JP6941373B2 - Amperometric electrochemical sensors, sensor systems and detection methods - Google Patents

Description

Cross-reference to related applications This application claims priority over US Patent Provisional Application No. 62 / 309,948, entitled "Amperometric Electrical Sensors, Sensor Systems and Detection Methods" filed March 17, 2016. This application is a partial continuation of US Patent Application No. 14 / 854,016 (currently pending) filed on September 14, 2015, and this application is the US Patent Provisional Application No. 14 filed on September 12, 2014. Claim priority over 62 / 049,977. Both of these are titled "Amperometric Electrochemical Sensors, Sensor Systems and Detection Methods". The above-mentioned provisional patent application and all disclosures of the patent application are incorporated herein by reference.

Federally Funded R & D Description Part of the invention was made with federal support under contract DE-SC-0009258 funded by the US Department of Energy. The United States Government reserves certain rights to the present invention.

The increase in global industrialization raises concerns about pollution caused by combustion processes. In particular, there are concerns about exhaust from vehicles or other distributed sources. New environmental regulations are _{gradually reducing NO X} (mixtures of various ratios of NO and NO ₂ ) emissions from diesel fuel vehicles, the most difficult of these environmental regulations being in 2010 EPA Tier 2. It is a diesel exhaust pipe standard.

To meet these emission regulations, engine manufacturers have developed new diesel aftertreatment technologies such as selective catalytic reduction (SCR) system and a lean NO _X trap (LNT). These techniques are often monitor performance, to meet board diagnostic requirements of the exhaust pipe exhaust, requiring multiple of the NO _X sensor. Generated during reduction technology (Point of generation abatement technologies) have also been developed for NO _X and other contaminants, but these solutions, when applied without a closed-loop control, can reduce fuel efficiency There is. In addition, some of the proposed solutions, if it is improperly controlled, itself obtained can cause contamination (e.g., selective catalytic reduction systems for NO _X is ammonia into the atmosphere May be released). Control of these reduction technologies is small and sensitive for _{NO X} , NH ₃ and other contaminants that can operate in oxygenated exhaust streams, such as exhaust streams resulting from lean burn engine operating conditions. A sensor is needed.

Several methods have been described for measuring the concentrations of NO _X and NH _3. These include electrochemical methods, potentiometric methods (including mixed potential methods), chemical resistance methods, current measurement methods, and impedance-based methods. A good discussion of these techniques is described in US Pat. Nos. 8,974,657 and 9,304,102, which are incorporated herein by reference. For example, in a mixed potential (potentiometric titration) sensor, an EMF signal (open circuit differential voltage) is generated in response to the presence of a target gas species due to the non-equilibrium potential between the detection electrode and the reference electrode. No bias is applied between the detection and reference electrodes of the hybrid potential sensor, and ions (or currents) do not flow through the cell. Amperometric sensors, on the other hand, measure the current resulting from a voltage bias applied between the electrodes of an electrochemical cell.

Amperometric device disclosed in the literature generally obtain a current detected under the applied voltage by the catalytic cracking of the NO _X as shown in the following formula:
Reducing the NO ₂ to ^{_{NO: NO 2 → 1/2}} O 2 + NO; reduction of and / or NO to _{N 2} and ^{_{O 2: NO → 1/2}} N 2 + 1/2 O 2.
Other amperometric sensors, such as those described in US Pat. No. 9,304,102, decompose the gas species (eg, NOx contacts) to detect the target gas (eg, NOx) concentration. Rather than relying on cracking), it is based on adsorbed gas species (eg, NOx) that increase the rate of oxygen reduction at the sensing electrode. With increase in the oxygen reduction current due to the presence of adsorbed NO _X, to detect the presence and / or concentration of the NO _X in the gas stream containing oxygen.

There may be a variety of devices and techniques for accurately detecting NO _X , NH ₃ and / or other target gas species, but anyone prior to us is described herein. It is believed that he did not produce or use the invention as described.

U.S. Pat. No. 8,974,657 U.S. Pat. No. 9,304,102

Although the present specification points out the present invention in detail and concludes with the scope of claims that are clearly claimed, the present invention, when read in conjunction with the accompanying drawings, is detailed in its particular embodiment. It is believed that the description will be better understood. Unless the context indicates otherwise, similar numbers in the drawings are used to identify similar elements in the drawings. Moreover, some drawings may be simplified by omitting certain elements to more clearly show the other elements. Such omissions do not necessarily indicate the presence or absence of any particular element of any of the exemplary embodiments, except as expressly stated in the corresponding detailed description.

It is a schematic cross-sectional view of an electrochemical sensor incorporated in a sensor system. The active electrode and the counter electrode are located on the same surface of the electrolyte layer (ie, the surface electrode), the active electrode has an overlying current collector layer, and the passive signal amplification layer is the opposite surface of the electrolyte layer. It is located above and is enclosed (ie, embedded) between the electrolyte layer and the support substrate.

FIG. 6 is an exploded view of an electrochemical sensor design (not including a bias source or current measuring device) similar to the design of FIG. The sensor includes a pair of substrate layers, a heater layer embedded between the substrate layers, a resistance temperature detector (“RTD”) layer on the bottom surface of the substrate, and multiple continuous layers on the top surface of the substrate: a signal amplification layer ( Current collection covering the "Pt-B"), electrolyte membrane layer (displayed as "GDC"), active electrode layer (displayed as "AE"), counter electrode layer (displayed as "CE"), and active electrode layer. Body layers (indicated as "CC") are included.

FIG. 6 is a schematic representation of a circuit for use with the sensors described herein. The current measurement function (ie, ammeter) is provided by measuring the voltage drop at the shunt resistor, which is proportional to the current flowing through the sensor.

4A and 4B show a common electrolyte layer and a common electrode layer located between two active electrode layers on the same surface of the electrolyte layer, together with a signal amplification layer encapsulated between the electrolyte layer and the support substrate. FIG. 5 is a schematic top and cross section of yet another alternative embodiment of a sensor system (also referred to as a surface electrode sensor) comprising two electrochemical cells having a counter electrode layer.

4C and 4D show two with a signal amplification layer encapsulated between the electrolyte layer and the support substrate, a separate electrolyte layer, and a common counter electrode layer located between the two active electrode layers. It is a schematic view of the top surface and the cross section of the alternative embodiment of the surface electrode sensor system including the electrochemical cell of.

4E and 4F are surface electrode sensor systems comprising a signal amplification layer encapsulated between an electrolyte layer and a support substrate, as well as two electrochemical cells having separate electrolyte layers and separate counter electrode layers. FIG. 5 is a schematic top and cross section of another alternative embodiment of.

4G and 4H show a surface electrode sensor having a signal amplification layer enclosed between the electrolyte layer and the support substrate, a separate electrolyte layer having electrodes interfitting with each other, and a common counter electrode layer. FIG. 5 is a schematic top and cross section of yet another embodiment of the system.

FIG. 6 is a schematic cross-sectional view of an embodiment of an electrochemical cell (or sense element) of various additional sensors, including SAL, further described herein.

Same as above.

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It is a figure which shows the result of the test of the sense element used in Examples 1 and 2, and these sensors in the simulated combustion exhaust.

Same as above.

_{Simulated combustion exhaust atmosphere (baseline gas, baseline containing 100 ppm NO, baseline containing 100 ppm NO 2} and 100 ppm NH ₃ included) for the sensor of Example 3 tested at 525 ° C. with an applied bias voltage of 200 mV. It is a bar graph which compares the current signals in (baseline).

The sensor of Example 4 tested at 525 ° C. with an applied bias voltage of 200 mV contains a simulated combustion exhaust atmosphere (baseline gas, baseline containing 100 ppm NO, baseline containing 100 ppm NO ₂ , and 100 ppm NH ₃₎ . It is a bar graph which compares the current signals in (baseline).

_{Simulated combustion exhaust atmosphere (baseline gas, baseline containing 100 ppm NO, baseline containing 100 ppm NO 2} and 100 ppm NH ₃ included) for the sensor of Example 5 tested at 525 ° C. with an applied bias voltage of 200 mV. It is a bar graph which compares the current signals in (baseline).

Simulated combustion exhaust atmosphere (baseline gas, baseline containing 100 ppm NO, baseline containing 100 ppm NO ₂ and 100 ppm NH ₃₎ for the sensor of Example 6 tested at 525 ° C. with an applied bias voltage of 200 mV. It is a bar graph which compares the current signals in (baseline).

It is a diagram schematically showing the sense element used in Example 11 operated in the forward bias, showing the result of the test in the simulated combustion exhaust of this sensor, NO at various oxygen levels in the gas sample. The response to NO ₂ and NH _{3 is shown.}

It is a diagram schematically showing the sense element used in Example 12 operated by the reverse bias, showing the result of the test with the simulated combustion exhaust of this sensor, NO at various oxygen levels in the gas sample. The response to NO ₂ and NH _{3 is shown.}

Graph the test results of the sense device of FIG. 19 showing the response to _{NO, NO 2} and NH ₃ at various oxygen levels in the gas sample and at various levels of reverse bias applied to the electrochemical cell. It is a figure shown by.

As further described herein, an alternative embodiment of a sense device, wherein one or both of the electrodes comprises a current collector layer located above the electrolyte layer and the catalyst layer is located above the current collector layer. It is a figure which shows the schematic sectional view.

Same as above.

Same as above.

Same as above.

Same as above.

The drawings are intended to illustrate it rather than limit the scope of the invention. Embodiments of the present invention may be carried out in a manner not necessarily shown in the drawings. Therefore, the drawings are intended to be merely an aid in the description of the present invention. Therefore, the present invention is not limited to the exact arrangement shown in the drawings.

The following detailed description will describe examples of embodiments of the invention solely for the purpose of allowing those skilled in the art to develop and use the invention. Therefore, the detailed description and illustration of these embodiments are essentially pure illustrations and do not limit the scope of the invention, or its protection, by any means. It is also naturally understood that the drawings are not on scale and in certain cases details not necessary for understanding the present invention are omitted.

The present disclosure provides amperometric electrochemical sensors, as well as sensor systems and gas species detection methods using such sensors, which are two (or more) surface electrodes located above the electrolyte. , As well as a passive conductive signal amplification layer. The signal amplification layer is placed in contact with the electrolyte and under the surface electrode without contact (eg, encapsulated in or just below the electrolyte layer). Although the signal amplification layer is separated from the surface electrode by the electrolyte layer, it amplifies the signal intensity and optionally affects the sensor selectivity for one or more gas species. In one study further discussed herein, adding a signal amplification layer between the bottom surface of the electrolyte layer and the sensor substrate increased the signal strength of the sensor by more than 10-fold, NO, NO _X and NH _3. The sensitivity of the sensor to the signal has also increased significantly. Although not bound by theory, it is believed that the signal amplification layer provides a lateral current path and effectively increases the active and counter electrode regions. This finding is surprising in that electricity is usually conducted between the electrodes only by oxygen ions through or along the surface of the electrolyte layer. In the presence of the signal amplification layer, it is considered that a part of oxygen ions normally conducted between the electrodes through the electrolyte layer is converted into electrons at the interface between the electrolyte layer and the signal amplification layer. These electrons are then carried through the signal amplification layer and then react with oxygen at the interface between the signal amplification layer and the electrolyte layer to form oxygen ions. The signal amplification layer provides a faster path for transport of charge carriers between the electrodes, even if this requires two additional electrochemical reactions. This finding can be applied to a variety of amperometric sensors with surface electrodes (including interconnected electrodes), which have much lower conductivity than the materials used for the signal amplification layer. It is particularly useful for other types of sensors in which an electrode layer is laminated on top of the material. Also, the signal amplification layer can have a larger spacing between the surface electrodes, which can simplify the manufacture of the sensor.

US Pat. No. 9,304,102, issued April 5, 2016, incorporated herein by reference (“Day et al.”), Describes an amperometric sensor, wherein at least one. Includes a conductive active electrode containing one molybdate or tungstate compound. _{The sensors described by Day et al. Are highly responsive to NO X} levels at desirable temperatures (eg, 500-600 ° C.) and, in some cases, to both _{NO X} and NH _3. Molybdate and tungstate active electrode compositions described Day et al., Oxygen ions (O2 ^-) when applied to conductive electrolyte, in the presence of the NO _X and NH _3, with respect to O ₂ reduction Shows high catalytic activity. The sensor of Day et al. Detects _{NO X} and NH ₃ by a catalytic effect in which the reduction of oxygen in the gas sample or gas stream _{is catalyzed by the presence of NO X} and NH _{3 on the surface of the active electrode.} The sensors of Day et al. Are also responsive to _{NO X} and NH ₃ in the presence of _{steam, carbon dioxide and sulfur oxides (SO X} ), which are additional components of the diesel exhaust stream.

In addition, the molybdates used in one or more active electrodes, as described in US Patent Application Publication No. 2016/077044, published March 17, 2016 and incorporated herein by reference. The sensor is tuned with the selection of and / or tungstate compounds and / or the selection of one or more current collector layers applied over one or more active electrodes, eg, in a gas sample. The concentration of NO _X and NH _{3 (ie, the amount of NO X and} the amount of NH ₃ rather than the total amount of _{NO X} and NH ₃ ) can be determined using it.

In some examples, it is desirable to make a sensor in which the electrodes are located on the same surface of the electrolyte membrane rather than on the opposite surface of the electrolyte. In such a "surface electrode" arrangement, the electrodes are located on the same surface of the sensor with respect to one or more electrolyte layers. The electrodes (eg, counter electrodes) are not embedded beneath the electrolyte. Generally, such surface electrodes are located above the top surface of the electrolyte layer so that both are exposed to the sample or stream of the gaseous analyte being analyzed.

In the present disclosure, a passive conductive signal amplification layer (hereinafter referred to as “SAL”), which is partially located below the surface electrode of an amperometric sensor but is not in contact with the surface electrode, unexpectedly has a signal strength and, in some cases, 1 Based on the surprising discovery of enhancing sensor selectivity for the above gas types. As an example, the sensor electrode can be located above the top surface of the electrolyte and the SAL can be located inside or below the electrolyte. In an alternative embodiment of the present disclosure, one or both of the electrodes of the amperometric sensor comprises a current collector layer located above the electrolyte layer and the catalyst layer is located above the current collector layer.

Embodiments of amperometric electrochemical sensors, sensor systems and detection methods described herein are adapted to detect a target gas species in a sample or stream of gaseous analyte using surface electrode arrangements. ing. Thus, instead of the electrode being located on the opposite surface of the sensor with respect to one or more electrolyte layers, the electrode is located on the same surface of the sensor with respect to one or more electrolyte layers. In some embodiments, a passive conductive signal amplification layer, or SAL (further described herein), is also provided away from the sensor. The SAL is in conductive contact with the electrolyte layer and can be located, for example, on the surface of the electrolyte layer opposite to the electrode surface (eg, between the electrolyte layer and the sensor substrate). The SAL is either completely encapsulated between the electrolyte layer and the substrate (eg, see FIG. 1) or only partially (eg, so that the outer edge of the SAL is not covered by the electrolyte or substrate). Can be done. As yet another alternative, the SAL is completely encapsulated in the electrolyte layer, away from both the top and bottom surfaces of the electrolyte layer so that the substrate on which the electrolyte layer is located does not come into contact with the SAL. Can be done. In some examples, the advantage provided by SAL is greater when the distance between the SAL and the electrode is minimized, not small enough to cause a short circuit between the electrode and the SAL.

The signal amplification layer is passive in that it has no direct electrical connection or contact with a sensor, bias source or current measuring device. In fact, in some embodiments, the SAL is only present in direct conductive contact with the electrolyte layer and substrate (generally non-conductive). All conductivity between the electrodes and the SAL is through the electrolyte layer of the sensor and no other current or electrical bias is applied to the SAL. Despite its passive nature, the inventors have found that the signal amplification layer surprisingly significantly enhances the signal strength and, in some cases, the sensor sensitivity to a particular gas species.

Although the present disclosure describes an amperometric sensor incorporating SAL therein, the use of passive conductive signal amplification layers includes a variety of other amperometric sensors and sensor systems with surface electrodes, as well as hybrids. It can be applied to potential sensors and sensor systems. These include, for example, U.S. Pat. No. 8,974,657 under the title "Amperometric electrical cells and sensors," U.S. Patent Application Publication No. 2009/0218220, published September 3, 2009, and Day et al. 9, 304, 102)) includes the sensors and sensor systems described. Each of the aforementioned references is incorporated herein by reference.

The SAL can be made of any of a variety of conductive materials suitable for the manufacture of sensors. Suitable materials include, for example, Pt, Pd, Au, Ag, alloys of the aforementioned metals (eg alloys of Pt and Pd, Au and / or Au), and other conductive metals conductive ceramics or cermets. Be done. Platinum is especially useful.

In some embodiments, the amperometric electrochemical sensors, sensor systems and detection methods described herein are adapted to detect one or more target gas species in a sample or stream of gaseous analyte. doing. In an embodiment for detecting one gas species (including detecting a combination of two or more related gas species such as the presence and / or concentration of _{NO X), the sensor comprises at least one electrochemical cell.} include. In embodiments for detecting two or more gas species, especially for use in determining the concentration of individual gas species, the sensor typically includes at least two electrochemical cells. As an example, in a sensor with two electrochemical cells, one of the cells responds additionally to the gas species of interest and the other cell responds selectively to at least one gas species. Can be configured in. Alternatively, as further described herein, a sensor with one electrochemical cell under two or more separate conditions (eg, forward bias and reverse bias) to obtain two or more response characteristics. Can be operated. In some embodiments, the two (or more) electrochemical cells of the sensor have a completely separate structure, while in other embodiments, the two (or more) electrochemical cells of the sensor are one or more. It shares components such as a common electrolyte layer, SAL, substrate, counter electrode or active electrode.

In general, each electrochemical cell of the amperometric surface electrode sensor according to the embodiments of the present disclosure contains a conductive active electrode, a conductive counter electrode (sometimes referred to as a second active electrode), an electrolyte layer, and a SAL. included. The active and counter electrodes are spaced apart from each other on the same surface of the electrolyte layer so that oxygen ions are conducted through the surface and interior of the electrolyte layer. In some examples, the active and counter electrodes are arranged side by side on the electrolyte layer. Alternatively, the active electrode and the counter electrode can be formed in a mutually fitted arrangement (eg, as shown in FIG. 4G). In some embodiments, a current collector layer that is in electrical contact with (eg, in contact with) the active electrode is also included, and similarly, in some examples, the counter electrode (or second). A current collector layer that is in electrical contact with the active electrode) is also included. As discussed below, one or more current collector layers can be applied to the top of the electrodes. Alternatively, one or more current collector layers can be located between the electrode and the electrolyte layer, also as discussed below.

As a mere example, the amperometric sensors, systems and methods described herein, at least in part, use electrocatalysis, such as _{NO X} and / or NH _{3 in an oxygen-containing environment of burned hydrocarbon fuel exhaust.} It can be used to detect the target gas species of. As a more specific example, _{amperometric sensors, sensor systems and detection methods with significantly enhanced sensitivity to both NO X} and NH ₃ include combustion exhaust streams (eg, exhaust from the vehicle's diesel engine). Can operate in gas). In some examples, the sensor may be configured to allow the differentiation and quantification of the concentration of the NO _X and NH _3.

Embodiment of an electrochemical sensor, sensor systems and methods described herein, the target gas (e.g., NO _X) in order to detect the concentration, the decomposition of the gas species (e.g., catalytic cracking of NO _X) Rather than relying on it, under the influence of a bias applied between the two electrodes, the adsorbed gas species (eg NO _X ) reacts in a predictable manner when changing the rate of oxygen reduction at the active electrode of the sensor. It is configured as a current measuring device / method. Due to the presence of adsorbed NO _X, the change in oxygen reduction current is used to detect the presence and / or concentration of the NO _X in the gas sample or gas stream containing oxygen. This mechanism is very fast and produces a larger current than is possible from the reduction of _{NO X alone.} Furthermore, the catalyst approach that extends to NH ₃ was demonstrated.

In some embodiments, each electrochemical cell of the amperometric ceramic electrochemical sensor is an electrolyte layer comprising a continuous network of materials that conduct ions at an operating temperature of about 400-700 ° C; about 400-700 ° C. Includes a counter electrode layer that is conductive at the operating temperature of; and an active electrode layer that is conductive at an operating temperature of about 400-700 ° C. The active electrode layer can operate to show changes in charge transfer in the presence of one or more target gas species, combining molybdate or tungstate compounds, generally with other materials such as electrolytes and metals. Including. The electrode layers are located on the same surface of the electrolyte layer, but are not in physical contact with each other (ie, they are separated). Embodiments of the electrochemical cell can operate to exhibit the conductivity of oxygen ions at an operating temperature of about 400-700 ° C. When a bias is applied between the electrodes, one or more electrochemical cells generate an electrical signal as a function of the concentration of the target gas in the oxygen-containing gas stream in the absence of an oxygen pumping current.

In some embodiments, the one or more electrochemical cells further include a current collector layer that is conductive at an operating temperature of about 400-700 ° C., the current collector layer being one or more active. It is in electrical contact with the electrode layer (eg, located on its surface). The current collector layer is more conductive than the active electrode layer, especially at an operating temperature of about 400 to 700 ° C. The purpose of the current collector layer is to increase the conductivity of the active electrode. However, in some embodiments, the current collector layer also manipulates the catalytic and electrochemical reactions that occur at the active electrode, thereby causing one or more gas species of interest (eg, NO, NO ₂ or NH _3). ) Can also be selected to reduce or enhance sensitivity to). In these embodiments, the combination of the active electrode and the current collector layer can be regarded as a two-layer active electrode.

The sensors described herein are made to be _{capable of detecting, for example, NO, NO 2} and NH ₃ (including detection at levels as low as 3 ppm) and / or exhibiting fast response times of 50 ms. , Good system control or even engine feedback control can be enabled. When configured to operate in the temperature range of 400-700 ° C., _{the response of NO X} and NH ₃ in some embodiments is greater than the sensitivity to variable background exhaust.

Sensor described herein, sensor systems and detection methods will have applicability to the detection of the NO _X in a diesel exhaust system comprising an exhaust system found in heavy truck and stationary generators, gas particularly containing oxygen It is also useful in a wide range of other applications where a rapid response to low levels of NO _X and / or NH _{3 is desired in the stream or sample.} Examples include diesel generators, large static generators, turbine engines, natural gas combustion boilers, and more specific electrical appliances (eg, natural gas powered furnaces, water heaters, stoves, ovens, etc.). Even included. Sensors, sensor systems and detection methods are at low levels in the presence of other gases of fixed or variable concentration, such as O ₂ , CO ₂ , SOx (SO and / or SO ₂ ), H ₂ O, and NH _3. It is especially useful in detecting NO _X.

Various electrochemical sensors, sensor systems and detection methods are described herein by reference to specific electrolytes, electrodes, current collectors and SAL compositions. However, the electrochemical sensors, sensor systems and detection methods described herein will yield beneficial results in a wide range of materials. It will be understood that the thickness shown in the drawings is so exaggerated that it is not on scale. Moreover, unless the context otherwise indicates, the terms "detect", "detect", and "detect" not only detect the presence of a target species, but also detect or measure the amount or concentration of the target species. It is also intended to include what to do.

In some embodiments having two or more electrochemical cells, the first electrochemical is such that the target gas species changes the amount of oxygen reduced in the first electrochemical cell in proportion to its concentration. The active electrode and / or collector layer of the cell is exposed to _{more than one target gas species (eg, NO X} and NH _3). As a result, the total concentration of the target gas species in the gas sample or gas stream can be correlated with the oxygen ion current through the first electrochemical cell at any given applied voltage bias and sensor temperature. The response of the first electrochemical cell of the sensor in this example is that the current measured at a given voltage bias and temperature correlates with the combined total concentration of _{the target gas species (eg NO X} and NH _3). It is "additional" in that it can be done. The active electrode and / or current collector layer of the second electrochemical cell is also exposed to more than one target species. _{However, the second electrochemical cell changes the amount of oxygen reduced in the second cell by the first gas species (eg, NO X} ) of the target gas species to the extent that it can be measured, and the second electrochemical cell of the target gas species. The configuration and / or operation is such that the effect (if present) on the amount of oxygen reduced in the second cell of the two gas species (eg, NH _{3) is significantly smaller.} Therefore, the measured current through the second electrochemical cell _{can be correlated with the concentration of the first target gas species (eg, NO X} ), but the change in the concentration of the second target gas species is the second electricity. The second electrochemical cell is "selective" with respect to the first gas species of the target gas species in that it has no recognizable effect (if any) on the measured current through the chemical cell. In this way, the concentration of the target gas species can be determined. Of course, any number of electrochemical cells can be provided as part of one sensor, for example, to detect two or more gas species.

FIG. 1 shows an exemplary amperometric sensor system (10) that includes a circuit that includes one electrochemical cell (20) (ie, a sensor) and a bias source (40) and a current measuring device (50). Some embodiments of the sensor system described herein include at least two electrochemical cells. Therefore, it will be understood that the sensor system of FIG. 1 depicts only half of such a sensor system. For example, FIG. 4F typically represents a sensor containing two electrochemical cells. Each cell is similar in structure to the individual cell (20) of the sensor shown in FIG. 1 and is laminated on a common substrate (428).

The electrochemical cell (20) includes an active electrode (22), a counter electrode (26), and an oxygen ion conductive electrolyte layer (24) on which the electrodes (22, 26) are located. As an example, the conductive active electrode (22) comprises at least one molybdate or tungstate compound. As shown, the passive conductive signal amplification layer (ie SAL) (27) is located beneath the electrolyte membrane (24) and the non-conductive substrate (28) supports the SAL (27). .. In this embodiment, the SAL (27) is completely encapsulated by the electrolyte layer (24) and the substrate (28). The bias source (40) is configured to apply a bias voltage between the two electrodes (22, 26) so that the current measuring device (50) measures the resulting current through the sensor (20). It is configured in. The bias source (40) can consist of either a variety of power supplies suitable for applying a bias between the active electrode (22) and the counter electrode (26), or any other device. The current measuring device (50) of FIG. 1 can consist of any of a variety of structures and devices known to those skilled in the art (or will be developed in the future), such as an ammeter. As is well known to those of skill in the art, ammeters can be provided by a combination of a shunt resistor and a voltmeter (as shown in FIG. 3).

FIG. 2 is an exploded view of an electrochemical sensor similar to FIG. 1, including some additional components. The sensor of FIG. 2 is made by sequentially stacking the following layers on an insulating substrate (ie, the top Al ₂ O ₃ layer in FIG. 2): signal amplification layer (“Pt−B”). One common electrolyte layer laminated on top of the SAL (“GDC”); active electrode layer laminated on a portion of the top surface of the electrolyte layer (“AE”); A counter electrode layer (CE) laminated on different portions of the top surface; and a first current collector layer (“CC”) laminated on the top surface of the active electrode layer. If desired, the second current collector layer can be laminated on the upper surface of the counter electrode layer. In the embodiment shown in FIG. 2, the sensor includes a platinum resistance heater (“Pt—H”) embedded between the substrate layers and a platinum resistance temperature detector laminated on the bottom surface of the second substrate layer (“Pt—H”). _{A second insulating Al 2} O ₃ substrate layer is included along with a "Pt-RTD") for monitoring the sensor temperature. Electrode and current collector leads ("Pt-L") are also shown, and Pt-H and Pt-RTD leads are also depicted.

Returning to FIG. 1, the current collector (36) is exposed to a gas containing oxygen, a voltage bias is applied between the electrodes (22, 26), and the electrochemical cell (20) is heated to a suitable operating temperature. Then, the oxygen molecule is reduced at the active electrode (22). The presence of one or more target gas species (eg, NO _X and / or NH ₃ ) affects the amount of oxygen reduced at the active electrode (22) (proportional to the target species concentration). The resulting oxygen ions are conducted across the electrolyte membrane (24) to the counter electrode (26), where the oxygen ions oxidize to reshape O ₂ and produce a measurable current. SAL (27) provides a lateral current path for electron transport under the electrolyte. As explained above, SAL (27) is believed to enhance the transport of oxygen ions from one electrode to the other. Under forward bias, SAL (27) provides an interface with the electrolyte layer, where oxygen ions from the active electrode (22) are converted to electrons. These electrons are then carried through the SAL (27) to the region below the counter electrode (26) and then react with oxygen at the SAL / electrolyte interface to form oxygen ions. These oxygen ions are then transported through the electrolyte layer to the counter electrode (26). Therefore, SAL (27) provides an additional (and faster) route for transporting oxygen ions from one electrode to the other through the electrolyte. However, it should be understood that it is the electrons, not the oxygen ions, that are transported through the SAL.

In some sensor embodiments (including those used in the examples further described herein), the electrolyte layer is porous. In other embodiments, the electrolyte layer is dense (not penetrating). In the embodiment shown in FIG. 1, the electrolyte membrane (24) is located at both ends of the SAL (27) so that the SAL (27) is completely encapsulated between the electrolyte membrane (24) and the substrate (28). Spread to. In other embodiments, such as FIGS. 7 and 8, the SAL is not completely encapsulated. Therefore, it is understood that the fully encapsulated SAL (27) in the embodiment of FIG. 1 can be replaced with the SAL arrangement shown in FIGS. 7 and 8 (ie, the electrolyte does not spread all around the SAL). Will be done. As used herein, "completely encapsulated" means that the SAL is surrounded by an electrolyte layer and a substrate, or is surrounded only by the electrolyte layer (ie, the SAL is not in contact with the substrate (ie). Not in contract with), rather a part of the electrolyte layer is located between the SAL and the substrate).

Embodiments of the sensor described herein include a substrate on which one or more electrochemical cells are made or otherwise supported, thereby to the sensor. Provides mechanical support for. Substrates are usually non-conductive (ie insulated). The substrate may include any suitable insulating material such as an insulating ceramic material (eg, aluminum oxide) or a metal or cermet material coated with the insulating material. In one embodiment, the sensor includes a zirconia substrate, more specifically an yttria-stabilized zirconia (YSZ) substrate.

Alternatively, the substrate may comprise a semiconductor material such as silicon or silicon carbide, and components of one or more electrochemical cells are made on the surface of the substrate using semiconductor manufacturing techniques.

In embodiments where the active electrode comprises a molybdate and / or tungstate compound, any of a variety of molybdate and / or tungstate compounds can be used. Suitable compounds, wherein _{A X (Mo (1-Z} ) W Z) Y O (X + 3Y) ( wherein, X and Y are selected from each independently represents an integer of 1 to 5, 0 ≦ Z ≦ 1 A is one or more ions that form a binary compound with Mo and / or W). As a more specific example, A is one or more of Mg, Zn, Ni, Co, Fe, Mn, Cu, Ca, Sr, Ba, and Pb. In some embodiments, both X and Y are 1 and Z is 0. Specific examples of such molybdate compounds include MgMoO ₄ , ZnMoO ₄ , NiMoO ₄ , CoMoO ₄ , FeMoO ₄ , MnMoO ₄ , CuMoO ₄ , CaMoO ₄ , SrMoO ₄ , BaMoO ₄ , and PbMoO _4. .. In other embodiments, both X and Y are 1, and Z is 1. Specific examples of such tungstate compounds include MgWO ₄ , ZnWO ₄ , NiWO ₄ , CoWO ₄ , FeWO ₄ , MnWO ₄ , CuWO ₄ , CaWO ₄ , SrWO ₄ , BaWO ₄ , and PbWO _4. ..

Active electrodes containing at least one molybdate or tungstate compound may have a variety of specific compositions, including, for example:
(A) for example, more than 30%, more than 50%, 80% or 90% molybdate or tungstate compound molybdate compounds including an active electrode containing the (by volume) _(A X Mo _Y O _{(X + 3Y))} or tungstate compound _{(A X W Y O (X} + 3Y));
(B) Formula _{A X (Mo (1-Z} ) W Z) Y O (X + 3Y), ( wherein, X and Y are each independently selected from an integer of 1 to 5, be 0 <Z <1 , A is one or more of Mg, Zn, Ni, Co, Fe, Mn, Cu, Ca, Sr, Ba, and Pb);
(C) A composite mixture of two or more compounds selected from the group consisting of molybdate and tungstate compounds, such as a composite mixture of at least one molybdate compound and at least one tungstate compound;
(D) A composite mixture of one or more ceramic electrolyte materials and one or more (a) to (c);
(E) A composite material made of a ceramic phase containing one or more of (a) to (d) and a metal phase (eg, silver, gold, platinum, palladium, rhodium, ruthenium, iridium or an alloy or mixture thereof). Or a mixture of two or more of (f) (a)-(e).
In some of the above embodiments, one or more additives or other materials may be added to the active electrode composition during production, but in other embodiments such additives are not included.

The molybdate and tungstate compounds and the solid solution of the molybdate and tungstate compounds may be doped with one or more metals. On top of that, or instead, one or more oxides such as manganese oxide, iron oxide, cobalt oxide, vanadium oxide, chromium oxide, tin oxide, niobium oxide, tantalum oxide, ruthenium oxide, indium oxide, titanium oxide, and zirconium oxide. Etc. may be added. When used, these oxide additives may be present in an amount between about 0.1-10% by volume in the active electrode layer or between about 1-3% by volume in the active electrode layer.

As mentioned above, in some embodiments, the one or more active electrodes are (a) a ceramic phase containing molybdate and / or molybdate (eg, molybdate, tungstate, molybdate). A solid solution or composite mixture of and molybdate, or a composite mixture of one or more of the above and an electrolyte); and (b) metal phases (Ag, Au, Pt, Pd, Rh, Ru, Ir, or alloys or mixtures thereof). : Includes polyphase composite material. The tungstate / molybdate ceramic phase of such composites may itself contain two or more phases, such as one or more molybdates and / or composite mixtures of tyrosine compounds and electrolytes. Should be noted.

For the polyphase ceramic / metal composites described above, the amount of metal phase can range from about 0.1% to 10% by weight or from about 30 to 70% by volume. For polyphase ceramic / metal composites with low levels of metal phases (eg, about 0.1% to 10%, or about 1% to 5 % by weight), Pt, Pd, Rh, Ru, or Ir (or them). (Alloys of mixtures of) are particularly useful. Higher levels of metal phases (eg, about 30% to 70%, or about 40% to 60 % by volume ) include Ag, Au, Pt, Pd, Rh, Ru, or Ir (or alloys thereof) or The mixture) may be used to improve conductivity (although sensitivity may be sacrificed somewhat).

As mentioned above, in some embodiments, the one or more active electrodes are (a) one or more ceramic electrolyte materials (eg, gadolinium-doped ceria, "GDC", or samarium-doped ceria, ". SDC "); (b) one or more molybdate and / or tungstate compounds; and optionally (c) metal phases (eg, silver, gold, platinum, palladium, rhodium, ruthenium, iridium, or them. Contains a composite mixture of (alloys or mixtures of). In these embodiments, the one or more ceramic electrolyte materials in the active electrode (22) are one of the electrolytes described below for the electrolyte membrane (24), or another that conducts electricity by conduction of oxygen ions. It may be a ceramic electrolyte material (ie, ionic conductivity rather than electron conductivity). As an example, as a ceramic electrolyte suitable for use in active electrodes,
(A) Cerium oxide doped with one or more of Ca, Sr, Sc, Y, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or La;
Examples thereof include (b) zirconium oxide doped with one or more of Ca, Mg, Sc, Y, or Ce; and (c) lanthanum oxide gallium oxide doped with one or more of Sr, Mg, Zn, Co, or Fe.
In a more specific embodiment, the ceramic electrolytes used in the active electrode are Ca, Sr, Sc, Y, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Alternatively, it contains cerium oxide doped with 1 or more of La. For example, GDC or SDC may be used as the metal phase in combination with Pt.

The relative amounts of the ceramic electrolyte and one or more molybdate / tungstate compounds in the composite mixture described in the previous paragraph are, among other things, the nature of the application (eg, gas flow / sample and ambient environment of the analyte), sensors. And / or may vary depending on the configuration of the sensor system, desired sensitivity, identity of one or more target gases, and so on. In some embodiments, the volume ratio of one or more ceramic electrolytes to one or more molybdate / tungstate compounds in the active electrode is between about 1: 9 and 9: 1. In other embodiments, the ratio is between about 2.5: 7.5-7.5: 2.5, or between about 4: 6 and 6: 4. In yet other embodiments, this ratio is about 1: 1. It should be pointed out that the aforementioned volume ratio is based on the ratio of the total volume of the ceramic electrolyte to the total volume of the molybdate and tungstate compounds in the active electrode layer in question. If the composite mixture described in the preceding paragraph contains a metal phase, the nature and amount of the metal phase may be any of the various metals and amounts previously described.

In yet further embodiments using SAL, the active electrode material may be any of the materials described in the applicant's previous sensor patents and published patent applications already incorporated herein by reference. The active electrode material can be electronically conductive or ionic conductive. In some examples, the active electrode material may be so conductive that the current collector layer is not required to achieve optimum signal strength, and the current collector layer may provide optimum signal strength. The conductivity may be minimal or moderate enough to be necessary. (Signal strength is defined as the current that occurs when a bias voltage is applied).

As a further example, suitable active electrode materials used in combination with SAL to increase signal intensity as an alternative to the above compositions comprising molybdenate or tungstate compounds include Ca, Sr, Ba, Fe, Lantanide manganate perovskite material doped with Co, Ni, Cu, Zn, Mg or a mixture thereof; Lantanide ferrite perovskite material doped with Ca, Sr, Ba, Mn, Co, Ni, Cu, Zn, Mg or a mixture thereof; Lantanide bright cobalt ore perovskite material doped with Ca, Sr, Ba, Mn, Fe, Ni, Cu, Zn, Mg or a mixture thereof; Ca, Sr, Ba, Mn, Fe, Co, Cu, Zn, Mg or a mixture thereof. Lantanide Nikrate Perovskite Material Doped with; Lantanide Copper Oxide Perobskite Material Doped with Ca, Sr, Ba, Mn, Fe, Co, Ni, or a mixture thereof; Composite Material Containing a Mixture of Ceramic and Metal Phase (Cermet) (Here, the ceramic phase is a ceramic electrolyte material, for example, a zirconia-based electrolyte material, a ceria-based electrolyte material, a bismuth oxide-based electrolyte material or a lanthanum gallium oxide-based electrolyte material, or a mixture thereof, and the metal phase is Ag, Pt, Pd, Rh, Ru, Ir or alloys or mixtures thereof); composite materials containing a mixture of ceramic and metallic phases, where the ceramic phase is an insulator such as aluminum oxide, magnesium oxide, or another insulating ceramic material. Yes, the metal phase comprises Ag, Pt, Pd, Rh, Ru, Ir or an alloy or mixture thereof); a metal electrode material containing Ag, Pt, Pd, Rh, Ru, Ir or an alloy or mixture thereof; or described above. Examples thereof include a mixture containing any two or more of the detection electrode materials.

In some embodiments, the current collector layer is provided for one or more active electrode layers of one or more electrochemical cells and, optionally, for one or more counter electrode layers. .. Since the current collector layer has higher conductivity than the active electrode layer, the electric conductivity of the active electrode is increased so that the signal strength is high. Moreover, in some embodiments, the current collector layer occurs at the underlying electrodes to provide reduced or enhanced sensitivity to one or more gas species of interest (eg, NO, NO ₂ or NH _3). It also manipulates catalysts and electrochemical reactions.

For example, the electrochemical cell (20) in FIG. 1 includes a current collector layer (36). The active electrode layer (22) is adjacent to the electrolyte membrane (24), but the current collector layer (36) is located above the active electrode layer (22). The conductivity of the current collector layer (36) is higher than that of the active electrode layer (22). In this particular embodiment, the current collector layer is configured as an overall covering in that it covers at least about 90% of the top surface of the active electrode layer (22). Alternative embodiments, in particular those in which the current collector is not configured to manipulate the catalyst and electrochemical reaction to reduce or enhance sensitivity to the target gas species, are further described in US Patent Application Publication No. 2016/077044. As described, the current collector can be configured to cover about 10-25% of the surface of the active electrode.

With respect to the composition of the current collector layer, if the current collector is used to simply increase the conductivity of the active electrode rather than manipulating the catalyst and / or electrochemical reaction at the underlying electrode, the current collector layer , Such as platinum, palladium, gold, silver, or any other precious metal, may include alloys of two or more precious metals, alloys of one or more precious metals and one or more base metals, or cermets of precious metals and ceramic electrolyte materials. ..

Alternatively, the current collector layer may be a metal (eg, platinum or gold) and ceramic phase, such as GDC, SDC, zirconium-doped ceria (“ZDC”), yttria-stabilized zirconia (“YSZ”), scandium-stabilized zirconia. Cermets may include (“ScSZ”), or one of the other ceramic electrolytes referred to as suitable for use in active electrodes. The metal content of such a cermet current collector layer must be sufficient to make the conductivity of the current collector layer higher than that of the underlying electrode layer. As further discussed herein, such cermet current collectors are used to manipulate the catalyst and / or electrochemical reaction of one or more electrochemical cells of a sensor (eg, for one or more purposes). Can be used to reduce or enhance the sensitivity of the gas species.

For example, in some embodiments, one or more cermet current collectors contain platinum and a ceramic electrolyte (eg, ScSz) to provide additional behavior with respect to _{NO X} and NH _{3, whereas gold and ceramic.} One or more cermet current collectors containing an electrolyte (eg, GDC) will result in selective behavior with respect _{to NO X in} the presence of _{NH 3.} In the example of a cermet current collector, especially a cermet current collector used to manipulate the response of an electrochemical cell, the current collector is about 40-80% by volume, or about 50-70% by volume metal phase ( For example, it may contain Pt or Au) and the rest may be a ceramic electrolyte phase (eg, GDC or ScSz).

The counter electrode of the electrochemical cell of the sensor described herein can include any of a variety of materials, depending on the configuration of the electrochemical cell in part or more. For example, the counter electrode may be any of the compositions described above for the current collector, such as a metal material such as platinum or gold, or a metal (eg platinum or gold) and a ceramic phase (GDC, SDC, ZDC, YSZ or Conductive cermets containing ScSZ) can be included. The counter electrode may be any of the materials identified above for the active electrode. Other materials suitable for the counter electrode of the sensor described herein include:
(A) Metals containing Ag, Au, Pt, Pd, Rh, Ru, or Ir, or any of the alloys, mixtures or cermets described above (eg, one or more of these metals, especially Pt, and YSZ, ScSZ, Cermet containing GDC or SDC); and (b) Various other conductive materials suitable for the manufacture of sensors, in particular materials that catalyze the reoxidation of oxygen ions to molecular oxygen (eg, conductive perovskite, eg, (eg,). La, Sr) MnO ₃ , (La, Sr) CoO ₃ , (La, Sr) (Co, Fe) O ₃ , La (Ni, Fe) O ₃ , La (Ni, Co) O ₃ , and related perovskite, etc. , And materials with a brown miralite type structure).

In yet further embodiments using SAL, the counter electrode material may be any of the materials described in the applicant's previous sensor patents and published patent applications already incorporated herein by reference. For example, as described in US Pat. No. 8,974,657, counterelectrode materials suitable for use in combination with SAL to enhance signal strength include Ca, Sr, Ba, Fe, Co. Lantanide manganate perovskite material doped with Ni, Cu, Zn, Mg or a mixture thereof; Lantanide ferrite perovskite material doped with Ca, Sr, Ba, Mn, Co, Ni, Cu, Zn, Mg or a mixture thereof; Ca Lantanide bright cobalt ore perovskite material doped with Sr, Ba, Mn, Fe, Ni, Cu, Zn, Mg or a mixture thereof; Ca, Sr, Ba, Mn, Fe, Co, Cu, Zn, Mg or a mixture thereof. Dope lanthanide nickate perovskite material; lanthanide copper oxide perovskite material doped with Ca, Sr, Ba, Mn, Fe, Co, Ni, or a mixture thereof; or Ni, Fe, Cu, Ag, Au, Pd, Pt , Rh, or a metal material containing Ir, or an alloy, mixture or cermet thereof.

It will be appreciated that in most examples, the active and counter electrodes of the individual electrochemical cells have different compositions, and / or their respective current collector layers have different compositions. For example, in some embodiments, the active electrode layer and the counter electrode layer are the same, but their respective current collector layers have different compositions. In some examples, each "electrode" of an electrochemical cell is such that the collector layer of an individual electrochemical cell (all) can be selected to manipulate the catalytic and / or electrochemical reaction of the cell. Can be thought of as a combination of an active (or "functional") electrode layer and a current collector layer (if present). For example, one electrochemical cell of a sensor can include first and second two-layer electrodes, each having an active (or "functional") layer and a current collecting layer, of the first electrode layer. The composition of at least one is different from the corresponding layer of the second electrode. Therefore, the first and second electrodes differ in their catalytic and / or electron-catalyzed response to the gas species to be detected.

In an alternative embodiment, the first electrode is a combination of an active electrode layer and an upper current collector layer, only an active electrode layer, or only a current collector layer (ie, a traditional counter electrode). The second electrode is a different combination of active electrode layer and / or current collector layer.

Suitable materials for the ionic conduction electrolyte membrane of the electrochemical cells used in the sensors described herein include dope ceria electrolytes and dope zirconia electrolytes. More specific examples include gadolinium-doped ceria (Ce _1-X Gd _X O _{2-X / 2} , where X is in the range of about 0.05-0.40), samarium-doped. Cerium (Ce _1-X Sm _X O _{2-X / 2} , in the formula, X ranges from about 0.05 to 0.40), yttrium-doped ceria (YDC), and other lanthanide-doped elements. Examples include cerium oxide and cerium oxide doped with two or more lanthanide or rare earth elements. Yet other suitable electrolyte materials include fully or partially doped zirconium oxide (including, but not limited to, yttria-stabilized zirconia (YSZ) and scandium-doped zirconia (ScSZ)); predominantly of oxygen ions. Other ceramic materials that conduct electricity by transport; mixed conductive ceramic electrolyte materials; as well as the two or more mixtures mentioned above. Moreover, an interface layer of GDC, SDC or another suitable electrolyte material may be provided between the electrolyte membrane and one or both of the active electrode and the counter electrode. Particularly suitable electrolyte materials include GDC, SDC, YSZ and ScSZ.

In yet another alternative form, the ceramic electrolyte material can be β-alumina, sodium zirconium phosphate, lithium silicate, lithium aluminum silicate, or any alkali ion conductive electrolyte material.

As already mentioned, some embodiments of the sensors and sensor systems described herein typically include at least two electrochemical cells, wherein the first cell is at least two of the objects of interest. The second cell is configured (or operates) to provide an additional response with respect to the target gas species (eg, NO _X and and NH ₃ ), and the second cell is the target gas species rather than the second gas species of the target gas species. It is configured (or works) to provide a selective response with respect to the first gas species in the. _{For example, with respect to the detection of NO X} and NH ₃ using the active electrode material described above, the sensor is sensitive to two electrochemical cells with different active electrodes, i.e. both _{NO X} and NH _3. It can be assembled with cells and cells that are sensitive only to _{NO X} (with little or no sensitivity to _{NH 3).} The total concentration of NO _X and NH ₃ can be quantified by measuring the current when biasing the first electrochemical cell, and the NO _X concentration biases the second electrochemical cell. It can be quantified by measuring the current at the time of application and the NH ₃ concentration can be calculated by subtraction (total concentration of _{NO X} and NH _{3 −NO X} concentration). Therefore, _{both NO X} and NH ₃ can be measured with one sensor. These two electrochemical cells can be physically integrated into one structure (eg, with a common electrolyte layer, a common SAL, a common substrate, and optionally a common counter electrode). , Or two physically separated electrochemical cells may be made.

As yet another alternative, the sensor is made of different current collector materials and so that one cell is sensitive to both _{NO X} and NH _{3 and the other cell is sensitive only to NO X.} It can be assembled in two electrochemical cells with the same or different active electrode materials. The total concentration of NO _X and NH ₃ can be quantified by measuring the current when biasing the first electrochemical cell, and the NO _X concentration biases the second electrochemical cell. can be quantified by measuring the current in applying, NH ₃ concentration can be calculated by subtraction. Therefore, _{both NO X} and NH ₃ can be measured with one sensor. As already mentioned, these two electrochemical cells can be physically integrated into one structure, or two physically separated electrochemical cells may be used.

Yet another alternative is a sensor assembled with two electrochemical cells having active electrodes of the same or similar composition, including or not containing related current collectors of the same or similar composition. Can operate with a forward bias applied to one electrochemical cell (ie, from the active electrode to the counter electrode) _{to detect and quantify the sum of NO X} and NH ₃ , and further to the second electrochemical cell. _{Either NO X} or NH ₃ can be detected and quantified by operating with the applied reverse bias (ie, counter electrode to active electrode) (the concentration of the other is calculated by subtraction). Therefore, _{both NO X} and NH ₃ can be measured with one sensor. As already mentioned, these two electrochemical cells can be physically integrated into one structure, or two physically separated electrochemical cells may be used. Similarly, in some embodiments, one electrochemical cell operates with forward and reverse biases (eg, alternating the two), with different response characteristics in the two bias modes (eg, alternating). (Additional in one bias direction, selective in the other).

In another alternative embodiment, the sensor can be assembled with two electrochemical cells, each having an active electrode of the same or different composition, with or without associated collectors of the same or similar composition. the sensor may operate in one cell is forward biased (i.e. the counter electrode from the active electrode) operating in detecting and quantifying total NO _X, (active electrode from i.e. the counter electrode) the second cell is reverse biased It can act to detect and quantify NH _3. In this example, one cell is _{selective for NO X} and the other cell is selective for _{NH 3.} Therefore, _{both NO X} and NH ₃ can be measured with one sensor. As already mentioned, these two electrochemical cells can be physically integrated into one structure, or two physically separated electrochemical cells may be used.

As already mentioned, certain current collector layers are sensored to achieve reduced or enhanced sensitivity to one or more gas types of interest (eg, NO, NO ₂ or NH _{3) in the electrochemical cell.} Suitable for manipulating the resulting catalysts and electrochemical reactions. This is particularly useful when surface electrode arrangements are used for one or more electrochemical cells with an overwhelming (90% or more) current collector at least above the active electrode layer. However, in such an embodiment having two or more electrochemical cells, the cells are configured to share a common substrate and, in some cases, a common electrolyte layer and / or a common counter electrode layer. Can be done. 4A-H represent such sensor arrangements. However, it will be appreciated that the arrangements shown in FIGS. 4A-H can also be used in embodiments where only the active electrode material controls the behavior of the electrochemical cell. In these examples, the current collector layer can be omitted (if the active electrode layer is sufficiently conductive), or the current collector layer can be as a non-covering current collector (eg, grid or mesh). Can be configured. Note that the bias source and current measuring device are not included in FIGS. 4A-H.

In the example shown in FIGS. 4A and 4B, the sensor with two electrochemical cells is the required layer on a suitable insulating substrate (428): one common SAL (427);
One common electrolyte layer (424) laminated on SAL; first active electrode layer (422A) laminated on a part of the electrolyte layer surface; second laminated on different parts of the electrolyte layer surface Active electrode layer (422B); laminated on different parts of the electrolyte layer (eg, between the first and second active electrode layers) in close proximity to the first and second electrode layers, and thus two. One common counter electrode layer (426) that defines the boundaries of the electrochemical cells of the above; a first current collector layer (436A) laminated on the first active electrode layer; and laminated on the second active electrode layer. It is produced by sequentially laminating a second current collector layer (436B).

In the example shown in FIGS. 4C and 4D, the sensor with two electrochemical cells is a first layer laminated on one region of the required layer: insulating substrate on a suitable insulating substrate (428). SAL (427A); second SAL (427B) laminated on the second region of the insulating substrate; first electrolyte layer (424A) laminated on the first SAL (427A); second Second electrolyte layer (424B) laminated on SAL (427B); first active electrode layer (422A) laminated on a portion of the first electrolyte layer; portion of the second electrolyte layer. A first active electrode layer (422B) laminated on top of both the first and second electrolyte layers (and the area of the insulating substrate between the first and second electrolyte layers). One common counter electrode layer (thus demarcating two electrochemical cells) laminated between the first and second electrode layers, very close to the and second electrode layers. 426); The first current collector layer (436A) laminated on the first active electrode layer; and the second current collector layer (436B) laminated on the second active electrode layer. It is produced by sequentially laminating.

In the example shown in FIGS. 4E and 4F, the sensor with two electrochemical cells is a first layer laminated on one region of the required layer: insulating substrate on a suitable insulating substrate (428). SAL (427A); second SAL (427B) laminated on the second region of the insulating substrate; first electrolyte layer (424A) laminated on the first SAL (427A); second Second electrolyte layer (424B) laminated on SAL (427B); first active electrode layer (422A) laminated on a portion of the first electrolyte layer; portion of the second electrolyte layer. Second active electrode layer (422B) laminated on top of; laminated on top of a first electrolyte layer very close to the first electrode layer (thus demarcating the boundaries of the first electrochemical cell). 1st counter electrode layer (426A); a second layered on top of a second electrolyte layer very close to the second electrode layer (thus defining the boundaries of the second electrochemical cell). Counter electrode layer (426B); first current collector layer (426A) laminated on the first active electrode layer; and second current collector laminated on the second active electrode layer. It is produced by sequentially laminating layers (436B).

The examples shown in FIGS. 4G and 4H are similar to the examples in FIGS. 4C and 4D.
However, in the embodiments of FIGS. 4G and 4H, the active and counter electrodes are interconnected, thereby increasing the effective area of the surface electrodes while minimizing the gaps between the electrodes.

Figures 5-11 show additional sensor embodiments (not on scale), in these examples of one sense element (ie, one electrochemical cell), each of which is a SAL (527, 627, 727, 827). , 927, 1027, 1127). In FIGS. 5 and 6, the SAL (527,627) is completely encapsulated between the electrolyte membrane (524,624) and the substrate (528,628). In FIGS. 7-11, the SAL (727, 827, 927, 1027, 1127) is located between the electrolyte layer (724, 824, 924, 1024, 1124) and the substrate (728, 828, 928, 1028, 1128). Not completely enclosed. Instead, the SAL is simply located between the electrolyte layer and the substrate, and part of the SAL is exposed. In the sensors of FIGS. 5 and 6, the SAL can be configured in this same way, and in the sensors of FIGS. 7-11 the SAL can instead be fully encapsulated as in the case of FIGS. 5 and 6. Will be understood.

In FIG. 5, the sense element is an insulating substrate (528), a conductive signal amplification layer (527), a ceramic electrolyte layer (524) that can be porous or dense, an active electrode layer (522), and a counter electrode layer (526). ), And a current collector layer (536, 537) covering at least about 90% of the upper surfaces of the active electrode layer and the counter electrode layer, respectively. The active electrode layer and the counter electrode layer (522, 526) can have the same or different compositions. Similarly, the current collector layer (536, 537) can have the same or different composition. In general, when the active electrode layer and the counter electrode layer of the embodiments of FIGS. 5 to 8 have the same composition, the current collector layers have different compositions (that is, they are different from each other or one of the current collector layers is omitted. ing). Similarly, when the current collector layers have the same composition, the active electrode layer and the counter electrode layer have different compositions (that is, they are different from each other). As shown in FIG. 5, the bias voltage is applied between the two current collector layers and the resulting current between the current collector layers is measured.

In FIG. 6, the sense elements are an insulating substrate (628), a conductive signal amplification layer (627), a ceramic electrolyte layer (624) that can be porous or dense, one active electrode layer (622), and one. Includes two collector layers (636, 637) located on the active electrode layer (622) in a spaced relationship. The two current collector layers (636, 637) have different compositions. For example, in one embodiment, the first current collector layer (636) is an Au and ceramic phase (GDC, SDC, zirconium-doped ceria (ZDC), yttria-stabilized zirconia (YSZ), scandium-stabilized zirconia (Scandium-stabilized zirconia). The second current collector layer (637) contains Pt and a ceramic phase (GDC, SDC,) containing a cermet of ScSZ), or one of the other ceramic electrolytes mentioned as suitable for use in active electrodes. Includes cermets of zirconium-doped ceria (ZDC), yttria-stabilized zirconia (YSZ), scandium-stabilized zirconia (ScSZ), or one of the other ceramic electrolytes mentioned as suitable for use in active electrodes). .. As a specific example, one current collector contains Au / GDC and the other contains Pt / ScSz. In the configuration shown in FIG. 6, one of the current collector layers (636, 637) and a part of the active electrode layer (622) under the current collector layer (622) both provide an active electrode, and the other current collector layer and the other current collector layer. A portion of the active electrode layer (622) below it both provides a counter electrode (or a second active electrode). As shown in FIG. 6, the bias voltage is applied between the two current collector layers and the resulting current between the current collector layers is measured.

In FIG. 7, the sense element is similar to that of FIG. 5, except that the SAL is not completely encapsulated between the electrolyte layer and the substrate. Therefore, the sense element of FIG. 7 includes an insulating substrate (728), a conductive signal amplification layer (727), a porous or dense ceramic electrolyte layer (724), an active electrode layer (722), and a counter electrode layer (2). 726) and a current collector layer (736, 737) covering at least about 90% of the upper surface of the active electrode layer and the counter electrode layer, respectively. As in the arrangement of FIG. 5, the active electrode layer and the counter electrode layer (722, 726) may have the same or different composition, and the current collector layer (736, 737) may have the same or different composition. Unlike FIG. 5, in the embodiment shown in FIG. 7, the SAL (727) is not completely encapsulated between the electrolyte membrane (724) and the substrate (728). Instead, as shown, the SAL layer (727) is simply located between the electrolyte membrane layer and the substrate layer.

In FIG. 8, the sense element is similar to that of FIG. 6, with the only difference being the use of an unencapsulated SAL. Thus, the sense elements are an insulating substrate (828), a conductive signal amplification layer (827), a ceramic electrolyte layer (824) that can be porous or dense, one active electrode layer (822), and one active electrode. Includes two collector layers (836, 837) located above the layer (822) in a spaced relationship. The two current collector layers (836, 837) may have different compositions, eg, the composition described above with respect to FIG. In the configuration shown in FIG. 8, the SAL (827) is not completely encapsulated between the electrolyte membrane (824) and the substrate (828). Instead, the SAL layer (827) is simply located between the electrolyte membrane layer and the substrate layer.

It should be pointed out that in some examples it is optional to refer to one electrode as the "pair electrode" and the other as the "active electrode" in the sensor embodiments described herein. .. For example, the direction in which electron and ionic currents flow between the two electrodes can be changed by switching the bias direction of one to the other. Therefore, the counter electrode in FIGS. 5-8, if present, can also be characterized as a second active electrode layer.

The various layers of the embodiments shown in FIGS. 5-8 can be any of the various compositions described herein. As a specific example, the substrate can be alumina, the SAL can be Pt, and the electrolyte layer can be GDC. _{The active electrode can be a molybdate or tungstate compound (eg MgWO 4} or BaWO ₄ ) in combination with an electrolyte (eg GDC) and a metal (eg Pt). The counter electrode was combined with a metal (eg, Pt or Au), an electrolyte (eg, GDC or ScSZ) and a metal (eg, Pt or Au) cermet, or an electrolyte (eg, GDC) and a metal (eg, Pt). It can be a molybdate or tungstate compound (eg, MgWO ₄ or BaWO ₄ ). The current collector can also be a cermet of metal (eg, Pt or Au), or electrolyte (eg, GDC or ScSZ) and metal (eg, Pt or Au). In some examples, the current collector is not provided above the counter electrode. In a more specific embodiment, the current collector on the active electrode comprises a cermet selected from Au / GDC, Pt / GDC, and Pt / ScSZ; the counter electrode (without the current collector on top). Includes a cermet selected from Au / GDC, Pt / GDC, and Pt / ScSZ, wherein the metal (Au or Pt) used in the counter electrode cermet is used in the active electrode current collector cermet. It is different from the metal (Pt or Au) to be used.

In yet a further alternative embodiment, the SAL can allow the use of a single layer electrode rather than a combination of active / counter electrode and current collector layer. In addition, a significant amount of the modified electrolyte layer is sufficient to allow a significant amount of the ceramic electrolyte material (eg, more than about 60% by volume, or the electrolyte material above its percoration limit and the non-electrolyte material below the percoration limit). ), As a result, if the modified electrolyte layer activity conducts electricity primarily through oxygen ions, then SAL is used to combine the active electrode and certain components of the electrolyte layer. (Or can be characterized by the removal of the electrolyte layer under one or both of the electrodes). In this example, having two different current collector materials can provide differentiation between the electrodes. FIG. 9 shows such an embodiment of a sense element using SAL (927).

In FIG. 9, the sense element is mounted on a portion of the top surface of an insulating substrate (928), a conductive signal amplification layer (927), a porous or dense ceramic electrolyte layer (924), and an electrolyte layer (924). A first electrode layer (922) located and a second electrode layer (926) located adjacent to the first electrode layer (922) and above another portion of the upper surface of the electrolyte layer (924). including. The first and second electrodes (922,926) (eg, the active electrode and the counter electrode) have different compositions and the various compositions described herein for the active electrode, counter electrode or current collector. Can include any of.

The electrolyte layer (924) can be, for example, a dope ceria or dope zirconia electrolyte, but instead it contains at least about 60% by volume of the dope ceria or dope zirconia electrolyte (eg, GDC, SDC, ZDC, YSZ, or ScSZ). One or more of the molyte or tungstate compounds already described herein (eg, MgWO ₄ or BaWO ₄ ); and / or one or more metals such as Pt, Pd, Rh, Ru, or Ir (eg, Pt, Pd, Rh, Ru, or Ir). Alternatively, it can be a modified electrolyte material, including in combination with their alloys or mixtures). As a specific example, the modified electrolyte layer comprises from about 60% to about 95% by volume of dope ceria or dope zirconia electrolyte (eg, GDC, SDC, ZDC, YSZ, or ScSZ); and from about 5% to about 40. Includes a molybdate or tungstate compound in combination with a metal selected from the group consisting of Pt, Pd, Rh, Ru, and Ir.

By using the modified electrolyte layer in the embodiment of FIG. 9, the benefits of the molybdate / tungstate compound can be utilized in the electrolyte layer rather than in the additional electrode layer. When such a modified electrolyte layer is used in the embodiment of FIG. 9, the electrodes (922, 926) should have different compositions. For example, one electrode may contain cermets containing platinum and electrolytes (GDC, SDC, YSZ, ScSZ), while the other electrode contains cermets containing gold and electrolytes (GDC, SDC, YSZ, ScSZ). ..

In a further embodiment, the SAL can branch the electrolyte into two adjacent layers, each located beneath one surface electrode. In these examples, the transverse conduction between the electrodes under bias passes completely through the SAL. Normally, oxygen ions conducted between electrodes through the electrolyte layer are converted into electrons at the interface between the first electrolyte layer and SAL. These electrons are then transported through the SAL and then react with oxygen at the interface between the SAL and the second electrolyte layer to form oxygen ions. In FIG. 10, the sense element is attached to the insulating substrate (1028), the conductive signal amplification layer (1027), the first ceramic electrolyte layer (1024A) located on a part of the SAL, and the first electrolyte layer (1024A). A second ceramic electrolyte layer (1024B) located above another portion of the adjacent SAL, a first electrode layer (1022) located above the first ceramic electrolyte layer (1024A), and a second ceramic. One such embodiment includes a second electrode layer (1026) located above the electrolyte layer (1024B). The first and second electrodes (1022, 1026) (eg, the active electrode and the counter electrode) have different compositions and the various compositions described herein for the active electrode, counter electrode or current collector. Can include any of. The first and second electrolyte layers may have the same or different composition and may contain, for example, a dope ceria or dope zirconia electrolyte, or instead contain a modified electrolyte material as described above with respect to FIG. Can be done.

FIG. 11 shows yet another alternative embodiment of a sense device that uses a branched electrolyte layer. In FIG. 11, the sense element is formed on an insulating substrate (1128), a conductive signal amplification layer (1127), a first ceramic electrolyte layer (1124A) located on a part of SAL, and a first electrolyte layer (1124A). A second ceramic electrolyte layer (1124B) located on another portion of the adjacent SAL, a first electrode layer (1122) located on the first ceramic electrolyte layer (1024A), and a first electrode layer (1122). ), A second electrode layer (1126) located above the second ceramic electrolyte layer (1124B). The first and second electrodes (1122, 1126) (eg, the active electrode and the counter electrode) have the same or different composition and are described herein for a variety of active electrodes, counter electrodes or current collectors. Can contain any of the above compositions. The first and second electrolyte layers may have the same or different composition and may contain, for example, a dope ceria or dope zirconia electrolyte, or instead contain a modified electrolyte material as described above with respect to FIG. Can be done. As an example, the first electrolyte layer (1124A) contains a dope ceria or dope zirconia electrolyte, while the second electrolyte layer contains a modified electrolyte material as described above with respect to FIG. 9 (eg, molybdenum). The acid salt compound is included with GDC or SDC).

The sensor embodiments described herein typically include a substrate in combination with the described electrochemical cells to provide mechanical support. The substrate may include any suitable insulating material, such as an insulating ceramic material such as aluminum oxide, magnesium oxide, magnesium aluminate, mullite, steatite, or cordierite. Aluminum oxide is particularly useful as a substrate material. The device can also be assembled with a metal or alloy as the substrate material (instead of the insulating material). In these examples, the metal substrate itself functions as a signal amplification layer. This is a method in which an electrolyte material (or an electrolyte containing an active electrode material) is directly laminated on a metal substrate in such a manner that an insulating layer is not formed at an interface between the layers of the electrolyte layer, the active electrode layer, and the current collector layer. Need to do. For example, various layers can be laminated using a sputtering process (or similar).

The sensors and sensor systems herein can be configured to suit a variety of application environments, including structural robustness, the addition of one or more heaters to control the sensor temperature, and / Or include a modified substrate to bring in the addition of resistance temperature detectors (“RTDs”), thermistors, thermocouples or other devices that measure temperature and feed back to electronic controls for temperature control. Can be done. An alternative temperature measurement technique based on the use of the impedance of the electrolyte layer at a particular frequency can also be used (this technique would require adding certain functionality to the sensor device structure). .. Modifications can also be made to the overall sensor size and shape, the exterior and shielding that accommodates and protects the sensor, and the appropriate leads and wiring to transmit the sensor signal to an external device or application.

The sensor can optionally include a heater that is electrically isolated from the electrolyte and electrodes. In some embodiments, the heater includes, for example, a resistance heater formed from a conductive metal such as, but not limited to, platinum, palladium, silver, or the like. The heater may be applied or embedded in the substrate, for example, or may be applied to the cell by another insulating layer such as an additional insulating layer (eg, aluminum oxide). In yet another embodiment, a temperature measuring mechanism is applied to the sensor to measure the temperature and feed it back to the electronic controller to enable closed-loop temperature control. For example, the temperature measuring mechanism is a resistance temperature detector (RTD) made of a conductive metal or metal / ceramic composite material (eg, platinum or platinum-based cermet) with a high temperature coefficient of resistance.

In certain embodiments as shown in FIG. 2, the electrochemical sensor is made using tape casting and screen printing techniques commonly used during the manufacture of multilayer ceramic capacitors and multilayer ceramic substrates. The first part of this process involves tape casting of aluminum oxide sheets (or tapes). In the green state, a via hole is cut into the substrate using a laser cutter or punch to provide an electrical path connection from the embedded heater or other structure to the contact pad on the outer surface of the ceramic element. Platinum (or platinum-based material) is screen-printed on one side of green aluminum oxide tape in a pattern that can be a heater after sintering. Also, in the green state, SAL is screen-printed on one side of the green aluminum oxide tape.

In the various embodiments described herein, the SAL is continuous configured to extend below at least about 50% of the surface electrodes, usually including extending below the gap between the two electrodes. It is a conductive layer. In other words, the SAL is located below the surface electrodes and has a size of about 50% to about 120% of the combined size of the surface electrodes (including the gaps between the electrodes). For example, as shown in FIG. 7, the cross-sectional length (L) of the SAL (727) is about 120% of the end-to-end width (W) of the electrodes (722, 726). In FIGS. 5 and 6, the size of the SAL is approximately the same as the electrode area (including the gap between the surface electrodes).

The SAL can be made of a variety of conductive materials suitable for the manufacture of sensors. Suitable materials include Pt, Pd, Au, Ag, alloys of the aforementioned metals (eg alloys of Pt and Pd, Au and / or Au), or other conductive metal or ceramic materials. Platinum is especially useful.

Returning to the embodiment of FIG. 2, after the formation of the SAL layer, multiple layers of green aluminum oxide tape are aligned and stacked so that the screen-printed heater layer is in the center and the SAL is on opposite sides. .. The stacked green alumina tapes are then laminated by applying uniaxial pressure at a slightly higher temperature. The via hole is filled with a conductive ink such as platinum, and the laminate is sintered at a high temperature to solidify the aluminum oxide substrate. A porous ceria-based electrolyte (GDC or SDC) layer (or other electrolyte material) is then applied over the SAL and on the surface around the substrate by screen printing and sintering. Platinum (or platinum-based material) is screen-printed on the outer surface of the sintering element in a pattern that can be an RTD that allows temperature measurement after sintering. Alternatively, another RTD suitable material may be applied in the green state prior to sintering the aluminum oxide substrate and co-sintered with it. A glass layer may be applied over the RTD and cured to protect the RTD during application. Alternatively, both the heater and the RTD layer may be embedded in a green substrate and a connection made of platinum vias (as described above), or only the platinum RTD may be embedded in the substrate and the heater layer. May be printed on the outer surface and protected by a glass layer. Alternatively, the RTD may be omitted and alternative means for temperature measurement and control may be used.

The manufacture of the electrochemical cell or sensor then annealies the electrode layer after screen printing the active electrode layer and counter electrode layer (made with any of the compositions described herein) on the electrolyte layer. It is completed by sintering the electrode layer to promote adhesion. Next, the current collector layer can be applied in a similar manner. Porous ceramic coatings, such as zeolite or gamma alumina, can be further applied over the electrodes / current collectors to protect these layers during application and calcinate to improve adhesion. Of note, multiple electrochemical cells or sensors can be simultaneously produced by the above process by array processing.

The sensor system is formed, for example, by connecting one or more sensors described herein with one or more electronic control devices, the electronic control device applying a controllably biased voltage (eg, eg). It is configured to control the temperature (by modulating the pulse width of the input voltage to the heater) based on the sensor temperature measurements provided to the controller. In some embodiments, the control device is configured to provide a tuned sensor output, such as a calibrated or linearized output.

A method of detecting, detecting, and / or monitoring the concentration of one or more target gas species such as _{NO X} and / or NH ₃ using any of the various sensors and sensor systems described herein. Is also provided. In these methods, a bias voltage is applied to the electrochemical cell of the sensor and the resulting current is measured. The measured current is associated with the target gas species at the sensor temperature based on previously collected sensor data. In general, the measured current changes as the concentration of the target gas species in the gas sample or gas stream increases. By using predetermined sensor response data for any given sensor operating temperature and applied bias voltage, the target gas type can be determined based on the generated current through the sensor cell.

The sensors, sensor systems and methods described herein can also be adapted to detect a wide variety of other gas species, including carbon monoxide (CO), methane (CH ₄ ), ethanol ( Includes C ₂ H ₆ ), hydrogen sulfide (H ₂ S), sulfur oxides (SOx), hydrogen (H ₂ ), refrigerants, oxygen (O ₂ ), volatile organic compounds (VOC) and other hydrocarbons. .. A variety of additional features and advantages of amperometric sensors, sensor systems and methods will become apparent from the devices and results obtained described in the Examples below.

As I mentioned before, in order to provide a measure of both of the NO _X concentration and the NH ₃ concentration, the sensor can be assembled in two active electrodes, providing two different electrochemical cells effectively be able to. For testing, an exemplary sensor was made as a single electrochemical cell and tested under conditions that allowed the design of _{a dual NO X} / NH _{3 sensor with multiple electrochemical cells.} This test applicants discovered several approaches for making a sensor for measuring the concentration of both of the NO _X and NH _3. These approaches are usually one electrochemical cell, the cell exhibits an additional response with respect to NO _X and NH ₃ (i.e., exhibit the same response for all three species) produced works as And the second electrochemical cell, in the presence of _{NH 3} , the cell shows a selective reaction with respect _{to NO X} (ie, the same response to _{NO and NO 2 and to NH 3)} . Accompanied by making and operating to show a reduced response or no response).

The additional response is that the magnitude of the signal provided by the electrochemical cell is proportional to the total concentration of the gas sample or analyte in the gas stream being analyzed (eg, NO, NO ₂ and NH _3). means. Accordingly, the amperometric sensor as described herein, NO, individual electrochemical cell sensor shown an additional response to _{NO 2} and NH ₃ are, NO, the total concentration of _{NO 2} and NH ₃ Will result in a proportional signal. In other words, the electrochemical cell of the sensor _{produces about the same current when exposed to given concentrations of NO, NO 2} and NH ₃ (eg, 20 ppm NO, 20 ppm NO ₂ or 20 ppm NH _{3 in the electrochemical cell).} It exhibits approximately equal responses to _{NO, NO 2} and NH ₃ so that it produces approximately the same current when exposed to. In particular, the individual electrochemical cells of the sensor have a sensitivity to each of the two or more species in the range of ± 20% for a given concentration of gas analyte in the range of 10-200 ppm. It is considered to be additional with respect to these analytical species. As used herein, sensitivity is the rate of change of the current signal compared to the current signal in the absence of the species of analysis. In some embodiments, the sensitivity of the additional electrochemical cell to two or more species is in the range of ± 10%, or even ± 5%.

One electrochemical cell of the sensor shows an additional response to more than one target gas species (eg NO _X and NH ₃ ), while the other electrochemical cell of the sensor is one of the target gas species (eg NO). _{It is} minimally responsive or non-responsive to either X or NH _{3), i.e. a selective response.} The selectivity depends on either the configuration of the second electrochemical cell (eg, selection of active electrode material and / or current collector) and / or the mode of operation of the second electrochemical cell (eg, bias direction). Given. The electrochemical cell of the sensor is this particular if its sensitivity to a particular analyte is less than 20% of its sensitivity to one or more other analytes at a given concentration in the range of 10-200 ppm. Minimal responsiveness (ie selective) with respect to the analyte. In some embodiments, the sensitivity to one analyte is less than 10%, or even less than 5%, of the sensitivity to one or more other analytes. In one particular embodiment, the first electrochemical cell of _{the sensor is additive for NO X} and NH ₃ , and the second electrochemical cell of the sensor is NO _X responsive but minimal for _{NH 3.} The second electrochemical cell preferably exhibits additional properties with respect to _{NO and NO 2} if it is only responsive or non-responsive.

The present inventors have found that in order to obtain additional and selective sensor response (e.g., to allow for dual NO X _/ NH ₃ detection and quantification), to adjust the collector of two cells By doing so, it has been found that it is possible to provide two electrochemical cells, one having an additional response to two or more target gas species and one having a selective response to at least one target gas species. Signal strength and, in some cases, selectivity are also enhanced by SAL. These findings are that the current collector creates a device that completely covers the surface of the active electrode (coverage> about 90%), and that both the counter electrode and the active electrode are spaced on the same surface of the electrolyte. This was achieved by utilizing a device structure that is laminated in a relationship. As demonstrated by the tests further reported herein, we have found that the electrochemical detection response will be controlled by the current collector in this alternative configuration. For example, in an electrochemical cell having the same active electrode ( _{based on MgWO 4} or BaWO ₄ ), the additional sensor response is realized in the cell incorporating the platinum-based current collector on top of the active electrode, and the selective response is gold. It is realized by a cell that incorporates the system current collector on the active electrode. This becomes more apparent with the examples further described herein.

In FIGS. 21-24, one or both of the electrodes include a current collector layer located above the electrolyte layer, with the catalyst layer located above the current collector layer and covering at least about 90% of the top surface of the current collector layer. (FIGS. 22 and 24) or a further alternative embodiment of the sense element of the present disclosure is shown in which the current collector layer is completely encapsulated between the catalyst layer and the electrolyte layer (FIGS. 21 and 23). As shown, SAL is also provided in the embodiments of FIGS. 21-25.

In the embodiments of FIGS. 21-24, the current collector layer has a higher conductivity than the catalyst layer. The catalyst layer is a composition comprising any of the materials previously described herein, particularly molybdates or tungstates, for use as an active electrode layer (eg, electrolyte materials and metals, as described above). It may be a molybdate or tungstate compound) in combination with. The current collector layer is any of the materials previously described herein for use as a current collector layer, particularly metal (eg Pt or Au) or electrolyte and metal cermets (eg Au / GDC). , Pt / GDC, or Pt / ScSZ). As shown, the bias voltage is applied between the current collector layers and the resulting signal is also obtained from the current collector layers, but the catalyst layer is NO, NO ₂ and NH present at the catalyst / current collector interface. _{It is believed that the concentration of 3} is manipulated, thereby changing the amount of current when a bias is applied (compared to the amount of current in the absence of a catalyst layer).

In FIG. 21, the sense element is mounted on a portion of the top surface of an insulating substrate (2028), a conductive signal amplification layer (2027), a porous or dense ceramic electrolyte layer (2024), and an electrolyte layer (2024). A first collector layer (2036) located and a second collection located adjacent to the first collector layer (2036) and above another portion of the top surface of the electrolyte layer (2024). Includes an electrical layer (2037). The first catalyst layer (2022) encloses the first current collector layer (2036) (that is, between the catalyst and the electrolyte), and the second catalyst layer (2026) is the second current collector layer. (2037) is enclosed. The two current collector layers (2036, 2037) may have the same or different composition, and the two catalyst layers (2022, 2026) may have the same or different composition. However, at least one of the current collector layer or the catalyst layer should have a different composition than the other current collector layer or catalyst layer (ie, 2036 has a different composition than 2037 and / or 2022 has a different composition than 2026). It will also be appreciated that, as shown, SAL (2027) is optionally fully encapsulated rather than partially encapsulated (also applies to the sense elements of FIGS. 22-24). ..

The sense element of FIG. 22 is similar to that of FIG. 21, but in this embodiment the catalyst layer (2122, 2126) completely encapsulates the underlying current collector layer (2136, 2137). No. The sense element of FIG. 22 also includes an insulating substrate (2128), a conductive signal amplification layer (2127), and a ceramic electrolyte layer (2124), which can be porous or dense, as before. Again, the two current collector layers (2136, 2137) may have the same or different composition, and the two catalyst layers (2122, 2126) may have the same or different composition. However, at least one of the current collector layer or the catalyst layer should have a different composition than the other current collector layer or catalyst layer (ie, 2136 has a different composition than 2137 and / or 2122 has a different composition than 2126).

In the embodiment of FIG. 23, the sense element is a portion of the top surface of an insulating substrate (2228), a conductive signal amplification layer (2227), a porous or dense ceramic electrolyte layer (2224), and an electrolyte layer (2224). It includes a current collector layer (2236) located above, a counter electrode layer (2226) adjacent to the current collector layer (2236) and above another portion of the upper surface of the electrolyte layer (2224). The catalyst layer (2222) encloses the current collector layer (2236) (ie, between the catalyst and the electrolyte). The counter electrode layer 2226 may include any of the compositions described herein for use as a counter electrode or as a current collector.

The sense element of FIG. 24 is similar to that of FIG. 23, but in this embodiment the catalyst layer (2322) does not completely enclose the underlying current collector layer (2336). The sense element of FIG. 24 also has an insulating substrate (2328), a conductive signal amplification layer (2327), a porous or dense ceramic electrolyte layer (2324), and a counter electrode layer (2326) as before. include.

Finally, the sense element of FIG. 25 includes a catalyst layer (2422) that encloses the current collector layer (2436) (ie, between the catalyst and the electrolyte (2424)). However, in this embodiment, the second (pair) electrode (2426) is below the electrolyte layer (2424) such that the pair electrode (2426) is located between the electrolyte layer (2424) and the substrate (2422). It is buried in. Therefore, the sense element of FIG. 25 does not include SAL.

Examples 1 and 2
The effect of the signal amplification layer on the sensor performance was determined using sensors of the same structure except for one sensor containing the SAL encapsulated between the electrolyte layer and the substrate. As shown in FIGS. 12 and 13, two sensors similar to those shown in FIG. 1 were assembled. Thus, both sensors included an Al ₂ O ₃ substrate, the same Pt-BaWO ₄ / GDC active electrode layer and a Pt / GDC current collector and counter electrode layer. The same treatment method was used to prepare and stack these layers. The sensor of Example 1 was manufactured without including the platinum signal amplification layer, but the sensor of Example 2 contained a platinum signal amplification layer between the GDC electrolyte layer and the substrate, and the SAL was completely enclosed. (As seen in FIG. 13). It should be noted that the dimensions of the sensor structure shown in FIGS. 12 and 13 are not on scale. The gap between the active electrode and the counter electrode on the electrolyte surface was about 500 microns, whereas the thickness of the GDC electrolyte layer (and thus the gap between the active electrode and the embedded platinum layer) was about 30 microns. Met.

The sensors of Examples 1 and 2 were maintained at a temperature of 525 ° C., with 77% by volume N ₂ , 10% by volume O ₂ , 8% by volume CO ₂ , 5% by volume H ₂ O and 1 ppm. The SO ₂ baseline was exposed to a simulated diesel exhaust atmosphere. A 200 mV forward bias was applied from the Pt / GDC current collector to the Pt / GDC counter electrode layer and the resulting current was determined by measuring the voltage across a 100 ohm shunt resistor. The baseline signal (exposed only to the simulated diesel exhaust at the baseline) was measured, as was the signal (ie, current) when _{100 ppm NO, NO 2} and NH _{3 were added to the simulated exhaust.} The sensitivity of NO, NO ₂ and NH ₃ to 100 ppm exposure was determined as the rate of change of the current signal in the presence of the analyte. The results of these tests are shown in FIGS. 12 and 13, which show that the platinum signal amplification layer increased the baseline signal from 0.28 to 3.8 μA (more than 10-fold increase). Moreover, the sensitivity to each of the gas species tested has also increased significantly, resulting in significantly more useful sensors. SAL provided a lateral current path and effectively increased the active and counter electrode regions. Therefore, even if two additional electrochemical reactions (conversion of oxygen ions at the GDC / Pt-SAL interface to electrons and conversion of electrons at the Pt-SAL / GDC interface back to oxygen ions) must occur. It can be imagined that the lateral current path provided by platinum is the faster path of the charge carrier.

Examples 3-10
The ability to adjust the response characteristics of the sensor by changing the composition of the electrodes and current collector layer, made various sensors, simulated diesel exhaust (baseline) and simulated exhaust containing _{100 ppm NO, NO 2} or NH _3. Demonstrated by determining its performance in. The sensors of Examples 3-10 were made as described above for Example 2 (ie, the structure of FIG. 1 containing the fully encapsulated Pt SAL). Therefore, the common electrolyte layer (24) was the GDC, and the active electrode (22), current collector (36) and counter electrode (26) layers were altered as reported in Table 1 below. The sensor was tested with the forward (positive) bias applied from the current collector (36) to the counter electrode (26) layer. The sensors were tested at a temperature of 525 ° C. with a bias voltage of 200 mV, as described above for Examples 1 and 2. The baseline gas atmosphere consists of 8% by volume CO ₂ , 5% by volume H ₂ O, 1 ppm SO ₂ , 10% by volume O ₂ , and 77% by volume N ₂ , with 100 ppm added to it. Sensor responses were measured for exposure to a baseline atmosphere containing NO, 100 ppm NO ₂ , or 100 ppm NH _{3 analysts.} The results are summarized in Table 2 and explained in subsequent paragraphs.

The test data obtained for the sensor of Example 3 including the Pt-MgWO ₄ / GDC active electrode, Au / GDC current collector and Pt / ScSZ counter electrode are shown in Table 2 and FIG. Applying a 200 mV bias at a temperature of 525 ° C., the sensor showed a baseline current signal of 8.9 μA and _{selective detection behavior for NO and NO 2} (for 100 ppm NO and 100 ppm NO ₂₎ . 33% and 43% sensitivity, respectively, and only 2% sensitivity to _{100 ppm NH 3).} The lack of sensitivity to NH ₃ was also seen in FIG. 14, where the signal was _{only slightly higher than the baseline signal when 100 ppm NH 3} was added to the baseline simulated diesel exhaust (8. 9.1 μA for 9 μA).

The test data obtained for the sensor of Example 4 including the Pt-MgWO ₄ / GDC active electrode, the Pt / SCSZ current collector and the Pt / ScSZ counter electrode are shown in Table 2 and FIG. Applying a 200 mV bias at a temperature of 525 ° C., the sensor showed a baseline current signal of 6.5 μA _{and additional detection behavior for NO, NO 2} and NH ₃ (100 ppm NO, 100 ppm NO ₂ and 39%, 31% and 33% sensitivities to 100 ppm NH _{3 respectively).}

The test data obtained for the sensor of Example 5 including the Pt-BaWO ₄ / GDC active electrode, the Au / GDC current collector and the Pt / ScSZ counter electrode are shown in Table 2 and FIG. The 200mV bias is applied at a temperature of 525 ° C., the sensor compares the baseline current signal 5.4Myuei, showed nominally selective detection behavior for NO and NO2 (49% sensitivity to NH ₃ Sensitivity of 91% and 108%, respectively). Therefore, by replacing the MgWO ₄ active electrodes of the sensor in BaWO _4, but considerable increase of the NO _X sensitivity brought, it was also observed significant NH ₃ response. For selective NO _X detection in order to improve the usefulness of the sensor, for example, either by varying the thickness and / or porosity of the active electrode and the current collector layer, or varying the composition of the current collector layer the like, it is necessary to reduce the NH ₃ response,

The test data obtained for the sensor of Example 6 including the Pt-BaWO ₄ / GDC active electrode, the Pt / SCSZ current collector and the Pt / ScSZ counter electrode are shown in Table 2 and FIG. Applying a 200 mV bias at a temperature of 525 ° C., the sensor exhibited a 3.8 μA baseline current signal and _{additional detection behavior for NO, NO 2} and NH ₃ (100 ppm NO, 100 ppm NO ₂ and Sensitivity of 167%, 164% and 164% to 100 ppm NH _{3 respectively).} Therefore, by replacing the MgWO ₄ active electrode of the additional sensor in BaWO _4, 4-fold increase of the NO _X and NH ₃ sensitivity brought.

Table 2 shows the test data obtained for the sensor of Example 7 including the MgWO ₄ / GDC active electrode (the active electrode does not contain platinum), the Pt / SCSZ current collector and the Pt / ScSZ counter electrode. Applying a 200 mV bias at a temperature of 525 ° C., the sensor showed a very low baseline current signal of 0.85 μA and an additional sensitivity lower than the relatively low optimum (100 ppm NO, 100 ppm NO _2). And 21%, 13% and 21% sensitivity to 100 ppm NH _3). Data, in order to obtain a more desirable NO _X and NH ₃ detection behavior, shows the benefits of the inclusion of platinum (or other metal) to the active electrode.

Table 2 shows test data obtained for the sensor of Example 8 provided with a Pt-MgWO ₄ / GDC active electrode, a platinum current collector and a platinum counter electrode (collector or counter electrode does not contain ScSZ or GDC). Applying a 200 mV bias at a temperature of 525 ° C., the sensor was 6% each for a very reduced baseline current signal of 0.14 μA and 100 ppm NO, 100 ppm NO ₂ and 100 ppm NH _3. , 7% and 1% showed very low sensitivity. The data show the advantages (at least for this particular sensor configuration and active electrode material) of including the electrolyte material (eg ScSZ or GDC) in the current collector and counter electrode layer.

Table 2 shows the test data obtained for the sensor of Example 9 including the Pt-MgWO ₄ / GDC active electrode, the Au / GDC current collector and the Au / GDC counter electrode. Applying a 200 mV bias at a temperature of 525 ° C., the sensor has a relatively high baseline current signal of 9.4 μA and 23% for _{100 ppm NO, 100 ppm NO 2} and 100 ppm NH _{3, respectively.} It showed a sensitivity of 45% and 30%. Therefore, replacing Pt / ScSZ of the counter electrode with Au / GDC reduces selectivity as compared to Example 3, and thus changing the metal used for the cermet counter electrode for the purpose of manipulating the sensor response. And with respect to this particular sensor configuration and active electrode material, the advantages of using platinum rather than gold for the cermet counter electrode were shown.

Table 2 shows the test data obtained for the sensor of Example 10 including the Pt-MgWO ₄ / GDC active electrode, the Pt / ScSZ current collector and the Au / GDC counter electrode. Applying a 200 mV bias at a temperature of 525 ° C., the sensor is 95%, 108% and 95% and 108% for a _{baseline current signal of 4.7 μA and 100 ppm NO, 100 ppm NO 2} and 100 ppm NH _{3, respectively.} It showed a sensitivity of 181%. Therefore, by replacing the counter electrode Pt / ScSZ with Au / GDC, additional behavior is lost and platinum (not gold) may be present in the cermet counter electrode for this particular sensor configuration and active electrode material. It was confirmed again that it was preferable.

Examples 11 and 12
Demonstrations of how the sensors described herein can be adapted for ammonia detection are described in Examples 11 and 12. The sensor was made as described above for Example 2 (ie, the structure of FIG. 1 containing a fully encapsulated Pt SAL). As shown in FIGS. 18 and 19, the sensor used was an Al ₂ O ₃ substrate, a Pt-MgWO ₄ / GDC active electrode layer, an Au / GDC current collector layer and a Pt / GDC counter electrode layer. Also, compared to previous examples, Pt-MgWO ₄ / GDC, Pt / GDC and Au / GDC layers were made with higher surface area components and higher annealing temperatures, thereby producing the density of these layers ( And durability) increased.

A baseline gas atmosphere consisting of 8% by volume CO ₂ , 5% by volume H ₂ O, 1 ppm SO ₂ , 2 to 20% by volume O ₂ , and 67 to 85% by volume N _{2 at 525 ° C.} Tested in, sensor responses were also _{observed for exposure to 100 ppm NO, 100 ppm NO 2} , or 100 ppm NH ₃ analysts at bias voltages ranging from -200 to +200 mV. The data obtained by the forward bias of 200 mV is shown in FIG. When tested in forward bias mode (ie, oxygen ions are generated in the active electrode and conducted through the electrolyte to the counter electrode), the sensor is highly cross-sensitive to oxygen and the _{response to NO and NO 2} is positive. The numbers were not the same (33% and 108%, respectively), the _{response to NH 3} was a large negative number (-86%), and the oxygen content was 5% by volume.

The data obtained by the reverse bias of −200 mV is shown in FIG. When tested in reverse bias mode (ie, oxygen ions are generated at the counter electrode and conducted through the electrolyte to the active electrode), the sensor is slightly cross-sensitive to oxygen, oxygen, NO and NO _2. response is the number of slightly positive (respectively, 31% and 25%) and a number of NH ₃ response is large positive (267%).

Different reverse bias voltage (at 525 ° C.), shown in Figure 20 the influence of the NO _X and NH ₃ responses oxygen content. At low bias voltage (-30 and -80 mV), NH ₃ response is slightly cross-sensitive to oxygen, the more the signal intensity oxygen content is high was low. However, at high bias voltages (-140 and -200 mV), NH ₃ sensitivity was insensitive to oxygen content. The combination of very high sensitivity to _{NH 3 (compared to NO X} ) and insensitivity to oxygen is advantageous for use as a _{stand-alone NH 3} sensor or as a dual NO _X / NH ₃ sensor NH _{3 selective cell.} be.

Although various embodiments of the sensor, as well as how the sensor is manufactured and used, have been described in detail above, the components, features and configurations, as well as the method of manufacturing the device and the methods described herein are described herein. It is of course understood that the specification is not limited to the particular embodiments described in the document. For example, the components, features, configurations, and manufacturing or usage described in the context of one embodiment above may be incorporated into any of the other embodiments. Further, but not limited to the further description described below, additional and alternative suitable components, features, configurations, and methods of using the device, as well as various methods of exchanging the teachings herein in combination. It will be apparent to those skilled in the art in light of the teachings herein.

Although various embodiments have been shown and described herein, further modifications and adaptations of the methods, systems and devices described herein have been accomplished by one of ordinary skill in the art without departing from the scope of this disclosure. good. Some of such possible changes will be mentioned, and others will be apparent to those skilled in the art. Therefore, it is understood that the scope of the invention should be considered with respect to the following claims and is not limited to the structural and operational details shown and described in the specification and drawings.

Claims (21)

An amperometric electrochemical sensor for measuring the concentration of one or more target gas species in a gas sample or gas stream, said sensor.
First and second surface electrodes;
Oxygen ion conductive solid electrolyte layer;
A conductive passive signal amplification layer (“SAL”); and a bias source for applying no electrical bias to the SAL but between the first and second surface electrodes;
The first and second surface electrodes are located on the same surface of the electrolyte layer, and at least a part of the electrolyte layer is between the surface electrode and the SAL. The sensor is located in, so that the SAL is in direct conductive contact with the electrolyte layer but not with the surface electrode. Said first surface electrode comprises at least one molybdate or tungstate compound, further wherein said at least one molybdate or tungstate _{compound, A X (Mo (1-} Z) W Z) Y O _{(X + 3Y)} (In the formula, X and Y are independently selected from integers 1 to 5, 0 ≦ Z ≦ 1, and A is Mg, Zn, Ni, Co, Fe, Mn, Cu, The sensor of claim 1, comprising (one or more of Ca, Sr, Ba, and Pb). The sensor according to claim 2, wherein the at least one molybdate or tungstate compound comprises MgMoO ₄ , MgWO ₄ , BaWO ₄ or CoWO _4. The sensor according to claim 2 or 3, wherein the first surface electrode comprises a composite mixture of (a) at least one molybdate or tungstate compound; and (b) at least one ceramic electrolyte material. Said first surface electrode further comprises from about 0.1 wt% to 10 wt%, Pt, Pd, Rh, Ru, Ir, and at least one metal selected from the group consisting of an alloy or a mixture , The sensor according to claim 4. The sensor according to claim 1, wherein the first surface electrode includes a ceramic phase and a metal phase. The ceramic phase of the first surface electrode contains a zirconia-based electrolyte material, a ceria-based electrolyte material, a bismuth oxide-based electrolyte material, a lanthanum gallium oxide-based electrolyte material, aluminum oxide or magnesium oxide, or a mixture thereof, and the metal phase. 6. The sensor of claim 6, wherein the sensor comprises Ag, Pt, Pd, Rh, Ru and Ir, or an alloy or mixture thereof. The second surface electrode
-Ag, metal selected Au, Pt, Pd, Rh, Ru, from the group consisting of Ir and their alloys or mixtures thereof;
The sensor according to any one of claims 1 to 7, selected from the group consisting of − conductive perovskite; and − metal and ceramic cermets. The second surface electrode is (a) platinum or gold; and (b) gadolinium-doped ceria (“GDC”), samarium-doped ceria (“SDC”), zirconium-doped ceria (“ZDC”). ), Yttria-stabilized zirconia (“YSZ”), or scandium-stabilized zirconia (“ScSZ”): the sensor of claim 8. It further comprises a current collector layer on at least one of the first and second surface electrodes, the current collector layer.
-Precious metals selected from the group consisting of platinum, palladium, gold and silver, and two or more alloys of platinum, palladium, gold and silver;
-Alloys of platinum, palladium, gold or silver and one or more base metals; or
-The sensor of any one of claims 1-9, comprising cermet of platinum, palladium, gold or silver and a ceramic electrolyte material. The sensor according to claim 10, wherein each of the current collector layers comprises (a) platinum or gold; and (b) a cermet of GDC, SDC, ZDC, YSZ or ScSZ :. Select from the group consisting of an insulating ceramic, a metal coated with an insulating material, and a cermet coated with an insulating material, further comprising a substrate supporting each of the first and second surface electrodes, an electrolyte layer and SAL. The sensor according to any one of claims 1 to 11, wherein the SAL is located between the electrolyte layer and the substrate. 12. The sensor of claim 12, wherein the SAL is completely encapsulated between the electrolyte layer and the substrate. Select from the group consisting of an insulating ceramic, a metal coated with an insulating material, and a cermet coated with an insulating material, further comprising the respective first and second surface electrodes, an electrolyte layer and a substrate supporting the SAL. The sensor according to any one of claims 1 to 11, wherein the SAL is located in the electrolyte layer. Claims 1-14, wherein the SAL comprises a material selected from the group consisting of Pt, Pd, Au, Ag, and two or more alloys of Pt, Pd, Au and Ag; conductive ceramics; and conductive cermets. The sensor according to any one of the above. The sensor according to claim 15, wherein the SAL is essentially made of platinum. A amperometric electrochemical sensor system for measuring two or more target gas species concentrations in the gas sample or gas stream, wherein the sensor system, electric according to any one of claims 1 to 16 A sensor system comprising a first electrochemical cell, which is a chemical cell, and a second electrochemical cell containing first and second surface electrodes on an electrolyte layer. 17. The sensor system of claim 17, wherein the second electrochemical cell comprises the sensor of any one of claims 1-16. The sensor system according to claim 17 or 18, wherein the first and second electrochemical cells share at least one of a common electrolyte layer, a common second surface electrode and a common SAL. A method of detecting the concentration of one or more target gas species in a gas sample or gas stream.
(A) The step of arranging the sensor or sensor system according to any one of claims 1 to 19 such that the one or more electrochemical cells are exposed to the gas sample or stream;
(B) With the step of applying one or more biases to the one or more electrochemical cells;
(C) With the step of measuring one or more currents generated between the first and second surface electrodes of the electrochemical cell;
(D) A method comprising the step of determining the concentration of one or more target gas species based on the measured one or more currents. The method of claim 20, wherein the one or more target gas species is NO _x and / or NH _3.

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