JPH0418263B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is an electric sensor that measures a gas concentration by detecting an output generated between a working electrode membrane and a counter electrode membrane in contact with an electrolytic solution in accordance with the gas concentration. Regarding chemical gas sensors.

BACKGROUND ART Conventionally, when measuring the concentrations of two types of gases at the same time, electrochemical gas sensors are provided to measure the concentrations of each gas, and the concentrations are measured individually using these sensors. An electrochemical gas sensor used in such a case includes, for example, a container containing an electrolytic solution and a first gas sensor formed in the container.
A gas permeable first part that closes the opening and is in contact with the measurement gas.
a permeable membrane, a gas-permeable second permeable membrane that closes a second opening formed in the container and is in contact with the outside air, a working electrode membrane that is adhered to the inner surface of the first permeable membrane that is in contact with the electrolytic solution, and a second permeable membrane that is in contact with the electrolytic solution. A counter electrode film is known that is provided with a counter electrode film attached to the inner surface of the permeable membrane that is in contact with the electrolyte.

However, in the past, in order to simultaneously measure the concentrations of two types of gases as described above, it was necessary to provide an electrochemical gas sensor for each gas, which resulted in the overall size of the measuring device and its complicated structure. , there is a problem that it becomes even more expensive. Moreover, since the concentration of each gas is measured using a separate electrochemical gas sensor, if a measurement error occurs in the gas sensor, the cause of the error may be determined, such as deterioration of the electrode membrane, electrolyte solution, etc. Another problem is that it is not easy to know what is causing the deterioration of the battery, abnormality in ambient temperature, etc. because there are many factors involved.

Problems to be Solved by the Invention In this invention, the measuring device as a whole becomes larger, has a more complicated structure, and becomes more expensive.
Moreover, it solves the conventional problem that when a measurement error occurs, it is difficult to know the cause of the error.

Means for Solving the Problems These problems are, firstly, the container containing the electrolyte and the first opening formed in the container being closed and the measurement gas mixed with two types of gases being closed. a gas-permeable first permeable membrane in contact with the outside air; a gas-permeable second permeable membrane that closes a second opening formed in the container and in contact with the outside air; A first working electrode film that reacts with one gas, a second working electrode film that is deposited on the inner surface of the first permeable membrane and that reacts with the other gas, and a second working electrode film that is deposited on the inner surface of the second permeable membrane that is in contact with the electrolyte. Second, in addition to the above, a porous removal film for removing the other gas is coated on the outer surface of the first permeable membrane so as to overlap with the first working electrode film. The problem can be solved by wearing it.

Effect First, the measurement gas mixed with two types of gas is
Upon reaching the permeable membrane, this measurement gas permeates through the first permeable membrane. At least one of the gases undergoes an oxidation or reduction reaction on the surface of the first working electrode membrane in contact with the electrolytic solution, and the other gas undergoes an oxidation or reduction reaction on the surface of the second working electrode membrane in contact with the electrolytic solution. On the other hand, on the surface of the counter electrode membrane that is in contact with the electrolyte, the outside air that has passed through the second permeable membrane undergoes a reduction or oxidation reaction. As a result, an output depending on the concentration of one gas or a total output depending on the concentrations of one and the other gas appears between the first working electrode film and the counter electrode film, and between the second working electrode film and the counter electrode film. An output appears depending on the concentration of the other gas.
Then, by detecting these outputs, the concentration of each gas is measured. As mentioned above, the invention described in item 1 only needs to add one more working electrode film to the inner surface of the first permeable film of a conventional electrochemical gas sensor, so it can be miniaturized and has a simple structure. Moreover, it can be manufactured at low cost. Furthermore, since the working electrode membranes that react with each gas are placed in almost the same position, the surrounding temperature conditions are the same, and the electrolyte that comes into contact with them is also common, reducing factors and making it easier to eliminate sources of error. will be able to investigate. The above is the effect of the invention in item 1, but in the case of the invention in item 2, since the other gas is removed when passing through the removal membrane,
Only one gas can reach the first working electrode membrane. Therefore, even if the first working electrode film is made of a material that reacts with both gases, the concentrations of both gases can be measured individually and accurately. Furthermore, since the removal membrane is a porous membrane, the pressure loss when gas passes through it is small, and as a result, it can be applied to a diffusion type gas sensor and can be used for a long period of time.

Embodiment Hereinafter, an embodiment of the present invention will be described based on the drawings.

The drawing shows an electrochemical gas sensor that simultaneously measures the concentrations of carbon monoxide gas and hydrogen sulfide gas, and 1 is a container containing an electrolytic solution 2 made of an aqueous solution of sulfuric acid, phosphoric acid, or the like. A first opening 3 is formed in this container 1, and this first opening 3 is closed by a gas permeable first permeable membrane 4 made of Teflon or the like. This first permeable membrane 4 is in contact with the measurement gas mixed with carbon monoxide gas and hydrogen sulfide gas, and can also transmit these carbon monoxide gases, hydrogen sulfide gases, and the like. A second opening 3 is located in the container 1 opposite the first opening 3.
An opening 5 is formed, and this second opening 5 is closed by a gas-permeable diaphragm 6 made of Teflon (trade name) or the like and an oxygen permeable membrane 7 made of Teflon (trade name) or the like and capable of transmitting only oxygen gas. . The aforementioned diaphragm 6 and oxygen permeable membrane 7 collectively constitute a second permeable membrane 8, and this second permeable membrane 8 is in contact with the outside air. A porous first working electrode film 11 is attached to a part of the inner surface of the first permeable membrane 4 that is in contact with the electrolytic solution 2 . The first working electrode film 11 is made of a platinum metal such as platinum, palladium, or silidium, an alloy thereof, or an oxide of the above metal, and as a result, it is resistant to both the carbon monoxide gas and the hydrogen sulfide gas. Catalytic reaction occurs at room temperature.
Further, this first working electrode film 11 is adhered to the inner surface of the first permeable film 4 by thick film printing or the like. A second working electrode film 12 is attached to the inner surface of the first permeable film 4 adjacent to the first working electrode film 11 . The second working electrode film 12 is made of gold, silver, or oxides thereof, and is deposited by a method such as vapor deposition, sputtering, or ion plating. As a result, the second working electrode film 12 contains only one of the two gases.
The electrode reacts selectively with the other gas, that is, hydrogen sulfide gas. Note that the first working electrode film 11 and the second working electrode film 12 are formed by first coating the second working electrode film 12 on the entire inner surface of the first permeable film 4, and then applying the second working electrode film 12 to the entire inner surface of the first permeable film 4.
The first working electrode film 11 may be attached to a part of the working electrode film 12. In this case, the first working electrode film 11 is attached to the inner surface of the first permeable film 4 via the second working electrode film 12. A porous removal membrane 13 is attached to the outer surface of the first permeable membrane 4 and overlaps the first working electrode membrane 11 . This removal film 13 is made of platinum, palladium,
It is made of metal such as iridium, oxides of these metals, activated carbon, graphite, etc., and adsorbs and removes the other gas, that is, hydrogen sulfide gas. A porous counter electrode film 14 and a porous reference electrode film 15 are attached to the inner surface of the second permeable membrane 8 that is in contact with the electrolyte 2 . 21, 22, 23 have one end as the first
Working electrode membrane 11, counter electrode membrane 14, reference electrode membrane 15
The other ends of these lead wires 21, 22, and 23 are connected to a potentiostat 24, and a constant potential is applied to the first working electrode film 11. Also, 25, 26, 27
are lead wires with one end connected to the second working electrode film 12, counter electrode film 14, and reference electrode film 15, respectively, and the other ends of these lead wires 25, 26, 27 are connected to the potentiostat 28, A constant potential is applied to the second working electrode film 12.

Next, the operation of one embodiment of the present invention will be explained.

It is now assumed that the measurement gas mixed with carbon monoxide gas and hydrogen sulfide gas is being led to the first opening 3. At this time, the other gas in the measurement gas, that is, hydrogen sulfide gas, is adsorbed and removed by the removal film 13 when passing through the removal film 13. Since this removal film 13 overlaps the first working electrode film 11, only one gas, that is, carbon monoxide gas, passes through the first permeable film 4 and reaches the first working electrode film 11. do. The carbon monoxide gas that has reached the first working electrode film 11 causes an oxidation reaction at the interface between the first working electrode film 11 and the electrolytic solution 2 . On the other hand, the measurement gas passes through the first permeable membrane 4 and reaches the second working electrode membrane 12.
At the interface between 2 and electrolyte 2, the other gas,
That is, only hydrogen sulfate gas is selectively oxidized. On the other hand, oxygen gas in the atmosphere passes through the second permeable membrane 8 and causes a reduction reaction at the interface between the counter electrode membrane 14 and the electrolytic solution 2. As a result, the first working electrode film 1
An electrolytic current corresponding to the concentration of carbon monoxide gas flows between the electrode 1 and the counter electrode film 14, and the concentration of carbon monoxide gas is measured by detecting this electrolytic current. On the other hand, the second working electrode film 12 and the counter electrode film 14
An electrolytic current corresponding to the concentration of hydrogen sulfide gas flows between them, and the concentration of hydrogen sulfide gas is measured by detecting this electrolytic current. Here, the potential of the reference electrode membrane 15 accurately represents the resting potential of the counter electrode membrane 14 and is not affected by the gas to be measured. In this way, the concentrations of carbon monoxide gas and hydrogen sulfide gas are measured individually and simultaneously.

In addition, in the above-mentioned embodiment, the case where the concentration of carbon monoxide gas and hydrogen sulfide gas was measured was explained, but in this invention, the concentration measurement of carbon monoxide gas and nitrogen oxide gas, carbon monoxide gas and sulfur oxide gas, It is also possible to measure concentrations such as Further, the first working electrode film 11 described above may be one of the gases,
That is, in the case of selectively reacting with carbon monoxide gas, the removal film 13 may not be provided. Furthermore, even if the first working electrode film 11 reacts with both gases and the second working electrode film 12 selectively reacts with the other gas, and the removal film 13 is omitted,
From the total electrolytic current obtained by measuring the concentrations of carbon monoxide gas and hydrogen sulfide gas flowing between the first working electrode membrane 11 and the counter electrode membrane 14, a microcomputer or the like is used to cancel the electrolytic current generated by the other gas. Then, the concentration of each gas can be measured simultaneously. Further, even if the removal film 13 is not provided, the first working electrode film 11
By individually setting the potential applied to the first working electrode membrane 12 and the potential applied to the second working electrode membrane 12 to appropriate values,
It is also possible to cause the working electrode film 11 to react selectively with one gas, and to make the second working electrode film 12 react selectively with the other gas. In addition, in the above-mentioned embodiment, the case where two types of gases are measured simultaneously was explained, but the first permeable membrane 4 has a working electrode film attached to the inner surface side and a removal film attached to the outer surface side. By adding one or more membrane units consisting of the following gases and measuring gases other than the two gases mentioned above, the concentrations of many types of gases can be measured simultaneously. Furthermore, in the above-mentioned embodiments, the case where the present invention was applied to a constant potential electrolysis type gas sensor was explained, but the present invention can also be applied to a galvanic cell type, polarographic type, coulometric type, and solution conductivity type gas sensor. be able to.

Effects of the Invention As explained above, according to the present invention, the measuring device as a whole becomes smaller in size, has a simpler structure, and can be manufactured at a lower cost. Moreover, when a measurement error occurs, it becomes easy to know what the cause is.

[Brief explanation of drawings]

The drawing is a schematic sectional view showing an embodiment of the present invention. 1... Container, 2... Electrolyte, 3... First opening,
4...First permeable membrane, 5...Second opening, 8...Second
Permeable membrane, 11...first working electrode membrane, 12...second
Working electrode film, 13... Removal film, 14... Counter electrode film.

Claims (1)

[Scope of Claims] 1. A container containing an electrolytic solution, a gas-permeable first permeable membrane that closes a first opening formed in the container and is in contact with a measurement gas mixed with two types of gases, and a container. a gas-permeable second permeable membrane that closes a second opening formed in the first permeable membrane and is in contact with the outside air; and a first working electrode membrane that is adhered to the inner surface of the first permeable membrane that is in contact with the electrolyte and that reacts with at least one of the gases. , a second working electrode film that is deposited on the inner surface of the first permeable membrane and reacts with the other gas;
a counter electrode film adhered to the inner surface of the permeable membrane that is in contact with the electrolytic solution; An electrochemical gas sensor characterized in that gas concentration is simultaneously measured by detecting the generated output. 2. A container containing an electrolytic solution, a gas-permeable first permeable membrane that closes a first opening formed in the container and is in contact with a measurement gas mixed with two types of gases, and a second gas-permeable membrane formed in the container. a gas-permeable second permeable membrane that closes the opening and is in contact with the outside air; a first working electrode membrane that is coated on the inner surface of the first permeable membrane that is in contact with the electrolytic solution and that reacts with at least one of the gases; a second working electrode film deposited on the inner surface and reacting with the other gas;
A porous removal membrane is attached to the outer surface of the permeable membrane so as to overlap with the first working electrode membrane and removes the other gas, and a counter electrode membrane is attached to the inner surface of the second permeable membrane that is in contact with the electrolyte. The gas concentration is simultaneously measured by detecting the output generated between the first working electrode film and the counter electrode film and between the second working electrode film and the counter electrode film according to the concentration of each gas. Electrochemical gas sensor.