JP7052549B2 - Redox reaction electrodes and fuel cells - Google Patents

Description

The present invention relates to an electrode for a redox reaction and a fuel cell using the same.

In the electrolyte used in polymer electrolyte fuel cells, water (H ₂ O) acts as a carrier to move protons (H ⁺ ) from the anode to the cathode, and the cathode reacts with protons (H ⁺ ) and oxygen (O ₂ ). To generate water (H ₂ O). Therefore, the polymer electrolyte fuel cell can be used only in the temperature range in which water can exist in the electrolyte, that is, below 100 ° C. When the operating temperature of the fuel cell is low, the activity of the Pt catalyst becomes low, which causes an increase in the amount of Pt in order to maintain the power generation performance. In addition, a large radiator for cooling the fuel cell and a unit for controlling the humidity of the electrolyte membrane are also required. Due to these factors, it is unavoidable to increase the cost of polymer electrolyte fuel cells.

Therefore, in Patent Document 1, it is proposed to use a mixture of a binder, a Pt catalyst, and H ₃ PO ₄ as a fuel cell electrode and H ₃ PO ₄ as a proton carrier. In this electrode, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polybenzimidazole, polyetherketone, polyetherimide, polysulfone or perfluorosulfonic acid are used as binders, and H is used after the electrode is completed. ₃ Doping PO ₄ .

Japanese Unexamined Patent Publication No. 2006-142293

However, when H ₃ PO ₄ is used as a proton carrier, the proton supply to the Pt catalyst is low. Further, at the cathode electrode, H ₃ PO ₄ is adsorbed on Pt and the catalytic activity is lowered. Furthermore, since H ₃ PO ₄ exudes from the binder over time, the ionic conductivity decreases and the catalytic activity decreases. From these facts, when H ₃ PO ₄ is used as a proton carrier, the oxygen reduction performance of the electrode is lowered.

In view of the above points, it is an object of the present invention to improve the redox performance of the redox reaction electrode having proton conductivity.

In order to achieve the above object, in the inventions according to claims 1 and 4 , the catalyst carrier (200), the Pt catalyst (201) supported on the catalyst carrier, and the ionoma (131b) having proton conductivity are used. The ionoma contains H ₄ PO ₄ ⁺ .
The invention according to claim 1 is characterized in that the peak shift δ of ³¹ P-NMR is 0.5 ppm or more.
In the invention according to claim 4, the ionoma contains a strong acid having a higher acidity than H ₃ PO ₄ , and the molar ratio of phosphoric acid to the strong acid in the ionoma is 1 or less.

Compared with H ₃ PO ₄ , H ₄ PO ₄ ⁺ contained in ionomer has a higher proton supply property to the Pt catalyst, is less likely to be adsorbed to the Pt catalyst, and can suppress a decrease in catalytic activity. Therefore, in the redox electrode of the present invention, the redox performance can be improved as compared with the case where H ₃ PO ₄ is used as the proton carrier.

The reference numerals in parentheses of each of the above components indicate the correspondence with the specific means described in the embodiments described later.

It is a conceptual diagram which shows the fuel cell of an embodiment of this invention. It is an enlarged view of a part of a catalyst layer. It is a figure which shows the proton carrier of Examples 1 and 2 and Comparative Examples 1 and 3. It is a figure which shows the NMR spectrum of the electrolytic solution of Example 1 and Comparative Example 1. FIG. It is a figure which shows the cyclic voltammogram of Example 1 and Comparative Example 1. It is a figure which shows the cyclic voltammogram of Example 2 and Comparative Example 2. It is a figure which shows the cyclic voltammogram of Example 2 and Comparative Example 3. It is a chart which shows the redox performance of Examples 1 and 2 and Comparative Examples 1 and 3. 6 is a graph showing the relationship between the molar ratio of H ₃ PO ₄ to the strong acid of Examples 3 to 6 and Comparative Example 4 and the chemical shift measured by NMR. It is a chart which shows the redox performance of Examples 3-6 and Comparative Example 4.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, the redox reaction electrode of the present invention is applied to a fuel cell electrode.

As shown in FIG. 1, the fuel cell 100 includes an electrolyte membrane 110 and a pair of electrodes 120 and 130 that sandwich the electrolyte membrane 110. The pair of electrodes 120 and 130 are composed of an anode electrode 120 and a cathode electrode 130. The anode electrode 120 is also referred to as a hydrogen electrode, and the cathode electrode 130 is also referred to as an air electrode. The cathode electrode 130 corresponds to the redox reaction electrode of the present invention, and the fuel cell 100 corresponds to the fuel cell of the present invention.

The fuel cell 100 outputs electric energy by utilizing an electrochemical reaction between hydrogen and oxygen in the air. The fuel cell 100 is used as a basic unit, and it can be used as a stack structure in which a plurality of cells are stacked. Hydrogen is the fuel gas and oxygen in the air is the oxidant gas.

When hydrogen is supplied to the anode pole 120 and air is supplied to the cathode pole 130, hydrogen and oxygen undergo an electrochemical reaction as shown below to output electrical energy.

(Anode pole side) H ₂ → 2H ⁺ + ^2e-
(Cathode pole side) 2H ⁺ + 1 / 2O ₂ + ^2e- → H ₂ O
At this time, at the anode electrode 120, hydrogen is ionized into an electron (e ⁻ ) and a proton (H ⁺ ) by a catalytic reaction, and the proton moves through the electrolyte membrane 110. On the other hand, in the cathode electrode 130, water (H ₂ O) is generated from the protons that have moved from the anode electrode 120 side, the electrons that have flowed from the outside, and the oxygen (O ₂ ) in the air by the catalytic reaction. ..

The fuel cell 100 of the present embodiment generates electricity without humidifying the electrolyte membrane 110. That is, during the operation of the fuel cell 100, dry air is supplied to the cathode electrode 130. Therefore, the fuel cell 100 can generate electricity at a temperature of 100 ° C. or higher.

The electrolyte membrane 110 is composed of a proton conductor containing a metal ion, an oxo anion, and a proton-coordinating molecule. In the proton conductor, at least one of an oxo anion and a proton-coordinating molecule coordinates with a metal ion to form a coordination polymer.

The metal ion contained in the proton conductor is not particularly limited, but is a high-period transition metal ion or a typical one from the viewpoint of easiness of forming a coordinate bond with an oxoanion and / or a proton-coordinating molecule. Metal ions are preferred. Of these, cobalt ions, copper ions, zinc ions, and gallium ions are preferable. In the electrolyte membrane 110 of the present embodiment, zinc ions are used as metal ions.

Examples of the oxo anion contained in the proton conductor include phosphate ion, sulfate ion and the like, but phosphate ion is preferable from the viewpoint of chemical stability to hydrogen. In the electrolyte membrane 110 of the present embodiment, a phosphate ion is used as an oxo anion.

The proton-coordinating molecule contained in the proton conductor is preferably a molecule having two or more coordination points for coordinating protons in the molecule. From the viewpoint of ion conductivity, imidazole, triazole, benzimidazole, benztriazole, and derivatives thereof having an excellent coordination point in the balance between proton coordination and release are preferable. In the electrolyte membrane 110 of the present embodiment, triazole is used as the proton-coordinating molecule.

The anode electrode 120 includes an anode-side catalyst layer 121 arranged in close contact with the anode-side surface of the electrolyte membrane 110, and an anode-side diffusion layer 122 arranged outside the anode-side catalyst layer 121. The cathode electrode 130 includes a cathode side catalyst layer 131 arranged in close contact with the cathode side surface of the electrolyte membrane 110, and a cathode side diffusion layer 132 arranged outside the cathode side catalyst layer 131.

As shown in FIG. 2, the catalyst layers 121 and 131 include catalyst-supported carbons 121a and 131a and ionomers 121b and 131b that coat the catalyst-supported carbons 121a and 131a. The catalyst-supported carbons 121a and 131a are composed of a carbon carrier 200 and Pt particles 201 supported on the carbon carrier 200. The carbon carrier 200 is a catalyst carrier and uses fine carbon powder called carbon black. The Pt particles 201 are catalysts that promote an electrochemical reaction and are supported on the surface of the carbon carrier 200. Ionomers 121b and 131b are proton conductors and contain a polymer as a binder and a proton carrier which is a proton conductive substance. The diffusion layers 122 and 132 are made of carbon cloth or the like.

Here, a method for manufacturing the electrodes 120 and 130 will be described. First, particulate catalyst-supported carbons 121a and 131a and ionomers 121b and 131b (polymer, proton carrier) are mixed with a solvent such as ethanol to form ink. This is applied onto the carbon cloth constituting the diffusion layers 122 and 132 and dried. Thereby, the catalyst layers 121 and 131 and the diffusion layers 122 and 132 constituting the electrodes 120 and 130 can be obtained.

H ₃ PO ₄ can be used as the proton carrier contained in the anode-side ionomer 121b. Further, as the polymer contained in the anode side ionoma 121b, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polybenzoimidazole, polyetherketone, polyetherimide, polysulfone, perfluorosulfonic acid and the like should be used. Can be done.

In this embodiment, H ₄ PO ₄ ⁺ is used as the proton carrier contained in the cathode side ionomer 131b. In the process of forming the cathode-side catalyst layer 131, H 3 PO 4 receives H + from the strong acid and H _{3 PO 4 receives H + from the strong acid by coexisting H 3 PO 4} ^and _{a strong acid having a higher acidity than H 3 PO 4 in} the solvent. ₄ PO ₄ ⁺ is generated. In order to increase the production rate of H ₄ PO ₄ ⁺ as much as possible, it is desirable that the molar ratio of phosphoric acid to strong acid is 1 or less.

Here, the phosphoric acid in the present specification mainly contains H ₃ PO ₄ and H ₄ PO ₄ ⁺ in which H ⁺ is bound to H ₃ PO ₄ . That is, in the step of forming the cathode side catalyst layer 131, it is sufficient that the molar ratio of H ₃ PO ₄ to the strong acid is 1 or more, and after the cathode side catalyst layer 131 is formed (that is, H ₄ PO ₄ ^+). After the formation of), the total molar ratio of H ₄ PO ₄ ⁺ and H ₃ PO ₄ to the strong acid should be 1 or more. The number of moles of strong acid also includes ions of strong acid that released H ⁺ .

As the polymer contained in the cathode side ionomer 131b, a strongly acidic polymer can be used. The strong acid polymer is a polymer as a binder and is a strong acid for producing H ₄ PO ₄ ⁺ . As the strongly acidic polymer, a polymer having a sulfone group can be preferably used. Examples of the polymer having a sulfone group include a perfluorosulfonic acid polymer, a sulfonated polyether ether ketone, and a polymer having a sulfonated acetylene skeleton.

In addition, instead of the strongly acidic polymer, among the strong acids such as sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, trifluoromethanesulfonic acid and 1,1,1-trifluoro-N-[(trifluoromethyl) sulfonyl] methanesulfonic acid. One or more acids and a polymer can be used in combination. In this case, one type of strong acid may be used alone, or a plurality of types of strong acids may be used in combination. Also, the polymer used in combination with a strong acid does not have to be a strong acid.

H ₄ PO ₄ ⁺ contained in the cathode side ionomer 131b has a high proton supply property to the Pt catalyst. Further, since H ₄ PO ₄ ⁺ is difficult to be adsorbed on Pt at the cathode potential in the operating range of the fuel cell 100, it is possible to suppress the decrease in the active site of the Pt catalyst.

When a strongly acidic polymer having a sulfone group is used, H ₄ PO ₄₊ and the sulfone group of the strongly acidic polymer are strongly bonded by ionic bonds ^. Therefore, even if the fuel cell 100 is used for a long period of time, there is an advantage that H ₄ PO ₄ ⁺ is difficult to elute from the cathode electrode 130.

Next, the redox efficiency of the cathode electrode 130 of this embodiment will be described with reference to Examples 1 and 2 and Comparative Examples 1 to 3. The evaluation of the oxygen reduction reaction activity was performed using a rotating disk electrode. In the rotating disk electrode, a Pt plate (electrode area: 0.196 cm ² ) was used as the working electrode, a Pt wire was used as the counter electrode, and a standard hydrogen electrode (SHE) was used as the reference electrode. As the electrolytic solution, 1-Butyl-1-methylpyrrolidinium Bis (trifluoromethanesulfonyl) imide was used. The electrode rotation speed was 400 rpm, and the cell temperature was 100 ° C.

As shown in FIG. 3, in Examples 1 and 2 and Comparative Examples 1 to 3, the types and amounts of proton carriers added to the electrolytic solution are different. Examples 1 and 2 used H ₄ PO ₄ ⁺ as the proton carrier, Comparative Examples 1 and 2 used H ₃ PO ₄ as the proton carrier, and Comparative Example 3 used H ₂ O as the proton carrier. In Examples 1 and 2, H ₄ PO ₄ ⁺ was generated by coexisting H ₃ PO ₄ and a strong acid in the electrolytic solution. Trifluoromethanesulfonic acid (CF ₃ SO ₃ H) was used as the strong acid.

In Example 1, 10 mM H ₃ PO ₄ and 10 mM strong acid were added to the electrolytic solution to generate H ₄ PO ₄ ⁺ . In Example 2, 100 mM H ₃ PO ₄ and 100 mM strong acid were added to the electrolytic solution to generate H ₄ PO ₄ ⁺ . In Comparative Example 1, 10 mM H ₃ PO ₄ was added to the electrolytic solution. In Comparative Example 2, 100 mM H ₃ PO ₄ was added to the electrolytic solution. In Comparative Example 3, 100 mM H ₂ O was added to the electrolytic solution.

Here, the production rate of H ₄ PO ₄ ⁺ of Example 1 will be described with reference to FIG. In Example 1, H ₄ PO ₄ ⁺ and H ₃ PO ₄ are present in the electrolyte, and in Comparative Example 1, only H ₃ PO ₄ is present in the electrolyte. As shown in FIG. 4, in the NMR spectrum of Example 1, the peak of the chemical shift is shifted to the left low magnetic field side with respect to the NMR spectrum of Comparative Example 1 corresponding to H ₃ PO ₄ . This indicates that H ₄ PO ₄ ⁺ is produced in Example 1 in which H ₃ PO ₄ and a strong acid are mixed.

Next, the results of evaluating the oxygen reduction reaction activities of Examples 1 and 2 and Comparative Examples 1 to 3 will be described with reference to FIGS. 5 to 7. 5 to 7 show that the potential is 10 mV / sec. From 1.12 V (vs. SHE) to 0 V (vs. SHE) by the electrochemical measuring device. It is swept at the speed of, and the change of the current value that flowed at that time is shown.

As shown in FIG. 5, in Example 1 (100 mM H ₄ PO ₄ ⁺ ), the current starts to flow earlier than in Comparative Example 1 (100 mM H ₃ PO ₄ ). From this, it can be seen that in Example 1, the oxidation reaction (that is, the reaction for producing H ₂ O at the cathode electrode 130) is promoted as compared with Comparative Example 1, and the proton supply property to the Pt catalyst is high.

As shown in FIG. 6, in Example 2 (10 mM H ₄ PO ₄ ⁺ ), the current starts to flow earlier than in Comparative Example 2 (10 mM H ₃ PO ₄ ). From this, it can be seen that in Example 2, the oxidation reaction is promoted as compared with Comparative Example 2, and the proton supply to the Pt catalyst is high.

As shown in FIG. 7, in Example 1 (100 mM H ₄ PO ₄ ⁺ ), the current starts to flow earlier than in Comparative Example 3 (100 mM H ₂ O). From this, it can be seen that in Example 1, the oxidation reaction is promoted as compared with Comparative Example 3, and the proton supply to the Pt catalyst is high.

Next, the results of evaluation of the oxygen reduction reaction activity of Examples 1 and 2 and Comparative Examples 1 to 3 will be described with reference to FIG. The Tafel slope and exchange current density shown in FIG. 8 were calculated from the current densities at 0.6 V of each of the Examples and Comparative Examples shown in FIGS. 5 to 7.

The exchange current density is the current when the chemical reaction occurring at the cathode pole 130 is in equilibrium. It can be said that the higher the exchange current density, the easier the current flows and the higher the redox performance.

As shown in FIG. 8, Example 1 (100 mM H ₄ PO ₄ ⁺ ) has a higher exchange current density than Comparative Example 1 (100 mM H ₃ PO ₄ ). Further, in Example 1, the exchange current density equivalent to that of Comparative Example 3 in which H ₂ O is used as the proton carrier is obtained. Further, Example 2 (10 mM H ₄ PO ₄ ⁺ ) has a higher exchange current density than Comparative Example 2 (10 mM H ₃ PO ₄ ). That is, when H ₄ PO ₄ ⁺ is used as the proton carrier, the redox performance is improved as compared with the case where H ₃ PO ₄ is used as the proton carrier.

Next, the production rate of H ₄ PO ₄ ⁺ when the cathode electrode 130 is formed by changing the molar ratio of H ₃ PO ₄ to the strong acid will be described with reference to Examples 3 to 6 and Comparative Example 4. In Examples 3 to 6 and Comparative Example 4, Nafion (a registered trademark of DuPont), which is a perfluorosulfonic acid polymer, was used as a strong acid.

In Examples 3 to 6 and Comparative Example 4, the molar ratio of H ₃ PO ₄ to nafion (that is, the molar ratio of phosphoric acid to strong acid) is different from each other. The molar ratio of H ₃ PO ₄ to Nafion was 0.5 for Example 3, 1.0 for Example 4, 2.0 for Example 5, 3.2 for Example 6, and 3.5 for Comparative Example 4. It is supposed to be.

In Example 3, 0.2 g of Pt (46.5 wt%) / C powder, 1.22 ml of 5% Nafion solution, 8.56 ml of ethanol, 0.96 ml of water, and 8. of 85% H ₃ PO ₄ . 07 ml was weighed and dispersed and mixed with an ultrasonic homogenizer to prepare an electrode ink. In Examples 4 to 6 and Comparative Example 4, the amount of H ₃ PO ₄ was different from that of Example 3 so that the molar ratio of H ₃ PO ₄ to Nafion described above was adjusted.

The electrode inks of Examples 3 to 6 and Comparative Example 4 prepared with the above composition were applied to a carbon cloth or the like by a spray method so that the amount of Pt carried was 0.3 mg / cm ² , and the applied electrodes were collected. , ³¹ P-NMR (phosphorus 31 nuclear magnetic resonance spectroscopy) was used to analyze ³¹ P. The NMR measurement sample was added so that KBr was 5 wt% with respect to the electrode powder, and the sample was sealed in a sample tube. In the NMR measurement, 0 ppm of 85% H ₃ PO ₄ was used as a reference.

In FIG. 9, the horizontal axis is the molar ratio of H ₃ PO ₄ to Nafion, and the vertical axis is the chemical shift δ measured by ³¹ P-NMR. In FIG. 9, the white circles indicate Examples 3 to 6, the white triangles indicate Comparative Example 4, and the white squares indicate the points where the abundance ratio of H ₄ PO ₄ ⁺ is 100%. ..

As shown in FIG. 9, the value of the chemical shift δ of ³¹ P-NMR is 3.2 ppm in Example 3, 3.0 ppm in Example 4, 1.7 ppm in Example 5, and 0.5 ppm in Example 6. In Comparative Example 4, it is 0.3 ppm. That is, the value of the chemical shift δ of ³¹ P-NMR is inversely proportional to the molar ratio of H ₃ PO ₄ to Nafion.

Here, the molar ratio of H ₃ PO ₄ to Nafion and the abundance ratio of H ₄ PO ₄ ⁺ will be described. "Yoshitaka Hisazumi, et. Al.," Determination of the association constants of H ₄ PO ₄ ⁺ HSO ₄ ^--31 P NMR and cation-exchange methods ", J. ^inorg . Nucl. Chem., Vol.39, pp1615-1619 According to "(1977).", The chemical shift amount of ³¹ P-NMR is 3.8 ppm when the abundance ratio of H ₄ PO ₄ ⁺ is 100%. Further, when the abundance ratio of H ₄ PO ₄ ⁺ is 0%, the chemical shift amount of ³¹ P-NMR is 0 ppm. That is, the larger the value of the chemical shift δ, the higher the abundance ratio of H ₄ PO ₄ ⁺ .

As shown in FIG. 9, as the molar ratio of H ₃ PO ₄ to nafion decreases, the abundance ratio of H ₄ PO ₄ ⁺ increases linearly. In Comparative Example 4 in which the molar ratio of H ₃ PO ₄ to Nafion is 3.5, it is estimated that the value of the chemical shift σ is 0.3 ppm and the abundance ratio of H ₄ PO ₄ ⁺ is about 7%.

On the other hand, in Examples 3 to 6 in which the molar ratio of H ₃ PO ₄ to Nafion is 3.2 or less, the value of the chemical shift σ of ³¹ P is 0.5 ppm or more, and the presence of H ₄ PO ₄ ⁺ is present. It is estimated that the ratio is 15% or more. In particular, in Examples 3 and 4 in which the molar ratio of H ₃ PO ₄ to Nafion is 1.0 or less, the value of the chemical shift σ of ³¹ P is 3.0 ppm or more, and the abundance ratio of H ₄ PO ₄ ⁺ is 75. It is estimated to be more than%. Therefore, it is desirable that the value of the chemical shift σ of ³¹ P is 0.5 ppm or more, and it is desirable that the molar ratio of H ₃ PO ₄ to Nafion is 3.2 or less. Further, it is more desirable that the value of the chemical shift σ of ³¹ P is 3.0 ppm or more, and it is more desirable that the molar ratio of H ₃ PO ₄ to Nafion is 1.0 or less.

Next, the electrodes of Examples 3 to 6 and Comparative Example 4 were attached to the electrolyte membrane to prepare an electrolyte electrode junction (MEA), and the exchange current density of the MEA was derived.

Place a 15 mm square hydrophilized Teflon (registered trademark) membrane filter (manufactured by Merck Millipore) on a Teflon (registered trademark) plate, fix the four corners with tape, and add 50 mg of coordination polymer powder to the membrane filter in 3 ml of water. An electrolyte membrane was prepared by applying the electrolyte membrane raw material solution dispersed in the above. The electrolyte membrane raw material solution was applied until the supported amount of the coordination polymer powder became 1 mg / 2.25 cm ² by spray application. The electrodes prepared in Examples 3 to 6 and Comparative Example 4 were attached to both sides of the obtained electrolyte membrane to prepare MEA.

Next, heat to 120 ° C. while supplying 3.8% hydrogen to one electrode of MEA and dry air to the other electrode at a flow rate of 60 mL / min, and after the temperature stabilizes, 0.6 V from the open circuit voltage. The battery performance was evaluated by sweeping up to 0.2 mV / sec. The obtained cyclic voltamogram was fitted using the Butler-Volmer equation with the exchange current density and the Tafel slope as variables, and the exchange current density, which is an index of the oxygen reduction reaction activity, was derived.

As shown in FIG. 10, the smaller the molar ratio of H ₃ PO ₄ to Nafion, the higher the exchange current density. That is, it is considered that the smaller the molar ratio of H ₃ PO ₄ to Nafion, the higher the abundance ratio of H ₄ PO ₄ ⁺ , and as a result, the higher the redox performance.

In the present embodiment described above, H ₄ PO ₄₊ is used as the proton carrier of the cathode side ionomer 131b in the cathode electrode 130 of the fuel cell 100 ^. H ₄ PO ₄ ⁺ has a higher proton supply property to the Pt catalyst than H ₃ PO ₄ . Further, since H ₄ PO ₄ ⁺ is difficult to be adsorbed on the Pt catalyst at the cathode potential in the operating range of the fuel cell 100, it is possible to suppress a decrease in catalytic activity. Therefore, in the cathode electrode 130 of the present embodiment, the redox performance can be improved as compared with the case where H ₃ PO ₄ is used as the proton carrier.

Further, when a strongly acidic polymer having a sulfone group is used for the cathode side ionoma 131b, H ₄ PO ₄ ⁺ is strongly bonded to the sulfone group of the strongly acidic polymer by an ionic bond. Therefore, even if the fuel cell 100 is used for a long period of time, it is difficult for H ₄ PO ₄ ⁺ to elute from the cathode electrode 130. Also by this, the cathode electrode 130 of the present embodiment can improve the redox performance.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and can be variously modified as follows without departing from the spirit of the present invention. In addition, the means disclosed in each of the above embodiments may be appropriately combined to the extent feasible.

(1) In the above embodiment, an example in which the redox reaction electrode of the present invention is applied to the fuel cell electrode has been described, but the present invention is not limited to this, and the redox reaction electrode of the present invention conducts protons to oxidize. Any electrode for carrying out a reduction reaction can be applied.

(2) In the above embodiment, the catalyst-supported carbon 131a is covered with the ionomer 131b, but it is not always necessary to cover the catalyst-supported carbon 131a with the ionomer 131b, and for example, a liquid ionoma may be used.

(3) In the above embodiment, an example in which a coordination polymer is used as the electrolyte membrane 110 has been described, but the type of the electrolyte membrane 110 is not limited to this, and a different type of electrolyte membrane 110 may be used. can.

(4) In the above embodiment, the anode pole 120 has a different configuration from the cathode pole 130, but the present invention is not limited to this, and the anode pole 120 may have the same configuration as the cathode pole 130. That is, the redox reaction electrode of the present invention may be applied to the anode electrode 120, and the proton carrier of the anode-side ionoma 121b may be H ₄ PO ₄ ⁺ .

100 fuel cell (fuel cell)
110 Electrolyte membrane 120 Anode pole 130 Cathode pole (Redox reaction electrode)
131 Cathode side catalyst layer 131a Catalyst-supported carbon 131b Ionoma 132 Cathode side diffusion layer 200 Carbon carrier (catalyst carrier)
201 Pt particles (Pt catalyst)

Claims (9)

It comprises a catalyst carrier (200), a Pt catalyst (201) supported on the catalyst carrier, and an ionomer (131b) having proton conductivity.
The ionomer contains H ₄ PO ₄ ⁺ and
³¹ An electrode for redox reaction in which the peak shift δ of P-NMR is 0.5 ppm or more . The redox reaction electrode according to claim 1 , wherein the ionomer contains a strong acid having a higher acidity than H ₃ PO ₄ . The electrode for redox reaction according to claim 2 , wherein the molar ratio of phosphoric acid to the strong acid in the ionoma is 1 or less. It comprises a catalyst carrier (200), a Pt catalyst (201) supported on the catalyst carrier, and an ionomer (131b) having proton conductivity.
The ionomer contains H ₄ PO ₄ ⁺ and
The ionomer contains a strong acid that is more acidic than H ₃ PO ₄ .
An electrode for a redox reaction in which the molar ratio of phosphoric acid to the strong acid in the ionoma is 1 or less . The electrode for a redox reaction according to any one of claims 2 to 4 , wherein the strong acid is a strongly acidic polymer having a sulfone group. The strong acid is one or more of sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, trifluoromethanesulfonic acid and 1,1,1-trifluoro-N-[(trifluoromethyl) sulfonyl] methanesulfonic acid. The electrode for an oxidation-reduction reaction according to any one of claims 2 to 4 . The electrode for redox reaction according to any one of claims 1 to 6, which is used in a fuel cell for generating electric energy by electrochemically reacting a fuel gas and an oxidant gas. The electrode for redox reaction according to claim 7, to which the oxidant gas is supplied. The redox reaction electrode (130) according to any one of claims 1 to 8.
A fuel cell including an electrolyte (110) arranged so as to be in contact with the redox reaction electrode.

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