Solid polymer fuel cells

Abstract

To provide a polymer electrolyte fuel cell, capable of suppressing the deterioration of a solid polymer electrolyte caused by hydrogen peroxides and radicals.SOLUTION: A polymer electrolyte fuel cell includes: (A) a tungsten compound A added to an anode catalyst layer and / or a tungsten compound B added to a cathode catalyst layer; and (B) one or more selected from the group consisting of Ce ions added to an electrolyte membrane, a Ce compound A added to the electrolyte membrane, a Ce compound B added to a water repellent layer of an anode gas diffusion layer, and a Ce compound C added to a water repellent layer of a cathode gas diffusion layer. Each of the tungsten compound A and the tungsten compound B has a composition represented by composition formula: WOx-nH2O (2≤x≤3, 0≤n≤3, and x and n each include a non-integer).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polymer electrolyte fuel cell, and more particularly to a polymer electrolyte fuel cell containing an additive that has the effect of suppressing the degradation of the polymer electrolyte. [Background technology]

[0002] Membrane electrode assemblies (MEAs) are used in soda electrolysis equipment, water electrolysis equipment, fuel cells, and other devices where electrochemical reactions occur. It is said that MEAs are susceptible to degradation due to the attack of electrolytes by radicals directly generated by the direct reaction of oxygen and hydrogen or by electrochemical reactions, or by radicals generated via hydrogen peroxide. For example, in fuel cells, radical attack is known to cause increased resistance of the electrolyte membrane, increased cross-leakage, and shortened lifespan due to thinning of the membrane. Furthermore, degradation products generated by radical attack can cause catalyst poisoning, potentially reducing electrolytic performance and battery performance.

[0003] Therefore, various proposals have been made to solve this problem. For example, Patent Document 1 contains: (a) A catalyst ink in which 0.25 times the number of moles of H2WO4 and 0.05 times the number of moles of Ce(NO3)3 are added relative to the number of moles of sulfonic acid groups in Nafion®, (b) Catalyst ink prepared by adding 0.25 moles of H2WO4 and 0.05 moles of Mn(NO3)3 relative to the number of moles of sulfonic acid groups in Nafion®. A MEA prepared using [the specified method] is disclosed. The document states that MEA prepared using catalyst inks containing degradation inhibitors (H2WO4, Ce(NO3)3, Mn(NO3)3) has a higher molecular weight retention rate of the solid polymer electrolyte compared to MEA prepared using catalyst inks that do not contain degradation inhibitors.

[0004] Patent Document 2 discloses a polymer electrolyte membrane containing a perfluorosulfonic acid resin and zirconia with a primary particle diameter of 10 nm, and the ratio of the mass (A) of the perfluorosulfonic acid resin to the mass (B) of zirconia (= A / B ratio) is 99 / 1. This document also describes (A) When adding zirconia that catalytically decomposes hydrogen peroxide to a perfluorosulfonic acid resin, if the primary particle diameter of zirconia is adjusted to 1 nm to 50 nm, the specific surface area of zirconia increases, and the hydrogen peroxide decomposition reaction points increase dramatically, and (B) thereby, the deterioration of the polymer electrolyte membrane is suppressed. These are described.

[0005] Furthermore, Patent Document 3 discloses (a) An electrolyte membrane made of Nafion (registered trademark) is immersed in a 0.1 M aqueous sodium tungstate solution at 90 °C for 30 minutes, (b) then, the electrolyte membrane is taken out of the aqueous solution and washed with water, (c) and further, the electrolyte membrane is immersed in 0.5 M sulfuric acid at 90 °C for 30 minutes. The resulting transition metal oxide-containing solid polymer electrolyte membrane is disclosed. This document also describes (A) By such a method, a transition metal oxide-containing solid polymer electrolyte membrane containing 2 wt% of tungsten oxide hydrate can be obtained, and (B) the electrolyte membrane containing tungsten oxide hydrate has a lower fluorine elution rate compared to the electrolyte membrane not containing tungsten oxide hydrate. These are described.

[0006] As described in Patent Documents 1 to 3, when adding certain deterioration inhibitors to a solid polymer electrolyte, the durability of the solid polymer electrolyte is improved. This is considered to be because certain deterioration inhibitors have the effect of decomposing hydrogen peroxide or eliminating radicals. However, even when a degradation inhibitor that has the effect of decomposing hydrogen peroxide and / or scavenging radicals was added to the solid polymer electrolyte, the degradation of the solid polymer electrolyte could not be sufficiently suppressed. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 5194448 [Patent Document 2] Patent No. 5354935 [Patent Document 3] Patent No. 4326271 [Overview of the project] [Problems that the invention aims to solve]

[0008] The problem that this invention aims to solve is to provide a polymer electrolyte fuel cell that can suppress the degradation of the polymer electrolyte caused by hydrogen peroxide and radicals. [Means for solving the problem]

[0009] To solve the above problems, the polymer electrolyte fuel cell according to the present invention has the following configuration. (1) The polymer electrolyte fuel cell is An electrolyte membrane containing a solid polymer electrolyte, an anode catalyst layer bonded to one side of the electrolyte membrane, A cathode catalyst layer bonded to the other side of the electrolyte membrane, An anode gas diffusion layer is disposed outside the anode catalyst layer, A cathode gas diffusion layer is disposed on the outside of the cathode catalyst layer. It is equipped with. (2) The polymer electrolyte fuel cell is (A) Tungsten compound A added to the anode catalyst layer, and / or tungsten compound B added to the cathode catalyst layer, (B) One or more selected from the group consisting of Ce ions added to the electrolyte membrane, Ce compound A added to the electrolyte membrane, Ce compound B added to the water-repellent layer of the anode gas diffusion layer, and Ce compound C added to the water-repellent layer of the cathode gas diffusion layer. Includes. (3) The tungsten compound A and the tungsten compound B each have the following compositional formula: WO x It has a composition represented by nH2O (where 2≦x≦3, 0≦n≦3, and x and n each include non-integers). [Effects of the Invention]

[0010] Certain tungsten compounds have the effect of decomposing hydrogen peroxide. Furthermore, Ce ions and Ce compounds have the effect of scavenging radicals. Therefore, adding both tungsten compounds and Ce ions or Ce compounds to a solid polymer electrolyte can suppress the degradation of the solid polymer electrolyte caused by hydrogen peroxide and radicals. However, for example, when both tungsten compounds and Ce ions are added to the electrolyte membrane simultaneously, the degradation suppression effect may be insufficient.

[0011] In contrast, when a tungsten compound is added to the catalyst layer and Ce ions or Ce compounds are added to a component other than the catalyst layer (e.g., the electrolyte membrane), the degradation of the solid polymer electrolyte may be suppressed compared to when these are added to the same component (e.g., the electrolyte membrane). [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows the relationship between the WO3·H2O content and the normalized total F-elution amount. [Figure 2] This figure shows the normalized total F-elution amount of the cells obtained in Example 2 and Comparative Example 2. [Figure 3] This figure shows the relationship between the WO3·H2O content and the normalized current density at 60°C, 80%RH, and 0.6V before and after the voltage fluctuation endurance test (82°C, 30%RH). [Modes for carrying out the invention]

[0013] One embodiment of the present invention will be described in detail below. [1. Polymer electrolyte fuel cell] The polymer electrolyte fuel cell according to the present invention has the following configuration.

[0014] [Configuration 1] A polymer electrolyte fuel cell with the following configuration. (1) The polymer electrolyte fuel cell is An electrolyte membrane containing a solid polymer electrolyte, an anode catalyst layer bonded to one side of the electrolyte membrane, A cathode catalyst layer bonded to the other side of the electrolyte membrane, An anode gas diffusion layer is disposed outside the anode catalyst layer, A cathode gas diffusion layer is disposed on the outside of the cathode catalyst layer. It is equipped with. (2) The polymer electrolyte fuel cell is (A) Tungsten compound A added to the anode catalyst layer, and / or tungsten compound B added to the cathode catalyst layer, (B) One or more selected from the group consisting of Ce ions added to the electrolyte membrane, Ce compound A added to the electrolyte membrane, Ce compound B added to the water-repellent layer of the anode gas diffusion layer, and Ce compound C added to the water-repellent layer of the cathode gas diffusion layer. Includes. (3) The tungsten compound A and the tungsten compound B each have the following compositional formula: WO x It has a composition represented by nH2O (where 2≦x≦3, 0≦n≦3, and x and n each include non-integers).

[0015] [Configuration 2] The tungsten compound A mentioned above, One or more selected from the group consisting of the Ce ion, the Ce compound A, and the Ce compound B A polymer electrolyte fuel cell as described in configuration 1, including the above.

[0016] [Configuration 3] The tungsten compound B mentioned above, One or more selected from the group consisting of the Ce ion, the Ce compound A, and the Ce compound C A polymer electrolyte fuel cell according to configuration 1 or 2, comprising the above.

[0017] [Structure 4] The anode catalyst layer contains the tungsten compound A, and the content of the tungsten compound A is 0.1 μg / cm³. 2 More than 50.0μg / cm 2 A polymer electrolyte fuel cell as described in any one of the following configurations 1 to 3.

[0018] [Composition 5] The cathode catalyst layer contains the tungsten compound B, and the content of the tungsten compound B is 0.1 μg / cm³. 2 More than 50.0μg / cm 2 A polymer electrolyte fuel cell as described in any one of the following configurations 1 to 4.

[0019] [Composition 6] The electrolyte membrane comprises the Ce ions and / or the Ce compound A, and the ratio of the number of moles of Ce (C) to the number of moles of acid groups (S) of the solid polymer electrolyte (=C / S) is 0.0005 or more and 0.15 or less, according to any one of configurations 1 to 5.

[0020] [Composition 7] The water-repellent layer of the anode gas diffusion layer contains the Ce compound B, and the content of the Ce compound B is 0.1 μg / cm³. 2 More than 100.0μg / cm 2 A polymer electrolyte fuel cell as described in any one of the following configurations 1 to 6.

[0021] [Configuration 8] The water-repellent layer of the cathode gas diffusion layer contains the Ce compound C, and the content of the Ce compound C is 0.1 μg / cm 2 or more and 100.0 μg / cm 2 or less. The solid polymer fuel cell according to any one of Configurations 1 to 7 described above.

[0022] [1.1. Electrolyte Membrane] The electrolyte membrane contains a solid polymer electrolyte. In the present invention, the type of the solid polymer electrolyte contained in the electrolyte membrane is not particularly limited. Examples of the solid polymer electrolyte include (a) Fluorine-based electrolytes such as Nafion (registered trademark), Flemion (registered trademark), Aquivion (registered trademark), and Aciplex (registered trademark), (b) All-aromatic hydrocarbon-based electrolytes composed of polyether ether ketone, polysulfone, polyether sulfone, polyimide, polyphenylene, polyamide, polyamide imide, or derivatives thereof, into which acid groups such as sulfonic acid groups are introduced, (c) Partially aromatic hydrocarbon-based electrolytes having an aromatic ring in a part of the polymer chain of aliphatic hydrocarbon-based electrolytes, and the like.

[0023] The electrolyte membrane may contain only the solid polymer electrolyte, or may be a composite of the solid polymer electrolyte and a reinforcing material. Examples of the reinforcing material include (a) Porous membranes or non-woven fabrics of fluorine-based resins such as polytetrafluoroethylene (PTFE), perfluoroalkoxy alkane (PFA), perfluoroethylene propene copolymer (FEP), and ethylene tetrafluoroethylene copolymer (ETFE), (b) Porous membranes or non-woven fabrics of hydrocarbon-based resins such as polyethylene (PE) and polypropylene (PP), and the like.

[0024] [1.2. Anode Catalyst Layer] An anode catalyst layer is bonded to one side of the electrolyte membrane. The anode catalyst layer comprises an electrode catalyst (anode catalyst) that is active for hydrogen oxidation reactions and a catalyst layer ionomer. The anode catalyst may consist only of catalyst particles (A) that are active for hydrogen oxidation reactions, or the catalyst particles (A) may be supported on the surface of a carrier. In the present invention, the materials of the catalyst layer ionomer, catalyst particles (A), and support are not particularly limited, and the most suitable materials can be selected depending on the purpose.

[0025] The anode-side catalyst layer ionomer may be made of the same material as the solid polymer electrolyte that constitutes the electrolyte membrane, or it may be made of a different material. Examples of catalyst particles (A) include precious metals, alloys containing two or more precious metals, and alloys of one or more precious metals with one or more base metals. Examples of carriers include carbon black, carbon nanotubes, carbon nanohorns, activated carbon, natural graphite, mesocarbon microbeads, and glassy carbon powder.

[0026] [1.3. Cathode Catalyst Layer] A cathode catalyst layer is bonded to the other side of the electrolyte membrane. The cathode catalyst layer comprises an electrode catalyst (cathode catalyst) that is active for the oxygen reduction reaction and a catalyst layer ionomer. The cathode catalyst may consist only of catalyst particles (B) that are active for the oxygen reduction reaction, or the catalyst particles (B) may be supported on the surface of a carrier. In the present invention, the materials of the catalyst layer ionomer, catalyst particles (B), and support are not particularly limited, and the most suitable materials can be selected depending on the purpose.

[0027] The catalyst layer ionomer on the cathode side may be made of the same material as the solid polymer electrolyte that constitutes the electrolyte membrane, or it may be made of a different material. Examples of catalyst particles (B) include precious metals, alloys containing two or more precious metals, and alloys containing one or more precious metals and one or more base metals. Examples of carriers include carbon black, carbon nanotubes, carbon nanohorns, activated carbon, natural graphite, mesocarbon microbeads, and glassy carbon powder.

[0028] [1.4. Anode gas diffusion layer, cathode gas diffusion layer] An anode gas diffusion layer and a cathode gas diffusion layer are arranged on both sides of the MEA. In this invention, the structure of the gas diffusion layer is not particularly limited, and an optimal structure can be selected depending on the purpose. The gas diffusion layer typically comprises a substrate made of carbon paper or the like, and a water-repellent layer (microporous layer) formed on the surface of the substrate. The water-repellent layer typically consists of a composite of conductive particles such as carbon and a water-repellent resin such as polytetrafluoroethylene.

[0029] [1.5. Tungsten compound A, Tungsten compound B] The polymer electrolyte fuel cell according to the present invention is (a) Tungsten compound A added to the anode catalyst layer, and / or (b) Tungsten compound B added to the cathode catalyst layer Includes.

[0030] [1.5.1. Composition of Tungsten Compounds A and B] In the present invention, tungsten compounds A and B are each composed of the following chemical formulas: WO x It has a composition represented by nH2O (2≦x≦3, 0≦n≦3, where x and n are non-integers). WO x nH2O has the effect of decomposing hydrogen peroxide. Therefore, adding it to the anode catalyst layer and / or cathode catalyst layer can suppress the degradation of the solid polymer electrolyte.

[0031] The anode catalyst layer may contain one type of tungsten compound A, or it may contain two or more types of tungsten compound A. Similarly, the cathode catalyst layer may contain one type of tungsten compound B, or it may contain two or more types of tungsten compound B. Furthermore, if the polymer electrolyte fuel cell contains both tungsten compound A and tungsten compound B, tungsten compound A and tungsten compound B may be compounds with the same composition, or they may be compounds with different compositions.

[0032] [1.5.2. Content of Tungsten Compound A] "Content of tungsten compound A (μg / cm³) 2 ) refers to the mass of tungsten compound A per unit area of ​​the anode catalyst layer.

[0033] During the operation of a polymer electrolyte membrane fuel cell, hydrogen peroxide is generated in the anode catalyst layer. This hydrogen peroxide undergoes the Fenton reaction to become a ·OH radical, which is known to degrade the electrolyte in the MEA. Therefore, adding tungsten compound A, which has hydrogen peroxide decomposition properties, to the anode catalyst layer may decompose the hydrogen peroxide before the ·OH radical is generated.

[0034] In this invention, the content of tungsten compound A is not particularly limited, and the optimal content can be selected depending on the purpose. Generally, if the content of tungsten compound A is too low, a sufficient degradation suppression effect may not be obtained. Therefore, the content of tungsten compound A is 0.1 μg / cm³. 2 The above is preferable. The content is more preferably 0.5 μg / cm³. 2 More preferably, 0.8 μg / cm³ 2 More preferably, 1.0 μg / cm³ 2 That is the case.

[0035] On the other hand, if the content of tungsten compound A is excessive, battery performance may decrease. This is thought to be because the excess tungsten compound A inhibits proton conduction and / or gas diffusion within the anode catalyst layer. Therefore, the content of tungsten compound A should be 50.0 μg / cm³. 2 The following is preferable. The content is more preferably 30.0 μg / cm³. 2 More preferably, 15.0 μg / cm³ 2 The following applies:

[0036] [1.5.3. Content of Tungsten Compound B] "Content of tungsten compound B (μg / cm³) 2 ) refers to the mass of tungsten compound B per unit area of ​​the cathode catalyst layer.

[0037] Hydrogen peroxide generated in the anode catalyst layer may diffuse through the electrolyte membrane without decomposing and reach the cathode catalyst layer. In such cases, adding tungsten compound B, which has hydrogen peroxide decomposing properties, to the cathode catalyst layer may decompose the hydrogen peroxide before ·OH radicals are generated.

[0038] In this invention, the content of tungsten compound B is not particularly limited, and the optimal content can be selected depending on the purpose. Generally, if the content of tungsten compound B is too low, a sufficient degradation suppression effect may not be obtained. Therefore, the content of tungsten compound B is 0.1 μg / cm³. 2 The above is preferable. The content is more preferably 0.5 μg / cm³. 2 More preferably, 0.8 μg / cm³ 2 More preferably, 1.0 μg / cm³ 2 That's all.

[0039] On the other hand, if the content of tungsten compound B is excessive, battery performance may decrease. This is thought to be because the excess tungsten compound B inhibits proton conduction and / or gas diffusion within the cathode catalyst layer. Therefore, the content of tungsten compound B should be 50.0 μg / cm³. 2 The following is preferable. The content is more preferably 30.0 μg / cm³. 2 More preferably, 15.0 μg / cm³ 2 The following applies:

[0040] [1.6. Ce ions, Ce compounds A-C] The polymer electrolyte fuel cell according to the present invention, in addition to a tungsten compound, (a) Ce ions added to the electrolyte membrane, (b) Ce compound A added to the electrolyte membrane, (c) Ce compound B added to the water-repellent layer of the anode gas diffusion layer, (d) Ce compound C added to the water-repellent layer of the cathode gas diffusion layer It further includes one or more selected from the group consisting of the following.

[0041] [1.6.1. Composition of Ce Compounds] Both Ce ions and Ce compounds have the effect of scavenging ·OH radicals. Therefore, when these are added to the electrolyte membrane and / or water-repellent layer, even if ·OH radicals are generated from hydrogen peroxide that could not be completely decomposed by tungsten compounds A and B, the ·OH radicals can be scavenged by the Ce ions or Ce compounds.

[0042] The Ce compound may be a water-soluble compound or a sparingly soluble compound. When a water-soluble Ce compound is used, the Ce compound dissociates, and some of the protons of the acid group of the solid polymer electrolyte are replaced by Ce ions. On the other hand, when a sparingly soluble Ce compound is used, the Ce compound remains dispersed within the electrolyte membrane or water-repellent layer, and Ce ions gradually leach out from the Ce compound. Examples of Ce compounds include nitrates, sulfates, carbonates, formates, acetates, oxalates, citrates, perchlorates, phosphates, chlorides, fluorides, oxides, hydroxides, acetylacetonate compounds, and cerium alkoxides.

[0043] When adding Ce compound A to an electrolyte membrane, the electrolyte membrane may contain one type of Ce compound A, or it may contain two or more types of Ce compound A. Similarly, when Ce compound B is added to the water-repellent layer of the anode gas diffusion layer, the water-repellent layer may contain one type of Ce compound B, or it may contain two or more types of Ce compound B. Similarly, when adding Ce compound C to the water-repellent layer of the cathode gas diffusion layer, the water-repellent layer may contain one type of Ce compound C, or it may contain two or more types of Ce compound C. Furthermore, if the polymer electrolyte fuel cell contains two or more of Ce compounds A to C, these compounds may have the same composition or may have different compositions.

[0044] [1.6.2. Components to which Ce ions and Ce compounds A-C are added] The components to which Ce ions and Ce compounds are added are not particularly limited, but a water-repellent layer of the electrolyte membrane and / or gas diffusion layer is preferred. For example, when tungsten compound A is added to the anode catalyst layer, it is preferable to add Ce ions to the electrolyte membrane and / or add Ce compound A to the electrolyte membrane and / or add Ce compound B to the water-repellent layer of the anode gas diffusion layer. Alternatively, if tungsten compound B is added to the cathode catalyst layer, it is preferable to add Ce ions to the electrolyte membrane and / or Ce compound A to the electrolyte membrane and / or Ce compound C to the water-repellent layer of the cathode gas diffusion layer.

[0045] When Ce ions or Ce compounds A-C are added to a component different from the component to which tungsten compounds A and B are added, the degradation of the solid polymer electrolyte may be suppressed compared to when both are added to the same component (e.g., an electrolyte membrane). This is thought to be because, in addition to each component functioning as a degradation inhibitor, Ce ions diffuse into the catalyst layer and exert a degradation inhibitory effect through a synergistic effect with tungsten compounds A and B present in the catalyst layer.

[0046] [1.6.3. Content of Ce ions or Ce compounds A-C] [A. C / S ratio] The "C / S ratio" is an index that represents the content of Ce ions or Ce compound A contained in the electrolyte membrane, and refers to the ratio of the total number of moles of Ce (C) contained in the electrolyte membrane to the number of moles of acid groups (S) of the solid polymer electrolyte contained in the electrolyte membrane.

[0047] When the electrolyte membrane contains Ce ions and / or Ce compound A, the C / S ratio is not particularly limited, and an optimal value can be selected depending on the purpose. Generally, if the C / S ratio becomes too small, a sufficient degradation suppression effect may not be obtained. Therefore, a C / S ratio of 0.0005 or higher is preferred. More preferably, the C / S ratio is 0.001 or higher, and even more preferably, 0.005 or higher.

[0048] On the other hand, if the C / S ratio becomes too high, battery performance may decrease. Therefore, a C / S ratio of 0.15 or less is preferable. More preferably, the C / S ratio is 0.10 or less, and even more preferably, 0.05 or less.

[0049] [Content of B. Ce compound B] "Content of Ce compound B (μg / cm³) 2 ) refers to the mass of Ce compound B per unit area of ​​the water-repellent layer formed on the MEA-side surface of the anode gas diffusion layer.

[0050] In this invention, the content of Ce compound B is not particularly limited, and the optimal content can be selected depending on the purpose. Generally, if the content of Ce compound B is too low, a sufficient degradation suppression effect may not be obtained. Therefore, the content of Ce compound B is 0.1 μg / cm³. 2 The above is preferable. The content is more preferably 0.5 μg / cm³. 2 More preferably, 1.0 μg / cm³ 2 That's all.

[0051] On the other hand, excessive amounts of Ce compound B can degrade battery performance. Therefore, the Ce compound B content should be 100.0 μg / cm³. 2 The following is preferable. The content is more preferably 50.0 μg / cm³. 2 More preferably, 25.0 μg / cm³ 2 The following applies:

[0052] [Content of C. Ce compound C] "Content of Ce compound C (μg / cm³) 2 ) refers to the mass of Ce compound C per unit area of ​​the water-repellent layer formed on the MEA-side surface of the cathode gas diffusion layer.

[0053] In this invention, the content of Ce compound C is not particularly limited, and the optimal content can be selected depending on the purpose. Generally, if the content of Ce compound C is too low, a sufficient degradation suppression effect may not be obtained. Therefore, the content of Ce compound C is 0.1 μg / cm³. 2 The above is preferable. The content is more preferably 0.5 μg / cm³. 2 More preferably, 1.0 μg / cm³ 2 That's all.

[0054] On the other hand, excessive amounts of Ce compound C can degrade battery performance. Therefore, the Ce compound C content should be 100.0 μg / cm³. 2 The following is preferable. The content is more preferably 50.0 μg / cm³. 2More preferably, 25.0 μg / cm³ 2 The following applies:

[0055] [2. Method for manufacturing polymer electrolyte fuel cells] The polymer electrolyte fuel cell according to the present invention can be manufactured by various methods. For example, a catalyst layer containing tungsten compound A or tungsten compound B (a) Prepare a dispersion in which a solid polymer electrolyte, an electrode catalyst, and tungsten compound A or tungsten compound B are dissolved or dispersed in a solvent. (b) Cast the dispersion onto the substrate surface and allow the solvent to evaporate. It can be manufactured by doing so.

[0056] Furthermore, for example, an electrolyte membrane containing Ce ions and / or Ce compound A, (a) Prepare a dispersion in which a solid polymer electrolyte and a water-soluble or sparingly soluble Ce compound A are dissolved or dispersed in a solvent. (b) Cast the dispersion onto the substrate surface, or impregnate the dispersion into the pores of the reinforcing material and evaporate the solvent. It can be manufactured by doing so.

[0057] Furthermore, for example, a water-repellent layer containing Ce compound B or Ce compound C, (a) Prepare a dispersion in which a water-repellent resin, conductive particles, and Ce compound B or Ce compound C are dissolved or dispersed in a solvent. (b) Apply the dispersion to the surface of the gas diffusion layer substrate and allow the solvent to evaporate. It can be manufactured by doing so.

[0058] By bonding catalyst layers to both sides of the obtained electrolyte membrane, a membrane electrode assembly (MEA) is obtained. Furthermore, by placing gas diffusion layers on both sides of the MEA, a membrane-electrode-gas diffusion layer assembly (MEGA) is obtained. Furthermore, by placing separators equipped with gas channels on both sides of the MEGA, a polymer electrolyte fuel cell according to the present invention is obtained.

[0059] [3. Effect] Certain tungsten compounds have the effect of decomposing hydrogen peroxide. Furthermore, Ce ions and Ce compounds have the effect of scavenging radicals. Therefore, adding both tungsten compounds and Ce ions or Ce compounds to a solid polymer electrolyte can suppress the degradation of the solid polymer electrolyte caused by hydrogen peroxide and radicals. However, for example, if both tungsten compounds and Ce ions are added to the electrolyte membrane simultaneously, the degradation suppression effect may be insufficient.

[0060] In contrast, when a tungsten compound is added to the catalyst layer and Ce ions or Ce compounds are added to a component other than the catalyst layer (e.g., the electrolyte membrane), the degradation of the solid polymer electrolyte may be suppressed compared to when these are added to the same component (e.g., the electrolyte membrane).

[0061] By adding an appropriate amount of tungsten compound to the catalyst layer, H2O2 can be decomposed and rendered harmless without significantly inhibiting proton conduction by ionomers within the catalyst layer. As a result, it is believed that battery performance can be maintained and chemical degradation of the solid polymer electrolyte can be suppressed. Furthermore, even if some of the H2O2 decomposes and radicals are generated, (a) Ce ions or Ce compound A contained in the electrolyte membrane, or (b) Ce ions that have diffused from Ce compound B or Ce compound C contained in the water-repellent layer to the electrolyte membrane or catalyst layer It is thought that this process scavenges radicals and suppresses the degradation of solid polymer electrolytes. [Examples]

[0062] (Examples 1-2, Comparative Examples 1-2) [1. Sample Preparation] [1.1. Example 1] An anode catalyst ink was prepared by mixing an electrolyte solution (D2020, Nafion® dispersion, 1000EW, 20 mass%, manufactured by Chemours), Pt-supported carbon, and WO3·H2O. The amount of WO3·H2O added was such that the WO3·H2O content was 7.0 μg / cm³ when the catalyst layer was formed. 2 The amount was determined to be such that the catalyst ink was applied to the substrate surface to prepare an anode-side catalyst layer sheet. Furthermore, the cathode-side catalyst layer sheet was prepared in the same manner as the anode-side catalyst layer sheet, except that WO3·H2O was not added.

[0063] Next, an electrolyte membrane containing Ce ions (Nafion®) was fabricated. The C / S ratio was set to 0.015. A catalyst layer containing WO3·H2O was hot-pressed onto the anode side of the electrolyte membrane, and a catalyst layer not containing WO3·H2O was hot-pressed onto the cathode side to obtain a membrane electrode assembly.

[0064] [1.2. Example 2] The amount of WO3·H2O added to the catalyst ink is such that when the catalyst layer is formed, the WO3·H2O content is 1.2 μg / cm³. 2 A film electrode assembly was fabricated in the same manner as in Example 1, except that the quantity was set to the amount specified.

[0065] [1.3. Comparative Example 1] A film electrode assembly containing only Ce ions was prepared in the same manner as in Example 1, except that WO3·H2O was not added to the catalyst inks of both electrodes.

[0066] [1.4. Comparative Example 2] A catalyst layer sheet was prepared in the same manner as in Example 1, except that WO3·H2O was not added to the catalyst inks at both electrodes. Next, an electrolyte membrane (Nafion®) containing Ce ions and WO3·H2O was prepared. The C / S ratio was set to 0.015. The WO3·H2O content was set to 1 mass% of the dry weight of the electrolyte membrane. A catalyst layer without WO3·H2O was hot-pressed onto both sides of the electrolyte membrane to obtain a membrane electrode assembly.

[0067] [2. Test Method] [2.1. OCV Durability Test] The fabricated membrane electrode assembly underwent an OCV durability test. The test conditions were: temperature: 95°C, humidity: 40%RH, anode gas / cathode gas: H2 / Air, test time: 90 hours. After the test, the amount of fluoride ions in the recovered water was measured, and F - The amount of elution was calculated.

[0068] [2.2. Voltage Fluctuation Endurance Test] Voltage fluctuation endurance tests were performed on the fabricated film electrode assemblies. The test conditions were: temperature: 82°C, humidity: 30%RH, voltage fluctuation range: 0V to 1.25V, and number of cycles: 3600 cycles. After the test, the current density was determined at 60°C, 80%RH, and 0.6V.

[0069] [3. Results] [3.1. OCV Durability Test] Figure 1 shows the WO3·H2O content and the normalized total F - This shows the relationship with the amount of elution. Note that "normalized total F - "Elution amount" refers to the total F of each sample. - The amount of elution is the total F of Comparative Example 1 - This refers to the value obtained by dividing by the amount of elution. Figure 2 shows the normalized total F of the cells obtained in Example 2 and Comparative Example 2. - The amount of elution is shown. From Figures 1 and 2, the following can be seen.

[0070] (1) Examples 1 and 2 had a total F compared to Comparative Example 1. - The amount of elution decreased. This is thought to be because, in addition to adding Ce ions to the electrolyte membrane, adding WO3·H2O to the catalyst layer promoted the decomposition of H2O2, reducing the amount of radicals generated. (2) Standardized total F - To reduce the elution amount to 0.4 or less, the WO3·H2O content should be 0.8 μg / cm³. 2 More than 7.0μg / cm 2 It was found that the following should be done. Also, the normalized total F -To reduce the elution amount to 0.3 or less, the WO3·H2O content must be 1.0 μg / cm³. 2 More than 5.0μg / cm 2 It was found that the following should be done. Furthermore, the normalized total F - To reduce the elution amount to 0.22 or less, the WO3·H2O content must be 1.1 μg / cm³. 2 More than 2.0μg / cm 2 I found out that the following is what should be done. (3) Example 2 had a total F compared to Comparative Example 2. - The amount of elution decreased. This is thought to be because, in addition to WO3·H2O and Ce ions functioning as degradation inhibitors in their respective additives, Ce ions diffused into the catalyst layer, improving the hydrogen peroxide decomposition effect of WO3·H2O.

[0071] [3.2. Voltage Fluctuation Endurance Test] Figure 3 shows the relationship between the WO3·H2O content and the normalized current density at 60°C, 80%RH, and 0.6V before and after the voltage fluctuation endurance test (82°C, 30%RH). "Normalized current density" refers to the value obtained by dividing the current density of each sample by the current density of Comparative Example 1. The WO3·H2O content is 0 μg / cm³ 2 (Comparative Example 1), or 1.2 μg / cm³ 2 In the case of (Example 2), there was no significant change in current density before and after the durability test. On the other hand, the WO3·H2O content was 7.0 μg / cm³. 2 In the case of (Example 1), the current density decreased after the durability test. However, this is not due to the degradation of the electrolyte, but rather because the WO3·H2O near the Pt inhibited the diffusion of gas within the catalyst layer.

[0072] Although embodiments of the present invention have been described in detail above, the present invention is not limited in any way to the above embodiments, and various modifications are possible without departing from the spirit of the present invention. [Industrial applicability]

[0073] The polymer electrolyte fuel cell according to the present invention can be used as an on-board power source or a stationary small-scale generator.

Claims

1. A polymer electrolyte fuel cell with the following configuration. (1) The polymer electrolyte fuel cell is An electrolyte membrane containing a solid polymer electrolyte, an anode catalyst layer bonded to one side of the electrolyte membrane, A cathode catalyst layer bonded to the other side of the electrolyte membrane, An anode gas diffusion layer is disposed outside the anode catalyst layer, A cathode gas diffusion layer is disposed on the outside of the cathode catalyst layer. It is equipped with. (2) The polymer electrolyte fuel cell is (A) Tungsten compound A added to the anode catalyst layer, and / or tungsten compound B added to the cathode catalyst layer, (B) One or more selected from the group consisting of Ce ions added to the electrolyte membrane, Ce compound A added to the electrolyte membrane, Ce compound B added to the water-repellent layer of the anode gas diffusion layer, and Ce compound C added to the water-repellent layer of the cathode gas diffusion layer. Includes. (3) The tungsten compound A and the tungsten compound B each have the following compositional formula: WO x nH 2 It has a composition represented by O (where 2 ≤ x ≤ 3, 0 ≤ n ≤ 3, and x and n each include non-integers).

2. The tungsten compound A and, One or more selected from the group consisting of the Ce ion, the Ce compound A, and the Ce compound B A polymer electrolyte fuel cell according to claim 1, comprising:

3. The tungsten compound B, One or more selected from the group consisting of the Ce ion, the Ce compound A, and the Ce compound C A polymer electrolyte fuel cell according to claim 1, comprising:

4. The anode catalyst layer contains the tungsten compound A, and the content of the tungsten compound A is 0.1 μg / cm³. 2 50.0 μg / cm or more 2 The polymer electrolyte fuel cell according to claim 1, wherein the following applies:

5. The cathode catalyst layer contains the tungsten compound B, and the content of the tungsten compound B is 0.1 μg / cm³. 2 50.0 μg / cm or more 2 The polymer electrolyte fuel cell according to claim 1, wherein the following applies:

6. The polymer electrolyte fuel cell according to claim 1, wherein the electrolyte membrane contains the Ce ions and / or the Ce compound A, and the ratio of the number of moles of Ce (C) to the number of moles of acid groups (S) of the solid polymer electrolyte (= C / S) is 0.0005 or more and 0.15 or less.

7. The water-repellent layer of the anode gas diffusion layer contains the Ce compound B, and the content of the Ce compound B is 0.1 μg / cm³. 2 100.0 μg / cm or more 2 The polymer electrolyte fuel cell according to claim 1, wherein the following applies:

8. The water-repellent layer of the cathode gas diffusion layer contains the Ce compound C, and the content of the Ce compound C is 0.1 μg / cm 2 or more and 100.0 μg / cm 2 or less. The solid polymer fuel cell according to claim 1.

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