JP2019114371A - Solid polymer fuel cell, electrolyte film, and catalyst layer - Google Patents

Abstract

To provide a solid polymer fuel cell, an electrolyte film and a catalyst layer which enable the achievement of both of a high proton conductivity and a high durability at a high level.SOLUTION: A solid polymer fuel cell comprises: an electrolyte film containing a solid polymer electrolyte; an anode-side catalyst layer joined to one face of the electrolyte film; a cathode-side catalyst layer joined to the other face of the electrolyte film; and Ag@CeOparticles added to one or more selected from a group consisting of the electrolyte film, the anode-side catalyst layer and the cathode-side catalyst layer. The electrolyte film includes: the solid polymer electrolyte; and Ag@CeOparticles added into the solid polymer electrolyte. The catalyst layer includes: an electrode catalyst; an electrolyte in the catalyst layer, covering the surface of the electrode catalyst; and Ag@CeOparticles among the electrode catalyst or added into the electrolyte in the catalyst layer.SELECTED DRAWING: Figure 2

Description

The present invention relates to a polymer electrolyte fuel cell, an electrolyte membrane, and a catalyst layer, and more specifically, a solid polymer containing composite particles (Ag @ CeO ₂ particles) having the function of suppressing deterioration of a solid polymer electrolyte by radicals. The present invention relates to a molecular fuel cell, an electrolyte membrane, and a catalyst layer.

In a soda electrolytic device, a water electrolytic device, a fuel cell or the like, a membrane electrode assembly (MEA) is used at a site where an electrochemical reaction occurs. In MEA, when impurity ions are eluted from component parts or impurity ions enter from the outside, the acid group or hydroxyl group of the electrolyte is ion-exchanged with the impurity ions, which causes the electrolyte to be attacked by radicals and tends to deteriorate. It is
For example, in a fuel cell, it is known that an increase in resistance of an electrolyte membrane, an increase in cross leak, a shortening of life due to perforation, and the like occur. Furthermore, catalyst poisoning may occur due to the deterioration product generated by radical attack, and the electrolytic performance and the battery performance may be degraded.

In order to solve this problem, various proposals have conventionally been made.
For example, in Patent Document 1, some of protons of cation exchange groups provided in the perfluoro type electrolyte are V, Mn, Nb, Ta, Cr, Mo, W, Fe, Ru, Ni, Pd, Pt, A solid polymer electrolyte substituted with at least one metal ion selected from Ag, Ce, Nd, Pr, Sm, Co, Gd, Tb, Dy, Ho, and Er, and a solid polymer fuel cell using the same It is disclosed.
In the document, it is possible to simultaneously achieve high electrical conductivity and high durability by replacing a part of protons of cation exchange groups contained in the perfluoro electrolyte with a specific metal ion. Have been described.

Patent Document 2 discloses a solid polymer fuel cell in which Ag ⁺ is added to the cathode side catalyst layer.
In the document, it is described that the durability of the fuel cell is improved by adding Ag ⁺ having hydrogen peroxide resolution to the cathode side catalyst layer.

In Patent Document 3 and Non-Patent Documents 1 and 2, although not a fuel cell, it is composed of silver particles as a core and ceria fine particles having an average primary particle diameter of 1 to 100 nm covering the periphery of the silver particles. Aggregates are disclosed.
The document describes that such an aggregate can be used as an oxidation catalyst for particulate matter (PM) contained in diesel exhaust gas, or as a catalyst for reduction reaction (eg, nitro group → amino group etc.) There is.

Certain metal ions are known to ionically decompose hydrogen peroxide to suppress the generation of radicals. Therefore, there are many cases where such metal ions are applied as a fuel cell deterioration inhibitor (Patent Documents 1 and 2). However, when a metal ion is added to MEA, the apparent equivalent weight (EW) increases because the acid group of the electrolyte and the metal ion simultaneously form a salt. As a result, the proton conductivity at low humidity decreases and the output performance decreases.
On the other hand, if the amount of metal ion added is reduced to avoid this, the hydrogen peroxide resolution is reduced. As a result, the durability of the MEA is reduced.

  Therefore, in order to achieve both high proton conductivity and high durability, it is necessary to find out the optimum metal ion addition amount. However, in the method of adding metal ions to MEA, there is a limit to the compatibility between high proton conductivity and high durability.

JP, 2006-338912, A JP, 2006-244721, A Patent No. 4661690

Nanostructured Ceria-Silver Synthesized in a One-Pot Redox Reaction Carbonyzations Carbon Oxidation, J. AM. CHEM. SOC. 2010, 132, 13154-13155 Design of a Silver-Cerium Dioxide Core-Shell Nanocomposite Catalyst for Chemoselective Reduction Reactions, Angew. Chem. Int. Ed. 2012, 51, 136-139

  The problem to be solved by the present invention is to provide a polymer electrolyte fuel cell, an electrolyte membrane, and a catalyst layer capable of achieving both high proton conductivity and high durability in a high level.

In order to solve the above-mentioned subject, the polymer electrolyte fuel cell concerning the present invention,
An electrolyte membrane comprising a solid polymer electrolyte,
An anode catalyst layer bonded to one surface of the electrolyte membrane;
A cathode catalyst layer bonded to the other surface of the electrolyte membrane;
Ag @ CeO ₂ particles added to any one or more selected from the group consisting of the electrolyte membrane, the anode catalyst layer, and the cathode catalyst layer,
The Ag @ CeO ₂ particles are characterized by having a core-shell structure in which the surface of an Ag core is covered with a CeO ₂ shell.

The electrolyte membrane according to the present invention is
Solid polymer electrolyte,
And Ag @ CeO ₂ particles added in the solid polymer electrolyte,
The Ag @ CeO ₂ particles are characterized by having a core-shell structure in which the surface of an Ag core is covered with a CeO ₂ shell.

Furthermore, the catalyst layer according to the present invention is
An electrode catalyst,
An electrolyte in a catalyst layer coating the surface of the electrode catalyst;
Ag @ CeO ₂ particles added between the electrode catalysts or in the electrolyte in the catalyst layer,
The Ag @ CeO ₂ particles are characterized by having a core-shell structure in which the surface of an Ag core is covered with a CeO ₂ shell.

The Ag @ CeO ₂ particles behave mainly as inorganic particles, not ions, in a fuel cell environment because they have a core-shell structure in which an Ag core is covered with a CeO ₂ shell. That is, the possibility that the metal ions eluted from the Ag @ CeO ₂ particles and the acid group of the electrolyte form a salt is low. In addition, Ag @ CeO ₂ particles have a decomposition effect of hydrogen peroxide (or an effect as a radical scavenging agent) even in a very small amount, and exhibit such a decomposition effect without being ionized. Therefore, by adding this to the electrolyte membrane and / or the catalyst layer, it is possible to achieve both high proton conductivity and high durability at a high level.

It is a SEM image of Ag @ CeO ₂ particle | grains. It is a figure which shows the relationship between an acidic radical substitution rate and F discharge | emission amount (FER).

Hereinafter, an embodiment of the present invention will be described in detail.
[1. Polymer Electrolyte Fuel Cell]
The polymer electrolyte fuel cell according to the present invention is
An electrolyte membrane comprising a solid polymer electrolyte,
An anode catalyst layer bonded to one surface of the electrolyte membrane;
A cathode catalyst layer bonded to the other surface of the electrolyte membrane;
It further comprises Ag @ CeO ₂ particles added to any one or more selected from the group consisting of the electrolyte membrane, the anode catalyst layer, and the cathode catalyst layer.

[1.1. Electrolyte membrane]
The electrolyte membrane contains a solid polymer electrolyte. In the present invention, the material of the solid polymer electrolyte is not particularly limited. The solid polymer electrolyte may be either a fluorine-based electrolyte or a hydrocarbon-based electrolyte. Moreover, it does not specifically limit about the kind of acidic radical of a solid polymer electrolyte. As the acid group, there are a sulfonic acid group, a carboxylic acid group, a phosphonic acid group, a sulfonimide group and the like. The solid polymer electrolyte may contain only any one of these acid groups, or may contain two or more.
Furthermore, the electrolyte membrane may be made of only a solid polymer electrolyte, or may be a composite of a solid polymer electrolyte and a reinforcing layer.

[1.2. Catalyst layer]
The catalyst layer is a portion to be a reaction site of the electrode reaction. The anode catalyst layer is bonded to one surface of the electrolyte membrane, and the cathode catalyst layer is bonded to the other surface. The catalyst layer includes an electrode catalyst or an electrode catalyst supported on a carrier, and an electrolyte in the catalyst layer covering the periphery thereof. In the present invention, the materials of the electrode catalyst, the electrolyte in the catalyst layer and the support are not particularly limited. Examples of the electrode catalyst include platinum, a platinum alloy, palladium, ruthenium, rhodium and the like, and alloys of these. Further, the material of the electrolyte in the catalyst layer may be the same material as the electrolyte membrane, or may be a different material.

[1.3. Gas diffusion layer]
Generally, a gas diffusion layer is bonded to the outside of each catalyst layer, but the gas diffusion layer can be omitted. The gas diffusion layer is for supplying a reaction gas to the electrode while performing exchange of electrons with the electrode. In general, carbon paper, carbon cloth or the like is used for the gas diffusion layer. Also, in order to increase water repellency, a surface of carbon paper etc. coated with a mixture of water repellent polymer powder such as polytetrafluoroethylene and carbon powder (water repellent layer) is used as a gas diffusion layer It is good.

[1.4. Ag @ CeO ₂ particles]
[1.4.1. composition]
"Ag @ CeO ₂ particles" refers to particles having a core-shell structure in which the surface of an Ag core is covered with a CeO ₂ shell. Such Ag @ CeO ₂ particles can be produced by the method described later.
Ag @ CeO ₂ particles function as a radical scavenger or hydrogen peroxide decomposer in a fuel cell environment. This is because Ce ^{3 +} is oxidized from Ce ^{3 +} to Ce ^{4 +} when radicals or hydrogen peroxide is decomposed in the CeO ₂ shell, but the Ag core rapidly reduces Ce ^{4 +} to Ce ^{3 +} . It is believed that there is.

[A. Ag core]
"Ag core" refers to particles containing Ag. The Ag core may consist essentially of Ag, or may be an alloy containing other metals. Other metals include, for example, Pd, Rh, Cu and the like. In addition, a part of Ag may form an oxide.
In order to obtain high radical resistance, the Ag content in the Ag core is preferably 0.3% by mass or more. The Ag content is preferably 75% by mass or more, more preferably 90% by mass or more.

[B. CeO ₂ shell]
The “CeO ₂ shell” refers to a structure formed by aggregation of fine particles containing CeO ₂ (hereinafter, also simply referred to as “CeO ₂ fine particles”) around the Ag core. The CeO ₂ fine particles may consist essentially of CeO ₂ or may contain additional components. Examples of the additive component include rare earth elements other than Ce such as La and Nd, Zr, Y, Al, Si and the like. These may effect of suppressing coarsening of CeO ₂ fine particles.

In the case where the CeO ₂ fine particles contain the additive component, the content of the additive component is preferably 1 mol% or more in order to obtain the above-described effect. The content of the additive component is preferably 5 mol% or more.
On the other hand, when the additive component is excessive, the effect as a radical scavenger or hydrogen peroxide decomposing agent is rather reduced. Therefore, the content of the additive component is preferably 30 mol% or less. The content of the additive component is preferably 20 mol% or less.
Here, "the content of the additive component" means the ratio of the number of moles of the additive component to the total number of moles of Ce and the additive component.

[C. Ratio of Ag core to CeO ₂ shell]
The ratio of the Ag core to the CeO ₂ shell contained in the Ag @ CeO ₂ particles affects the effect as a radical scavenger or hydrogen peroxide decomposing agent. If the proportion of Ag core is too low, the reduction rate of Ce will be slow. Therefore, the ratio (molar ratio) of Ag core / CeO ₂ shell is preferably 10/90. The ratio is preferably 35/65 or more, more preferably 40/60 or more.
On the other hand, if the proportion of the Ag core is too large, the decomposition rate of radicals or hydrogen peroxide will be slow. Therefore, the ratio (molar ratio) of Ag core / CeO ₂ shell is preferably 80/20 or less. The ratio is preferably 60/40 or less.
Here, the “ratio of Ag core / CeO ₂ shell” refers to the ratio of the total number of moles of the metal element contained in the Ag core to the total number of moles of the metal element contained in the CeO ₂ shell.

[1.4.2. Place of addition]
In a polymer electrolyte fuel cell, a membrane electrode assembly (MEA) in which an anode side catalyst layer and a cathode side catalyst layer are respectively joined to both sides of an electrolyte membrane (a gas diffusion layer is further joined to the outside of the catalyst layer) (Including a membrane-electrode-gas diffusion layer assembly (MEGA)). Ag @ CeO ₂ particles are added to any one or more selected from the group consisting of an electrolyte membrane contained in MEA, an anode catalyst layer, and a cathode catalyst layer.
Degradation of the solid polymer electrolyte due to radicals can occur in any of the electrolyte membrane and the catalyst layer. Therefore, even when Ag @ CeO ₂ particles are added to either the electrolyte membrane or the catalyst layer, deterioration of the solid polymer electrolyte due to radicals is suppressed. When Ag @ CeO ₂ particles are added to both the electrolyte membrane and the catalyst layer, the deterioration of the solid polymer electrolyte due to radicals is further suppressed.

[1.4.3. Acid group substitution rate]
The term “acid group substitution rate of Ag @ CeO ₂ particles” means that all metal elements contained in Ag @ CeO ₂ particles are ions (eg, Ag ⁺ , Ce ^{3 +} , La ^{3 +} , Nd ^{3 +} , Y ^{3 +} , Al ³⁺ , Si ⁴⁺ , Zr ⁴⁺ , Cu ²⁺ etc.), and it is assumed that the proton of the acid group of the electrolyte contained in MEA is substituted by the metal ion, the acid group contained in the electrolyte The ratio of the number of moles of ion-exchanged acid groups to the total number of moles of

In general, when the addition amount of Ag @ CeO ₂ particles is too small, deterioration of the polymer electrolyte due to radicals can not be sufficiently suppressed. Therefore, the acid group substitution rate of Ag @ CeO ₂ particles is preferably 0.001% or more. The acid group substitution rate is preferably 0.005% or more, more preferably 0.01% or more.
On the other hand, even if Ag @ CeO ₂ particles are added more than necessary, there is no difference in the effect and there is no real benefit. Therefore, the acid group substitution rate of Ag @ CeO ₂ particles is preferably 2.0% or less. The acid group substitution rate is preferably 0.1% or less, more preferably 0.05% or less.

[1.4.4. Average particle size]
The size of the Ag core and the CeO ₂ fine particles mainly depends on the calcination temperature at the time of synthesis. In the case of using the method described later, when the manufacturing conditions are optimized, the size of the Ag core is in the range of 10 nm to 400 nm. In addition, the size of the CeO ₂ fine particles constituting the CeO ₂ shell is in the range of 1 nm to 100 nm.
Furthermore, the periphery of the Ag core is covered with one or more layers of CeO ₂ fine particles. Moreover, there may be a case where a plurality of such core-shell particles are aggregated. Therefore, in the case of using the method described later, when the manufacturing conditions are optimized, the average particle size of the Ag @ CeO ₂ particles is in the range of 0.05 μm to 0.5 μm.
Here, the "average particle size" refers to a median diameter (d ₅₀ ) measured by a laser diffraction scattering method.

In the present invention, the average particle size of the Ag @ CeO ₂ particles is not particularly limited. However, the smaller the average particle size of the Ag @ CeO ₂ particles, the higher the effect obtained with a small amount of addition. Therefore, the average particle size is preferably 0.5 μm or less. The average particle size is preferably less than or equal to 0.1 μm.

[2. Electrolyte membrane]
The electrolyte membrane according to the present invention is
Solid polymer electrolyte,
And Ag @ CeO ₂ particles added in the solid polymer electrolyte.

[2.1. Solid polymer electrolyte]
In the present invention, the material of the solid polymer electrolyte is not particularly limited. The details of the solid polymer electrolyte constituting the electrolyte membrane are as described above, and thus the description thereof is omitted.

[2.2. Ag @ CeO ₂ particles]
Ag @ CeO ₂ particles have a core-shell structure in which the surface of an Ag core is covered with a CeO ₂ shell.
Also when adding Ag @ CeO ₂ particles to the electrolyte membrane, the acid group substitution ratio of Ag @ CeO ₂ particles is preferably 0.001% or more and 2.0% or less.
The average particle size of the Ag @ CeO ₂ particles is preferably 0.5 μm or less.
The details of the Ag @ CeO ₂ particles are as described above, and thus the description thereof is omitted.

[3. Catalyst layer]
The catalyst layer according to the present invention is
An electrode catalyst,
An electrolyte in a catalyst layer coating the surface of the electrode catalyst;
Ag @ CeO ₂ particles added between the electrode catalysts or in the electrolyte in the catalyst layer.

[3.1. Electrode catalyst and electrolyte in catalyst layer]
In the present invention, the materials of the electrode catalyst and the electrolyte in the catalyst layer are not particularly limited. The details of the electrode catalyst and the electrolyte in the catalyst layer are as described above, and thus the description thereof is omitted.

[3.2. Ag @ CeO ₂ particles]
Ag @ CeO ₂ particles have a core-shell structure in which the surface of an Ag core is covered with a CeO ₂ shell.
Also when adding Ag @ CeO ₂ particles to the catalyst layer, the acid group substitution ratio of Ag @ CeO ₂ particles is preferably 0.001% or more and 2.0% or less.
The average particle size of the Ag @ CeO ₂ particles is preferably 0.5 μm or less.
The details of the Ag @ CeO ₂ particles are as described above, and thus the description thereof is omitted.

[4. Method of producing Ag @ CeO ₂ particles]
Ag @ CeO ₂ particles are
(A) A solution containing an Ag salt, a solution containing a Ce salt, and a solution containing a pH adjuster are mixed to form precursor particles in which the surface of an Ag particle is covered with Ce compound fine particles,
(B) It can manufacture by baking precursor particle | grains.

[4.1. Precursor preparation process]
First, a solution containing an Ag salt, a solution containing a Ce salt, and a solution containing a pH adjuster are mixed to form precursor particles in which the surface of an Ag core is covered with Ce compound fine particles (precursor production step) . In the solution, a complexing agent, a reverse micelle agent, etc. may be further added.

[4.1.1. Ag salt and Ce salt]
Examples of Ag salts and Ce salts include nitrates, acetates, chlorides, sulfates, sulfites, inorganic complex salts and the like. These are all water soluble salts. Ag salts and Ce salts are particularly preferably nitrates (silver nitrate, cerium nitrate). When preparing Ag @ CeO ₂ particles containing metal elements other than Ag and Ce, a salt containing the metal element is used.
The solvent for dissolving the Ag salt and the Ce salt is not particularly limited. As the solvent, for example, water, alcohol (for example, methanol, ethanol, ethylene glycol), a mixed solvent thereof, and the like can be mentioned. The solvent is particularly preferably water.

The blending amounts of the Ag salt and the Ce salt do not have to completely match the composition of the target Ag @ CeO ₂ particles, and the optimal blending amount can be selected according to the purpose. For example, if excessively blended Ag salt against Ce salt, CeO ₂ almost all the fine particles produced in the solution is consumed for the generation of Ag @ CeO ₂ particles, other than Ag @ CeO ₂ particles in the solution the solid particles Can be suppressed.

[4.1.2. pH adjuster]
The precursor particles are formed by first forming Ce compound fine particles in a solution and then depositing Ag particles by the reduction action of the Ce compound fine particles. The reaction rate of such redox reaction depends on the pH in the solution. Therefore, it is preferable to control the oxidation-reduction reaction by appropriately adding a pH adjuster. Examples of pH adjusters include NaOH, KOH, NH ₃ , HNO ₃ , H ₂ SO ₄ and the like.
In order to suppress the formation of coarse Ag particles, it is preferable to form precursor particles in an alkaline solution. In this case, depending on the type of pH adjuster, precipitates other than the target precursor particles may be generated. Therefore, it is preferable to use ammonia as a pH adjuster. Ammonia also functions as a complexing agent for Ag and is therefore suitable as a pH adjuster.

[4.1.3. Complexing agent]
If necessary, a complexing agent may be added to the solution. Depending on the pH of the solution, precipitates other than the target precursor particles may be formed in the solution. In such a case, the formation of a precipitate can be suppressed by adding a complexing agent to the solution. The type of complexing agent is not particularly limited, and an optimum one can be selected according to the purpose. Examples of the complexing agent include ammonia, alkali salts of organic acids (glycolic acid, citric acid, tartaric acid etc.), thioglycolic acid, hydrazine, triethanolamine, ethylenediamine, glycine, pyridine, cyanide and the like.

[4.1.4. Reverse micelle agent]
If necessary, an aqueous solution of Ag or Ce may be added to the reverse micelle agent in which surfactant molecules are added to the nonpolar solution. In such a case, the size of the generated particles can be controlled by nanosize.
As surfactant which becomes a reverse micelle agent,
(A) anionic surfactants such as sodium bis (2-ethylhexyl) sulfosuccinate;
(B) Cationic surfactants such as hexadecyl trimethyl ammonium bromide, cetyl dimethyl benzyl ammonium bromide, butyl dodecyl dimethyl ammonium bromide, dioleyl dimethyl ammonium chloride, etc.
(C) nonionic surfactants such as pentaoxyethylene glycol dodecyl ether, hexaoxyethylene glycol dodecyl ether, polyoxyethylene nonyl phenyl ether, etc.
and so on.
Nonpolar solvents include cyclohexane, heptane, isooctane, benzene, chlorobenzene and the like.

[4.1.5. Mixing method]
As a method of mixing the solution,
(A) A method of adding a pH adjuster solution to a solution containing Ag salt and Ce salt (precipitation method),
(B) A method of adding a solution containing an Ag salt and a Ce salt to a pH adjuster solution (reverse precipitation method),
(C) A method in which a solution of an Ag salt or a Ce salt is mixed with a dispersion of a reverse micelle agent containing a surfactant and a nonpolar solvent (reverse micelle method)
and so on. Any method may be used in the present invention.
The mixing conditions such as the temperature in the solution, the solid content concentration in the solution, and the mixing time are not particularly limited, and optimum conditions can be selected according to the purpose. When the respective solutions are mixed under predetermined conditions, a redox reaction proceeds in the solution to obtain precursor particles in which the surface of the Ag particles is covered with the Ce compound fine particles.

[4.2. Firing process]
Next, after washing the precursor particles as necessary, the precursor particles are fired. Thus, the surface of the Ag core Ag @ CeO ₂ particles coated with CeO ₂ fine particles is obtained.
The firing conditions are not particularly limited, and it is preferable to select optimum conditions according to the purpose. Baking is usually performed by holding at 300 ° C. to 600 ° C. for 1 to 5 hours in an oxidizing atmosphere.

[5. Method of Manufacturing Electrolyte Membrane, Catalyst Layer, and Polymer Electrolyte Fuel Cell]
The electrolyte membrane, the catalyst layer, and the polymer electrolyte fuel cell according to the present invention can be manufactured by various methods. For example, an electrolyte membrane containing Ag @ CeO ₂ particles is
(A) Add Ag @ CeO ₂ particles to a solution in which a solid polymer electrolyte is dissolved or dispersed in a solvent,
(B) apply this solution to the surface of the substrate;
(C) It can manufacture by volatilizing a solvent from a coating film.

Also, the catalyst layer containing Ag @ CeO ₂ particles is
(A) Add Ag @ CeO ₂ particles to a catalyst ink in which an electrode catalyst and an electrolyte in the catalyst layer are dissolved or dispersed in a solvent,
(B) apply the catalyst ink to the surface of the substrate;
(C) It can manufacture by volatilizing a solvent from a coating film.

Furthermore, a polymer electrolyte fuel cell containing Ag @ CeO ₂ particles is
(A) preparing an electrolyte membrane and / or a catalyst layer containing Ag @ CeO ₂ particles,
(B) It can manufacture by joining a catalyst layer on both surfaces of an electrolyte membrane.

[6. Action]
The Ag @ CeO ₂ particles behave mainly as inorganic particles, not ions, in a fuel cell environment because they have a core-shell structure in which an Ag core is covered with a CeO ₂ shell. That is, the possibility that the metal ions eluted from the Ag @ CeO ₂ particles and the acid group of the electrolyte form a salt is low. In addition, Ag @ CeO ₂ particles have a decomposition effect of hydrogen peroxide (or an effect as a radical scavenging agent) even in a very small amount, and exhibit such a decomposition effect without being ionized. Therefore, by adding this to the electrolyte membrane and / or the catalyst layer, it is possible to achieve both high proton conductivity and high durability at a high level.

(Examples 1 to 2, Comparative Examples 1 to 7)
[1. Preparation of sample]
[1.1. Examples 1-2]
A perfluoroalkylsulfonic acid resin dispersion having a solid concentration of 21.5 wt% and an EW of 1000 was diluted with 1 propanol and ultrapure water so as to have a concentration of 10 wt%. An appropriate amount of radical scavenger was added to the resin dispersion. As a radical scavenger, Ag @ CeO ₂ particles having an average particle size of 0.1 μm or less were used. The amount of acid group substitution of the radical scavenger was 0.01% (Example 1) or 0.005% (Example 2). FIG. 1 shows an SEM image of Ag @ CeO ₂ particles used in the experiment.

  The resin dispersion to which the radical scavenger was added: 7 g was taken in a 50 mL glass container and subjected to ultrasonic irradiation for 5 minutes. The above dispersion was poured into a flat petri dish having a diameter of 90 mm and placed on a parallel glass table to cover the upper surface with a non-woven fabric. In this state, it was left to stand overnight in a draft chamber to remove the solvent. Thereafter, the flat petri dish was placed in a vacuum dryer, and heating was performed at 80 ° C. × 2 hr + 140 ° C. × 2 hr to form a film. The obtained membrane was punched into a size of 2 cm × 2.4 cm. These membranes were taken on filter paper and vacuum dried at 80 ° C. for 2 hours to determine the dry weight.

[1.2. Comparative Examples 1 and 2]
An electrolyte membrane was produced in the same manner as in Example 1 except that the radical scavenger was not added. The obtained electrolyte membrane was immersed in a silver acetate aqueous solution, and ion exchange was performed with Ag ⁺ . The acid group substitution ratio was 0.1% (Comparative Example 1) or 1.0% (Comparative Example 2).
[1.3. Comparative Example 3]
An electrolyte membrane was produced in the same manner as in Example 1 except that Ag ₂ O particles (manufactured by Wako Pure Chemical Industries, Ltd., average particle diameter: 1 μm) were used as a radical scavenger. The acid group substitution ratio was 1.0%.

[1.4. Comparative Examples 4 to 6]
An electrolyte membrane was produced in the same manner as in Example 1 except that the radical scavenger was not added. The obtained electrolyte membrane was immersed in a cerium nitrate aqueous solution, and ion exchange was performed with Ce ³⁺ . The acid group substitution ratio was 0.1% (comparative example 4), 1.0% (comparative example 5), or 2.0% (comparative example 6).
[1.5. Comparative Example 7]
An electrolyte membrane was produced in the same manner as in Example 1 except that CeO ₂ fine particles (manufactured by Shin-Etsu Chemical Co., Ltd., average particle diameter: 0.1 μm) were used as a radical scavenger. The acid group substitution ratio was 1.0%.
[1.6. Reference example]
An electrolyte membrane was produced in the same manner as in Example 1 except that the radical scavenger was not added.

[2. Test method]
[2.1. Ion exchange by Fe ²⁺ ]
Add ferrous sulfate solution so that 1% of acid group is ion-exchanged with Fe ²⁺ (weight ratio 280 ppm) in a container containing an electrolyte membrane, ion exchange (80 ° C. × 8 hr), and warm water Rinsing (80 ° C. × 2 hr × 4 times) was performed.

[2.2. Measurement of FER]
The treated membrane was put on filter paper and vacuum dried at 80 ° C. for 2 hours. The dried film was placed in a dropping hydrogen peroxide solution vaporization type testing apparatus, and a hydrogen peroxide vapor exposure test was conducted. The conditions for the exposure test were: temperature: 105 ° C., exposure time: 5 hours, hydrogen peroxide concentration: 3 wt%, dropping rate: 0.12 mL / min, diluted N ₂ flow rate: 0.3 L / min.
100 mL of ultrapure water was put in advance in a 500 mL recovery container, and the exposed hydrogen peroxide vapor was introduced into the recovery container to collect the water-soluble deteriorated product (mainly HF). The amount of dissolved F ions in the recovered water was determined with an ion meter, and the amount of F discharged per unit area FER (μg / cm ² / h) was determined from the weight of the recovered water, the test membrane area and the test time.

[3. result]
Table 1 shows the F emissions (FER). Further, FIG. 2 shows the relationship between the acid group substitution rate and the F discharge amount (FER). The following can be understood from Table 1 and FIG.

(1) When Ag @ CeO ₂ particles are added as a radical scavenger, the addition amount is 1/10 to 1/20 of the conventional radical scavenger (acid group substitution rate is 0.01 to 0.005%) Even in comparison with the reference example, FER was significantly reduced.
(2) When 1% of Ag ⁺ was added as a radical scavenger, FER was significantly reduced. However, when the acid group substitution rate reached 0.1%, FER increased.
(3) Ag ₂ O is less effective in reducing F emissions than Ag ⁺ .
(4) When Ce ³⁺ is added as a radical scavenger, the larger the substitution rate of the acid group, the lower the amount of F emission, but the effect is smaller than that of Ag ⁺ .
(5) The addition of CeO ₂ rather increased the FER.

  As mentioned above, although embodiment of this invention was described in detail, this invention is not limited at all to the said embodiment, A various change is possible within the range which does not deviate from the summary of this invention.

  The polymer electrolyte fuel cell according to the present invention can be used as an on-vehicle power source, a stationary generator, or the like.

Claims (9)

An electrolyte membrane comprising a solid polymer electrolyte,
An anode catalyst layer bonded to one surface of the electrolyte membrane;
A cathode catalyst layer bonded to the other surface of the electrolyte membrane;
Ag @ CeO ₂ particles added to any one or more selected from the group consisting of the electrolyte membrane, the anode catalyst layer, and the cathode catalyst layer,
The above-mentioned Ag @ CeO ₂ particles have a core-shell structure in which the surface of an Ag core is covered with a CeO ₂ shell. The polymer electrolyte fuel cell according to claim 2, wherein an acid group substitution ratio of the Ag @ CeO ₂ particles is 0.001% or more and 2.0% or less. The polymer electrolyte fuel cell according to claim 1, wherein an average particle size of the Ag @ CeO ₂ particles is 0.5 μm or less. Solid polymer electrolyte,
And Ag @ CeO ₂ particles added in the solid polymer electrolyte,
The Ag @ CeO ₂ particles are an electrolyte membrane having a core-shell structure in which the surface of an Ag core is covered with a CeO ₂ shell. The electrolyte membrane according to claim 4, wherein an acid group substitution ratio of the Ag @ CeO ₂ particles is 0.001% or more and 2.0% or less. The electrolyte membrane according to claim 4, wherein an average particle size of the Ag @ CeO ₂ particles is 0.5 μm or less. An electrode catalyst,
An electrolyte in a catalyst layer coating the surface of the electrode catalyst;
Ag @ CeO ₂ particles added between the electrode catalysts or in the electrolyte in the catalyst layer,
The Ag @ CeO ₂ particles have a core-shell structure in which the surface of an Ag core is covered with a CeO ₂ shell. The catalyst layer according to claim 7, wherein an acid group substitution ratio of the Ag @ CeO ₂ particles is 0.001% or more and 2.0% or less. The catalyst layer according to claim 7 or 8, wherein an average particle size of the Ag @ CeO ₂ particles is 0.5 μm or less.

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