JP2010218914A - Anode for fuel cell, membrane electrode assembly, and fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anode for a fuel cell from which a high output fuel cell can be obtained.
SOLUTION: A supported catalyst containing a conductive support material and catalyst fine particles supported on the conductive support material, compounded at a weight W _C , silicon oxide with a weight W _SiO2 , and proton conductive inorganic oxide with a weight W _SA A composite of a silicon oxide-containing proton conductive inorganic oxide having a total weight of W _{SA + SiO2} and a basic polymer of weight W _BP , and a proton conductive organic polymer binder blended with a weight W _P It comprises the electrode catalyst layer containing.
[Selection figure] None

Description

  The present invention relates to an anode for a fuel cell, a membrane electrode assembly, and a fuel cell.

  As an electrode for a fuel cell using a proton conductive inorganic oxide and a proton conductive organic polymer binder, a sulfuric acid-supported metal oxide having a solid super strong acid property in the proton conductive inorganic oxide is known (for example, patent) Reference 1). Such an electrode is unstable as a proton conductor of a fuel cell that generates water during power generation, particularly a fuel cell that uses liquid fuel.

  On the other hand, the present inventors have proposed an electrode for a fuel cell containing an oxide carrier such as Ti, oxide particles such as W, and a binder that binds these particles (see, for example, Patent Document 2). In an electrode catalyst layer in which an oxide such as Ti or W (proton conductive inorganic oxide), a Pt catalyst, and a binder are combined, continuity between proton conductive inorganic oxides or continuity between Pt catalyst support materials. The properties are inhibited by the binder. Moreover, the binder adhering to the surface of the proton conductive inorganic oxide or the Pt catalyst hinders the supply of water to the proton conductive inorganic oxide. In this case, the water necessary for the generation of protons is insufficient, the supply of air to the Pt catalyst is insufficient, and the three-phase interface where the electrode reaction occurs is insufficient.

  Although proton conductors have been extensively developed to improve the proton conductivity and electrode reaction of the electrode catalyst layer, there is still room for improvement in performance.

  In addition, conventional proton conductive inorganic oxides have a tendency that nano-sized particles are fused to each other at the time of synthesis to cause grain growth, the specific surface area is decreased, and effective proton conductive sites are decreased. As a result, the proton conductivity was lowered, so that the output of the fuel cell as a whole could not be sufficiently increased.

JP 2004-158261 A JP 2006-32287 A

  An object of this invention is to provide the anode for fuel cells from which a high output fuel cell is obtained.

An anode for a fuel cell according to an aspect of the present invention includes a supported catalyst that includes a conductive support material and catalyst fine particles supported on the conductive support material, and is blended at a weight W _C.
Complex of the silicon oxide-containing proton-conductive inorganic oxide of silicon oxide and the weight W total weight containing a proton-conductive inorganic oxides _SA W _{SA + SiO2} weight W _SiO2, a basic polymer having a weight W _BP and characterized by including an electrode catalyst layer containing a proton conductive organic polymer binder which is at a weight W _P.

A membrane electrode assembly according to an aspect of the present invention is a membrane electrode assembly comprising a fuel electrode, an oxidant electrode, and an electrolyte membrane disposed between the fuel electrode and the oxidant electrode,
The fuel electrode has the fuel cell anode described above.

  A fuel cell according to one embodiment of the present invention includes the above-described membrane electrode assembly.

  ADVANTAGE OF THE INVENTION According to this invention, the anode for fuel cells from which a high output fuel cell is obtained, a membrane electrode assembly using the same, and a fuel cell are provided.

The side view which shows typically the fuel cell concerning one Embodiment.

  Embodiments of the present invention will be described below.

  The anode for a fuel cell according to the present embodiment includes a supported catalyst, a composite of a proton conductive inorganic oxide and a basic polymer, and an electrode catalyst layer including a proton conductive organic polymer binder.

  The supported catalyst includes a conductive support and catalyst fine particles supported on the conductive support.

  Examples of the conductive carrier include carbon black, but are not limited thereto. Any carrier having sufficient conductivity and stability can be used. Recently, nanocarbon materials, such as fibers, tubes, coils, etc., have been developed. Furthermore, you may use the ceramic material which has electroconductivity as a support body.

  As the catalyst fine particles, any anode catalyst for a fuel cell can be used. Pt and Ru are generally used as the main catalyst elements. Further, for the purpose of enhancing the catalytic activity, Fe, Co, Ni, Pd, Os, Ir, etc. may be added as a promoter component. Usually, an alloy of Pt and Ru is widely used. Pt is effective for the oxidation reaction of hydrogen and the dehydrogenation reaction of organic fuel, and Ru is extremely effective for suppressing CO poisoning. If the amount of Ru is excessively small, sufficient activity may not be obtained. It is desirable that Ru is contained in at least 1 mol% or more in the catalyst fine particles.

  The catalyst fine particles can be supported on the conductive support using, for example, a solution method such as an impregnation method, a precipitation method, and a colloid method. In the case of a metal that reacts with water and is oxidized, it can be directly supported on the conductive support by sputtering, vapor deposition or the like. According to such a method, it is easy to produce a catalyst having a metal bond. The catalyst may be supported on the conductive support by any method, but is not limited thereto.

  Since the higher activity is obtained as the average particle size of the catalyst fine particles is smaller, the average particle size of the catalyst fine particles is preferably 10 nm or less. If the average particle size is too small, it is difficult to control the catalyst synthesis process and the catalyst synthesis cost becomes high. Therefore, it is desired that the average particle size be at least about 0.5 nm.

  As the catalyst fine particles, fine particles having an average particle diameter of 10 nm or less can be used alone. Alternatively, an aggregate (secondary particle) of primary particles made of such fine particles may be used. The average particle diameter of the catalyst fine particles can be calculated from the half width of the peak by XRD measurement using the Scherrer equation.

  The proton conductive inorganic oxide includes an oxide carrier and oxide particles supported on the surface of the oxide carrier. The oxide support can include, for example, at least one first element selected from the group consisting of Ti, Zr, and Sn, and the oxide particles are selected from the group consisting of W, Mo, and V At least one second element can be included.

Specific examples of the oxide carrier containing the first element include TiO ₂ , ZrO ₂ , and SnO _2. Specific examples of the oxide particles containing the second element include: WO _2, MoO _2, and the like V ₂ O ₅ and the like. When the oxide particles are supported on the surface of such an oxide carrier, Lewis acid points are generated in the structure of the oxide particles. It is presumed that when this Lewis acid point is hydrated, it becomes a Bronsted acid point and a proton conduction field is formed. In addition, when the proton conductive inorganic oxide has an amorphous structure, the generation of Lewis acid points is promoted.

  The proton conductive inorganic oxide can reduce the number of molecules of entrained water necessary for proton transfer in addition to the proton generation reaction by the Lewis acid point. For this reason, it becomes possible to obtain high proton conductivity with a small amount of water molecules present on the surface of the proton conductive inorganic oxide, and a large amount of power generation can be obtained without strict water management during power generation. .

  The oxide particles containing the second element may have water solubility due to fluctuations in water solubility depending on the element and pH environment. On the other hand, the oxide carrier containing the first element has low water solubility. By supporting the oxide particles on an oxide carrier having low water solubility, it is possible to suppress dissolution of the oxide particles in water. As a result, the stability of the proton conductive inorganic oxide to water and liquid fuel is improved as compared with the case where the oxide particles are present alone. Also, contamination of other fuel cell materials and devices by ions of the eluted oxide particles can be avoided.

  Therefore, a fuel cell having high reliability over a long period can be obtained by using such a proton conductive inorganic oxide. Furthermore, an inexpensive oxide carrier can be used as a base material, and the manufacturing cost of the battery can be suppressed.

  Moreover, silicon oxide is supported on the surface of the proton conductive inorganic oxide. Silicon oxide may be supported as fine particles or may be deposited in layers on the surface of the proton conductive inorganic oxide. In any state, as long as silicon oxide is supported on the surface of the proton conductive inorganic oxide, it is possible to prevent the proton conductive inorganic oxide from fusing together and grain growth.

  The fact that the oxide carrier containing the first element and the oxide particles containing the second element and the silicon oxide are supported on the oxide carrier containing the first element are, for example, transmission electron microscope (TEM), X-ray diffraction (XRD), X-ray photoelectron It can be confirmed by instrumental analysis such as spectroscopy (XPS).

  The oxide carrier containing the first element can be synthesized by any method. For example, a vapor phase method in which a gas containing a first element is decomposed to produce an oxide, or a sol-gel method using a solution containing a first element or a metal alkoxide as a raw material can be given. The oxide carrier may be a complex oxide containing a plurality of types of metal elements.

  When Sn is used as the first element, the proton conductivity can be sufficiently increased. In addition, when Ti is used as the first element, high proton conductivity can be obtained while suppressing the manufacturing cost. The oxide carrier can have various shapes such as a particle shape, a fiber shape, a flat plate shape, a layer shape, and a porous shape, and the shape is not particularly limited. In the oxide carrier, the surface acts as a proton conduction site. For this reason, sufficient proton conduction sites can be obtained by using nano-sized fine particle oxide as an oxide carrier.

  The oxide particles containing the second element can be supported on the surface of the oxide carrier containing the first element, for example, by the following method. As the solvent, for example, water or alcohol can be used. First, a solution in which a substance containing the second element is dissolved in a solvent, for example, an acidic or alkaline aqueous solution such as chloride, nitrate, hydrogen acid, or oxo acid salt, or an alcohol solution of a metal alkoxide is prepared. Here, the oxide carrier containing the first element is dispersed, and the solvent is removed. Thereby, after supporting the raw material of the oxide particles containing the second element, heat treatment is performed to obtain oxide particles.

  The oxide particles containing the second element may be supported on the oxide carrier in the state of a composite oxide containing a plurality of elements. The solvent is generally removed by heating, but is not limited thereto. The solvent can be removed under reduced pressure without heating. Furthermore, the solvent may be removed by simultaneously performing heating and decompression.

  The effect is exhibited if the oxide particles containing the second element are supported on at least a part of the surface of the oxide carrier containing the first element. For example, it may be a layered material that is scattered on the surface of the oxide support or covers the surface of the oxide support. The oxide particles may be supported on the surface of the oxide carrier, and the crystallinity of the oxide particles or the oxide carrier is not limited.

  Considering the promotion of Lewis acid point generation, the possibility of contributing to the improvement of acidity, the reduction of the manufacturing cost, and the ease of the manufacturing process, it is desirable that both the oxide particles and the oxide support are amorphous. . More preferably, the oxide particles are amorphous and the oxide support is crystalline. On the contrary, it is also possible to use both the oxide particles and the oxide support in the crystal form, or the oxide particles are in the crystal form and the oxide support is used in the amorphous form.

  The state in which the raw material of the oxide particles is supported on the surface of the oxide carrier is the proton conductive inorganic oxide precursor particles. When the solvent is removed and the oxide particles are supported on the surface of the oxide carrier, the precursor particles are strongly aggregated into coarse aggregates. It is not easy to release this aggregation state, leading to an increase in manufacturing cost. On the other hand, when the heat treatment is continued in the agglomerated state, the oxide carriers are fused to cause grain growth.

  In particular, when the oxide carrier is a fine particle such as a nanoparticle, grain growth tends to occur at a temperature considerably lower than the melting point of the oxide carrier. When grain growth occurs, the specific surface area of the particles decreases and proton conduction sites decrease. As a result, the cell resistance increases, and the tendency that a high output cannot be obtained as a whole battery becomes strong.

  In this embodiment, when the oxide carrier is dispersed in a solution in which the substance containing the second element is dissolved, the silicon oxide particles are added, and then the solvent is removed. As a result, silicon oxide particles adhere to the surface of the oxide support. Alternatively, silicon oxide dissolved in the solution can be deposited and deposited on the surface of the oxide support, and the silicon oxide can be supported on the surface of the oxide support. By performing the heat treatment in the state where the silicon oxide particles are added in this manner, it is possible to suppress fusion of the oxide carrier and grain growth. That is, the aggregation of the proton conductive inorganic oxide precursor particles is released.

  The mechanism of this phenomenon is considered as follows. This is because silicon oxide is a hardly sinterable oxide, and the presence of silicon oxide between the aggregated oxide carrier particles suppresses fusion between the oxide carriers. In the proton conductive inorganic oxide synthesized by the above method, the oxide particles are supported not only on the surface of the oxide carrier but also on the surface of the silicon oxide particles. It is difficult to separate and remove only the oxide particles supported on the surface of the silicon oxide particles.

  As described above, silicon oxide is a hardly sinterable oxide, and oxide particles are difficult to bond. For this reason, oxide particles may elute during power generation, and the components of the fuel cell may be contaminated by the components. In order to avoid such an inconvenience, it is desired to remove the oxide particles supported on the surface of the silicon oxide particles by washing in advance with water or hot water.

  By washing, a proton conductive inorganic oxide composed of an oxide carrier and oxide particles and silicon oxide particles supported on the surface thereof is obtained. Silicon oxide is a hardly sinterable oxide, and the bond with the oxide carrier may be weak depending on the synthesis conditions. In this case, the silicon oxide particles can be removed by washing with water or hot water in advance.

The weight (W _SiO2 ) of silicon oxide (SiO ₂ ) supported on the surface is preferably 0.1 to 0.5 times the weight (W _SA ) of the proton conductive inorganic oxide (SA). That is, the weight ratio (W _SiO2 / W _SA ) between the silicon oxide particles and the proton conductive inorganic oxide is preferably in the range of 0.1 to 0.5. Within this range, a grain growth suppressing effect can be sufficiently obtained without causing a decrease in proton conductivity or electron conductivity.

  It is preferable that the average particle diameter of silicon oxide does not exceed the average particle diameter of the oxide carrier. Considering the ease of handling and the effect of suppressing grain growth, the average particle diameter of silicon oxide is preferably in the range of 1 to 15 nm. When the average particle size of silicon oxide is smaller than 1 nm, the supported amount increases to obtain the effect of suppressing grain growth of the proton conductive inorganic oxide, and the silicon oxide masks the proton generation site on the surface of the proton conductive inorganic oxide. Is done. As a result, proton conduction resistance may increase. When the average particle diameter of silicon oxide is larger than 15 nm, uniform synthesis control becomes difficult. In view of availability, the range of 3 to 10 nm is more preferable. The crystallinity and shape of the particles are not particularly limited, and an appropriate one may be selected in consideration of the cost.

The specific surface area of the proton conductive inorganic oxide is preferably in the range of 10 to 2000 m ² / g. When the specific surface area exceeds 2000 m ² / g, it is difficult to control handling and uniform synthesis, and when it is less than 10 m ² / g, sufficient proton conductivity cannot be obtained. The specific surface area of the proton conductive inorganic oxide is the specific surface area per unit weight of the proton conductive inorganic oxide, and can be measured using the BET method.

  In the proton conductive inorganic oxide, the atomic ratio between the second element (M2) contained in the oxide particles and the first element (M1) contained in the oxide carrier (number of M2 atoms / M1). Is preferably in the range of 0.0001-5. When the atomic ratio (number of M2 atoms / number of M1 atoms) is less than 0.0001, the supported amount is small and the proton conduction field is small. On the other hand, if it exceeds 5, the supported amount is too large and the proton conduction field is covered with oxide particles. In either case, sufficient proton conductivity may not be obtained. The atomic ratio (number of M2 atoms / number of M1 atoms) is more preferably in the range of 0.01 to 1.

  The proton conductive inorganic oxide can be obtained, for example, by supporting a precursor of oxide particles on an oxide carrier and then heat-treating it in an oxidizing atmosphere such as the air. It is preferable that the temperature of heat processing shall be 200-1000 degreeC. When the temperature is lower than 200 ° C., the precursor of the oxide particles hardly becomes an oxide, and a sufficient chemical bond is not formed between the oxide carrier and the oxide particles. On the other hand, when the temperature exceeds 1000 ° C., grain growth occurs in addition to the fusion between the particles, and the specific surface area decreases. In either case, there is a possibility that sufficient proton conductivity cannot be obtained. The heat treatment temperature is more preferably 400 to 800 ° C. In addition, when the process is performed at a high temperature around 1000 ° C., the heat treatment time can be shortened.

It is desirable that the proton conductive inorganic oxide exhibits a solid superacidity. The degree of proton dissociation can be expressed as acid strength, and the acid strength of solid acid is expressed as Hammett acidity function H ₀ . For example, the acidity (H ₀ ) of sulfuric acid (100 wt%) is −11.93, and it is more preferable that the proton-conductive inorganic oxide exhibits a solid superacidity where H ₀ <−11.93. Further, the proton conductive inorganic oxide, by optimizing the synthesis method, it is possible to increase the acidity to H ₀ = -20.00. Therefore, it is desirable to use a proton conductive inorganic oxide having an acid strength in the range of −20.00 <H ₀ <−11.93.

  The acidity of the solid superacid can be measured using, for example, an ammonia temperature rising desorption method (TPD) method. Specifically, ammonia gas is adsorbed on the solid acid sample, and the sample is heated. Solid acidity is analyzed by detecting the desorption amount and desorption temperature of the desorbed ammonia.

  The proton conductive inorganic oxide is used in the anode of this embodiment as a complex with a basic polymer.

  The basic polymer is a polymer having a functional group showing basicity. As the functional group, for example, it is desirable to include at least one selected from the group consisting of an amino group, a pyridyl group, and an imidazole group. Specific examples of the basic polymer containing such a functional group include, but are not limited to, polyethyleneimine, polyvinylamine, polyallylamine, polyvinylpyridine, and polyvinylimidazole.

  Since the proton conductive inorganic oxide is an acidic substance, a complex with a basic polymer is formed by acid-base interaction.

  A complex of a basic polymer and a proton conductive inorganic oxide is prepared by, for example, dissolving a basic polymer in a solvent to obtain a solution, and dispersing the proton conductive inorganic oxide in the solution therein. can do. By being complexed, the basic polymer dissolved in the solvent is deposited on the surface of the proton conductive inorganic oxide to form an aggregate of the proton conductive inorganic oxide.

  Protons generated from the proton conductive inorganic oxide transition to a basic functional group of the basic polymer, and the basic polymer takes a cation type. Furthermore, the proton of the basic polymer again transitions to a proton conductive inorganic oxide or a proton conductive binder.

  Conventionally, some proton conductive inorganic oxides isolated inside the catalyst layer have been difficult to contribute to power generation. However, by compositing a proton conductive inorganic oxide and a basic polymer, a new proton conduction path has been established, and the output of the fuel cell can be increased.

The weight ratio of the weight (W _BP) of the weight of the proton conductive inorganic oxide _(SA) (W SA) and basic polymer _{(BP) (W BP / W} SA) is 0.001 to 0.1 It is preferable to be within the range. Within this range, a sufficient output can be obtained without any inconvenience.

  In addition to the supported catalyst and the composite of the proton conductive inorganic oxide and the basic polymer described above, the electrode catalyst layer of the anode for the fuel cell according to this embodiment contains a proton conductive organic polymer binder. The

  Since proton conductivity is high, an organic polymer material having a sulfonic acid group is preferable as the proton conductive organic polymer binder. Examples thereof include fluororesins having a sulfonic acid group such as Nafion (trade name: manufactured by DuPont), Flemion (trade name: manufactured by Asahi Kasei Co., Ltd.), and Ashiburek (trade name: manufactured by Asahi Glass Co., Ltd.). The organic polymer material having a sulfonic acid group is not particularly limited.

In the electrode catalyst layer according to the present embodiment, the supported catalyst (C) is contained by weight (W _C ). The weight (W _SiO2 ) of silicon oxide and the weight (W _SA ) of proton conductive inorganic oxide are collectively referred to as silicon oxide-containing proton conductive inorganic oxide. The weight of the silicon oxide-containing proton conductive inorganic oxide is (W _{SA + SiO2} ). The weight ratio (W _{SA + SiO 2} / W _C ) is preferably in the range of 0.05 to 0.5. Within this range, the proton conductivity and the electron conductivity are not lowered, and a sufficient output can be obtained.

The proton conductive organic polymer binder (P) is contained by weight (W _P ), and the weight ratio (W _P / W _{SA +} ) to the weight (W _{SA + SiO 2} ) of the silicon oxide-containing proton conductive inorganic oxide. _SiO2 ) is preferably in the range of 1-32. If it is within this range, the proson conductivity and the electron conductivity will not be lowered, and a sufficient output can be obtained. Thus, by setting the weight ratio of the supported catalyst, the composite of the proton conductive inorganic oxide and the basic polymer, and the proton conductive organic polymer binder within a predetermined range, the characteristics of the fuel cell are remarkably improved. It was. This is a finding obtained by the present inventors.

  The membrane electrode assembly according to the present embodiment is configured using the anode as described above. That is, the membrane electrode assembly according to the embodiment includes an anode, a cathode, and a proton conductive membrane disposed between the anode and the cathode. The fuel cell according to the present embodiment includes this membrane electrode assembly.

  As schematically shown in the cross-sectional (side) view of FIG. 1, a fuel cell according to an embodiment includes a membrane electrode assembly (hereinafter referred to as MEA) 12 and a cathode holder having an oxidant gas supply groove 8. 9 and an anode holder 11 having a fuel supply groove 10.

  The MEA 12 includes an anode (fuel electrode) 2, a cathode (oxidant electrode) 3, and a proton conductive membrane 1. The anode 2 includes a diffusion layer 4 and an anode catalyst layer 5 stacked thereon, and the cathode 3 includes a diffusion layer 6 and a cathode catalyst layer 7 stacked thereon. The anode 2 and the cathode 3 are laminated so that the anode catalyst layer 5 and the cathode catalyst layer 7 face each other with the proton conductive membrane 1 interposed therebetween.

  The anode catalyst layer 5 can be produced using a supported catalyst, a proton conductive inorganic oxide, a basic polymer, and a proton conductive organic polymer binder as described above. In addition to these components, an aprotic conductive binder may further be contained. In this case, the form of the catalyst layer can be maintained well. Examples of the non-proton conductive binder include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP), and tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin (PFA). Can be mentioned.

  In order to avoid a decrease in output due to an increase in cell resistance or the like, it is desirable that the content of the aprotic conductive binder be 10% or less of the total weight of the anode catalyst layer 5. The content of the aprotic conductive binder is more preferably 5% or less of the total weight of the anode catalyst layer 5.

  The cathode catalyst layer 7 contains a cathode catalyst and a proton conductive organic polymer binder. As the cathode catalyst, for example, Pt can be used. The catalyst can be used by being supported on a carrier, but it may be used without being supported.

  A conductive porous sheet can be used for the diffusion layers 4 and 6. As the conductive porous sheet, for example, a sheet formed of a material having air permeability or liquid permeability such as carbon cloth or carbon paper can be used.

  The anode and the cathode can be produced by a known method. For example, the above-described constituent materials are mixed in an organic solvent such as water or alcohol and dispersed to form a catalyst slurry, and this slurry is applied to the conductive porous sheet, dried, and fired as necessary to form a catalyst layer. Let The dispersion method is not particularly limited, and examples thereof include a dissolver and a ball mill.

The proton conducting membrane and the electrode (anode and cathode) can be joined using an apparatus that can be heated and / or pressurized. Generally, thermocompression bonding (joining) is performed by a hot press machine. The press temperature in that case should just be more than the glass transition temperature of the proton conductive polymer used as a binder, and is generally 100-400 degreeC. The pressing pressure depends on the hardness of the electrode used, but is usually 5 to 200 kg / cm ² (0.49 to 19.6 MPa).

  The fuel cell according to this embodiment includes the above-described MEA, means for supplying fuel to the anode, and means for supplying an oxidant to the cathode. The number of MEAs to be used may be one or more. By using multiple, higher electromotive force can be obtained. As the fuel, methanol, ethanol, formic acid, or an aqueous solution containing one or more selected from these can be used.

(No. 1)
First, a proton conductive inorganic oxide was synthesized. A solution was prepared by dissolving 1.5 g of vanadium oxide (V ₂ O ₅ ) in 100 mL of aqueous ammonia. 9 g of titanium oxide (TiO ₂ ) was dispersed in 500 ml of distilled water, and the previously prepared solution containing vanadium was mixed. In the obtained mixed solution, 3.0 g of silicon oxide (SiO ₂ ) particles were dispersed. The average particle diameter of the SiO ₂ particles is about 10 nm. The mixed solution was heated to 80 ° C. with constant stirring. After removing water at an evaporation rate of 100 ml / hour, the mixture was kept in a dryer at 100 ° C. for 12 hours to obtain a powder.

  The powder was pulverized in an agate mortar, then housed in an alumina crucible, and heated to 500 ° C. at a temperature increase rate of 100 ° C./hour. Further, by holding at 500 ° C. for 4 hours, a mixture of vanadium oxide-supported titanium oxide and vanadium oxide-supported silicon oxide was obtained.

This mixture was washed with hot water to obtain a proton conductive inorganic oxide (silicon oxide-containing proton conductive inorganic oxide) on which SiO ₂ particles were supported. The first element and the second element in the proton conductive inorganic oxide are titanium and vanadium, respectively.

  The silicon oxide-containing proton conductive inorganic oxide was subjected to X-ray diffraction measurement. All of the observed diffraction peaks are attributed to titanium oxide, and it was confirmed that vanadium oxide and silicon oxide have an amorphous structure.

  The atomic ratio (number of M2 atoms / number of M1 atoms) in the proton conductive inorganic oxide was determined by inductively coupled plasma emission spectroscopy (ICP-AES). The solid acidity was determined by an acid indicator or ammonia temperature programmed desorption (TPD) method. The results obtained are summarized in Table 1 below.

  Polyvinylpyridine was prepared as a basic polymer and dissolved in 2-propanol to prepare a 1 wt% solution. 0.5 g of the obtained solution and 0.5 g of the above-described proton conductive inorganic oxide were mixed, 3 g of 2-propanol was further added, and the mixture was well stirred and dispersed. As a result, 4 g of a dispersion in which a complex of a proton conductive inorganic oxide and a basic polymer was dispersed in 2-propanol was prepared.

  4 g of the obtained dispersion, 2 g of PtRu supported catalyst, 0.5 g of proton conductive inorganic oxide, 12.5 g of 20 wt% Nafion solution (trade name: manufactured by DuPont), 3 g of water, and 3 g of 1-propanol The slurry for anode was prepared by thoroughly stirring and dispersing.

The obtained slurry was applied to a water-repellent carbon paper (350 μm, manufactured by Toray Industries, Inc.) with a control coater and dried. By the above method, an anode having a noble metal catalyst loading density of 1 mg / cm ² was produced.

For the obtained anode, the weight ratio (W _{SA + SiO 2} / W _C ) between the supported catalyst (C) and the silicon oxide-containing proton conductive inorganic oxide (SA + SiO ₂ ), the silicon oxide-containing proton conductive inorganic oxide (SA + SiO ₂ ). ₂ ) and the proton conductive organic polymer binder (P) in the weight ratio (W _P / W _{SA +} SiO ₂ ), the weight ratio between the silicon oxide (SiO ₂ ) particles and the proton conductive inorganic oxide (SA) (W _{SiO 2} / W _SA ) and the weight ratio (W _BP / W _SA ) between the basic polymer (BP) and the proton conductive inorganic oxide ( _SA ) are determined and summarized in Table 2 below. These weight ratios were calculated from the charged composition.

  Furthermore, by changing the type and blending amount of the components as follows, each method is used for No. 2 to 27 anodes were prepared.

(No. 2)
1.5 g of vanadium oxide (V ₂ O ₅ ) was changed to 2.4 g of molybdenum oxide (MoO ₃ ), the amount of silicon oxide (SiO ₂ ) particles was changed to 3.2 g, and the firing temperature was 600 ° C. No. except for change to No. 1 is the same method.

(No. 3)
1.5 g of vanadium oxide (V ₂ O ₅ ) is changed to 4.0 g of tungsten oxide (WO ₃ ), the amount of silicon oxide (SiO ₂ ) particles is changed to 3.5 g, and the firing temperature is 700 ° C. No. except for change to No. 1 is the same method.

(No. 4)
No. 9 except that 9.0 g of titanium oxide (TiO ₂ ) was changed to 13 g of zirconium oxide (ZrO ₂ ) and the amount of silicon oxide (SiO ₂ ) particles was changed to 4.2 g. 1 is the same method.

(No. 5)
No. 9 except that 9.0 g of titanium oxide (TiO ₂ ) was changed to 13 g of zirconium oxide (ZrO ₂ ) and the amount of silicon oxide (SiO ₂ ) particles was changed to 4.2 g. 2 is the same method.

(No. 6)
No. 9 except that 9.0 g of titanium oxide (TiO ₂ ) was changed to 13 g of zirconium oxide (ZrO ₂ ) and the amount of silicon oxide (SiO ₂ ) particles was changed to 4.7 g. 3 is the same method.

(No. 7)
No. 9 except that 9.0 g of titanium oxide (TiO ₂ ) was changed to 17 g of tin oxide (SnO ₂ ) and the amount of silicon oxide (SiO ₂ ) particles was changed to 5.4 g. 1 is the same method.

(No. 8)
No. 9 except that 9.0 g of titanium oxide (TiO ₂ ) was changed to 17 g of tin oxide (SnO ₂ ) and the amount of silicon oxide (SiO ₂ ) particles was changed to 5.6 g. 2 is the same method.

(No. 9)
No. 9 except that 9.0 g of titanium oxide (TiO ₂ ) was changed to 17 g of tin oxide (SnO ₂ ) and the amount of silicon oxide (SiO ₂ ) particles was changed to 5.9 g. 3 is the same method.

(No. 10)
The compounding amount of the proton conductive inorganic oxide was changed to 0.1 g, the compounding amount of the 20 wt% Nafion (trade name: DuPont) solution was changed to 15.7 g, and the compounding quantity of the 1 wt% polyvinylpyridine solution was changed to 0. .No. 1 is the same method.

(No. 11)
The blending amount of the proton conductive inorganic oxide is changed to 1.0 g, the blending amount of the 20 wt% Nafion (trade name: DuPont) solution is changed to 6.4 g, and the blending quantity of the 1 wt% polyvinylpyridine solution is 1 No. except that it was changed to 0.0g. 1 is the same method.

(No. 12)
No. 1 except that the amount of silicon oxide (SiO ₂ ) particles was changed to 1.0 g. 1 is the same method.

(No. 13)
No. 1 except that the amount of silicon oxide (SiO ₂ ) particles was changed to 5.0 g. 1 is the same method.

(No. 14)
No. 1 except that the amount of the 1 wt% polyvinyl pyridine solution was changed to 0.05 g. 1 is the same method.

(No. 15)
No. 1 except that the blending amount of the 1 wt% polyvinyl pyridine solution was changed to 5.0 g. 1 is the same method.

(No. 16)
No. 5 except that 0.5 g of 1 wt% polyvinyl pyridine solution was changed to 0.5 g of 1 wt% polyallylamine aqueous solution. 1 is the same method.

(No. 17)
No. 5 except that 0.5 g of 1 wt% polyvinyl pyridine solution was changed to 0.5 g of 1 wt% polyvinyl imidazole aqueous solution. 1 is the same method.

(No. 18)
The compounding amount of the proton conductive inorganic oxide was changed to 0.05 g, the compounding amount of the 20 wt% Nafion (trade name: manufactured by DuPont) solution was changed to 4.39 g, and the compounding quantity of the 1 wt% polyvinylpyridine solution was changed to 0. No. 1 is the same method.

(No. 19)
The blending amount of the proton conductive inorganic oxide is changed to 1.5 g, the blending amount of the 20 wt% Nafion (trade name: manufactured by DuPont) solution is changed to 26.2 g, and the blending amount of the 1 wt% polyvinylpyridine solution is 1 No. except for changing to 5g. 1 is the same method.

(No. 20)
The blending amount of the proton conductive inorganic oxide is changed to 1.5 g, the blending amount of the 20 wt% Nafion (trade name: manufactured by DuPont) solution is changed to 3.1 g, and the blending amount of the 1 wt% polyvinylpyridine solution is set to 1. No. except for changing to 5g. 1 is the same method.

(No. 21)
The compounding amount of the proton conductive inorganic oxide was changed to 0.05 g, the compounding amount of the 20 wt% Nafion (trade name: manufactured by DuPont) solution was changed to 10.3 g, and the compounding quantity of the 1 wt% polyvinylpyridine solution was changed to 0. No. 1 is the same method.

(No. 22)
No. 1 except that the amount of silicon oxide (SiO ₂ ) particles was changed to 0.1 g. 1 is the same method.

(No. 23)
No. 1 except that the amount of silicon oxide (SiO ₂ ) particles was changed to 7.0 g. 1 is the same method.

(No. 24)
The compounding amount of the proton conductive inorganic oxide was changed to 1.0 g, the compounding amount of the 20 wt% Nafion (trade name: DuPont) solution was changed to 15.0 g, and the compounding quantity of the 1 wt% polyvinylpyridine solution was changed to 0. No. 1 is the same method.

(No. 25)
The compounding amount of the proton conductive inorganic oxide was changed to 0.1 g, the compounding amount of the 20 wt% Nafion (trade name: manufactured by DuPont) solution was changed to 10.5 g, and the compounding quantity of the 1 wt% polyvinylpyridine solution was changed to 2 No. except for changing to 5g. 1 is the same method.

(No. 26)
No. except that 0.5 g of 1 wt% polyvinylpyridine solution is not used. 1 is the same method.

No. Regarding the proton conductive inorganic oxides used in Nos. 2 to 26, 1 was used to determine the atomic ratio (number of M2 atoms / number of M1 atoms) and solid acidity. The results are summarized in Table 1 below.

Furthermore, no. For each of the anodes 2 to 26, no. 1, the weight ratio (W _{SA +} SiO ₂ / W _C ) between the supported catalyst (C) and the SiO ₂ -containing proton conductive inorganic oxide (SA + SiO ₂ ), the SiO ₂ -containing proton conductive inorganic oxide ( SA + SiO ₂ ) and proton conductive organic polymer binder (P) in weight ratio (WP / W _{SA +} SiO ₂ ), SiO ₂ particles (SiO ₂ ) and proton conductive inorganic oxide (SA) in weight ratio (W _{SiO 2} / W _SA ) and the weight ratio (W _BP / W _SA ) between the basic polymer (BP) and the proton conductive inorganic oxide ( _SA ) were determined. The results are summarized in Table 2 below.

(No. 27)
3 g of PtRu supported catalyst, 8 g of pure water, 15 g of 20 wt% Nafion (trade name: manufactured by DuPont) solution, and 10 g of ethanol were sufficiently stirred and dispersed to obtain a slurry. The above slurry was applied to a carbon paper (thickness 350 μm, manufactured by Toray Industries, Inc.) subjected to water repellent treatment using a control coater and dried to prepare an anode. The loading density of the noble metal catalyst in the obtained anode was 1 mg / cm ² .

  No. Using each of the anodes 1 to 27, a membrane electrode assembly was produced by the following method.

2 g of Pt catalyst, 5 g of pure water, 5 g of 20 wt% Nafion (trade name: manufactured by DuPont) solution, and 20 g of 2-ethoxyethanol were sufficiently stirred and dispersed to prepare a cathode slurry. . The obtained slurry was applied to carbon paper (thickness 350 μm, manufactured by Toray Industries, Inc.) treated with water repellency with a control coater and dried to obtain a cathode. The loading density of the noble metal catalyst at the cathode was 2 mg / cm ² .

The anode and cathode were each cut into a 3.2 cm × 3.2 cm square so that the electrode area was 10 cm ² . The cut cathode and anode sandwiched Nafion 117 (trade name: manufactured by DuPont) as a proton conductive organic polymer membrane. A membrane electrode assembly was produced by thermocompression bonding for 10 minutes at 125 ° C. and 30 kg / cm ² .

A cathode holder and an anode holder were respectively arranged on the cathode side and the anode side of this membrane electrode assembly to produce a single cell of a fuel direct supply type solid polymer electrolyte fuel cell. A 1M aqueous methanol solution as a fuel is supplied to the anode at a flow rate of 0.6 mL / min, and air is supplied to the cathode at a flow rate of 200 mL / min, and the cell is maintained at 65 ° C. and 150 mA / cm ² current density. Was made to generate electricity. The cell voltage after 30 minutes was measured, and the results are summarized in Table 3 below.

  As shown in Table 3 above, No. 1 having an anode containing no basic polymer. With 26 MEAs, the cell voltage remains at 0.45V. No. having an anode containing no proton conductive inorganic oxide. In 27 MEAs, the cell voltage is as low as 0.25V. On the other hand, in addition to the supported catalyst and the proton conductive organic polymer binder, MEA (Nos. 1 to 25) including an anode further containing a complex of a proton conductive inorganic oxide and a basic polymer, In both cases, a high cell voltage is obtained.

No. In 1 to 17, all four weight ratios are defined within a preferable range. Specifically, the proton conductive inorganic oxide supported catalyst (C) and including SiO ₂ weight ratio of _{(SA + SiO 2) (W} SA + SiO2 / W C) is in the range of 0.05 to 0.5 There, the proton conductive inorganic oxide containing SiO ₂ (SA + SiO ₂₎ and the weight ratio of the proton conductive organic polymer binder _{(P) (W P / W} SA + SiO2) is in the range of 1-32. Further, the weight ratio (W _SiO2 / W _SA ) between the SiO ₂ particles and the proton conductive inorganic oxide ( _SA ) is in the range of 0.1 to 0.5, and the proton conductive inorganic oxide (SA) and The weight ratio (W _BP / W _SA ) of the basic polymer (BP) is in the range of 0.001 to 0.1.

  As described above, since the weight ratios are all defined within the preferred range, 1 to 17 MEAs are shown to obtain a very high cell voltage of 0.49 V or more.

  Even when one of the weight ratios is out of the preferred range, No. 1 in which the proton conductive inorganic oxide and the basic polymer are combined. 18-25 are No. The cell voltage is higher than that of No. 26, and the effect of complexing with the basic polymer is confirmed.

  As described above, according to the present invention, it is possible to provide an anode from which a fuel cell capable of obtaining a higher output than before can be obtained.

  Note that the present invention is not limited to the above-described embodiment itself, and can be embodied by modifying constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

DESCRIPTION OF SYMBOLS 1 ... Proton conductive membrane; 2 ... Anode; 3 ... Cathode; 4 ... Diffusion layer 5 ... Anode catalyst layer; 6 ... Diffusion layer; 7 ... Cathode catalyst layer 8 ... Oxidant supply groove; 9 ... Cathode holder; Supply groove 11 ... Anode holder; 12 ... Membrane electrode composite.

Claims (12)

A supported catalyst containing a conductive support material and catalyst fine particles supported on the conductive support material, and blended at a weight W _C ;
Complex of the silicon oxide-containing proton-conductive inorganic oxide of silicon oxide and the weight W total weight containing a proton-conductive inorganic oxides _SA W _{SA + SiO2} weight W _SiO2, a basic polymer having a weight W _BP , and the anode for a fuel cell characterized by comprising the electrode catalyst layer containing a proton conductive organic polymer binder which is at a weight W _P. 2. The fuel cell anode according to claim 1, wherein the weight ratio (W _{SA + SiO 2} / W _C ) is 0.05 or more and 0.5 or less. The anode for fuel cells according to claim 1 or 2, wherein the weight ratio (W _P / W _{SA + SiO 2} ) is 1 or more and 32 or less. _4. The fuel cell anode according to claim 1, wherein the weight ratio (W _SiO2 / W _SA ) is not less than 0.1 and not more than 0.5. 5. 5. The fuel cell anode according to claim 1, wherein the weight ratio (W _BP / W _SA ) is 0.001 or more and 0.1 or less.   The proton conductive inorganic oxide includes an oxide carrier and oxide particles supported on the surface of the oxide carrier, and the oxide carrier is at least selected from the group consisting of Ti, Zr, and Sn. 6. The method according to claim 1, wherein the oxide particle contains at least one second element selected from the group consisting of W, Mo, and V. 2. A fuel cell anode according to claim 1. Hammett acidity function H ₀ of the proton conductive inorganic oxide is:
-20.00 <H ₀ <-11.93
The anode for a fuel cell according to any one of claims 1 to 6, wherein:   The anode for fuel cells according to any one of claims 1 to 7, wherein the proton conductive organic polymer binder contains a sulfonic acid group.   The anode for a fuel cell according to any one of claims 1 to 8, wherein the basic polymer contains at least one selected from the group consisting of an amino group, a pyridyl group, and an imidazole group.   The anode for a fuel cell according to any one of claims 1 to 9, wherein the catalyst fine particles include at least one selected from Pt, Ru, and a PtRu alloy. A membrane electrode assembly comprising a fuel electrode, an oxidant electrode, and an electrolyte membrane disposed between the fuel electrode and the oxidant electrode,
The membrane electrode assembly, wherein the fuel electrode includes the anode for a fuel cell according to any one of claims 1 to 10.   A fuel cell comprising the membrane electrode assembly according to claim 11.

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