JP2006244782A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell which can improve durability without reducing power generation performance. <P>SOLUTION: A fuel cell 100 comprises an electrolyte film 11 and an MEA 15 having an anode electrode 12 and a cathode electrode 13 which are placed on the both sides of the electrolyte film 11, respectively. A material with hydrogen peroxide decomposition performance is placed in at least one region of regions composed of the electrolyte film 11, the anode electrode 12, and a mid-area between the electrolyte film 11 and the anode electrode 12. The material with hydrogen peroxide decomposition performance is a compound containing a single body of a metal element and/or the metal element. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell, and more particularly to a fuel cell capable of improving durability without reducing power generation performance.

  A fuel cell is based on an electrochemical reaction in a membrane electrode assembly (hereinafter referred to as “MEA (Membrane Electrode Assembly)”) including an electrolyte and electrodes (cathode and anode) disposed on both sides of the electrolyte. The generated electric energy is taken out through separators disposed on both sides of the MEA. Among these fuel cells, polymer electrolyte fuel cells (hereinafter referred to as “PEFC (Polymer Electrolyte Fuel Cell)”) used in home cogeneration systems and automobiles are operated at low temperatures. It is generally used at an operating temperature of 50 to 100 ° C. In addition, PEFC has shown high energy conversion efficiency of 50 to 60%, has a short start-up time, and has a small and light system.

  A unit cell of PEFC includes an electrolyte membrane, a cathode and an anode including a catalyst layer and a diffusion layer, and a separator, and the theoretical electromotive force thereof is 1.23V. However, since such a low electromotive force is insufficient as a power source for an electric vehicle or the like, the stack form is generally configured by disposing end plates or the like at both ends in the stacking direction of a stacked body in which unit cells are stacked in series. A fuel cell is used.

  On the other hand, it is clear that hydrogen peroxide is generated in the catalyst layer in the unit cell during power generation of the fuel cell, and the OH radicals generated from this hydrogen peroxide are the starting point and deteriorate the polymer electrolyte of MEA. It is becoming. Since such deterioration contributes to a decrease in the power generation performance of the fuel cell, it is desired to reduce the hydrogen peroxide in the MEA to suppress the deterioration and improve the durability and power generation performance of the fuel cell. Yes.

Several techniques for improving the power generation performance of fuel cells have been disclosed so far. For example, Patent Document 1 discloses a technique related to a cathode catalyst for a fuel cell, which is characterized in that CeO ₂ is supported on a carrier supporting Pt. By using such a catalyst, oxygen at the cathode is disclosed. The reduction reaction rate can be increased. Patent Document 2 discloses a technique relating to a fuel cell, in which the cathode-side electrode includes a catalyst / oxide / polymer electrolyte thin layer composed of an oxide, a catalyst, and a solid polymer electrolyte material. By using such a fuel cell, crossover is suppressed, and it is possible to prevent a decrease in power generation performance due to crossover.
JP 2003-100308 A JP 2003-86192 A

However, in the technique disclosed in Patent Document 1, CeO ₂ that does not contribute to the electrochemical reaction in the fuel cell is supported on the cathode catalyst. Here, it is known that the cathode reaction of the electrochemical reaction in the fuel cell is rate limiting. Therefore, when CeO ₂ that does not contribute to the electrochemical reaction in the fuel cell is supported on the cathode catalyst, there is a problem that the reaction rate of the electrochemical reaction at the cathode is lowered and the power generation performance of the fuel cell may be lowered. . Further, even with the technique disclosed in Patent Document 2, there is a problem that it is difficult to improve the durability of the fuel cell.

  Then, this invention makes it a subject to provide the fuel cell which can improve durability, without reducing electric power generation performance.

In order to solve the above problems, the present invention takes the following means. That is,
The invention according to claim 1 is a fuel cell comprising an electrolyte membrane and an MEA comprising an anode electrode and a cathode electrode provided on both sides of the electrolyte membrane, the electrolyte membrane, the anode electrode, and the electrolyte membrane; A substance having the ability to decompose hydrogen peroxide is provided in at least one of the areas between the anode electrode and the substance having the ability to decompose hydrogen peroxide. The above problem is solved by a fuel cell, which is a compound containing a metal element.

  Here, in the present invention, the substance having hydrogen peroxide decomposition performance is not particularly limited as long as it is a metal simple substance having hydrogen peroxide decomposition performance and / or a metal compound containing the metal element. Specific examples of the substance include Mn, Fe, Pt, Pd, Ni, Cr, Cu, Ce, Rb, Co, Ir, Ag, Au, Rh, Ti, Zr, Al, Hf, Ta, Nb, Os, etc. And / or a compound containing the above element.

  The invention according to claim 2 is the fuel cell according to claim 1, wherein the anode electrode includes a catalyst layer and a diffusion layer, and the anode electrode is provided with a substance having hydrogen peroxide decomposition performance. The substance having hydrogen peroxide decomposition performance is provided in at least one of a catalyst layer, a diffusion layer, and a region formed between the catalyst layer and the diffusion layer.

  The invention according to claim 3 is the fuel cell according to claim 1 or 2, wherein the substance having hydrogen peroxide decomposition performance is a metal element contained in an element group consisting of a transition metal element or a rare earth metal element. It is a compound containing a single element and / or the metal element.

  The invention according to claim 4 is the fuel cell according to any one of claims 1 to 3, wherein the substance having hydrogen peroxide decomposition performance is a cerium-containing oxide.

Here, in the present invention, specific examples of the cerium-containing oxide include CeO _{2 and the} like.

According to the first aspect of the present invention, the substance having the ability to decompose hydrogen peroxide is at least one of the electrolyte membrane, the anode electrode, and the region formed between the electrolyte membrane and the anode electrode (in the following). , The hydrogen peroxide in the MEA can be decomposed by the substance and / or ions eluted from the substance. The hydrogen peroxide present in the MEA contributes to the deterioration of the MEA, particularly the electrolyte membrane. Therefore, the degradation of the electrolyte membrane can be suppressed by decomposing the hydrogen peroxide in the MEA. . Further, according to the present invention, the power generation performance of the fuel cell is provided because the substance having hydrogen peroxide decomposition performance is provided in the above-mentioned region other than the cathode electrode which is the rate-limiting part of the electrochemical reaction in the fuel cell. There is little possibility of lowering. In addition, according to the present invention, the substance having hydrogen peroxide decomposition performance is provided on the anode side, and the outflow of the substance by the generated water is less than that on the cathode side. It can be maintained for a long time. Therefore, according to the first aspect of the present invention, it is possible to provide a fuel cell capable of improving the durability without reducing the power generation performance.
In the following, substances that themselves have hydrogen peroxide decomposition ability (metal simple substance / metal compound) and substances that elute ions that have hydrogen peroxide decomposition ability (metal simple substance / metal compound) are collectively referred to as “ It is expressed as “hydrogen peroxide decomposing substance”.

  According to the invention described in claim 2, when a substance having hydrogen peroxide decomposition performance is provided in the anode electrode, the anode catalyst layer, the anode diffusion layer, and the anode catalyst layer and the anode diffusion layer, Therefore, hydrogen peroxide generated in the catalyst layer of the anode electrode can be effectively decomposed. Therefore, according to the invention described in claim 2, it is possible to provide a fuel cell capable of effectively improving the durability without deteriorating the power generation performance.

  According to the third aspect of the present invention, the transition metal element alone or the compound containing the element, and / or the rare earth metal element alone or the compound containing the element, the electrolyte membrane, the anode electrode, and the electrolyte membrane and anode It is possible to provide at least one of the regions formed between the electrodes. Therefore, the hydrogen peroxide in the MEA can be decomposed by the hydrogen peroxide decomposing substance and / or ions eluted from the substance. Therefore, according to the invention described in claim 3, it is possible to provide a fuel cell capable of improving the durability without deteriorating the power generation performance.

According to the invention of claim 4, the cerium-containing oxide is provided in at least one of the electrolyte membrane, the anode electrode, and the region composed of the electrolyte membrane and the anode electrode. Here, Ce ³⁺ generated from the cerium-containing oxide can effectively decompose hydrogen peroxide, and the cerium-containing oxide is generally spread as a material for automobile catalysts. Therefore, according to the invention described in claim 4, it is possible to easily provide a fuel cell capable of improving durability without deteriorating power generation performance.

During power generation of a fuel cell, it is known that hydrogen peroxide is generated in the catalyst layer of the anode electrode, and OH radicals generated from the hydrogen peroxide degrade the electrolyte material of MEA (for example, an electrolyte membrane). . Up to now, a technology related to a fuel cell having a structure containing a compound (for example, CeO ₂ ) that elutes ions having hydrogen peroxide decomposition performance in the MEA has been disclosed. It remains only for the purpose of improving the reactivity in the cathode electrode, and a single metal having hydrogen peroxide decomposition performance and / or a compound containing the metal is added between the electrolyte membrane, the anode electrode, and the electrolyte membrane and the anode electrode. A technology relating to a fuel cell provided in at least one of the regions consisting of the above has not yet been disclosed. If the hydrogen peroxide decomposing substance is provided in the above region, the peroxide generated in the MEA without reducing the reaction rate of the electrochemical reaction in the fuel cell, that is, without reducing the power generation performance of the fuel cell. It becomes possible to decompose hydrogen, and it becomes easy to suppress deterioration of the electrolyte layer over a long period of time. Therefore, with such a configuration, it is possible to provide a fuel cell that can improve durability without deteriorating the power generation performance of the fuel cell.

The present invention has been made from such a viewpoint, and the gist of the present invention is that, for example, a hydrogen peroxide decomposing substance typified by CeO ₂ is present from the electrolyte membrane, the anode electrode, and between the electrolyte membrane and the anode electrode. An object of the present invention is to provide a fuel cell capable of improving durability without deteriorating power generation performance by adopting a configuration provided in at least one of the regions.

  Hereinafter, the fuel cell of the present invention will be described more specifically with reference to the drawings.

1. Configuration of Fuel Cell FIG. 1 is a sectional view schematically showing a fuel cell according to the first embodiment of the present invention. As illustrated, the fuel cell 100 according to the first embodiment of the present invention includes an electrolyte membrane 11, anode electrodes 12 (hereinafter simply referred to as “anode 12”) disposed on both sides of the electrolyte membrane 11, and the like. An MEA 15 including a cathode electrode 13 (hereinafter simply referred to as “cathode 13”) and separators 16a and 16b disposed outside the MEA 15 are provided. The anode 12 and the electrolyte membrane 11 include a cerium-containing oxide. (Hereinafter described as “CeO ₂ ”). The anode 12 includes an anode catalyst layer 12a and an anode diffusion layer 12b, while the cathode 13 includes a cathode catalyst layer 13a and a cathode diffusion layer 13b. The catalyst layers 12a and 13a are disposed on the electrolyte membrane 11 side, and the diffusion layers 12b and 13b. Are arranged on the separators 16a and 16b side, respectively. In the separators 16a and 16b arranged outside the MEA 15, reaction gas supply paths 18a, 18a,..., 18b, 18b,... Are formed on the diffusion layers 12b and 13b side, and the reaction gas supply on the anode 12 side is formed. A hydrogen-containing substance (hereinafter referred to as “hydrogen”) is supplied to the passages 18a, 18a,..., While an oxygen-containing substance (hereinafter, referred to as a reaction gas supply path 18b, 18b,. , “Air”, and cooling medium channels 17, 17,... Are formed on the opposite surfaces.

At the time of power generation of the fuel cell, part of oxygen contained in the air supplied from the reaction gas supply paths 18b, 18b,... May pass through the electrolyte membrane 11 and reach the anode catalyst layer 12a. When this oxygen is reduced in the catalyst layer 12a (in the case where the catalyst layer 12a includes a catalyst made of platinum-supported carbon, for example, on platinum and / or carbon), hydrogen peroxide is generated. OH radicals resulting from the hydrogen peroxide are generated. The OH radical contributes to the deterioration of the electrolyte membrane 11, and the electrolyte membrane 11 is damaged as the deterioration proceeds. If the electrolyte membrane 11 is damaged, the voltage of the fuel cell is lowered, leading to a decrease in power generation performance. Therefore, the degradation of the electrolyte membrane is suppressed by previously decomposing hydrogen peroxide that contributes to the damage, and the fuel cell It is desirable to improve the durability. Therefore, in the fuel cell 100 according to the present embodiment, the catalyst layer is mixed with CeO ₂ that elutes Ce ³⁺ having hydrogen peroxide decomposition performance into the electrolyte membrane 11, the anode catalyst layer 12a, and the anode diffusion layer 12b. The hydrogen peroxide generated in 12a is decomposed to suppress the deterioration of the electrolyte membrane 11.

The fuel cell 100 according to the present invention is characterized in that CeO ₂ is provided in the anode 12, the electrolyte membrane 11, and the region formed between the anode 12 and the electrolyte membrane 11. Hereinafter, effects obtained by arranging CeO ₂ in such a region will be described.

  In the anode catalyst layer, an electrochemical reaction in which electrons and hydrogen ions are generated from hydrogen supplied via the reaction gas supply path and the anode diffusion layer occurs. On the other hand, in the cathode catalyst layer, an electrochemical reaction occurs in which water is generated from electrons, oxygen contained in the air supplied through the reaction gas supply path and the cathode diffusion layer, and hydrogen ions that have passed through the electrolyte membrane. . Usually, it is known that there is a difference in the reaction rate of the electrochemical reaction between the anode and the cathode, and in the fuel cell, the cathode reaction is the rate-limiting of the electrochemical reaction. Here, when the hydrogen peroxide decomposing substance is mixed into the MEA, the cathode can also be a candidate for the mixing site. However, if a hydrogen peroxide decomposing substance is mixed into the cathode, which is the rate limiting part of the electrochemical reaction in the fuel cell, if the hydrogen peroxide decomposing substance does not contribute to the electrochemical reaction at the cathode, the electrochemical reaction of the cathode There is a problem that the reaction rate of the reaction is further reduced. On the other hand, when the hydrogen peroxide decomposing substance also contributes to the electrochemical reaction of the cathode, it is considered that the substance (for example, Pt or the like) is less likely to decrease the rate of the cathode reaction. Is often expensive, and thus tends to increase the manufacturing cost of the fuel cell. In addition, the flow rate of air supplied to the cathode is usually larger than the flow rate of hydrogen supplied to the anode, and water is generated by an electrochemical reaction at the cathode. That is, since more material is moving at the cathode than at the anode, when the hydrogen peroxide decomposing substance is mixed into the cathode, the hydrogen peroxide decomposing substance is easily carried away by the substance moving inside the cathode. There is also a problem that it is difficult to maintain the decomposition performance over a long period of time.

Therefore, in order to avoid these problems, in the present invention, a hydrogen peroxide decomposing substance such as CeO ₂ is introduced from the electrolyte membrane, the anode electrode (anode catalyst layer, anode diffusion layer), and between the electrolyte membrane and the anode electrode. It is set as the structure provided in at least any one area | region of becoming. With this configuration, hydrogen peroxide in the MEA can be decomposed by the hydrogen peroxide decomposing substance. Furthermore, this configuration also makes it possible to decompose the hydrogen peroxide in the anode catalyst layer, thereby preventing deterioration of the electrolyte material in the electrolyte membrane and the cathode catalyst layer due to hydrogen peroxide in the anode reverse diffusion water. It is also possible to do. Therefore, according to the present invention, it is possible to provide a fuel cell that can improve the durability without reducing the power generation performance at a relatively low cost.

In the fuel cell of the present invention, a hydrogen peroxide decomposing substance such as CeO ₂ is provided in at least one of the electrolyte membrane, the anode (anode catalyst layer, anode diffusion layer), and the region between the electrolyte membrane and the anode. If it is, the arrangement form of the hydrogen peroxide decomposing substance is not particularly limited. As in the fuel cell 100 shown in FIG. 1, the electrolyte membrane 11, the anode catalyst layer 12a, and the anode diffusion layer 13a may be provided with CeO ₂ , for example, the electrolyte membrane 11, the anode catalyst layer 12a, or the anode diffusion. CeO ₂ may be provided in only one part of the layer 13a. Therefore, hereinafter, a fuel cell in a form in which CeO ₂ is provided only in one portion of the electrolyte membrane 11, the anode catalyst layer 12a, or the anode diffusion layer 13a will be described.

FIG. 2A is a cross-sectional view schematically showing the fuel cell of the present invention according to the second embodiment. As illustrated, the fuel cell 200 of the present invention according to the second embodiment includes an electrolyte membrane 11 and an MEA 25 including an anode 22 and a cathode 13 disposed on both sides of the electrolyte membrane 11, and an outside of the MEA 25. Separators 16 a and 16 b are provided, and CeO ₂ is mixed in the electrolyte membrane 11. The anode 22 includes an anode catalyst layer 22a and an anode diffusion layer 22b, while the cathode 13 includes a cathode catalyst layer 13a and a cathode diffusion layer 13b. The catalyst layers 22a and 13a are disposed on the electrolyte membrane 11 side, and the diffusion layers 22b and 13b. Are arranged on the separators 16a and 16b side, respectively. In FIG. 2A, parts having the same configuration as the constituent parts of the fuel cell 100 according to the first embodiment are assigned the same reference numerals as those shown in FIG. Is omitted.

As shown in FIG. 2 (A), if CeO ₂ is mixed in the electrolyte membrane 11, hydrogen peroxide, which is a source of OH radicals that degrade the electrolyte membrane 11, is absorbed in the electrolyte membrane 11 that is a degradation site. Since it becomes possible to decompose, it becomes possible to directly prevent the deterioration of the electrolyte membrane 11. Therefore, with this configuration, it is possible to provide the fuel cell 200 that can improve the durability without reducing the power generation performance.

FIGS. 2B and 2C are cross-sectional views schematically showing a more detailed example of the fuel cell of the present invention according to the second embodiment. As shown in FIG. 2B, in the fuel cell 210 according to this embodiment, CeO ₂ is mixed in the portion 11a of the electrolyte membrane 11 on the anode catalyst layer side. On the other hand, as shown in FIG. 2C, in the fuel cell 220 according to this embodiment, CeO ₂ is mixed in the portion 11c of the electrolyte membrane 11 on the cathode catalyst layer side. 2B and 2C, parts having the same configuration as the constituent parts of the fuel cell 200 are given the same reference numerals as the constituent parts in FIG. Detailed description is omitted.

As shown in FIG. 2B, if CeO ₂ is mixed in the portion 11a on the anode catalyst layer side of the electrolyte membrane 11, the hydrogen peroxide generated in the catalyst layer 22a and reaching the electrolyte membrane 11 is It becomes possible to decompose at the part 11a. Therefore, by adopting such a configuration, it is possible to effectively suppress the deterioration of the electrolyte membrane 11, so that it is possible to provide the fuel cell 210 that can improve the durability without reducing the power generation performance. Become.

On the other hand, as shown in FIG. 2C, even if CeO ₂ is mixed in the portion 11c on the cathode catalyst layer side of the electrolyte membrane 11, hydrogen peroxide in the electrolyte membrane 11 can be decomposed. Therefore, even with such a configuration, it is possible to suppress the deterioration of the electrolyte membrane 11, and thus it is possible to provide the fuel cell 220 that can improve the durability without reducing the power generation performance.

FIG. 3A is a cross-sectional view schematically showing a fuel cell of the present invention according to the third embodiment. As illustrated, the fuel cell 300 according to the third embodiment of the present invention includes an MEA 35 including an electrolyte membrane 31 and anodes 32 and cathodes 13 disposed on both sides of the electrolyte membrane 31, and outside the MEA 35. Separators 16a and 16b are provided. The anode 32 includes an anode catalyst layer 12a and an anode diffusion layer 22b, while the cathode 13 includes a cathode catalyst layer 13a and a cathode diffusion layer 13b. The catalyst layers 12a and 13a are disposed on the electrolyte membrane 31 side, and the diffusion layers 22b and 13b. Are arranged on the separators 16a and 16b side, respectively. CeO ₂ is mixed in the anode catalyst layer 12a. In FIG. 3 (A), parts that adopt the same configuration as the constituent parts of the fuel cell 100 according to the first embodiment and / or the fuel cell 200 according to the second embodiment are shown in FIG. 1 and / or FIG. The same reference numerals are assigned to the components shown in (A), and detailed description thereof is omitted.

As shown in FIG. 3A, when CeO ₂ is mixed in the anode catalyst layer 12a, hydrogen peroxide that is a source of OH radicals that degrade the electrolyte membrane 31 is converted at the hydrogen peroxide generation site. Since the catalyst layer 12a can be decomposed, the electrolyte membrane 31 can be effectively prevented from being deteriorated. Therefore, with this configuration, it is possible to provide the fuel cell 300 that can improve durability without deteriorating the power generation performance.

3 (B) and 3 (C) are cross-sectional views schematically showing a further detailed example of the fuel cell according to the third embodiment of the present invention. As shown in FIG. 3B, in the fuel cell 310 according to this embodiment, CeO ₂ is mixed in the portion 12d on the anode diffusion layer side of the anode catalyst layer 12a. On the other hand, as shown in FIG. 3C, in the fuel cell 320 according to this embodiment, CeO ₂ is mixed in the portion 12e on the electrolyte membrane side of the anode catalyst layer 12a. 3 (B) and 3 (C), parts having the same configuration as the constituent parts of the fuel cell 300 are given the same reference numerals as the constituent parts in FIG. Detailed description is omitted.

As shown in FIG. 3B, if CeO ₂ is mixed in the diffusion layer side portion 12d of the anode catalyst layer 12a, the hydrogen peroxide generated in the catalyst layer 12a is contained in the catalyst layer 12a. Can be disassembled. Therefore, with this configuration, it is possible to suppress deterioration of the electrolyte membrane 31, and thus it is possible to provide the fuel cell 310 that can improve the durability without reducing the power generation performance.

On the other hand, as shown in FIG. 3C, if CeO ₂ is mixed in the portion 12e on the electrolyte membrane side of the anode catalyst layer 12a, hydrogen peroxide generated in the catalyst layer 12a is transferred to the electrolyte membrane 31. Before reaching, hydrogen peroxide can be decomposed in the catalyst layer 12a. Therefore, by adopting such a configuration, it is possible to more effectively suppress the deterioration of the electrolyte membrane 31, and thus it is possible to provide the fuel cell 320 that can improve the durability without reducing the power generation performance. become.

FIG. 4A is a sectional view schematically showing a fuel cell according to the fourth embodiment of the present invention. As shown in the drawing, the fuel cell 400 of the present invention according to the fourth embodiment includes an MEA 45 including an electrolyte membrane 31 and anodes 42 and cathodes 13 disposed on both sides of the electrolyte membrane 31, and outside the MEA 45. Separators 16a and 16b are provided. The anode 42 includes an anode catalyst layer 22a and an anode diffusion layer 12b, while the cathode 13 includes a cathode catalyst layer 13a and a cathode diffusion layer 13b. The catalyst layers 22a and 13a are disposed on the electrolyte membrane 11 side, and the diffusion layers 12b and 13b. Are arranged on the separators 16a and 16b side, respectively. CeO ₂ is mixed in the anode diffusion layer 12b. In FIG. 4 (A), the parts adopting the same configuration as the constituent parts of the fuel cell 100 according to the first embodiment and / or the fuel cell 200 according to the second embodiment are shown in FIG. 1 and / or FIG. The same reference numerals are assigned to the components shown in (A), and detailed description thereof is omitted.

As shown in FIG. 4A, if CeO ₂ is mixed in the anode diffusion layer 12b, the anode diffusion layer 12b is not a reaction field of the anode, so there is little possibility of reducing the reaction rate of the anode reaction. Even if CeO ₂ is mixed in the anode diffusion layer 12b, Ce ³⁺ eluted from the CeO ₂ can reach the anode catalyst layer 22a together with hydrogen supplied in the diffusion layer 12b. That is, even in such a fuel cell 400, hydrogen peroxide can be decomposed by the anode catalyst layer 22a and / or the electrolyte membrane 31, so that deterioration of the electrolyte membrane 31 can be prevented. Become. Therefore, with this configuration, it is possible to provide the fuel cell 400 that can improve the durability without deteriorating the power generation performance.

4 (B) and 4 (C) are cross-sectional views schematically showing a more detailed example of the fuel cell according to the fourth embodiment of the present invention. As shown in FIG. 4B, in the fuel cell 410 according to this embodiment, CeO ₂ is mixed in the separator-side portion 12s of the anode diffusion layer 12b. On the other hand, as shown in FIG. 4C, in the fuel cell 420 according to this embodiment, CeO ₂ is mixed in the portion 12c on the anode catalyst layer side of the anode diffusion layer 12b. 4B and 4C, parts having the same configuration as the constituent parts of the fuel cell 400 are given the same reference numerals as the constituent parts in FIG. Detailed description is omitted.

As described above, even when CeO ₂ is mixed in the anode diffusion layer 12b, the deterioration of the electrolyte membrane 31 can be suppressed. Therefore, by adopting such a configuration, durability is not reduced without reducing the power generation performance. It becomes possible to provide the fuel cell 410 or 420 that can improve the fuel efficiency.

2. CeO ₂ Dispersion Method A method of mixing and dispersing CeO ₂ in the electrolyte membrane, the anode catalyst layer, and the anode diffusion layer will be described below.

The electrolyte membrane provided in the fuel cell of the present invention is formed from, for example, a molten electrolyte. On the other hand, CeO ₂ provided in the fuel cells 100, 200, 210, 220, 300, 310, 320, 400, 410, and 420 of the present invention is a powdery substance. Therefore, it is possible to obtain an electrolyte membrane in which CeO ₂ is dispersed by a method such as dispersing powdered CeO ₂ in a molten electrolyte (hereinafter sometimes referred to as “electrolyte ink”). become. In addition, the electrolyte membrane concerning this invention can also be divided and manufactured in a layer. Therefore, for example, when manufacturing an electrolyte membrane in which CeO ₂ is unevenly distributed at a site on the anode catalyst layer side, CeO ₂ is dispersed in the site (first layer) of the electrolyte membrane disposed on the anode catalyst layer side. Then, after the first layer is manufactured, the electrolyte in which CeO ₂ is unevenly distributed is manufactured by a method such as manufacturing a layer (second layer) of the electrolyte membrane in which CeO ₂ is not dispersed on the surface of the first layer. A film can be formed.

The anode catalyst layer provided in the fuel cell of the present invention is coated with a paste-like catalyst layer (hereinafter sometimes referred to as “catalyst ink”) on the surface of the electrolyte membrane produced by the above method or the like, and then dried. Manufactured by a method such as Here, the catalyst ink is prepared by a method of dispersing powdery platinum-supported carbon or the like that functions as a catalyst in an electrochemical reaction in a fuel cell in a solvent. Therefore, an anode catalyst layer in which CeO ₂ is dispersed can be obtained by a method such as dispersing powdered CeO ₂ in the catalyst ink. In the case of producing a catalyst layer CeO ₂ is unevenly distributed, providing a catalyst ink that has not been dispersed catalyst ink and CeO ₂ containing dispersed CeO _2, the electrolyte membrane surface one catalyst layer After applying and drying, a catalyst layer in which CeO ₂ is unevenly distributed can be obtained by applying the other catalyst layer to the surface of the dried catalyst layer and drying it.

The anode diffusion layer provided in the fuel cell of the present invention is coated with a water-repellent paste (hereinafter sometimes referred to as “water-repellent paste”) on a substrate made of, for example, carbon paper, and then dried. Manufactured by a method such as Here, the water-repellent paste contains, for example, carbon and polytetrafluoroethylene resin (PTFE). Therefore, an anode diffusion layer in which CeO ₂ is dispersed can be obtained by a method such as dispersing powdered CeO ₂ in a water-repellent paste. The diffusion layer CeO ₂ is unevenly distributed, by the production method and the following same method or the like of the catalyst layer CeO ₂ are unevenly distributed, can be produced.

A specific example when CeO ₂ is dispersed in each part of the fuel cell according to the above embodiment will be described below.

2.1. Like the fuel cell 100 and 300 according to the embodiment when evenly distributed in the anode catalyst layer, in the case of evenly distributing the CeO ₂ to the anode catalyst layer, in the catalyst ink adjustment, the CeO ₂ to the catalyst ink Mix and disperse. Here, the mixing / dispersing amount of CeO ₂ is preferably 1% by mass or more with respect to the catalyst basis weight from the viewpoint of sustaining the hydrogen peroxide decomposition effect over a long period of time. On the other hand, from the viewpoint of suppressing a decrease in power generation performance due to excessive dispersion, the amount of mixing / dispersing is preferably 5% by mass or less.
In the present invention, the particle size of CeO ₂ mixed and dispersed in the anode catalyst layer is not particularly limited as long as hydrogen peroxide decomposition performance can be effectively expressed, but the elution to the outside of the fuel cell is suppressed. From the viewpoint of making the hydrogen peroxide decomposition effect sustainable over a long period of time, it is preferably 0.1 μm or more. On the other hand, from the viewpoint of suppressing damage to the electrolyte membrane caused by containing too large CeO ₂ , the particle diameter is preferably 5 μm or less.
After the amount of CeO ₂ is dispersed, for example, a catalyst ink containing CeO ₂ is applied to the electrolyte membrane or the anode diffusion layer and dried to form the anode catalyst layer. Here, the coating method is not particularly limited, and specific examples of the coating method include a transfer method, a spray method, and an electrostatic coating method.

2.2. When the dispersion is concentrated on the anode catalyst layer When the CeO ₂ is concentrated on the anode diffusion layer side or the electrolyte membrane side of the anode catalyst layer as in the fuel cells 310 and 320 according to the above-described embodiment, first, A catalyst ink not containing CeO ₂ is formed by the coating method or the like. After that, adjusting the CeO ₂ containing catalyst solution of CeO ₂ for example 1 to 5% by weight relative to the catalyst unit weight of the catalyst ink were mixed and dispersed, the anode catalyst layer the CeO ₂ containing catalyst ink by the coating method or the like It is possible to produce an anode catalyst layer comprising intensively dispersed CeO ₂ by applying to the anode diffusion layer side or the electrolyte membrane side and drying.

2.3. In the case where the electrolyte membrane is evenly dispersed As in the fuel cells 100 and 200 according to the above-described embodiment, when the CeO ₂ is uniformly dispersed in the electrolyte membrane, the CeO ₂ is mixed and dispersed in the electrolyte ink at the time of producing the electrolyte membrane. Let Here, the mixing / dispersing amount of CeO ₂ is preferably 1% by mass or more with respect to the electrolyte component in the electrolyte ink, from the viewpoint of allowing the hydrogen peroxide decomposition effect to be sustained over a long period of time. On the other hand, from the viewpoint of suppressing a decrease in ionic conductivity due to excessive dispersion, the amount of mixing / dispersing is preferably 5% by mass or less.
In the present invention, the particle size of CeO ₂ mixed / dispersed in the electrolyte membrane is not particularly limited as long as the hydrogen peroxide decomposition performance can be effectively expressed. For example, when the thickness of the electrolyte membrane is about 30 to 50 μm, the particle size is preferably 10 μm or less from the viewpoint of suppressing damage to the catalyst layer caused by containing too large CeO _2. . On the other hand, when CeO ₂ is dispersed in the electrolyte membrane, CeO ₂ is retained by the electrolyte component in the electrolyte membrane, so it is considered that the particle size may be 0.1 μm or less.
In the present invention, the method for forming the electrolyte membrane from the electrolyte ink in which the above amount of CeO ₂ is dispersed is not particularly limited, and specific examples of the forming method include a casting method and a melt extrusion method. be able to.

2.4. When Concentrating Dispersion on Electrolyte Membrane When CeO ₂ is intensively dispersed on the anode catalyst layer side or the cathode catalyst layer side of the electrolyte membrane as in the fuel cells 210 and 220 according to the above-described embodiment, first, cast An electrolyte membrane not including CeO ₂ is formed by a method or the like. After that, adjusting the CeO ₂ containing electrolyte ink was mixed and dispersed with respect to electrolyte component for example of 1 to 5 wt% of CeO ₂ in the electrolyte ink, the CeO ₂ containing electrolyte ink by the forming method and the like, the CeO ₂ By forming the electrolyte membrane on the electrolyte membrane that is not provided, it is possible to produce an electrolyte membrane that includes CeO ₂ dispersed in a concentrated manner.

2.5. Like the fuel cell 100 and 400 according to the embodiment when to evenly distribute the anode diffusion layer, in the case of evenly distributing the CeO ₂ to the anode diffusion layer, when the water repellent paste preparation, CeO ₂ to water repellent paste Mix and disperse. Here, the mixing / dispersing amount of CeO ₂ is 1 with respect to the solid content ratio (or the basis weight of the water-repellent layer) in the water-repellent paste from the viewpoint that the hydrogen peroxide decomposition effect can be sustained over a long period of time. It is preferable to set it as mass% or more. On the other hand, from the viewpoint of suppressing a decrease in power generation performance due to excessive dispersion, the mixing / dispersing amount is preferably 5% by mass or less.
In the present invention, the particle size of CeO ₂ to be mixed and dispersed in the anode diffusion layer is not particularly limited as long as hydrogen peroxide decomposition performance can be expressed effectively, but the elution to the outside of the fuel cell is suppressed. From the viewpoint of making the hydrogen peroxide decomposition effect sustainable over a long period of time, it is preferably 0.1 μm or more. On the other hand, from the viewpoint of suppressing damage to the anode catalyst layer caused by containing too large CeO ₂ , the particle size is preferably 5 μm or less.
After the above amount of CeO ₂ is dispersed, for example, by impregnating the diffusion layer base material with a water repellent paste containing CeO ₂ , an anode diffusion layer in which CeO ₂ is uniformly dispersed can be produced. .

2.6. When Dispersion is Concentrated in the Anode Diffusion Layer When CeO ₂ is intensively dispersed on the separator side or anode catalyst layer side of the anode diffusion layer as in the fuel cells 410 and 420 according to the above-described embodiment, first, CeO 2 is dispersed. An anode diffusion layer subjected to a water repellent treatment is produced by a method of impregnating the diffusion layer base material with a water repellent paste not having ₂ . Thereafter, a CeO ₂ -containing water-repellent paste in which, for example, 1 to 5% by mass of CeO ₂ is mixed and dispersed with respect to the solid content ratio in the water-repellent paste (or the basis weight of the water-repellent layer) is prepared, and the above-described application method and the like By applying the CeO ₂ -containing water-repellent paste to the separator side or the anode catalyst layer side of the anode diffusion layer and drying it, it becomes possible to produce an anode diffusion layer comprising intensively dispersed CeO ₂ .

In the above description, for convenience, the fuel cell in the form in which no member is interposed between the anode and the electrolyte membrane and between the anode catalyst layer and the anode diffusion layer has been described. However, the fuel cell according to the present invention is in this form. However, the present invention is not limited thereto, and may be a form in which inclusions (for example, a substance for improving power generation performance) are provided in these portions. When the fuel cell according to the present invention has such a configuration, a hydrogen peroxide decomposing substance such as CeO ₂ can be dispersed in the inclusion.

  When inclusions are provided between the anode and the electrolyte membrane, if hydrogen peroxide decomposition substances are dispersed in the inclusions, hydrogen peroxide generated in the catalyst layer of the anode and moving to the electrolyte membrane This hydrogen peroxide can be decomposed when passing through the inclusion. Further, if the hydrogen peroxide decomposing substance is dispersed in the inclusions provided between the anode and the electrolyte membrane, there is little possibility that the electrochemical reaction of the cathode is inhibited by the hydrogen peroxide decomposing substance. Therefore, by adopting such a configuration, it is possible to provide a fuel cell that can improve durability without deteriorating power generation performance.

  On the other hand, when an inclusion is provided between the anode catalyst layer and the anode diffusion layer, if hydrogen peroxide decomposition material is dispersed in the inclusion, hydrogen peroxide eluted from the hydrogen peroxide decomposition material Hydrogen peroxide can be decomposed by ions having decomposition performance. In addition, when the hydrogen peroxide decomposition substance is dispersed in the inclusions provided between the anode catalyst layer and the anode diffusion layer, there is little possibility that the electrochemical reaction of the cathode is inhibited by the hydrogen peroxide decomposition substance. . Therefore, even with such a configuration, it is possible to provide a fuel cell that can improve durability without reducing power generation performance.

For convenience, the fuel cell in which CeO ₂ is dispersed has been described in the above description. However, the hydrogen peroxide decomposing substance that the fuel cell according to the present invention can be provided is not limited to CeO ₂ , It is suitable if it is a substance (metal simple substance / metal compound) having hydrogen peroxide decomposition ability in the environment and / or a substance (metal simple substance / metal compound) that generates ions having hydrogen peroxide decomposition ability in the environment within the MEA. be able to. Specific examples of substances that have hydrogen peroxide decomposition performance in the environment within the MEA or substances that generate hydrogen peroxide decomposition performance in the environment within the MEA include Mn, Fe, Pt, Pd, Ni, Cr, Mentioning simple substance consisting of Cu, Ce, Se, Rb, Co, Ir, Ag, Au, Rh, Sn, Ti, Zr, Al, Hf, Ta, Nb, Os, Si, C, etc. and a compound containing the above elements Can do.

  Further, in the above description, the fuel cell including the separator in the form in which the reaction gas supply path is formed on the diffusion layer side has been described. However, the separator that can be included in the fuel cell according to the present invention is not limited to the form. For example, it may be a flat type separator in which no reaction gas supply path is formed on the diffusion layer side.

  The constituent materials of the constituent elements (electrolyte membrane, anode catalyst layer, anode diffusion layer, cathode catalyst layer, cathode diffusion layer, separator, etc.) provided in the fuel cell according to the present invention are not particularly limited, In a normal PEFC, materials that can constitute these components can be appropriately used.

Using a fuel cell (Example) including an electrolyte membrane, an anode catalyst layer, and an anode diffusion layer in which CeO ₂ is uniformly dispersed by the above mixing / dispersing method, and a fuel cell (Comparative Example) not including CeO ₂ Durability tests were conducted, and the amount of F ions (F elution amount) contained in the water collected from these fuel cells was measured. The fuel cells according to the present example and the comparative example were each provided with an electrolyte membrane containing a fluorine-based resin. Further, since F ions are eluted when the electrolyte membrane containing a fluororesin is deteriorated, the F elution amount is an index of durability.

  In the durability test, the fuel cell according to the example and the fuel cell according to the comparative example had substantially the same power generation performance during normal operation. Further, in the measurement of F elution amount, in the fuel cell according to the comparative example, many F ions were eluted as time passed, but in the fuel cell according to the example, the elution amount of F ions was reduced. Therefore, according to the present invention, it has been confirmed that it is possible to provide a fuel cell capable of improving durability without deteriorating power generation performance.

1 is a cross-sectional view schematically showing a fuel cell of the present invention according to a first embodiment. It is sectional drawing which shows schematically the fuel cell of this invention concerning 2nd Embodiment. It is sectional drawing which shows schematically the fuel cell of this invention concerning 3rd Embodiment. It is sectional drawing which shows schematically the fuel cell of this invention concerning 4th Embodiment.

Explanation of symbols

11, 31 Electrolyte membrane 12, 22, 32, 42 Anode (anode electrode)
12a, 22a Anode catalyst layer 12b, 22b Anode diffusion layer 13 Cathode (cathode electrode)
15, 25, 35, 45 MEA
16a, 16b Separator 100, 200, 300, 400 Fuel cell

Claims (4)

A fuel cell comprising an electrolyte membrane and an MEA comprising an anode electrode and a cathode electrode provided on both sides of the electrolyte membrane,
A substance having hydrogen peroxide decomposition performance is provided in at least one of the electrolyte membrane, the anode electrode, and a region between the electrolyte membrane and the anode electrode,
A fuel cell, wherein the substance having hydrogen peroxide decomposition performance is a simple substance of a metal element and / or a compound containing the metal element. The anode electrode includes a catalyst layer and a diffusion layer;
When the anode electrode is provided with the substance having the ability to decompose hydrogen peroxide, the substance having the ability to decompose hydrogen peroxide includes the catalyst layer, the diffusion layer, and the catalyst layer and the diffusion layer. 2. The fuel cell according to claim 1, wherein the fuel cell is provided in at least one of the regions. The said substance which has hydrogen peroxide decomposition | disassembly performance is the simple substance of the metal element contained in the element group which consists of a transition metal element or a rare earth metal element, and / or the compound containing this metal element, It is characterized by the above-mentioned. Or the fuel cell of 2. The fuel cell according to any one of claims 1 to 3, wherein the substance having hydrogen peroxide decomposition performance is a cerium-containing oxide.

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