JP2007035325A - Fuel cell and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell which can improve power generation performance by supplying oxygen to a catalyst effectively, and a method for manufacturing the fuel cell. <P>SOLUTION: A fuel cell 100 comprises an electrolyte film 11, and an anode 12 and a cathode 13 arranged on both sides of the electrolyte film 11, respectively. The anode 12 and the cathode 13 have at least catalyst layers 12a, 13a respectively, the catalyst layer 13a of the cathode has an oxygen absorbent 4, a catalyst 5, and a proton conductor 6. The oxygen absorbent 4 is formed by fixing a metalloporphyrin 3 to the surface of carbon 1 through an imidazole group 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell and a method for manufacturing the fuel cell, and more particularly to a fuel cell capable of improving power generation performance by effectively supplying oxygen to a catalyst and a method for manufacturing the fuel cell.

  A fuel cell represented by a polymer electrolyte fuel cell (hereinafter referred to as “PEFC (Polymer Electrolyte Fuel Cell”)) includes an electrolyte membrane and electrodes (cathode and cathode) disposed on both sides of the electrolyte membrane. The electrical energy generated by the electrochemical reaction in the membrane electrode assembly (hereinafter referred to as “MEA (Membrane Electrode Assembly)”) including the anode is externally supplied via separators disposed on both sides of the MEA. It has been taken out. Among fuel cells, PEFCs used for household cogeneration systems and automobiles can be operated in a low temperature region and are generally used at an operating temperature of about 80 to 100 ° C. In addition, PEFC has shown high energy conversion efficiency of 30 to 40%, has a short start-up time, and has a small and lightweight system. Therefore, PEFC has attracted attention as an optimal power source for electric vehicles and portable power sources.

  A unit cell of PEFC includes an electrolyte membrane, a cathode and an anode including at least a catalyst layer, and a separator, and a 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.

An electrochemical reaction that is a source of electricity generation in a fuel cell proceeds in the following steps. First, hydrogen supplied to the anode is decomposed into hydrogen ions and electrons on a catalyst (for example, platinum supported on carbon, etc., the same applies hereinafter).
Anode side: H ₂ → 2H ⁺ + 2e ⁻
Then, hydrogen ions generated in the anode (hereinafter referred to as “protons”) pass through the electrolyte membrane, which is a proton conductor, and reach the cathode. Here, since the electrolyte membrane has a property of allowing only ions to pass therethrough, the electrons generated at the anode cannot pass through the electrolyte membrane and move to the cathode bypassing the electrolyte membrane. In a fuel cell, electricity is generated by such movement of electrons. On the other hand, the oxygen supplied to the cathode reacts with the protons and electrons on the catalyst provided in the cathode to become water.
Cathode side: 2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O
Thus, oxygen, protons, and electrons are reacted in the cathode of the fuel cell during power generation, and such oxygen is usually supplied to the cathode in the form of air.

  In the conventional fuel cell, the amount of oxygen supplied to the cathode, particularly the catalyst contained in the cathode catalyst layer, is insufficient, or the performance of the catalyst contained in the cathode is insufficient. The efficiency of the chemical reaction (hereinafter referred to as “cathode reaction efficiency”) is insufficient, and sufficient power generation performance is not obtained. Therefore, it is desired to provide a fuel cell capable of improving the power generation performance by improving the reaction efficiency of the cathode.

So far, several techniques aimed at improving the performance of PEFC cathode catalysts have been disclosed. For example, Patent Document 1 discloses a technology related to a catalyst for a PEFC cathode in which a transition metal macrocycle complex and a noble metal are supported on a carbon material having a BET specific surface area of 500 m ² / g or more. It is said that a high-performance PEFC cathode catalyst can be obtained by adopting the form. Patent Document 2 discloses a fuel cell in which a substance obtained by adding metal porphyrin to imidazole is mixed at the cathode.
JP 2003-109614 A JP 2004-319292 A

  Here, if the fuel cell is equipped with a high-performance PEFC cathode catalyst, it is considered that the reaction efficiency of the cathode can be improved, and the power generation performance can be effectively improved. However, even if the performance of the PEFC cathode catalyst is improved by the technique disclosed in Patent Document 1, if the amount of oxygen that can improve the reaction efficiency of the cathode is not supplied to the catalyst, the reaction of the cathode It is difficult to improve the efficiency, and it is difficult to improve the power generation performance of the fuel cell. That is, even if a fuel cell including the catalyst disclosed in Patent Document 1 is manufactured, there is a problem that it is difficult to obtain a sufficient power generation performance improvement effect. Patent Document 1 also discloses a technique for fixing a macrocyclic compound complex of a transition metal to a carbon material by heat treatment at a temperature of 700 to 1100 ° C. However, at such a temperature, a part of the macrocyclic compound complex is thermally decomposed, so that it is difficult to obtain a sufficient power generation performance improvement effect.

  Then, this invention makes it a subject to provide the fuel cell which can improve electric power generation performance by supplying oxygen to a catalyst effectively, and the manufacturing method of the said fuel cell.

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 anode and a cathode disposed on both sides of the electrolyte membrane, wherein the anode and the cathode comprise at least a catalyst layer, and the catalyst layer of the cathode Further, the fuel cell is provided with an oxygen adsorbent formed by immobilizing a metal porphyrin on the carbon surface via an imidazole group, a catalyst, and a proton conductor. To do.

  Here, the catalyst layer of the cathode according to the present invention is only required that the metal porphyrin is fixed on the carbon surface via an imidazole group, and as a specific example of the imidazole group interposed between the metal porphyrin and carbon, Alkyl imidazole and the like can be mentioned. More specifically, N-benzylimidazole, N-methylimidazole, 2-methylimidazole, N-laurylimidazole, poly (N-vinylimidazole), poly (N-vinylimidazole- (Co-octyl methacrylate), N-trityl imidazole, 3- (imidazol-1-yl) propylamine and the like. The structure of 3- (imidazol-1-yl) propylamine is represented by the following formula (1).

また、本発明において、金属ポルフィリンとは、５，１０，１５，２０−テトラアリールポルフィリン等の中心に、コバルト原子、銅原子、鉄原子、マンガン原子等の金属原子が配位したものを指し、５，１０，１５，２０−テトラアリールポルフィリンにかかるアリール基の具体例としては、フェニル基、ｏ−ピバルアミドフェニル基、ペンタフルオロフェニル基、ｐ−スルホナトフェニル基、ｐ−メトキシフェニル基、ｐ−トリル基、メシチル基、４−ピリジル基、１−メチル−４−ピリジル基等を挙げることができる。
さらに、本発明にかかるカソードの触媒層に備えられる炭素は、通常のＰＥＦＣにおいて触媒が担持される炭素等を好適に用いることが可能であり、当該炭素の具体例としては、カーボンブラック等を挙げることができる。加えて、本発明にかかるカソードの触媒層に備えられる触媒及びプロトン伝導体は、通常のＰＥＦＣにおいて使用されるもの等を好適に用いることが可能である。触媒の具体例としては、ルテニウム、ロジウム、パラジウム、オスミウム、イリジウム、白金、及び、これらを主成分とする合金等を、プロトン伝導体の具体例としては、含フッ素イオン交換樹脂を備えるフッ素系の電解質成分や、炭化水素系の電解質成分等を挙げることができる。

In the present invention, the metal porphyrin refers to a metal atom such as a cobalt atom, a copper atom, an iron atom, or a manganese atom coordinated to the center of 5,10,15,20-tetraarylporphyrin, Specific examples of the aryl group related to 5,10,15,20-tetraarylporphyrin include phenyl group, o-pivalamidophenyl group, pentafluorophenyl group, p-sulfonatophenyl group, p-methoxyphenyl group, Examples thereof include a p-tolyl group, a mesityl group, a 4-pyridyl group, and a 1-methyl-4-pyridyl group.
Further, as the carbon provided in the catalyst layer of the cathode according to the present invention, carbon or the like on which a catalyst is supported in a normal PEFC can be suitably used. Specific examples of the carbon include carbon black and the like. be able to. In addition, as the catalyst and proton conductor provided in the cathode catalyst layer according to the present invention, those used in ordinary PEFC can be suitably used. Specific examples of the catalyst include ruthenium, rhodium, palladium, osmium, iridium, platinum, and alloys containing these as main components. Specific examples of the proton conductor include fluorine-based ion exchange resins. Examples thereof include an electrolyte component and a hydrocarbon-based electrolyte component.

  The invention according to claim 2 is the fuel cell according to claim 1, wherein the metalloporphyrin is cobalt porphyrin.

  Here, the cobalt porphyrin means a cobalt atom coordinated to the center of the 5,10,15,20-tetraarylporphyrin.

  The invention according to claim 3 is a method of manufacturing a fuel cell comprising an electrolyte membrane, and an anode and a cathode disposed on both sides of the electrolyte membrane, wherein the anode and the cathode include at least a catalyst layer, An immobilization step of immobilizing an imidazole group on the carbon surface, and after the immobilization step, a metal porphyrin is coordinated to the imidazole group to form an oxygen adsorbent, and after the coordination step, an oxygen adsorbent, The above-mentioned problem is solved by a method for producing a fuel cell, comprising a catalyst layer production step of producing a catalyst layer comprising a catalyst and a proton conductor.

  Here, in the present invention according to claim 3, the carbon, the imidazole group, the metal porphyrin, the catalyst, and the proton conductor can be the same as the substance according to the invention according to claim 1. .

  According to the first aspect of the present invention, since the carbon-imidazole-metal porphyrin can be bonded in an electron-sharing manner through the imidazole group, the metal porphyrin is attached to the carbon surface without heating. It becomes possible to fix the catalyst, and it is possible to support a catalyst (for example, platinum or the like; the same applies hereinafter) on the carbon surface. Here, the metal porphyrin has a property of selectively adsorbing oxygen (hereinafter referred to as “oxygen adsorption performance”), and starts to be decomposed when heated to 400 to 600 ° C. or higher. According to the present invention, since heating at the time of fixing to the carbon surface is unnecessary, it is possible to provide a cathode catalyst layer capable of effectively expressing the oxygen adsorption performance of metal porphyrin. That is, with this configuration, oxygen can be effectively supplied to the cathode catalyst via the metal porphyrin. Therefore, according to the first aspect of the present invention, it is possible to provide a fuel cell capable of improving the power generation performance by effectively supplying oxygen to the catalyst. Furthermore, according to such a fuel cell, a sufficient amount of oxygen can be supplied to the catalyst even at high output, and therefore a fuel cell capable of suppressing a decrease in power generation performance at high output is provided. It becomes possible.

  According to the invention described in claim 2, an oxygen adsorbent formed by fixing cobalt porphyrin on the carbon surface via an imidazole group, a catalyst, and a proton conductor (for example, a fluorine-containing ion exchange resin). It is possible to provide a fuel cell provided with a cathode catalyst layer provided with an electrolyte component and the like. Here, cobalt porphyrin has excellent oxygen adsorption performance. Therefore, according to the invention described in claim 2, it is possible to provide a fuel cell capable of improving the power generation performance by supplying oxygen to the catalyst even more effectively.

  According to the invention described in claim 3, since the metal porphyrin is coordinated to the imidazole group after fixing the imidazole group to the carbon surface, the metal porphyrin is attached to the carbon surface via the imidazole group without heating. A fixed oxygen adsorbent can be formed. Since a catalyst layer including such an oxygen adsorbent, a catalyst, and a proton conductor is produced, if such a catalyst layer is disposed on the cathode side of the electrolyte membrane, oxygen is effectively supplied to the catalyst. Thus, a fuel cell capable of improving the power generation performance can be obtained. And according to this fuel cell, it also becomes possible to suppress the fall of the power generation performance at the time of high output. Therefore, according to the invention described in claim 3, it is possible to improve power generation performance by effectively supplying oxygen to the catalyst, and to suppress a decrease in power generation performance at the time of high output. It is possible to provide a method for manufacturing a fuel cell.

  In order to improve the power generation performance of the fuel cell, it is effective to improve the reaction efficiency of the cathode, and the electrochemical reaction at the cathode is caused by the association of oxygen, protons and electrons on the catalyst. Even if the performance of the catalyst itself is improved as in the past, it is difficult to improve the efficiency of the electrochemical reaction if the amount of oxygen supplied onto the catalyst is insufficient. Therefore, in order to improve the reaction efficiency, it is desirable to increase the amount of oxygen and proton supplied to the catalyst.

  On the other hand, when a conventional fuel cell is operated at a high output, the consumption of protons and oxygen increases, but the diffusion rate of oxygen from the outside to the catalyst surface of the cathode catalyst layer hardly changes. Therefore, when the amount of oxygen consumed on the catalyst exceeds the amount of oxygen supplied onto the catalyst, oxygen on the catalyst is deficient, so that the electrochemical reaction at the cathode is delayed, resulting in a decrease in power generation performance. .

  That is, if the supply efficiency of oxygen supplied to the catalyst is improved, it is possible to improve the power generation performance of the fuel cell, and this improvement in supply efficiency will be particularly noticeable at high output of the fuel cell. It is done.

  The present invention has been made from such a viewpoint, and the gist thereof includes an oxygen adsorbent formed by fixing a metal porphyrin on a carbon surface via an imidazole group, a catalyst, and a proton conductor. By providing a fuel cell including a cathode catalyst layer, it is possible to provide a fuel cell capable of improving the power generation performance by effectively supplying oxygen to the catalyst, and a method for manufacturing the fuel cell. .

  Hereinafter, embodiments of the fuel cell of the present invention and a method for manufacturing the fuel cell will be described more specifically with reference to the drawings.

1. Configuration of Fuel Cell FIG. 1 is a conceptual diagram schematically showing the vicinity of the surface of an oxygen adsorbent and a catalyst provided in a cathode catalyst layer of a fuel cell according to the present invention, and an arrow in the figure indicates oxygen toward the catalyst. Indicates the direction of movement. FIG. 2 is a cross-sectional view schematically showing a fuel cell according to the present invention, and the horizontal direction in the figure is the stacking direction of the catalyst layers.

  As shown in FIG. 1, the cathode catalyst layer according to the present invention has a metal porphyrin (for example, cobalt (II) -5, 10, 15, 20-) through an imidazole group (for example, N-benzylimidazole) 2. Tetraphenylporphyrin, etc. In the following, it may be described as “Co porphyrin”.) Oxygen adsorbent 4 formed by fixing 3 on the surface of carbon (for example, carbon black) 1, carbon 1 And a catalyst (for example, platinum or the like) 5 supported on the proton conductor (for example, an electrolyte component (for example, Nafion or the like, Nafion is a registered trademark of DuPont, USA)) containing a fluorine-containing ion exchange resin. Is distributed.

  On the other hand, as shown in FIG. 2, the fuel cell 100 according to the present invention includes an electrolyte membrane 11, an MEA 15 including an anode catalyst layer 12 a and a cathode catalyst layer 13 a laminated on both sides of the electrolyte membrane 11, and both sides of the MEA 15. The anode diffusion layer 12b and the cathode diffusion layer 13b disposed on the anode diffusion layer 12b and the separators 16 and 17 disposed outside the anode diffusion layer 12b and the cathode diffusion layer 13b. 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. In the fuel cell 100, the electrolyte membrane 11, the anode catalyst layer 12 a, and the cathode catalyst layer 13 a have electrolyte components (for example, a fluorine-containing ion exchange resin typified by Nafion or the like. Hereinafter, simply described as “Nafion”). Is). The anode catalyst layer 12a and the cathode catalyst layer 13a are provided with carbon particles (hereinafter referred to as “platinum-supported carbon”) on which platinum functioning as a catalyst for electrochemical reaction is provided. The diffusion layer 12b and the cathode diffusion layer 13b are made of, for example, carbon paper made of carbon fiber. In the separators 16 and 17, reaction gas supply paths 18a, 18a,..., And 18b, 18b,... Are formed on the anode 12 and cathode 13 sides, and the reaction gas supply paths 18a, 18a,. Is supplied with a hydrogen-containing substance (hereinafter referred to as “hydrogen”), while an oxygen-containing substance (hereinafter referred to as “air”) is supplied to the reaction gas supply paths 18b, 18b,. .), And cooling medium channels 19, 19,... Are formed on the opposite surfaces.

  The fuel cell according to the present invention will be described below with reference to FIGS. 1 and 2 as appropriate.

  During power generation of the fuel cell 100, hydrogen supplied from the reaction gas supply paths 18a, 18a,... Is decomposed on the catalyst 5 of the anode electrode layer 12a (electrochemical reaction occurs), thereby causing protons 8A, 8A,. Are generated, and the protons 8A, 8A,... Pass through the electrolyte membrane 11 and reach the cathode electrode layer 13a, while the electrons 8B, 8B,. The electrode layer 13a is reached. On the other hand, oxygen 7, 7,... Contained in the air supplied from the reaction gas supply passages 18b, 18b,... Reaches the cathode electrode layer 13a, and oxygen 7 on the catalyst 5 of the cathode electrode layer 13a. .., And protons 8A, 8A,... And electrons 8B, 8B,... That have moved from the anode electrode layer 12a react (electrochemical reaction) to generate water (water vapor) 9, 9,. The

  Here, in the fuel cell 100 according to the present invention, the cathode catalyst layer 13a includes the oxygen adsorbent 4, the catalyst 5 supported on the carbon 1, and the proton conductor 6, and the oxygen adsorbent 4 is Co porphyrin 3 having excellent oxygen adsorption performance is fixed to carbon 1 through imidazole group 2. Therefore, when air is supplied to the cathode catalyst layer 13a as described above, oxygen 7, 7,... Contained in the air is attracted to the Co porphyrin 3. On the other hand, a catalyst 5 is supported on the carbon 1 on which the Co porphyrin 3 is fixed. That is, by adopting such a configuration, it is possible to improve the oxygen concentration in the vicinity of the catalyst 5 by attracting the oxygen 7, 7,... Contained in the air supplied to the cathode catalyst layer 13a by the Co porphyrin 3. Therefore, it becomes possible to selectively supply oxygen 7, 7,... In the air to the catalyst 5.

  FIG. 3 is a schematic diagram showing Co porphyrin immobilized on carbon via an imidazole group. FIG. 3 (A) shows the coordination form of Coporphyrin 3 fixed to carbon 1 via a 3- (imidazol-1-yl) propylamide group, and FIG. 3 (B) shows 3- (imidazole-1 -Yl) Coordination forms of Coporphyrin 3 fixed to carbon 1 via a propylsulfonamide group are shown respectively.

  As shown in the figure, the Co porphyrin 3 is fixed to the carbon 1 by coordination via a nitrogen atom (N) contained in the imidazole groups 2 and 2. Thus, by fixing through the imidazole groups 2 and 2, the heat treatment for fixing the Co porphyrin 3 to the carbon 1 becomes unnecessary. Here, in the case where the macrocyclic compound complex is directly fixed to carbon as in the conventional case, for example, it is necessary to undergo a heat treatment for heating to a temperature of about 700 to 1100 ° C. However, for example, when the metal porphyrin is heated to such a temperature, at least a part of the metal porphyrin is decomposed, and it becomes difficult to effectively exhibit the oxygen adsorption performance of the metal porphyrin. Therefore, in the present invention, the Co porphyrin 3 is fixed to the carbon 1 through the imidazole groups 2 and 2 and the heat treatment is not required, so that the oxygen adsorption performance of the Co porphyrin 3 can be effectively expressed.

  As described above, in the cathode catalyst layer 13a in the present invention, oxygen 7, 7,... Can be selectively supplied to the catalyst 5, and the efficiency of the electrochemical reaction occurring in the cathode catalyst layer 13a can be improved. Improve power generation performance because it becomes possible. That is, according to the present invention, it is possible to provide the fuel cell 100 capable of improving the power generation performance by effectively supplying the oxygen 7, 7,...

  Further, according to the fuel cell 100 according to the present invention, since a highly efficient electrochemical reaction is possible at the cathode 13, it is possible to suppress a decrease in power generation performance at the time of high output of the fuel cell 100. Hereinafter, the power generation performance deterioration suppressing effect at the time of high output will be described with reference to the drawings.

  FIG. 4 is an enlarged schematic view showing the vicinity of the surface of platinum-supporting carbon provided in the cathode catalyst layer. 4A shows a low output state, FIGS. 4B and 4C show a high output state, and FIGS. 4A and 4B show platinum support in a conventional fuel cell. FIG. 4C shows the vicinity of the surface of the carbon, and FIG. 4C shows the vicinity of the surface of the platinum-supporting carbon in the fuel cell of the present invention. 4A to 4C, substances having the same properties as those in FIG. 1 are denoted by the same reference numerals as those used in FIG. 1, and detailed description thereof is omitted as appropriate. In addition, the linear arrow in a figure represents the moving direction of the oxygen which goes to a catalyst, and the curved arrow represents that the electrochemical reaction in the cathode has arisen, respectively.

  FIG. 4A is an enlarged schematic view showing the vicinity of the surface of platinum-supporting carbon provided in a conventional fuel cell. As described above, even in a conventional fuel cell, oxygen 7, 7,... Is supplied to the cathode, and protons 8A, 8A,..., Electrons 8B, 8B,. By reacting above, water 9, 9,... Is generated. When the output is low, the amount of oxygen 7, 7,... And protons 8A, 8A,... Consumed on the catalysts 5, 5,. The probability of occurrence is relatively low.

  On the other hand, at the time of high output, a large amount of oxygen 7, 7, ... and protons 8A, 8A, ... are consumed on the catalysts 5, 5, ..., while oxygen 7 reaching the surface of the catalysts 5, 5, .... , 7... Hardly change the diffusion rate. Therefore, when a conventional fuel cell is operated at a high output, an oxygen-deficient region 7x is formed in the cathode catalyst layer or the like (see FIG. 4B). When the oxygen-deficient region 7x is formed, the oxygen 7a, 7a,... Existing in the region between the oxygen-deficient region 7x and the catalysts 5, 5,. It takes time for the oxygen 7b, 7b, ... existing on the opposite side of the catalysts 5, 5, ... to reach the top of the catalysts 5, 5, .... Therefore, an electrochemical reaction cannot occur on the catalysts 5, 5,... During the time, and as a result, the power generation characteristics are deteriorated.

  On the other hand, as described above, in the fuel cell according to the present invention, the metal porphyrin 3 typified by Co porphyrin having oxygen adsorption performance is fixed to the carbon 1 through the imidazole group 2, and the catalyst 5 from the outside. It is possible to increase the diffusion rate of oxygen 7, 7,. Therefore, even if the amount of oxygen 7, 7,... Consumed on the catalysts 5, 5,... Is increased by operating the fuel cell 100 at a high output, the oxygen 7, 7,. Therefore, the probability that the oxygen-deficient region 7x is formed can be reduced, and the formation of the oxygen-deficient region 7x can be prevented (FIG. 4C )reference). Therefore, according to the fuel cell 100 of the present invention, it is possible to suppress a decrease in power generation performance at the time of high output.

2. Manufacturing Method of Fuel Cell The fuel cell of the present invention is characterized in that a catalyst layer including an oxygen adsorbent, a catalyst, and a proton conductor is provided. Below, the manufacturing method of the fuel cell of the present invention concerning an embodiment is explained.

  In order to produce the catalyst layer according to this embodiment, it is necessary to form an oxygen adsorbent provided in the catalyst layer. Here, in the oxygen adsorbent according to the present embodiment, a metal porphyrin (eg, Co porphyrin) is immobilized on the surface of carbon (eg, carbon black) via an imidazole group (eg, N-benzylimidazole). Is formed. Therefore, in order to produce the oxygen adsorbent, first, N-benzylimidazole is dissolved in an organic solvent such as chloroform, and then imidazoles are adsorbed on the carbon surface by dispersing carbon such as carbon black. Alternatively, after oxidizing the carbon surface with an oxidizing agent such as potassium permanganate in advance to oxidize part of the surface to a carboxyl group, 3- (imidazol-1-yl) is present in the presence of a condensing agent such as DCC. ) Fix the imidazole group to the carbon surface by reacting with propylamine to form an amide bond. There is also a method of fixing imidazole by forming a sulfonic acid group on a carbon surface using a sulfonating agent such as sulfur trioxide and then reacting with 3- (imidazol-1-yl) propylamine to form a sulfonamide. Yes (hereinafter referred to as “fixing step”).

  Next, after the fixing step, the metal porphyrin is dissolved in an organic solvent such as chloroform, the carbon to which the imidazole is fixed is dispersed, and the metal porphyrin is coordinated to the imidazole group by stirring for a certain time (hereinafter, “ "Coordination process").

  Further, after the coordination step, the oxygen adsorbent, a catalyst (for example, platinum) and a proton conductor (for example, Nafion) are mixed with a solvent (for example, a mixture of water, methanol, and 2-propanol). ) To produce a paste-like catalyst layer (hereinafter referred to as “catalyst layer production step”). The paste-like catalyst layer thus prepared is then coated on the cathode side surface of an electrolyte membrane (for example, Nafion etc.) and dried to provide an oxygen adsorbent, a catalyst, and a proton conductor. It becomes possible to produce a cathode catalyst layer. The anode catalyst layer is prepared by a method such as applying and drying a paste-like catalyst layer formed by a method such as dispersing the catalyst and proton conductor in the solvent on the anode side surface of the electrolyte membrane. The MEA can be manufactured through such a process.

  In the present invention, the imidazole group is preferably insoluble in the organic solvent and stable at the operating temperature of the fuel cell, and its weight average molecular weight is preferably 100 or more, and is dissolved in the solvent. From the viewpoint of enabling it, the weight average molecular weight is preferably 1000 or less. More preferably, it is 150 or more and 500 or less.

  Further, from the viewpoint of fixing the metal porphyrin to the carbon surface, the mass of the imidazole group is preferably 1 part by mass or more with respect to 100 parts by mass of carbon, and from the viewpoint of reducing resistance polarization, the same mass. Is preferably 50 parts by mass or less with respect to 100 parts by mass of carbon. More preferably, they are 5 to 20 mass parts.

  Furthermore, in the present invention, the metal porphyrin is preferably insoluble in the organic solvent and stable at the operating temperature of the fuel cell, and its weight average molecular weight is preferably 500 or more. The weight average molecular weight is preferably 2,000 or less from the viewpoint of being soluble in the solvent. More preferably, it is 600 or more and 1200 or less.

  In addition, the mass of the metal porphyrin is preferably 5 parts by mass or more with respect to 100 parts by mass of the catalyst from the viewpoint of expressing significant oxygen adsorption performance, and the same mass from the viewpoint of reducing resistance polarization. Is preferably 20 parts by mass or less with respect to 100 parts by mass of the catalyst. More preferably, they are 10 to 20 mass parts.

  In the oxygen adsorbent according to the present invention, the amount of metal porphyrin or imidazole adsorbed is determined based on the BET specific surface area of carbon to be adsorbed and the molecular occupation area of the metal porphyrin. The amount that can be covered can be set.

In the present invention, the solvent for dispersing the oxygen adsorbent, the catalyst, and the proton conductor is not particularly limited as long as they can be dispersed substantially uniformly. Specific examples thereof include water, methanol, ethanol, Or a hydrophilic solvent prepared by mixing at least one or more of aprotic polar solvents such as lower alcohols such as isopropanol, polyhydric alcohols such as ethylene glycol or diethylene glycol, or dimethyl sulfoxide or diethylformamide Can be mentioned.
In addition, it is preferable that the mass of the said solvent mixed with water shall be 10 mass parts or more and 90 mass parts or less with respect to 100 mass parts of water from a viewpoint of making the dispersibility of carbon and the solubility of an adsorbent high. More preferably, it is 20 to 80 parts by mass.

  In the above description, for convenience, N-benzylimidazole as the imidazole group, cobalt (II) -5,10,15,20-tetraphenylporphyrin as the metal porphyrin, carbon black as the carbon, platinum as the catalyst, proton conductor As an example, a mode in which an electrolyte component including a fluorine-containing ion exchange resin is provided has been described. However, the fuel cell of the present invention and the method for manufacturing the fuel cell are not limited to the mode.

  Specific examples of the imidazole group according to the present invention include alkylimidazole and the like. More specifically, N-benzylimidazole, N-methylimidazole, 2-methylimidazole, N-laurylimidazole, poly (N -Vinylimidazole), poly (N-vinylimidazole-co-octylmethacrylate), N-tritylimidazole, 3- (imidazol-1-yl) propylamine and the like.

  In addition, specific examples of metal porphyrins include 5,10,15,20-tetraarylporphyrin, and specific examples of aryl groups related to 5,10,15,20-tetraarylporphyrin include phenyl. Group, o-pivalamidophenyl group, pentafluorophenyl group, p-sulfonatophenyl group, p-methoxyphenyl group, p-tolyl group, mesityl group, 4-pyridyl group, 1-methyl-4-pyridyl group, etc. Can be mentioned. Furthermore, specific examples of the metal atom to be coordinated to the center of the metal porphyrin include a cobalt atom, a copper atom, an iron atom, and a manganese atom.

In addition, specific examples of carbon according to the present invention include carbon black and activated carbon, and the specific surface area is 200 m ² / g or more from the viewpoint of enabling the catalyst to be supported effectively. It is preferable.

  Further, specific examples of the catalyst according to the present invention include ruthenium, rhodium, palladium, osmium, iridium, platinum, and alloys containing these as main components, and can express good catalytic performance. From the viewpoint, platinum or a platinum alloy is preferable.

  Furthermore, specific examples of the proton conductor according to the present invention include a fluorine-based electrolyte component having a fluorine-containing ion exchange resin, a hydrocarbon-based electrolyte component, and the like. From the viewpoint of enabling conduction, a sulfonic acid type perfluorocarbon polymer is preferably used.

  For the sake of convenience, in the above description, the fuel cell including the separator in the form in which the reaction gas supply path is formed on the MEA side has been described. Instead, for example, a flat separator in which no reaction gas supply path is formed on the MEA side may be used. In the case of such a fuel cell, the layers to be brought into contact with the separator (in the fuel cell according to the above embodiment, the anode diffusion layer and the cathode diffusion layer) are made of stainless steel manufactured by a plating method, a foaming method, or the like, What is necessary is just to set it as the fuel cell of the form which forms with porous bodies, such as foam metals, such as titanium or nickel, or a sintered metal, and a reactive gas is supplied to the said layer.

  Furthermore, in the above description, a fuel cell having an anode diffusion layer and a cathode diffusion layer has been described. However, even when an anode diffusion layer and / or a cathode diffusion layer are not provided, good power generation performance can be obtained. Alternatively, the fuel cell according to the present invention may have a form in which the anode diffusion layer and / or the cathode diffusion layer is not provided.

500 mg of carbon and 20 mg of benzylimidazole are put in a container, an organic solvent such as chloroform (about 200 mL) is added and stirred at a constant temperature to fix benzylimidazole on the surface of carbon, and 100 mg of Co porphyrin is further added to the container. Then, by stirring at a constant temperature, Co porphyrin was immobilized on the carbon surface via benzylimidazole to obtain an oxygen adsorbent. Next, the oxygen adsorbent, Nafion, and platinum-supported carbon are mixed at a mass ratio of 1: 1: 0.1, and the mixture is mixed with water, methanol, and 2-propanol at 8: 1: A paste-like catalyst layer P1 was produced by dispersing the mixture in a mixed liquid having a mass ratio of 1.
Thereafter, the cathode catalyst layer was formed by applying and drying the paste-like catalyst layer P1 on one surface of the electrolyte membrane (Nafion 112 (manufactured by DuPont)). Further, a paste-like catalyst layer P2 was prepared in the same manner as in the above-described process except that the oxygen adsorbent was not mixed, and this catalyst layer P2 was applied to the other surface of the electrolyte membrane and dried. Such MEA was produced. Note that the MEA according to the comparative example was manufactured by applying and drying a paste-like catalyst layer P2 on both surfaces of the electrolyte membrane.

  Thus, the diffusion layer comprised by the carbon paper which consists of carbon fiber is arrange | positioned on both sides of MEA concerning the Example obtained in this way, and MEA concerning a comparative example, Furthermore, reaction gas is outside the said diffusion layer. By disposing a separator in which a flow path was formed, the fuel battery cell according to the example and the fuel battery cell according to the comparative example were respectively produced.

  Hydrogen gas (80 ° C., relative humidity 100%) from the anode side and oxygen (80 ° C., relative humidity 100%) from the cathode side to each of the fuel cell according to the example and the fuel cell according to the comparative example And the cell temperature was maintained at 80 ° C., and a deterioration acceleration test was conducted. The results of the accelerated deterioration test are also shown in Table 1. Here, Table 1 shows the fuel cell according to the embodiment when the cell voltage (V) of the fuel cell is a specific value (0.8 V, 0.7 V, 0.6 V, and 0.5 V). And the electric current value (A) measured in the fuel cell concerning a comparative example is shown. The cell voltage (OCV) when no current was flowing in the deterioration acceleration test was 9.5V.

  From Table 1, when the cell voltage (V) of the fuel cell according to the example and the fuel cell according to the comparative example is the same, the current value (A) of the fuel cell according to the example is the fuel according to the comparative example. It was larger than the current value (A) of the battery cell. That is, it was confirmed that the fuel cell according to the example has a power generation performance superior to that of the fuel cell according to the comparative example. This is presumably because the amount of oxygen supplied to the catalyst was increased by fixing Co porphyrin on the carbon surface via benzylimidazole. Therefore, from the above-described deterioration acceleration test, it was confirmed that according to the present invention, it is possible to provide a fuel cell capable of improving the power generation performance by effectively supplying oxygen to the catalyst.

It is a conceptual diagram which shows roughly the oxygen adsorber with which the cathode catalyst layer of the fuel cell concerning this invention is equipped, and the surface vicinity of a catalyst. 1 is a cross-sectional view schematically showing a fuel cell according to the present invention. It is the schematic which shows Co porphyrin fixed to carbon via the imidazole group. It is the schematic which expands and shows the surface vicinity of the platinum carrying | support carbon with which a cathode catalyst layer is equipped.

Explanation of symbols

1 carbon 2 imidazole group 3 metal porphyrin (Co porphyrin)
4 Oxygen adsorbent 5 Catalyst (platinum)
6 Proton conductor 7 Oxygen 8A Proton 8B Electron 9 Water 11 Electrolyte membrane 12 Anode 12a Anode catalyst layer 12b Anode diffusion layer 13 Cathode 13a Cathode catalyst layer 13b Cathode diffusion layer 15 MEA
16, 17 Separator 100 Fuel cell (fuel cell)

Claims (3)

A fuel cell comprising an electrolyte membrane, and an anode and a cathode disposed on both sides of the electrolyte membrane,
The anode and cathode include at least a catalyst layer,
A fuel cell comprising an oxygen adsorbent formed by fixing a metal porphyrin on a carbon surface via an imidazole group, a catalyst, and a proton conductor on the catalyst layer of the cathode. The fuel cell according to claim 1, wherein the metalloporphyrin is cobalt porphyrin. A fuel cell manufacturing method comprising: an electrolyte membrane; and an anode and a cathode disposed on both sides of the electrolyte membrane, wherein the anode and the cathode include at least a catalyst layer,
A fixing step of fixing an imidazole group on the carbon surface;
After the fixing step, a metal porphyrin is coordinated to the imidazole group to form an oxygen adsorbent, and a coordination step;
A method for producing a fuel cell, comprising: a catalyst layer production step of producing a catalyst layer comprising the oxygen adsorbent, a catalyst, and a proton conductor after the coordination step.

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