JPWO2005006470A1 - ELECTRODE FOR FUEL CELL, FUEL CELL USING THE ELECTRODE, AND METHOD FOR PRODUCING THE ELECTRODE - Google Patents

Abstract

A mixture of a proton conductive gel having a dispersed phase composed of a phosphate molecular chain containing at least one of Ca ion, Mg ion and Zn ion and a dispersion medium composed of water and carbon particles e carrying catalyst f is prepared. Then, an electrode was formed using the mixture. Since the proton conducting gel has a smaller molecular weight than that of the solid polymer electrolyte and has a high affinity with the carbon particles e, in the electrode a, the electrolyte c made of the proton conducting gel has a gap g in the aggregate b of the carbon particles e. Infiltrate up to and form many three-phase interfaces. This provides an electrode with high catalyst utilization efficiency.

Description

  The present invention relates to an electrode used for a fuel cell, a fuel cell provided with the electrode, and a method for manufacturing the electrode.

  Fuel cells are classified into several types depending on the type of electrolyte membrane. Among these, solid polymer fuel cells using a solid polymer as the electrolyte membrane are smaller and have higher output than any other method. It operates at a low temperature, and is regarded as the next generation mainstay as a small-scale on-site type, mobile (on-vehicle) and portable fuel cell. Solid polymer fuel cells have entered the practical development stage and are used in trial production or testing. The electrolyte membrane of this fuel cell has perfluoroalkylene as the main skeleton, which is chemically stable and has high proton conductivity even at room temperature, and a sulfonic acid group, a carboxylic acid group, etc. at the end of the perfluorovinyl ether side chain A fluorine-based polymer having an ion exchange group is used. Nafion (registered trademark) is known as a typical fluorine-based polymer electrolyte.

  As shown in FIG. 4, the main part of a general polymer electrolyte fuel cell is a collection of an electrolyte membrane y, an electrode a bonded to both surfaces thereof, and a carbon paper bonded to the outside of the electrode a. It is constituted by a membrane electrode assembly x formed by integrating the electric body z.

An electrode used for a fuel cell includes an electrolyte as a path for ions to move, a conductor as a path for electrons to move, and a catalyst for causing an electrochemical reaction. Inside the electrode, gas (hydrogen or oxygen) is contained. A pore is formed as a supply path. The following shows the electrochemical reaction (electrode reaction) that occurs at each electrode when hydrogen is supplied to the fuel electrode and oxygen is supplied to the oxygen electrode.
Fuel electrode: H ₂ → 2H ⁺ + 2e ⁻
Oxygen electrode: 1 / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O
Total reaction: H ₂ + 1 / 2O ₂ → H ₂ O

In this reaction, a three-phase interface (electrolyte, conductor carrying a catalyst, and pores are in contact with each other, which can simultaneously exchange gas (hydrogen or oxygen), proton (H ⁺ ), and electron (e ⁻ ). It can only progress in (part). In addition, a catalyst is indispensable for this reaction, and the electrode reaction occurs only when the catalyst is present in the vicinity of the three-phase interface.

  More specifically, in a solid polymer fuel cell electrode, a solid polymer is used as an electrolyte, and carbon particles are used as a conductor. The catalyst is made of platinum or an alloy containing platinum as a main component and is supported on carbon particles. Then, after mixing the conductor carrying the catalyst and the solid polymer electrolyte solution, the electrode is manufactured by forming into a layer or impregnating the laminate of the conductor with the solid polymer electrolyte solution. In such an electrode, the solid polymer electrolyte adheres to the surface of the conductor and coats the catalyst supported on the carbon particles, thereby forming a three-phase interface structure in the vicinity of the catalyst.

By the way, in this polymer electrolyte fuel cell electrode, platinum (or platinum alloy) is used as a catalyst, but platinum is a rare element and expensive, and the material cost of the catalyst accounts for a large proportion of the production cost of the electrode. ing. For this reason, development of an electrode with high catalyst utilization efficiency that can cause a sufficient electrode reaction with a small amount of catalyst has become active (for example, Patent Document 1).
JP-A-7-134996

  In the above electrode, one of the factors hindering the improvement of the utilization efficiency of the catalyst is a problem of the solid polymer electrolyte constituting the electrode. This will be described with reference to FIGS. FIG. 1 is a schematic diagram showing a cross section of an electrode a using a solid polymer as an electrolyte. As described above, the electrode a is composed of the aggregate b of the carbon particles (conductor) e carrying the catalyst and the electrolyte c, and the pores d through which the gas passes are formed. Here, the illustrated aggregate b is not a single carbon particle e but a collection of a plurality of carbon particles e. FIG. 2 is a schematic schematic view showing the inside of the aggregate b in an enlarged manner. Thus, the aggregate b is composed of a plurality of carbon particles e, and the catalyst f existing on the outer surface of the aggregate b comes into direct contact with the electrolyte c to form a three-phase interface. On the other hand, a large number of catalysts f are also carried on the carbon particles e inside the aggregate b. However, since the solid polymer electrolyte has a large molecular weight, the electrolyte c hardly penetrates into the gap g formed between the carbon particles e. Therefore, in the conventional electrode a, there are only a few three-phase interfaces in the gap g inside the aggregate b, and most of the catalyst f in the gap g does not contribute to the electrode reaction and is wasted. It was.

  An object of the present invention is to provide an electrode with high catalyst utilization efficiency, a method for producing the electrode, and a low-cost and high-power fuel cell using the electrode. Is.

  The present invention is an electrode used in a fuel cell, and has an electrolyte composed of a phosphate molecular chain containing at least one of Ca ion, Mg ion and Zn ion, and a conductor carrying a catalyst. Electrode.

  The electrolyte composed of such phosphate molecular chains is made from a proton-conductive “proton conductive gel” previously reported by the present inventors in Chemistry Letters, 820-821 (2001). This proton conducting gel is a viscous gel-like proton conductor obtained by rapidly reacting phosphate glass powder with water at room temperature, and the phosphate glass obtained by the melting method is mixed with water. It exists in the periphery of each OH group of the phosphate molecular chain, and a dispersed phase consisting of a phosphate molecular chain having a linear structure or / and a cyclic structure in which an OH group is bonded to a phosphorus atom by reaction. It has the dispersion medium which consists of water, It is characterized by the above-mentioned. The inventors of the present invention have focused on the possibility of this proton conducting gel as an electrode material, and as a result of intensive studies, have reached the present invention.

The proton conductive gel will be described in detail. The proton conductive gel is obtained by pulverizing phosphate glass containing at least one of Ca ions, Mg ions, and Zn ions and reacting it with water. The phosphate glass can be obtained by a melting method, that is, by rapidly cooling the phosphate to a glass transition temperature or lower after melting the phosphate. In order to obtain a proton conducting gel in high yield, it is desirable that the phosphate molecular chain constituting the proton conducting gel contains phosphoric acid in a range of 30 to 75 mol% in terms of P ₂ O ₅ , Furthermore the contains in the range of 40 to 60 mol% phosphoric acid in terms _{of P} 2 _{O 5} is more preferable. On the other hand, the total amount of Ca ions, Mg ions and Zn ions contained in the phosphate molecular chain is preferably in the range of 25 to 70 mol% in terms of oxide, and 40 to 60 mol% in terms of oxide. A range is more desirable.

  And the electrode of this invention uses this proton conductive gel as an electrolyte material of an electrode. Here, the electrolyte constituting the electrode of the present invention may be a proton conductive gel itself, or may be one in which the proton conductive gel is dried by heat treatment or the like and becomes only a phosphate molecular chain as a dispersion medium. I do not care. Further, the electrolyte of the electrode of the present invention may be a mixture with not only the phosphate molecular chain but also other solid polymer electrolytes.

  This proton conducting gel has a high affinity for carbon particles, and the phosphate molecular chains in the proton conducting gel are composed of linear or cyclic phosphate molecular chains of various lengths. Most of them are lower in molecular weight than solid polymer electrolytes, and therefore easily penetrate into the gaps formed in the aggregates of carbon particles. For this reason, in the electrode of this invention, many three-phase interfaces can be formed rather than the electrode using the conventional solid polymer electrolyte. That is, in the electrode of the present invention, as shown in the schematic diagram of FIG. 3, a large amount of electrolyte c enters the gap g inside the aggregate b and adheres to the surface of the carbon particles e. Many three-phase interfaces are formed in the vicinity of the catalyst f existing inside the aggregate b. Therefore, in the present invention, since the catalyst in the aggregate that has not been used in the conventional electrode is used in the electrode reaction, the utilization efficiency of the catalyst is increased.

  In addition, since the proton-conducting electrolyte comprising the phosphate molecular chain that constitutes the electrode of the present invention does not contain fluorine, the load on the environment during synthesis and disposal is small. In particular, in an electrode using a conventional fluorine-based solid polymer as an electrolyte, as described in JP-A-61-138541, when recovering platinum contained in a catalyst when the fuel cell is discarded, Because of the fluorine-based solid polymer, it is difficult to dissolve platinum by directly immersing the electrode in aqua regia, and a complicated recovery method was required, but the electrode of the present invention contains fluorine. The platinum can be easily recovered by directly treating the electrode with aqua regia.

  The amount of the three-phase interface formed in the electrode of the present invention is adjusted by the amount of the proton conducting gel solvent, the type of solvent, the ratio of the electrolyte to the conductor, the component composition of the proton conducting gel, and the like. For example, when the proportion of the electrolyte and the conductor is too large, the pore portion in the electrode is reduced and it is difficult to ensure a sufficient gas supply path. On the other hand, when the composition ratio of the electrolyte is too small, the proton conduction path in the electrode is reduced and it is difficult to form a three-phase interface. For this reason, in order to form a sufficient three-phase interface in the electrode, the average composition ratio between the electrolyte and the conductor is preferably in the range of 20:80 to 80:20 by mass ratio. Furthermore, it is more desirable that the average composition ratio of the electrolyte and the conductor is in the range of 30:70 to 70:30 by mass ratio. The mass of the electrolyte does not include moisture, and the mass of the conductor includes the mass of the supported catalyst.

  The electrode manufacturing method of the present invention carries a proton conductive gel having a dispersed phase composed of a phosphate molecular chain containing at least one of Ca ions, Mg ions and Zn ions and a dispersion medium composed of water, and a catalyst. A mixture with a conductor is prepared, and an electrode is formed using the mixture.

  The mixture can be obtained by sufficiently kneading a conductor carrying a catalyst in the proton conducting gel. In this mixture, the conductor and the proton conducting gel are mixed, and the phosphate molecular chain of the proton conducting gel penetrates into the carbon particle aggregate. The proton conductive gel may be diluted by adding water or an organic solvent as necessary. In this step, it is also possible to add other electrolytes, water repellents and the like to the mixture.

  The electrode is formed on a current collector made of carbon paper or a woven fabric, or on an electrolyte membrane made of a solid polymer or the like. That is, the mixture is formed into a film by printing or applying the mixture on a current collector or an electrolyte film, and then the film-shaped formed product is dried to obtain moisture or an organic solvent contained in the mixture. By removing a part or all of the electrode, the electrode of the present invention having pores inside is formed on the electrolyte membrane or the current collector. In the step of drying the molded product, a strong electrode can be obtained in a short time by heat-treating the molded product. If this heat treatment is carried out in the range of 130 to 400 ° C., a suitable electrode can be obtained without greatly altering the phosphate molecular chain of the electrolyte. Furthermore, it is more desirable to perform the heat treatment under conditions of 150 to 300 ° C.

  The electrode according to the present invention may be formed with a water-repellent structure by mixing PTFE (polytetrafluoroethylene) particles with the electrode-forming paste or by applying PTFE to the current collector. .

  The electrode manufactured in this way is the current collector formed on the electrolyte membrane, and the one formed on the current collector is heat-pressed with the electrolyte membrane, and the electrolyte membrane-electrode junction integrated with the electrolyte membrane and the current collector. Form the body. Like the conventional electrolyte membrane-electrode assembly, this electrolyte membrane-electrode assembly can be incorporated into a fuel cell by constituting a fuel cell by being sandwiched between separators in which gas flow channel grooves are formed. The electrode of the present invention is preferably used for both of the two electrodes bonded to both surfaces of the electrolyte membrane, but may be configured to be used on only one surface. And, in the fuel cell in which the electrode of the present invention is joined to at least one surface of the electrolyte membrane, the utilization efficiency of the catalyst is high. In addition, a sufficient output as a fuel cell can be obtained even with a small amount of catalyst.

  The electrode of the present invention is not limited to conventional polymer electrolyte fuel cells, and can be used for fuel cells that operate at low temperatures. For example, the present inventors have also developed a fuel cell using the above-described proton conducting gel as an electrolyte membrane, and confirmed that a high output can be obtained even if the electrode of the present invention is used for this fuel cell. Yes.

  In the electrode of the present invention using the above-described proton conductive electrolyte composed of phosphate molecular chains, the electrolyte permeates into the aggregate of carbon particles to form a three-phase interface. Then, the catalyst inside the agglomerated waste can be utilized for the electrode reaction. And in a fuel cell using such an electrode, the production cost can be reduced while maintaining the output by reducing the catalyst amount of the electrode. A higher output fuel cell can be realized with the same catalyst amount. Further, since the phosphate molecular chain constituting the electrolyte of the electrode of the present invention does not contain fluorine, there is little environmental load during production and disposal, and platinum contained in the catalyst can be easily recovered.

  In such an electrode, if the average composition ratio of the electrolyte and the conductor is within a range of 20:80 to 80:20 in terms of mass ratio, the electrolyte and the conductor are mixed at an appropriate ratio. A sufficient three-phase interface can be formed inside. Furthermore, if the average composition ratio of the electrolyte and the conductor is within the range of 30:70 to 70:30 by mass ratio, a large amount of three-phase interface is formed in the electrode, and the catalyst utilization rate of the electrode is ensured. Can be improved.

  And in the manufacturing method of the said electrode which produces the mixture of the said proton conductive gel and the conductor which carry | supported the catalyst, and forms an electrode using this mixture, the electrolyte which uses a proton conductive gel as a raw material, and a catalyst Is mixed with the conductor carrying the electrolyte, and the electrolyte can be suitably infiltrated into the aggregate of the conductor, so that many three-phase interfaces can be formed inside the aggregate.

  Here, when the electrode is formed by heat treatment at 130 to 400 ° C. after forming the mixture into a film shape, a strong electrode can be formed in a short time.

It is a schematic diagram which expands and shows the electrode cross section of a conventional structure. It is a schematic diagram which expands and shows the internal structure of the aggregate b of the conventional structure. It is a schematic diagram which expands and shows the internal structure of the aggregate b of this invention. It is sectional drawing which shows the membrane electrode assembly x of a polymer electrolyte fuel cell.

Explanation of symbols

a electrode b aggregate c electrolyte d pore e carbon particle f catalyst g gap x membrane electrode assembly y electrolyte membrane z current collector

  Embodiments of the present invention will be described according to Examples 1 to 3 below.

  First, Example electrodes 1 and 2 that are electrodes of the present invention and Comparative Example electrodes 1 and 2 that are comparative electrodes will be described.

A dry mixed powder of calcium carbonate and orthophosphoric acid is prepared so that orthophosphoric acid has a composition of 48 mol% in terms of P ₂ O ₅ . Then, the dry mixed powder is heat-treated at 1300 ° C. for 0.5 hours in an electric furnace and melted. Thereafter, the melt was poured onto a carbon plate and quenched to room temperature to obtain calcium phosphate glass (melting method). The calcium phosphate glass is pulverized with a mortar until the particle diameter becomes 10 μm or less. And after putting the obtained glass powder in a plastic petri dish, adding an equal weight of distilled water and stirring, leaving it at room temperature for about 3 days with the lid covered to prevent drying, the phosphate molecular chains are formed. Proton conducting gel A was obtained, comprising phosphoric acid in an amount of 48 mol% in terms of P ₂ O ₅ , an electrolyte amount of 52 mol% in terms of calcium ion in terms of CaO, and 50 mass% of water as a dispersion medium.

  Subsequently, 82.7% by mass of ethylene glycol as a dispersion medium was further added to 17.3% by mass of proton conductive gel A, and kneaded to obtain a proton conductive gel dilution B used for electrode formation of the present invention.

  Conductor A used for forming the electrode of the present invention was prepared by supporting carbon particles (Valcan XC-72R manufactured by Cabot) with platinum (Pt) as a catalyst in an amount of 2/3 times the weight of the carbon particles. did.

  A carbon sheet (TGP-H-060F T0.2 mm × W110 mm × L110 mm manufactured by Toray Industries, Inc., 83% porosity) was subjected to water repellent treatment to obtain a current collector for use in this example.

  A paste-like mixture of proton conductive gel dilution B and conductor A used for electrode formation of the present invention is prepared by kneading 2.2 g of proton conductive gel dilution B and 0.45 g of conductor A. And screen-printing the mixture on the current collector surface, followed by heat treatment in the atmosphere at 150 ° C. for 1 hour to remove all of the ethylene glycol and a part of water in the mixture, and the phosphor surface containing Ca ions on the current collector surface Example electrode 1 of the present invention comprising 30% by mass of proton-conductive electrolyte composed of acid salt molecular chain and 70% by mass of conductor A was produced.

  Also, 6.2 g of proton conductive gel dilution B and 0.23 g of conductor A were kneaded to prepare a paste-like mixture of proton conductive gel dilution B and conductor A used for electrode formation of the present invention. In the same manner as in the example electrode 1, the example electrode 2 of the present invention is produced in which the current collector is composed of 70% by mass of a proton-conductive electrolyte composed of phosphate molecular chains containing Ca ions and 30% by mass of the conductor A. did.

  1.2 g of a solution containing 25% solid polymer electrolyte (Nafion) and 0.45 g of the conductor A were mixed and kneaded to prepare a paste-like mixture containing the solid polymer electrolyte and the conductor A. . This mixture was printed on the current collector used in Example electrodes 1 and 2 and then dried to form an electrode. Comparative electrode 1 comprising 40% by mass of solid polymer electrolyte and 60% by mass of conductor A on the current collector surface Was made.

  Further, the mixing ratio of the solution containing the solid polymer electrolyte and the conductor A was changed, and the following is the same production method as in Comparative Example Electrode 1, and the current collector had 70% by mass of the solid polymer electrolyte, the catalyst A comparative example electrode 2 comprising 30% by mass of a conductor carrying bismuth was prepared.

  The Example electrodes 1 and 2 and the comparative electrodes 1 and 2 were each 25 mm × 25 mm in size and used as samples for evaluation tests. Table 1 shows the results of measuring the Pt content of each electrode.

  Hereinafter, Example batteries A to D and Comparative batteries A and B, which are fuel cells of the present invention, produced using the samples for evaluation tests of the above-described Example electrodes 1 and 2 and Comparative example electrodes 1 and 2 will be described. To do.

  The proton conductive gel A was filled in a container made of PTFE (polytetrafluoroethylene) having an inner size of 25 mm × 25 mm and a thickness of 0.8 mm, and then dried to prepare an electrolyte membrane made of the proton conductive gel A.

  The electrode surface of Example electrode 1 was pressed against both surfaces of the electrolyte membrane to produce an electrolyte membrane-electrode assembly. The electrolyte membrane-electrode assembly is sandwiched by a separator having a gas flow path to constitute a fuel cell, and an example battery A which is a fuel cell of the present invention in which the fuel electrode and the oxygen electrode are composed of the example electrode 1 Produced.

  In addition, Example Battery B, which is the fuel cell of the present invention in which the fuel electrode and the oxygen electrode are composed of Example Electrode 2, is produced in the same manner as Example Battery A except that Example Electrode 1 is replaced with Example Electrode 2. did.

Furthermore, 0.1 mg / cm ² of 5% Nafion solution was applied to both surfaces of the solid polymer membrane (Nafion 112), dried at 70 ° C. for 30 minutes, and then both surfaces and the electrode surface of Example electrode 1 were 160. An electrolyte membrane-electrode assembly bonded by hot pressing under the condition of 1 ° C. for 1 minute was produced. Then, in the same manner as in the example battery 1, an example battery C which is a fuel cell of the present invention in which the fuel electrode and the oxygen electrode are composed of the example electrode 1 was produced from this electrolyte membrane-electrode assembly.

  In addition, Example Battery D, which is the fuel cell of the present invention in which the fuel electrode and the oxygen electrode are composed of Example Electrode 2, is produced in the same manner as Example Battery C except that Example Electrode 1 is replaced with Example Electrode 2. did.

  As a comparative example, both surfaces of the solid polymer membrane (Nafion 112) and the electrode surface of the comparative example electrode 1 were combined and hot-pressed at 160 ° C. for 1 minute to prepare an electrolyte membrane-electrode composite. Then, Comparative Example Battery A, which is a comparative fuel cell in which the fuel electrode and the oxygen electrode are composed of Comparative Example Electrode 1, was produced in the same manner as Example Battery A.

  Further, a comparative example battery B which is a comparative fuel cell in which the fuel cell and the oxygen electrode are composed of the comparative example electrode 2 is manufactured in the same manner as the comparative example battery A except that the comparative example electrode 1 is replaced with the comparative example electrode 2. did.

The current-voltage characteristics of the example batteries A to D and the comparative batteries A and B were measured. Table 2 shows the output voltage obtained at a current density of 0.15 A / cm ² .

Measurement conditions are as follows.
Hydrogen: 0.1 MPa (normal pressure)
Oxygen: 0.1 MPa (normal pressure)
Flow rate: 0.201 / min
Gas humidification temperature: 35 ° C
Battery operating temperature: 40 ° C

  As is apparent from Table 2, the example batteries A to D using the electrode of the present invention showed higher output voltages than the comparative batteries A and B. In particular, the difference in output voltage is significant when the example electrode 2 having a low Pt content (catalyst amount) is used. As described above, the fuel cell using the electrode of the present invention shows a higher output than the fuel cell using the conventional electrode, and even if the amount of the catalyst is suppressed, the decrease in the output is small and the output is sufficiently high. You can see that

  Conductor B (PtRu catalyst: carbon particles = 61% by mass: 31% by mass) was prepared by supporting PtRu (Pt: Ru = 64% by mass: 34% by mass) on the same carbon particles as in Example 1 as a catalyst. .

  5.2 g of the proton conducting gel dilution B described in Example 1 and 0.45 g of the conductor B were kneaded to prepare a paste-like mixture of the proton conducting gel dilution B and the conductor B. In the same manner as Example electrodes 1 and 2, Example electrode 3 comprising 50% by mass of proton-conductive electrolyte and 50% by mass of conductor B was produced.

  On the other hand, 1.8 g of a solution containing 25% solid polymer electrolyte (Nafion) and 0.45 g of the conductor B were kneaded to prepare a paste-like mixture containing the solid polymer electrolyte and the conductor B. A comparative example electrode 3 comprising 50% by mass of a solid polymer electrolyte and 50% by mass of a conductor B was produced in the same manner as this comparative example electrodes 1 and 2.

  The Example electrode 3 and the comparative example electrode 3 were used as evaluation test samples each having a size of 25 mm × 25 mm, as in Example 1. Table 3 shows the results of measuring the Pt content of each electrode.

Next, 0.1 mg / cm ² of a 5% by mass Nafion solution was applied to both surfaces of the solid polymer electrolyte membrane (Nafion 117) and dried at 70 ° C. for 30 minutes. An electrolyte membrane-electrode assembly in which the opposite surface and the electrode 3 were joined by hot pressing at 160 ° C. for 1 minute each was prepared, and in the same manner as in Example 1, the fuel electrode and the oxygen electrode were respectively Example battery E, which is a fuel cell of the present invention comprising Example electrode 3 and Example electrode 1, was produced.

  Also, an electrolyte membrane in which one side of the solid polymer electrolyte (Nafion) membrane and the comparative example electrode 3 are joined by hot pressing the opposite side and the comparative example electrode 1 at 160 ° C. for 1 minute, respectively. -An electrode assembly was prepared, and in the same manner as in Example 1, a comparative battery C, which was a comparative fuel cell in which the fuel electrode and the oxygen electrode were composed of the comparative electrode 3 and the comparative electrode 1, respectively, was manufactured.

For Example Battery E and Comparative Example Battery C, methanol (CH ₃ OH) was supplied to the fuel electrode side and O ₂ was supplied to the oxygen electrode side, and current-voltage characteristics were measured. Table 4 shows current values obtained at an output voltage of 0.55V.

The measurement conditions are as follows.
Fuel electrode: 50% by mass CH ₃ OH + 50% by mass H ₂ O
: 0.10 l / min
Oxygen electrode: O ₂
: 0.2 MPa
: 0.35 l / min
Gas humidification temperature: Non-humidified battery operating temperature: 30 ° C

  As is apparent from Table 4, the example battery E using the electrode of the present invention shows higher output than the comparative example battery D using the electrode of the conventional configuration. Since the amount of catalyst used in the example battery E and the comparative example battery D is substantially the same, it can be seen that the example battery E has a higher catalyst utilization efficiency than the comparative example battery D. Thus, the electrode of the present invention is effective even when methanol is supplied as fuel to the fuel electrode side.

  Example battery A, Example battery C and Comparative example battery A produced in Example 1 were disassembled, and each electrolyte membrane-electrode assembly was taken out, and concentrated acid (aqua regia) with 3 volumes of concentrated hydrochloric acid and 1 volume of concentrated nitric acid. ) And heated at 60 to 70 ° C. for 2 hours, and then Pt was recovered from aqua regia.

  For Example Battery A and Example Battery C, the electrolyte membrane-electrode assembly was decomposed. As a result of measuring the recovered Pt, the recovery rate {(recovered Pt amount) / (Pt amount used for the electrode) × 100} was 89% and 72%, respectively.

  On the other hand, in Comparative Example Battery A, the electrolyte membrane-electrode assembly was not decomposed even in the above-described aqua regia treatment, and the recovery rate of Pt from aqua regia was less than 1%.

  From the above results, it can be seen that Pt can be easily recovered from the electrode of the present invention used in the fuel cell without burning the electrolyte membrane-electrode assembly.

Claims (6)

An electrode used in a fuel cell,
A linear structure comprising at least one of Ca ion, Mg ion and Zn ion, and a phosphate glass obtained by a melting method reacts with water to form an OH group bonded to a phosphorus atom or / and cyclic A proton conducting electrolyte comprising a proton conducting gel having a dispersed phase comprising a phosphate molecular chain having a structure and a dispersion medium comprising water present around each OH group of the phosphate molecular chain; and a catalyst. An electrode having a supported conductor. The electrode according to claim 1, wherein an average composition ratio of the electrolyte and the conductor is in a range of 20:80 to 80:20 by mass ratio. The electrode according to claim 1, wherein an average composition ratio of the electrolyte and the conductor is in a range of 30:70 to 70:30 by mass ratio. A fuel cell comprising the electrode according to any one of claims 1 to 3 joined to at least one surface of an electrolyte membrane. A linear structure comprising at least one of Ca ion, Mg ion and Zn ion, and a phosphate glass obtained by a melting method reacts with water to form an OH group bonded to a phosphorus atom or / and cyclic A mixture of a proton conducting gel having a dispersed phase composed of a phosphate molecular chain having a structure, a dispersion medium composed of water present around each OH group of the phosphate molecular chain, and a conductor carrying a catalyst The electrode manufacturing method according to any one of claims 1 to 3, wherein the electrode is formed using the mixture. Producing a mixture of a proton conducting gel having a dispersed phase composed of a phosphate molecular chain containing at least one of Ca ions, Mg ions and Zn ions and a dispersion medium composed of water, and a conductor carrying a catalyst, The electrode manufacturing method according to claim 1, wherein the electrode is formed by heat-treating the mixture at a temperature of 130 to 400 ° C. after forming the mixture into a film.

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