JP2008108495A - Manufacturing method for fuel-cell catalyst carrier, membrane electrode assembly for fuel cell, fuel cell, and processor for fuel-cell catalyst carrier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a fuel-cell catalyst carrier that improves the durability of a catalyst carrier while being advantageous for suppressing deterioration in the power generation performance of a fuel cell, a membrane electrode assembly for a fuel cell, the fuel cell, and a processor for the fuel-cell catalyst carrier. <P>SOLUTION: The manufacturing method is composed so as to execute a first step in which a catalyst carrier for carrying a catalyst used for a fuel cell is prepared, and a second step for applying a voltage to the catalyst carrier in an atmosphere including oxygen so as to locally oxidize the catalyst carrier. The membrane electrode assembly is provided with an ion conduction film and an anode electrode and a cathode electrode that sandwich the ion conduction film between them in a thickness direction. In the membrane electrode assembly, at least one of the anode electrode and the cathode electrode is provided with a fluid diffusion layer for allowing an active material to permeate through it and a catalyst layer formed on the surface of the fluid diffusion layer. The catalyst layer is formed while allowing the catalyst carrier to carry a catalyst. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a fuel cell catalyst carrier, a fuel cell membrane electrode assembly, a fuel cell, and a fuel cell catalyst carrier treatment apparatus.

  In Patent Document 1, two or more kinds of carbon powders graphitized at different heat treatment temperatures are mixed to form a carbon support, and platinum and base metal are supported on the carbon support to form platinum-supported carbon. A technique for forming a fuel cell catalyst layer using platinum-supported carbon is disclosed.

Patent Document 2 discloses a catalyst membrane for a polymer electrolyte fuel cell having graphite, catalyst particles, and an ion conductive resin. According to this, it is described that the use of graphite optimizes the arrangement of the catalyst and the ion conductive resin in the catalyst membrane. Patent Document 3 discloses a cathode catalyst including a mixture of 30 to 40% by mass of platinum black and a catalyst supported on 60 to 70% by mass.
JP 2002-273224 A JP 2005-209544 A JP 2005-294264 A

  In the industry, there is a demand for further improvement in the durability of the power generation performance of fuel cells. However, since the electrode potentials of the anode electrode and the cathode electrode change due to various factors such as continuous operation, starting and stopping of the fuel cell for a long time, the catalyst carrier may be corroded depending on conditions. In this case, since the electrode performance changes, there is a limit to improving the durability of the power generation performance of the fuel cell.

  For example, when the catalyst support is carbon-based, in the case of the cathode electrode, when the cathode electrode is in a noble potential environment (about 1.0 V or more), the electrochemical oxidation reaction of carbon causes Corrosion may progress. In this case, the catalyst metal particles supported on the catalyst carrier formed of carbon are released, and as a result, the catalyst metal particles that are effectively used may be reduced. In this case, the power generation performance of the fuel cell may be reduced. In addition, if fuel shortage occurs during power generation operation at the anode electrode, water electrolysis or oxidation of the catalyst carrier may occur in place of the fuel oxidation reaction at the anode electrode to maintain current density. is there. In this case, the performance of the anode electrode changes, which may affect the power generation performance of the fuel cell.

  In Patent Documents 1 and 2, carbon constituting the catalyst carrier is heat-treated at a high temperature to graphitize the carbon, thereby enhancing the corrosion resistance of the carbon. Furthermore, Patent Document 3 adopts a method of balancing the overall corrosion resistance by blending platinum-supporting carbon and platinum black. However, even with the above-described technique, there is a limit in suppressing the corrosion of the catalyst carrier mainly composed of carbon.

  The present invention has been made in view of the above circumstances, and can produce a catalyst support for a fuel cell that can improve the durability of the catalyst support for a fuel cell and is advantageous in suppressing a decrease in power generation performance of the fuel cell. It is an object of the present invention to provide a method, a fuel cell membrane electrode assembly, a fuel cell, and a fuel cell catalyst carrier treatment apparatus.

  A method for manufacturing a fuel cell catalyst carrier according to aspect 1 includes a first step of preparing a fuel cell catalyst carrier, and applying a voltage to the catalyst carrier in a state where the catalyst carrier is placed in an atmosphere containing an oxidant. And a second step of electrochemically oxidizing the support.

  In the method for producing a fuel cell catalyst carrier according to aspect 2, the third step of carrying the catalyst on the catalyst carrier is performed after the second step. In this case, since the catalyst is supported on the catalyst carrier after the second step, the second step can be prevented from affecting the catalyst.

  A fuel cell catalyst carrier according to aspect 3 is a fuel cell membrane electrode assembly comprising an ion conductive membrane and an anode electrode and a cathode electrode sandwiching the ion conductive membrane in the thickness direction. At least one of the electrodes includes a fluid diffusion layer that transmits the active material and a catalyst layer provided on the surface of the fluid diffusion layer so as to face the ion conductive membrane. And a catalyst supported on the catalyst carrier.

  A fuel cell according to aspect 4 includes a fuel cell membrane electrode assembly having an ion conductive membrane and an anode electrode and a cathode electrode sandwiching the ion conductive membrane in the thickness direction, and an anode electrode of the fuel cell membrane electrode assembly An anode distribution member for supplying anode fluid to the anode electrode, and a cathode distribution member for supplying cathode fluid to the cathode electrode of the fuel cell membrane electrode assembly; The fuel cell membrane electrode assembly is formed of the fuel cell membrane electrode assembly according to the above aspect.

  According to the above aspects 1 to 4, in the second step, the portion of the catalyst carrier that is easily oxidized is electrochemically oxidized before the fuel cell is assembled and is electrochemically oxidized. Leave difficult parts. Therefore, when the catalyst carrier that has undergone the second step is assembled to the fuel cell, the portion of the catalyst carrier that is susceptible to electrochemical oxidation is previously oxidized and removed. Therefore, the remaining part of the catalyst carrier corresponds to a part that is not easily oxidized electrochemically. As a result, even if the fuel cell having the catalyst carrier in which the second step is performed is operated for power generation for a long time, the electrochemical oxidation of the catalyst carrier incorporated in the fuel cell is suppressed. As a result, the durability of the fuel cell can be improved, and a decrease in output voltage can be suppressed.

Oxidizing agent refers to a substance that oxidizes a partner by taking electrons from the partner. Examples of the atmosphere containing an oxidizing agent include an atmosphere containing an oxygen atom, an oxygen gas-containing atmosphere (air or the like), or an atmosphere containing liquid phase or vapor phase water (water vapor). Therefore, the form which implements a 2nd process in the state which contacted the catalyst support and water vapor is illustrated. Here, regarding carbon, when H ₂ O is an oxidizing agent, it is considered that a reaction in which oxygen dioxide is formed from carbon proceeds as in the following formula (1). Here, the redox potential (equilibrium electrode potential) of carbon is +0.2 volts (vs. SHE). Here, SHE means a hydrogen standard electrode. If the potential applied to the catalyst carrier is more positive than the equilibrium electrode potential (vs. SHE), the reaction proceeds in the oxidation direction, and the oxidation of carbon is promoted.
Formula (1): C + 2H ₂ O → CO ₂ + 4H ⁺ + 4e ⁻ +0.2 volts (vs. SHE)

  In carrying out the second step, the catalyst carrier is preferably a catalyst carrier before carrying a catalyst such as platinum. In this case, when a voltage is applied to the catalyst carrier, it is avoided that the catalyst such as platinum is affected. In the second step, a reference electrode and an ion conductive membrane are prepared, and the potential of the catalyst carrier with respect to the reference electrode is controlled by the potential control means in a state where the ion conductive membrane is sandwiched between the aggregate of catalyst carriers and the reference electrode, Examples include a mode in which a portion that is easily oxidized electrochemically in the carrier is oxidized and a portion that is not easily oxidized electrochemically is left.

The fuel cell catalyst carrier processing apparatus according to aspect 5 is an apparatus that can carry out the fuel cell catalyst carrier manufacturing method according to the aspect described above, in which the ion conductive membrane is sandwiched between the catalyst carrier assembly and the reference electrode. In the state, a holding means for holding the aggregate of the catalyst carrier, the reference electrode and the ion conductive membrane, a reference electrode terminal electrically connected to the reference electrode, and a working electrode electrically connected to the aggregate of the catalyst carrier A potential control means having a terminal, and the potential of the catalyst carrier assembly with respect to the reference electrode is controlled by the potential control means in a state where the oxidant is in contact with the catalyst carrier assembly. Among them, the portion that is easily oxidized electrochemically is oxidized, and the portion that is not easily oxidized electrochemically is left. In this case, the portion of the catalyst carrier that is likely to be oxidized electrochemically is oxidized in advance, so that oxidation during the power generation operation of the fuel cell is suppressed. Examples of the oxidizing agent include water (H ₂ O), oxygen gas, and oxygen in the air. Water includes water vapor and liquid phase water.

  The portion of the catalyst carrier that is easily oxidized is oxidized and disappears before assembly of the fuel cell. For this reason, oxidation during the power generation operation of the fuel cell is suppressed. Therefore, it is possible to improve the durability of the catalyst carrier for the fuel cell, which is advantageous for suppressing a decrease in the power generation performance of the fuel cell.

  According to the present invention, the first step of preparing a catalyst carrier and the second step of applying a voltage to the catalyst carrier in an atmosphere containing an oxidizing agent to oxidize the catalyst carrier are performed. Examples of the atmosphere containing the oxidizing agent include an atmosphere containing oxygen gas such as air, or an atmosphere containing liquid or vapor phase water. Examples of the catalyst carrier include carbon-based materials, and a carbon carrier is preferable. Examples of the carbon carrier include carbon black, carbon nanotube (including carbon nanohorn), carbon nanowall, fibrous carbon, activated carbon, diamond-like carbon, and the like. Examples of carbon black include furnace black and acetylene black. A noble metal is mentioned as a catalyst, At least 1 type in any one of platinum, rhodium, palladium, osmium, and ruthenium is mentioned.

  Preferably, in the second step, a reference electrode (also referred to as a reference electrode) and an ion conductive membrane (proton conductive membrane) are prepared. An ion conducting membrane (proton conducting membrane) is sandwiched between the catalyst carrier assembly and the reference electrode. In this state, it is preferable to supply a carrier gas containing an oxidizing agent to the catalyst carrier aggregate while supplying hydrogen gas to the reference electrode. The carrier gas is preferably an inert gas, and examples thereof include nitrogen gas and argon gas. The reason why hydrogen gas is supplied to the reference electrode is to set the potential of the reference electrode to 0 volts or near 0 volts (vs. SHE). Then, the potential on the catalyst carrier side with respect to the reference electrode is controlled. In this case, the potential may be controlled cyclically or may be controlled by a constant potential (direct current). The catalyst carrier before the second step is preferably before supporting the catalyst. Therefore, it is preferable to support the catalyst on the catalyst carrier after the second step is executed. This suppresses the second step from affecting the catalyst on the catalyst carrier.

  In the second step, when the potential of the catalyst carrier assembly is cyclically controlled, the cycle of repeating both the oxidation condition and the reduction condition is set as one cycle for the potential of the catalyst carrier assembly with respect to the reference electrode. This cycle can be repeated many times. As a result, a portion of the catalyst carrier that is easily oxidized electrochemically is oxidized in advance, and a portion that is not easily oxidized is left. The number of cycles can be appropriately selected. For example, it can be about 5 to 10,000 times or about 10 to 1000 times, but is not limited thereto. In the second step, the reason for repeating both the oxidation condition and the reduction condition is that, in an actual fuel cell, there are potential fluctuations due to starting and stopping, and the oxidizable part in such an environment is reliably removed. Because we expect that.

  Here, when the potential of the aggregate of catalyst supports is cyclically controlled with respect to the reference electrode, the potential is increased or decreased so as to straddle the oxidation-reduction potential (equilibrium electrode potential) of the material forming the catalyst support. Cycle can be made one cycle. That is, a cycle having a potential region less than the oxidation-reduction potential of the material forming the catalyst carrier and a potential region exceeding the oxidation-reduction potential on the plus side can be made into one cycle.

  Here, when the catalyst carrier is carbon-based, for example, the cycle controlled to 0.1 volts ← → 1.0 volts (vs. SHE) can be made one cycle. When the potential of the catalyst support is cyclic, when the catalyst support is cyclic, the reason for setting the upper limit of the potential to a potential of 1.0 volts is that if the potential is higher than that, the oxidation of the catalyst support is excessively promoted. This is because there is a possibility that The reason why the lower limit of the cycle potential is set to a potential of 0.1 volts is that a potential lower than that is considered to be insufficient for the oxidation of the catalyst carrier. Further, the cycle controlled to 0.1 volts ← → 0.8 volts (vs. SHE) can be made one cycle. The redox potential of carbon is +0.2 volts (vs. SHE).

  When the catalyst support is carbon-based, and the aggregate of the catalyst support is controlled at a constant potential (direct current), the potential (constant potential) of the aggregate of the catalyst support with respect to the reference electrode is 0.2 volts to It is desirable to be within the range of 0.5 volts (vs. SHE). In this case, if it exceeds 0.5 volts, the oxidation of the catalyst support may be promoted excessively. Moreover, it is thought that it is not enough for the oxidation of a catalyst support | carrier to be less than 0.2 volts. When the potential of the catalyst carrier aggregate is controlled at a constant potential (direct current), the potential of the catalyst carrier aggregate with respect to the reference electrode (constant potential) is 0.2 to 0.4 volts (in some cases). vs. SHE).

  When the potential is cyclically controlled when the second step is performed on the catalyst carrier already supporting the catalyst metal, the upper limit potential of the potential is such that the oxidation-reduction potential of the catalyst metal is on the plus side. It is preferable not to exceed. This is because it is preferable not to promote oxidation of the catalyst metal.

For example, when the second step is performed on a catalyst carrier already supporting platinum as a catalyst metal, the upper limit potential of the cycle voltage is determined by considering the following equation (2), the oxidation-reduction potential of platinum (+1.188). It is preferable not to exceed the bolt (vs. SHE). Therefore, it is desirable that the upper limit potential of the cycle voltage does not exceed 1.0 volts.
Formula (2): Pt ²⁺ +2 ^e− = Pt +1.188 volts (vs. SHE)

  Any potential control means can be used as long as it can control the potential on the catalyst carrier side with respect to the reference electrode. Examples of the potential control means include a potentiostat that is electrically connected to the catalyst carrier side and the reference electrode.

  According to the present invention, the catalyst carrier is previously removed from the portion that is easily oxidized electrochemically. If the catalyst is supported on such a catalyst carrier and used as a catalyst carrier for a fuel cell, the oxidation deterioration of the catalyst carrier is suppressed in the power generation operation of the fuel cell, and the decrease in the surface area due to the oxidation deterioration is suppressed. , Aggregation of catalyst particles is suppressed.

  Examples of the present invention will be specifically described below. First, the holding device 10 (holding means) having the storage tank 12 shown in FIG. 1 is used. The holding device 10 includes a flow distribution member 14. The flow distribution member 14 includes a hydrogen gas supply unit 10 a that supplies hydrogen gas to the hydrogen electrode 16 and a hydrogen gas discharge unit 10 c that discharges hydrogen gas from the hydrogen electrode 16. An aggregate 2 (mass 10 g) of carbon particles formed of carbon black (Ketjen carbon black) functioning as a catalyst carrier is filled in the storage tank 12 of the apparatus 10 to form a carbon electrode 20. Furthermore, the apparatus 10 includes an inert gas supply unit 20a that supplies nitrogen gas (inert gas) to the carbon electrode 20, and an inert gas discharge unit 20c that discharges nitrogen gas (inert gas) from the carbon electrode 20. .

The hydrogen electrode 16 described above was manufactured as shown in FIGS. That is, a commercially available carbon paper 3 (Toray Industries, Inc., TGP-H-60, thickness 190 μm) was prepared as a carbon substrate having porosity and conductivity. This carbon paper 3 was impregnated with carbon paste 4. This carbon paste 4 is a dispersion (polyflon D) containing 100 g of carbon black (VXC-72R, surface area 380 m ² / g, manufactured by Cabot Corporation) as a conductive material and polytetrafluoroethylene (PTFE) as a water repellent. -1, Daikin Co., Ltd.) 166.7 g, a dispersant, and a mixture obtained by kneading pure water.

  As described above, the carbon paper 3 was impregnated with the carbon paste 4, and then the carbon paper 3 was pre-dried at 80 ° C. for 1 hour and then baked at 380 ° C. for 1 hour. This was used as the gas diffusion layer 160 (see FIG. 1B). The gas diffusion layer 160 has surfaces 160a and 160c.

Next, formation of the catalyst paste will be described. As a catalyst, 10 g of platinum-supported carbon (Tanaka Kikinzoku Co., Ltd., TEC10E50E, 50% by mass of platinum) supporting platinum and 100 g of ion exchange resin solution (Asahi Kasei Corporation, SS-1100 / 05, ion exchange resin: 5% by mass) And 40 g of ion-exchanged water were kneaded and dispersed in a sand mill for 1 hour to form a catalyst paste. The kneading conditions by the sand mill were a ceramic ball (zirconia) diameter of 2 mm and a peripheral speed of 15 m / s. In this case, the mass ratio of ion exchange resin / platinum-supported carbon was set to 1.0. The catalyst paste obtained as described above was applied to the surface 160a of the gas diffusion layer 160 with a gap of 100 μm by the doctor blade method (about 0.4 mg Pt / cm ² ) to form the catalyst layer 162, and the hydrogen electrode 16 was formed (see FIG. 2C). The catalyst layer 162 is in contact with the ion conductive membrane 5 of the fuel cell.

  Then, the hydrogen electrode 16 was covered with a flow distribution member 14 (material: carbon) having a passage groove-shaped channel 140. In this case, the ion conductive film 5 (perfluorosulfonic acid film, thickness: 30 μm) was sandwiched between the hydrogen electrode 16 and the carbon electrode 20. A potentiostat 6 (Hokuto Denko: potentio / galvanostat, HA-301) as potential control means is used, and the reference electrode terminal 6a and the hydrogen electrode 16 (reference electrode) of the potentiostat 6 are connected via the flow distribution member 14. The working electrode terminal 6c of the potentiostat 6 and the carbon electrode 20 side were electrically connected to each other. The potentiostat 6 has both a potentiostat function for controlling to a constant potential and a galvanostat function for controlling to a constant current.

  Then, hydrogen gas (flow rate: 1 liter / minute) is supplied from the hydrogen gas supply unit 10a to the hydrogen electrode 16 (reference electrode), and nitrogen gas (flow rate: 1 liter / minute) is not used as a carrier gas containing water vapor. The potential of the working electrode terminal 6c with respect to the reference electrode terminal 6a of the potentiostat 6 was controlled by the potentiostat 6 while being supplied to the carbon electrode 20 from the active gas supply unit 20a. That is, the potential of the carbon electrode 20 with respect to the hydrogen electrode 16 (reference electrode) was controlled. In this case, as a method for introducing water vapor, a gas passed through a bubbler having the same temperature as the temperature of the holding device 10 (room temperature 25 ° C.) was used (RH 100%). As a result, the second step was performed on the carbon electrode 20. Here, the hydrogen electrode 16 to which hydrogen gas is supplied is set to 0 volts, and serves as a reference electrode (also referred to as a reference electrode).

  According to the second step, the potential of the carbon electrode 20 with respect to the hydrogen electrode 16 (reference electrode) was set to one cycle of 0.1 to 1.0 volts, and 100 cycles were performed (sweep speed: 50 millivolts / second). . The carbon redox potential (0.2 volts) in the above-described formula (1) for carbon is defined as a threshold voltage, and a voltage less than the threshold voltage and a voltage exceeding the threshold voltage are alternately repeated a plurality of times. . That is, the potential operation of the carbon electrode 20 is repeated a plurality of times so as to cross the threshold voltage. Thereby, the part (for example, edge part, part with low crystallinity degree) which is easy to oxidize electrochemically among the carbon particles which comprise the carbon electrode 20 is oxidized beforehand. The electrochemically oxidized portion becomes carbon dioxide and is discharged to the outside together with the carrier gas. Of the carbon part of the carbon particles, the part that is not easily oxidized electrochemically remains. Thus, after implementing a 2nd process, the carbon particle which comprises the carbon electrode 20 is removed from the storage tank 12. FIG.

  As described above, 10 g of the carbon particles subjected to the second step and 59 g of a dinitrodiammine platinum nitric acid solution (catalyst-containing solution, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., Pt 8.476% by mass) were mixed to form a mixed solution. Thereafter, the mixed solution was dried at 70 ° C. for 24 hours. Thereafter, reduction was performed at 190 ° C. for 2 hours in a hydrogen atmosphere, whereby platinum was supported on carbon particles to form platinum-supported carbon (Pt: 50 mass%).

Next, a membrane electrode assembly was formed. In this case, as shown in FIG. 3A, a commercially available carbon paper 7 (Toray Industries, Inc., TGP-H-60, thickness 190 μm) was prepared as a carbon base material having porosity and conductivity. This carbon paper 7 was impregnated with carbon paste 8. The carbon paste 8 is a dispersion (polyfluorocarbon) containing 100 g of carbon black (VXC-72R, surface area 380 m ² / g, manufactured by Cabot Corporation) as a conductive material and polytetrafluoroethylene (PTFE) as a water repellent. D-1, Daikin Co., Ltd.) 166.7 g, a dispersant and pure water were kneaded. Thereafter, the carbon paper 7 impregnated with the carbon paste 8 was pre-dried at 80 ° C. for 1 hour, and then fired at 380 ° C. for 1 hour. This was used as the gas diffusion layer 70 (see FIG. 3B).

  Next, a fuel cell electrode was formed. In this case, platinum-supported carbon in which platinum was supported on the carbon support on which the second step was performed was used as a catalyst. And 10g of platinum carrying | support carbon which implemented the 2nd process, 100g of ion exchange resin solutions (Asahi Kasei Corporation, SS-1100 / 05, ion exchange resin: 5 mass%) containing ion exchange resin, 40g of ion exchange water, Was kneaded for 1 hour in a sand mill and dispersed to form a catalyst paste. In this case, the mass ratio of ion exchange resin / platinum-supported carbon was set to 1.0. The ion exchange resin functions as a proton conducting material.

The obtained catalyst paste was applied to one surface of the gas diffusion layer 70 by a doctor blade method with a gap of 250 μm (about 1 mg Pt / cm ² ) to form a cathode electrode sheet. The above catalyst paste was applied to one surface of another gas diffusion layer 70 by a doctor blade method with a gap of 100 μm (about 0.4 mg Pt / cm ² ) to form an anode electrode sheet.

The cathode electrode sheet was punched into a reaction area of 100 cm ² to form a cathode electrode 7C (see FIG. 3C). As shown in FIG. 3C, the cathode electrode 7 </ b> C is formed of a gas diffusion layer 70 (fluid diffusion layer) and a cathode catalyst layer 70 c laminated on the gas diffusion layer 70. The anode electrode sheet was punched into a reaction area of 100 cm ² to form an anode electrode 7A (see FIG. 3D). As shown in FIG. 3D, the anode electrode 7 </ b> A is formed of a gas diffusion layer 70 (fluid diffusion layer) and an anode catalyst layer 70 a stacked on the gas diffusion layer 70. The catalyst layers 70a and 70c contain a catalyst (platinum), carbon black (conductive material) as a catalyst carrier, and a proton conductive material.

  Thereafter, the cathode electrode 7C was arranged on one surface 80c side of the ion conductive film 80 (Gore 30-III-B: Japan Gore-Tex Co., Ltd.) cut into a 12 cm square shape. An anode electrode 7A is disposed on the other surface 80a side of the ion conductive film 80. In this case, the catalyst layer 70a and the catalyst layer 70c face and contact the ion conductive film 80 so as to sandwich the ion conductive film 80. In this state, hot pressing was performed at 140 ° C. and 8 MPa for 3 minutes to form a membrane electrode assembly 8 (see FIG. 4).

Then, as shown in FIG. 4, a cathode flow distribution member 85 also called a separator having a gas flow path 85c for flowing the anode gas is applied to the cathode electrode 7C of the membrane electrode assembly 8, and the gas flow for flowing the cathode gas. An anode distribution member 86, also called a separator having a path 86c, was applied to the anode electrode 7A to form a test cell. And power generation performance was evaluated using the test cell. In this case, the anode gas (hydrogen gas) is allowed to flow through the gas flow path 85c, and the cathode gas (air) is allowed to flow through the gas flow path 86c. In this case, the cell temperature is 80 ° C., the dew point of the anode electrode 7A and the cathode electrode 7C is 80 ° C., the current density is 0.2 amps / cm ² , the hydrogen utilization rate is 70%, and the air utilization rate is 30%. It was evaluated with.

  Based on the manufacturing conditions described above, a test cell according to a comparative example in which the method of the present invention was not implemented was produced, and the power generation performance of the test cell was evaluated under the same power generation conditions. However, in the comparative example, the second step is not performed on the carbon particles.

  FIG. 5 shows the test results. The horizontal axis of FIG. 5 indicates time, and the vertical axis indicates the voltage holding ratio when the initial voltage is 100%. In FIG. 5, the characteristic line S1 shows the test result relating to the test cell of the example in which the method of the present invention is implemented. Characteristic line S2 shows the test result concerning the test cell of the comparative example in which the method of the present invention is not carried out. As shown by the characteristic line S1, according to the embodiment, the power generation time is maintained in a state where the voltage holding ratio is high even for a long period of time. On the other hand, as shown by the characteristic line S2, according to the comparative example, when the power generation time has elapsed, the voltage holding ratio gradually decreases. Therefore, the durability of the fuel cell can be maintained for a long time by electrochemically pre-oxidizing the part of the carbon particles that make up the catalyst carrier that is susceptible to electrochemical oxidation prior to assembly as a fuel cell. You can see that That is, in this embodiment, since the method of the present invention is carried out, a portion of the catalyst carrier that is easily oxidized is oxidized beforehand and disappears before assembly of the fuel cell. For this reason, it is suppressed that the part which is easily oxidized among catalyst carriers is oxidized during the power generation operation of the fuel cell. Therefore, it is possible to improve the durability of the catalyst carrier for the fuel cell, which is advantageous for suppressing a decrease in the power generation performance of the fuel cell.

  In the comparative example, as shown in FIG. 6, a portion of the catalyst carrier formed of carbon that is easily oxidized is easily oxidized and deteriorated during the power generation operation of the fuel cell, and disappears (hollows). For this reason, it is presumed that the contact points between the catalyst carriers formed of carbon are reduced and the electrical resistance is increased.

  In this case, when the catalyst support formed of carbon is oxidized and deteriorated, the catalyst metal particles supported on the catalyst support may be released, and the catalyst metal particles used effectively may be reduced. Further, the disappearance of carbon may cause aggregation of the liberated catalyst (platinum). In this case, the power generation performance of the fuel cell may be reduced.

  A measure for bringing the acidic solution into contact with the catalyst carrier is also conceivable. In this case, however, the portion of the catalyst carrier that is susceptible to chemical degradation is removed, and the portion of the catalyst carrier that is susceptible to electrochemical oxidation is not oxidized. This measure is difficult to match the deterioration of the catalyst carrier in a fuel cell with an electrochemical power generation reaction.

The present invention is not limited to the above-described embodiments, and can be implemented with appropriate modifications within a range not departing from the gist. The following technical idea can also be grasped from the above description.
(Additional Item 1) First step of preparing a catalyst support for a fuel cell, and in a state where the catalyst support is installed in an atmosphere containing an oxidant, the catalyst support is electrochemically oxidized to A method for producing a catalyst support for a fuel cell, comprising performing a second step of previously oxidizing a portion that is easily oxidized chemically.

  The present invention can be used, for example, for vehicles, stationary devices, electric devices, electronic devices, and portable fuel cells.

It is a conceptual diagram of the processing apparatus which implements a 2nd process. It is a block diagram which shows typically the process of forming a hydrogen electrode. It is a block diagram which shows typically the process of forming the electrode for cathodes, and the electrode for anodes. It is a block diagram which shows typically the state by which the fuel cell was decomposed | disassembled. It is the graph which performed the electric power generation operation which concerns on an Example and a comparative example. It is a figure concerning a comparative example and showing typically the state where the contact of catalyst carriers formed with carbon is decreasing.

Explanation of symbols

10 is a holding device, 14 is a distribution member, 16 is a hydrogen electrode, 20 is a carbon electrode,
7A is an anode electrode, 70 is a gas diffusion layer, 70a is an anode catalyst layer, 7C is a cathode electrode, 70 is a gas diffusion layer, 70c is a cathode catalyst layer, 80 is an ion conductive membrane, and 8 is a membrane electrode The joined body is shown.

Claims (7)

A first step of preparing a fuel cell catalyst carrier;
And a second step of applying a voltage to the catalyst carrier and electrochemically oxidizing the catalyst carrier in a state where the catalyst carrier is installed in an atmosphere containing an oxidant. A method for producing a carrier.   2. The method for producing a catalyst support for a fuel cell according to claim 1, wherein the catalyst support is carbon-based, and the atmosphere containing the oxidizing agent is an atmosphere containing liquid or vapor phase water, or an oxygen gas-containing atmosphere.   2. The method for producing a fuel cell catalyst carrier according to claim 1, wherein after the second step, a third step of carrying a catalyst on the catalyst carrier is performed. In one of Claims 1-3, a reference electrode and an ion conductive film are prepared in the second step,
The potential of the catalyst carrier with respect to the reference electrode is controlled by potential control means in a state where the ion conductive membrane is sandwiched between the assembly of the catalyst carrier and the reference electrode, and the catalyst carrier is electrochemically oxidized. A method for producing a catalyst support for a fuel cell, wherein an easy-to-oxidize portion is electrochemically oxidized and a portion that is not easily oxidized electrochemically remains. In a fuel cell membrane electrode assembly comprising an ion conductive membrane, and an anode electrode and a cathode electrode sandwiching the ion conductive membrane in the thickness direction,
Each of the anode electrode and the cathode electrode includes a fluid diffusion layer that allows an active material to permeate, and a catalyst layer provided on a surface of the fluid diffusion layer so as to face the ion conductive membrane,
The catalyst layer of at least one of the anode electrode and the cathode electrode includes a catalyst carrier according to one of claims 1 to 4 and a catalyst supported on the catalyst carrier. A fuel cell membrane electrode assembly. A fuel cell membrane electrode assembly having an ion conductive membrane and an anode electrode and a cathode electrode sandwiching the ion conductive membrane in the thickness direction;
An anode flow distribution member provided on the anode electrode side of the fuel cell membrane electrode assembly and supplying an anode fluid to the anode electrode;
A fuel cell comprising a cathode flow distribution member provided on the cathode electrode side of the fuel cell membrane electrode assembly and supplying a cathode fluid to the cathode electrode;
The fuel cell membrane electrode assembly is formed of the fuel cell membrane electrode assembly according to claim 5. Holding means for holding the aggregate of the catalyst carrier, the reference electrode, and the ion conductive membrane in a state where the ion conductive membrane is sandwiched between the aggregate of the catalyst carrier and the reference electrode;
A potential control means comprising a reference electrode terminal electrically connected to the reference electrode and a working electrode terminal electrically connected to the assembly of the catalyst carriers;
In a state where the catalyst carrier aggregate is installed in an atmosphere containing an oxidant, the potential of the catalyst carrier aggregate with respect to the reference electrode is controlled by potential control means, and the catalyst carrier is easily oxidized electrochemically. An apparatus for treating a catalyst support for a fuel cell, wherein the portion is electrochemically oxidized and the portion that is not easily oxidized electrochemically remains.

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