JP2005294175A - Electrode catalyst layer and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means for improving durability of a polymer electrolyte fuel cell.
As an electrode catalyst layer of a polymer electrolyte fuel cell, a layer made of a conductive catalyst carrier, a catalyst active material supported on the conductive catalyst carrier, a proton conductive polymer, and a water repellent material is used. .
[Selection] Figure 1

Description

  The present invention relates to a polymer electrolyte fuel cell. More specifically, the present invention relates to an electrode catalyst layer in a polymer electrolyte fuel cell.

  A fuel cell is a clean power generation system in which the product of an electrode reaction is water in principle and has almost no adverse effect on the global environment. Various fuel cells such as a polymer electrolyte fuel cell, a solid oxide fuel cell, a molten carbonate fuel cell, and a phosphoric acid fuel cell have been proposed as fuel cells. Among these, a polymer electrolyte fuel cell (PEFC) can be operated at a relatively low temperature, and thus is expected as a power source for moving bodies such as automobiles, and is being developed.

  The solid polymer fuel cell has a proton conductive solid polymer electrolyte membrane and a pair of electrodes that sandwich the solid polymer electrolyte membrane. One electrode is an oxygen electrode to which an oxidizing agent is supplied, and the other electrode is a fuel electrode to which hydrogen gas is supplied.

  FIG. 1 is a schematic view of an embodiment of a solid polymer fuel cell. As shown in the figure, a polymer electrolyte fuel cell 10 includes a membrane electrode assembly (MEA) 100 and a membrane electrode assembly 100 disposed so as to sandwich the membrane electrode assembly 100 outside the membrane electrode assembly. And a pair of separators 200. A current collector 300 is disposed outside the separator 200. The membrane electrode assembly 100 includes a proton conductive solid polymer electrolyte membrane 110, a pair of electrode catalyst layers 120 arranged to sandwich the solid polymer electrolyte membrane 110, the polymer electrolyte membrane 110, and an electrode catalyst. It is a laminate having a pair of gas diffusion layers 130 arranged so as to sandwich the layer 120. If necessary, a carbon layer 140 or the like may be laminated.

  In the pair of separators 200 that sandwich the membrane electrode assembly 100, a gas flow path 210 is formed on a surface in contact with the gas diffusion layer 130. An oxidant such as air or oxygen gas is supplied to the gas flow path 210 on the oxygen electrode side. A fuel gas such as hydrogen gas is supplied to the gas flow path 210 on the fuel electrode side. The reaction gas supplied to the gas flow path 210 reaches the electrode catalyst layer 120 through the porous gas diffusion layer 130 and the carbon layer 140, and electrons are generated by an electrochemical reaction represented by the following formulas (1) and (2). Occur. The electrons are taken out to an external circuit through the current collector 300 and used as electric energy.

  The electrode reaction in the polymer electrolyte fuel cell proceeds in the electrode catalyst layer 120. Therefore, the battery performance of the polymer electrolyte fuel cell depends greatly on the characteristics of the electrode catalyst layer. In order to improve the battery performance, the components of the electrode catalyst layer, the blending ratio of the components, the structure of the electrode catalyst layer, etc. It is important how to devise.

  In the battery performance required for fuel cells, output improvement is strongly demanded. If a battery with a high output is used, the fuel cell as a power source can be made small and light, and effects such as an increase in the space inside the fuel cell vehicle and an improvement in fuel consumption can be obtained. In addition to the improvement in output, improvement in durability is also desired. In particular, in applications such as automobiles that are used for a long period of time, it is required to reduce the decrease in discharge voltage associated with use as much as possible and to improve the reliability of the vehicle.

As a technique for improving the characteristics of the polymer electrolyte fuel cell, for example, Patent Document 1 proposes a technique for controlling the blending ratio of components in the electrode catalyst layer on the oxygen electrode side. Specifically, in an electrocatalytic catalyst carrier comprising a catalytic active material such as platinum, a catalytic active material such as carbon powder, and an electrode catalyst layer comprising a proton conducting polymer, proton conductivity to the conductive catalyst carrier A technique has been proposed in which the polymer mass ratio (proton conductive polymer mass / conductive catalyst carrier mass) is 0.8 to 1.0. However, further improvement is demanded regarding the durability of the polymer electrolyte fuel cell.
JP 2003-115299 A

  Accordingly, an object of the present invention is to provide means for improving the durability of a polymer electrolyte fuel cell.

  The present invention is an electrode catalyst layer for a solid polymer fuel cell, comprising a conductive catalyst carrier, a catalyst active material supported on the conductive catalyst carrier, a proton conductive polymer, and a water repellent material.

  The present invention also includes a step of preparing a liquid containing a conductive catalyst carrier, a catalyst active material supported on the conductive catalyst carrier, and a proton conductive polymer, volatilizing the solvent from the liquid, and further performing a heat treatment. A step of obtaining a powder comprising the conductive catalyst carrier, the catalyst active material, and the polymer, a step of preparing an electrode ink including the powder and a water repellent material, and applying the electrode ink And forming a film containing the conductive catalyst carrier, the catalyst active material supported on the conductive catalyst carrier, the proton conductive solid polymer, and the water repellent material by volatilizing the solvent; Is a method for producing an electrode catalyst layer.

  The present invention provides a polymer electrolyte fuel cell having a high initial voltage and excellent durability.

  In the polymer electrolyte fuel cell, electric power is generated by the reaction at the oxygen electrode and the fuel electrode described above. At this time, protons generated around the catalyst active material present in the electrode catalyst layer on the fuel electrode side reach the solid polymer electrolyte membrane via the proton conductive polymer dispersed in the electrode catalyst layer, and It passes through the solid polymer electrolyte membrane and moves to the oxygen electrode side. Thereafter, the catalyst active material is reached via the proton conductive polymer dispersed in the electrode catalyst layer on the oxygen electrode side, and reacts with oxygen gas and electrons that have passed through the external circuit to generate water.

  In a fuel cell, water is generated with a power generation reaction, and when this water stays in the polymer electrolyte fuel cell, it becomes one of the causes for degrading the performance of the fuel cell. That is, the generated water causes clogging of the gas flow path in the separator and uneven water distribution in the electrode catalyst layer, and the electrode catalyst layer is corroded and deteriorated, so that the performance of the polymer electrolyte fuel cell is lowered. To do.

  For example, when carbon black is used as the conductive carrier and platinum is used as the catalyst active material, the carbon black as the carrier is corroded by the next reaction due to an increase in electrode potential due to fuel depletion that occurs during start and stop and battery operation.

  When the carbon black is corroded, the porous structure of the electrode catalyst layer is destroyed, and the battery performance deteriorates due to a decrease in the diffusibility of the fuel gas and oxygen gas and a decrease and blockage of the proton conduction path in the electrode catalyst layer. Further, an increase in battery resistance due to a decrease in electronic conductivity also contributes to a decrease in battery performance. Furthermore, when the joining part of platinum and carbon black peels off, when the platinum particles are fused and the surface area of platinum is reduced, the battery performance is lowered. As described above, since various adverse effects are caused by the generated water, it is preferable to take measures against corrosion deterioration in the polymer electrolyte fuel cell so that the generated water does not deteriorate due to the water remaining in the catalyst layer. .

  In the first aspect of the present invention, the water repellent material is contained in the electrode catalyst layer, thereby improving the water separation from the electrode catalyst layer and preventing the electrode catalyst layer from being corroded. Specifically, the first of the present invention is a solid polymer fuel cell comprising a conductive catalyst carrier, a catalyst active material supported on the conductive catalyst carrier, a proton conductive polymer, and a water repellent material. This is an electrode catalyst layer.

  Hereinafter, the configuration of the electrode catalyst layer of the present invention will be described in detail.

  The conductive catalyst carrier is a substance having a role of supporting a catalyst active material and having conductivity so that electrons can move. The conductive catalyst carrier is not particularly limited as long as it can carry a catalyst active material. The catalyst carrier to be actually used may be determined in consideration of the characteristics of the catalyst carrier, compatibility with the electrode active material, and the like. Specific examples of the conductive catalyst carrier include carbon blacks such as acetylene black, carbon materials such as activated carbon and graphite, and various metals. Other conductive catalyst supports may be used.

  The particle size of the conductive catalyst carrier is not particularly limited, but is preferably 5 to 100 nm, more preferably 30 to 50 nm.

The specific surface area of the conductive catalyst support is not particularly limited, preferably 200~1200m ² / g, more preferably 500 to 1000 m ² / g. If the specific surface area is too small, the dispersibility of the electrode active material and the proton conductive polymer on the conductive catalyst carrier may be reduced, and sufficient battery performance may not be exhibited. On the other hand, if the specific surface area is too large, the effective utilization rate of the electrode active material and the proton conductive polymer may be reduced, and sufficient battery performance may not be exhibited.

The amount of the catalyst active material supported on the conductive catalyst carrier is not particularly limited, but is preferably 0.01 to 5 mg / cm ² , more preferably 0.1 to 1 mg / cm ² . If the supported amount of the catalyst active material is too small, the catalyst function may not be sufficiently exhibited. If the amount of the catalyst active material supported is too large, there may be no particular problem from the viewpoint of the catalyst function. However, even if more catalyst active material is supported, an increase in effect commensurate with the increase in production cost can be obtained. It becomes difficult to be.

  The catalytic active material is a material having a function of promoting an electrode reaction at the fuel electrode or the oxygen electrode. A catalyst active material will not be specifically limited if it has a function which accelerates | stimulates the electrode reaction in the electrode arrange | positioned. Specific examples of the catalyst active material include platinum, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum, and alloys thereof. Is mentioned. Other catalytic active materials may be used.

  The particle size of the catalyst active material is not particularly limited, but is preferably 1 to 30 nm, and more preferably 1.5 to 10 nm. From the viewpoint of improving the catalyst utilization rate, the smaller the particle size, the better. However, when the particle size is too small, it becomes difficult to produce the catalyst active material.

  The proton conductive polymer means a polymer having the ability to move protons. The proton conductive polymer plays a role of transmitting protons generated around the catalyst active material on the fuel electrode side. As the proton conductive polymer, a polymer having the same configuration as the polymer constituting the solid polymer electrolyte membrane can be used. For example, perfluorocarbon sulfonic acid polymer, polystyrene sulfonic acid, polytrifluorostyrene sulfonic acid, or the like can be used as the proton conductive polymer.

  Preferably, the ion exchange capacity (EW) of the proton conducting polymer is in a predetermined range. Specifically, the ion exchange capacity (EW) of the proton conducting polymer is preferably 700 to 1200 g / ew, more preferably 900 to 1100. “EW” shown here represents the equivalent mass of the exchange group having proton conductivity. This mass is the dry mass of the ion exchange membrane per equivalent of ion exchange groups, and is expressed in units of g / ew. If the ion exchange capacity is too small, the hydrophilicity of the electrode catalyst layer is increased, and the generated water may not be smoothly moved. On the other hand, when the ion exchange capacity is too large, proton conductivity is lowered, and sufficient battery performance is hardly obtained. However, the technical scope of the present invention is not limited to the above range.

  The electrode catalyst layer of the present invention further contains a water repellent material. The water repellent material is higher in water repellency than the catalyst active material, conductive catalyst carrier, and proton conductive polymer contained in the electrode catalyst layer, and imparts water repellency to the electrode catalyst layer to the outside of the electrode catalyst layer. It means a material having a function of promoting the discharge of water.

  The higher the water repellency of the water repellent material is, the more suitable for obtaining the effects of the present invention. Specifically, when the static contact angle to water is investigated using a sheet made of a water repellent material, the contact angle is preferably 90 to 160 °, more preferably 100 to 150 °, and still more preferably 105 to 135 °. The contact angle with water is calculated using water as a test solution. Specifically, it can be calculated by the following measurement method. 20 μl is dropped on the plane of the test article, and then the droplet is enlarged on a monitor using a microscope VH-6110 (manufactured by Keyence Corporation). By image processing, the height h of the droplet, and the distance a between the perpendicular point between the vertex of the droplet and the horizontal plane and the intersection of the droplet and the horizontal plane are measured, and the following equation θ = 2 × arctan (h / a) Based on this, the contact angle is calculated. For contact angle measurement, other contact angle measuring devices may be used as long as reliable data can be obtained.

  Examples of the water repellent material include compounds containing fluorine atoms. In general, a compound containing a fluorine atom has high water repellency. Specific examples of the water repellent material include polytetrafluoroethylene and carbon fluoride.

  The content ratio of the material constituting the electrode catalyst layer may be determined in consideration of the function as the electrode catalyst layer. In determining the content ratio of each material, it is preferable to consider the balance of the functions of each material. For example, in order to sufficiently advance the electrode reaction, it is necessary to secure an amount of the catalyst carrier containing the catalyst active material. However, when the proton conductive polymer is insufficient, the conductivity of the generated protons is lowered, and the battery performance may be deteriorated. Further, when the water repellent material is insufficient, the generated water is not sufficiently discharged, and the durability may be reduced.

  Preferably, the mass ratio X of the water repellent material to the mass of the conductive catalyst carrier (water repellent material mass / conductive catalyst carrier mass) is 0.0001 ≦ X ≦ 0.5. More preferably, the mass ratio X is 0.001 ≦ X ≦ 0.2. When X is too small, there is a possibility that sufficient corrosion resistance cannot be obtained due to a lack of water repellent material. On the other hand, when X is too large, there is a possibility that the electron conduction resistance in the electrode catalyst layer increases due to an excessive water repellent material, and sufficient battery performance cannot be obtained. By setting X in the above range, it is possible to impart appropriate water repellency to the electrode catalyst layer while ensuring battery performance. However, the present invention can be carried out even outside the above range. The mass ratio X can be controlled by adjusting the raw material ratio when producing the electrode catalyst layer.

  Preferably, the mass ratio Y of the proton conductive polymer to the mass of the conductive catalyst carrier (proton conductive polymer mass / conductive catalyst carrier mass) is 0.5 ≦ Y ≦ 1.2. If Y is too small, the proton conduction path may decrease, and sufficient battery performance may not be obtained in the early stage of power generation. On the other hand, when Y is too large, the battery performance at the initial stage of power generation can be satisfied, but there is a possibility that the performance degradation due to battery operation for a long time becomes large. The proton conducting polymer is altered by long-time battery operation. Therefore, it is presumed that the influence of alteration increases when the blending ratio of the proton conducting polymer is too high. However, the present invention can be carried out even outside the above range. The mass ratio Y can be controlled by adjusting the raw material ratio when producing the electrode catalyst layer.

  The electrode catalyst layer may contain other materials as necessary.

  A second aspect of the present invention is a polymer electrolyte fuel cell in which the first electrode catalyst layer of the present invention is disposed on at least one of an oxygen electrode and a fuel electrode. As the configuration of the solid polymer fuel cell, as shown in FIG. 1, there is a structure in which the electrode catalyst layer 120, the gas diffusion layer 130, and the separator 200 are disposed on both sides of the polymer electrolyte membrane 110. However, it is of course possible to apply the first electrode catalyst layer of the present invention to a polymer electrolyte fuel cell having a configuration different from that shown in the drawing. In the present invention, the constituent material other than the electrode catalyst layer is not particularly limited as long as the first electrode catalyst layer of the present invention is disposed on at least one of the oxygen electrode and the fuel electrode.

  The third aspect of the present invention relates to a method for producing an electrocatalyst layer comprising a conductive catalyst carrier, a catalyst active material supported on the conductive catalyst carrier, a proton conductive solid polymer, and a water repellent material. Specifically, the third aspect of the present invention includes a step of preparing a liquid containing a conductive catalyst carrier, a catalyst active material supported on the conductive catalyst carrier, and a proton conductive polymer, and a solvent from the liquid. And a heat treatment to obtain a powder comprising the conductive catalyst carrier, the catalyst active material, and the polymer, and a step of preparing an electrode ink containing the powder and a water repellent material And by applying the electrode ink and volatilizing the solvent, the conductive catalyst carrier, the catalyst active material supported on the conductive catalyst carrier, the proton conductive solid polymer, and the water repellent material Forming a film containing the electrode catalyst layer.

  Hereinafter, the third aspect of the present invention will be described in the order of steps. The materials constituting the electrode catalyst layer, such as a catalyst active material, a conductive catalyst carrier, a proton conductive polymer, and a water repellent material, are the same as those described in the first aspect of the present invention. Omitted.

  First, a liquid containing a conductive catalyst carrier, a catalyst active material supported on the conductive catalyst carrier, and a proton conductive polymer is prepared. A liquid is obtained by adding these materials to a solvent in a predetermined compounding ratio and mixing them. The solvent is not particularly limited, but water is used. Other solvents such as ethylene glycol may be used in combination. Since the conductive catalyst carrier and the catalyst active material are not dissolved in water, a slurry is usually obtained.

  Next, the solvent is volatilized from the liquid containing the conductive catalyst carrier, the catalyst active material supported on the conductive catalyst carrier, and the proton conductive polymer. The means for volatilizing the solvent is not particularly limited. For example, it is volatilized forcibly in a vacuum atmosphere.

  After volatilizing the solvent, heat treatment is performed to obtain a powder composed of a conductive catalyst carrier, a catalyst active material, and a proton conductive polymer. By performing the heat treatment, the binding property between the proton conductive polymer and the electrode active material can be improved, and the deterioration of the battery performance can be prevented. If the binding property between the proton conducting polymer and the electrode active material is insufficient, the proton conducting polymer is liberated from the surface of the electrode active material during a long continuous operation, and effective protons on the surface of the electrode active material are obtained. There is a risk of the conduction path disappearing. This problem can be solved by improving the binding property by heat treatment.

  The heat treatment temperature is not particularly limited as long as the binding property between the proton conductive polymer and the electrode active material can be improved, but is preferably less than 140 ° C., more preferably 80 to 120 ° C. In determining the heat treatment temperature, the glass transition temperature of the proton conducting polymer should be taken into consideration. For example, when a perfluorocarbon sulfonic acid polymer is used as the proton conductive polymer, the glass transition temperature of the perfluorocarbon sulfonic acid polymer is around 130 ° C., and thus heat treatment may be performed at a temperature lower than this temperature.

  The heat treatment atmosphere is not particularly limited, but from the viewpoint of preventing an undesirable chemical reaction, it is preferable that the heat treatment is performed in a vacuum atmosphere or an inert gas atmosphere.

  Thereafter, an electrode ink containing a powder obtained by heat treatment and a water repellent material is prepared. The electrode ink is obtained by adding the powder and the water repellent material to a solvent at a predetermined mixing ratio and mixing them. The solvent is not particularly limited, but water is used. Other solvents such as isopropyl alcohol may be used in combination.

  By applying the prepared electrode ink and volatilizing the solvent, a film containing a conductive catalyst carrier, a catalyst active material supported on the conductive catalyst carrier, a proton conductive solid polymer, and a water repellent material is formed. To do. When applying the electrode ink, a known method can be used in the preparation of the electrode catalyst layer. For example, a screen printing method, a die coater method, a spray method, or the like is used. The application amount and application conditions of the electrode ink may be determined based on the knowledge already obtained, and are not particularly limited in the present invention.

  For example, the electrode ink is applied to both sides of the proton conductive polymer electrolyte membrane, and a laminate in which the electrode catalyst layer, the polymer electrolyte membrane, and the electrode catalyst layer are laminated in this order is obtained. A membrane electrode assembly is obtained by hot pressing the laminate and the gas diffusion substrate. However, the manufacturing method of the polymer electrolyte fuel cell is not limited to such a method, and other manufacturing methods may be adopted.

  Hereinafter, the content of the present invention will be described with reference to examples and comparative examples, but the present invention is not limited to these examples.

(Example 1)
Carbon black (CB; specific surface area 800 m ² / g; Ketjen Black EC manufactured by Lion Corporation) supporting platinum (Pt; average particle size 3 nm) was prepared as a catalyst active material. The mass ratio of platinum as the catalyst active material and carbon black as the conductive catalyst carrier was 50:50. To this, a Nafion aqueous solution (5% by mass Nafion solution manufactured by Aldrich) having an ion exchange capacity of 1100 g / ew as a proton conductive polymer and ethylene glycol are added and mixed to obtain a conductive catalyst carrier and a conductive catalyst carrier. A slurry solution A containing a supported catalyst active material and a proton conductive polymer was prepared.

  The solvent in the slurry solution A was volatilized in a vacuum. Thereafter, heat treatment was performed at 110 ° C. in an inert gas atmosphere to obtain a powder A composed of a conductive carrier, a catalyst active material, and a proton conductive polymer.

  Powder A, pure water, isopropyl alcohol, and polytetrafluoroethylene (PTFE) powder (manufactured by Aldrich) as a water repellent material were mixed to prepare slurry solution B used as electrode ink.

On one side of a proton conductive polymer electrolyte membrane (manufactured by DuPont; trade name Nafion 112; film thickness 50 μm), the amount of platinum supported is 0.35 mg / cm ² , the thickness of the catalyst layer is 10 μm, and the coating area is 50 × 50 mm. Thus, slurry solution B was applied by a die coater method. After coating, the coating film was air-dried to form a cathode-side electrode catalyst layer. Using the same method, an anode-side electrode catalyst layer having a platinum loading of 0.35 mg / cm ² , a catalyst layer thickness of 10 μm, and a coating area of 50 × 50 mm is formed on the opposite side of the polymer electrolyte membrane. Filmed.

  The mass ratio X (polytetrafluoroethylene / carbon black) of the water repellent material (polytetrafluoroethylene) to the conductive catalyst carrier (carbon black supporting platinum) was 0.01. The mass ratio Y (Nafion / carbon black) of the proton conductive polymer (Nafion) to the conductive catalyst carrier (carbon black supporting platinum) was 0.85.

  As the gas diffusion layer of the electrode, a carbon paper (TGP-H-060, manufactured by Toray Industries, Inc.) cut out to 55 × 55 mm was prepared on both the anode side and the cathode side. The carbon paper was water repellent treated by immersing it in a solution obtained by diluting an aqueous dispersion of fluororesin (D1 manufactured by Daikin Industries, Ltd.) with pure water for 2 minutes and then drying at 60 ° C. for 10 minutes. The carbon paper after the water repellent treatment was impregnated with 25% by mass of tetrafluoroethylene particles.

  A slurry solution C in which carbon black and tetrafluoroethylene were uniformly dispersed in isopropyl alcohol was applied on one side of the carbon paper by a spray method on the water-repellent carbon paper. The coating film was dried to obtain a gas diffusion substrate composed of carbon paper and a carbon layer (film thickness 50 μm). The gas diffusion substrate was further heat-treated at 350 ° C. for 5 minutes in an inert gas atmosphere. The mass ratio of carbon to polytetrafluoroethylene (PTFE) in the underlayer was 50:50.

Next, the laminated body in which the catalyst layer is formed on both sides of the proton conductive polymer electrolyte membrane and the gas diffusion substrate are hot-pressed for 1 minute under the conditions of 120 ° C. and 20 kgf / cm ² , whereby a membrane electrode assembly is obtained. Got. About the obtained membrane electrode assembly, the performance (initial cell voltage and cell voltage holding ratio) as a fuel cell was evaluated. The results are shown in Table 1.

The initial cell voltage was evaluated by measuring the cell voltage when power was generated at a current density of 1.0 A / cm ² under conditions of atmospheric pressure and cell temperature of 70 ° C. Hydrogen gas was supplied as the fuel gas, and air was supplied as the oxidant. Both gases were humidified at 60 ° C. and then supplied to the cell.

  The cell voltage holding ratio was evaluated by the following procedure. After continuous power generation for 1 hour under the same conditions as those for evaluating the initial cell voltage, power generation was terminated. After power generation was completed, the cell was purged with nitrogen for 10 minutes for both the anode and cathode. The cell was left for 1 hour and continuously operated again under the same conditions. With this series of operations as the conditions for starting and stopping, the cell voltage holding ratio of the cell voltage after repeating the starting and stopping 300 times with respect to the initial cell voltage {(cell voltage after starting and stopping 300 times / initial cell voltage) × 100 (%)} Was calculated. The higher the cell voltage holding ratio, the better the durability.

(Example 2)
A membrane electrode assembly was produced by the same procedure as in Example 1 except that the mass ratio Y (Nafion / carbon black) of the proton conductive polymer to the conductive catalyst support was 1.0, and the fuel cell was manufactured as a fuel cell. Performance was evaluated. The results are shown in Table 1.

(Example 3)
A membrane electrode assembly was produced by the same procedure as in Example 1 except that the mass ratio X (polytetrafluoroethylene / carbon black) of the water-repellent material to the conductive catalyst carrier was set to 0.1. The performance of was evaluated. The results are shown in Table 1.

Example 4
A membrane / electrode assembly was manufactured in the same manner as in Example 1 except that the mass ratio X (polytetrafluoroethylene / carbon black) of the water-repellent material to the conductive catalyst support was 0.18. The performance of was evaluated. The results are shown in Table 1.

(Example 5)
The mass ratio X (polytetrafluoroethylene / carbon black) of the water-repellent material to the conductive catalyst carrier is 0.1, and the mass ratio Y (Nafion / carbon black) of the proton conductive polymer to the conductive catalyst carrier is 0. A membrane / electrode assembly was produced by the same procedure as in Example 1 except that the performance as a fuel cell was evaluated. The results are shown in Table 1.

(Example 6)
A conductive catalyst carrier having a specific surface area of 1000 m ² / g was used, and after the solvent in the slurry solution A was volatilized in vacuum, no heat treatment was performed. Except for these changes, a membrane electrode assembly was produced in the same procedure as in Example 1, and the performance as a fuel cell was evaluated. The results are shown in Table 1.

(Example 7)
A membrane / electrode assembly was produced by the same procedure as in Example 1 except that a conductive catalyst carrier having a specific surface area of 1000 m ² / g was used, and the performance as a fuel cell was evaluated. The results are shown in Table 1.

(Example 8)
A membrane / electrode assembly was produced by the same procedure as in Example 1 except that a Flemion solution (9% by mass Flemion solution manufactured by Asahi Glass Co., Ltd.) having an ion exchange capacity of 900 g / ew was used as the proton conductive polymer. The performance as a fuel cell was evaluated. The results are shown in Table 1.

Example 9
Flemion solution having a mass ratio X (polytetrafluoroethylene / carbon black) of the water-repellent material to the conductive catalyst support of 0.1 and an ion exchange capacity of 900 g / ew as a proton conductive polymer (Asahi Glass Co., Ltd., 9 A membrane / electrode assembly was produced by the same procedure as in Example 1 except that (mass% flemion solution) was used, and the performance as a fuel cell was evaluated. The results are shown in Table 1.

(Example 10)
Using a conductive catalyst carrier having a specific surface area of 1000 m ² / g, the mass ratio X (polytetrafluoroethylene / carbon black) of the water-repellent material to the conductive catalyst carrier is 0.1, and the proton conductive polymer is ion A membrane / electrode assembly was produced in the same procedure as in Example 1 except that a Flemion solution (Asahi Glass Co., Ltd., 9% by mass Flemion solution) with an exchange capacity of 900 g / ew was used. evaluated. The results are shown in Table 1.

(Comparative Example 1)
A conductive catalyst carrier having a specific surface area of 1000 m ² / g was used, and the mass ratio Y (Nafion / carbon black) of the proton conductive polymer to the conductive catalyst carrier was set to 0.8. Further, no water repellent material was used in the production of the electrode catalyst layer. Therefore, the mass ratio X (polytetrafluoroethylene / carbon black) of the water-repellent material to the conductive catalyst carrier is zero. Except for these changes, a membrane electrode assembly was produced in the same procedure as in Example 1, and the performance as a fuel cell was evaluated. The results are shown in Table 1.

(Comparative Example 2)
A conductive catalyst carrier having a specific surface area of 1000 m ² / g was used, and the mass ratio Y (Nafion / carbon black) of the proton conductive polymer to the conductive catalyst carrier was set to 0.9. Further, no water repellent material was used in the production of the electrode catalyst layer. Therefore, the mass ratio X (polytetrafluoroethylene / carbon black) of the water-repellent material to the conductive catalyst carrier is zero. Except for these changes, a membrane electrode assembly was produced in the same procedure as in Example 1, and the performance as a fuel cell was evaluated. The results are shown in Table 1.

(Comparative Example 3)
A conductive catalyst support having a specific surface area of 1000 m ² / g was used, and the mass ratio Y (Nafion / carbon black) of the proton conductive polymer to the conductive catalyst support was set to 1.0. Further, no water repellent material was used in the production of the electrode catalyst layer. Therefore, the mass ratio X (polytetrafluoroethylene / carbon black) of the water-repellent material to the conductive catalyst carrier is zero. Except for these changes, a membrane electrode assembly was produced in the same procedure as in Example 1, and the performance as a fuel cell was evaluated. The results are shown in Table 1.

  As shown in the table, the cell voltage holding ratio is improved by including a water repellent material in the electrode catalyst layer. It can also be seen that the cell voltage holding ratio is improved when heat treatment is performed (Example 7) and when heat treatment is not performed (Example 6).

It is a schematic diagram of one Embodiment of a polymer electrolyte fuel cell.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Solid polymer fuel cell, 100 ... Membrane electrode assembly, 110 ... Solid polymer electrolyte membrane, 120 ... Electrode catalyst layer, 130 ... Gas diffusion layer, 140 ... Carbon layer, 200 ... Separator, 210 ... Gas flow path , 300 ... current collector.

Claims (9)

  An electrode catalyst layer for a solid polymer fuel cell, comprising a conductive catalyst carrier, a catalyst active material supported on the conductive catalyst carrier, a proton conductive polymer, and a water repellent material. ^{2. The} electrode catalyst layer for a polymer electrolyte fuel cell according to claim 1, wherein the conductive catalyst carrier has a specific surface area of 200 to 1200 m ² / g.   The electrode catalyst layer for a polymer electrolyte fuel cell according to claim 1 or 2, wherein an ion exchange capacity (EW) of the proton conducting polymer is 700 to 1200 g / ew.   The electrode catalyst layer for a polymer electrolyte fuel cell according to any one of claims 1 to 3, wherein the water repellent material comprises a compound containing a fluorine atom.   The mass ratio X of the water-repellent material to the mass of the conductive catalyst carrier (water-repellent material mass / conductive catalyst carrier mass) is 0.0001 ≦ X ≦ 0.5. Electrode catalyst layer for polymer electrolyte fuel cells.   The mass ratio Y of the proton conductive polymer to the mass of the conductive catalyst carrier (proton conductive polymer mass / conductive catalyst carrier mass) is 0.5 ≦ Y ≦ 1.2. 6. The electrode catalyst layer for a polymer electrolyte fuel cell according to any one of 5 above.   A polymer electrolyte fuel cell in which the electrode catalyst layer according to any one of claims 1 to 6 is disposed on at least one of an oxygen electrode and a fuel electrode. Preparing a liquid containing a conductive catalyst carrier, a catalyst active material supported on the conductive catalyst carrier, and a proton conductive polymer;
Evaporating the solvent from the liquid and further performing a heat treatment to obtain a powder comprising the conductive catalyst carrier, the catalyst active material, and the polymer;
Preparing an electrode ink comprising the powder and a water repellent material;
A film containing the conductive catalyst carrier, the catalyst active material supported on the conductive catalyst carrier, the proton conductive solid polymer, and the water repellent material by applying the electrode ink and volatilizing the solvent Forming a stage;
A method for producing an electrode catalyst layer, comprising:   The method for producing an electrode catalyst layer according to claim 8, wherein the heat treatment temperature is less than 140 ° C.

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