JP2003168443A - Solid polymer-type fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid polymer-type fuel cell having a high efficiency and a high output density even in case an entrance-neighboring region of a gas flow passage of a cathode catalyst layer becomes to have a dry atmosphere by supplying an oxidizer gas of a low humidity to the cathode in order to operate the solid polymer-type fuel cell system in the high efficiency. <P>SOLUTION: In the solid polymer-type fuel cell provided with an anode, a cathode, a polymer electrolyte membrane between them, and a separator in which the gas flow passage is formed that is arranged on the exterior side of the cathode and that has the entrance and the exit on a face contacted with the cathode, the catalyst layer of the cathode is made to be constituted so that the amount of platinum (alloy) and/or the amount of an ion exchange resin contained per unit area is larger in the entrance neighboring region than that in the exit neighboring region of the gas flow passage. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polymer electrolyte fuel cell.

[0002]

2. Description of the Related Art A hydrogen / oxygen fuel cell has attracted attention as a power generation system that has a reaction product of only water in principle and has almost no adverse effect on the global environment. In particular, the polymer electrolyte fuel cell has a high output density due to the rapid progress of research in recent years, and its practical application is highly expected. Since the polymer electrolyte fuel cells currently under study have a low operating temperature range and are difficult to utilize exhaust heat, under operating conditions where the anode reaction gas utilization rate such as hydrogen and the cathode reaction gas utilization rate such as air are high. High power generation efficiency and high output density are required.

A gas diffusion electrode used in a polymer electrolyte fuel cell usually comprises a catalyst layer and a gas diffusion layer, and the catalyst layer contains a catalyst and an ion exchange resin coating the catalyst, The catalyst layer is bonded to the polymer electrolyte membrane to form a membrane-electrode assembly including the membrane and the electrode. And
The three-phase interface where the ion exchange resin (strictly speaking, the part of the ion exchange group) that is continuously connected from the polymer electrolyte membrane and the catalyst and the reaction gas are in contact is the main part where the electrode reaction takes place. Therefore, it is important to increase the number of the three-phase interfaces in order to increase the power density of the fuel cell. In particular, increasing the number of reaction sites on the cathode where the reaction overvoltage is large in the four-electron reaction leads to higher power density.

[0006] In a usual polymer electrolyte fuel cell, for example, a membrane electrode assembly is laminated to form a stack via a separator 1 having grooves on both sides which are gas channels 2 as shown in FIG. To do. At the cathode, an oxidant gas such as air is supplied from the inlet 21 of the gas flow path 2, flows in the plane of the gas diffusion electrode, and is discharged from the outlet 22 of the gas flow path. 1A is a front view of the separator as seen from the surface in contact with the cathode or the anode, and FIG.
FIG. 7 is a cross-sectional view taken along the line AA ′ in FIG. In FIG. 1A, the arrow indicates the direction of gas flow.

When the reaction efficiency is important, the ion exchange resin in the membrane and the catalyst layer is preferably moistened in order to ensure conductivity, and therefore the reaction gas is humidified before being supplied. However, when importance is placed on the efficiency of the system of the entire fuel cell, it is desirable that the oxidant gas is humidified under a mild humidification condition and supplied in a low humidification state having a dew point lower than the operating temperature of the cell. In this case, the area near the inlet of the gas flow path has a dry atmosphere, and the area near the outlet has a relatively wet atmosphere due to the accumulation of water produced by the cell reaction within the catalyst layer surface.
Therefore, the cathode catalyst layer has different reaction efficiencies in the region near the inlet and the region near the outlet of the gas flow path. However, conventionally, the cathode catalyst layer has a uniform structure in the plane,
It has not been possible to have different functions in the region near the inlet and the region near the outlet of the gas flow path.

As a countermeasure against this, Japanese Patent Laid-Open No. 2001-572
No. 18 proposes a polymer electrolyte fuel cell in which the gas diffusivity of the reaction gas upstream portion of the gas diffusion layer is made lower than that of the reaction gas downstream portion (specifically, the average pore diameter of the gas diffusion layer is made smaller). ing. However, in this polymer electrolyte fuel cell, the region near the inlet of the gas flow path in the cathode is essentially drier due to the effect of the gas diffusion layer, but is essentially drier than the region near the outlet. The number of reaction sites that substantially function in the region near the inlet of the flow channel was small, and the output of the fuel cell could not be sufficiently increased.

[0007]

As described above, when the low-humidification oxidant gas is supplied to the cathode, the cathode catalyst layer in the area near the inlet of the gas flow channel becomes dry, and the area near the outlet is compared. It becomes a moist atmosphere. Therefore, the water content of the ion-exchange resin coating the catalyst is low, the passage of protons in the resin cannot be sufficiently secured, and the number of three-phase interfaces that substantially function is reduced. Therefore, when the in-plane configuration of the cathode catalyst layer, that is, the in-plane distribution of the catalyst layer and the ion exchange resin is uniform, the area near the inlet of the gas flow path substantially functions as compared with the area near the outlet. The number of reaction sites is greatly reduced. Therefore, the output density of the electrode as a whole becomes low.

Therefore, according to the present invention, there is no significant difference in the number of reaction sites substantially functioning in the area near the inlet and the area near the outlet of the gas flow path in the plane of the cathode catalyst layer.
It is an object of the present invention to provide a polymer electrolyte fuel cell having excellent output characteristics by providing a cathode catalyst layer having a substantially uniform current density and a substantially uniform current density.

[0009]

The inventors of the present invention have found that the amount of catalyst contained per unit area in the catalyst layer in the region near the inlet of the gas channel and the region near the outlet of the gas channel of the cathode catalyst layer. Alternatively, the amount of the ion exchange resin was changed and the fuel cell characteristics in various patterns were examined. As a result, by increasing the amount of the catalyst (platinum) and / or the amount of ion exchange resin in the area near the inlet of the gas flow path as compared with the area near the outlet,
The present inventors have found that a reaction site that substantially functions in the catalyst layer in the region near the inlet can be sufficiently secured, and that the power density of the polymer electrolyte fuel cell can be efficiently increased, and the present invention has been completed.

According to the present invention, an anode, a cathode, a polymer electrolyte membrane arranged between the anode and the cathode, and an inlet arranged on the side opposite to the surface of the cathode in contact with the polymer electrolyte membrane. A solid polymer electrolyte fuel cell comprising a separator having a gas flow path having an outlet on a surface in contact with the cathode, wherein the cathode is
It has a catalyst layer containing a catalyst containing platinum or a platinum alloy and an ion exchange resin and is adjacent to the polymer electrolyte membrane, and in the catalyst layer, it is included per unit area in a region near the inlet of the gas flow path. There is provided a polymer electrolyte fuel cell characterized in that the amount of platinum is larger than the amount of platinum contained per unit area in the region near the outlet.

In the in-plane distribution of the cathode catalyst layer, the amount of platinum in the area near the inlet of the gas flow path is made larger than the amount of platinum in the area near the outlet so that the number of reaction sites potentially existing in the area near the inlet is increased. It is considered that the absolute amount of is larger than the area near the exit. Therefore, even if the ion-exchange resin is dried in a dry atmosphere by supplying an oxidant gas having a low dew point in the region near the inlet of the gas flow path of the cathode catalyst layer, the number of reaction sites that substantially function is to some extent. Can be secured.

On the other hand, in the area near the outlet of the gas flow path, since there is a cumulative amount of water generated by the cell reaction and the atmosphere is relatively moist, the ion-exchange resin is in a water-containing state, and the area near the inlet is latent. It is possible to secure a sufficient number of reaction sites that substantially function during power generation, even if the number of reaction sites does not exist. Therefore, when the structure of the cathode catalyst layer in the present invention is adopted, the in-plane current density distribution of the cathode catalyst layer can be efficiently made uniform, and the output density of the fuel cell can be increased. Further, since an unnecessarily large amount of catalyst is not contained in the region near the outlet of the gas flow path, it is possible to efficiently and economically increase the power density of the membrane electrode assembly.

The present invention also includes an anode, a cathode,
A polymer electrolyte membrane disposed between the anode and the cathode, and a surface on which a gas flow path having an inlet and an outlet disposed on the opposite side of the surface of the cathode in contact with the polymer electrolyte membrane contacts the cathode. A separator formed on the
In the solid polymer electrolyte fuel cell, the cathode has a catalyst layer including a catalyst containing platinum or a platinum alloy and an ion exchange resin, and the catalyst layer is adjacent to the polymer electrolyte membrane. A solid polymer characterized in that the amount of ion exchange resin contained per unit area in the region near the inlet of the gas flow channel is larger than the amount of ion exchange resin contained per unit area in the region near the outlet. Type fuel cell is provided.

In the in-plane distribution of the cathode catalyst layer, the amount of the ion-exchange resin coating the catalyst in the area near the inlet of the gas flow path is set to be larger than that in the area near the outlet, so that it is potentially present in the area near the inlet. The absolute amount of reaction sites can be increased. Therefore, by supplying an oxidant gas having a low dew point, even if the ion exchange resin is dried in a dry atmosphere in the vicinity of the inlet of the gas passage of the cathode catalyst layer, it is possible to secure a certain number of substantially functioning reaction sites. .

On the other hand, in the cathode catalyst layer, the region near the outlet of the gas flow passage has a cumulative amount of the water produced by the cell reaction from the region near the inlet and becomes a relatively moist atmosphere, so that the ion exchange resin becomes hydrated, It is possible to secure a sufficient number of reaction sites during power generation, even if the potential number of reaction sites does not exist as much as the area near the inlet.

Therefore, the amount of the ion exchange resin is increased only in the region near the inlet of the gas flow path of the cathode catalyst layer, and the amount of the ion exchange resin is not unnecessarily increased in the region near the outlet, so that the efficiency and It is possible to increase the output density of the membrane electrode assembly, advantageously in terms of cost. Further, it is possible to eliminate the nonuniformity of the current density distribution in the plane of the cathode catalyst layer.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION In a polymer electrolyte fuel cell,
Considering the efficiency of the entire system, it is preferable to supply a low-dew point, low-humidification oxidant gas (for example, air or oxygen) to the cathode. However, in this case, the area near the inlet of the gas passage of the cathode catalyst layer is dried. The cathode catalyst layer contains a catalyst containing platinum and an ion exchange resin for coating the catalyst to increase the number of reaction sites, but the ion exchange resin cannot obtain proton conductivity until it becomes hydrated, so it is in a dry state. Then, the number of reaction sites during power generation is greatly reduced. That is, the number of reaction sites actually functioning during power generation is greatly reduced compared to the number of reaction sites potentially existing in the region near the inlet of the gas flow path.

On the other hand, in the area near the outlet of the gas flow path of the cathode catalyst layer, the amount of water produced by the cell reaction accumulated from the area near the inlet causes a relatively moist atmosphere, and the ion exchange resin becomes hydrated. However, most of the reaction sites that were originally present substantially function as reaction sites.

Usually, there are various factors that determine the number of reaction sites potentially existing in the cathode catalyst layer, but the content ratios of the catalyst and the ion exchange resin contained in the cathode catalyst layer, their absolute amounts, the mixed state, and the structure. Etc. is the main factor. The present invention focuses on the absolute amount of platinum and / or ion exchange resin constituting the catalyst. But,
Even if only one of platinum and / or ion exchange resin is extremely increased, the number of reaction sites will reach the ceiling. Therefore, in order to reliably increase the number of reaction sites, both the amount of catalyst and the amount of ion exchange resin should be increased. It is preferable to increase.

From the above viewpoint, in the present invention, when the amount of both platinum and ion exchange resin in the cathode catalyst layer is increased in the region near the inlet of the gas flow channel, the cathode catalyst layer is much more reliable than the region near the outlet. It is preferable because the number of reaction sites potentially existing can be increased. In this case, by supplying a gas with a low dew point, even if the area near the inlet of the gas flow channel becomes a dry atmosphere, it is possible to secure a sufficient amount of substantially functional reaction sites in the area near the inlet, and it is relatively wet. The amount of platinum and ion exchange resin may be set not to be unnecessarily large in the region near the outlet of the flow path of the atmosphere gas.

In the present invention, the amount of platinum per unit area in the region near the inlet of the gas passage of the cathode catalyst layer is 0.02 to 1.
It is preferable that the composition is increased by 5 mg / cm ² . When the difference between the amount of platinum per unit area in the inlet vicinity region and the amount of platinum in the outlet vicinity region is less than 0.02 mg / cm ² , the reaction sites in the inlet vicinity region cannot be efficiently increased,
The effect of the configuration of the present invention is small. More preferably 0.
It is at least 05 mg / cm ² . On the other hand, the above difference is 1.5
If it exceeds mg / cm ² , the amount of platinum in the area near the inlet is unnecessarily high and the cost becomes unnecessarily high, and the catalyst layer becomes too thick to reduce the gas diffusivity and, conversely, the cell voltage. May decrease. More preferably 0.9
It is mg / cm ² or less.

Further, the amount of platinum per unit area of the area near the inlet of the gas passage of the cathode catalyst layer is 0.1 to 2.0 mg / cm ² from the viewpoint of securing the battery output and economical efficiency. Is preferred. The catalyst contained in the cathode catalyst layer may contain platinum, and may be composed of platinum or a platinum alloy. However, it is preferable that the catalyst is a supported catalyst in which platinum or a platinum alloy is supported on carbon. On the other hand, the amount of platinum per unit area in the area near the outlet is 0.05 to 1.5 mg.
/ Cm ² is preferable. 0.05 mg / cm ²
If it is less than this, the amount of platinum may be too small to obtain a sufficient battery output. On the other hand, if it exceeds 1.5 mg / cm ² , the amount of platinum is too large, which unnecessarily increases the cost, and the thickness of the catalyst layer becomes too thick, which may reduce the gas diffusivity and the battery output. .

The amount of ion exchange resin contained per unit area in the area near the outlet of the gas flow path of the cathode catalyst layer is 90 with respect to the amount of ion exchange resin contained per unit area in the area near the inlet. % Or less, and the amount of the ion exchange resin contained per unit area in the vicinity of the inlet is preferably 0.1 to 2.5 mg / cm ² . When the amount of ion exchange resin in the area near the outlet exceeds 90% of the amount of ion exchange resin in the area near the inlet, the number of reaction sites in the area near the inlet cannot be increased efficiently, and the effect of the present invention is small. To more efficiently secure the reaction site in the region near the inlet, the above ratio is more preferably 80% or less.

On the other hand, the above ratio is 30% or more, especially 50%.
% Or more is preferable. If the amount of the ion exchange resin in the area near the outlet of the gas flow path is smaller than this range, the amount of the ion exchange resin in the area near the outlet is too small to sufficiently cover the catalyst with the resin, resulting in sufficient battery output. It may not be possible to secure enough reaction sites.

The amount of ion exchange resin per unit area in the region near the inlet of the gas passage of the cathode catalyst layer depends on the amount of catalyst, but from the viewpoint of the initial characteristics and durability of the fuel cell. 0.1 mg / cm ² or more, particularly 0.2 mg / cm
cm ² or more is more preferable. On the other hand, if the amount of the ion exchange resin in the region near the inlet exceeds 2.5 mg / cm ² , the amount of the catalyst must be increased in accordance with the amount of the ion exchange resin, resulting in cost increase. On the contrary, the gas diffusibility of the oxidant gas may worsen and the cell voltage may decrease. Further, the pores of the cathode catalyst layer may be blocked by the ion exchange resin, and the gas diffusibility may be reduced. Considering the performance and the ease of manufacturing the catalyst layer, the amount is more preferably 1.7 mg / cm ² or less.

On the other hand, the amount of the ion exchange resin per unit area in the area near the outlet is preferably 0.09 to 2.25 mg / cm ² . If the amount of the ion exchange resin is too small, the catalyst may not be sufficiently covered with the ion exchange resin, and it may not be possible to secure a reaction site sufficient to obtain a sufficient battery output. On the other hand, if it is more than 2.25 mg / cm ² , the cathode catalyst layer may be too thick, gas diffusivity may be lowered and cell voltage may be lowered, and the cost may be increased more than necessary. Further, the pores of the cathode catalyst layer may be blocked by the ion exchange resin, and the gas diffusibility may be reduced.

Regarding the content of the ion exchange resin contained in the cathode catalyst layer, from the viewpoint of ensuring sufficient proton conductivity in the cathode catalyst layer and the viewpoint of ensuring sufficient reaction sites in the catalyst layer. The mass ratio of the catalyst to the ion exchange resin (mass ratio) is preferably such that the mass of the catalyst: the mass of the ion exchange resin = 4.0: 6.0 to 9.5: 0.5, and the mass of the catalyst: Mass of ion exchange resin = 6.
More preferably, it is 0: 4.0 to 8.0: 2.0. The catalyst referred to here includes the mass of the carrier in the case of a supported catalyst supported on a carrier such as carbon.

In the cathode catalyst layer of the polymer electrolyte fuel cell of the present invention, the area of the gas passage near the inlet where the amount of catalyst and / or the amount of ion exchange resin is large and the area near the outlet where the amount thereof is small) Is preferably 5% or more with respect to the total area of the cathode catalyst layer.
It is more preferably at least 10%, further preferably at least 20%. When the ratio of the area of the region where the amount of the catalyst and / or the amount of the ion exchange resin is large is less than 5% with respect to the total area of the cathode catalyst layer, the low humidification gas in the catalyst layer causes a relatively dry atmosphere. It may not be possible to secure a sufficient reaction site in the area where the battery is charged, and it may not be possible to obtain a high battery output. On the other hand, if it exceeds 95%, the inside of the catalyst layer surface cannot be efficiently separated, and it may not be possible to efficiently obtain a high power density.

Further, the catalyst layer of the cathode is used in an amount of catalyst and / or
Alternatively, an area with a large amount of ion exchange resin (area near the inlet of the gas flow path) and a small area (area near the exit of the gas flow path)
Not only the two regions but also the three or more regions, the amount of the catalyst and / or the ion exchange resin is gradually reduced from the inlet side to the outlet side of the gas flow path. You may do it.

The structure of the present invention is particularly effective when a low humidification gas is supplied to the cathode. That is, the temperature of the gas passage on the cathode side is higher than the operating temperature of the fuel cell by 10
An excellent effect is exhibited when a gas having a dew point of a temperature lower than 0 ° C. or a gas having a dew point of a temperature lower than the operating temperature of the fuel cell by 15 ° C. or more flows. The low-humidification gas referred to here includes non-humidified (dry) gas.

In the present invention, the ion exchange resin contained in the cathode is not particularly limited as long as it is an ion exchange resin exhibiting good ion conductivity in a wet state, but it has a sulfonic acid group from the viewpoint of durability and output characteristics. Perfluorocarbon polymers (which may contain ether-bonding oxygen atoms and the like) are preferred.

The anode catalyst layer in the present invention is not particularly limited, but it contains a catalyst and an ion exchange resin like the cathode. Like the cathode catalyst layer, the anode catalyst layer may have a different composition distribution in the catalyst layer surface,
The in-plane composition may be uniform.

Further, the ion exchange membrane to be the solid polymer electrolyte membrane in the present invention is not particularly limited, and specifically, for example, Flemion manufactured by Asahi Glass Co., Aciplex manufactured by Asahi Kasei, Nafion manufactured by DuPont, Japan. You can use Gore Select made by Gore-Tex. These films are films made of a perfluorocarbon polymer having a sulfonic acid group, but in addition to these, a film made of a perfluorocarbon polymer having a phosphonic acid group or a phenolic hydroxyl group can also be used. Further, a film made of a hydrocarbon-based resin having a sulfonic acid group, a phosphonic acid group or the like or a partially fluorinated hydrocarbon-based resin can also be used. The method for producing the membrane is not particularly limited, and may be an extrusion-molded membrane or a membrane obtained by a casting method from a liquid obtained by dissolving or dispersing an ion exchange resin in a solvent. Further, a reinforcing membrane obtained by compounding a membrane made of an ion exchange resin with a reinforcing material can also be used as the solid polymer electrolyte membrane.

To form the catalyst layer on the ion exchange membrane, the catalyst layer formed on the base material sheet may be hot-press transferred to the membrane, or may be directly applied in a membrane form, The catalyst layer formed on the gas diffusion layer may be hot-press bonded to the film without any particular limitation.

[0035]

EXAMPLES The present invention will be specifically described below with reference to Examples (Examples 1 to 3) and Comparative Examples (Example 4), but the present invention is not limited thereto.

Example 1 As the ion exchange resin contained in the cathode catalyst layer, CF ₂ ═CF ₂ / CF ₂ ═CF— which is a perfluorocarbon polymer having a sulfonic acid group.
_{OCF 2 CF (CF 3) -OCF} 2 CF 2 SO 3 H copolymer (ion exchange capacity _{A R} 1.1 meq / g dry resin (hereinafter referred to as meq./g)) was used. Next, as a catalyst, a supported catalyst in which carbon (trade name: Ketjen Black EC, manufactured by Lion Corp.) was supported by platinum with 54% of the total mass of the catalyst was used, and the catalyst and the above copolymer were used in a mass ratio of 7.
86: 2.14, mixed and stirred in a mixed solvent of ethanol / water (1/1 by mass ratio), and the solid content (total amount of catalyst and resin) of the resulting liquid was 10% by mass. Was prepared. This was used as a catalyst layer forming coating liquid 1.

Next, ethanol / ethanol was added so that the mass ratio of the supported catalyst to the copolymer was 6.47: 3.53.
Mixing and stirring in a mixed solvent of water (1/1 by mass ratio), the solid content (total amount of catalyst and resin) concentration of the resulting liquid is 10% by mass.
Was prepared so that This was used as a catalyst layer forming coating liquid 2.

Next, with reference to FIG. 2, the method for forming the catalyst layer and the production of the membrane electrode assembly will be described. First,
The coating liquid 2 for forming a catalyst layer has a platinum adhesion amount of 0.3 mg / cm on one surface of a base sheet (trade name: Aflon COP, manufactured by Asahi Glass Co., Ltd.) made of a tetrafluoroethylene / ethylene copolymer having a thickness of 50 μm. ^It was applied by a bar coater so as to be ^2, and dried to obtain an anode catalyst layer 33. The base sheet on which the anode catalyst layer was formed was cut out so that the effective electrode area was 25 cm ² .

Next, the cathode catalyst layer was formed as follows. The cathode catalyst layer is equally divided into upper and lower regions, that is, the cathode separator is B- in FIG.
When divided into two at the position of B ′, the cathode catalyst layer which is in contact with the upper part of the position of BB ′, that is, a portion which is a region in the vicinity of the inlet of the gas flow path is defined as a region P, and the position of BB ′ The cathode catalyst layer, which is in contact with the lower portion, that is, the portion which is the area in the vicinity of the outlet of the gas passage is formed as the area Q by the following procedure. The total cathode catalyst layer area (region P
The ratio (%) of the area of the region P and the area of the region Q to the sum of the area of 1 and the area of the region Q) was 50%.

The coating liquid 1 for forming the catalyst layer is applied to the anode catalyst layer 3
3 platinum on amount of 0.44 mg / cm ² to a half of the base sheet prepared separately of the same material as forms the base sheet, it was applied so that the ion exchange resin amount is 0.222mg / cm ² dried This was designated as region P. Next, the coating liquid 2 for forming a catalyst layer was applied to the remaining half of the base sheet so that the amount of platinum deposited was 0.22 mg / cm ² and the amount of ion exchange resin was 0.222 mg / cm ² . Dried
This was designated as region Q. Then, the base sheet on which the cathode catalyst layer 32 including the regions P and Q is formed is placed in the region P.
And the area Q was made equal to each other and the effective electrode area was cut out to be 25 cm ² .

The base sheet having the anode catalyst layer 33 formed thereon and the base sheet having the cathode catalyst layer 32 formed thereon are
Ion-exchange membranes made of a perfluorocarbon polymer having a sulfonic acid group as a polymer electrolyte membrane 31 and facing each other with the surfaces on which the catalyst layers are formed facing each other and reinforced with a fibril-like fluorocarbon polymer (commodity). Name: Flemion HEf2, manufactured by Asahi Glass Co., Ltd., A _R = 1.1
meq. / G, dry film thickness 30 μm), 160 ° C
Hot-pressed at. Since the cathode catalyst layer 32 and the anode catalyst layer 33 were transferred to the polymer electrolyte membrane 31 by hot pressing, the membrane / catalyst layer assembly was obtained by peeling the substrate sheets on both sides.

Next, on both surfaces of this bonded body, carbon cloths (trade name: Carbell CL, manufactured by Japan Gore-Tex Co., Ltd.) whose surfaces are filled with carbon and a water repellent are used as gas diffusion layers 34, 35. Then, a membrane electrode assembly was obtained. The membrane electrode assembly is sandwiched between two separators 36 and 37 each having a groove serving as a gas flow path formed on the surface,
The gas inlet was on the left side in FIG. 2 and the reaction gas outlet was on the right side.

Example 2 First, the coating liquid 2 for forming a catalyst layer used in Example 1 was prepared. Next, the supported catalyst used in Example 1 and the copolymer were mixed and stirred in a mixed solvent of ethanol / water (mass ratio of 1/1) such that the mass ratio was 8.46: 1.54. Solid content of the resulting liquid (total amount of catalyst and resin)
The concentration was adjusted to 10% by mass. This was designated as Catalyst Layer Forming Coating Liquid 3.

The catalyst layer forming coating liquid 2 was used in place of the catalyst layer forming coating liquid 1, and the amount of platinum deposited was 0.33 mg / cm 3.
² , the area P is formed by coating so that the amount of the ion exchange resin is 0.333 mg / cm ^2, and the catalyst layer forming coating solution 2
Instead of using the catalyst layer-forming coating liquid 3, the amount of deposited platinum was 0.33 mg / cm ² , and the amount of ion exchange resin was 0.111.
A cathode catalyst layer was formed in the same manner as in Example 1 except that the region Q was formed by coating so that the amount became mg / cm ² . A membrane / catalyst layer assembly was obtained in the same manner as in Example 1 except that the cathode catalyst layer obtained as described above was used.
A membrane electrode assembly was produced in the same manner as in Example 1.

Example 3 A mixed solvent of ethanol / water (mass ratio of 1/1) was used so that the mass ratio of the supported catalyst used in Example 1 and the copolymer was 7.10: 2.90. The mixture was mixed and stirred in such a manner that the concentration of the solid content (total amount of catalyst and resin) of the obtained liquid was adjusted to 10% by mass. This was used as a catalyst layer forming coating liquid 4.

Then, the mass ratio of the supported catalyst used in Example 1 to the copolymer was adjusted to 7.86: 2.14 in a mixed solvent of ethanol / water (mass ratio of 1/1). Mix and stir at 50 ° C., and the resulting liquid has a solid content (total amount of catalyst and resin) of 1
It was prepared to be 0% by mass. This was used as a catalyst layer forming coating liquid 5.

The catalyst layer forming coating liquid 4 was used in place of the catalyst layer forming coating liquid 1, and the amount of platinum deposited was 0.44 mg / cm 2.
² , the area P is formed by coating so that the amount of the ion exchange resin is 0.333 mg / cm ^2, and the catalyst layer forming coating solution 2
Instead of using the coating liquid 5 for forming a catalyst layer, the amount of platinum deposited was 0.22 mg / cm ² , and the amount of ion exchange resin was 0.111.
A cathode catalyst layer was formed in the same manner as in Example 1 except that the region Q was formed by coating so that the amount became mg / cm ² . A membrane / catalyst layer assembly was obtained in the same manner as in Example 1 except that the cathode catalyst layer obtained as described above was used.
A membrane electrode assembly was produced in the same manner as in Example 1.

Example 4 A mixed solvent of ethanol / water (mass ratio of 1/1) was used so that the mass ratio of the supported catalyst used in Example 1 and the copolymer was 7.33: 2.67. The mixture was mixed and stirred in such a manner that the concentration of the solid content (total amount of catalyst and resin) of the obtained liquid was adjusted to 10% by mass. This was used as a catalyst layer forming coating liquid 6.

The catalyst layer-forming coating liquid 6 was applied to the entire area of the substrate sheet so that the amount of platinum deposited was 0.33 mg / cm ² and the amount of ion exchange resin was 0.222 mg / cm ^2, and dried. A membrane / catalyst layer assembly was obtained in the same manner as in Example 1 except that the cathode catalyst layer obtained as described above was used, and a membrane / electrode assembly was prepared in the same manner as in Example 1.

[Battery Characteristic Test] Electronic load device FK40 was prepared by placing separators as shown in FIG. 1 on both outer sides of each unit cell (membrane electrode assembly) of Examples 1 to 4 as a measuring cell.
0L (Takasago Seisakusho) and DC power supply EX750L
Using Takasago Seisakusho, a measurement test of current-voltage characteristics was performed. Measurement conditions are hydrogen outlet pressure; 0.15 MPa,
Air outlet pressure; 0.15 MPa, operating temperature of measuring cell;
75 ° C., the dew point of the air supplied to the cathode is 45 ° C.,
The dew point of hydrogen supplied to the anode is 70 ° C., the output current density is 0 A / cm ² (OCV), 0.2 A / cm ² ,
The cell voltage (voltage between terminals) of the measurement cell when changed to 1.0 A / cm ² was measured. Table 2 shows the test results of each of these measurement cells.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

According to the structure of the present invention, the absolute amount of reaction sites potentially existing in the region near the inlet of the gas flow channel becomes larger than that in the region near the outlet of the gas flow channel. for that reason,
Even if the area near the inlet of the gas flow path in the cathode catalyst layer becomes a dry atmosphere due to the low-humidification oxidant gas being supplied to the cathode catalyst layer, a sufficient amount of effective reaction sites are secured even during power generation. It On the other hand, in the region near the outlet of the gas flow path, a wet state is obtained because there is water generated by the battery reaction accumulated from the region near the inlet. Therefore, since the ion-exchange resin coating the catalyst is in a water-containing state, an effective reaction site can be sufficiently secured even if the number of potentially existing reaction sites is not as large as the area near the inlet of the gas flow path.

That is, in the constitution of the cathode catalyst layer in the present invention, the number of reaction sites potentially existing in the region near the inlet and the region near the outlet of the gas flow passage is adjusted by the reaction of the fuel cell. By adopting such a constitution of the present invention, a high-performance solid polymer fuel cell can be obtained economically and efficiently.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention relating to an in-plane distribution structure of a cathode catalyst layer.

FIG. 2 is a diagram showing an embodiment of a polymer electrolyte fuel cell of the present invention.

[Explanation of symbols]

2: Separator 21: Inlet of gas flow path 22: Exit of gas flow path 31: Polymer electrolyte membrane 32: cathode catalyst layer 33: Anode catalyst layer 34, 35: Gas diffusion layer 36, 37: Separator

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Claims (7)

[Claims] 1. An anode, a cathode, a polymer electrolyte membrane arranged between the anode and the cathode, and an inlet and an outlet arranged on the opposite side of the surface of the cathode in contact with the polymer electrolyte membrane. A solid polymer electrolyte fuel cell comprising a separator having a gas flow path formed on a surface in contact with the cathode, wherein the cathode includes a catalyst containing platinum or a platinum alloy and an ion exchange resin, It has a catalyst layer adjacent to a molecular electrolyte membrane, and in the catalyst layer, the amount of platinum contained per unit area in the region near the inlet of the gas flow channel is contained per unit area in the region near the outlet. The polymer electrolyte fuel cell is characterized in that the amount of platinum contained is greater than that of platinum. 2. The amount of platinum contained per unit area in the region near the inlet is 0.02-1.5 mg / cm2 from the amount of platinum contained per unit area in the region near the outlet.
^The polymer electrolyte fuel cell according to claim 1, wherein the amount is ^two . 3. An anode, a cathode, a polymer electrolyte membrane arranged between the anode and the cathode, and an inlet and an outlet arranged on the opposite side of a surface of the cathode in contact with the polymer electrolyte membrane. A solid polymer electrolyte fuel cell comprising a separator having a gas flow path formed on a surface in contact with the cathode, wherein the cathode includes a catalyst containing platinum or a platinum alloy and an ion exchange resin, Having a catalyst layer adjacent to a molecular electrolyte membrane, in the catalyst layer, the amount of ion exchange resin contained per unit area in the region near the inlet of the gas flow path,
The polymer electrolyte fuel cell is characterized in that the amount of the ion exchange resin contained per unit area in the region near the outlet is larger than that of the polymer electrolyte fuel cell. 4. In the catalyst layer, the amount of ion exchange resin contained per unit area in the region near the inlet of the gas flow channel is equal to that of the ion exchange resin contained per unit area in the region near the outlet. The polymer electrolyte fuel cell according to claim 1 or 2, which is larger than the amount. 5. The amount of ion exchange resin contained per unit area in the region near the outlet is 9 with respect to the amount of ion exchange resin contained per unit area in the region near the inlet.
0% or less, and the amount of ion exchange resin contained per unit area in the area near the inlet is 0.1 to 2.5 m.
The polymer electrolyte fuel cell according to claim 3 or 4, which has g / cm ² . 6. The ion exchange resin comprises a perfluorocarbon polymer having a sulfonic acid group.
The polymer electrolyte fuel cell according to any one of 1. 7. The polymer electrolyte fuel cell according to claim 1, wherein a gas having a dew point at a temperature lower than the operating temperature of the fuel cell by 10 ° C. or more flows through the gas flow path.