JP5137387B2 - Method for producing membrane-catalyst layer assembly - Google Patents

Description

The present invention relates to the production how the membrane-catalyst layer assembly.

  Since fuel cells (FC) have high power generation efficiency and a low environmental load, they are expected to spread in the future as distributed energy systems. In particular, polymer electrolyte fuel cells using a polymer electrolyte having cation (hydrogen ion) conductivity have high output density, low operating temperature, and can be miniaturized. It is expected to be used in mobile units, distributed power generation systems, and home cogeneration systems.

  The polymer electrolyte fuel cell generates electric power and heat simultaneously by electrochemically reacting a fuel gas containing hydrogen and an oxidant gas such as air containing oxygen. Here, FIG. 17 is a schematic cross-sectional view showing an example of a basic configuration of a unit cell mounted on a conventional polymer electrolyte fuel cell. 18 is a schematic sectional view showing an example of a basic configuration of a membrane-electrode assembly (MEA) mounted on the unit cell 100 shown in FIG. 17, and FIG. 19 is shown in FIG. 1 is a schematic cross-sectional view showing an example of a membrane-catalyst layer assembly (CCM: Catalyst-coated membrane) constituting a membrane electrode assembly 101. FIG.

  As shown in FIG. 19, in the membrane-catalyst layer assembly 102, an electrode catalyst (for example, a platinum-based metal catalyst) is supported on carbon powder on both surfaces of a polymer electrolyte membrane 111 that selectively transports hydrogen ions. A catalyst layer 112 containing the obtained catalyst-supporting carbon and a polymer electrolyte having hydrogen ion conductivity is formed. As the polymer electrolyte membrane 111, a polymer electrolyte membrane made of perfluorocarbon sulfonic acid (for example, Nafion (trade name) manufactured by Du Pont, USA) is generally used.

  As shown in FIG. 18, the membrane electrode assembly 101 is formed by forming a gas diffusion layer 113 having both air permeability and electronic conductivity on the outer surface of the catalyst layer 112 using, for example, carbon paper subjected to water repellent treatment. Consists of. The combination of the catalyst layer 112 and the gas diffusion layer 113 constitutes an electrode (anode or cathode) 114. Furthermore, as shown in FIG. 17, the unit cell 100 includes a membrane electrode assembly 101, a gasket 115, and a pair of separators 116. The gasket 115 is disposed around the electrode with a polymer electrolyte membrane interposed therebetween in order to prevent leakage and mixing of the supplied fuel gas and oxidant gas to the outside. The gasket 115 is integrated with the electrode and the polymer electrolyte membrane in advance. A combination of the polymer electrolyte membrane 111, the pair of electrodes 114 (the catalyst layer 112 and the gas diffusion layer 113), and the gasket 115 may be referred to as a membrane electrode assembly.

  A pair of separators 116 for mechanically fixing the membrane electrode assembly 101 is disposed outside the membrane electrode assembly 101. A reaction gas (fuel gas or oxidant gas) is supplied to the electrode of the separator 116 in contact with the membrane electrode assembly 101, and an electrode reaction product and a gas containing an unreacted reaction gas are supplied from the reaction field to the outside of the electrode. A gas flow path 117 is formed for carrying it away. Although the gas channel 117 can be provided separately from the separator 116, a method of forming a gas channel by providing a groove on the surface of the separator is generally used. Further, a groove is provided on the side of the separator 116 opposite to the membrane electrode assembly 101 to form a cooling water flow path 118.

Thus, the membrane electrode assembly 101 is fixed by the pair of separators 116, the fuel gas is supplied to the gas flow path of one separator, and the oxidant gas is supplied to the gas flow path of the other separator. When a practical current density of 10 to several hundred mA / cm ² is applied, a single cell can generate an electromotive force of about 0.7 to 0.8V. However, when a polymer electrolyte fuel cell is normally used as a power source, a voltage of several to several hundred volts is required. In practice, the required number of cells are connected in series and stacked. Use as

  In order to supply the reaction gas to the gas flow path 117, the reaction gas supply pipe is branched into a number corresponding to the number of separators to be used, and the branch destinations are directly connected to the gas flow path on the separator. A manifold that is a member is required. In particular, a manifold that is directly connected to a separator from an external pipe that supplies reaction gas is called an external manifold. On the other hand, there is a so-called internal manifold having a simpler structure. The internal manifold is composed of a through hole provided in the separator having the gas flow path, and the reaction port can be directly supplied to the gas flow path from the through hole by connecting the inlet / outlet of the gas flow path to the hole. it can.

  The gas diffusion layer 113 mainly has the following three functions. The first function is a function of diffusing the reaction gas in order to uniformly supply the reaction gas from the gas flow path of the separator 116 located outside the gas diffusion layer 113 to the electrode catalyst in the catalyst layer 112. The second function is a function of quickly discharging water generated by the reaction in the catalyst layer 112 to the gas flow path. The third function is a function of conducting electrons necessary for the reaction or generated electrons. That is, the gas diffusion layer 113 is required to have high reaction gas permeability, moisture exhaustability, and electronic conductivity.

  In general, the gas diffusion layer 113 is made of carbon fine powder, a pore-forming material, carbon paper, carbon cloth, or the like and has a porous structure so as to have gas permeability. Is used. Further, in order to provide drainage, water-repellent polymer typified by fluororesin is dispersed in the gas diffusion layer 113, and further, carbon fiber, The gas diffusion layer 113 is also made of an electron conductive material such as metal fiber or carbon fine powder. A water repellent carbon layer composed of a water repellent polymer and carbon powder may be provided on the surface of the gas diffusion layer 113 in contact with the catalyst layer 112.

  Next, the catalyst layer 112 mainly has four functions. The first function is a function of supplying the reaction gas supplied from the gas diffusion layer 113 to the reaction site of the catalyst layer 112, and the second function is hydrogen ions or generation necessary for the reaction on the electrode catalyst. It is a function to conduct the generated hydrogen ions. The third function is a function of conducting electrons necessary for the reaction or the generated electrons, and the fourth function is a function of accelerating the electrode reaction by high catalyst performance and its wide reaction area. That is, the catalyst layer 112 needs high reaction gas permeability, hydrogen ion conductivity, electron conductivity, and catalyst performance.

  In general, as the catalyst layer 112, a catalyst layer having a porous structure and a gas channel is formed using carbon fine powder or a pore former so as to have gas permeability. In order to provide hydrogen ion permeability, a polymer electrolyte is dispersed in the vicinity of the electrode catalyst in the catalyst layer 112 to form a hydrogen ion network. Further, in order to provide electron conductivity, an electron channel is formed by using an electron conductive material such as carbon fine powder or carbon fiber as an electrode catalyst carrier. In order to improve the catalyst performance, a catalyst body in which a very fine particle electrode catalyst having a particle size of several nm is supported on a fine carbon powder is highly dispersed in the catalyst layer 112. ing.

  Here, for the practical application of the polymer electrolyte fuel cell, studies for improving various performances of the catalyst layer 112 are being conducted. For example, Patent Document 1 proposes adjusting the catalyst distribution ratio to the cathode and the anode in the gas concentration ratio in order to increase the catalyst utilization rate in the catalyst layer. Specifically, in the region where the gas concentration is higher on the cathode side than on the anode side, the catalyst distribution rate in the cathode catalyst layer is increased, and conversely in the region where the gas concentration is lower, the catalyst distribution rate in the anode catalyst layer is increased. That is, electrodes having different catalyst distribution ratios in the catalyst layer surface direction have been proposed.

Patent Document 2 also proposes a fuel cell in which the constituent material composition is changed in the catalyst layer surface direction. Specifically, in the cathode catalyst layer, in the vicinity of the oxidant gas outlet, in the cathode catalyst layer, in the vicinity of the oxidant gas outlet, with the intention of suppressing excessive product water retention in the cathode electrode. There has been proposed a method for increasing the amount of catalyst supported over the existing catalyst layer.
JP 7-169471 A JP-A-8-167416

However, the above-described prior art has been proposed with the intention of improving the initial cell characteristics of the fuel cell and reducing the cost from the viewpoint of effective utilization of the catalyst. It has not been sufficiently studied to improve the durability and life characteristics of the assumed membrane electrode assembly and membrane catalyst layer assembly as well as the fuel cell.
Specifically, in Patent Documents 1 and 2, there is no report on a technique for designing a catalyst layer from the viewpoint of improving the durability of the membrane electrode assembly and the membrane catalyst layer assembly, and the lifetime is high and the efficiency is high. There is still room for improvement from the viewpoint of realizing a membrane electrode assembly, a membrane catalyst layer assembly, a fuel cell, and a fuel cell stack.

The present invention has been made in view of the above viewpoints, and even if the fuel cell is repeatedly operated and stopped, the degradation of the polymer electrolyte membrane can be suppressed over a long period of time, and the deterioration of the initial characteristics can be sufficiently prevented. An object of the present invention is to provide a fuel cell having excellent durability.
In addition, the present invention is a fuel having excellent durability that can suppress degradation and degradation of the polymer electrolyte membrane over a long period of time even if the operation and stop of the fuel cell are repeated, and can sufficiently prevent a decrease in initial characteristics. An object of the present invention is to provide a membrane catalyst layer assembly and a membrane electrode assembly capable of easily and reliably realizing a battery.
Further, the present invention is equipped with a plurality of the above fuel cells of the present invention, can suppress degradation and degradation of the polymer electrolyte membrane over a long period of time even if the operation and the stop are repeated, and sufficiently lower the initial characteristics. An object of the present invention is to provide a fuel cell stack having excellent durability that can be prevented.

As a result of intensive studies to achieve the above object, the present inventors have found that the anode catalyst layer and the cathode catalyst layer provided in close contact with the polymer electrolyte membrane greatly affect the durability of the polymer electrolyte membrane. The durability of the membrane-catalyst layer assembly and the durability of the membrane-electrode assembly can be improved by devising the configuration of the catalyst layer to the following configuration, and the present invention Reached.
That is, the present invention relates to a method for producing a membrane / catalyst layer assembly in which an anode catalyst layer is formed on one surface of a polymer electrolyte membrane and a cathode catalyst layer is formed on the other surface. The step of arranging the catalyst layer forming mask with a gap between the mask and the mask, and applying the ink for forming the catalyst layer by the spray method, the anode catalyst layer and the cathode catalyst layer on the surface of the polymer electrolyte membrane And a step of forming at least one of them.

In the membrane / catalyst layer assembly according to the present invention , the mass of the catalyst per unit area of the catalyst layer is directed from the inside to the outside in the periphery of the main surface of at least one of the anode catalyst layer and the cathode catalyst layer. There is a decreasing part that is decreasing. The reduced portion is formed such that the catalyst layer is provided in an island shape and the thickness of the catalyst layer decreases from the inside toward the outside.
As described above, by using the membrane catalyst layer assembly having at least one of the anode catalyst layer and the cathode catalyst layer as described above for the fuel cell, the fuel cell can be operated for a long time even if the fuel cell is repeatedly operated and stopped. It is possible to easily and reliably realize a fuel cell having excellent durability that can suppress degradation and degradation of the molecular electrolyte membrane and can sufficiently prevent deterioration of initial characteristics.
More specifically, since the fuel cell including the membrane-catalyst layer assembly according to the present invention includes the catalyst layer having the reduced portion described above, the polymer electrolyte membrane in the membrane-electrode assembly is decomposed. Deterioration is suppressed, and even if the fuel cell is repeatedly operated and stopped, deterioration of the initial characteristics can be sufficiently prevented over a long period of time, and excellent durability can be obtained.

The clear mechanism for the effect of the present invention the above mentioned is obtained has not been elucidated, the present inventors have presumed as follows.
That is, it has been reported that the deterioration of the membrane electrode assembly and the membrane catalyst layer assembly proceeds mainly in the polymer electrolyte membrane. Specifically, it is reported that the degradation of the polymer electrolyte membrane proceeds specifically in the portion of the polymer electrolyte membrane that is in contact with the peripheral portion of the electrode (for example, S. Grot, Abstract p860, Fuel Cell Seminar Nov. 2003).
When the polymer electrolyte membrane deteriorates, fluorine, which is a component element of the polymer electrolyte membrane, is discharged out of the fuel cell as fluoride ions. Therefore, by measuring the amount of fluoride ions discharged, It is possible to quantify the degree of progress of degradation and degradation of membrane electrode assemblies and membrane catalyst layer assemblies, and to evaluate the durability performance (for example, Wen Liu et. Al., J. New Mater. Electrochem. Syst ., 4 (2001) 227).

  It is presumed that the reaction heat of the electrode reaction that proceeds in the catalyst layer (at least one of the anode catalyst layer and the cathode catalyst layer) has a great influence on the deterioration of the polymer electrolyte membrane in the periphery of the electrode. In the periphery of the catalyst layer, reaction heat is generated in the portion where the catalyst layer exists, and no reaction heat is generated in the portion where the catalyst layer does not exist. Therefore, in the peripheral part of the catalyst layer and the peripheral part of the polymer electrolyte membrane in contact therewith, there are portions where the heat of reaction is generated and portions where the heat of reaction is not generated, or there is a difference in the magnitude of the heat of reaction. As a result, a temperature difference between the regions (particularly, a temperature difference between the regions in a direction in a plane parallel to the main surface) occurs. Since the polymer electrolyte undergoes a change in water content and the like depending on the temperature, it is presumed that mechanical stress is easily applied to the portion of the polymer electrolyte membrane that is in contact with the periphery of the catalyst layer.

  Further, in the periphery of the catalyst layer, in addition to the reaction gas (fuel gas or oxidant gas) that permeates the gas diffusion layer and enters the catalyst layer, the gas flow of the separator does not pass through the gas diffusion layer. There is a reaction gas that enters the catalyst layer from the road around the electrode. Therefore, the electrode reaction is more likely to proceed at the periphery of the catalyst layer than at the center of the catalyst layer, and current concentration is likely to occur. In connection with this, it is guessed that deterioration by the above-mentioned reaction heat is further accelerated in the periphery of the catalyst layer.

The inventors of the present invention provide a polymer electrolyte membrane by causing the mass per unit area of the electrode catalyst constituting the catalyst layer to be reduced in the peripheral portion with respect to the central portion of the catalyst layer. We believe that it will be possible to sufficiently reduce the occurrence of temperature differences between the regions due to the heat of reaction described above, which is considered to be the main cause of deterioration. More specifically, the present inventors have reduced the amount of catalyst in the periphery of the catalyst layer (mass per unit area of the catalyst layer of the electrode catalyst), thereby reducing excess reaction heat that contributes to the deterioration of the polymer electrolyte membrane. Since the generation is sufficiently reduced, the temperature difference between the local areas in the periphery of the catalyst layer (especially the temperature difference between the local areas in the direction parallel to the main surface) should be sufficiently reduced. It is considered that the mechanical stress described above can be sufficiently reduced on the periphery of the polymer electrolyte.
From the above, high efficiency is achieved by constructing a catalyst layer structure in which the amount of electrode catalyst (mass per unit area of the electrode catalyst) is reduced as described above with respect to the center of the catalyst layer. As a result, it is possible to obtain a fuel cell that can simultaneously achieve excellent life characteristics, that is, high durability.

  Here, in the present invention, “the mass per unit area of the catalyst layer of the electrode catalyst decreases from the inner side toward the outer side in the periphery of the main surface of at least one of the anode catalyst layer and the cathode catalyst layer. The state where there is a reduced portion that is present is a state in which the corresponding catalyst layer is viewed in a cross section cut in a plane substantially parallel to the normal direction of the main surface of the catalyst layer, and the inner side ( That is, it shows a state in which the mass per unit area of the electrode catalyst is generally reduced from the center side of the main surface of the catalyst layer to the outside.

The state in which decreased the schematic, when viewed above SL cross-section, toward the inside to the outside, situations that der mass per catalyst layer unit area of the electrode catalyst is reduced to discontinuous . Specifically, when the catalyst layer is viewed along the cross section, it is in a state (island shape) where the catalyst layer is not locally seen from the inside to the outside (see the state shown in FIG. 6 described later).

In the present invention, “the peripheral portion of the main surface of at least one of the anode catalyst layer and the cathode catalyst layer” means “gas diffusion from the gas flow path of the separator” of the corresponding catalyst layer. This refers to the “peripheral part where the reactant gas that enters the periphery of the electrode without passing through the layer is exposed”.
Further, in the present invention, the “peripheral portion” of the main surface of the catalyst layer having the reduced portion and the portion other than the peripheral portion (hereinafter referred to as “center portion”) are gasses of the separator disposed on the catalyst layer side. It is more preferable that the portion is positioned at the following position with respect to the flow path. That is, as will be described later with reference to FIG. 1, in the present invention, the catalyst layer having a reduced portion is on the outermost side of the gas flow path formed in the separator disposed on the catalyst layer side. With reference to the outer end of the gas flow path (that is, the gas flow path that is on the outermost side as viewed from the center of the main surface of the separator), the inner side as viewed from the outer end (that is, the center side of the main surface of the catalyst layer) It is preferably divided into a “central portion” located at the outer edge and a “peripheral portion” located on the outer side (that is, the outer side as seen from the center of the main surface of the catalyst layer) from the outer end.
By positioning the peripheral portion as described above, the central portion of the main surface of the catalyst layer (the portion where the electrode reaction mainly proceeds) is brought into contact with the gas flow path of the separator in the catalyst layer having the reduced portion ( A portion having a constant mass per unit area of the catalyst layer of the electrode catalyst can be disposed.

  In this case, it is easier to form a catalyst layer having a constant mass per unit area of the electrode catalyst when forming the central portion (portion in contact with the gas flow path of the separator) of the catalyst layer. A catalyst layer can be formed. Furthermore, from the viewpoint of simplifying the production process, it is preferable to prepare the catalyst layer with only one type of catalyst layer forming ink containing the constituent material of the catalyst layer. In this case, one type of catalyst layer is formed. Even when the catalyst layer is formed using the ink for a catalyst, it is possible to easily form a catalyst layer having a constant mass per unit area of the electrode catalyst and a constant thickness of the central portion. If the thickness of the central portion of the catalyst layer can be made constant, the contact resistance with the separator can be easily reduced. Further, if the thickness of the central portion of the catalyst layer can be made constant, it is easy to reduce variations in fastening pressure applied to the surface of the central portion of the catalyst layer. Therefore, it is possible to prevent a large fastening pressure from being applied to a specific portion of the polymer electrolyte membrane, and it becomes easy to obtain good durability.

  Reaction heat, which is a deterioration factor of the polymer electrolyte membrane, is generated in both the anode and cathode catalyst layers. Therefore, the durability of the polymer electrolyte membrane is improved by applying the catalyst layer structure in which the mass per unit area of the electrode catalyst of the electrode catalyst is changed in the catalyst layer surface direction to at least one of the anode and cathode catalyst layers. . Furthermore, if the catalyst layer structure in which the mass per unit area of the electrode catalyst is changed in the catalyst layer surface direction is applied to both the anode and cathode catalyst layers, the durability can be improved more effectively. it is conceivable that.

According to the membrane / catalyst layer assembly of the present invention, at least one of the anode catalyst layer and the cathode catalyst layer is configured as described above, so that the polymer can be maintained over a long period of time even when the fuel cell is repeatedly activated and stopped. Degradation and degradation of the electrolyte membrane can be suppressed, and deterioration of the initial characteristics can be sufficiently prevented, and a fuel cell having excellent durability can be obtained easily and reliably.

Et al is, the present invention is a method for producing a membrane catalyst layer assembly for forming a cathode catalyst layer on the anode catalyst layer and the other surface on one surface of the polymer electrolyte membrane, the support and the catalyst layer formed A step of disposing a catalyst layer forming mask on the surface of the support with a gap provided between the mask and a catalyst layer forming ink is applied by a spray method, and an anode catalyst layer and a cathode catalyst are formed on the surface of the support. A method for producing a membrane / catalyst layer assembly comprising a step of forming at least one of the layers and a step of bonding the obtained catalyst layer to the surface of a polymer electrolyte membrane is provided.

According to the present invention, even if the fuel cell is repeatedly operated and stopped, the degradation of the polymer electrolyte membrane can be suppressed over a long period of time, and the deterioration of the initial characteristics can be sufficiently prevented, and the battery is sufficiently stable over a long period of time. A fuel cell exhibiting performance and having excellent durability can be obtained.
In addition, according to the present invention, even when the operation and stop of the fuel cell are repeated, the degradation and degradation of the polymer electrolyte membrane can be suppressed over a long period, and the initial characteristics can be sufficiently prevented from being deteriorated. It is possible to obtain a membrane catalyst layer assembly and a membrane electrode assembly that can surely realize the fuel cell having the fuel cell.
Furthermore, according to the present invention, the upper Ki燃 charge batteries has a plurality mounting, it is possible to suppress decomposition deterioration of the polymer electrolyte membrane for a long time even after repeated operation and stopping, and the decrease in initial characteristics A fuel cell stack having excellent durability that can be sufficiently prevented may be configured.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or an equivalent part, and the overlapping description may be abbreviate | omitted.
FIG. 1 is a schematic cross-sectional view showing an example of a basic configuration of a preferred embodiment of a fuel cell (unit cell) including a membrane catalyst layer assembly according to the present invention. 2 is a schematic cross-sectional view showing an example of a basic configuration of a membrane-electrode assembly (MEA) of the present embodiment mounted on the fuel cell 1 shown in FIG. 1, and FIG. It is a schematic sectional drawing which shows an example of the membrane catalyst layer assembly (CCM: Catalyst-coated membrane) of this embodiment which comprises the membrane electrode assembly 10 shown in FIG.

As shown in FIG. 3, the membrane / catalyst layer assembly 20 of the present embodiment mainly includes a substantially rectangular cathode catalyst layer 12a, a substantially rectangular anode catalyst layer 12b, and the cathode catalyst layer 12a and the anode catalyst layer 12b. And a substantially rectangular polymer electrolyte membrane 11 disposed between the two.
The polymer electrolyte membrane 11 is not particularly limited, and a polymer electrolyte membrane mounted on a normal solid polymer fuel cell can be used. For example, a polymer electrolyte membrane made of perfluorocarbon sulfonic acid (for example, Nafion (trade name) manufactured by Du Pont, USA, Aciplex (trade name) manufactured by Asahi Kasei Co., Ltd., GSII manufactured by Japan Gore-Tex Co., Ltd. (product) Name) etc. can be used.

The polymer electrolyte membrane 11 is a solid electrolyte and has hydrogen ion conductivity that selectively transports hydrogen ions. In the membrane electrode assembly 20 during power generation, hydrogen ions generated in the anode catalyst layer 12b move in the polymer electrolyte membrane 11 toward the cathode catalyst layer 12a.
Moreover, as a polymer electrolyte which comprises the polymer electrolyte membrane 11, what has a sulfonic acid group, a carboxylic acid group, a phosphonic acid group, and a sulfonimide group as a cation exchange group is mentioned preferably. From the viewpoint of hydrogen ion conductivity, those having a sulfonic acid group are particularly preferred. The polymer electrolyte having a sulfonic acid group preferably has an ion exchange capacity of 0.5 to 1.5 meq / g dry resin. When the ion exchange capacity of the polymer electrolyte is 0.5 meq / g dry resin or more, it is preferable because the resistance value of the catalyst layer is easily kept low during power generation, and the ion exchange capacity is 1.5 meq / g dry resin or less. The polymer electrolyte membrane 11 is preferable because the moisture content in the catalyst layers (cathode catalyst layer 12a and anode catalyst layer 12b) can be easily secured sufficiently while keeping the moisture content of the polymer electrolyte membrane 11 appropriately. From the same viewpoint as described above, the ion exchange capacity is particularly preferably 0.8 to 1.2 meq / g dry resin.

As the polymer _{electrolyte, CF 2 = CF- (OCF 2} CFX) m -O p - (CF 2) a perfluorovinyl compound represented by _n -SO ₃ H (m is an integer of 0 to 3 , N represents an integer of 1 to 12, p represents 0 or 1, X represents a fluorine atom or a trifluoromethyl group), and tetrafluoroethylene represented by CF ₂ = CF ₂ A perfluorocarbon copolymer containing a polymerization unit based on The fluorocarbon polymer may contain, for example, an etheric oxygen atom.

Preferable examples of the perfluorovinyl compound include compounds represented by the following formulas (1) to (3). However, in the following formula, q is an integer of 1 to 8, r is an integer of 1 to 8, and t is an integer of 1 to 3.
_{CF 2 = CFO (CF 2)} q -SO 3 H ··· (1)
_{CF 2 = CFOCF 2 CF (CF} 3) O (CF 2) r -SO 3 H ··· (2)
_{CF 2 = CF (OCF 2 CF} (CF 3)) t O (CF 2) 2 -SO 3 ··· (3)

The polymer electrolyte membrane 11 may be composed of one or a plurality of polymer electrolytes, but may include a reinforcing body (filler) inside. However, the arrangement state (for example, the degree of density or regularity) of the reinforcing body in the polymer electrolyte membrane 11 is not particularly limited.
The material constituting such a reinforcing body is not particularly limited, and examples thereof include polytetrafluoroethylene, polyfluoroalkoxyethylene, and polyphenyl sulfide. The shape of the reinforcing body is not particularly limited, and examples thereof include a porous reinforcing body, a fibril-like reinforcing body, and fibril-like, fibrous and spherical reinforcing body particles. Fibril-like fibers are fibers in which fibrils (small fibers) existing on the surface are fluffed (fibrillated), and there are fine air grooves (holes) between each fibril. It refers to the fibers that are formed. For example, all cellulosic fibers are bundles of many fibrils, and there are fine air grooves (holes) between the fibrils.

The cathode catalyst layer 12a and the anode catalyst layer 12b are mainly composed of a catalyst-supported carbon obtained by supporting an electrode catalyst (for example, a platinum-based metal catalyst) on carbon powder, and a polymer electrolyte having hydrogen ion conductivity. Has been.
As the polymer electrolyte having hydrogen ion conductivity contained in the cathode catalyst layer 12a and the anode catalyst layer 12b and adhering to the catalyst-supporting carbon, the polymer electrolyte constituting the polymer electrolyte membrane 11 may be used. The polymer electrolyte constituting the cathode catalyst layer 12a, the anode catalyst layer 12b, and the polymer electrolyte membrane 11 may be the same type or different types. For example, commercially available products such as Nafion (trade name) manufactured by Du Pont, USA, Flemion (trade name) manufactured by Asahi Glass Co., Ltd., and Aciplex (trade name) manufactured by Asahi Kasei Co., Ltd. may be used.

Here, in the membrane catalyst layer assembly 20 of the present embodiment, as described above, the cathode catalyst layer 12a and the anode catalyst layer 12b include carbon powder and catalyst-supported carbon containing an electrode catalyst supported on the carbon powder, And a polymer electrolyte having hydrogen ion conductivity attached to the catalyst-supporting carbon. As described above, the mass per unit area of the catalyst layer of the electrode catalyst is approximately parallel to the main surface of the polymer electrolyte membrane 11 at the periphery of the cathode catalyst layer 12a and the periphery of the anode catalyst layer 12b. In other directions, there is a portion (decreasing portion) that is generally decreasing from the inside toward the outside (ie, the portions indicated by 12a ₁ , 12a ₂ , 12b _1, and 12b ₂ in FIG. 3). Existing).

A description will be given by taking the cathode catalyst layer 12a side as a representative in the membrane catalyst layer assembly 20 of the present embodiment. As shown in FIG. 1, the gas formed in the plate-like cathode-side separator 16 a when viewed in a cross section cut along a plane substantially parallel to the normal direction of the main surface of the cathode catalyst layer 12 a of the fuel cell 1. An outer end (portion P indicated by a dotted line in FIG. 1) of the outermost gas channel 17a1 of the channel 17a (that is, the outermost gas channel 17a1 as viewed from the center of the main surface of the separator 16). “Central part Z” located on the inner side (that is, the center side of the main surface of the cathode catalyst layer 12a) as viewed from the part P, and outer side (that is, the main part of the cathode catalyst layer 12a) as viewed from the part P. And “peripheral portion Y” located on the outer side as viewed from the center of the surface.
The anode catalyst layer 12b side has the same configuration as the cathode catalyst layer 12a side. Further, a portion Q indicated by a dotted line in FIG. 1 indicates the positions of the outer ends of the cathode gas diffusion layer 13a and the anode gas diffusion layer 13b.
That is, in the present embodiment, the outer ends Q of the cathode gas diffusion layer 13 a and the anode gas diffusion layer 13 b are the outer ends of the gas flow channels 17 a 1 positioned on the outermost side of the gas flow channels 17 formed in the separator 16. The peripheral portion Y is located between the portion Q and the portion P, located outside the (portion P).

In the membrane catalyst layer assembly 20, as shown in FIG. 3, the “peripheral thickness” of the cathode catalyst layer 12a and the “peripheral thickness” of the anode catalyst layer 12b are directed from the inside to the outside, respectively. Is decreasing. As a result, a “reduced portion where the mass per unit area of the catalyst layer of the electrode catalyst is generally decreased from the inside toward the outside” is formed in the periphery of the cathode catalyst layer 12a and the periphery of the anode catalyst layer 12b. Has been.
As described above, the method of reducing the thickness when the thickness of the periphery of each catalyst layer (the periphery of the cathode catalyst layer 12a and the periphery of the anode catalyst layer 12b) is decreased from the inside toward the outside is shown in FIG. As shown in FIG. 3, the thickness of the catalyst layer may be monotonously decreased from the inside to the outside (the mass per unit area of the electrode catalyst is monotonously reduced) (as shown in FIG. 3). It may decrease in a substantially linear manner or in a substantially curvilinear manner).

  In FIG. 3, the distance from the outer end (part P) of the central portion Z of the cathode gas diffusion layer 12a to the outer end of the reduced portion (distance in a direction substantially perpendicular to one side of the substantially rectangular shape). ) S coincides with the distance from the portion P to the portion Q, but the distance S of the decreasing portion starting from the portion P does not necessarily coincide with the distance from the portion P to the portion Q, and is short. Also good. That is, the distance S may vary from the portion P to the portion Q starting from the portion P along the periphery of the main surface of the cathode gas diffusion layer 12a.

About the arrangement | positioning state on the main surface of the reduced part of the peripheral part Y, it is preferable that it is the state which satisfy | fills the following conditions. That is, as shown in FIG. 4, the four sides of the peripheral portion Y of the main surface of the substantially rectangular cathode catalyst layer 12a are each divided into four equal parts to obtain 16 pieces obtained by dividing the peripheral portion Y into 16 equal parts. In each of the unit peripheral parts Y _{1 to} Y ₁₆ , the longest distance among the distances S from the outer end (part P) of the central part Z of the cathode gas diffusion layer 12a to the outer end of the reduced part is 200. It is preferable that the shortest distance among the distances S to the outer end of the reduced portion is 0 to 200 μm.
4 is a schematic front view of the membrane catalyst layer assembly 20 as viewed from the direction of the arrow R in FIG. FIG. 4 is also a diagram for explaining an example of a suitable method for verifying the presence or absence of a decreasing portion in which the catalyst loading amount decreases from the inside toward the outside in the peripheral portion of the catalyst layer.

  In addition to the method shown in FIG. 3, for example, as shown in FIGS. 5 to 7, each method for reducing the thickness in the case where the thickness of the peripheral portion of each catalyst layer is reduced from the inside toward the outside is shown in FIGS. If the thickness of the catalyst layer as a whole (the mass per unit area of the catalyst layer of the electrode catalyst decreases as a whole) from the inside to the outside of the periphery of the catalyst layer, the thickness of the cathode catalyst layer 12a and the anode You may make it reduce so that the part in which the thickness of the catalyst layer 12b is increasing partly exists may be included.

Hereinafter, it demonstrates concretely using FIGS. FIG. 5 is an enlarged cross-sectional view of a main part in which a main part of the peripheral part 12a ₁ (Y) of the cathode catalyst layer 12a is enlarged. As shown in FIG. 5, in the peripheral portion 12a ₁ (Y) of the cathode catalyst layer 12a, the thickness of the cathode catalyst layer 12a is roughly as shown by an arrow X from the inside to the outside of the cathode catalyst layer 12a. As long as it has decreased. However, as long as the effects of the present invention can be obtained, the cathode catalyst layer 12a has a thickness that is partially outside (indicated by arrow α) and outside (indicated by arrow β). The state where the thickness of 12a is increasing may be included. Further, within the range where the effects of the present invention can be obtained, if the thickness of the cathode catalyst layer 12a is substantially reduced, it is partially outside (indicated by the arrow β) outside (indicated by the arrow α). The thickness of the cathode catalyst layer 12a of the portion shown in FIG. The same applies to the peripheral portion 12a ₂ of the cathode catalyst layer 12a and the peripheral portions 12b ₁ and 12b ₂ of the anode catalyst layer 12b. However, from the viewpoint of simplifying the manufacturing process, a monotonically decreasing state is desirable.

FIG. 6 is an enlarged cross-sectional view of a main part in which a main part of a modified example of the peripheral part 12a ₁ (Y) of the cathode catalyst layer 12a is enlarged. As shown in FIG. 6, when the peripheral portion 12a ₁ (Y) of the cathode catalyst layer 12a is viewed in a cross section cut along a plane substantially parallel to the normal direction of the main surface of the cathode catalyst layer 12a, the catalyst layer is As shown by an arrow X, a state may be formed in which the catalyst layer is not locally seen from the inside to the outside. Thus, the thickness of the peripheral portion 12a of the cathode catalyst layer 12a ₁ (Y) may form a state that schematically reduced as a whole. The same applies to the peripheral portion 12a ₂ of the cathode catalyst layer 12a and the peripheral portions 12b ₁ and 12b ₂ of the anode catalyst layer 12b.

FIG. 7 is an enlarged cross-sectional view of a main part in which a main part of another modification of the peripheral part 12a ₁ of the cathode catalyst layer 12a is enlarged. As shown in FIG. 7, when the peripheral portion 12a ₁ (Y) of the cathode catalyst layer 12a is viewed in a cross section cut along a plane substantially parallel to the normal direction of the main surface of the cathode catalyst layer 12a, the peripheral portion 12a ₁ While the thickness of (Y) and the thickness of the central portion Z are substantially matched, a state in which the catalyst density in the peripheral portion 12a ₁ (Y) is substantially reduced as seen from the inside to the outside as indicated by an arrow X is formed. Also good. The same applies to the peripheral portion 12a ₂ of the cathode catalyst layer 12a and the peripheral portions 12b ₁ and 12b ₂ of the anode catalyst layer 12b.

  In the present embodiment, the mass per unit area of the carbon powder that is the electrode catalyst carrier is decreased in proportion to the electrode catalyst mass from the inside toward the outside in the peripheral part of the catalyst layer. It does not matter if it does not decrease. Further, the mass per unit area of the polymer electrolyte present in the catalyst layer is not decreased even if it decreases in proportion to the electrode catalyst mass from the inside to the outside in the peripheral part of the catalyst layer. It doesn't matter. From the viewpoint of hydrogen ion conduction and flooding, an increase / decrease proportional to the mass of the catalyst-supporting carbon is preferable.

  The carbon powder (conductive carbon particles) that is a carrier in the cathode catalyst layer 12a and the anode catalyst layer 12b is preferably a carbon material having conductive pores, such as carbon black, activated carbon, carbon fiber, and the like. Carbon tubes or the like can be used. Examples of carbon black include channel black, furnace black, thermal black, and acetylene black. Activated carbon can be obtained by carbonizing and activating materials containing various carbon atoms.

The specific surface area of the carbon powder is preferably 50 to 1500 m ² / g. A specific surface area of 50 m ² / g or more is preferable because it is easy to increase the loading ratio of the electrode catalyst, and the output characteristics of the obtained cathode catalyst layer 12a and anode catalyst layer 12b can be more sufficiently secured. Is 1500 m ² / g or less, sufficiently large pores can be secured more easily and coating with a polymer electrolyte becomes easier, and the output characteristics of the cathode catalyst layer 12a and the anode catalyst layer 12b are improved. It is preferable because it can be sufficiently secured. From the same viewpoint as described above, the specific surface area is particularly preferably 200 to 900 m ² / g.

As an electrode catalyst used for the cathode catalyst layer 12a and the anode catalyst layer 12b, it is preferable to use platinum or a platinum alloy. Platinum alloys include platinum group metals other than platinum (ruthenium, rhodium, palladium, osmium, iridium), iron, titanium, gold, silver, chromium, manganese, molybdenum, tungsten, aluminum, silicon, rhenium, zinc, and tin. An alloy of at least one metal selected from the group consisting of platinum and platinum is preferable. The platinum alloy may contain an intermetallic compound of platinum and the metal.
Furthermore, an electrode catalyst mixture obtained by mixing an electrode catalyst made of platinum and an electrode catalyst made of a platinum alloy may be used. Even if the same electrode catalyst is used for the cathode catalyst layer 12a and the anode catalyst layer 12b, different electrode catalysts may be used. It may be used.

The primary particle diameter of the electrode catalyst is preferably 1 to 20 nm in order to make the cathode catalyst layer 12a and the anode catalyst layer 12b highly active, and in particular, a large surface area is secured to increase the reaction activity. From the viewpoint of being possible, it is preferably 2 to 10 nm.
The catalyst loading rate of the catalyst-carrying carbon (ratio of the mass of the supported electrode catalyst to the total mass of the catalyst-carrying carbon) may be 20 to 80% by mass, and particularly preferably 40 to 60% by mass. . Within this range, high battery output can be obtained. As described above, when the catalyst loading is 20% by mass or more, sufficient battery output can be obtained more reliably, and when it is 80% by mass or less, the electrode catalyst particles are supported on the carbon powder with good dispersibility. And the effective catalyst area can be further increased.

  As the polymer electrolyte having hydrogen ion conductivity contained in the cathode catalyst layer 12a and the anode catalyst layer 12b and adhering to the catalyst-supporting carbon, a polymer electrolyte constituting the polymer electrolyte membrane 11 may be used. The polymer electrolyte constituting the cathode catalyst layer 12a, the anode catalyst layer 12b, and the polymer electrolyte membrane 11 may be the same type or different types. For example, commercially available products such as Nafion (trade name) manufactured by Du Pont, USA, Flemion (trade name) manufactured by Asahi Glass Co., Ltd., and Aciplex (trade name) manufactured by Asahi Kasei Co., Ltd. may be used.

The polymer electrolyte is preferably added in proportion to the mass of the catalyst-carrying carbon constituting the catalyst layer in order to cover the catalyst-carrying carbon particles and secure a three-dimensional hydrogen ion conduction path.
Specifically, the mass of the polymer electrolyte constituting the catalyst layer is preferably 0.2 times or more and 2.0 times or less with respect to the mass of the catalyst-supporting carbon. Within this range, high battery output can be obtained. As described above, if the mass of the polymer electrolyte is 0.2 times or more, sufficient hydrogen ion conductivity is easily secured, and if it is 2.0 times or less, flooding can be avoided more easily. High battery output can be realized.

  In the cathode catalyst layer 12a and the anode catalyst layer 12b of this embodiment, it is sufficient that the polymer electrolyte is partially attached to the surface of the catalyst-carrying carbon particles, that is, at least a part of the catalyst-carrying carbon particles. What is necessary is just to coat | cover and it does not necessarily need to coat | cover the whole catalyst carrying | support carbon particle. Of course, the polymer electrolyte may cover the entire surface of the catalyst-supporting carbon particles.

  Next, as shown in FIG. 2, the membrane electrode assembly 10 according to the present embodiment uses, for example, carbon paper that has been subjected to water repellent treatment on the outer sides of the cathode catalyst layer 12 a and the anode catalyst layer 12 b. In addition, a gas diffusion layer 13 having both electron conductivity is formed. A cathode 14 a is configured by a combination of the cathode catalyst layer 12 a and the gas diffusion layer 13, and an anode 14 b is configured by a combination of the anode catalyst layer 12 b and the gas diffusion layer 13.

  As the gas diffusion layer 13, a conductive material having a porous structure produced using carbon fine powder having a developed structure structure, a pore former, carbon paper, carbon cloth, or the like in order to provide gas permeability. A substrate can be used. In order to provide drainage, a water repellent polymer such as a fluororesin may be dispersed in the gas diffusion layer 13. In order to impart electron conductivity, the gas diffusion layer 13 may be made of an electron conductive material such as carbon fiber, metal fiber, or carbon fine powder. Furthermore, a water repellent carbon layer composed of a water repellent polymer and carbon powder may be provided on the surface of the gas diffusion layer 13 that is in contact with the cathode catalyst layer 12a or the anode catalyst layer 12b. The same gas diffusion layer or different gas diffusion layers may be used on the cathode side and the anode side.

  As shown in FIG. 1, the fuel cell 1 according to the present embodiment includes a membrane electrode assembly 10, a gasket 15, and a pair of separators 16 (an anode side separator 16b and a cathode side separator 16a). The gasket 15 is disposed around the cathode 14a and the anode 14b with the polymer electrolyte membrane 11 interposed therebetween in order to prevent leakage and mixing of the supplied fuel gas and oxidant gas to the outside. The gasket 15 is integrated with the cathode 14a or the anode 14b and the polymer electrolyte membrane 11 in advance, and a combination of these may be referred to as a membrane electrode assembly 10.

  A pair of separators 16 (an anode side separator 16b and a cathode side separator 16a) for mechanically fixing the membrane electrode assembly 10 are disposed outside the membrane electrode assembly 10. In the portion of the separator 16 that contacts the membrane electrode assembly 10, an oxidant gas is supplied to the cathode 14 a, a fuel gas is supplied to the anode 14 b, and an electrode reaction product and a gas containing an unreacted reaction gas are supplied to the reaction field. Gas passages 17 (a gas passage 17b formed in the anode-side separator 16b and a gas passage 17b formed in the cathode-side separator 16a) for carrying away from the cathode 14a and the anode 14b are formed. The gas flow path 17 can be provided separately from the separator 16, but in FIG. 1, the gas flow path 17 is formed by providing a groove on the surface of the separator 16. Further, the side of the separator 16 opposite to the membrane electrode assembly 10 has a configuration in which a coolant channel 18 is formed by providing a groove by cutting.

Thus, the membrane electrode assembly 10 is fixed by the pair of separators 16, the fuel gas is supplied to the gas flow path 17b of one anode side separator 16b, and the oxidant is supplied to the gas flow path 17a of the other cathode side separator 16a. By supplying gas, an electromotive force of about 0.7 to 0.8 V can be generated in one fuel cell 1 when a practical current density of several tens to several hundred mA / cm ² is applied. However, in general, when a polymer electrolyte fuel cell is used as a power source, a voltage of several volts to several hundred volts is required. Therefore, in actuality, the required number of fuel cells 1 are connected in series. It is used as a fuel cell stack (FIG. 12 described later).

  In order to supply the reaction gas to the gas channel 17, the piping for supplying the reaction gas is branched into a number corresponding to the number of separators 16 to be used, and the branch destinations are directly connected to the gas channel 17 on the separator 16. However, in the present invention, either an external manifold or an internal manifold can be employed.

  Here, FIG. 8 is a front view when the main surface of the anode separator 16b of the fuel cell 1 shown in FIG. 1 is viewed from the cooling water flow path 18 side, and FIG. 9 is the fuel cell shown in FIG. It is a front view at the time of seeing the main surface of 1 anode side separator 16a from the gas channel 17b side. FIG. 10 is a front view when the main surface of the cathode separator 16a of the fuel cell 1 shown in FIG. 1 is viewed from the gas flow path 17a side, and FIG. 11 is the fuel cell 1 shown in FIG. It is a front view at the time of seeing the main surface of the cathode side separator 16a from the cooling water flow path 18 side.

  Since the voltage value that can be output by one fuel cell 1 shown in FIG. 1 is limited (theoretically, when hydrogen gas is used as the reducing agent and oxygen is used as the oxidizing agent, about 1.23 V), it is desirable depending on the use environment. The fuel cell 1 is used as a single cell constituting the fuel cell stack 30 shown in FIG. In particular, in the case of the fuel cell stack 30 shown in FIG. 12, all the fuel cells 1 constituting this are the fuel cells 1 shown in FIG. FIG. 12 is a schematic cross-sectional view showing a configuration of one embodiment of a fuel cell stack configured by stacking a plurality of fuel cells 1 of the present embodiment shown in FIG.

  As shown in FIG. 12, the fuel cell stack 30 includes a plurality of membrane electrode assemblies 10 that are electrically stacked in series by interposing an anode side separator 16b and a cathode side separator 16a between the plurality of membrane electrode assemblies 10. Obtained. In this case, in order to configure the fuel cell stack 30, a manifold for further branching the reaction gas supplied to the fuel cell stack 30 through an external gas line (not shown) and supplying it to each membrane electrode assembly 10. , A manifold for collectively discharging the gas discharged from each membrane electrode assembly 10 to the outside of the fuel cell stack 30, and cooling water supplied to the fuel cell stack 30 through an external cooling water line (not shown). A manifold for branching to the required number and supplying to at least one of the anode side separator 16b and the cathode side separator 16a is required.

  Therefore, as shown in FIGS. 8 to 11, the anode separator 16b and the cathode separator 16a are provided with a fuel gas supply manifold hole 24, a fuel gas discharge manifold hole 25, a cooling water supply manifold hole 26, and a cooling water. A discharge manifold hole 27, an oxidant gas supply manifold hole 28, and an oxidant gas discharge manifold hole 29 are provided.

  In the anode separator 16 b of the fuel cell 1, one end of the cooling water passage 18 is connected to the cooling water supply manifold hole 26 and the other end is connected to the cooling water discharge manifold hole 27. Further, in the anode separator 16 b of the fuel cell 1, one end of the gas flow path 17 b is connected to the fuel gas supply manifold hole 24 and the other end is connected to the fuel gas discharge manifold hole 25. In the cathode separator 16 a of the fuel cell 1, one end of the cooling water flow path 18 is connected to the cooling water supply manifold hole 26 and the other end is connected to the cooling water discharge manifold hole 27. Further, in the cathode side separator 16 a of the fuel cell 1, one end of the gas flow path 17 a is connected to the oxidant gas supply manifold hole 28 and the other end is connected to the oxidant gas discharge manifold hole 29. That is, the fuel cell 10 of the present embodiment has a so-called “internal manifold type” configuration having a manifold in the separator.

  In the anode side separator 16b shown in FIG. 8, the cooling water flow path 18 has a serpentine structure in order to effectively use the main surface (substantially rectangular main surface) of the anode side separator 16b having a limited size. . More specifically, the cooling water flow path 18 is in the horizontal direction (in the anode side separator 16b of FIG. 8, substantially parallel to the side of the portion where the fuel gas supply manifold hole 24 and the oxidant gas supply manifold hole 28 are provided. 13 straight portions 77a (long flow paths) extending in the same direction) and 12 turn portions 77b (short flow paths) connecting the ends of the adjacent straight portions from the upstream side to the downstream side.

  Further, in the anode side separator 16b shown in FIG. 9, the gas flow path 17b also has a serpentine structure in order to effectively use the main surface of the anode side separator 16b having a limited size. More specifically, the gas flow path 17b is substantially parallel to the side in the horizontal direction (on the side of the anode side separator 16b in FIG. 9 where the oxidant gas supply manifold hole 28 and the fuel gas supply manifold hole 24 are provided). 11 straight portions L1 (long flow paths) extending in the same direction) and 10 turn portions S1 (short flow paths) connecting the ends of the adjacent straight portions from the upstream side to the downstream side. .

  Furthermore, as shown in FIG. 10, the gas flow path 17a in the cathode side separator 16a also has a serpentine structure. That is, the gas flow path 17a is in the horizontal direction (a direction substantially parallel to the side of the portion where the oxidant gas supply manifold hole 28 and the fuel gas supply manifold hole 24 are provided in the cathode side separator 16a in FIG. 10). 11 straight portions L2 (long flow paths) extending in the direction of 10 and 10 turn portions S2 (short flow paths) connecting the ends of the adjacent straight portions from the upstream side to the downstream side.

  Furthermore, as shown in FIG. 11, the cooling water flow path 18 in the cathode side separator 16a also has a serpentine structure. That is, the cooling water flow path 18 is in the horizontal direction (a direction substantially parallel to the side of the portion where the fuel gas supply manifold hole 24 and the oxidant gas supply manifold hole 28 are provided in the cathode separator 16a of FIG. 11). 13 straight portions 77a (long flow paths) extending in the direction of 12 and 12 turn portions 77b (short flow paths) connecting the ends of the adjacent straight portions from the upstream side to the downstream side.

  As shown in FIG. 12, in the fuel cell stack 30 of the present embodiment, a plurality of fuel gas supply manifold holes 24 of the anode side separator 16b and the cathode side separator 16a of the fuel cell 1 constituting the fuel cell stack 30 are continuously stacked. In this state, a fuel gas supply manifold (not shown) is formed. Further, in the fuel cell stack 30, a plurality of fuel gas discharge manifold holes 25 of the anode-side separator 16b and the cathode-side separator 16a of the fuel cell 1 constituting the fuel cell stack 30 are combined in a continuously stacked state to form fuel gas. A discharge manifold (not shown) is formed. Further, in the fuel cell stack 30, the above-described fuel gas is also applied to the cooling water supply manifold hole 26, the cooling water discharge manifold hole 27, the oxidant gas supply manifold hole 28, and the oxidant gas discharge manifold hole 29. Similar to the supply manifold, a plurality of manifold holes are combined in a continuously stacked state to form a manifold (not shown).

Next, a method for manufacturing the fuel cell 1 of the present embodiment will be described.
The cathode catalyst layer 12a and the anode catalyst layer 12b in this embodiment can be formed using a plurality of catalyst layer forming inks. The dispersion medium used to prepare the ink for forming the catalyst layer may be a polymer electrolyte that can be dissolved or dispersible (part of the polymer electrolyte is dissolved and the other part is dispersed without being dissolved) It is preferable to use a liquid containing an alcohol. The dispersion medium preferably contains at least one of water, methanol, ethanol, propanol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol and tert-butyl alcohol. These water and alcohol may be used alone or in combination of two or more. The alcohol is particularly preferably a straight chain having one OH group in the molecule, and ethanol is particularly preferable. This alcohol includes those having an ether bond such as ethylene glycol monomethyl ether.

  Further, the composition of the ink for forming the catalyst layer may be appropriately adjusted according to the configuration of the cathode catalyst layer 12a or the anode catalyst layer 12b, but the solid content concentration is preferably 0.1 to 20% by mass. When the solid content concentration is 0.1% by mass or more, a catalyst layer having a predetermined thickness can be obtained by spraying or applying a smaller number of times when the catalyst layer is produced by spraying or applying the catalyst layer forming ink. Production efficiency. Moreover, when the solid content concentration is 20% by mass or less, the viscosity of the mixed solution becomes appropriate, and a uniform catalyst layer is obtained. The solid content concentration is particularly preferably 1 to 10% by mass.

  The ink for forming the catalyst layer (the ink for forming the cathode catalyst layer 12a and the ink for forming the anode catalyst layer 12b) can be prepared based on a conventionally known method. Specifically, a method using a stirrer such as a homogenizer or a homomixer, a method using high-speed rotation such as using a high-speed rotating jet flow method, or a high-pressure emulsifying apparatus or the like is used to push the dispersion from a narrow part. The method of giving a shearing force to a dispersion liquid by taking out is mentioned.

  When the cathode catalyst layer 12a and the anode catalyst layer 12b are formed using the catalyst layer forming ink, the indirect formation method is indirectly applied to the polymer electrolyte membrane 11 even if the direct coating method is used. Any of the application methods can be employed. Examples of the coating method include a screen printing method, a die coating method, a spray method, and an ink jet method. As an indirect coating method, for example, a cathode catalyst layer 12a and an anode catalyst layer 12b are formed by the above-described method on a support made of polypropylene or polyethylene terephthalate, and then formed on the polymer electrolyte membrane 11 by thermal transfer. Is mentioned. When the membrane electrode assembly 10 of the present embodiment shown in FIG. 6 is obtained, the cathode catalyst layer 12a and the anode catalyst layer 12b are formed on the gas diffusion layer 13 and then joined to the polymer electrolyte membrane 11. It doesn't matter.

  As an example of this embodiment, the thickness of the peripheral portion of each catalyst layer is reduced by decreasing the coating amount of the catalyst layer ink from the inner side to the outer side in the peripheral portion of the cathode catalyst layer 12a and the anode catalyst layer 12b. (The catalyst mass per unit area in the periphery of each catalyst layer may be reduced). For example, in the case of application by a spray method, by changing the number of times of application in the surface direction of the cathode catalyst layer 12a and the anode catalyst layer 12b, or changing the amount of ink applied to the catalyst layer, The catalyst layer structure in which the thickness of the part (the catalyst mass per unit area of the peripheral part of each catalyst layer) decreases from the inside toward the outside in the peripheral part of the cathode catalyst layer 12a and the anode catalyst layer 12b may be realized. .

  In order to define the application area of the cathode catalyst layer 12a and the anode catalyst layer 12b, the desired cathode catalyst layer 12a and anode catalyst layer on the polymer electrolyte membrane or substrate on which the cathode catalyst layer 12a and anode catalyst layer 12b are applied. A mask is arranged in accordance with the shape of 12b. The shapes of the cathode catalyst layer 12a and the anode catalyst layer 12b may be defined by punching the cathode catalyst layer 12a and the anode catalyst layer 12b in advance in the mask, or may be defined by the arrangement of the mask. Note that the mask is generally a film of polyethylene terephthalate, polypropylene, kapton, or metal in consideration of adhesion to an object to be coated.

  As an example, the cathode catalyst layer 12a and the anode catalyst layer 12b of this embodiment can be formed using a mask having the structure shown in FIG. FIG. 13 is a schematic cross-sectional view showing a mask that can be used in this embodiment, the polymer electrolyte membrane 11 (or support), and their positional relationship. When the mask 19a having a cross section as shown in FIG. 13 is used, the polymer electrolyte membrane 11 and the mask 19b are adhered and fixed, and the ink for forming the catalyst layer is applied by spraying, the cathode catalyst layer 12a and the anode In the periphery of the catalyst layer 12b, the thickness of the periphery of each catalyst layer can be decreased from the inside to the outside (the catalyst mass per unit area of the periphery of each catalyst layer is increased from the inside to the outside). Can be reduced towards).

  Furthermore, as another example, the cathode catalyst layer 12a and the anode catalyst layer 12b of the present embodiment can be formed using a mask having the structure shown in FIG. FIG. 14 is a schematic cross-sectional view showing a mask that can be used in this embodiment, the polymer electrolyte membrane 11 (or support), and their positional relationship. If a mask 19b having a cross section as shown in FIG. 14 is used, the polymer electrolyte membrane 11 and the mask 19b are fixed through a gap without being in close contact, and the catalyst layer forming ink is applied by spraying, The catalyst mass per unit area in the periphery of the catalyst layer can be decreased from the inside toward the outside in the periphery of the cathode catalyst layer 12a and the anode catalyst layer 12b. That is, the ink for forming the catalyst layer enters the gap between the mask 19b and the polymer electrolyte membrane 11, and the catalyst mass per unit area of the periphery of each catalyst layer is determined as the periphery of the cathode catalyst layer 12a and the anode catalyst layer 12b. It is possible to decrease from the inside toward the outside.

  Furthermore, as an example of this embodiment, a catalyst layer structure in which the catalyst mass per unit area is reduced may be realized by changing the catalyst layer ink composition. Specifically, by reducing the catalyst supporting rate in the catalyst supporting carbon constituting the catalyst layer ink to be applied from the inner side toward the outer side in the peripheral part of the cathode catalyst layer 12a and the anode catalyst layer 12b, the catalyst mass can be increased. A reduction is feasible. In this case, as described above, the thickness of the peripheral portion of each catalyst layer is not decreased from the inside to the outside, and the thickness of the peripheral portion of each catalyst layer is set to a substantially constant thickness. It is possible to reduce the catalyst mass per unit area at the periphery of the layer from the inside to the outside.

In the present embodiment, layer structures having different material compositions constituting the cathode catalyst layer 12a and the anode catalyst layer 12b may be formed in the thickness direction of the cathode catalyst layer 12a and the anode catalyst layer 12b. In this case, each layer may be formed by either a direct coating method or an indirect coating method.
A conventionally known method may be used as the thermal transfer and bonding method. As described above, in at least one of the anode catalyst layer and the cathode catalyst layer, the mass per unit area of the catalyst layer of the electrode catalyst is the cathode. As long as it is possible to realize that there are reduced portions that decrease from the inside toward the outside in the peripheral portions of the catalyst layer 12a and the anode catalyst layer 12b, the design of the manufacturing method can be appropriately changed.

  Further, as a method other than the above, after the cathode catalyst layer 12a and the anode catalyst layer 12b having a substantially uniform thickness as a whole are formed, the ink for forming the catalyst layer is applied to the periphery of the cathode catalyst layer 12a and the anode catalyst layer 12b. For example, a decreasing portion that decreases from the inside toward the outside may be formed by dispersing and applying in an island shape.

Here, as an example of the embodiment, the membrane catalyst layer assembly 20 produced in Example 1 below is an example of an optical microscope image of the cathode catalyst layer 12a of the main surface of the polymer electrolyte membrane 11 as viewed from a substantially normal direction. A portion including the peripheral portion 12a ₁ is shown in FIG. In addition, the portion including the peripheral portion of the cathode catalyst layer 112a in the optical microscopic image of the conventional membrane-catalyst layer assembly produced in Comparative Example 1 described below viewed from the direction substantially normal to the main surface of the polymer electrolyte membrane 111. Is shown in FIG.
In the membrane catalyst layer assembly 20 of Example 1 below, the polymer electrolyte membrane 11 and the mask 19b shown in FIG. 14 are not in close contact (that is, provided with a gap). The membrane / catalyst layer assembly of Comparative Example 1 below was prepared by applying the ink for forming the catalyst layer and sprayed with the polymer electrolyte membrane 111 and the mask 19b shown in FIG. Thus, a catalyst layer forming ink is applied to the polymer electrolyte membrane 111. The conditions relating to the application of the catalyst layer are the same as the catalyst layer ink used for spraying and the number of sprays, etc., except for the mask adhesion.

As shown in FIG. 15, in an example of this embodiment, the central portion of the cathode catalyst layer 12a defined by the inside of the peripheral portion 12a ₁ of the cathode catalyst layer 12a, that is, the portion indicated by P of the mask 19b in FIG. It can be seen that the catalyst mass per unit area decreases from about 300 μm toward the outer side from the portion P indicating the outer peripheral portion. Further, the catalyst is scattered in the region outside 300 μm or more. This catalyst layer scattering region (decreasing portion) is a region of about 700 μm from the portion P. That is, the distance S of the reduced portion starting from the portion P is about 700 μm.
Here, the sum of the width (surface direction) of the peripheral portion 12a ₁ where the catalyst mass per unit area of the catalyst layer is reduced and the width (surface direction) of the scattering region is the center of the cathode side catalyst layer 12a. It is preferable that it is more than this thickness. As described above, when the sum of the width (surface direction) of the peripheral portion 12a _{1 and} the width (surface direction) of the scattering region is equal to or greater than the thickness of the central portion of the cathode-side catalyst layer 12a, the catalyst layer generated by the production process. It is less affected by damage such as chipping at the periphery, and can exhibit good battery characteristics.

Further, as described above, the outer end portion of the central portion Z of the cathode-side catalyst layer 12a indicated by the portion P is located at the position indicated by the portion Q of the gas diffusion layer 13a as shown in FIGS. It is preferable that it exists inside the outer end portion (that is, the central portion side of the polymer electrolyte membrane 11). As described above, when the outer end portion of the central portion Z of the cathode side catalyst layer 12a exists inside the outer end portion of the gas diffusion layer 13a, the reaction heat due to the catalytic reaction can be dissipated through the gas diffusion layer 13a. Long-life battery characteristics can be obtained with certainty.
Here, although only describes the peripheral portion 12a1 of the cathode-side catalyst layer 12a with reference to FIG. 15, other peripheral portions 12a _2, and the anode side peripheral portion 12b of the catalyst layer 12b ₁ and the cathode-side catalyst layer 12a The same applies to 12b ₂ .

Whether or not the catalyst layer which is the greatest feature of the present invention as described above is used in the membrane catalyst layer assembly 20, the membrane electrode assembly 10 and the fuel cell 1 can be confirmed by the following method. is there.
According to cross-sectional observation with an electron beam microanalyzer (EPMA), it is possible to quantify atoms such as platinum as an electrode catalyst in the catalyst layer. Furthermore, secondary ion mass spectrometer (SIMS), X-ray diffractometer (XRD), emission analyzer (OES), energy dispersive X-ray fluorescence analyzer (EDX), wavelength dispersive X-ray fluorescence analyzer (XRF) ) And the like, it is possible to quantitatively analyze the atoms (elements) of the catalyst, and it is possible to measure the distribution of the catalyst metal per unit area in the catalyst layer surface direction.

As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to the said embodiment.
For example, in the membrane catalyst layer assembly 20, the membrane electrode assembly 10, and the fuel cell 1 of the present invention, the mass per unit area of the electrode catalyst catalyst layer in at least one of the cathode side catalyst layer and the anode side catalyst layer. However, it is only necessary to decrease from the inner side toward the outer side in the peripheral part of at least one of the cathode side catalyst layer and the anode side catalyst layer. More effectively, it is desirable to have a catalyst layer structure in which the electrode catalyst is reduced in both the cathode side catalyst layer and the anode side catalyst layer.

In the above-described preferred embodiment of the polymer electrolyte fuel cell including the membrane catalyst layer assembly according to the present invention , the polymer electrolyte fuel cell including only one fuel cell 1 has been described. However, the present invention is not limited to this .

  In the above-described embodiment, the cooling water flow path 18 is provided in both the anode side separator 16 and the cathode side separator 16. However, the cooling water flow path 18 is provided in at least one separator 16. Also good. In particular, when a stack obtained by stacking a plurality of fuel cells 1 is used as the polymer electrolyte fuel cell of the present invention, one cooling water channel 18 may be provided for every two to three fuel cells 1. Good.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in more detail, this invention is not limited to these Examples at all.

Example 1
In this example, first, a membrane catalyst layer assembly of the present invention having the structure shown in FIG. 3 was produced.
A catalyst-supporting carbon (TEC10E50E manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., 50% by mass of Pt) obtained by supporting platinum particles as an electrode catalyst on carbon powder, and a polymer electrolyte solution having hydrogen ion conductivity (Asahi Glass ( Flemion) was dispersed in a mixed dispersion medium (mass ratio 1: 1) of ethanol and water to prepare a cathode catalyst layer forming ink.
The polymer electrolyte was added so that the mass of the polymer electrolyte in the catalyst layer after coating formation was 0.4 times the mass of the catalyst-supported carbon.

Using the obtained cathode catalyst layer forming ink, a cathode catalyst layer having a single layer structure was formed so that the total amount of platinum supported was 0.6 mg / cm ² . First, the cathode catalyst layer ink adjusted so that the mass of the polymer electrolyte is 1.0 times is sprayed on one surface of the polymer electrolyte membrane (GSII, 150 mm × 150 mm, manufactured by Japan Gore-Tex Co., Ltd.). The cathode catalyst layer was formed with a platinum loading of 0.12 mg / cm ² .
At the time of applying the catalyst layer, a substrate (PET) punched out to 140 mm × 140 mm was used as a mask. The mask is placed on the polymer electrolyte membrane, which is an object to be coated, only at the time of spray coating without going through a step of improving adhesion to the polymer electrolyte membrane by thermocompression in advance. A weight was placed about 10 mm away from the extracted inner periphery (portion indicated by p in FIG. 14).
It was speculated that the positional relationship between the polymer electrolyte membrane 11 and the mask 19b as shown in FIG. 14 was realized by the pressure of air used for spraying due to the usage of the mask, as shown in FIG. .

Next, a catalyst-supported carbon (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) in which platinum ruthenium alloy (platinum: ruthenium = 1: 1.5 molar ratio (substance ratio)) particles as electrode catalysts are supported on carbon powder. TEC61E54, 50% by mass of Pt—Ru alloy) and a polymer electrolyte solution having hydrogen ion conductivity (Flemion manufactured by Asahi Glass Co., Ltd.), a mixed dispersion medium of ethanol and water (mass ratio 1: 1) An ink for forming an anode catalyst layer was prepared by dispersing in an aqueous solution.
The obtained ink for forming an anode catalyst layer was applied to the other surface of the polymer electrolyte membrane opposite to the surface on which the cathode catalyst layer was formed by a spray method, and had a single layer structure and a platinum carrying amount. Formed an anode catalyst layer at 0.35 mg / cm ² .
The shape of the mask and the method of use were the same as in the preparation of the cathode catalyst layer.

Next, using a membrane catalyst layer assembly of the present invention obtained as described above, to produce a membrane electrode assembly that having a structure shown in FIG.
In order to form a gas diffusion layer, a carbon cloth (SK-1 manufactured by Mitsubishi Chemical Corporation) having a size of 16 cm × 20 cm and a thickness of 270 μm was used, and an aqueous dispersion containing a fluororesin (manufactured by Daikin Industries, Ltd.). ND-1) was impregnated and then dried to impart water repellency to the carbon cloth (water repellency treatment).

  Subsequently, a water repellent carbon layer was formed on one surface (entire surface) of the carbon cloth after the water repellent treatment. Conductive carbon powder (Denka Black (trade name) manufactured by Denki Kagaku Kogyo Co., Ltd.) and an aqueous solution (D-1 manufactured by Daikin Industries, Ltd.) in which fine powder of polytetrafluoroethylene (PTFE) is dispersed. By mixing, an ink for forming a water-repellent carbon layer was prepared. This water repellent carbon layer forming ink was applied to one surface of the carbon cloth after the water repellent treatment by a doctor blade method to form a water repellent carbon layer. At this time, a part of the water repellent carbon layer was embedded in the carbon cloth.

Thereafter, the carbon cloth after the water repellent treatment and the formation of the water repellent carbon layer was fired at 350 ° C., which is a temperature equal to or higher than the melting point of PTFE, for 30 minutes. Finally, the central portion of the carbon cloth was cut with a punching die to obtain a gas diffusion layer with dimensions of 142.5 mm × 142.5 mm.
Next, the membrane-catalyst layer assembly is sandwiched between two gas diffusion layers so that the central portion of the water-repellent carbon layer of the gas diffusion layer obtained as described above is in contact with the cathode catalyst layer and the anode catalyst layer, The whole was subjected to thermocompression bonding (120 ° C., 30 minutes, 10 kgf / cm ² ) with a hot press machine to obtain a membrane electrode assembly .

Finally, using the membrane electrode assembly obtained as described above, to produce a fuel cell (unit cell) 1 that have a structure shown in FIG. The membrane electrode assembly is sandwiched between a separator having a gas flow path for supplying a fuel gas and a cooling water flow path, and a separator having a gas flow path for supplying an oxidant gas and a cooling water flow path, and a cathode between both separators. and fluorine rubber gasket placed around the anode, the effective electrode (anode or cathode) area to give a single cell (fuel cell) which is 36cm ^2.

Example 2
A single cell (fuel cell) was obtained in the same manner as in Example 1 except that the catalyst layer was formed so that the catalyst mass reduction region (distance of the reduced portion around the catalyst layer periphery) was in the range shown in Table 1.

<< Comparative Example 1 >>
A membrane / catalyst layer assembly, a membrane / electrode assembly, and a unit cell were produced in the same manner as in Example 1 except that the method of using the mask during spray coating to define the catalyst layer shape was used.
The mask was brought into close contact with both surfaces of the polymer electrolyte membrane by spraying (90 ° C., 3 minutes, 10 kgf / cm ² ) before spray coating. At the time of spray coating, the cathode catalyst layer and the anode catalyst layer were formed through a mask adhered to the polymer electrolyte membrane.

[Evaluation test]
(1) Direct observation of membrane catalyst layer peripheral portion The membrane electrode assemblies obtained in Example 1 and Comparative Example 1 were observed with an optical microscope. Specifically, the reduction area of the catalyst mass per unit area, specifically, the distance from the outer periphery of the catalyst layer defined by the mask to the outer periphery of the actual catalyst layer was measured. The results are shown in Table 1.
Moreover, the part including the peripheral part of a cathode catalyst layer in the optical microscope image which looked at the membrane-catalyst layer assembly obtained in Example 1 and Comparative Example 1 from a substantially normal direction to the main surface of the polymer electrolyte membrane (See FIGS. 15 and 16).

(2) Catalyst mass decrease region (distance of the decrease portion around the catalyst layer)
As shown in FIG. 4, the four sides of the peripheral portion of the main surface of the substantially rectangular cathode catalyst layer and the four sides of the peripheral portion of the main surface of the substantially rectangular anode catalyst layer are divided into four equal parts, respectively. part is a obtained by 16 equal parts, in the cathode catalyst layer and anode catalyst layer units periphery Y ₁ to Y ₁₆ 16 pieces each of the distribution of the platinum particles using energy dispersive X-ray fluorescence analyzer (EDX) Using the optical microscope and scanning electron microscope (SEM) to observe the state, the outer end of the reduced portion starting from the outer end portion 17a (part P) of the central portion Z of the cathode gas diffusion layer and the anode catalyst layer The distance S to the part was measured, and the range between the maximum value and the minimum value of the distance S was determined.

(3) Durability evaluation test The unit cells obtained in the above examples and comparative examples were controlled at 70 ° C., hydrogen gas was supplied as fuel gas to the anode-side gas flow path, and the cathode-side gas flow path was Each was supplied with air. At this time, the utilization rate of hydrogen gas was set to 70%, the utilization rate of air was set to 40%, and humidification was performed so that the dew points of hydrogen gas and air were about 70 ° C., respectively. Then, the cell was operated for 12 hours at a current density of 0.3 mA · cm ⁻² for aging (activation treatment).

After aging (activation treatment), each cell was subjected to an accelerated durability test in which the deterioration of the membrane electrode assembly was accelerated and the life could be judged in a shorter time. In the accelerated durability test, each unit cell was operated so that the polymer electrolyte membrane had relatively low humidification. Specifically, the cell temperature is raised to 90 ° C., while a mixed gas of hydrogen and carbon dioxide (volume ratio 8: 2) is supplied to the gas flow path on the anode side, and the gas flow path on the cathode side is supplied. Air was supplied, and the dew points of both gases were about 70 ° C., respectively. The operation was performed at a current density of 0.16 mA · cm ⁻² .
The acceleration test was performed until the operation became impossible due to a decrease in battery voltage. The durability of the cell was judged from the operating time. The results are shown in Table 1.

FIG. 15 shows a portion including a peripheral portion of the cathode catalyst layer in an optical microscope image of the membrane / catalyst layer assembly produced in Example 1 as seen from a substantially normal direction to the main surface of the polymer electrolyte membrane, FIG. 16 shows a portion including a peripheral portion of the cathode catalyst layer in an optical microscopic image of the membrane / catalyst layer assembly of Comparative Example 1 viewed from a substantially normal direction to the main surface of the polymer electrolyte membrane.
The membrane / catalyst layer assembly 20 of Example 1 was sprayed onto the polymer electrolyte membrane 11 by spraying in a state where the polymer electrolyte membrane 11 and the mask 19b shown in FIG. 14 were not in close contact (that is, provided with a gap). The membrane-catalyst layer assembly of Comparative Example 1 was prepared by applying a forming ink, and the polymer electrolyte membrane 111 and the mask 19b shown in FIG. This is prepared by applying a catalyst layer forming ink to the molecular electrolyte membrane 111. The conditions relating to the application of the catalyst layer are the same as the catalyst layer ink used for spraying and the number of sprays, etc., except for the mask adhesion.

As shown in FIG. 15, in Example 1, the outer periphery of the central portion of the cathode catalyst layer 12a defined by the inside of the peripheral portion 12a ₁ of the cathode catalyst layer, that is, the portion indicated by p of the mask 19b in FIG. It was confirmed that the catalyst mass per unit area decreased from about 300 μm toward the outside from the portion of line P indicating the portion. Furthermore, the catalyst was scattered in the region outside 300 μm or more. This catalyst layer scattering region is a region of about 700 μm from the line P. The same applies to the peripheral portions 12b ₁ and 12b ₂ of the anode side catalyst layer 12b. On the other hand, in the comparative example 1, it was confirmed that the catalyst layer scattering region as described above was not formed.
Further, as is apparent from the results in Table 1, it was confirmed that the membrane / electrode assembly of Example 1 can realize excellent durability and long-life battery characteristics with respect to the membrane / electrode assembly of Comparative Example 1. It was.

The polymer electrolyte fuel cell including the membrane-catalyst layer assembly according to the present invention is expected to be suitably used for a mobile body such as an automobile, a distributed power generation system, a household cogeneration system, and the like.

It is a schematic sectional drawing which shows an example of the basic composition of the single cell mounted in suitable one Embodiment of the polymer electrolyte fuel cell containing the membrane catalyst layer assembly based on this invention. It is a schematic sectional drawing which shows an example of the basic composition of the membrane electrode assembly mounted in the fuel cell 1 shown in FIG. It is a schematic sectional drawing which shows an example of the membrane catalyst layer assembly which comprises the membrane electrode assembly 10 shown in FIG. FIG. 4 is a schematic front view of the membrane catalyst layer assembly 20 as viewed from the direction of arrow R in FIG. 3. FIG. 4 is an enlarged cross-sectional view of a main part in which a main part of a peripheral part 12a ₁ (Y) of a cathode catalyst layer 12a of the membrane catalyst layer assembly 20 shown in FIG. 3 is enlarged. FIG. 4 is an enlarged cross-sectional view of a main part in which a main part of a modified example of a peripheral part 12a ₁ (Y) of a cathode catalyst layer 12a of the membrane catalyst layer assembly 20 shown in FIG. 3 is enlarged. FIG. 5 is an enlarged cross-sectional view of a main part in which a main part of another modification of the peripheral part 12a ₁ (Y) of the cathode catalyst layer 12a of the membrane catalyst layer assembly 20 shown in FIG. 3 is enlarged. FIG. 2 is a front view when the main surface of an anode-side separator 16b of the fuel cell 1 shown in FIG. 1 is viewed from the cooling water flow path 18 side. FIG. 2 is a front view when the main surface of an anode side separator 16b of the fuel cell 1 shown in FIG. 1 is viewed from the gas flow path 17b side. FIG. 2 is a front view when the main surface of a cathode-side separator 16a of the fuel cell 1 shown in FIG. 1 is viewed from the gas flow path 17a side. FIG. 2 is a front view when the main surface of a cathode separator 16a of the fuel cell 1 shown in FIG. 1 is viewed from the cooling water flow path 18 side. It is a schematic sectional drawing which shows the structure of one Embodiment of the fuel cell stack comprised by laminating | stacking the fuel cell 1 of this embodiment shown in FIG. It is a schematic sectional drawing which shows the mask which can be used in one Embodiment of this invention, the polymer electrolyte membrane 11 (or support body), and these positional relationships. It is a schematic sectional drawing which shows the other mask which can be used in one Embodiment of this invention, the polymer electrolyte membrane 11 (or support body), and these positional relationships. The periphery of the cathode catalyst layer 12a in the optical microscope image of the membrane / catalyst layer assembly 20 produced as one embodiment (Example 1) of the present invention viewed from the direction substantially normal to the main surface of the polymer electrolyte membrane 11 This is a part including the part 12a ₁ . This is a portion including a peripheral portion of the cathode catalyst layer 112a in an optical microscopic image of a conventional (comparative example 1) membrane-catalyst layer assembly viewed from a substantially normal direction to the main surface of the polymer electrolyte membrane 111. It is a schematic sectional drawing which shows an example of the basic composition of the single cell mounted in the conventional polymer electrolyte fuel cell. It is a schematic sectional drawing which shows an example of the basic composition of the membrane electrode assembly mounted in the fuel cell 100 shown in FIG. It is a schematic sectional drawing which shows an example of the membrane catalyst layer assembly which comprises the membrane electrode assembly 101 shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,100 ... Fuel cell 10, 101 ... Membrane electrode assembly, 20, 102 ... Membrane catalyst layer assembly, 11, 111 ... Polymer electrolyte membrane, 12, 112 ... Catalyst Layer, 12a ... cathode catalyst layer, 12b ... anode catalyst layer, 13, 113 gas diffusion layer, 14a ... anode, 14b ... cathode, 114 ... electrode, 15, 115 ... gasket , 16, 116 ... separator, 17, 117 ... gas passage, 18, 118 ... cooling water passage, 19a, 19b ... mask, 24 ... manifold hole for fuel gas supply, 25. .. Manifold hole for fuel gas discharge, 26 ... Manifold hole for cooling water supply, 27 ... Manifold hole for cooling water discharge, 28 ... Manifold hole for supplying oxidant gas, 29 ... Oxidant gas Discharge machine Hold hole, 77a ... straight portion (long flow paths), 77b ... turn portions (short flow paths), 30 ... fuel cell stack.

Claims (3)

A method for producing a membrane / catalyst layer assembly comprising forming an anode catalyst layer on one surface of a polymer electrolyte membrane and a cathode catalyst layer on the other surface,
Placing in a state of a gap, the mask catalyst layer formed between the polymer electrolyte membrane and the catalytic layer forming a mask,
Applying the ink for forming a catalyst layer by a spray method, and forming at least one of the anode catalyst layer and the cathode catalyst layer on the surface of the polymer electrolyte membrane. . A method for producing a membrane / catalyst layer assembly comprising forming an anode catalyst layer on one surface of a polymer electrolyte membrane and a cathode catalyst layer on the other surface,
In a state in which a gap is provided between the catalyst layer forming mask tactile and supporting bearing member, a step of arranging a mask for forming the catalyst layer on the surface of the support,
Applying a catalyst layer forming ink by a spray method to form at least one of the anode catalyst layer and the cathode catalyst layer on the surface of the support;
Joining the obtained catalyst layer to the surface of the polymer electrolyte membrane, and a method for producing a membrane catalyst layer assembly. The catalyst layer forming mask has an inner peripheral portion of a shape punched to form the catalyst layer,
The catalyst layer forming ink is applied in a state where a gap is provided between the polymer electrolyte membrane or the support and the inner peripheral portion of the catalyst layer forming mask. Manufacturing method of membrane catalyst layer assembly.