JP2006040767A - Solid polymer fuel electrode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode for a fuel cell superior both in durability and catalyst performance. <P>SOLUTION: The electrode for solid polymer fuel comprises a catalyst layer which has two constitutions having a geometrical pattern, one of which is scattered in island shape, and the other of which has a groove structure to fill the spacings between the island shaped portions, and furthermore in which the island shaped portion has hydrophilic characteristics and the groove structure portion has water repellency. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polymer electrolyte fuel electrode, and more particularly to a polymer electrolyte fuel electrode in which durability and catalytic performance in an oxygen reduction electrode are compatible. Hereinafter, the membrane-electrode assembly is also referred to as MEA (abbreviation of membrane electrode assembly), the oxygen reduction electrode is also referred to as a cathode, and the gas diffusion layer is also referred to as GLD (abbreviation of gas diffusion layer).

  In recent years, in response to social demands and trends against the background of energy and environmental problems, attempts have been made to use solid polymer electrolyte fuel cells that can operate at room temperature and obtain high output density as power sources for automobiles and stationary applications. ing. In using such a fuel cell as an automobile or stationary power source, it is required to improve the power generation performance and maintain the desired power generation performance over a long period of time, that is, to improve the durability. The battery life is said to be 5,000 hours for an automotive power source and 40,000 hours for a stationary power source. For this reason, the catalyst used for the fuel cell electrode is required to maintain a desired catalytic activity over a long period from the beginning of power generation, and various research and development are being carried out.

  One possible means for improving power generation performance is to prevent flooding in the catalyst layer on the cathode side. In addition, as one means for achieving maintenance of power generation performance, suppression of corrosion of carbon which is an electrode catalyst carrier is exemplified.

  Therefore, in Patent Document 1, the water repellency in the catalyst layer from the side in contact with the polymer electrolyte membrane toward the porous substrate side of the gas diffusion layer due to the change in the content of the water repellent material such as PTFE in the catalyst layer. An electrode for a fuel cell is disclosed in which is continuously changed.

Further, in Patent Documents 2 and 3, in order to improve the water repellency by the water-repellent carbon in the gas diffusion layer, hydrophilic carbon such as furnace black and vulcan, and hydrophobic such as acetylene black and denka black are formed on the gas diffusion layer. Disclosed is a gas diffusion electrode comprising a conductive carbon and a water repellent.
JP 2003-109604 A JP-A-7-220734 JP-A-7-078617

  However, in the invention of the above-mentioned Patent Document 1, the water repellency in the catalyst layer is continuously changed by changing the content of the water repellent material such as PTFE, but the corrosion of the carbon that is the electrode catalyst carrier is suppressed. It is difficult to improve durability because there is no effect. Moreover, although drainage can be improved, there is a possibility of causing a decrease in gas diffusibility. Further, since the water repellent material cannot be used as a catalyst support, the amount of catalyst is relatively reduced by increasing the water repellent material in the catalyst layer. Therefore, it is difficult to achieve both power generation performance and durability.

  Furthermore, in the electrode catalyst of the said patent document 2, 3, although the drainage property improvement by water-repellent carbon is performed in a gas diffusion layer, the effect with respect to the durability improvement of a catalyst layer is small.

  Accordingly, an object of the present invention is to provide a polymer electrolyte fuel electrode that is excellent in both durability and catalytic performance.

As a result of intensive studies by the inventor in view of the above-mentioned problems, the catalyst layer has two configurations having a geometric pattern, one is dotted in an island shape, and the other is filling the gap in the island-shaped portion. It has a groove structure like
Furthermore, it has been found that the above-mentioned problems can be solved by a polymer electrolyte fuel electrode characterized in that the island-like portion has hydrophilicity and the groove structure portion has water repellency.

  According to the polymer electrolyte fuel electrode of the present invention, a highly water-repellent catalyst portion and a highly hydrophilic portion are distinguished in the same plane to realize a geometrical arrangement, and the catalyst layer surface has a high water repellency. A drainage channel can be formed. This makes it possible to suppress flooding without deteriorating gas diffusivity in the catalyst layer, and to suppress catalyst detachment due to corrosion of carbon, which is excellent in durability and catalytic performance. An electrode can be provided. Therefore, in the fuel cell using the polymer electrolyte fuel electrode, the power generation performance can be improved and high power generation performance can be maintained over a long period from the beginning of power generation.

  The polymer electrolyte fuel electrode of the present invention has two configurations having a geometric pattern in the catalyst layer, one is dotted in an island shape, and the other is a groove that fills the gap in the island portion. In addition, the island-shaped portion has hydrophilicity, and the groove-structure portion has water repellency. In the present invention, a hydrophilic portion and a water-repellent portion are formed in the catalyst layer on the cathode side in order to prevent both drying and flooding of the membrane. By doing in this way, water retention improves in a hydrophilic part, drainage improves in a water-repellent part, and the contradictory phenomenon of drying and flooding can be suppressed. In addition, when the water-repellent part has a groove structure that fills the gap between the hydrophilic island-like parts, that is, a continuous structure, excess water can move to a water-deficient part.

  Explaining the above points in detail, in the polymer electrolyte fuel cell, on the catalyst surface in the cathode, protons moving from the anode react with the supplied oxidant gas (oxygen) to produce water. If this generated water is excessively retained in the catalyst layer, the diffusion path of the oxidant gas is blocked with water, and the gas diffusibility is lowered, resulting in a decrease in power generation performance. In order to eliminate such flooding phenomenon, conventionally, as disclosed in Patent Document 1, a measure such as mixing a water repellent in the catalyst layer has been taken. However, even though flooding due to generated water can be suppressed, there is a high possibility that the diffusion path of the oxidant gas is reduced by the water repellent and the improvement in battery performance is limited. In addition, in order for protons to move sufficiently within the catalyst layer, it is necessary that water is present in the catalyst layer appropriately. Therefore, in the catalyst layer, it is necessary to ensure water appropriately and prevent excessive water from staying, but such a polymer electrolyte fuel electrode has not been provided.

  Therefore, like the polymer electrolyte fuel electrode of the present invention, it has a hydrophilic island-like structure in the catalyst layer and a water-repellent groove structure that fills the gap between the island-like portions. It is possible to suppress the contradictory phenomenon of drying and flooding in the catalyst layer, and an improvement in battery performance can be expected.

  The solid polymer type fuel electrode of the present invention comprises a catalyst layer containing a carbon powder supporting a catalyst and a polymer electrolyte, and a gas diffusion layer.

  FIG. 1 shows a basic structure of a fuel cell 10 including the polymer electrolyte fuel electrode. As shown in FIG. 1, the polymer electrolyte membrane 11 is sandwiched between solid polymer fuel electrodes (hereinafter also simply referred to as electrodes) 14 including a catalyst layer 12 and a gas diffusion layer 13. A joined body of the polymer electrolyte membrane 11 and the electrode 14 is referred to as MEA 15. The MEA 15 is sandwiched by a separator 17 having a flow path 16 for fuel gas or reaction gas. In the fuel cell, the catalyst layer 12 side of the electrode 14 is in contact with the polymer electrolyte membrane 11, and the gas diffusion layer 13 side is in contact with the separator 17.

  In the above basic structure, the fuel gas is supplied to the gas diffusion layer 13a from the fuel gas flow path 16a provided on the surface of the separator 17 in contact with the anode side, passes through the gas diffusion layer 13a while diffusing, and reaches the catalyst layer 12a. The oxidant gas is supplied to the gas diffusion layer 13b from the reaction gas flow path 16b provided on the surface of the separator 17 in contact with the cathode side, passes through the gas diffusion layer 13b while diffusing, and reaches the catalyst layer 12b.

The electrode reaction occurs on the surface of the catalyst contained in the catalyst layer 12. In the catalyst layer 12a on the anode side, a reaction of H ₂ → 2H ++ 2e ⁻ occurs. In the catalyst layer 12b on the cathode side, a reaction of 1 / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O occurs. The overall reaction is H ₂ + 1 / 2O ₂ → H ₂ O + Q. An electromotive force is obtained by this reaction and power generation is possible. At the same time, water is generated in the catalyst layer 12b on the cathode side. Further, H ⁺ generated in the catalyst layer 12a on the anode side during the reaction moves through the polymer electrolyte membrane 11 and reaches the catalyst layer 12b on the cathode side. At this time, one H ⁺ ion moves along with 5 to 20 H ₂ O molecules.

The polymer electrolyte membrane 11 exhibits high hydrogen ion conductivity for the first time in a state swollen with a sufficient amount of water. However, since a large amount of water moves along with the H ⁺ ions moving in the polymer electrolyte membrane 11 to the cathode 14b, it is necessary to always supply water to the polymer electrolyte membrane 11. This water is supplied from the gas flow path 16 to the gas diffusion layer 13 as water vapor, and then supplied to the polymer electrolyte membrane 11 through the cathode 14b and the anode 14a. Further, of the water generated in the catalyst layer 12b on the cathode 14b side, excess water that is not required by the polymer electrolyte membrane 11 is discharged from the catalyst layer 12b to the outside through the gas diffusion layer 13b. Is done.

As described above, in the catalyst layer 12b on the cathode 14b side, the reaction gas (O ₂ or air) diffuses inside the porous electrode structure formed by the carbon powder carrying the catalyst and the polymer electrolyte, and the anode Proton (H ⁺ ) that has migrated from the 14a side through the polymer electrolyte membrane 11 is oxidized to produce reaction water (product water). If this water is not removed promptly, the diffusion of the reaction gas is hindered, and the power generation performance cannot be maintained or maintained.

  The porous base material (support) such as carbon paper or carbon cloth of the gas diffusion layer 13 is porous and has a large pore diameter, and the carbon layer applied and formed on the porous base material as needed is Since the particle size is large and the void ratio in the layer is high, and the water repellent material is added, the water repellent effect is remarkably higher than that of the catalyst layer 12. On the other hand, in the vicinity of the polymer electrolyte membrane 11, the membrane itself retains water and contains water, and the wettability is extremely high.

  For this reason, in order to accelerate the removal of the generated water, it is important to control the water repellency in the catalyst layer 12b because the catalyst layer 12b on the cathode 14b side has a large amount of water entering and exiting. In particular, from the viewpoint of preventing flooding and enhancing durability, it is necessary to design the water repellency inside the catalyst layer 12b so that excess water can be quickly discharged to the outside through the gas diffusion layer 13b.

  Therefore, in the present invention, from the viewpoint of quick removal of the generated water, in the catalyst layer where water enters and exits frequently, carbon having high water repellency and carbon having high hydrophilicity (low water repellency) are used. It has been found that it is effective to provide a continuous hydrophobic change (gradient) in the catalyst layer. That is, in the present invention, the catalyst layer 12 has two configurations having various geometric patterns (typical patterns 1 to 6 are illustrated in FIGS. 2 to 7), and one of the two is an island shape 12P. One of them has a groove structure 12Q that fills the gap between the island-like portions 12P. Further, the island-shaped portion 12P has hydrophilicity, and the groove-shaped portion 12Q has water repellency.

  In the present invention, several kinds of geometric patterns of the catalyst layer are described below, but the present invention is not limited to these. It is desirable that the drainage channel (water-repellent part) of pattern 1 has a lattice shape from the viewpoint of easy pattern production and easy contact between the grooves (functioning as a drainage channel can be easily achieved by contact) I can say that.

  Pattern 1 in FIG. 2 is an example of a catalyst layer (corresponding to Example 1 described later) in which the geometric pattern in the surface of the catalyst layer 12 is a lattice. Here, the island-like portions 12P having hydrophilicity are quadrangular, and are arranged at regular intervals (width and space) vertically and horizontally (in FIG. 2, 3 vertically × horizontal). 3 total 9). The island portion 12P having hydrophilicity is formed using, for example, hydrophilic carbon as a catalyst carrier. On the other hand, the groove structure 12Q that fills the gap between the quadrangular island-like portions 12P is formed in a so-called lattice shape, so that the hydrophilic portion can be obtained. The groove-structured portion 12Q can be formed as a water-repellent portion by forming the catalyst carrier using water-repellent carbon, for example.

  The pattern 2 in FIG. 3 is a catalyst layer in which the island-like portion 12P having hydrophilicity is circular in the geometric pattern in the surface of the catalyst layer 12, and the water-repellent portion 12Q surrounds the gap. It is an example. Here, the island-like portions 12P having hydrophilicity are arranged such that the distance between the centers of adjacent circular portions is vertical and horizontal with a certain interval (width and space) (in FIG. 3 x 3 next to 9). The circular island-like portion 12P having hydrophilicity can be formed into a hydrophilic portion by forming the catalyst carrier with hydrophilic carbon, for example. On the other hand, the water repellent portion 12Q having water repellency surrounded so as to fill the gap between the circular island portions 12P is formed by using water repellent carbon for the catalyst carrier, for example. It can be.

  Pattern 3 in FIG. 4 is a geometric pattern in the surface of the catalyst layer 12 in which the island-like portion 12P having hydrophilicity has a rhombus shape, and the gap structure has a water-repellent groove structure. It is an example of the catalyst layer which the part 12Q surrounds. Here, the rhombus-like island-like portions 12P having hydrophilicity are arranged at regular intervals (width and space) vertically and horizontally (a total of 21 in FIG. 4). The island-like portion 12P having hydrophilicity can be formed as a hydrophilic portion by forming the catalyst carrier with hydrophilic carbon, for example. On the other hand, the groove-shaped portion 12Q that fills the gap between the rhombic island-shaped portions 12P can be formed as a water-repellent portion by forming the catalyst carrier using water-repellent carbon, for example.

  The pattern 4 in FIG. 5 is a geometric pattern in the surface of the catalyst layer 12, in which the island-like portions 12 </ b> P having hydrophilicity are triangular, and the gaps have a groove structure having water repellency. It is an example of the catalyst layer which the part 12Q surrounds. Here, the island-like portions 12P having a triangular hydrophilicity are arranged such that adjacent island-like portions 12P are vertically and horizontally spaced apart from each other (width and space) (in FIG. 15). The island-like portion 12P having hydrophilicity can be formed as a hydrophilic portion by forming the catalyst carrier with hydrophilic carbon, for example. On the other hand, the groove-shaped portion 12Q that fills the gap between the triangular island-shaped portions 12P can be formed as a water-repellent portion by forming the catalyst carrier using water-repellent carbon, for example.

  In the pattern 5 in FIG. 6, in the geometric pattern in the surface of the catalyst layer 12, the island-like portions 12P having hydrophilicity are present in an irregular shape (indefinite shape) in an island shape, and the gaps are formed. This is an example of a catalyst layer surrounded by a groove-structure portion 12Q having water repellency. The island-like portion 12P having hydrophilicity can be formed as a hydrophilic portion by forming the catalyst carrier with hydrophilic carbon, for example. On the other hand, the groove-shaped portion 12Q that fills the gaps between the irregularly shaped island-like portions 12P can be formed as a water-repellent portion by forming the catalyst carrier using water-repellent carbon, for example.

  In the pattern 6 in FIG. 7, in the geometric pattern in the catalyst layer 12 surface, the hydrophilic portion 12P and the water-repellent portion 12Q are in a lattice shape, the hydrophilic portions 12P are dotted in an island shape, and the gaps are formed. This is an example of a catalyst layer in which the groove structure portion 12Q to be filled is water repellent. Also, the closer to the gas outlet, the smaller the island-like portion having hydrophilicity and the larger the groove portion having water repellency compared to the closer to the gas inlet. The quadrangular hydrophilic island-like portion 12P can be formed into a hydrophilic portion by forming the catalyst carrier with hydrophilic carbon, for example. On the other hand, the groove-structured portion 12Q that fills the gap between the island-like portions 12P can be formed as a water-repellent portion by forming the catalyst carrier using water-repellent carbon, for example.

  In the polymer electrolyte fuel electrode of the present invention, the catalyst layer may be composed of at least two layers from the electrolyte membrane side toward the gas diffusion layer side. Thereby, in addition to the catalyst layer surface, a drainage channel having high water repellency can be freely formed in the thickness direction of the catalyst layer. This makes it possible to suppress flooding without deteriorating gas diffusivity in the catalyst layer, and to suppress catalyst detachment due to corrosion of carbon, which is excellent in durability and catalytic performance. Advantageously, an electrode can be provided.

In the present invention, in the catalyst layer composed of two or more layers, the catalyst layer in the catalyst layer closest to the electrolyte membrane is the catalyst layer 1, the next catalyst layer is the catalyst layer 2, and the catalyst on the side closest to the gas diffusion layer. When the layer is a catalyst layer N (N is the number of layers constituting the entire catalyst layer),
The area of the groove structure portion having water repellency in each of the catalyst layers 1 to N is X1, X2,... XN, and the area of the island-shaped portion having hydrophilicity in each catalyst layer Is Y1, Y2,... YN, the following formula (1)

What is characterized by becoming is desirable. This is because, in order to suppress flooding in the catalyst layer 12, it is optimal to improve the water repellency on the electrolyte membrane 11 side where water is excessive due to the generated water (see FIG. 1). In the catalyst layer 12, the place where water tends to exist excessively (place where the electrode reaction is most likely to proceed) is near the electrolyte membrane 11, and when protons move from the anode side to the cathode side, Move with water. Therefore, in the cathode catalyst layer 12b, the water in the portion close to the electrolyte membrane 11 is the most. Furthermore, in order to discharge excess water in the catalyst layer 12 from the catalyst layer 12 (electrode 14), it is necessary to move the water to the separator 17 in which the reaction gas flows. Accordingly, by reducing the water repellency from the electrolyte membrane 11 side toward the GDL 13 side, water can move from the electrolyte membrane 11 side to the GDL 13 side. Such an embodiment will be described with reference to the drawings.

  In FIG. 8, the cathode-side catalyst layer is composed of two layers. In order to satisfy the above formula (1), the catalyst layer on the electrolyte membrane side has smaller islands in the hydrophilic portion and the water-repellent portion. It is explanatory drawing which shows the example where the groove | channel is large (corresponding to Example 2 described later). 8A and 8B are arranged one above the other so that the size relationship between the hydrophilic portion and the water-repellent portion can be seen. FIG. 8A shows the gas in the cathode side catalyst layer. It is a schematic plan view showing a geometric pattern (lattice pattern) in the catalyst layer surface on the diffusion layer (not shown) side. FIG. 8B is a schematic plan view showing a geometric pattern (lattice pattern) in the catalyst layer surface of the cathode side catalyst layer on the electrolyte membrane side. FIG. 8C is a cross-sectional view taken along the line XX in FIGS. 8A and 8B, including configurations of the cathode side catalyst layer, the electrolyte membrane, and the anode side catalyst layer.

  As shown in FIG. 8, in the cathode side catalyst layer 12b composed of two layers, the catalyst layer on the electrolyte membrane 11 side is the catalyst layer 1, and the gas diffusion layer (not shown) side catalyst layer is the catalyst layer 2. In this case, the areas 12Q-1 and 12 of the groove structure 12Q-1 and 2 having water repellency in the catalyst layers 1 and 2 on the cathode side are X1 and X2, respectively, and the catalyst layers 1 and 2 have hydrophilicity. When the area (total hydrophilic partial area) of the island-like parts 12P-1 and 2 being Y1 and Y2, the relationship satisfying the formula (1); (X1 / Y1)> (X2 / Y2) is established. Yes. That is, the cathode side catalyst layer 12b is composed of two layers (catalyst layers 1 and 2), and the catalyst layer 1 on the electrolyte membrane 11 side is more hydrophilic than the catalyst layer 2 on the gas diffusion layer side. It is desirable that the island-shaped part is small and the water-repellent part of the groove structure is large. Thereby, in the cathode side catalyst layer 12b in which the catalyst layers 1 and 2 are laminated, the water repellency is weakened from the electrolyte membrane 11 side toward the GDL (not shown) side. Specifically, the area of the hydrophilic portion of the catalyst layer 2 is made larger than that of the catalyst layer 1, the area of the hydrophobic portion is made smaller, and the water repellency becomes weaker from the catalyst layer 1 toward the catalyst layer 2, thereby efficiently. Excess water in the catalyst layer 12b can be discharged, and the flooding phenomenon in the catalyst layer 12b can be suppressed.

  As shown in FIG. 8, the anode side catalyst layer 12a may have the same configuration as the cathode side catalyst layer 12b. However, since water is not generated in the catalyst layer, as shown in FIG. The catalyst structure may be one layer and one structure. In addition, the cathode side catalyst layer has an example of the cathode side catalyst layer constituted by two layers, but is not limited thereto, and the cathode side catalyst layer may be configured to satisfy the above formula (1) even in the case of three or more layers. That's fine.

  Further, in the present invention, in the catalyst layer composed of two or more layers, the groove structure having water repellency of the next catalyst layer on the drainage channel of the groove structure portion having water repellency. Desirably, a partial drainage channel is provided. This is because it is desirable that the drainage channel is continuous in order to facilitate the discharge of water in the catalyst layer. That is, in the catalyst layer, water tends to stay in the water-repellent part, but if the water-repellent part is discontinuous, there is a possibility that excessive water movement is less likely to occur. Then, it becomes possible to discharge | emit excess water efficiently by making drainage channels (water-repellent part) contact. That is, as shown in FIG. 8C, by laminating the water-repellent portions 12Q-1 and 12Q-2 in contact with each other, a drainage channel that efficiently discharges excess water is formed in the thickness direction of the catalyst layer. Can also be formed. However, even if the water-repellent portion of each layer is discontinuous, each layer has a hydrophilic island-like structure and a water-repellent groove structure that fills the gap between the island-like portions. A drainage channel for efficiently discharging excess water in the in-plane direction can be secured (see FIGS. 2 to 7). Therefore, the contradictory phenomenon of drying and flooding can be suppressed, and the first object of the present invention and its function and effect, which can improve battery performance, are not impaired at all.

In the polymer electrolyte fuel electrode of the present invention, in the catalyst layer, the catalyst layer is divided into at least four sections in the plane, and the catalyst layer in the portion closest to the gas outlet is defined as the catalyst layer 1 ′, When the catalyst layer adjacent to this is the catalyst layer 2 ′ and the catalyst layer closest to the gas inlet is the catalyst layer N ′ (N ′ represents the number of the catalyst layers divided in the plane). In addition,
The area of the groove structure portion having water repellency in each of the catalyst layers 1 ′ to N ′ is defined as X1 ′, X2 ′,. Further, when the area of the island-like portion having hydrophilicity in each catalyst layer is Y1 ′, Y2 ′,..., YN ′, the following formula (2)

What is characterized by becoming is desirable. During the power generation, the polymer electrolyte fuel cell tends to dry near the gas inlet, and tends to flood around the gas outlet. Therefore, as in this embodiment, by increasing the water-repellent part closer to the gas outlet side and increasing the hydrophilic part closer to the inlet side, sufficient water is secured in the dry tendency part, and in the flooding tendency part. It is possible to ensure sufficient drainage.

  In the catalyst layer, the catalyst layer tends to dry near the gas inlet, and the catalyst layer tends to flood near the outlet. Under such a phenomenon, the electrode reaction cannot proceed sufficiently in the vicinity of the gas inlet and the outlet, and as a result, the original power generation performance cannot be obtained. In order to obtain sufficient power generation performance, it is desirable that the wet state of the catalyst layer is uniform in the catalyst layer surface. However, it is virtually impossible to control this wet state by the humidified state or flow rate of the reaction gas. Therefore, the present inventor has come to find this embodiment based on the idea that it is most efficient to move water from an excessive water location to a insufficient water location in the catalyst layer surface. Such an embodiment will be described with reference to the drawings.

  FIG. 9 shows that the gas layer is closer to the gas outlet side by the catalyst layer divided into four by the difference in the occupied area of the water repellent part and the hydrophilic part in the catalyst layer surface so as to satisfy the above formula (2). It is explanatory drawing which shows the example of the catalyst layer formed so that the island of a hydrophilic part may be smaller than the nearer to the entrance side, and the groove | channel of a water-repellent part may become large (it respond | corresponds to Example 3 mentioned later).

As illustrated in FIG. 9, in the catalyst layer 12, the catalyst layer 12 is divided into four sections (four equal parts) in a cross shape in the plane, and the catalyst layer in the portion closest to the gas outlet is the catalyst layer. In the case where the layer 1 ′, the two adjacent upper and left catalyst layers are the catalyst layer 2 ′, and the catalyst layer closest to the gas inlet is the catalyst layer 3 ′,
The area of the groove structure portion having water repellency in each of the catalyst layers 1 ′, 2 ′, and 3 ′ is sequentially set to X1 ′, X2 ′, and X3 ′. Further, assuming that the area of the island-shaped portion having hydrophilicity in each catalyst layer 1 ′, 2 ′, 3 ′ is sequentially Y1 ′, Y2 ′, Y3 ′, the formula (2); (X1 ′) / Y1 ′)> (X2 ′ / Y2 ′)> (X3 ′ / Y3 ′). As in the present invention, in the plane of the catalyst layer 12, the island-like portion 12 </ b> P of the hydrophilic portion in the plane of the divided catalyst layers 1 ′, 2 ′, and 3 ′ approaches from the vicinity of the gas outlet to the vicinity of the inlet. By increasing the area ratio, decreasing the area ratio of the groove structure portion 12Q of the water-repellent part, and increasing the hydrophilicity, the hydrophilicity from the strong water-repellent part when the water retention amount is different in the same plane. Water moves to a strong spot. In other words, water can move from the gas outlet side where water is likely to exist excessively to the gas inlet side where water is likely to be insufficient, through the water-repellent portions 12Q-1 'to -3', which are drainage channels, and the catalyst. It becomes possible to form a uniform wet state in the plane of the layer 12, and an improvement in power generation performance can be expected.

Furthermore, in the present invention, it is desirable to have both of the embodiments shown in FIGS. That is, in the catalyst layer composed of two or more layers, the catalyst layer in the catalyst layer closest to the electrolyte membrane is the catalyst layer 1, the next catalyst layer is the catalyst layer 2, and the catalyst layer closest to the gas diffusion layer is the catalyst layer. In the case of the catalyst layer N (N is the number of layers constituting the entire catalyst layer),
The area of the groove structure portion having water repellency in each of the catalyst layers 1 to N is X1, X2,... XN, and the area of the island-shaped portion having hydrophilicity in each catalyst layer Is Y1, Y2,... YN, the following formula (1)

And
Further, in the catalyst layer, the catalyst layer is divided into at least four parts in the plane, the catalyst layer in the portion closest to the gas outlet is the catalyst layer 1 ′, the catalyst layer adjacent to the catalyst layer 1 ′, When the catalyst layer closest to the gas inlet is the catalyst layer N ′ (N ′ represents the number of the catalyst layers divided in the plane),
The area of the groove structure portion having water repellency in each of the catalyst layers 1 ′ to N ′ is defined as X1 ′, X2 ′,. Further, when the area of the island-like portion having hydrophilicity in each catalyst layer is Y1 ′, Y2 ′,..., YN ′, the following formula (2)

What is characterized by becoming is desirable. Thereby, the effect of two above-mentioned embodiments can be expressed effectively. That is, by reducing water repellency in the direction from the electrolyte membrane side to the GDL side of the catalyst layer and from the vicinity of the gas outlet to the vicinity of the inlet in the catalyst layer surface (in other words, increasing the hydrophilicity), the catalyst layer In addition to being able to discharge excess water, the flooding phenomenon in the catalyst layer can be suppressed, and water moves from a highly water-repellent location to a highly hydrophilic location. In other words, water can move from the gas outlet side where water is likely to exist excessively to the gas inlet side where water is likely to be insufficient, and a uniform wet state can be formed within the surface of the catalyst layer. The power generation performance can be improved. Such an embodiment will be described with reference to the drawings.

  FIG. 10 is divided into four parts by the difference in the area occupied by the water repellent part and the hydrophilic part in the catalyst layer surface so as to satisfy the above formula (2), and the water repellency is higher near the gas outlet than near the gas inlet. In addition, the side catalyst layer is composed of two layers, and the side close to the electrolyte membrane has a higher water repellency than the GDL side so as to satisfy the above formula (1). It is a figure (corresponding to Example 4 described later). 10A and 10B are arranged side by side so that the size relationship between the hydrophilic part and the water-repellent part can be seen. FIG. 10A shows a gas diffusion layer (not shown) of the catalyst layer. 3) is a schematic plan view showing a geometric pattern (lattice pattern) in the surface of the catalyst layer on the side. FIG. 10B is a schematic plan view showing a geometric pattern (lattice pattern) in the catalyst layer surface of the cathode side catalyst layer on the electrolyte membrane side. FIG. 10C is a cross-sectional view taken along the line XX in FIGS. 10A and 10B, including configurations of the cathode side catalyst layer, the electrolyte membrane, and the anode side catalyst layer.

  First, as illustrated in FIG. 10, in the cathode side catalyst layer 12b composed of two layers, the catalyst layer on the electrolyte membrane 11 side is the catalyst layer 1, and the catalyst layer on the gas diffusion layer (not shown) side is the catalyst layer. 2, the area of the groove structure portion having water repellency in each of the catalyst layers 1 and 2 on the cathode side (the total area of the water repellency portion of the entire catalyst layer divided into four parts) X1 and X2, and the area of the island-shaped portion having hydrophilicity in each of the catalyst layers 1 and 2 (the total area of the hydrophilic portion of the entire catalyst layer divided into four) is Y1 and Y2 in order, The relationship satisfies the formula (1); (X1 / Y1)> (X2 / Y2).

Further, in the cathode side catalyst layer 12b composed of two layers, the catalyst layers 1 and 2 are both divided into four cross sections (four equal parts) in the plane. The catalyst layer in the portion closest to the gas outlet is the catalyst layer 1a'1b ', the two adjacent upper and left catalyst layers are the catalyst layers 2a'2b', and the closest to the gas inlet. When the catalyst layer on the side is the catalyst layer 3a'3b ',
The area of the groove structure portion having water repellency in each of the catalyst layers 1a ′, 2a ′, 3a ′ and 1b ′, 2b ′, 3b ′ in the same plane is sequentially changed to X1a ′, X2a ′, X3a ′ and Let X1b ′, X2b ′, and X3b ′. In addition, the area of the island-like portion having hydrophilicity in each of the catalyst layers 1a ′, 2a ′, 3a ′ and 1b ′, 2b ′, 3b ′ in the same plane is sequentially expressed as Y1a ′, Y2a ′, Assuming that Y3a ′ and Y1b ′, Y2b ′, Y3b ′, in each of the catalyst layers 1 and 2, the formula (2); (X1a ′ / Y1a ′)> (X2a ′ / Y2a ′)> (X3a ′ / Y3a ′) ) And (X1b ′ / Y1b ′)> (X2b ′ / Y2b ′)> (X3b ′ / Y3b ′).

  In the relationship between the above formulas (1) and (2), X1 = X1a ′ + X2a ′ + X3a ′, X2 = X1b ′ + X2b ′ + X3b ′, and Y1 = Y1a ′ + Y2a ′ + Y3a ′. Y2 = Y1b ′ + Y2b ′ + Y3b ′.

  Further, in the polymer electrolyte fuel electrode of the present invention, (1) the catalyst-supporting carrier includes the hydrophilic island-like portion and the water-repellent groove structure in the catalyst layer. As described above, both of the water-repellent carbon and the carbon having high hydrophilicity or low water repellency are used without mixing, and the island-like portion having the hydrophilicity is hydrophilic. It may be formed using carbon having high or low water repellency, and the groove structure portion having water repellency may be formed using carbon having high water repellency. . Alternatively, (2) an island-like portion having hydrophilicity in the catalyst layer and a groove-structure portion having water repellency are used as a catalyst-supporting carrier and carbon having high water repellency and hydrophilicity It is formed so that the blending ratio with carbon having a high or low water repellency is different, and the portion of the front groove structure has a higher blending ratio of the carbon having a higher water repellency than the island-shaped portion. It may be a thing.

  That is, in the present invention, in forming two portions having different hydrophilicity / hydrophobicity in the catalyst layer, the hydrophilicity / hydrophobicity is not imparted (distinguished) using a water repellent or the like. It is desirable to impart (distinguish) hydrophilicity / hydrophobicity by using carbon having different hydrophilicity / water repellency as carrier carbon. For example, in the embodiment of the above (1), a catalyst slurry in which hydrophilic carbon black and water repellent carbon black are not mixed is used as the carrier carbon for supporting the catalyst. Distinguish between high parts. In the embodiment (2), a catalyst slurry obtained by mixing conventional carbon black (non-graphitized carbon black) as a hydrophilic material and graphitized carbon black in a water-repellent material is used as the carrier carbon for supporting the catalyst. The catalyst portion having high water repellency and the portion having high hydrophilicity may be separately arranged in the same plane, and the mixing ratio of hydrophilic carbon black and water repellent carbon black together with two types of catalyst slurry. May be blended (prepared) so that one is a highly hydrophilic catalyst slurry and the other is a highly water-repellent catalyst slurry. In any of the above embodiments (1) and (2), a geometrical arrangement is realized on the surface coated with two kinds of catalyst slurry, and a highly water-repellent drainage channel is formed in the catalyst layer surface. It is. Further, by applying the two kinds of slurries, the area of the water repellent portion is A1 and the area of the hydrophilic portion is B1 in the catalyst layer closest to the electrolyte membrane. When the area of the water-repellent part in the subsequent catalyst layer is A2, the area of the hydrophilic part is B2, the area of the water-repellent part closest to the GDL is AN, and the area of the hydrophilic part is BN, (A1 / B1 )> (A2 / B2)...> (AN / BN). Similarly, after dividing into four or more divisions in the same plane, from the gas outlet side to the gas inlet side. On the other hand, it can also apply | coat so that the area of a hydrophilic part may be raised.

  By forming a hydrophilic part (island-like part) and a water-repellent part (groove structure part) using two types of carrier carbons for supporting the catalyst having different hydrophilicity and hydrophobicity, the gas in the catalyst layer is formed. Flooding can be suppressed without reducing diffusibility, and catalyst detachment due to carbon corrosion can be suppressed, thereby improving durability.

The two types of support carbons for supporting the catalyst having different hydrophilicity and hydrophobicity used in the present invention are not particularly limited. However, as described below, the water-repellent portion (groove) in the catalyst layer is used. The water-repellent carbon that is the carrier carbon used to form the (structure portion) is desirably carbon that has been graphitized with a BET surface area of less than 150 m ² / g. On the other hand, the hydrophilic carbon that is the carrier carbon used to form the hydrophilic portion (island-like portion) in the catalyst layer is preferably a carbon material having a BET surface area of 150 m ² / g or more.

  That is, examples of means for imparting water repellency and hydrophilicity in the catalyst layer include a method of mixing a water repellent such as PTFE and PVDE, and a method of mixing a metal oxide and the like to impart hydrophilicity. However, although it is possible to impart water repellency and hydrophilicity to the catalyst layer by the means as described above, such water repellency part and hydrophilic part are not electrically conductive and resistance to electron transfer in the catalyst layer. It becomes a factor of increase of. In addition, if the water repellent or hydrophilic agent dissolves during power generation, there will be contamination in the electrode, which may reduce durability against long-term battery operation. Therefore, in providing a water-repellent part and a hydrophilic part in the catalyst layer, it is necessary to maintain the power generation performance over a long period of time without lowering the power generation performance. As in the present invention, by changing the catalyst-supporting carbon species as a means for imparting water repellency and hydrophilicity in the catalyst layer, there is no mixing of non-conductive substances, so that electrons by imparting water repellency and hydrophilicity can be obtained. The use of graphitized carbon that does not increase the movement resistance suppresses the corrosion of the carbon and makes it possible to maintain the power generation performance over a long period of time.

  Here, the carbon powder used for the carrier supporting the catalyst is originally heat-treated at a temperature necessary for carbonization, specifically, 1000 ° C. or more and less than 2000 ° C. Therefore, carbon powder (carbonized) used as a catalyst-supporting carrier has very few surface functional groups and acid sites, and has higher surface hydrophobicity than oxides. However, it becomes hydrophilic in use as described above. That is, it becomes highly hydrophilic carbon. Even in these carbon powders, the carbon heat-treated at a high temperature (2000 ° C. to 3000 ° C.) necessary for graphitization further reduces surface functional groups, has high hydrophobicity, and can be used for a long time. It is in a chemically stable (inactive) state. That is, it becomes carbon with high water repellency.

  The carbon powder used for the carrier supporting the catalyst is improved in corrosion resistance by being graphitized. On the other hand, the graphitized carbon has a specific surface area significantly reduced by high-temperature heat treatment, and the surface functional groups have also disappeared. Therefore, it is difficult to support the catalyst particles in a suitable state. The particles are easily aggregated. Therefore, an electrode catalyst using such graphitized carbon as a carrier is excellent in durability, but the catalytic activity is not sufficiently obtained especially at the beginning of power generation, and the catalytic activity is also obtained even when used for a long time. However, there was a problem that the catalyst performance was inferior.

  The performance of the catalyst has a close relationship with the dispersibility of the catalyst particles. For example, the larger the BET surface area of the carrier carbon, the higher the catalyst particles are dispersed and the higher the catalyst performance is obtained. The smaller the BET surface area of the carrier carbon is, the more the catalyst particles are aggregated and the catalyst performance is lowered.

  Further, the graphitized carbon has improved corrosion resistance by forming a graphitized layer on the surface. The corrosion resistance of carbon is greatly influenced not only by the graphitization rate of the graphitized layer but also by the thickness of the graphitized layer, and the higher the graphitized layer thickness, the higher the corrosion resistance. The thickness of the graphitized layer is inversely proportional to the BET surface area. The larger the BET surface area, the thinner the graphitized layer, and the smaller the BET surface area, the thicker the graphitized layer. Further, the thickness of the graphitized layer is difficult to control depending on the heat treatment conditions, and depends on the type of carbon used as a raw material.

  Thus, the corrosion resistance of the conductive carbon and the catalytic performance of the catalyst are in a trade-off relationship. In the present invention, as a result of various investigations on solid polymer fuel electrodes that are excellent in both durability and catalytic performance by paying attention to such carbon characteristics, graphitized carbon has high water repellency, and has a long time. Knowing that water repellency can be maintained even after use, geometric pattern of two types of carbon, newly high water repellency (graphitized) and other hydrophilic or low water repellency carbon It has been found that by disposing in the catalyst layer, removal of generated water in the catalyst layer can be promoted and the corrosion resistance of the carrier carbon can be suppressed. As a result, carbon having high oxidation corrosion resistance can be used effectively, and oxidative corrosion of conventional carbon having high hydrophilicity or low water repellency can be remarkably suppressed. As a result, it is possible to provide a fuel cell that is free from water clogging, has excellent discharge performance, and is highly durable and reliable.

  By thus forming a continuous water-repellent drainage channel in the catalyst layer 12 that generates water, surplus water quickly moves to the gas diffusion layer 13 (or the polymer electrolyte membrane 11) having a lower water-repellency. Then, it quickly passes through the gas diffusion layer 13 and moves to the gas flow path 16. In this way, excess water is provided with a continuous water-repellent portion drainage channel, and can be quickly discharged to the outside, preferably by changing the area ratio, thereby suppressing flooding due to water clogging within the electrode 14. it can. Further, since the gas permeability is not lowered, a fuel cell having high discharge characteristics and high reliability can be obtained.

  For the purpose of imparting water repellency in the catalyst layer, carbon having high water repellency (water repellent carbon) mainly used for forming a water repellant portion (groove structure portion) includes acetylene black and furnace black. In the present invention, it is desirable to use graphitized conductive carbon (graphitized carbon). Specifically, carbon obtained by heat treatment at 1000 ° C. or more and less than 2000 ° C. to perform carbonization treatment (conducting carbon black) is further heat-treated at a high temperature to perform graphitization treatment (graphitized carbon). Black; graphitized carbon black has higher conductivity than conventional conductive carbon black). Graphitized carbon has a very low surface functional group and is therefore highly hydrophobic, and has a small surface area such as disappearance of pores by high-temperature treatment, and also has a low water retention. Therefore, the water repellency of carbon can be maintained over a long period of time without increasing the thickness of the catalyst layer or decreasing the conductivity.

  Here, the graphitization temperature is not particularly limited as long as a desired graphitized layer can be formed on the carbon surface. The graphitizing temperature is preferably 2000 ° C. or higher, preferably 2000 to 3000 ° C., more preferably 2400 to 2800 ° C., although suitable temperature conditions vary slightly depending on the type of carbon. If it is less than 2000 degreeC, it cannot be said that formation of the graphitization layer on a carbon surface is enough, and there exists a possibility that desired water repellency and corrosion resistance may not fully be obtained. The graphitization time is not particularly limited as long as a desired graphitized layer can be formed on the carbon surface. The graphitization treatment is preferably performed in an inert gas atmosphere such as nitrogen, argon, or helium.

Among the graphitized carbons, graphitized acetylene black (GrAB), graphitized furnace black (GrFB), graphitized vulcanized (GrVul), graphitized kettle having a graphitization rate of 85% or more and a BET surface area of less than 150 m ² / g. Graphitized carbon (graphitized carbon) such as chain black (GrKB) is suitable, but is not limited thereto. These carbons with high water repellency may be used alone or in combination of two or more.

As described above, the carbon having high water repellency is desirably graphitized carbon having a BET surface area of less than 150 m ² / g, more preferably 50 to 140 m ² / g, and particularly preferably 80 to 130 m ² / g. . When two or more types of carbon having high water repellency are used in combination, the BET surface area of each carbon needs to satisfy the range specified above. When the BET surface area of graphitized carbon is less than 150 m ² / g, the surface functional groups are remarkably small, so that the hydrophobicity is high, the surface area is small, and the water retention is small. Therefore, the water repellency of carbon can be maintained over a long period of time without increasing the thickness of the catalyst layer or decreasing the conductivity.

Further, high water repellent carbon, lattice constant _{C 0} value of X-ray diffraction (Å) is 7.0Å or less, are preferably 6.7～7.0A, more preferably 6.8~6.9Å . In an ideal graphite, C ₀ = 6.707 、. For example, in the case of graphitized carbon produced under the graphitization treatment conditions (temperature and time) of the examples, each C ₀ value is GrAB = 6.853 そ れ ぞ れ. GrFB = 6.852Å, GrVul = 6.851Å, and GrKB = 6.879. The lattice constant C ₀ value of the X-ray diffraction may be measured, for example, by the Gakushin method (Michio Inagaki, Carbon No. 36, 25-34 (1963)) using an X-ray diffraction method (XRD). Alternatively, it may be determined from the lattice spacing (d ₀₀₂ ) measured by the same method (meaning the hexagonal mesh spacing based on the graphite structure of conductive carbon). That is, the lattice spacing d ₀₀₂ of carbon is the spacing of the hexagonal mesh plane based on the graphite structure of carbon, and is the ½ interlayer distance of the lattice constant C _{0 in} the c-axis direction that is perpendicular to the hexagonal mesh plane. Mean value.

Carbon graphitized by heat treatment, etc. has a graphitized layer consisting of a three-dimensional crystal lattice resembling the graphite structure on the surface, and as the graphitization proceeds, the fine voids between the crystal lattices decrease, and the carbon material The crystal structure approaches that of graphite. In consideration of corrosion resistance and the like, it is preferable that the graphitized carbon has a high crystallinity. Therefore, when the true density of graphitized carbon is less than 1.80 g / cm ³ and the lattice spacing d ₀₀₂ exceeds 3.50 mm, there are many cases where the graphite structure is not sufficiently developed, and high corrosion resistance. There is a risk that electronic conductivity may not be obtained. Further, when the true density exceeds 2.11 g / cm ³ and the lattice spacing d ₀₀₂ is less than 3.36 mm, the graphite structure is often developed, and there is a possibility that a sufficient specific surface area cannot be obtained.

Accordingly, it is preferable to use graphitized carbon having a true density of 1.80 to 2.11 g / cm ³ and a lattice spacing d ₀₀₂ of 3.36 to 3.50 mm, more preferably The true density is 1.90 to 2.11 g / cm ³ and the lattice spacing d ₀₀₂ is 3.40 to 3.49 mm, and the true density is particularly preferably 2.0 to 2.11 g / cm ³ and the lattice spacing. It is preferable to use one having d ₀₀₂ of 3.42 to 3.49 mm.

In the present invention, the true density is a value measured by a gas phase substitution method using helium, and the lattice spacing d ₀₀₂ is the Gakushin method using the X-ray diffraction method (Michio Inagaki, Carbon No. 36, 25- 34 (1963)).

  Next, the carbon having high hydrophilicity or low water repellency may be any carbon as long as it has lower water repellency than the carbon having high water repellency, and is used as a conventional conductive carbon carrier that has not been graphitized. You can use what you have. In other words, any material having higher hydrophilicity than carbon having high water repellency may be used. Specifically, carbon which is carbonized by heat treatment at 1000 ° C. or more and less than 2000 ° C. can be used. Depending on the carbonization temperature, a graphitized layer may be formed on a small part of the carbon surface to be obtained. Such a carbonized layer is included in highly hydrophilic carbon.

  The carbonization temperature is usually 1000 ° C. or higher and lower than 2000 ° C. If it is less than 1000 ° C., it is not sufficiently carbonized. On the other hand, if it is 2000 ° C. or more, the water repellency increases, but a surface area that is important for use as a carrier cannot be secured sufficiently.

The carbon having high hydrophilicity or low water repellency (also referred to simply as carbon having high hydrophilicity in this specification) preferably has a BET surface area of 150 m ² / g or more, preferably 250 to 2000 cm ² / g (graphite Carbon) is not preferred. When two or more kinds of highly hydrophilic carbons are used in combination, the BET surface area of each carbon needs to satisfy the range specified above. When the BET surface area of carbon is less than 150 m ² / g, it becomes difficult to control the dispersibility and particle size of the catalyst (Pt, etc.) particles and ensure high power generation performance.

  The carbon having high hydrophilicity is preferably carbon that is used as a normal highly conductive support from the viewpoint of controlling the dispersibility and particle size of catalyst particles such as platinum and ensuring high power generation performance. Examples thereof include Vulcan, Ketjen Black, Black Pearl, Acetylene Black, Furnace Black and the like used in Examples. These highly hydrophilic carbons may be used alone or in combination of two or more.

The carbon having high water repellency and the carbon having high hydrophilicity are distinguished by the thermal history (heat treatment temperature) during production, the BET surface area of carbon, the microscopic observation of carbon (lattice constant C ₀ of X-ray diffraction), etc. Discriminating). For example, at the manufacturing stage, the carbon type before the hydrophilic / hydrophobic carbon is in a mixed state (catalyst layer) (carbon distinguished according to different production conditions) can be determined by the BET surface area and Co value, The degree of graphitization can be measured, and hydrophilic carbon and hydrophobic carbon can be classified (discriminated) by these. In addition, when the product becomes a product, the presence or absence of a peak of crystalline carbon (graphite; graphite) and amorphous carbon (carbon other than graphite) and the intensity ratio are measured by Raman spectroscopy. Whether or not carbon is contained and the content ratio can be measured. That is, almost no peaks attributed to crystalline carbon are observed in hydrophilic carbon, and both peaks attributed to crystalline carbon and peaks attributed to amorphous carbon are observed in water-repellent carbon. There is also a method of measuring (calculating) whether or not the catalyst layer contains graphitized carbon based on the change in peak ratio (the peak intensity of crystalline carbon increases). . Furthermore, the product is divided into several parts in the thickness direction and the flow path direction, the catalyst layer is peeled off and sampled, and measured by Raman spectroscopy, etc., whether the catalyst layer contains graphitized carbon, There is also a method for calculating the content ratio.

  In the present invention, as described above, conventional carbon having high catalyst carrying ability and high conductivity (carbon having high hydrophilicity as described above) is used as the carbon powder carrying the catalyst. It is made of carbon with high water content. Therefore, the carbon having high water repellency may or may not be loaded with a catalyst, but from the viewpoint of increasing the amount of catalyst loaded, it is desirable that the catalyst component (noble metal) is also loaded on carbon having high water repellency. . The catalyst component is preferably a noble metal having high corrosion resistance (oxidation resistance) and excellent power generation performance.

  Therefore, in the present invention, the highly water-repellent carbon in the catalyst layer contains (supports) at least one catalyst noble metal component selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium. It is desirable. To improve both battery performance (initial power generation performance) and corrosion resistance, the mixing ratio of the hydrophilic carbon carrying the catalyst noble metal component and the water-repellent carbon carrying the catalyst noble metal component is set within the optimum range. This is necessary.

  From the viewpoint of performance, the average particle diameter of the catalyst supported on carbon having high water repellency is desirably in the range of 1 to 10 nm, preferably 2 to 6 nm. When it is less than 1 nm, the durability of the particles is poor, and when it exceeds 10 nm, the contact state with the ionomer is poor and the performance is low.

  In the present invention, the highly water-repellent carbon in the catalyst layer contains (supports) at least one or more types of catalytic noble metal components selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium, and further, Co, It contains at least one catalyst base metal component selected from the group consisting of Cr, Mn, Ni and Fe, and the supported amount of the noble metal / the supported amount of the base metal = 5/1 to 1/2, preferably 5/1 It is 1/1. This is because, in order to improve the battery performance (initial power generation performance) and the corrosion resistance and to achieve both, it is important that the catalyst component is also supported on the highly water-repellent carbon in the catalyst layer. The catalyst component is preferably a noble metal alloy having high corrosion resistance (oxidation resistance) and excellent power generation performance. However, the catalyst performance can be further improved by further containing an appropriate amount of a base metal component. Is advantageous. That is, when a noble metal and a base metal are used in combination, the average particle diameter of the noble metal alloy supported on carbon having high water repellency is desirably in the range of 1 to 10 nm, preferably 2 to 6 nm, from the viewpoint of performance. When the average particle diameter of the noble metal alloy is less than 1 nm, the durability of the particles is inferior, and when it exceeds 10 nm, the contact state with the ionomer is poor and the performance is low.

  Here, when the precious metal / base metal (composition ratio (molar ratio))> 5/1, the effect of adding the base metal does not appear, and when the precious metal / base metal (composition ratio (molar ratio)) <1/2. In contrast, the activity of noble metals is inhibited.

  In the present invention, the type and average particle size of the highly hydrophilic carbon and the catalyst particles supported thereon are not particularly limited, and can be appropriately selected from conventionally known ones.

  In the present invention, in order to achieve both the durability and catalytic performance of the electrode catalyst and to further reduce the decrease in the catalytic activity over time, the catalyst supported on carbon having high water repellency and carbon having high hydrophilicity. The particles are preferably supported by adjusting the average particle diameter. From this point of view, the average particle diameter of the catalyst particles in carbon having high water repellency is 1 to 10 nm, preferably 2 to 6 nm. If the average particle size is less than 1 nm, high catalytic activity can be obtained at the beginning of power generation, but durability may be inferior when used for a long period of time. If the average particle size exceeds 10 nm, the particle surface area of the catalyst particles becomes small, and On the contrary, there is a risk that the catalytic activity may decrease due to the poor contact state. On the other hand, the average particle diameter of the catalyst particles in the highly hydrophilic carbon is 1 to 10 nm, preferably 2 to 6 nm. If the average particle size is less than 1 nm, the decrease in the catalytic activity over time may not be sufficiently reduced. If the average particle size exceeds 10 nm, the particle surface area of the catalyst particles becomes small and the contact state with the ionomer becomes poor. On the other hand, the catalytic activity may decrease.

  Here, the “average particle diameter of the catalyst particles” refers to the average value of the particle diameter of the catalyst particles determined from the crystallite diameter or the transmission electron microscope image obtained from the half width of the diffraction peak of the catalyst particles in X-ray diffraction.

  In the electrode catalyst of the present invention, the supported amount of catalyst particles in the highly water-repellent carbon is 10 to 70% by mass, preferably 20 to 60% by mass, based on the total amount of catalyst particles used in the electrode catalyst. Preferably, the amount of catalyst particles in the highly hydrophilic carbon is 5 to 70% by mass, preferably 20 to 60% by mass, and more preferably 30 to 50% by mass.

  In order to further improve the durability and catalytic performance of the electrode catalyst, and to further reduce the decrease in the catalytic activity over time, it is supported on each of the carbon having high water repellency and carbon having high hydrophilicity. The supported amount of catalyst particles is preferably within the above-mentioned range.

  If the supported amount of carbon having a high water repellency is less than 10% by mass, high catalytic activity may not be obtained at the beginning of power generation, and if it exceeds 70% by mass, the amount of supported catalyst particles is too large. There is a risk that the catalyst activity may be reduced due to the catalyst particles overlapping each other.

  If the supported amount in the highly hydrophilic carbon is more than 70% by mass, the amount of the supported catalyst particles is too large and the catalyst particles may be overlapped with each other. If it is, there is a possibility that the decrease in the catalytic activity over time cannot be made sufficiently small.

  In the electrode catalyst of the present invention, in order to further improve the durability and catalyst performance of the electrode catalyst, the catalyst particles are supported on the highly water-repellent carbon, and the catalyst particles are supported on the highly hydrophilic carbon. Two types of catalyst slurries having different compositions may be formed by mixing them at a predetermined ratio.

  That is, the electrode catalyst of the present invention includes an electrode catalyst (C) in which the catalyst particles are supported on the highly water-repellent carbon, and an electrode catalyst (D) in which the catalyst particles are supported on the highly hydrophilic carbon. ) And a mass ratio (D) / (C) of 4/1 to 1/2, preferably 3/1 to 1/2, more preferably 2/1 to 1/1. May be used. When used in the above range, if the mass ratio (D) / (C) to which the electrode catalyst (C) and the electrode catalyst (D) are mixed exceeds 4/1, sufficient durability cannot be obtained. If the ratio is less than ½, the catalyst performance may be lowered. However, it goes without saying that the carbon mixture composition having high water repellency and the carbon mixture composition having high hydrophilicity may have a region not necessarily within the above range depending on the purpose of use. That is, in order to form a drainage channel in the catalyst layer, it may be more effective to use water-repellent carbon alone. This is because the hydrophilic part (island-like part) may be more effective when used alone from the viewpoint of enhancing the electrode reaction.

  The highly hydrophilic carbon used in the electrode catalyst of the present invention is preferably one having a conductivity of 1 to 10 S / cm. Highly hydrophilic carbon is used as an electrocatalyst for high-performance fuel cells, so it not only supports catalyst particles but also functions as a current collector for taking electrons into or taking them out of the external circuit. That is required. If the electrical conductivity of the highly hydrophilic carbon is less than 1 S / cm, the internal resistance of the fuel cell may be increased, leading to a decrease in cell performance, and if it exceeds 10 S / cm, the catalytic activity may be decreased. . On the other hand, carbon having a high water repellency is preferably used with a conductivity of 10 to 1000 S / cm. If the conductivity of the carbon having high water repellency is less than 10 S / cm, the durability may be lowered, and if it exceeds 1000 S / cm, the catalytic activity may be lowered.

  Next, the catalyst particles supported on the highly hydrophilic carbon may be any catalyst particles that exhibit a catalytic action for the hydrogen oxidation reaction and / or the oxygen reduction reaction. For example, at least one or more kinds of noble metals selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium can be mentioned. In particular, platinum can be used alone as catalyst particles because of its high catalytic activity. However, for the purpose of improving heat resistance, poisoning resistance to carbon monoxide, etc., at least one base metal selected from chromium, manganese, iron, cobalt, nickel, or iridium and a noble metal such as platinum. It may be used as an alloy.

  Even in the catalyst particles supported on carbon having high hydrophilicity, the mixing ratio of the noble metal and the base metal in the alloy is platinum / base metal in a mass ratio of 1/1 to 5/1, particularly 2/1 to 4/1. It is preferable to do this. Thereby, it can be set as the catalyst particle which has poisoning resistance, corrosion resistance, etc., maintaining high catalyst activity.

  The catalyst particles are supported on the highly water-repellent carbon and the highly hydrophilic carbon by impregnation method, liquid phase reduction support method, evaporation to dryness method, colloid adsorption method, spray pyrolysis method, reverse micelle method (micro micelle method) Any method generally used in the past may be used, such as an emulsion method.

  The catalyst layer includes a polymer electrolyte such as an ion exchange resin in addition to the above-described carbon powder (carbon having high hydrophilicity) supporting catalyst particles and carbon having high or low water repellency supporting or not supporting catalyst particles. included. It is preferable that the ion exchange resin covers at least a part of the electrode catalyst as a binder polymer. Thereby, not only ion conductivity etc. can be improved, but an electrode structure can be maintained stably and electrode performance can be improved.

  The ion exchange resin is not particularly limited, and is a perfluorosulfonic acid polymer proton conductor such as a Nafion solution, a hydrocarbon polymer compound doped with an inorganic acid such as phosphoric acid, partly a proton conductor And organic / inorganic hybrid polymers substituted with the above functional groups, and ion exchange resins made of proton conductors in which a polymer matrix is impregnated with a phosphoric acid solution or a sulfuric acid solution.

Specific examples of perfluorosulfonic acid polymer proton conductors include not only polymers composed of only carbon atoms and fluorine atoms, but also oxygen atoms if all hydrogen atoms are replaced with fluorine atoms. and the _like, CF 2 = polymerized units based on CF ₂ and _{CF 2 = CF- (OCF 2 CFX} ) m -O p - (CF 2) n -SO 3 polymerized units (in the formula based on H, X is fluorine An atom or a trifluoromethyl group, m is an integer of 0 to 3, n is an integer of 1 to 12, and p is 0 or 1.).

  The catalyst layer may contain a water-repellent polymer such as polytetrafluoroethylene, polyhexafluoropropylene, and tetrafluoroethylene-hexafluoropropylene copolymer. Thereby, the water repellency of the resulting catalyst layer can be increased, and water generated during power generation can be quickly discharged.

  Next, the gas diffusion layer is not particularly limited, but includes a porous base material based on a sheet-like material having conductivity and porosity, such as a carbon woven fabric, a paper-like paper body, a felt, and a non-woven fabric. Can be mentioned. Similarly to the catalyst layer, in the gas diffusion layer, in order to increase water repellency and prevent flooding phenomenon, the gas diffusion layer is subjected to water repellency treatment using known means, or carbon particle aggregates are formed on the gas diffusion layer. A body layer may be formed.

  The polymer electrolyte fuel electrode of the present invention can be used as an MEA by further sandwiching a polymer electrolyte membrane between a pair of electrodes (anode and cathode).

  The polymer electrolyte membrane that can be used for the MEA is not particularly limited, and examples thereof include a membrane made of an ion exchange resin. Since the ion exchange resin is the same as that described in the catalyst layer of the present invention, detailed description thereof is omitted here. The same ion exchange resin may be used for the electrode catalyst layer and the solid polymer electrolyte membrane, or different ones may be used, but the same one is preferably used in consideration of ion conductivity and the like. Examples of the polymer electrolyte membrane include various types of Nafion (DuPont registered trademark: NAFION) manufactured by DuPont, perfluorosulfonic acid membranes represented by Flemion, ion exchange resins manufactured by Dow Chemical, and ethylene-tetrafluoroethylene. Commercially available products such as fluoropolymer electrolytes such as fluorinated ethylene copolymer resin films and resin films based on trifluorostyrene, and hydrocarbon-based resin films having sulfonic acid groups may be used.

  In the fuel cell electrode having the MEA configuration of the present invention, the catalyst layer, the gas diffusion layer, and the polymer electrolyte membrane are desirably thin to improve the diffusibility of the fuel gas, but are too thin. A sufficient electrode output cannot be obtained. Therefore, it may be determined as appropriate so that an MEA having desired characteristics can be obtained.

  The above-mentioned MEA is suitably used as a fuel cell. As the type of the fuel cell, a solid polymer electrolyte fuel cell (PEFC) is preferably mentioned from the viewpoints of practicality and safety.

  The structure of the fuel cell is not particularly limited, and examples thereof include a structure in which MEAs are stacked with a separator (see FIG. 1).

  The separator may be any commonly used material such as carbon paper or carbon cloth. Further, the separator has a function of separating air and fuel gas, and a gas flow groove may be formed in order to secure a flow path thereof, and a conventionally known technique can be appropriately used. it can. The thickness and size of the separator are not particularly limited, and may be appropriately determined in consideration of the output characteristics of the obtained fuel cell.

  Furthermore, a stack in which a plurality of MEAs are stacked via a separator and connected in series may be formed so that the fuel cell can obtain a desired voltage or the like. The shape of the fuel cell is not particularly limited, and may be determined as appropriate so that desired battery characteristics such as voltage can be obtained.

  Since the fuel cell electrode of the present invention is excellent in power generation performance and durability, it can exhibit excellent characteristics over a long period of time. Therefore, the MEA and the fuel cell using such a fuel cell electrode can exhibit superior performance as compared with the conventional one. Therefore, the efficiency of the fuel cell system can be improved, and the fuel cell system is useful as a stationary power source, a power source for moving bodies such as vehicles.

  Hereinafter, the present invention will be specifically described based on examples. In addition, this invention is not limited only to these Examples.

Example 1
In carrying out the present invention, a cathode catalyst layer was formed. First, an electrode catalyst slurry (hydrophilic slurry) for preparing a hydrophilic portion in the cathode catalyst layer was prepared. Using ketjen black (Pt supported amount: 50 wt%) having a BET surface area of 800 m ² / g to which Pt fine particles having a particle diameter of about 2 to 3 nm are attached as an electrode catalyst, pure water and a proton exchange membrane are used as the electrode catalyst powder. An electrolyte solution in which the electrolyte of the same component was dissolved (Nafion solution, registered trademark of DuPont) and a lower alcohol such as isopropanol were added, and refined and mixed with a homogenizer to prepare a hydrophilic slurry. Next, graphitized ketjen black (Pt supported amount: 50 wt%) having a BET surface area of 120 m ² / g to which Pt fine particles having a particle diameter of about 2 to 3 nm are attached is used as an electrode catalyst. A Nafion solution and isopropanol were added, and the water-repellent slurry was prepared by pulverization and mixing as described above.

  The catalyst slurry was applied to the Teflon (registered trademark) sheet using the screen slurry of the hydrophilic slurry and the water-repellent slurry prepared by the above-described method to form a catalyst layer on the Teflon (registered trademark) sheet. When forming this catalyst layer, two types of screen meshes are used, one is a mesh for applying a hydrophilic slurry, the applicable part is a square, and the other is a mesh for applying a water-repellent slurry. The coatable portion has a lattice shape so as to fill the square gap (see FIG. 2). The two types of slurries were applied alternately using the two types of meshes until the target Pt usage amount was reached. The amount of Pt used was 0.4 mg / cm. The thickness of the cathode catalyst layer was about 20 μm.

  Next, an anode catalyst layer was formed. Using the hydrophilic slurry, a catalyst layer was formed by applying it onto a Teflon (registered trademark) sheet with a screen printer. The anode catalyst layer had a thickness of about 20 μm.

  The anode catalyst layer and the cathode catalyst layer were transferred to an electrolyte membrane (Nafion membrane, manufactured by DuPont, thickness: 25 μm) by hot pressing to form a membrane-electrode assembly.

  In Example 1, ketjen black is used as the catalyst carrier used in the hydrophilic slurry. However, the present invention is not limited to this, and vulcanized or black pearl may be used. Carbon used in water repellent slurry. Graphitized Vulcan, Graphitized Acetylene Black, Graphitized Furnace Black, etc. may be used. Furthermore, although a rectangular lattice-like geometric pattern was used for the shape of the hydrophilic portion in the catalyst layer surface (see FIG. 2), it is not limited to such a geometric pattern. (Not shown), a rhombus, or the like (see FIGS. 3 to 7).

Example 2
A cathode catalyst layer was formed on a Teflon (registered trademark) sheet by the following procedure.
Using the slurry and screen printing mesh used in Example 1, a catalyst layer having a thickness of about 10 μm was formed in a pattern similar to Example 1 on a Teflon (registered trademark) sheet. did. Subsequently, a catalyst layer was further formed on the catalyst layer 1 having a thickness of about 10 μm. At this time, two new meshes were used. One is a quadrangle in which the coatable part is a square (the number of squares exceeds the square area of Example 1 and the number of squares is the same), and the other is a lattice shape that fills the gaps of the squares. Using these two new types of meshes, two types of slurry were applied, and the application of the slurry was repeated until the amount of Pt used reached 0.4 mg / cm ² . The newly applied catalyst layer was designated as catalyst layer 2 (see FIG. 8). The total thickness of the catalyst layer at this time was about 20 μm.

  The cathode catalyst layer and the anode catalyst layer prepared in Example 1 were transferred to a Nafion film (thickness: 25 μm) by hot pressing to form a membrane-electrode assembly.

  In Example 2, a quadrangle is adopted as the shape of the hydrophilic portion in the catalyst layer. However, in the present invention, the shape is not limited to a quadrangle.

Example 3
In the cathode side catalyst layer, a catalyst layer was formed in which the hydrophilic portion increased from the gas outlet side to the inlet side. In this example, the catalyst layer was divided into four parts (see FIG. 9, but note that the reference numerals in the figure and the reference numerals used in the following description of this example are slightly different). The four divisions are divided into four equal parts, the portion closest to the gas outlet is the catalyst layer 1-1 ′, the portion closest to the gas inlet is the catalyst layer 1-3 ′, and the other portion is the catalyst layer 1-2 ′. And Screen meshes for forming the three types of catalyst layers are hydrophilic part meshes 1-1 ′, 1-2 ′, 1-3 ′ (catalyst layers 1-1 ′, 1-2 ′, 1-3). Used for the water repellent portion 1-1 ′, 1-2 ′, and 1-3 ′ (used for the catalyst layers 1-1 ′, 1-2 ′, and 1-3 ′). The hydrophilic portion mesh has a quadrangular shape, and the same number of the quadrangles are arranged, and the area of the square is hydrophilic portion mesh 1-1 ′ <hydrophilic portion mesh 1-2 ′ <hydrophilic portion use. The relationship is mesh 1-3 ′. Further, the water repellent part mesh has a groove structure that fills the square gap of the corresponding hydrophilic part mesh. The catalyst layer 1-1 ′ is formed using the hydrophilic portion mesh 1-1 ′ and the water repellent portion mesh 1-1 ′, and the catalyst layer 1-2 ′ and the catalyst layer 1-3 ′ are formed in the same manner. And a catalyst layer was formed on the Teflon (registered trademark) sheet. The amount of Pt used in the catalyst layer at this time was 0.4 mg / cm ² , and the thickness of the catalyst layer was about 20 μm.

  The cathode catalyst layer and the anode catalyst layer produced by the same means as in Example 1 were transferred to a Nafion film (25 μm) by hot pressing to form a membrane-electrode assembly.

  Also in the third embodiment, a quadrangular shape is adopted as the shape of the hydrophilic portion within the full catalyst layer. However, in the present invention, the shape is not limited to a quadrangular shape.

Example 4
Using the same means as in Example 3, a similar catalyst layer was formed on a Teflon (registered trademark) sheet (referred to as catalyst layer A). However, the amount of Pt used in the catalyst layer was about 0.2 mg / cm ² and the thickness was about 10 μm. Next, a new catalyst layer was formed on the formed catalyst layer (referred to as catalyst layer B). Note that this is slightly different.) This newly formed catalyst layer is divided into four parts in the same manner as the base catalyst layer, the catalyst layer closest to the gas outlet is the catalyst layer 2-1 ', and the catalyst layer closest to the gas inlet is the catalyst layer. The catalyst layer 2-3 ′ and the other part are referred to as a catalyst layer 2-2 ′.

  Moreover, in the screen mesh for forming this catalyst layer 2-1 ', 2-2', 2-3 ', the hydrophilic part in each catalyst layer is made into the hydrophilic part mesh 2-1', 2-2 '. The water-repellent portion was formed of the water-repellent portion meshes 2-1 ′, 2-2 ′, and 2-3 ′. At this time, in the hydrophilic portion mesh, the coatable portion has a square shape, and the coatable portion in the water repellent portion mesh has a groove structure that fills the square gap of the hydrophilic portion. Further, in the hydrophilic portion mesh, the area of the quadrangle is hydrophilic portion mesh 2-1 ′ <hydrophilic portion mesh 2-2 ′ <hydrophilic portion mesh 2-3 ′. Hydrophilic part mesh 2-1 '> Hydrophilic part mesh 1-1, Hydrophilic part mesh 2-2'> Hydrophilic part mesh 1-2, Hydrophilic part mesh 2-3 '> Hydrophilic The partial mesh 1-3 is related.

Using the hydrophilic part meshes 2-1 ', 2-2', 2-3 'and the water repellent part meshes 2-1', 2-2 ', 2-3' as described above, the catalyst layer 1 A catalyst layer 2 (catalyst layer B) was newly formed on (catalyst layer A). At this time, catalyst layer 1 + catalyst layer 2 was one cathode catalyst layer, the total amount of Pt used was 0.4 mg / cm ² , and the thickness was about 20 μm.

  The cathode catalyst layer and the anode catalyst layer produced by the same means as in Example 1 were transferred to a Nafion film (25 μm) by hot pressing to form a membrane-electrode assembly.

  Also in Example 4, a quadrangular shape is adopted as the shape of the hydrophilic portion within the catalyst layer. However, in the present invention, the shape is not limited to a quadrangular shape.

Comparative Example 1
A catalyst layer was formed on a Teflon (registered trademark) sheet by a screen printer using a screen mesh without a pattern, using the hydrophilic slurry prepared in Example 1. Two such catalyst layers were prepared. The membrane-electrode assembly was formed by transferring to the Nafion film by the hot press thus prepared.

<Power generation test>
A fuel cell single cell was produced using the MEA including the polymer electrolyte fuel electrode obtained in each of Examples 1 to 4 and Comparative Example 1, and the performance of the fuel cell single cell was measured. In the MEA used in this example and the comparative example, the area of the electrode (catalyst layer) portion was set to 100 cm ² .

The performance measurement of the obtained fuel cell single cell was as follows. In the measurement, hydrogen was supplied as fuel to the anode side, and air was supplied to the cathode side. The supply pressure of both gases is atmospheric pressure, hydrogen is 58.6 ° C., air is saturated and humidified at 55 ° C., the temperature of the fuel cell body is set to 70 ° C., the hydrogen utilization rate is 70%, and the air utilization rate is 40. %, The operation was continued for 30 minutes at a current density of 1.0 A / cm ² . When power generation was stopped, the current density taken out was set to zero, and then the anode was purged with air to discharge hydrogen. The cathode was opened at the outlet side at atmospheric pressure. At this time, temperature control of the fuel cell body was not performed, and the stop time was 30 minutes. When restarting operation after stopping, gas was again introduced into the cell under the above conditions to generate power. By repeating this start-stop cycle, the durability of the single fuel cell was evaluated. The results are shown in Table 1 below.

FIG. 11 shows the number of start-stop cycles of cell voltage at a current density of 1.0 A / cm ² for each solid polymer electrolyte fuel cell configured using MEAs including solid polymer fuel electrodes of Examples and Comparative Examples. It is a graph showing the change with respect to. As shown in FIG. 11, the fuel cell using the MEA (Example) including the polymer electrolyte fuel electrode of the present invention used the MEA (Comparative Example) including the conventional polymer electrolyte fuel electrode. It was confirmed that the cell voltage decrease rate was smaller than the number of start / stop cycles from the start of operation, compared to the fuel cell.

  In Examples 3 to 4 in Table 1, the catalyst layer 1 and the catalyst layer 2 are formed in a form corresponding to FIGS. 9 to 10, and each catalyst layer surface is equally divided into four sections. The ratio of the area X of the groove structure having water repellency in these sections to the area Y of the island-shaped part having hydrophilicity is different as shown in Table 1 above. It is.

  On the other hand, the catalyst layer of Example 1 is one layer, and the whole catalyst layer has X / Y = 1 in a form corresponding to FIG. 2. In addition, the catalyst layer surface is equally divided into four sections as in Examples 3 and 4, and the X / Y ratio is not different for each section. The catalyst layer is not a two-layer structure.

  Similarly, the catalyst layer of Example 2 has a catalyst layer 1 and a catalyst layer 2 in a form corresponding to FIG. 8, and is formed so that the X / Y ratio is different for each catalyst layer. That is, the entire catalyst layer 1 is X / Y = 1 and the entire catalyst layer 2 is X / Y = 0.67, but in Table 1 above, for convenience, it is shown together with the sections of Examples 3 to 4 Therefore, as in Examples 3 and 4, the catalyst layers are equally divided into four sections so that the X / Y ratio is different, and the X / Y ratio is not different for each section.

It is the schematic perspective view decomposed | disassembled and shown for every basic structure of the fuel cell containing the polymer electrolyte fuel electrode of this invention. 1 is a schematic plan view of a catalyst layer showing an example (an embodiment corresponding to Example 1; pattern 1) in which a geometric pattern in a catalyst layer surface of the polymer electrolyte fuel electrode of the present invention is a lattice pattern; . In the geometric pattern in the catalyst layer surface of the polymer electrolyte fuel electrode of the present invention, an example is shown in which the island portion having hydrophilicity is circular and the water-repellent portion surrounds the gap (pattern) It is a plane schematic diagram of the catalyst layer showing 2). In the geometric pattern in the catalyst layer surface of the solid polymer fuel electrode of the present invention, the island-like portion having hydrophilicity has a rhombus shape, and the gap has a groove structure having water repellency. It is the plane schematic of the catalyst layer which shows the example (pattern 3) which the part surrounds. In the geometric pattern in the catalyst layer surface of the solid polymer fuel electrode of the present invention, the island-like portion having hydrophilicity has a triangular shape, and the gap has a groove structure having water repellency. It is the plane schematic of the catalyst layer which shows the example (pattern 4) which the part surrounds. In the geometric pattern in the catalyst layer surface of the polymer electrolyte fuel electrode of the present invention, the island portions having hydrophilicity are present in an irregular shape (indefinite shape) in an island shape, and the gaps are formed. It is the plane schematic diagram of the catalyst layer which shows the example (pattern 5) where the part of the groove structure which has water repellency surrounds. In the geometric pattern in the catalyst layer surface of the solid polymer fuel electrode of the present invention, the hydrophilic portion and the water-repellent portion are in a lattice shape, and the rectangular hydrophilic portion is dotted in an island shape, and the gaps are formed. It is the plane schematic diagram of the catalyst layer which shows the example (pattern 6) where the part of the groove structure to fill is water-repellent. In the polymer electrolyte fuel electrode of the present invention, the cathode side catalyst layer is composed of two layers, and the catalyst layer on the electrolyte membrane side has more hydrophilic islands so as to satisfy the formula (1). It is explanatory drawing which shows the example which is small and the groove | channel of the water-repellent part is large (this is an embodiment corresponding to Example 2). In order to satisfy the formula (2) in the solid polymer type fuel electrode of the present invention, the catalyst layer divided into four by the difference in the area occupied by the water-repellent part and the hydrophilic part in the catalyst layer surface leads to the gas outlet side. It is explanatory drawing which shows the example of the catalyst layer formed so that the near side was smaller than the side near the gas inlet side, and the island of the hydrophilic part was small, and the groove | channel of the water-repellent part was enlarged (corresponding to Example 3). Embodiment). In the polymer electrolyte fuel electrode of the present invention, the catalyst layer surface is divided into four parts depending on the occupied area of the water-repellent part and the hydrophilic part so that the formula (2) is satisfied. The catalyst layer has a higher water repellency than the vicinity, and the side catalyst layer is composed of two layers, and the side closer to the electrolyte membrane has a higher water repellency than the GDL side so as to satisfy the formula (1). It is explanatory drawing which shows the example of (It is embodiment corresponding to Example 4). The change of the cell voltage with respect to the number of start-stop cycles at a current density of 1.0 A / cm ² of each solid polymer electrolyte fuel cell configured using MEAs including the solid polymer fuel electrodes of Examples and Comparative Examples is shown. It is a graph.

Explanation of symbols

10 Fuel cell,
11 Polymer electrolyte membrane,
12a catalyst layer on the anode side,
12b Cathode side catalyst layer,
13a A gas diffusion layer on the anode side,
13b cathode side gas diffusion layer,
14a anode,
14b cathode,
15 MEA,
16a A fuel gas flow path on the anode side,
16b Reaction gas flow path on the cathode side,
17 Separator.

Claims (9)

In the catalyst layer, it consists of two configurations having a geometric pattern, one is dotted with islands, and one has a groove structure that fills the gaps in the islands,
The solid polymer fuel electrode is characterized in that the island-shaped portion has hydrophilicity and the groove-structure portion has water repellency.   2. The polymer electrolyte fuel electrode according to claim 1, wherein the catalyst layer is composed of at least two layers from the electrolyte membrane side toward the gas diffusion layer side. In the catalyst layer composed of two or more layers, the catalyst layer in the catalyst layer closest to the electrolyte membrane is the catalyst layer 1, the next catalyst layer is the catalyst layer 2, and the catalyst layer closest to the gas diffusion layer is the catalyst layer. N (N is the number of layers constituting the entire catalyst layer),
The area of the groove structure portion having water repellency in each of the catalyst layers 1 to N is X1, X2,... XN, and the area of the island-shaped portion having hydrophilicity in each catalyst layer (X1 / Y1)> (X2 / Y2)>... (XN / YN), where Y is Y1, Y2,... YN. Polymer fuel electrode.   In the catalyst layer composed of two or more layers, the drainage channel of the groove structure having water repellency of the next catalyst layer is provided on the drainage channel of the groove structure having water repellency. The solid polymer fuel electrode according to any one of claims 1 to 3, wherein the solid polymer fuel electrode is provided. In the catalyst layer, the catalyst layer is divided into at least four parts in the plane, the catalyst layer in the portion closest to the gas outlet is the catalyst layer 1 ′, the catalyst layer adjacent to the catalyst layer 1 ′, and When the catalyst layer closest to the gas inlet is the catalyst layer N ′ (N ′ represents the number of the catalyst layers divided in the plane),
The area of the groove structure portion having water repellency in each of the catalyst layers 1 ′ to N ′ is defined as X1 ′, X2 ′,. Further, assuming that the area of the island-like portion having hydrophilicity in each catalyst layer is Y1 ′, Y2 ′,..., YN ′, (X1 ′ / Y1 ′)> (X2 ′ / Y2 ′) The solid polymer fuel electrode according to any one of claims 1 to 4, wherein: (XN '/ YN'). Both the island-like portion having hydrophilicity and the groove-structure portion having water repellency in the catalyst layer are carbon having high water repellency and carbon having high hydrophilicity or low water repellency. Formed without mixing,
The island-like portion having hydrophilicity is formed using carbon having high hydrophilicity or low water repellency,
6. The polymer electrolyte fuel electrode according to claim 1, wherein the water-repellent groove structure is formed using carbon having high water repellency. . A blend of carbon having high water repellency and carbon having high hydrophilicity or low water repellency in the island-like portion having hydrophilicity and the groove structure portion having water repellency in the catalyst layer. Are formed with different ratios,
6. The solid polymer fuel electrode according to claim 1, wherein the front groove structure portion has a higher blending ratio of the carbon having a higher water repellency than the island-shaped portion. 8. The polymer electrolyte fuel electrode according to claim 6, wherein carbon having high water repellency in the catalyst layer is carbon graphitized with a BET surface area of less than 150 m ² / g. 9. The solid polymer type according to claim 6, wherein the carbon having high hydrophilicity or low water repellency in the catalyst layer is carbon having a BET surface area of 150 m ² / g or more. Fuel electrode.