JP5458801B2 - Fuel cell - Google Patents

Description

  The present invention relates to a fuel cell, and in particular, a fuel that exhibits high performance even when the catalyst layer cannot be sufficiently humidified due to restrictions on the use environment, or when low humidification operation is forced temporarily due to fluctuations in operating conditions. The present invention relates to a fuel cell having a gas diffusion electrode for a battery.

  The basic structure of the fuel cell according to the present invention is, for example, a structure of a general polymer electrolyte fuel cell, and a catalyst layer serving as an anode and a cathode is disposed with a proton conductive electrolyte membrane interposed therebetween. Then, a gas diffusion layer is further arranged on the outer side, and a separator is further arranged on the outer side to constitute a unit cell fuel cell. Normally, a single cell fuel cell is stacked according to the required output, and used as a stacked fuel cell.

In order to take out the current from the fuel cell having such a basic structure, an oxidizing gas such as oxygen or air is supplied to the cathode side from the gas flow path of the separator disposed on both the anode and the cathode, and hydrogen is supplied to the anode side. A reducing gas such as is supplied to the catalyst layer through the gas diffusion layer. For example, when using hydrogen gas and oxygen gas, the chemical reaction of H ₂ → 2H ⁺ + 2e ⁻ (E ₀ = 0V) occurring on the anode catalyst and O ₂ + 4H ⁺ + 4e occurring on the cathode catalyst ^- → The current is extracted using the energy difference (potential difference) of the chemical reaction of 2H ₂ O (E ₀ = 1.23V).

Therefore, a gas diffusion path through which oxygen gas or hydrogen gas can move from the gas flow path of the separator to the catalyst inside the catalyst layer, and protons (H ⁺ ) generated on the anode catalyst pass through the proton conductive electrolyte membrane and proton conduction paths that can be transmitted to the catalyst, more electrons generated on the anode catalyst (e ^-) is a gas diffusion layer, separator, electron transfer pathway capable of transmitting to the cathode catalyst through an external circuit, continuously without being separated respectively If they are not connected, current cannot be extracted efficiently.

  Inside the catalyst layer, generally, pores that are formed in the gaps between the materials and serve as gas diffusion paths, electrolyte materials that serve as proton conduction paths, and conductive materials such as carbon materials and metal materials that serve as electron conduction paths are continuously connected to each other. It is important to form a network.

  In addition, ion exchange resins typified by perfluorosulfonic acid polymers are used as polymer electrolyte materials for proton conducting paths in proton conducting electrolyte membranes and catalyst layers. These generally used polymer electrolyte materials exhibit high proton conductivity for the first time in a wet environment, and the proton conductivity decreases in a dry environment. Therefore, in order to operate the fuel cell efficiently, it is essential that the polymer electrolyte material is in a sufficiently wet state.

  As one of the water supply sources for the polymer electrolyte material to be in a sufficiently wet state, there is water generated at the cathode by power generation, and the generation amount depends on the load condition (current density). When power generation is stopped or during low-load operation, the amount of water produced is small, the polymer electrolyte material dries, proton conductivity tends to decrease, and the amount of water produced during high-load operation is large. Excess water that cannot be absorbed by the electrolyte material easily closes the pores serving as a gas diffusion path.

  A humidifier is generally used as a stable water supply source that does not depend on load conditions. A method of humidifying the gas to be supplied by passing it through water that has been previously kept at a constant temperature and a method of directly supplying water that has been kept at a constant temperature to the cell are used. However, for the purpose of setting the energy efficiency of the entire system high, it is preferable that there is no humidifier that consumes a certain amount of energy for heat retention. Also, the same is true for the purpose of making the whole system light and small, and it is preferable that there is no humidifier. Therefore, depending on the intended use of the fuel cell, a sufficient humidifier cannot be mounted on the system, and the electrolyte material may not be sufficiently humidified. Alternatively, even when a humidifier with sufficient humidification capacity is mounted in steady operation, it is inevitable that the vehicle will temporarily fall into a low humidification state at the time of start-up or load fluctuation.

  Thus, since it cannot always be used in a moist environment suitable for an electrolyte material, there is a strong demand for a catalyst layer for a fuel cell that can exhibit high performance under any load condition or humidification condition. Thus, a high-performance fuel cell that can be easily controlled and operated is desired.

  Conventionally, for the purpose of avoiding drying of the polymer electrolyte material, an electrolyte membrane has been conventionally used by using a hydrophilic component in the gas diffusion layer, the catalyst layer, or an intermediate layer disposed between the gas diffusion layer and the catalyst layer. In addition, a method for moisturizing the electrolyte material inside the catalyst layer has been proposed.

  Among these, as a proposal for imparting hydrophilicity to the catalyst layer, in Patent Document 1, in order to maintain high battery performance even when the humidification amount is reduced, hydrophilic particles such as zeolite and titania on the anode, It is disclosed that it is contained in a hydrophilic carrier. In Patent Document 2, as a fuel cell exhibiting excellent startability even in a low-temperature atmosphere, a conductive material (hydrophilic treatment) containing a moisture humectant in the catalyst layer of the anode and hydrophilized the moisture humectant. Carbon black etc.). Further, in Patent Document 3, hydrophilic particles carrying hydrophobic particles such as silica particles carrying Teflon (registered trademark) particles in a catalyst layer for the purpose of providing a fuel cell that can cope with a wide range of humidification conditions. Is disclosed.

In Patent Document 4, activated carbon is used as a catalyst carrier, and the surface area S _BET of the activated carbon by the BET method (Brunauer-Emmett-Teller specific surface area method) satisfies S _BET ≧ 1500 m ² / g and has a diameter of 2 nm or less. A fuel cell is proposed in which the ratio of the micropore surface area S _micro (m ² / g) to the total pore area S _total (m ² / g) satisfies S _micro / S _total ≧ 0.5. On the other hand, Patent Document 5 proposes a fuel cell using a carrier made of a carbon material partially containing mesoporous carbon particles as a catalyst carrier.

  Furthermore, in an environment where the fuel cell is actually used, it is known that a metal such as platinum as a catalyst component elutes or a carbon material used for a carrier corrodes due to start / stop or high load operation. Durability technology that prevents elution of metals such as platinum and carbon corrosion is also very important.

As measures for preventing the corrosion of the carbon material used as the catalyst support, the following techniques have been disclosed so far. For example, Patent Document 6 discloses that the peak intensity (I _D ) in the range of 1300 to 1400 cm ⁻¹ called D-band obtained from the Raman spectrum by heat treatment and the like, and 1500 to 1600 cm ⁻ called G-band ⁻ It is disclosed that a carbon material having a relative intensity ratio (I _D / I _G ) with a peak intensity (I _G ) in the range of ¹ adjusted to 0.9 to 1.2 is used as a catalyst support.

In Patent Document 7, the specific surface area of the carbon material used as the catalyst carrier is set to 800 m ² / g or more and 900 m ² / g or less, so that power generation performance is high, and high potential durability and fuel shortage durability are excellent. An electrode structure of a polymer electrolyte fuel cell is disclosed.

JP 2004-342505 A JP 2006-59634 A JP-A-2005-174835 JP 2006-155921 A JP 2004-71253 A JP 2008-41253 JP JP 2006-318707 A

  However, in Patent Documents 1 and 3, since the catalyst layer contains a material that is hydrophilic but does not have conductivity or proton conductivity, the transfer path of electrons or protons is interrupted, and the internal resistance is reduced. There was an increasing problem. In Patent Document 2, carbon black treated with nitric acid is used as a catalyst carrier as an example of a conductive material subjected to hydrophilic treatment. However, the degree of hydrophilicity (degree of hydrophilic treatment) is also suggested. It has not been done. According to the study by the inventors, simply including hydrophilic carbon black shows excellent water retention capability under low humidity conditions, but the gas diffusion path is condensed during high load operation or when sufficiently humidified. It became clear that the problem of water blockage occurred. In other words, depending on the degree of hydrophilicity, the water retention capacity may be insufficient, or the gas diffusion path may be blocked by water when the water retention capacity is too strong and the condition is sufficiently humidified. .

  Further, until now, the present inventors, the carbon material that is the main component of the catalyst layer, a carbon material carrying a catalyst component (hereinafter referred to as a catalyst carrier carbon material) and a carbon material not carrying a catalyst component (hereinafter referred to as a carbon material). The gas diffusion carbon material is contained in the catalyst layer separately, and at least two types of carbon materials having different hydration properties (hydration power) are used for the gas diffusion carbon material. A fuel cell having a catalyst layer for a fuel cell that can prevent the gas diffusion path from being clogged by condensed water even under high humidification conditions while maintaining the material in a suitable wet state at all times, that is, high regardless of humidification conditions We have developed a fuel cell that demonstrates its performance. The fuel cell is very effective for high and low load conditions under high and low humid conditions, and exhibits high performance under all conditions. Since it is an unsupported gas diffusion carbon material, the water retention effect of the electrolyte material in the vicinity of the catalyst is not necessarily sufficient, and a new improvement has been required to develop even higher characteristics.

  In that regard, the proposal using the activated carbon of Patent Document 4 that can be expected to maintain the water retention of the catalyst carrier is sufficient in terms of water retention in the vicinity of the catalyst particles, and the idea of ensuring gas movement with the gas diffusion carbon material is also However, assuming the aim of a higher-performance fuel cell, the activated carbon itself has a low electronic conductivity, and the hydrophilicity around the catalyst particles is so high that gas movement in the vicinity of the catalyst is hindered. There were problems such as. The proposal in which the mesoporous carbon of Patent Document 5 is a part of the catalyst carrier is mixed with a carbon material other than mesoporous carbon as the catalyst carrier, so that the gas diffusibility and the electron transfer property are higher than when the mesoporous carbon is used alone. Although improved, for example, during high load operation under high humidification conditions, there is a strong tendency for gas to become clogged by the generated water.To avoid this, lowering the mesoporous carbon ratio reduces the load particularly under low humidification conditions. During operation, the electrolyte in the vicinity of the catalyst on the carbon material other than mesoporous carbon was easily dried, and excellent characteristics could be exhibited only under limited conditions at a specific mixing ratio. In particular, carbon materials other than mesoporous carbon are expected to have a function of enhancing the diffusibility of the reaction gas. However, since carbon particles other than mesoporous carbon also have catalyst particles, they are used especially at the cathode during high-load operation. However, the water generated in the catalyst particles tends to hinder gas diffusion, and cannot be a universal catalyst layer under all conditions.

  On the other hand, as a measure for preventing the corrosion of the carbon material used as the catalyst carrier, as disclosed in Patent Documents 6 and 7, the degree of graphitization and surface area of the carbon material can be controlled. However, if the degree of graphitization is increased or the specific surface area is reduced, there is no doubt that the resistance to oxidation consumption is improved. However, even if the degree of graphitization and the specific surface area are the same, the resistance to oxidation consumption is high. In order to obtain a carbon material that is low and has a high resistance to oxidation exhaustion, it was necessary to clarify what caused it. Further, it has been found that increasing the degree of graphitization or reducing the specific surface area not only lowers the dispersibility of the catalyst particles, but also reduces the moisture retention and the fuel cell performance.

  Therefore, the present invention provides a catalyst layer for use in a fuel cell that is formed without dividing the movement paths of gas, electrons, and protons, and the electrolyte material in the catalyst layer is always formed under low humidification conditions or low load operation. A fuel cell having a catalyst layer for a fuel cell that can prevent the gas diffusion path from being clogged with condensed water even under high humidification conditions or high load operation while maintaining a suitable wet state, i.e., depending on the humidification conditions. It is an object of the present invention to provide a fuel cell that exhibits high performance. It is another object of the present invention to provide a fuel cell having a higher durability against oxidation consumption of a carbon material used as a catalyst carrier and more excellent in durability.

  In order to solve the above problems, paying attention to the water retention capacity in the catalyst layer used in the fuel cell, the material properties and higher order structure of the catalyst component, the electrolyte material, and the carbon material are examined and supported on the catalyst carrier. The catalyst layer structure was designed so that the catalyst worked well under all conditions. That is, a carbon material that is a component of the catalyst layer, a catalyst carrier carbon material that supports the catalyst component, a gas diffusion carbon material that does not support the catalyst component, a conductive auxiliary agent carbon material that does not support the catalyst component, The catalyst carrier carbon material is divided into the catalyst carrier carbon material A and the catalyst carrier carbon material A has high water retention and can easily store water generated by power generation or water supplied by humidification, and has excellent electron conductivity and gas diffusion. It was found that when used separately in combination with the catalyst support carbon material B having the characteristics that it is easy to perform, an excellent function of exhibiting high performance regardless of humidification conditions and load conditions can be expressed.

  Further, a catalyst layer containing a catalyst carrier carbon material A with high water retention is used as an inner layer on the electrolyte membrane side, and an outer layer mainly composed of a catalyst carrier carbon material B having a structure developed on the opposite side of the electrolyte membrane across the inner layer. It has been found that an excellent function of exhibiting high performance regardless of humidification conditions and load conditions can be expressed by using a catalyst layer having at least a two-layer structure.

  By adopting such a two-layer structure, the water retention water containing the supplied water or the generated water in the inner layer while the outer layer whose gas diffusion path is difficult to block with water mainly works at the time of high humidification conditions or high load operation. It is stored in the catalyst support carbon material A having a pore structure that is easy to form, and under low humidification conditions or low load conditions, the water stored in the catalyst support carbon material A prevents the electrolyte material in the catalyst layer from being dried, The decrease can be suppressed.

  Further, a carbon material having a pore structure that is easy to retain water, such as the catalyst support carbon material A, generally has insufficient electron conductivity and is often a simple particle. If the inner layer is composed of only the material, the electron conduction resistance increases, and the pores that serve as gas diffusion paths are difficult to develop. To compensate for this, carbon materials with high electron conductivity and developed structures are selected as the conductive auxiliary agent carbon material and coexisted in the catalyst support carbon material A and the catalyst layer. It was also found that the internal resistance rise due to the electron conduction resistance and the blockage of the gas diffusion path by water can be effectively suppressed during the load operation.

  Further, in each of the inner layer and the outer layer, a catalyst aggregation phase formed by aggregating the catalyst component, the catalyst-supporting carbon material A or B, and the electrolyte material, and a gas diffusion carbon material aggregation formed by aggregating the gas diffusion carbon material If the catalyst-aggregated phase is used as a continuous phase and the gas-diffused carbon material aggregated layer phase is dispersed in the catalyst-aggregated phase, high performance is exhibited regardless of humidification conditions and load conditions. It has been found that an excellent function of performing can be expressed.

  By adopting the structure of the catalyst layer, the electrolyte material is present in the vicinity of the catalytic carbon material, preventing a decrease in the moisture content under dry conditions, and by making the electrolyte material a continuous phase, Develop a network of electrolyte materials to prevent internal resistance rise due to proton conductivity. Further, as described above, the gas diffusion path is ensured by dispersing the gas diffusion carbon material aggregated phase in the continuous phase of the catalyst aggregated phase. Since no catalyst component is present in the gas diffusion carbon material aggregation phase, water is not generated in the gas diffusion material aggregation phase during power generation, and therefore, a gas diffusion path can be more effectively secured. . In addition, since the gas diffusion carbon material aggregated phase does not use a fluorine compound or the like that does not have electron conductivity, a gas diffusion path can be secured without dividing the electron conduction path. Further, since the gas diffusion carbon material aggregate phase is an independent aggregate phase that does not contain an electrolyte substance or a catalyst component, a carbon material having a low water vapor adsorption characteristic is used as the gas diffusion carbon material forming the aggregate phase. Since the water repellency inherent in the surface can be utilized, a gas diffusion path can be effectively secured.

  As described above, a plurality of carbon materials used in the catalyst layer are selected according to the function for which the catalyst layer is required, and the layer structure and agglomeration so that the catalyst component and the electrolyte material can work efficiently together with the selected carbon material. By controlling the phase structure, it has been found that a fuel cell capable of generating power stably and efficiently even under a wide range of conditions that has never been obtained has been obtained, and the present invention has been achieved.

  In addition, regarding the durability, the present inventors paid attention to the carbon material used as a catalyst carrier, and earnestly investigated the degree of graphitization, oxygen concentration, specific surface area, water vapor adsorption amount, etc. of the carbon material. As a result, the present inventors have found that the oxidation consumption resistance and the battery performance tend to be consistent with each other.

Therefore, the gist of the present invention is as follows.
(1) A fuel cell comprising a pair of catalyst layers sandwiching a proton conductive electrolyte membrane,
At least the catalyst layer of the cathode includes a catalyst component, an electrolyte material, and a carbon material, and the carbon material carries a catalyst carrier carbon material carrying the catalyst component, and a conductive auxiliary agent carbon material not carrying the catalyst component. When the result of the catalyst component from the three gas-diffusing carbon material not carrying, and consists of two kinds of the catalyst supporting carbon material is catalytic carrier carbon material a and the catalyst supporting carbon material B, and the cathode The catalyst layer has at least a two-layer structure;
The catalyst carrier carbon material A in which the inner layer on the side in contact with the proton conductive electrolyte membrane carries at least the catalyst component, the conductive auxiliary agent carbon material not carrying the catalyst component, the electrolyte material, and the catalyst The outer layer on the side not in contact with the proton-conducting electrolyte membrane comprises at least the catalyst carrier carbon material B carrying the catalyst component and the electrolyte material. And a layer made of the gas diffusion carbon material not supporting the catalyst component, and an inner layer of the catalyst layer,
The catalyst carrier carbon material A carrying at least the catalyst component, the conductive auxiliary agent carbon material not carrying the catalyst component, a catalyst aggregation phase formed by aggregating the component made of the electrolyte material, and at least the catalyst component Consisting of a two-phase mixed structure of a gas diffusion carbon material aggregated phase formed by agglomerating components composed of the gas diffusion carbon material not supporting
The outer layer of the catalyst layer is
Aggregating at least the catalyst carrier carbon material B supporting the catalyst component, a catalyst aggregation phase formed by aggregating the component composed of the electrolyte material, and a component composed of the gas diffusion carbon material not supporting at least the catalyst component A gas diffusion carbon material aggregated phase, and the inner layer and the outer layer in each layer, the catalyst aggregated phase is a continuum, and the gas diffusion carbon material aggregated phase is Microstructure having a structure dispersed in the catalyst agglomerated phase and having a specific surface area S _BET of 1000 m ² / g or more and 4000 m ² / g or less by t-plot analysis of the catalyst support carbon material A according to BET evaluation. The ratio S _micro / S _{total of the} pore surface area S _micro and the total surface area S _total is 0.5 or more, and the ratio X / S of the DBP oil absorption XmL / 100 g of the catalyst support carbon material B and the specific surface area S _BET by BET evaluation _BET is, is 0.2 to 3.0 Fuel cell, wherein the door.
(2) The fuel according to (1), wherein a mass ratio A / (A + B) of the catalyst support carbon material A and the catalyst support carbon material B in the catalyst layer is 0.2 or more and 0.95 or less. battery.
(3) The amount of water vapor adsorption V ₁₀ at 25 ° C. and a relative humidity of 10% of the catalyst support carbon material A is 2 ml / g or less, and the water vapor adsorption of the catalyst support carbon material A at 25 ° C. and a relative humidity of 90% the fuel cell according to the amount V ₉₀ is equal to or is 400 ml / g or more (1) or (2).
(4) the 25 ° C. of the catalyst alone carbon material A, and water vapor adsorption amount V ₁₀ at a relative humidity of 10%, the catalyst support 25 ° C. of the carbon material A, the ratio V of the water vapor adsorption amount V ₉₀ at a relative humidity of 90% ₁₀ / The fuel cell according to any one of (1) to (3), wherein V ₉₀ is 0.002 or less.

  The fuel cell of the present invention is formed in the catalyst layer without dividing the gas, electron, and proton transfer paths, and the electrolyte material in the catalyst layer is always in a suitable wet state under low humidification conditions and low load conditions. Thus, it is possible to prevent the gas diffusion path from being blocked by condensed water even under high humidification conditions or high load conditions, and to supply a fuel cell that exhibits high performance regardless of the humidification conditions or load conditions. Therefore, since the water (humidity) management of the fuel cell system is facilitated, system control and operation are simplified.

  Further, the catalyst support carbon material used in the solid polymer fuel cell of the present invention has higher oxidation consumption resistance and higher battery performance than the conventionally used catalyst support carbon material. There is an effect that can be done. When the polymer electrolyte fuel cell of the present invention is used, durability of an automobile fuel cell, a stationary fuel cell, etc. can be improved, and high cell performance can be obtained. A significant cost reduction can be realized, and commercialization of polymer electrolyte fuel cells can be accelerated.

FIG. 2 is a schematic diagram of an aggregated phase structure of an inner catalyst layer of the present invention (because it is clarified as a schematic diagram, the relative size of each hierarchical structure is different from the actual one). FIG. 2 is a schematic diagram of an aggregated phase structure of an outer catalyst layer of the present invention (because it is clarified as a schematic diagram, the relative size of each hierarchical structure is different from the actual one).

  The fuel cell of the present invention is a fuel cell including a pair of catalyst layers sandwiching a proton conductive electrolyte membrane.

  The catalyst layer included in the fuel cell of the present invention is composed of a mixture including a catalyst component, a carbon material, and an electrolyte material, and the carbon material carries a catalyst support carbon material carrying the catalyst component and a catalyst component. The catalyst support carbon material is composed of two types of carbon materials, the catalyst support carbon material A and the catalyst support carbon material B, which have different characteristics.

  Each component of the present invention has a required function, and each of the components needs to have a minimum material property in order to exhibit the function. If it is a catalyst component, it functions as a catalyst, and if it is an electrolyte material, it conducts protons. In particular, the carbon material is divided into three or more carbon materials. In the case of A, in addition to the function of supporting the catalyst component, the function of storing water, in the case of the catalyst-supporting carbon material B, in addition to the function of supporting the catalyst component, the function of efficiently diffusing gas, the gas diffusion carbon material This is a function of efficiently diffusing gas, and a function of complementing the electron conductivity of the catalyst support carbon material if it is a conductive assistant carbon material.

  The catalyst component used in the catalyst layer of the present invention is not limited as long as the required reaction proceeds on the catalyst component. Examples of preferred catalyst components include noble metals such as platinum, palladium, ruthenium, gold, rhodium, osmium, iridium, noble metal composites and alloys obtained by combining two or more of these noble metals, noble metals and organic compounds and inorganic compounds. And complexes of transition metals, transition metals, composites and alloys of transition metals and noble metals, complexes of noble metals and transition metals with organic compounds and inorganic compounds, metal oxides, and the like. Also, a combination of two or more of these can be used.

Of the carbon material used in the present invention, the catalyst supporting carbon material, two carbon materials different Do that characteristic, i.e., selects the water retention of high catalyst carrier carbon material A and structure of developed catalyst supporting carbon material B . Furthermore, the catalyst layer of the present invention employs at least a two-layer structure, and the catalyst carrier carbon material A having high water retention is provided in the inner layer on the side in contact with the electrolyte membrane side, and the outer layer on the side opposite to the electrolyte membrane with the inner layer interposed therebetween. And a catalyst layer containing the catalyst-supported carbon material B having a developed structure.

  In the catalyst layer of the present invention, the inner layer may be in contact with the proton conductive electrolyte membrane and the outer layer may be a three-layer structure or more as long as it is the outermost layer on the side not in contact with the proton conductive electrolyte membrane. That is, there may be one or more intermediate catalyst layers between the inner layer and the outer layer. Although the inner layer and the outer layer are not limited as long as they have the structure of the present invention, the intermediate catalyst layer is preferably a catalyst layer having an intermediate property between the inner layer and the outer layer, for example, contained in the intermediate layer. When the catalyst support carbon material to be used is a mixture of catalyst support carbon materials A and B, or when there are multiple intermediate layers, the mass ratio of catalyst support carbon material A and catalyst support carbon material B from the inner layer direction toward the outer layer direction A configuration in which A / (A + B) decreases is preferable. The intermediate layer may be a single layer, and the mass ratio A / (A + B) of the catalyst support carbon material A and the catalyst support carbon material B may be continuously changed in the intermediate layer. .

For the catalyst carrier carbon material A, in addition to the function of supporting the catalyst component, a carbon material having a function of storing water that can humidify the nearby electrolyte material in order to obtain stable power generation performance even in a dry state is selected. . In particular, in order to express the function of storing water more effectively, the specific surface area S _BET by the BET evaluation method is 1000 m ² / g or more and 4000 m ² / g or less, and the micropore surface area by the t plot analysis is 2 nm or less in diameter. The ratio S _micro / S _{total of} S _micro and total surface area S _total needs to be 0.5 or more. Here, the specific surface area S _BET by BET evaluation is a specific surface area value obtained by the BET method from measurement of an isothermal adsorption line at a liquid nitrogen temperature of nitrogen gas. When the specific surface area S _BET is 1000 m ² / g or more and 4000 m ² / g or less, the catalyst component is easily supported, and it becomes easy to store water in the catalyst support carbon material under wet conditions, and the stored water under dry conditions. Since the water content of the electrolyte material that is gradually released and is present in the vicinity can be prevented, a decrease in the proton conductivity of the electrolyte material can be suppressed. If the amount is less than 1000 m ² / g, the amount of water that can be retained by the catalyst-supporting carbon material is reduced, and the moisture content of the electrolyte substance in the catalyst layer decreases under dry conditions such as low humidification conditions and low load operation, The internal resistance due to proton conductivity tends to increase. Moreover, the upper limit of the specific surface area is not particularly limited, but the specific surface area of the carbon material that can be substantially used is 4000 m ² / g or less.

As for the catalyst support carbon material A, as described above, the ratio S _micro / S _{total of the} micropore surface area S _micro and the total surface area S _total having a diameter of 2 nm or less by t plot analysis needs to be 0.5 or more. . Here, the specific surface area S _{micro of the} micropores defined as pores having a diameter of 2 nm or less, and the total surface area S _total are calculated from the isotherm adsorption line at the liquid nitrogen temperature of nitrogen gas, and t-plot analysis ( The value calculated by Colloid Chemistry I, Tokyo Chemical Doujin (1995) published by the Chemical Society of Japan was used. When the ratio S _micro / S _{total of the} micropore surface area S _micro and the total surface area S _total is 0.5 or more, the power generation performance under the dry condition is further improved. Although the detailed mechanism is unknown, micropores defined as pores with a diameter of 2 nm or less are easy to store water under the wet condition in the operating environment of the fuel cell, and moderately release the water stored under the dry condition In particular, when the specific surface area S _BET is 1000 m ² / g or more and 4000 m ² / g or less and S _micro / S _total is 0.5 or more, the ease of supporting the catalyst component is improved. At the same time, it is estimated that the amount of water that can be retained by the catalyst-carrying carbon material and the balance between the water absorption and release characteristics are improved, and stable power generation characteristics can be obtained under both wet and dry conditions. Since S _micro is impossible be larger than S _total, the upper limit of S _micro / S _total is 1. When S _micro / S _total is less than 0.5, the power generation performance under a dry condition is substantially lowered, and sufficient characteristics cannot be obtained.

The catalyst support carbon material A used in the present invention is not particularly limited as long as it is a generally existing carbon material, and as described above, the specific surface area S _BET is 1000 m ² / g or more and 4000 m ² / g or less, _Any carbon material having S _micro / S _total of 0.5 or more can be used as a preferred carbon material. In particular, a material that causes a chemical reaction other than the originally required reaction or that elutes a substance constituting the carbon material by contact with condensed water is not preferable, and a chemically stable carbon material is preferable. As the catalyst carrier carbon material A, carbon black, graphite, carbon fiber, activated carbon and the like, pulverized products thereof, carbon compounds such as carbon nanofiber and carbon nanotube, and the like can be used. Two or more types can be mixed and used. An example of the most preferable carbon material is activated carbon. Generally, activated carbon has oxygen introduced into the pore surface of activated carbon in various chemical forms depending on the production method. Illustrative examples include a carboxyl group, a hydroxyl group, a quinone type oxygen, a lactone ring, and a cyclic ether. As a result of intensive studies by the present inventors, when the oxygen content is too high, the catalyst support carbon material A itself is easily oxidized and consumed when used in the catalyst layer of the fuel cell for a long period of time, resulting in a decrease in power generation performance. It becomes easy to connect to. The optimal oxygen content range is 5% by mass or less. If the oxygen content of the activated carbon exceeds 5% by mass, the catalyst support carbon material A is likely to be oxidized and consumed in the fuel cell operating environment, and the life of the catalyst is reduced, so it may not be applicable to the present invention. is there. The kind of oxygen-containing functional group is not particularly limited.

  Furthermore, when a carbon material with a water vapor adsorption amount of 100 mL / g or more at 25 ° C. and a relative humidity of 90% is selected as the catalyst support carbon material A, the electrolyte in the vicinity of the catalyst component remains in an appropriate wet state, and proton conductivity Therefore, the proton conduction resistance does not increase even during a low current discharge in which water is not generated so much on the catalyst component of the cathode, and a more preferable state as a fuel cell can be maintained. Therefore, the catalyst-carrying carbon material of the present invention is so good that it is easily wetted with water, and the upper limit value of the preferable range of the water vapor adsorption amount at 25 ° C. and relative humidity of 90% cannot be limited. If the substantial upper limit of the amount of water vapor adsorption at 25 ° C. and 90% relative humidity is exemplified, about 2000 mL / g estimated to be obtained with activated carbon having a high specific surface area can be mentioned. If the amount of water vapor adsorbed at 90% relative humidity of the catalyst-supporting carbon material is lower than 100 mL / g, the electrolyte in the vicinity of the catalyst component tends to dry under dry conditions, and proton conductivity tends to decrease. is there. More preferably, when the water vapor adsorption amount of the catalyst support carbon material A at 25 ° C. and a relative humidity of 90% is 400 ml / g or more, the electrolyte in the vicinity of the catalyst component maintains an appropriate wet state even in a severe dry state, Since a decrease in proton conductivity can be prevented, a decrease in fuel cell performance can be minimized.

  Further, when the fuel electrode is partially depleted of hydrogen due to the presence of air or the like when the fuel cell is started or stopped, the potential of the air electrode increases, and the carbon material that is the catalyst carrier may be oxidized and consumed. As is known, in order to further enhance the durability of the fuel cell of the present invention, the amount of water vapor adsorbed at 25 ° C. and 10% relative humidity of the catalyst support carbon material A is 2 ml / g or less. Consumption is suppressed, and a catalyst excellent in oxidation consumption resistance can be obtained. When the carbon material used as the catalyst support has a water vapor adsorption amount of more than 2 ml / g at 25 ° C. and a relative humidity of 10%, the oxidation consumption may be significant, and the hydrophilicity of the catalyst support increases and the drainage capacity increases. In some cases, the fuel cell performance may decrease due to a tendency to decrease. In addition, a part of the supported catalyst may fall off or partly elute due to the above oxidation consumption, which may reduce the amount of the catalyst and lower the fuel cell performance.

  If the amount of water vapor adsorption at 10% relative humidity is 2 ml / g or less, the physical basis for suppressing oxidative consumption is not clear, but water vapor adsorption at low relative humidity is not possible with aggregate structures or pore structures. It is thought that it depends on the functional groups adsorbed on the surface, and there is a strong correlation between the amount of functional groups and the resistance to oxidation consumption. It can be inferred that the catalyst particles fall off and are eluted.

  The amount of water vapor adsorption at 25 ° C and relative humidity of 10% of the carbon material used as the catalyst support is better if only considering oxidation resistance, but the dispersibility when supporting the catalyst depends on the presence of functional groups. On the other hand, since improvement is also conceivable, the water vapor adsorption amount at 25 ° C. and 10% relative humidity of the catalyst support carbon material A is more preferably 0.05 ml / g or more.

In the present invention, the water vapor adsorption amount (V ₉₀ ) at 25 ° C. and a relative humidity of 90%, which is an index corresponding to the moisturizing ability of the catalyst, has a high value, and at the same time, high oxidation consumption resistance of the catalyst support carbon material It is more preferable that the water vapor adsorption amount (V ₁₀ ) at 25 ° C. and 10% relative humidity as a corresponding index has a small value in order to achieve both durability and high catalyst activity. Result of extensive studies, 25 ° C., the amount of adsorbed water vapor at a relative humidity of _10% (V 10) and 25 ℃, V ₁₀ / V ₉₀ is the ratio of the water vapor adsorption amount at a relative humidity of _90% (V 90) is 0.002 or less It has been found that it is suitable for achieving both high durability (oxidation wear resistance) and high moisturizing ability. More preferably, it is 0.0018 or less. When V ₁₀ / V ₉₀ exceeds 0.002, the durability or the moisture retention performance is deteriorated.

  The amount of water vapor adsorbed at 25 ° C. and relative humidity of 10% and 90% as an index in the present invention is shown by converting the amount of water vapor adsorbed per 1 g of carbon material placed in an environment of 25 ° C. into the water vapor volume in the standard state. Index. The measurement of the water vapor adsorption amount at 25 ° C. and relative humidity of 10% and 90% of the carbon material can be performed using a commercially available water vapor adsorption amount measuring device. The water vapor adsorption amount in the present invention is an adsorption amount when the water vapor is gradually adsorbed on the carbon material by starting the adsorption from a vacuum state where the vapor pressure of the water vapor is zero, and gradually increasing the relative pressure of the water vapor. Relative humidity values of 10% and 90% are used.

The primary particle size of the catalyst-carrying carbon material A is more preferably 5 μm or less and 10 nm or more. A carbon material larger than this range can be used after being pulverized, and is preferably pulverized. If the primary particle diameter is more than 5 μm, there is a high risk of disrupting the gas diffusion path and proton conduction path, and the amount of the catalyst component used is particularly limited due to economic reasons. For example, a catalyst layer having a thickness of about 10 μm. When it is required to exhibit performance, the distribution of the catalyst-supporting carbon material in the catalyst layer tends to be non-uniform, which is not preferable. Further, if the primary particle diameter is less than 10 nm, the electron conductivity is lowered, which is not preferable in some cases, and a carbon material having S _micro / S _total of 0.5 or more may not be substantially obtained.

As the catalyst support carbon material B, a carbon material having a function of efficiently diffusing gas in addition to a function of supporting a catalyst component is selected. In particular, in order to more effectively express the function of diffusing gas efficiently, a carbon material with a developed structure is preferably used. For this purpose, the ratio X / S _BET between the DBP oil absorption amount XmL / 100 g of the catalyst support carbon material B and the specific surface area S _BET by BET evaluation needs to be 0.2 or more and 3.0 or less. An example of a preferred material is carbon black. In carbon black, a plurality of primary particles are fused to form a secondary structure called a structure. Depending on the type, this structure has been developed, and the primary particles are connected to each other in a space. It is preferable to use a carbon material having such a structure as the catalyst support carbon material B because the enclosed space serves as a gas diffusion path or a water movement path. In other words, the carbon material A for the catalyst carrier is selected as a carbon material that has the property of easily storing water, but the carbon material having such a characteristic often has an undeveloped structure, and the catalyst carrier carbon material A alone is selected. It is difficult to develop a gas diffusion path when the catalyst-supporting carbon material is constituted by the above. By compounding the catalyst support carbon material B with a developed structure, it is possible to develop a gas diffusion path in the vicinity of the catalyst support carbon material A, and the gas diffusion path is water in particular under high load operation and high humidification conditions. It is preferable because it can be prevented from being clogged by.

  The degree of structure can be determined by observing with an electron microscope, but can be determined by the relationship between DBP oil absorption and specific surface area.

  DBP oil absorption is the amount of dibutyl phthalate absorbed by carbon black when unitary carbon black is brought into contact with dibutyl phthalate, and is mainly absorbed in the gaps between primary particles. When the structure is developed, the DBP oil absorption increases, and when the structure is not so developed, the DBP oil absorption tends to decrease. However, DBP is absorbed not only by the gaps between the primary particles but also by the micropores formed inside the primary particles, so that the DBP oil absorption amount does not always represent the degree of structure. This is because when the specific surface area as measured by the nitrogen adsorption amount increases, the DBP absorbed in the micropores increases, and the total DBP oil absorption amount tends to increase. Therefore, in the high structure carbon black, the DBP oil absorption amount is large for the nitrogen adsorption amount, and conversely, in the low structure carbon black, the DBP oil absorption amount is small for the nitrogen adsorption amount.

When a carbon material having a DBP oil absorption amount XmL / 100 g and a specific surface area S _BET m ² / g ratio X / S _BET of 0.2 to 3.0 is used as the catalyst support carbon material B while securing a conductive path A gas diffusion path and a water movement path can be secured, and a high-performance catalyst layer can be obtained. When the ratio of X / S _BET is less than 0.2, the space for the gas diffusion path becomes poor, and it is difficult to stably extract the performance of the catalyst layer. If it exceeds 3.0, the conductivity is impaired.

The catalyst support carbon material B used in the present invention is not particularly limited as long as it is a generally existing carbon material. As described above, the DBP oil absorption amount XmL / 100 g and the specific surface area S _BET m ² / _BET according to BET evaluation. Any carbon material having a g ratio X / S _BET of 0.2 or more and 3.0 can be used as a preferred carbon material. In particular, a material that causes a chemical reaction other than the originally required reaction or that elutes a substance constituting the carbon material by contact with condensed water is not preferable, and a chemically stable carbon material is preferable. As the catalyst support carbon material B, carbon black, graphite, carbon fiber, activated carbon and the like, pulverized products thereof, carbon compounds such as carbon nanofiber and carbon nanotube, and the like can be used. Two or more types can be mixed and used. An example of the most preferable carbon material is carbon black.

  The primary particle diameter of the catalyst-carrying carbon material B is more preferably 5 μm or less and 5 nm or more. A carbon material larger than this range can be used after being pulverized, and is preferably pulverized. If the primary particle diameter is more than 5 μm, there is a high risk of disrupting the gas diffusion path and proton conduction path, and the amount of the catalyst component used is particularly limited due to economic reasons. For example, a catalyst layer having a thickness of about 10 μm. When it is required to exhibit performance, the distribution of the catalyst-supporting carbon material in the catalyst layer tends to be non-uniform, which is not preferable. Further, if the primary particle diameter is less than 5 nm, the electron conductivity may be lowered, which is not preferable.

  The preferred content in the catalyst layer of the catalyst support carbon materials A and B in the catalyst layer depends on the type of catalyst support carbon materials A and B, the type and content of the gas diffusion carbon material, the type of catalyst component and the loading rate. Since it is affected, it cannot be specified, but if the content in the catalyst layer combining the catalyst support carbon materials A and B is in the range of 5% by mass to 80% by mass, at least the fuel cell functions, The effects of the present invention can be obtained. If a more preferable range is illustrated, it is 10 mass% or more and 60 mass% or less. If it is out of this range, the balance with other components is deteriorated, and an efficient fuel cell may not be obtained. For example, if it is less than 5% by mass, the amount of the catalyst component supported on the catalyst-supporting carbon materials A and B is limited, and sufficient performance may not be exhibited. For example, if it exceeds 80% by mass, the amount of the electrolyte material becomes too small and the proton transmission path becomes poor, so that an efficient battery may not be obtained.

  The mass ratio A / (A + B) of the catalyst support carbon material A and the catalyst support carbon material B contained in the catalyst layer of the present invention is preferably in the range of 0.2 to 0.95. When the mass ratio A / (A + B) between the catalyst support carbon material A and the catalyst support carbon material B is less than 0.2, it is difficult to obtain the combined effect of the catalyst support carbon material A, and it is difficult to obtain a low load operation or low It is not preferable because the moisture content of the electrolyte substance in the catalyst layer tends to decrease under humidified conditions, and the internal resistance due to proton conductivity tends to increase. When the mass ratio A / (A + B) of the catalyst support carbon material A and the catalyst support carbon material B is more than 0.95, the gas diffusion path is likely to be clogged with water during high load operation or high humidification conditions. Therefore, it is not preferable.

  Further, the inner layer containing the catalyst carrier carbon material A having high water retention contains a conductive auxiliary agent carbon material. The kind of the conductive auxiliary carbon material in the catalyst layer of the present invention is not particularly limited as long as it is a generally existing carbon material having electron conductivity, but may cause a chemical reaction other than the originally required reaction. A material from which a substance constituting the carbon material is eluted by contact with condensed water is not preferable, and a chemically stable carbon material is preferable. The primary particle size of the carbon material is more preferably 1 μm or less and 5 nm or more. Carbon materials larger than this range can be used after being pulverized. When the primary particle diameter is more than 1 μm, the distribution of the conductive auxiliary agent carbon material in the catalyst layer tends to be non-uniform, which is not preferable. On the other hand, if the primary particle diameter is less than 5 nm, the electron conductivity is lowered, which is not preferable. Carbon black is most commonly used as a preferred conductive aid carbon material, but, in addition, if it has electronic conductivity, graphite, carbon fiber, activated carbon and the like, pulverized products thereof, carbon nanofiber, Carbon compounds such as carbon nanotubes can be used. Also, a mixture of two or more of these can be used. Among them, the electronic conductivity of the conductive auxiliary agent carbon material is more preferably equal to or higher than the electronic electric conductivity of the catalyst supporting carbon material A (conductive auxiliary agent carbon material ≧ catalyst supporting carbon material A).

  The conductive auxiliary carbon material of the present invention is preferably a carbon material having a structure developed to some extent. An example of a preferred material is carbon black. In carbon black, a plurality of primary particles are fused to form a secondary structure called a structure. Depending on the type, this structure has been developed, and the primary particles are connected to each other in a space. It is preferable to use a carbon material having such a structure as the conductive assistant carbon material because the enclosed space serves as a gas diffusion path or a water movement path.

Using a carbon material with a DBP oil absorption amount XmL / 100g and a specific surface area S _BET m ² / g ratio X / S _BET of 0.2 or more and 3.0 or less as the conductive auxiliary agent carbon material while ensuring a conductive path Since a gas diffusion path and a water movement path can be secured, a higher performance catalyst layer can be obtained, which is preferable. When the ratio of X / S _BET is less than 0.2, the space for the gas diffusion path becomes poor, and it may be difficult to stably extract the performance of the catalyst layer. If it exceeds 3.0, the conductivity may be impaired, which may not be preferable.

  The content of the conductive additive carbon material of the present invention in the inner layer of the catalyst layer is preferably in the range of 3% by mass to 30% by mass. Within this range, even when the catalyst carrier carbon material A itself has poor electronic conductivity, the conductive assistant carbon material can effectively collect current from the catalyst component. If it is less than 3% by mass, the effect of addition is small, and the current collecting effect may be low. If it is 30% by mass or more, the density of the catalyst component in the inner layer of the catalyst layer is excessively lowered. In particular, concentration polarization may increase when air is used as the cathode gas, which is not preferable. In particular, when the mass of the catalyst support carbon material A is 1, it is more preferable that the mass of the conductive additive carbon material is in the range of 0.05 to 0.4. Within this range, the difference between the power generation characteristics under wet conditions and the power generation characteristics under dry conditions becomes small, and stable characteristics that are hardly affected by conditions can be exhibited. If it is less than 0.05, the electron conductivity of the inner layer is lowered, so that the internal resistance is increased and the performance may be lowered. If it exceeds 0.4, the density of the catalyst component in the inner layer of the catalyst layer is excessively lowered, and the concentration polarization may be increased particularly when air is used as the cathode gas, which is not preferable.

  The range of the optimal oxygen content of the conductive assistant carbon material of the present invention is 5% by mass or less, more preferably 3% by mass or less. If the oxygen content of the conductive assistant carbon material exceeds 5% by mass, the current collecting effect of the conductive assistant carbon material is reduced, and the effect of using the conductive assistant carbon material may not be obtained. There is no particular lower limit for the oxygen content, and good characteristics are exhibited even when there is almost no oxygen contained.

  The type of carbon material used in the gas diffusion carbon material of the present invention is capable of forming a gas diffusion path, and causes a chemical reaction other than the originally required reaction or constitutes the carbon material by contact with condensed water. A material from which the substance is eluted is not preferred, and is a chemically stable carbon material. The primary particle diameter of the gas diffusion carbon material is preferably 1 μm or less and 5 nm or more. Carbon materials larger than this range can be used after being pulverized. If the primary particle diameter is more than 1 μm, the function of securing the gas diffusion path cannot be expected, and the distribution of the gas diffusion carbon material in the catalyst layer tends to be nonuniform, which is not preferable. Further, when the primary particle diameter is less than 5 nm, a preferable gas diffusion path may not be obtained. As a preferred gas diffusion carbon material, carbon black is the most common. However, if a gas diffusion path can be formed, graphite, carbon fiber, activated carbon, etc., pulverized products thereof, carbon nanofiber, carbon nanotube, etc. Carbon compounds can be used. Also, a mixture of two or more of these can be used. Furthermore, in the present invention, it is preferable that the gas diffusion carbon material is present in the catalyst layer as an agglomerated phase in which the gas diffusion carbon materials are aggregated, because the gas diffusion path is hardly blocked by the electrolyte material and the gas is easily diffused in the catalyst layer. . The gas diffusion path formed by the agglomerated phase is not easily broken even when the cell is strongly fastened, and it is easy to maintain the optimum pore diameter controlled at the time of forming the catalyst layer for a long period of time.

  The gas diffusion carbon material of the present invention preferably uses carbon black having a higher structure. In the carbon black, a plurality of primary particles are fused to form a secondary structure called a structure. Depending on the type, this structure has been developed, and the primary particles are connected to each other in a space. In the catalyst layer included in the present invention, the gas diffusion carbon material joins such spaces so that a space surrounded by a network of primary particles is continuously formed in the catalyst layer as a gas diffusion path. One of them. Therefore, in the case of the gas diffusion carbon material using the carbon black, a structure that aggregates the gas diffusion carbon materials can be easily formed in the catalyst layer. The gas diffusion path formed by agglomerating the gas diffusion carbon material is more difficult to break even when the cell is strongly fastened, and it is easy to maintain the optimum pore diameter controlled at the time of forming the catalyst layer for a longer period of time.

When a carbon material having a ratio X / S _{BET of} DBP oil absorption XmL / 100g and specific surface area S _BET m ² / g by BET evaluation of 1 or more is used as the gas diffusion carbon material of the present invention, a more preferable gas diffusion path is obtained. The equipped catalyst layer can be formed. This is because if the ratio of X / S _BET is 1 or more, a space formed in the gap between the primary particles of carbon black with a high structure is large, and formation of a gas diffusion path preferable for battery reaction can be expected. When the ratio of X / S _BET is less than 1, the gas diffusion path due to the structure becomes poor, and the gap between the secondary particles of carbon black mainly forms the gas diffusion path. In some cases, it cannot be ensured or the holes are easily broken when the cells are fastened, so that it is difficult to control and it is difficult to stably extract the performance of the catalyst layer. More preferably, the ratio of X / S _BET is 1.5 or more. If it is 1.5 or more, the pore size of the gas diffusion path formed by the structure is sufficiently large, and flooding is difficult even when a high current is taken out. With such a structure, gas easily diffuses, and the gas diffusion path is not easily blocked by water. Therefore, the catalyst in the catalyst layer can be used effectively, and a high output fuel cell can be obtained even with a small amount of catalyst. be able to.

  The gas diffusion carbon material of the present invention is more preferably selected from carbon materials having a low hydration power. By including in the catalyst layer a carbon material that does not support the catalyst component and has a low hydration power, that is, a gas diffusion carbon material, a path through which gas can diffuse into the catalyst layer can be developed. If it exists, hydrogen or a mixed gas mainly composed of hydrogen, and if it is a cathode, oxygen or air easily diffuses into the catalyst layer and can contact many catalyst surfaces. Therefore, the reaction in the catalyst layer is efficiently advanced, and high battery performance can be obtained. When a carbon material with a low hydration power is selected as the gas diffusion carbon material, a large amount of water is generated in the catalyst layer when the catalyst layer is exposed to high humidification conditions due to fluctuations in operating conditions or when the catalyst layer is operated in a high current density region. When it occurs, it is possible to prevent the gas diffusion path from being blocked by water and to prevent the battery performance from deteriorating.

  Therefore, the gas diffusion carbon material contained in the fuel cell of the present invention has a low water hydration capacity of 50 mL / g or less at 25 ° C. and a relative humidity of 90%. The blocking of the path can be effectively suppressed, and the current can be taken out with a stable voltage. If it exceeds 50 mL / g, the condensed water is stagnated in the catalyst layer during current discharge, the gas diffusion path is likely to be blocked, and the voltage behavior may become unstable.

  In order to obtain a higher effect, a carbon material having a hydration power in a more appropriate range is used as the gas diffusion carbon material. Specifically, a carbon material having a water vapor adsorption amount of 1 mL / g or more and 20 mL / g or less at 25 ° C. and 90% relative humidity is selected as the gas diffusion carbon material. Within this range, excessive drying of the electrolyte material in the catalyst layer is suppressed, and water generated inside the catalyst layer is efficiently discharged out of the catalyst layer even during a large current discharge, and the gas diffusion path Therefore, an efficient battery can be obtained over the entire region regardless of load conditions from low load to high load. When the water vapor adsorption amount at 25 ° C. and relative humidity 90% is less than 1 mL / g, the hydration power is too small (water repellency becomes too strong), and excessive drying may be caused. If the amount of water vapor adsorption at 25 ° C and 90% relative humidity exceeds 20 mL / g, the water generated inside the catalyst layer cannot catch up when a large current is continuously taken out, and the gas diffusion path is blocked. May end up. In this case, the effect of adding the gas diffusion carbon material is reduced.

  The content of the gas diffusion carbon material according to the present invention in the catalyst layer in the catalyst layer is more preferably in the range of 3% by mass to 30% by mass in each of the inner layer and the outer layer. If it is less than 3% by mass, the gas diffusion path cannot be sufficiently developed, and the effect of including the gas diffusion carbon material may not be expected. If it exceeds 30 mass%, the proton conduction path is interrupted by the gas diffusion carbon material and becomes poor, and the IR drop becomes large, so that the battery performance may be deteriorated. If it is within the range of 3% by mass or more and 30% by mass or less, the gap of the gas diffusion carbon material forms a network in the catalyst layer, and this becomes a gas diffusion path, so the catalyst component in the catalyst layer is effectively used. be able to. Although depending on the type and form of the carbon material to be used, it is most preferably 5% by mass or more and 25% by mass or less in each of the inner layer and the outer layer. Within this range, an optimum gas diffusion path can be developed without impairing the proton conduction path and the electron conduction path, so that it is possible to obtain a fuel cell electrode having extremely efficient power generation characteristics.

Control of the hydration power of various carbon materials included in the present invention can be achieved by selecting a water vapor adsorption amount as an index from generally existing carbon materials. Alternatively, even in the case of a carbon material having a water vapor adsorption amount less than the preferred range, the water vapor adsorption amount can be reduced by treating the carbon material surface with an acid, a base, or the like, or exposing the carbon material to an oxidizing atmosphere environment. It can be increased to a suitable range. Without limitation, for example, treatment in warm concentrated nitric acid, immersion in an aqueous hydrogen peroxide solution, heat treatment in an ammonia stream, immersion in a heated aqueous sodium hydroxide solution The amount of water vapor adsorption can be increased by heating in KOH or NaOH, or by heat treatment in dilute oxygen, dilute NO, or NO ₂ . On the other hand, when the amount of water vapor adsorption is too large, the water vapor adsorption amount can be reduced to a suitable range by firing in an inert atmosphere. Although not limited, for example, the amount of water vapor adsorption can be reduced by heat treatment in an atmosphere of argon, nitrogen, helium, vacuum, or the like.

  The fuel cell of the present invention is effective regardless of the type of electrolyte material used, and is not particularly limited as long as the electrolyte material used has a function of conducting protons. Absent. The electrolyte membrane used in the fuel cell of the present invention and the electrolyte material used in the catalyst layer are polymers introduced with phosphoric acid groups, sulfonic acid groups, etc., such as perfluorosulfonic acid polymer or benzenesulfonic acid. However, the polymer is not limited to a polymer, and may be used for a fuel cell using an electrolyte membrane such as an inorganic type or an inorganic-organic hybrid type. If a particularly preferable operating temperature range is exemplified, a fuel cell that operates within a range of normal temperature to 150 ° C. is preferable. Further, the mass ratio of the catalyst support carbon material and the electrolyte material contained in the catalyst layer is preferably 1/10 to 5/1. If the amount of the catalyst-supporting carbon material is less than 1/10, the catalyst surface is excessively covered with the electrolyte material, and the area where the reaction gas can come into contact with the catalyst component may be reduced. If the catalyst support carbon material is contained in excess of 5/1, the electrolyte material network may be poor and proton conductivity may be lowered.

  In the catalyst layer of the present invention, the inner layer is agglomerated with a catalyst component, the catalyst support carbon material A, a conductive additive carbon material, and an electrolyte material formed by agglomeration, and a gas diffusion carbon material as a main component. It is preferable that the gas diffusion carbon material aggregated phase has two aggregated phase structures, the catalyst aggregated phase is a continuous body, and the gas diffusion carbon material aggregated phase is dispersed in the catalyst aggregated phase. The outer layer comprises a catalyst component, the catalyst carrier carbon material B, and an electrolyte material as main components, and a conductive agglomerate carbon material, a catalyst agglomerated phase formed by agglomerating these as necessary, and a gas diffusion carbon material. The gas diffusion carbon material aggregate phase formed as a main component and a gas aggregate carbon material aggregate phase, the catalyst aggregate phase is a continuum, and the gas diffusion carbon material aggregate phase is dispersed in the catalyst aggregate phase As a result, the characteristics can be dramatically improved as compared with the catalyst layer in which the respective components are simply mixed on average. FIG. 1 and FIG. 2 schematically show the structure of the inner layer (FIG. 1) and the outer layer (FIG. 2) of the catalyst layer according to the present invention. In FIGS. 1 and 2, since each material and the aggregated phase are schematically expressed clearly, the relative size of each hierarchical structure is different from the actual size.

  By making the inner layer and the outer layer of the catalyst layer of the present invention each have two agglomerated phases, first, the gas diffusion carbon material can function effectively. That is, by making the catalyst component and the electrolyte material not contact with the surface of the gas diffusion carbon material as much as possible, the surface characteristics of the gas diffusion carbon material and the structural characteristics represented by the structure are maximized and the gas diffusion carbon materials are aggregated. Thus, pores formed in the gaps of the gas diffusion carbon material can be continuously developed as a gas diffusion path.

  Second, in the inner layer and the outer layer of the catalyst layer of the present invention, the catalyst support carbon material A or B carrying the catalyst component, the conductive additive carbon material, and the electrolyte material are contained in one aggregate (catalyst aggregation phase). Thus, the water produced on the catalyst component effectively wets the electrolyte material in the vicinity, and an increase in proton conduction resistance of the electrolyte material can be prevented. In addition, since the conductive auxiliary agent carbon material coexists in the inner layer, a gas diffusion path is formed even in an environment where the catalyst support carbon material A is covered with water under high load operation or high humidification conditions. The reaction can be effectively advanced on the catalyst component supported on the catalyst support carbon material A.

  Third, in the catalyst layer of the present invention, the catalyst cohesive phase, which is firmly fused with the electrolyte material as a medium, is used as a continuous phase, thereby enhancing the mechanical strength of the catalyst layer itself and making the electrolyte material network continuous. By doing so, it is possible to reduce the proton conduction resistance that causes the largest increase in internal resistance in the catalyst layer.

  The two aggregated phase structures of the catalyst layer of the present invention can also be confirmed by observing the cross section. Make a cut surface at an arbitrary angle on the catalyst layer at an arbitrary angle, and observe the cross section to confirm that the carbon material on which the catalyst component is not supported forms an aggregate (aggregated phase). Is the method. The aggregate corresponds to the gas diffusion carbon material aggregate phase of the present invention.

  In the field of view of 10 μm × 10 μm in the cross section of the catalyst layer, at least one carbon material agglomerated phase (gas diffusion carbon material agglomerated phase) having no catalyst component with a circle equivalent diameter of 300 nm or more is dispersed. It is preferable. If it is less than one, various carbon materials have been mixed on average when forming the catalyst layer, or the content of the gas diffusion carbon material which is a carbon material not supporting the catalyst component is too low, so at least the gas diffusion carbon material Since the catalyst layer is not dispersed due to the formation of an agglomerated phase, the gas transmission path is undeveloped and gas diffusibility is poor, and it exhibits stable performance especially under high humidification conditions and high load operation. I can't. More preferably, at least one carbon material aggregated phase (gas diffusion carbon material aggregated phase) having no catalyst component having a circle equivalent diameter of 500 nm or more exists in the same visual field. If it is the said structure, it will be suppressed that power generation performance becomes unstable at least under wet conditions, and the stable power generation performance will be obtained.

  The method for forming the cut surface of the catalyst layer is not particularly limited. For example, the catalyst layer is cut with a cutter knife or scissors, or the catalyst layer cooled to a temperature lower than the glass transition temperature of the electrolyte material is broken, and the cross section is observed. The method etc. can be mentioned. A particularly preferable method is a method of forming a cut surface of the catalyst layer in an environment cooled with liquid nitrogen using a cryomicrotome or the like. Although a method of preparing and observing an ultrathin section using a cryomicrotome is conceivable, more simply, a catalyst layer is set as a sample on the cryomicrotome, and the surface of the catalyst layer is coated with a trimming knife made of diamond or glass. This is a method of cutting and observing the generated cut surface.

  The observation method is preferably a scanning electron microscope that can observe the same field of view with both a secondary electron image and a reflected electron image, and that can be observed at a magnification of at least 10,000 times. The secondary electron image reflects the unevenness information of the cross section of the catalyst layer, and the presence of carbon material, electrolyte material, and pores can be confirmed. The presence of the catalyst component can be confirmed using a high-precision electron microscope, but when the reflected electron image in the same field is observed, the component distribution information is reflected.For example, when a metal is used for the catalyst component, the catalyst component is A bright, non-catalytic area is dark contrasted and an image is obtained. When comparing the secondary electron image and the reflected electron image of the catalyst layer of the present invention, a portion having a dark contrast in the reflected electron image despite the presence of a carbon material in the secondary electron image in the same field of view, That is, a carbon material having no catalyst component is recognized. A preferred embodiment of the present invention is that the equivalent circular diameter of the outer periphery of the portion, that is, the carbon material portion having no catalyst component, is 300 nm or more.

  An example will be described in which the presence of a carbon material aggregated phase (gas diffusion carbon material aggregated phase) having no catalyst component having a circle equivalent diameter of 300 nm or more can be identified more quantitatively. Brightness is captured at a magnification of 10,000 times at a resolution of 272 DPI x 272 DPI and 256 levels. Using the image analysis software, the brightness of the captured image is displayed in black so that the range from the darker to the 110th layer is displayed in black, and the range from the 111th layer to the brighter is displayed in white so that it is white. Turn into. In this state, since many black points are isolated in an island shape, in order to clarify the target range, each black point is expanded once to recognize adjacent points. Further, a hole filling process is executed, and blank portions in the range are filled in so as to be recognized as being in the same range. Finally, a degeneration process for restoring the expanded portion is performed to clarify the target range. Then, the circle equivalent diameter of each black part is calculated from the area of each black part, and all parts less than 300 nm are cut. Of the remaining black portions, when a carbon material is present in the secondary electron image, this is a preferred embodiment of the present invention. When performing such quantitative analysis, it is preferable to analyze a more average cross section of the catalyst layer. For example, a method of analyzing about 5 randomly selected fields of view of a randomly selected cross section and judging the average value thereof is more preferable.

  In the present invention, it is not necessary to observe the carbon material aggregated phase (gas diffusion carbon material aggregated phase) having no catalyst component and satisfy the specified range of the present invention by all the analytical methods described above. If the obtained value satisfies the specified range of the present invention, the effect can be obtained.

  The method for producing the catalyst layer included in the fuel cell of the present invention is not particularly limited as long as it has a two-layer structure of an inner layer containing the catalyst support carbon material A and an outer layer containing the catalyst support carbon material B. In particular, in each of the inner layer and the outer layer, it is preferable if the gas diffusion carbon material aggregation phase is dispersed in the continuous phase of the catalyst aggregation phase and the electrolyte material is adsorbed on the surface of the gas diffusion carbon material as much as possible. For example, liquids containing materials contained in the inner layer and the outer layer are prepared separately, and water and an organic solvent are added as necessary to produce two types of ink. A method of drying each of these two types of inks into a film and laminating them to form a catalyst layer having a two-layer structure.After drying the first type of ink into a film, the first type using the second type of ink A method of drying a film on the catalyst layer to form a catalyst layer having a two-layer structure can be selected.

  A particularly preferable method for preparing the ink for the inner layer or the outer layer will be described below.

  (i) Catalyst support carbon material A carrying a catalyst component, or catalyst support carbon material B carrying a catalyst component, and a conductive solvent carbon material in the case of an inner layer, and an electrolyte material, a good solvent for the electrolyte material After pulverizing and mixing in the liquid A, a poor solvent for the electrolyte material is added, and the electrolyte material, the catalyst carrier carbon material supporting the catalyst component, and the conductive auxiliary agent carbon material in the case of the inner layer are aggregated. A liquid B obtained by pulverizing a gas diffusion carbon material not supporting a catalyst component in a poor solvent for the electrolyte material, and a liquid C obtained by mixing the liquid A and the liquid B are used as ink. .

  In this method, the catalyst carrier carbon material A carrying the catalyst component or the catalyst carrier carbon material B carrying the catalyst component and the electrolyte material (conducting aid carbon material in the case of the inner layer) are both good for the electrolyte material. When pulverized and mixed in a solvent, the catalyst support carbon material A or B and (in the case of the inner layer, the conductive assistant carbon material) are mixed and pulverized into fine aggregates, and the electrolyte material is dissolved in the vicinity of the surface. It will be in the state. When the electrolyte material is precipitated by adding a poor solvent for the electrolyte material to this, the catalyst support carbon material A or B carrying the catalyst, and (in the case of the inner layer, the conductive assistant carbon material), the electrolyte material particles agglomerate, The electrolyte material is fixed to the catalyst support carbon material A or B carrying the catalyst (in the case of the inner layer, also to the conductive assistant carbon material). Further, when a fine gas diffusion carbon material is added to this solution, the electrolyte material is fixed to the catalyst support carbon material, so that the surface of the gas diffusion carbon material is not easily covered with the electrolyte material. Can take advantage of the surface properties originally possessed. That is, the present invention has a structure of two agglomerated phases of the catalyst agglomerated phase and the gas diffusion carbon material agglomerated phase of the present invention, wherein the catalyst agglomerated phase is a continuum and the gas diffusion carbon material agglomerated phase is dispersed in the catalyst agglomerated phase. It becomes a structure. In particular, this method is effective when a gas diffusion carbon material whose surface hydration property is controlled is used. Further, the dispersion state (shape and size) of the gas diffusion carbon material aggregated phase can be controlled by changing the method of mixing the liquid A and the liquid B.

  (ii) The catalyst support carbon material A or B carrying the catalyst component and a small amount of the electrolyte material are pulverized and mixed in a good solvent for the electrolyte material, and then solidified by drying to form the solidified product (conducting aid in the case of the inner layer). After adding the agent carbon material and crushing with a poor solvent for the electrolyte material, the solution A obtained by further dropping the solution in which the electrolyte material is dissolved, and the gas diffusion carbon material not supporting the catalyst component are applied to the electrolyte material. A liquid B obtained by pulverizing in a poor solvent is prepared, and a liquid C obtained by mixing the liquid A and the liquid B is used as an ink and dried into a film to form a catalyst layer.

  In this method, the catalyst carrier carbon material A or B carrying the catalyst component is pulverized and mixed in a good solvent of the electrolyte material together with a trace amount of the electrolyte material, and then dried. It is fixed on the surface as a film. When the solid material obtained by the drying (catalyst support carbon material A or B on which a small amount of electrolyte material is fixed) is pulverized in a poor solvent for the electrolyte material (along with the conductive assistant carbon material in the case of the inner layer), the electrolyte material Is atomized while being fixed to the catalyst support carbon material carrying the catalyst component. Further, a necessary and sufficient electrolyte solution is dropped into the suspension to precipitate the electrolyte material, and the catalyst support carbon material A or B in which the electrolyte material is slightly fixed (in the case of the inner layer, the conductive assistant carbon material). And) a dispersion in which the deposited electrolyte material is agglomerated. When a gas diffusion carbon material is added to the dispersion, the electrolyte material is formed on the surface of the catalyst carrier carbon material carrying the catalyst (in the case of the inner layer, the conductive assistant carbon material) as in the method (i). Since it is fixed or agglomerated, the surface of the gas diffusion carbon material is hardly covered with the electrolyte material, and the surface properties inherently possessed by the surface of the gas diffusion carbon material can be utilized. That is, the present invention has a structure of two agglomerated phases of the catalyst agglomerated phase and the gas diffusion carbon material agglomerated phase of the present invention, wherein the catalyst agglomerated phase is a continuum and the gas diffusion carbon material agglomerated phase is dispersed in the catalyst agglomerated phase. It becomes a structure. This method is also effective particularly when a gas diffusion carbon material whose surface hydration property is controlled is used. Further, the dispersion state (shape and size) of the gas diffusion carbon material aggregated phase can be controlled by changing the method of mixing the liquid A and the liquid B.

  The good solvent for the electrolyte material used in these catalyst layer preparation methods is a solvent that substantially dissolves the electrolyte material used, and it cannot be limited because it depends on the type and molecular weight of the electrolyte material. For example, as a good solvent for the perfluorosulfonic acid polymer contained in a commercially available 5% Nafion (registered trademark) manufactured by Aldrich, methanol, ethanol, isopropyl alcohol, and the like can be given.

  In addition, the poor solvent for the electrolyte material used in these preferred catalyst layer preparation methods is a solvent that does not substantially dissolve the electrolyte material to be used, and the solvent varies depending on the type and molecular weight of the electrolyte material. It cannot be specified. Examples of the poor solvent for the perfluorosulfonic acid polymer contained in a commercially available 5% Nafion solution made by Aldrich include hexane, toluene, benzene, ethyl acetate, butyl acetate and the like.

  Among the preferred catalyst layer preparation methods of (i) or (ii) described above, as a method of pulverizing or pulverizing and mixing, the catalyst carrier carbon material and gas diffusion carbon material that are large aggregates are pulverized and at least 1 μm. The means is not limited as long as the purpose of pulverizing into the following aggregates can be achieved. Examples of general techniques include a method using ultrasonic waves and a method of mechanically pulverizing using a ball mill or glass beads.

  When the gas diffusion layer is used in the fuel cell of the present invention, a function of uniformly diffusing gas from the gas flow path formed in the separator to the catalyst layer and a function of conducting electrons between the catalyst layer and the separator are required. However, it is not particularly limited as long as it has these functions. In general examples, a carbon material such as carbon cloth or carbon paper is used as a main constituent material. A metal material such as a metal mesh or metal wool can be used as long as it can provide corrosion resistance in addition to gas diffusibility and electron conductivity.

  As an example of a preferable structure of the gas diffusion layer, the separator side layer of the gas diffusion layer is a gas diffusion fiber layer mainly containing a fibrous carbon material, and the catalyst layer side layer is a micropore mainly containing carbon black. A two-layer structure composed of layers can be given.

  As a method for drying the ink into a film, a generally proposed method can be applied and is not particularly limited.

  For example, if ink is applied on the gas diffusion layer, methods such as brush coating, spraying, roll coater, ink jet, and screen printing can be used. Alternatively, the ink is applied by a method such as bar coater, brush coating, spray, roll coater, ink jet, screen printing, etc., dried, and once separated on the surface of a polymer material such as polytetrafluoroethylene (PTFE) sheet or PTFE plate A method of forming a gas diffusion electrode by forming a catalyst layer on the material and then joining the gas diffusion layer by a method such as hot pressing may be selected.

  The gas diffusion electrode thus produced can be pressure-bonded to an electrolyte membrane such as perfluorosulfonic acid polymer by hot pressing or the like to form a composite of the electrolyte membrane and electrode (Membrane Electrode Assembly, MEA).

  Or after applying the ink to a polymer material such as PTFE sheet or PTFE plate by brushing, spraying, roll coater, ink jet, screen printing, etc., and drying, once forming a catalyst layer on another material, The catalyst layer and the electrolyte membrane can be bonded to the electrolyte membrane such as perfluorosulfonic acid polymer by a method such as hot pressing, or by directly applying and drying ink on the electrolyte membrane such as perfluorosulfonic acid polymer. The MEA can also be formed by, for example, a method in which the gas diffusion layer is pressure-bonded to the catalyst layer by a method such as hot pressing after the joined body is manufactured.

  In general, the MEA produced as described above can be used as a fuel cell by forming a unit cell by disposing a separator on the outside thereof and stacking the unit cells according to a required output.

<Measurement of physical properties of carbon materials>
In showing examples of the gas diffusion electrode and the fuel cell of the present invention, 11 types of carbon materials a to k were prepared as carbon materials to be used. Table 1 (Types of carbon materials and their physical properties) shows various physical properties of various carbon materials.

Nitrogen adsorption specific surface area was measured with nitrogen gas using an automatic specific surface area measuring device (BELSORP36, manufactured by Nippon Bell Co., Ltd.) after vacuum drying at 120 ° C, and the specific surface area S was determined by a one-point method based on the BET method. _BET was determined. Also, t plot analysis were calculated by extrapolating the measured values S _total and S _micro using an analysis program supplied with the device. The oxygen content is an elemental analysis value. The amount of water vapor adsorption was measured using a constant capacity water vapor adsorption device (Nippon Bell, BELSORP18), and the sample that had been pre-degassed for 2 hours at 120 ° C. and 1 Pa or lower was held at a constant temperature of 25 ° C. From the vacuum state to the saturated vapor pressure of water vapor at 25 ° C., water vapor was gradually supplied to gradually change the relative humidity, and the water vapor adsorption amount was measured. An adsorption isotherm was drawn from the obtained measurement results, and the water vapor adsorption amount at a relative humidity of 90% was read from the figure. In Table 1, the read water vapor amount is shown in terms of the water vapor volume in the standard state adsorbed per 1 g of the sample. The DBP oil absorption amount was determined by converting the DBP addition amount at the time of 70% of the maximum torque into the DBP oil absorption amount per 100 g of sample using an absorber meter (manufactured by Brabender).

<Preparation of platinum catalyst>
In a chloroplatinic acid aqueous solution, one selected from the carbon materials shown in Table 1 as a catalyst support carbon material is dispersed, kept at 50 ° C., added with hydrogen peroxide while stirring, and then Na ₂ S ₂ O. ₄ Aqueous solution was added to obtain a catalyst precursor. The catalyst precursor was filtered, washed with water, and dried, followed by reduction treatment at 300 ° C. for 3 hours in a 100% H ₂ stream to prepare a platinum catalyst in which 50% by mass of platinum metal was supported on the catalyst support carbon material.
<Standard coating ink production method>
Select one kind of carbon material as catalyst support carbon material A or B, take the prepared platinum catalyst supporting platinum metal in the procedure of <Preparation of catalyst support carbon material supporting platinum metal> in the container, and use the inner catalyst layer In the case of the coating ink, a conductive auxiliary agent carbon material was further selected from Table 1 and added to the container. To this was added a 5% Nafion solution (DE521 manufactured by DuPont), and after lightly stirring, the catalyst was pulverized with ultrasonic waves. Furthermore, butyl acetate was added while stirring, so that the solid content concentration of platinum metal and catalyst support carbon material A or B, and in the case of the inner layer, the conductive auxiliary agent carbon material and Nafion was 2% by mass. A catalyst aggregation ink in which a platinum catalyst and Nafion (electrolyte) were aggregated was prepared. Unless otherwise stated, in the case of the inner layer, the total amount of the catalyst support carbon material A and the conductive additive carbon material is 1 part by mass, in the case of the outer layer, the catalyst support carbon material B is 1 part by mass, and the ratio of Nafion is 1.5 parts by mass. Mixed.

  Also, take one type selected from the carbon materials listed in Table 1 as a gas diffusion carbon material in another container, add butyl acetate so that the concentration of the carbon material is 2% by mass, and pulverize the carbon material with ultrasound Then, a gas diffusion carbon material aggregation ink in which the gas diffusion carbon material was aggregated was prepared.

Next, the catalyst aggregation ink and the gas diffusion carbon material aggregation ink were mixed to prepare a coating ink having a solid content concentration of 2% by mass.
<Catalyst layer preparation method>
First, the outer layer coating ink was sprayed onto a Teflon (registered trademark) sheet, dried in argon at 80 ° C. for 10 minutes, and cooled to room temperature to form an outer catalyst layer. Next, the inner layer coating ink is sprayed onto the outer catalyst layer, dried in argon at 80 ° C. for 10 minutes, then dried in argon at 120 ° C. for 60 minutes, and a catalyst layer having a two-layer structure of an inner layer and an outer layer. Was made.

The platinum basis weight of the catalyst layer and the ratio of the inner layer to the outer layer are determined by cutting the catalyst layer on the prepared Teflon (registered trademark) sheet into 3 cm squares after the outer catalyst layer and the inner catalyst layer, respectively. After that, the mass of the Teflon (registered trademark) sheet after the catalyst layer was peeled off with a scraper was measured, the mass of the catalyst layer peeled off from the difference from the previous mass was calculated, and the solid content in the catalyst ink The amount of platinum is calculated from the ratio of platinum in the medium, and the amount of spray is adjusted so that the amount of platinum is 0.10 mg / cm ² and the target ratio of inner layer to outer layer is obtained.
<Production of MEA>
An MEA (membrane electrode assembly) was produced using the produced catalyst layer.

A Nafion membrane (N112 manufactured by DuPont) was cut into a 6 cm square, and the catalyst layer coated on the Teflon (registered trademark) sheet was cut into a 2.5 cm square with a cutter knife. These catalyst layers were used as an anode and a cathode, sandwiched so that there was no deviation at the center of the Nafion membrane, and pressed at 120 ° C. and 100 kg / cm ² for 10 minutes. After cooling to room temperature, only the Teflon (registered trademark) sheet for both the anode and the cathode was carefully peeled off to fix the anode and cathode catalyst layers to the Nafion membrane. Next, cut a commercially available carbon cloth (LT-1200W manufactured by E-TEK) as a gas diffusion layer into a square of 2.5 cm square, sandwich it so that there is no deviation between the anode and the cathode, and press at 120 ° C, 50 kg / cm ² for 10 minutes And created the MEA. The mass of the fixed catalyst layer is determined from the difference between the mass of the Teflon (registered trademark) sheet with the catalyst layer before pressing and the mass of the Teflon (registered trademark) sheet peeled off after pressing, and the mass ratio of the composition of the catalyst layer is determined. The platinum weight was calculated and confirmed to be 0.1 mg / cm ² .
<Fuel cell performance evaluation conditions>
The produced MEAs were each incorporated in a cell, and the fuel cell performance was evaluated by the following procedure using a fuel cell measuring device.

First, performance evaluation was performed with the following conditions as typical conditions for “high humidification and high load”. The gas was supplied to the cathode with air and pure hydrogen to the anode so that the utilization rates would be 35% and 70%, respectively, and each gas pressure was adjusted with a back pressure valve provided downstream of the cell, and 0.1 MPa Set to. The cell temperature was set to 80 ° C., and the supplied air and pure hydrogen were bubbled in distilled water kept at 80 ° C. and humidified. After supplying a gas to the cell under these conditions, increasing gradually loaded to 1000 mA / cm ^2, the load was fixed at 1000 mA / cm ^2, the inter-cell terminal voltage after the lapse of 60 minutes, "High humidification High Recorded as “load” performance.

Next, performance evaluation was performed using the following conditions as typical conditions of “low humidification and low load”. The gas was supplied to the cathode with air and pure hydrogen to the anode so that the utilization rates would be 35% and 70%, respectively, and each gas pressure was adjusted with a back pressure valve provided downstream of the cell, and 0.1 MPa Set to. The cell temperature was set at 80 ° C., and the supplied air and pure hydrogen were bubbled in distilled water kept at 40 ° C. and humidified. After supplying a gas to the cell under these conditions, by gradually increasing the load until 1000 mA / cm ^2, the load was fixed at 1000 mA / cm ^2, to lower the load to 100 mA / cm ² after a lapse of 30 minutes, 10 The voltage between the cell terminals after the lapse of minutes was recorded as “low humidification and low load” performance.
<Performance comparison 1>
First, as shown in Table 2, the catalyst support carbon material A is selected as j in Table 1, the conductive auxiliary agent carbon material Y as e in Table 1, and the gas diffusion carbon material as a in Table 1 as the inner catalyst layer. Then, a comparison was made using a two-layered catalyst layer in which h in Table 1 was selected as the catalyst support carbon material B and a in Table 1 was selected as the gas diffusion carbon material as the outer catalyst layer.

  In Comparative Example 1, the catalyst support carbon material A is shown in Table 1, j, the catalyst support carbon material B is shown in Table 1, h, the conductive additive carbon material Y is shown in Table 1, e, and the gas diffusion carbon material is shown in Table 1 as a. After mixing 5% Nafion solution (DuPont DE521) as an electrolyte material and diluting with ethanol to make a coating ink with a solid content concentration of 2% by mass, the carbon material is pulverized with ultrasonic waves, and then each component is uniform A mixed coating ink was prepared, and a catalyst layer having no inner layer and outer layer and having no aggregated phase structure was prepared by using this, and used for evaluation.

  Further, Comparative Example 2 shows catalyst support carbon material A as j in Table 1, conductive auxiliary agent carbon material Y as Table 1 e, gas diffusion carbon material as Table 1 a, and electrolyte material 5% Nafion solution (manufactured by DuPont). DE521) is mixed, diluted with ethanol so that the solid content concentration is 2% by mass, and the carbon material is pulverized with ultrasonic waves. H in Table 1 as material B, a in Table 1 as gas diffusion carbon material, 5% Nafion solution (DEPON manufactured by DuPont) as an electrolyte material, and diluted with ethanol so that the solid content concentration is 2% by mass, After the carbon material was pulverized with ultrasonic waves, an outer layer coating ink in which each component was uniformly mixed was prepared. For the catalyst layer, a two-layered catalyst layer having no aggregated phase structure was prepared by the method described in <Catalyst Layer Preparation Method> using these two types of coating inks, and used for evaluation.

  Further, in Example 1 and Comparative Examples 3 to 8, following the above <Standard Coating Ink Preparation Method>, an inner layer coating ink and an outer layer coating ink were prepared, and the catalyst layer was coated with these two types. A catalyst agglomerated phase comprising a catalyst carrier carbon material A, a conductive assistant carbon material, and an electrolyte material, which are produced by the method described in <Catalyst Layer Preparation Method> using ink and carrying a catalyst component, and a gas diffusion carbon material A catalyst comprising: an inner layer catalyst layer having a structure in which the gas diffusion carbon material aggregate phase is dispersed in the catalyst aggregate phase, a catalyst support carbon material B supporting a catalyst component, and an electrolyte material. A two-layer catalyst layer consisting of an agglomerated phase and a gas-diffusing carbon material agglomerated phase and having a structure in which the gas-diffusing carbon material agglomerated phase is dispersed in the catalyst agglomerated phase is prepared and evaluated. Used for. In Comparative Examples 3 to 8, a catalyst layer lacking any one or plural kinds of carbon materials was produced.

  The power generation performance when these catalyst layers were cathoded was compared. Note that the catalyst layer of Example 1 was used for all anodes.

  First, of the catalyst layers prepared in the above performance comparison, Example 1 having a two-layer structure and having a two-phase aggregate structure, a comparative example having neither of the two-layer structure and the two-phase aggregate structure as described above The cross-sectional structure of the catalyst layer of Comparative Example 2 having a 1- and 2-layer structure but not having a two-phase aggregate structure was observed.

  For the observation sample, the MEA used in the performance comparison was subjected to performance evaluation, taken out from the cell, and the gas diffusion layer was carefully peeled off using tweezers. Next, the MEA from which the gas diffusion layer had been peeled was cut out to a size of about 5 mm square with a cutter knife, and fixed to the cryomicrotome holder with carbon tape so that the cathode catalyst layer could be cut. The produced holder was set on a cryomicrotome, and a diamond trimming knife was set on the knife. At this time, the diamond trimming knife was set at an angle of about 10 degrees with respect to the traveling direction of the knife so that the catalyst layer was cut obliquely. Cutting was performed at least 100 times at a cutting temperature of −90 ° C. and a thickness of 50 nm per time in the depth direction of the catalyst layer to prepare a cut surface of the catalyst layer. The catalyst layer on which these cut surfaces were prepared was set in an electron microscope holder together with the holder, and a secondary electron image and a reflected electron image were observed at a magnification of 10,000 times.

  First, from the secondary electron images, it could be determined that the catalyst layers of Example 1 and Comparative Example 2 clearly formed a two-layer structure due to the difference in the shape of the carbon materials constituting them. In contrast, Comparative Example 1 was confirmed to be composed of a plurality of carbon material shapes, but was uniformly dispersed and confirmed to have a single-layer structure.

  In addition, the catalyst layers of Comparative Example 1 and Comparative Example 2 were observed with a uniform contrast of the reflected electron image, except where the electrolyte material was estimated to be agglomerated from the secondary electron image, No agglomerated phase of carbon material (gas diffusion carbon material agglomerated phase) with no catalyst component supported was found. On the other hand, in the catalyst layer of Example 1, both the inner layer and the outer layer have a dark contrast in the reflected electron image, that is, where the carbon material is clearly present in the secondary electron image, that is, the catalyst component. It was observed that the agglomerated phase (gas diffusion carbon material agglomerated phase) of the carbon material on which no carbon was supported was distributed in islands. In order to identify more quantitatively, a reflected electron image is captured as electronic information with a resolution of 272 DPI × 272 DPI or higher at a magnification of 10,000 and a brightness of 256 colors in a part of the inner layer, and the captured image Using the image analysis software, the brightness was binarized so that the range from the darker to the 110th layer was displayed in black, and the range from the 111th layer to the brighter layer up to the 256th layer was white. Next, each black point was expanded once to recognize adjacent points. Further, a hole filling process was executed, and blank portions in the range were filled and recognized as being in the same range. Finally, a degeneration process for returning the expanded portion was performed to clarify the target range. Then, the circle equivalent diameter of each black part was calculated from the area of each black part, and all parts less than 300 nm were cut. Of the remaining black parts, the number of black parts with carbon material in the secondary electron image with the same field of view was eight. Furthermore, even if the black part with an equivalent circle diameter of 500 nm or less was deleted, the number of black parts with carbon material present in the secondary electron image in the same field of view of the remaining black part was three. . When the outer layer was analyzed in the same manner, it was found that the number of equivalent circle diameters was 300 nm or more.

  Comparing Comparative Examples 1 and 2 and Example 1 as shown in Table 1, Example 1 using a two-layered catalyst layer having an aggregated phase structure in both the inner layer and the outer layer showed the most excellent characteristics, and the inner layer and outer layer Comparative Example 1 using a catalyst layer having no aggregated phase structure, and Comparative Example 2 using a catalyst layer having an inner layer and an outer layer but each having no aggregated phase structure are In comparison, the characteristics were low in both high humidification high load conditions and low humidification low load conditions.

Further, when comparing Example 1 and Comparative Examples 3 to 8 using a two-layer structure catalyst layer having an aggregated phase structure in both the inner layer and the outer layer, the catalyst support carbon material A, the conductive auxiliary agent carbon material, and the gas diffusion are formed in the inner layer. Example 1 containing the carbon material and containing the catalyst support carbon material B and the gas diffusion carbon material in the outer layer shows the most excellent characteristics, and compared with Example 1, at least one of the inner layer or outer layer carbon materials. Comparative Examples 3 to 8 in which the type was lost had characteristics lower than those of Example 1.
<Performance comparison 2>
As shown in Table 3, a to k in Table 1 are selected for the catalyst support carbon material A, e in Table 1 is selected for the conductive additive carbon material Y, and a in Table 1 is selected for the gas diffusion carbon material as the inner catalyst layer. The catalyst carrier carbon material B is different in the type of catalyst carrier carbon material A in the inner layer by using a two-layered catalyst layer in which h in Table 1 is selected as the catalyst carrier carbon material B and a in Table 1 is selected as the gas diffusion carbon material as the outer catalyst layer. A comparison was made.

  For the catalyst layer, following the above <Standard coating ink preparation method>, the inner layer coating ink and the outer layer coating ink were prepared, and using these two types of coating inks, the method described in <Catalyst layer preparation method> It was produced with. The produced catalyst layers each have an aggregated phase structure in the inner layer and the outer layer, and the power generation performance when these catalyst layers are cathoded was compared. Note that the catalyst layer of Example 1 was used for all anodes.

As shown in Table 3, the specific surface area S _BET by BET evaluation is 1000 m ² / g or more and 4000 m ² / g or less, and the ratio S _{micro of the} micropore surface area S _micro and the total surface area S _total of 2 nm or less diameter by t plot analysis Examples 1 to 5 using the catalyst support carbon material A of the present invention having / S _total of 0.5 or more showed excellent performance in both high humidification high load conditions and low humidification low load conditions. Among them, Examples 1 and 3 to 5 using carbon materials h, i, j, and k having a water vapor adsorption amount of 100 mL / g or more at 25 ° C. and a relative humidity of 90% as the catalyst support carbon material A are low humidification and low. It showed very good characteristics even under load conditions.

In contrast, a carbon material having a specific surface area S _BET by BET evaluation of less than 1000 m ² / g or a ratio S _micro / S _{total of the} micropore surface area S _micro to the total surface area S _total of less than 0.5 is defined as a catalyst support carbon material A. Comparative Examples 9 to 14 resulted in particularly poor characteristics of low humidification and low load.
<Performance comparison 3>
As shown in Table 4, j in Table 1 for the catalyst support carbon material A, e in Table 1 for the conductive additive carbon material Y, and a in Table 1 for the gas diffusion carbon material are selected for the inner catalyst layer, Types of catalyst carrier carbon material B in the outer layer using a catalyst catalyst carbon material B with a two-layer structure catalyst layer selected from a to j in Table 1 and gas diffusion carbon material a in Table 1 as the outer catalyst layer. Comparisons were made when they were different.

  The catalyst layer was prepared as described in <Catalyst Layer Preparation Method> using the coating ink for the inner layer and the coating ink for the outer layer according to the above <Standard Application Method for Preparation of Ink> and using these two types of application inks. It was produced by the method. The produced catalyst layers each have an aggregated phase structure in the inner layer and the outer layer, and the power generation performance when these catalyst layers are cathoded was compared. Note that the catalyst layer of Example 1 was used for all anodes.

As shown in Table 4, the ratio X / S _BET between the DBP oil absorption amount XmL / 100 g and the specific surface area S _BET according to BET evaluation is 0.2 using the catalyst support carbon material B of the present invention, which is 3.0 or less. And 6-9 showed the performance which was excellent in high humidification high load conditions and low humidification low load conditions.

On the other hand, Comparative Examples 15 to 19 where the ratio X / S _BET between the DBP oil absorption amount XmL / 100 g and the specific surface area S _BET by BET evaluation is outside the range of 0.2 or more and 3.0 or less is the catalyst support carbon material B. In particular, the characteristics of high humidification and high load were poor.
<Performance comparison 4>
As shown in Table 5, select j in Table 1 for catalyst support carbon material A, a to j in Table 1 for conductive auxiliary carbon material Y, and a in Table 1 for gas diffusion carbon material as the inner catalyst layer. Then, using a two-layer catalyst layer in which h in Table 1 is selected for the catalyst support carbon material B and a in Table 1 for the gas diffusion carbon material is selected as the outer catalyst layer, the conductive auxiliary agent carbon material Y of the inner layer is selected. Comparison was made when the types were different. Further, when the conductive auxiliary carbon material Y was e in Table 1, a comparison was also made when the mass ratio Y / (A + Y) of the conductive auxiliary carbon material Y to the catalyst support carbon material A was changed.

  The catalyst layer was prepared as described in <Catalyst Layer Preparation Method> using the coating ink for the inner layer and the coating ink for the outer layer according to the above <Standard Application Method for Preparation of Ink> and using these two types of application inks. It was produced by the method. The produced catalyst layers each have an aggregated phase structure in the inner layer and the outer layer, and the power generation performance when these catalyst layers are cathoded was compared. Note that the catalyst layer of Example 1 was used for all anodes.

Examples 10-13, 1, 20 in which the mass ratio Y / (A + Y) of the conductive additive carbon material Y to the catalyst support carbon material A was fixed to 0.2 and the type of conductive additive carbon material Y was changed. ~ 24, carbon material a, b, c, e, h with DBP oil absorption XmL / 100g and specific surface area S _BET ratio X / S _BET by BET evaluation of 0.2 to 3.0 Examples 1, 10 to 12 and 22 used as the carbon material Y showed excellent performance under both high humidification and high load conditions and low humidification and low load conditions.

On the other hand, carbon material d, f, g, i, j whose ratio X / S _BET between DBP oil absorption XmL / 100g and specific surface area S _BET by BET evaluation is outside the range of 0.2 or more and 3.0 or less is conductive aid. Examples 13, 20, 21, 23, and 24, which are carbon materials Y, have lower characteristics than those in which X / S _BET is in the range of 0.2 to 3.0 in both high humidification and high load conditions and low humidification and low load conditions. As a result.

Also, Examples 1, 14 to 19 in which the mass ratio Y / (A + Y) of the conductive assistant carbon material Y to the catalyst support carbon material A was changed as e in Table 1 as the type of the conductive assistant carbon material Y. When the mass ratio Y / (A + Y) is 0.05 or more and 0.4 or less, Examples 1 and 15 to 18 are examples in which the mass ratio Y / (A + Y) is less than 0.05 or more than 0.4. And showed better properties than 19.
<Performance comparison 5>
As shown in Table 6, j in Table 1 for the catalyst support carbon material A, e in Table 1 for the conductive additive carbon material Y, and a in Table 1 for the gas diffusion carbon material are selected as the inner catalyst layer, The catalyst carrier carbon material contained in each of the inner layer and the outer layer using a two-layer catalyst layer in which h in Table 1 is selected as the catalyst support carbon material B and a in Table 1 is selected as the gas diffusion carbon material as the outer catalyst layer. Comparison was made when the mass ratio A / (A + B) of A and the catalyst-supporting carbon material B was changed. Further, a comparison was also made when the mass ratio of the gas diffusion carbon material contained in the inner layer and the outer layer was changed in each layer when the mass cost A / (A + B) was 0.7.

  The catalyst layer was prepared as described in <Catalyst Layer Preparation Method> using the coating ink for the inner layer and the coating ink for the outer layer according to the above <Standard Application Method for Preparation of Ink> and using these two types of application inks. It was produced by the method. The produced catalyst layers each have an aggregated phase structure in the inner layer and the outer layer, and the power generation performance when these catalyst layers are cathoded was compared. Note that the catalyst layer of Example 1 was used for all anodes.

When comparing Examples 25 to 28, 1, 39 to 41 when the content of the gas diffusion carbon material of the inner layer and the outer layer is 10% by mass, the mass ratio A / (of the catalyst support carbon material A and the catalyst support carbon material B Examples 26 to 28, 1, 39, 40 in which A + B) is 0.2 or more and 0.95 or less, Example 25 in which the mass ratio A / (A + B) is less than 0.2, or mass ratio A / (A + B ) Was superior to Example 41 having a value exceeding 0.95, both showed excellent performance under both high humidification and high load conditions and low humidification and low load conditions. In addition, when the mass ratio A / (A + B) of the catalyst support carbon material A and the catalyst support carbon material B is 0.70, and the contents of the gas diffusion carbon material in the inner layer are changed, 29 to 33 are compared. Examples 1 and 30 to 32 in which the content of the gas diffusion carbon material in the inner catalyst layer is in the range of 3% by mass to 30% by mass were excellent in both high humidification and high load conditions and low humidification and low load conditions. Showed performance. In particular, Examples 1, 30, and 31 in which the content of the gas diffusion carbon material in the inner catalyst layer is in the range of 5% by mass or more and 25% by mass or less are high humidification high load conditions, low humidification low load conditions, It showed balanced characteristics. Further, when the mass ratio A / (A + B) of the catalyst support carbon material A and the catalyst support carbon material B is 0.70, and the contents of the gas diffusion carbon material in the outer layer are changed, Examples 1 and 34 to 38 are compared. In Examples 1 and 35 to 37, the content of the gas diffusion carbon material in the outer catalyst layer in the range of 3% by mass to 30% by mass was excellent in both high humidification and high load conditions and low humidification and low load conditions. Showed performance. In particular, Examples 1, 35, and 36 in which the content of the gas diffusion carbon material in the inner catalyst layer is in the range of 5% by mass or more and 25% by mass or less are high humidification high load conditions, low humidification low load conditions, It showed balanced characteristics.
<Durability test>
<Example of performance comparison 2> In the example showing excellent characteristics, the water vapor adsorption amounts V ₁₀ , V ₉₀ , V ₁₀ / V ₉₀ for the carbon materials h, i, j, k used for the catalyst support carbon material A These are shown in Table 7. Further, using these carbon materials h, i, j and k, catalysts H, I, J and K carrying platinum were prepared by the following method. A chloroplatinic acid aqueous solution and polyvinylpyrrolidone are placed in distilled water, and sodium borohydride is dissolved in distilled water while stirring at 90 ° C., and then poured into the aqueous solution to reduce chloroplatinic acid. Carbon materials h, i, j, and k were added to the aqueous solution, followed by stirring for 60 minutes, followed by filtration and washing. The obtained solid was vacuum-dried at 90 ° C., pulverized, and heat-treated at 250 ° C. for 1 hour in a hydrogen atmosphere to prepare catalysts H, I, J, and K. The catalyst was prepared so that the amount of platinum supported was 50% by mass.

The amount of water vapor adsorbed on the carbon material was measured using a constant capacity water vapor adsorption device (BELSORP18, manufactured by Nippon Bell Co., Ltd.). The water vapor was gradually supplied from the vacuum state to the saturated vapor pressure of water vapor at 25 ° C. to gradually change the relative humidity, and the water vapor adsorption amount was measured. The resulting drawn adsorption isotherm from the measurement results were read relative humidity of 10% and 90% of the water vapor adsorption amount of time as the V ₁₀ and V _90, respectively from FIG. In Table 10, the read water vapor amount is shown in terms of the water vapor volume in the standard state adsorbed per 1 g of the sample.

  The particle diameter of the platinum particles was estimated by the Scherrer equation from the half-value width of the platinum (111) peak of the powder X-ray diffraction spectrum of the catalyst obtained using an X-ray diffractometer (manufactured by Rigaku Corporation).

  Using catalysts H, I, J, and K in Table 7 as catalyst support carbon material A, select e in Table 1 for conductive aid carbon material Y and a in Table 1 for gas diffusion carbon material as the inner catalyst layer. Then, a durability performance test was conducted using a catalyst layer carbon material B having a two-layered catalyst layer in which h in Table 1 was selected as a catalyst carrier carbon material B and a in Table 1 was selected as a gas diffusion carbon material as an outer catalyst layer. For the catalyst layer, following the above <Standard coating ink preparation method>, the inner layer coating ink and the outer layer coating ink were prepared, and using these two types of coating inks, the method described in <Catalyst layer preparation method> It was produced with. The prepared catalyst layer had an inner layer and an outer layer each having an agglomerated phase structure, and an endurance performance test of MEA when these catalyst layers were cathoded was conducted. Note that the catalyst layer of Example 1 was used for the anode.

  In the durability performance test, the voltage between the cell terminals is first changed stepwise from the open circuit voltage (usually about 0.9 to 1.0 V) to 0.2 V, and the current density that flows when the cell terminal voltage is 0.8 V is measured. The performance. Next, a cycle in which the open voltage was held for 15 seconds and the cell terminal voltage was held at 0.5 V for 15 seconds was performed 4000 times, and then the battery performance was measured in the same manner as before the cycle to obtain the battery performance after the endurance test. As the gas, air was supplied to the cathode and pure hydrogen was supplied to the anode so that the utilization rates would be 50% and 80%, respectively, and each gas pressure was adjusted to 0.1 MPa with a back pressure valve provided downstream of the cell. . The cell temperature was set to 70 ° C., and the supplied air and pure hydrogen were bubbled in distilled water kept at 50 ° C. and humidified.

Table 8 shows the battery performance results of each MEA and the battery performance after the endurance test. Carbon materials j and k whose water vapor adsorption amount (V ₁₀ ) at 25 ° C. and relative humidity 10% is 2 ml / g or less and whose water vapor adsorption amount (V ₉₀ ) at 25 ° C. and relative humidity 90% is 400 ml / g or more. example 44 and 45 was used as a catalyst carrier carbon material a is, V90 is the initial battery performance even higher than that of example 42 using the carbon material h of less than 400 ml / g as a catalyst carrier carbon material a, V ₁₀ is It can be seen that the durability is lower than that of Example 43 in which the carbon material i exceeding 2 ml / g was used as the catalyst support carbon material A. Further, when Examples 44 and 45 showing excellent characteristics are compared, Example 44 using the carbon material j having a value of V ₁₀ / V ₉₀ of 0.02 or less as the catalyst support carbon material A is V ₁₀ / V ₉₀ It can be seen that the deterioration rate is further lower than that in Example 45 in which the carbon material k having a value of more than 0.02 is used as the catalyst support carbon material A, and exhibits particularly excellent durability performance.

1 Gas diffusion carbon material aggregation phase
2 Gas diffusion carbon material
3 Catalyst agglomerated phase
4 Catalyst support carbon material A carrying catalyst components
5 Catalyst support carbon material B carrying catalyst components
6 Electrolyte material
7 Conductive aid carbon material

Claims (4)

A fuel cell including a pair of catalyst layers sandwiching a proton conductive electrolyte membrane,
At least the catalyst layer of the cathode includes a catalyst component, an electrolyte material, and a carbon material, and the carbon material carries a catalyst carrier carbon material carrying the catalyst component, and a conductive auxiliary agent carbon material not carrying the catalyst component. When the result of the catalyst component from the three gas-diffusing carbon material not carrying, and consists of two kinds of the catalyst supporting carbon material is catalytic carrier carbon material a and the catalyst supporting carbon material B, and the cathode The catalyst layer has at least a two-layer structure;
The catalyst carrier carbon material A in which the inner layer on the side in contact with the proton conductive electrolyte membrane carries at least the catalyst component, the conductive auxiliary agent carbon material not carrying the catalyst component, the electrolyte material, and the catalyst The outer layer on the side not in contact with the proton-conducting electrolyte membrane comprises at least the catalyst carrier carbon material B carrying the catalyst component and the electrolyte material. And a layer made of the gas diffusion carbon material not supporting the catalyst component, and an inner layer of the catalyst layer,
The catalyst carrier carbon material A carrying at least the catalyst component, the conductive auxiliary agent carbon material not carrying the catalyst component, a catalyst aggregation phase formed by aggregating the component made of the electrolyte material, and at least the catalyst component Consisting of a two-phase mixed structure of a gas diffusion carbon material aggregated phase formed by agglomerating components composed of the gas diffusion carbon material not supporting
The outer layer of the catalyst layer is
Aggregating at least the catalyst carrier carbon material B supporting the catalyst component, a catalyst aggregation phase formed by aggregating the component composed of the electrolyte material, and a component composed of the gas diffusion carbon material not supporting at least the catalyst component A gas diffusion carbon material aggregated phase, and the inner layer and the outer layer in each layer, the catalyst aggregated phase is a continuum, and the gas diffusion carbon material aggregated phase is Microstructure having a structure dispersed in the catalyst agglomerated phase and having a specific surface area S _BET of 1000 m ² / g or more and 4000 m ² / g or less by t-plot analysis of the catalyst support carbon material A according to BET evaluation. The ratio S _micro / S _{total of the} pore surface area S _micro and the total surface area S _total is 0.5 or more, and the ratio X / S of the DBP oil absorption XmL / 100 g of the catalyst support carbon material B and the specific surface area S _BET by BET evaluation _BET is, is 0.2 to 3.0 Fuel cell, wherein the door.   2. The fuel cell according to claim 1, wherein a mass ratio A / (A + B) of the catalyst support carbon material A and the catalyst support carbon material B in the catalyst layer is 0.2 or more and 0.95 or less. The catalyst carrier carbon material A has a water vapor adsorption amount V ₁₀ at 25 ° C. and a relative humidity of 10% of 2 ml / g or less, and the catalyst carrier carbon material A has a water vapor adsorption amount V ₉₀ at 25 ° C. and a relative humidity of 90%. 3. The fuel cell according to claim 1, wherein the fuel cell is 400 ml / g or more. The ratio V ₁₀ / V ₉₀ of the water vapor adsorption amount V ₁₀ at 25 ° C. and relative humidity 10% of the catalyst support carbon material A and the water vapor adsorption amount V ₉₀ at 25 ° C. and relative humidity 90% of the catalyst support carbon material A is the fuel cell according to any one of claims 1 to 3 is 0.002 or less.

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