JP2009026501A - Electrolyte membrane-electrode assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte membrane-electrode assembly (MEA) superior in power generation performance and durability. <P>SOLUTION: The electrolyte membrane-electrode assembly includes a polymer electrolyte membrane, a cathode catalyst layer and a cathode side gas diffusive electrode arranged in order on one side of the polymer electrolyte membrane, and an anode catalyst layer and an anode side gas diffusive electrode arranged in order on the other side of the polymer electrolyte membrane. The cathode catalyst layer includes a carrier in which a catalyst component is carried, a substance having an oxygen storage and releasing action, and a polymer electrolyte, and/or the anode catalyst layer includes a carrier in which the catalyst component is carried, a substance having hydrophilicity, and the polymer electrolyte. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrolyte membrane-electrode assembly (MEA), and more particularly to an electrolyte membrane-electrode assembly for a fuel cell. In particular, the present invention relates to an electrolyte membrane-electrode assembly (MEA) excellent in power generation performance and durability, particularly to an electrolyte membrane-electrode assembly for a fuel cell.

  In recent years, in response to social demands and trends against the background of energy and environmental problems, fuel cells that can operate at room temperature and obtain high output density have attracted attention as power sources for electric vehicles and stationary power sources. A fuel cell is a clean power generation system in which the product of an electrode reaction is water in principle and has almost no adverse effect on the global environment. In particular, the polymer electrolyte fuel cell is expected as a power source for electric vehicles because it operates at a relatively low temperature. In general, the polymer electrolyte fuel cell has a structure in which an electrolyte membrane-electrode assembly is sandwiched between separators. In the electrolyte membrane-electrode assembly, a polymer electrolyte membrane is sandwiched between a pair of electrode catalyst layers and a gas diffusing electrode (gas diffusion layer; GDL).

In a polymer electrolyte fuel cell having an MEA as described above, an electrode reaction represented by the following reaction formula is allowed to proceed in accordance with the polarity of both electrodes (cathode and anode) sandwiching the polymer electrolyte membrane. Are getting electrical energy. First, hydrogen contained in the fuel gas supplied to the anode (hydrogen electrode) side is oxidized by the catalyst component to become protons and electrons (2H ₂ → 4H ⁺ + 4e ⁻ : reaction 1). Next, the generated protons pass through the solid polymer electrolyte contained in the electrode catalyst layer and the solid polymer electrolyte membrane in contact with the electrode catalyst layer, and reach the cathode (oxygen electrode) side electrode catalyst layer. In addition, the electrons generated in the anode-side electrode catalyst layer include the conductive carrier constituting the electrode catalyst layer, the gas diffusion layer in contact with the side of the electrode catalyst layer different from the solid polymer electrolyte membrane, the separator, and the outside. The cathode side electrode catalyst layer is reached through the circuit. The protons and electrons that have reached the cathode-side electrode catalyst layer react with oxygen contained in the oxidant gas supplied to the cathode side to generate water (O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O: Reaction 2). . In the fuel cell, electricity can be taken out through the above-described electrochemical reaction.

In the electrochemical reaction, hydrogen ions (H ⁺ ) (hereinafter also referred to as “protons”) generated by the reaction 1 on the anode side permeate the solid polymer electrolyte membrane in a hydrated state (H ₃ O ⁺ ). (Spread. Protons that have passed through the membrane are supplied to the reaction 2 together with oxygen and electrons that have permeated (diffused) through the gas diffusion layer at the cathode. That is, the reaction at the anode and the cathode proceeds at the interface between the catalyst in the electrode catalyst layer and the solid polymer electrolyte, with the electrode catalyst layer in close contact with the electrolyte membrane as a reaction site. Therefore, if the interface between the catalyst and the polymer electrolyte increases and the formation of the interface becomes uniform, the above reactions 1 and 2 proceed more smoothly and actively.

In general, as the catalyst in the electrode catalyst layer, a conductive carrier (carbon black or the like) carrying platinum or a platinum alloy is used. Here, in order for the reactions 1 and 2 to proceed smoothly and actively, the surface (reduction / oxidation) state of platinum or platinum alloy and the state of surface adsorbed species are important. For example, in order to generate protons by reaction 1 on the anode side, hydrogen that is adsorbed (desorbed) on the surface of platinum that is an active site, hydrogen that is coordinated on the platinum surface, and H ₂ O or platinum present in the vicinity of platinum It is estimated that H ₂ O coordinated on the surface is important. On the other hand, on the cathode side, H ₂ O can be generated by the formula, reaction 2, by oxygen adsorbed (desorbed) on the surface of platinum as an active site, oxygen coordinated on the platinum surface, and in the vicinity of platinum. such as H _{2 O} to coordinate in H 2 _O and the platinum surface is presumed importance.

  Therefore, it is important to increase the number of adsorbed and coordinated species on the surface of platinum, which is the active site, and to improve activation and poisoning resistance. In order to achieve such an object, a technique such as addition of a complex oxide in the electrode catalyst layer has been proposed as a catalyst species used for the anode and cathode (for example, Patent Document 1).

Patent Document 1 proposes a catalyst in which a composite oxide containing a noble metal element and an element constituting a non-stoichiometric oxide is supported on a carbon support as a cathode electrode catalyst species. Here, as the composite oxide (A _a B _b C _c O _x ), one or more noble metal elements (A) including platinum and one or more non-stoichiometric oxides (B) including cerium are used. And any metal element (C). As a result, oxygen that is supplied to the cathode catalyst layer is taken in (adsorbed, absorbed, or occluded) by the elements constituting the non-stoichiometric oxide in the composite oxide, and supplied to adjacent noble metal elements, thereby improving oxygen utilization efficiency. The activity is improved.
JP 2006-66255 A

  However, in Patent Document 1, since the noble metal (Pt) is compounded, the noble metal exists in the crystal lattice. For this reason, the catalyst according to Patent Document 1 cannot effectively catalyze the reduction reaction of oxygen because the noble metal exists in the crystal lattice and cannot contact the oxygen efficiently. Moreover, in patent document 1, in order to make a noble metal exist in a crystal lattice, it is necessary to make the magnitude | size of a noble metal particle small. However, when the particle size is too small, the noble metal particles are easily eluted and cannot fully exhibit the catalytic action.

  Therefore, the present invention has been made in view of the above circumstances, and an object thereof is to provide an electrolyte membrane-electrode assembly (MEA) having excellent power generation performance and durability.

  As a result of intensive studies to solve the above problems, the present inventor has arranged a substance having an oxygen storage / release action in the cathode catalyst layer, or a substance having hydrophilicity in the anode catalyst layer. It has been found that the power generation performance and durability of the catalyst layer can be improved. Based on the above findings, the present invention has been completed.

  The electrolyte membrane-electrode assembly (MEA) of the present invention is excellent in power generation performance and durability.

  A first aspect of the present invention is a polymer electrolyte membrane, a cathode catalyst layer and a cathode-side gas diffusible electrode sequentially disposed on one side of the polymer electrolyte membrane, and the other side of the polymer electrolyte membrane. An electrolyte membrane-electrode assembly having an anode catalyst layer and an anode-side gas diffusive electrode sequentially disposed on the cathode catalyst layer, wherein the cathode catalyst layer has a carrier carrying a catalyst component, and an oxygen storage / release function. And / or a polymer electrolyte, and / or the anode catalyst layer includes a carrier on which a catalyst component is supported, a hydrophilic substance, and a polymer electrolyte. Provide the body.

Conventionally, various methods have been tried to facilitate and activate the above reaction 1 (2H ₂ → 4H ⁺ + 4e ⁻ ) and reaction 2 (O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O) in the anode and cathode catalyst layers. Has been. For example, there is an increase in the interface between the catalyst and the polymer electrolyte (ionomer) in the electrode catalyst layer and the uniform formation of the interface. In addition to the above, in the anode catalyst layer, the diffusion permeability and proton conductivity of the reaction gas (hydrogen) are improved, and in the cathode catalyst layer, the diffusion permeability and utilization efficiency of the reaction gas (oxygen) are improved. Diffusion and removal of the water has been reported. Furthermore, in the electrode catalyst layers of the anode and the cathode, it is not possible to sufficiently improve performance (activity) and durability simply by solving these technical problems individually. Therefore, it is important to optimize the bipolar catalyst layer and to maximize the synergistic effect of the anode and cathode catalyst layer and to solve the trade-off.

  However, in the conventional fuel cell, the following problems have been pointed out in the anode and cathode catalyst layers. That is, in the polymer electrolyte fuel cell using hydrogen gas as fuel, the deterioration of poisoning of the anode catalyst layer due to carbon monoxide is very small compared to the fuel cell using methanol, ethanol or the like as a fuel (reformed type). . For this reason, practical problems include improving the diffusion permeability of the reaction gas (hydrogen) at the anode electrode and promoting the proton generation reaction.

  However, since hydrogen has a smaller molecule (diameter) than other gas species, diffusion permeability (gas diffusivity, Knunsen diffusivity, etc.) is very high (diffusion rate or diffusion coefficient is large). Therefore, it is considered that a porous structure having fine pores such as a conventional gas diffusion layer (GDL) or an electrode catalyst layer has high hydrogen diffusion permeability.

  Therefore, in the anode catalyst layer, it is presumed that promotion of proton generation reaction and improvement of proton conductivity are important issues. In order to improve the proton production reaction and proton conductivity in the anode catalyst layer, it is necessary to keep the water content of the electrolyte (ionomer) contained in the electrode catalyst layer in a high water content state.

  The water content of the ionomer is most effective when the amount of sulfonic acid groups in the electrolyte molecular skeleton (side chain) is increased (lowering the EW value), but there is also a limit to the sulfonic acid groups that can be introduced into the molecular skeleton. . Therefore, there is a need for a new solution that maintains and adjusts the anode electrode catalyst layer in a high water content state, promotes the proton generation reaction, and increases the conductivity of the generated protons.

  In addition, reducing the activation overvoltage of the cathode catalyst layer (improving the oxygen reduction activity) is effective in improving the performance and durability of the polymer electrolyte fuel cell. Improvements in utilization efficiency, diffusion and removal of generated water are issues.

  Compared to hydrogen diffusion permeability, oxygen diffusion permeability is considered to be strongly influenced by the microporous structure of porous structures such as gas diffusion layers and electrode catalyst layers. Improvements have been made. The improvement of the microporous structure of the porous structure is effective for the diffusion permeability of the reaction gas (oxygen) and the diffusion and removal of the produced water, but the effect of dramatically improving the oxygen utilization efficiency has not been obtained. It was the actual situation.

  Therefore, in the cathode catalyst layer, it is presumed that improvement of diffusion permeability and utilization efficiency of the reaction gas (oxygen) is an important issue. In order to improve oxygen diffusion permeability and oxygen utilization efficiency in the cathode catalyst layer, it is necessary to maintain a high state (concentration) of oxygen that diffuses and dissolves in the electrolyte (ionomer) contained in the electrode catalyst layer. It is.

  In terms of oxygen diffusibility and solubility in ionomers, increasing the amount of sulfonic acid groups in the electrolyte molecular skeleton (side chain) (decreasing the EW value) to improve oxygen solubility is the most effective, but improving ionomers There are also limitations. Therefore, there is a need for a new solution that maintains and adjusts the ionomer in the cathode electrode catalyst layer in a highly water-containing state, promotes the proton generation reaction, and increases the conductivity of the generated protons.

According to the present invention, a substance having an oxygen storage / release action is disposed in the cathode catalyst layer. By this arrangement, a substance having an oxygen storage / release action is arranged in the vicinity of the catalyst component such as Pt or Pt alloy. Therefore, adsorption oxygen and lattice oxygen can be supplied to the surface of the catalyst component, so that the oxygen reduction activity can be improved. In addition, with this arrangement, oxygen that diffuses and dissolves in the polymer electrolyte (ionomer) contained in the catalyst layer can be maintained at a high concentration, so that the oxygen reduction reaction can be promoted. In particular, oxygen that diffuses and dissolves in the polymer electrolyte (ionomer) contained in the catalyst layer under low oxygen conditions or under high load operation can be maintained at a high concentration, so that the oxygen reduction reaction can be promoted. .

  Generally, in a cyclic voltammogram (CV) of a platinum plate or a platinum wire, a platinum oxidation reaction proceeds from around 0.8V. On the other hand, in the CV of platinum-supporting carbon, the platinum oxidation reaction proceeds from around 0.65V. Therefore, in the conventional platinum-supported carbon, the oxidation-reduction cycle of platinum proceeds at a lower potential under normal operating conditions (0.6 V (nearly rated 1 A) to 0.95 V (natural potential or idle holding potential)). Platinum dissolution proceeds. However, according to the present invention, since the substance having an oxygen storage / release action is disposed in the cathode catalyst layer, it is adsorbed (desorbed) on the surface of the catalyst component such as platinum which is the active site, and is disposed on the surface of the platinum. Increased oxygen increases. For this reason, when a substance having an oxygen storage / release action is present in the vicinity of the platinum particles on the carbon or in the vicinity of the platinum-supporting carbon, an oxygen coating layer (PtOx) is formed on the surface of the platinum particles under normal operating conditions. It is easy to be maintained. For this reason, even if the oxidation-reduction cycle of platinum proceeds, platinum dissolution can be suppressed.

  According to the present invention, a hydrophilic substance is disposed in the anode catalyst layer. With this arrangement, a hydrophilic substance is arranged in the vicinity of the catalyst component such as Pt or Pt alloy. Therefore, since the coordination water can be supplied in the vicinity of the catalyst component on the carrier, the hydrogen oxidation activity can be improved. In addition, with this arrangement, the water content of the polymer electrolyte (ionomer) contained in the catalyst layer can always be maintained at a high water content, so that the proton generation reaction can be promoted and the proton conductivity can be improved. In particular, the water content of the polymer electrolyte (ionomer) contained in the catalyst layer can be maintained at a high water content under low humidification conditions or under high load operation. Therefore, in the anode catalyst layer according to the present invention, it is possible to promote proton generation reaction and improve proton conductivity.

  Therefore, the electrolyte membrane-electrode assembly (MEA) using the cathode catalyst layer and / or the anode catalyst layer according to the present invention is excellent in power generation performance and durability.

  Embodiments of the present invention will be described below.

  In the present invention, the cathode catalyst layer includes a carrier on which the catalyst component is supported, a substance having an oxygen storage / release action, and a polymer electrolyte, and / or the anode catalyst layer is a carrier on which the catalyst component is supported. And a hydrophilic substance and a polymer electrolyte. Here, in consideration of power generation performance and durability, it is preferable to dispose a substance having an oxygen storage / release action at least in the cathode catalyst layer. More preferably, it is preferable to dispose a substance having an oxygen storage / release action in the cathode catalyst layer and a substance having hydrophilicity in the anode catalyst layer.

In the present invention, the substance having an oxygen storage / release action disposed in the cathode catalyst layer is not particularly limited as long as it has an oxygen storage / release action, and a known substance can be used. Specifically, a complex oxide of rare earth elements can be given. Here, the complex oxide of the rare earth element is not particularly limited as long as it has an oxygen storage / release action, and is disclosed in JP-A-10-216509, JP-A-10-218620, and JP-A-2000-072437. JP-A-2000-072447, JP-A-2000-128537, JP-A-2004-337840, JP-A-2005-296880, JP-A-2006-068677, etc. Can be used. More _{specifically, CeO 2, ZrO 2, Ce} x1 Zr 1-x1 O Y1 (x1 is an atomic ratio of Ce, which is 0 <x1 <1, Y1 is satisfied valences of the respective components Pr _x2 Zr _1-x2 O _Y2 (x2 is the atomic ratio of Pr, 0 <x2 <1, Y2 satisfies the valence of each of the above components) And Pr _x3 Ce _1-x3 O _Y3 (x3 is the atomic ratio of Pr, 0 <x3 <1, Y3 is the valence of each of the above components) Preferably, it is the number of oxygen atoms necessary for satisfaction. Such a substance can supply a sufficient amount of adsorbed oxygen and lattice oxygen to the surface of the catalyst component, and can maintain a high concentration of oxygen that diffuses and dissolves in the electrolyte (ionomer) contained in the catalyst layer. For this reason, oxygen reduction activity can be improved. In particular, the oxygen reduction reaction can be promoted because oxygen that diffuses and dissolves in the electrolyte (ionomer) contained in the catalyst layer can be maintained at a high concentration under low oxygen conditions or under high load operation. Further, adsorbed oxygen and lattice oxygen of a substance having an oxygen storage / release action can be supplied to the catalyst component surface over a range of low potential to high potential (near 0.6 V (rated) to 0.95 V). For this reason, oxygen adsorbed (desorbed) on the surface of platinum, which is an active site, and oxygen coordinated on the platinum surface increase, whereby an oxygen coating layer (eg, PtO _x ) is formed on the surface of the catalyst component. Therefore, the oxidation-reduction cycle of the catalyst component is difficult to occur, and elution of the catalyst component (particularly platinum) can be effectively suppressed. The substance having an oxygen storage / release action may be used alone or in the form of a mixture of two or more. In the present invention, the substance having the oxygen storage / release action is not combined with the catalyst component used in the cathode catalyst layer, that is, the substance having the oxygen storage / release action and the catalyst component used in the cathode catalyst layer are combined. Does not form oxides. When the substance having the oxygen storage / release action and the catalyst component are present separately, the catalyst component can function regardless of entering and exiting from the crystal lattice, so that the catalyst component can exhibit a desired effect more effectively.

  In addition, the amount of the substance having an oxygen storage / release action according to the present invention disposed in the cathode catalyst layer is not particularly limited as long as it is an amount capable of promoting the oxygen reduction reaction and suppressing the elution of the catalyst component. Preferably, the substance having an oxygen storage / release action is contained in a content of the substance having an oxygen storage / release action from 0.01 to the total amount of the substance having the oxygen storage / release action, the catalyst component, the carrier and the polymer electrolyte. It arrange | positions in the quantity which will be 20 mass%. The content of the substance having an oxygen storage / release action is more preferably 0.1 to 15% by mass, still more preferably 0, based on the total amount of the substance having an oxygen storage / release action, the catalyst component, the carrier and the polymer electrolyte. .1 to 10% by mass. Within such a range, in the cathode catalyst layer, a sufficient amount of a substance having an oxygen storage / release action can be disposed in the vicinity of the catalyst component such as Pt or Pt alloy. Therefore, a sufficient amount of adsorbed oxygen and lattice oxygen can be supplied to the catalyst component surface, and the oxygen reduction activity can be improved. Further, adsorbed oxygen and lattice oxygen of a substance having an oxygen storage / release action can be supplied to the catalyst component surface over a range of low potential to high potential (near 0.6 V (rated) to 0.95 V). For this reason, an oxygen coating layer is formed on the surface of the catalyst component, and the oxidation-reduction cycle of the catalyst component hardly occurs, and elution of the catalyst component (particularly platinum) can be effectively suppressed.

  Furthermore, the shape and size of the substance having an oxygen storage / release action according to the present invention are not particularly limited. The shape of the substance having an oxygen storage / release action is preferably granular. The average particle diameter of the substance having an oxygen storage / release action at this time is also not particularly limited. Preferably, the average particle size of the substance having an oxygen storage / release action is 1 μm or less, more preferably 1 to 100 nm, and particularly preferably 5 to 50 nm. Within such a range, when a catalyst component such as Pt or Pt alloy is supported on a substance having an oxygen storage / release action, the adsorbed oxygen or lattice oxygen of the substance having an oxygen storage / release action migrates. It becomes easy. The “average particle diameter of a substance having an oxygen storage / release action” in the present invention is a particle diameter determined from a crystallite diameter or a transmission electron microscope image obtained from a half-value width of a diffraction peak of the substance in X-ray diffraction. The average value can be measured.

In the present invention, the hydrophilic substance disposed in the anode catalyst layer is not particularly limited as long as it has hydrophilicity, and a known substance can be used. Specifically, hydrophilic metal oxides,
And a carbon material having a high surface area. In the present specification, “hydrophilic” means that the substance (for example, metal oxide) itself has water retention. The “high surface area carbon material” means a carbon material having a large surface area so that sufficient coordination water can be supplied in the vicinity of the catalyst component particles on the support. Preferably, the “high surface area carbon material” is a carbon material having a BET specific surface area of 50 m ² / g or more. More specifically, the hydrophilic metal oxide includes an oxide of at least one metal selected from the group consisting of silicon, titanium, aluminum, zirconium, tantalum, yttrium, tin, tungsten, indium, and antimony. Can be mentioned. Moreover, activated carbon etc. are mentioned as a high surface area carbon material. Of these, hydrophilic materials such as titanium dioxide (TiO ₂ ), silicon dioxide (SiO ₂ ), zirconia (ZrO ₂ ), and high surface area carbon materials such as activated carbon can be used more preferably. Such a substance can supply a sufficient amount of coordination water in the vicinity of the catalyst component particles on the support. Further, the water coordinated by the substance having hydrophilicity can keep the electrolyte (ionomer) contained in the catalyst layer in a high water content state even under low humidification conditions or under high load operation. For this reason, since the proton production reaction of the polymer electrolyte (ionomer) in the vicinity of the catalyst component is accelerated and the proton conductivity is increased, the hydrogen oxidation activity can be improved. The hydrophilic substance may be used alone or in a mixture of two or more. In the present invention, the hydrophilic substance is not complexed with the catalyst component used in the anode catalyst layer, that is, the hydrophilic substance and the catalyst component used in the anode catalyst layer form a complex oxide. do not do. When the hydrophilic substance and the catalyst component are present separately, the catalyst component can function regardless of entering and exiting from the crystal lattice, so that the catalyst component can exhibit a desired effect more effectively.

  In addition, the amount of the hydrophilic substance according to the present invention disposed in the anode catalyst layer is not particularly limited as long as it is an amount that can promote proton generation reaction and improve proton conductivity. Preferably, the content of the hydrophilic substance is 0.01 to 20% by mass with respect to the total amount of the hydrophilic substance catalyst component, the carrier and the polymer electrolyte. Arrange by quantity. The content of the hydrophilic substance is more preferably 0.1 to 15% by mass, still more preferably 0.1 to 10% by mass, based on the total amount of the hydrophilic substance catalyst component, the carrier and the polymer electrolyte. %. Within such a range, in the anode catalyst layer, by simply placing a hydrophilic substance in the vicinity of the catalyst component such as Pt or Pt alloy, sufficient coordination water is provided in the vicinity of the catalyst component particles on the support. The hydrogen oxidation activity can be improved. In addition, water coordinated by a hydrophilic substance can increase proton conductivity of the polymer electrolyte (ionomer) in the vicinity of the catalyst component and improve hydrogen oxidation activity even in a low humidified atmosphere.

  Furthermore, the shape and size of the hydrophilic substance according to the present invention are not particularly limited. It is preferable that the hydrophilic substance has a granular shape. In this case, the average particle diameter of the hydrophilic substance is not particularly limited. Preferably, the average particle size of the hydrophilic substance is 1 μm or less, more preferably 1 to 100 nm, and particularly preferably 5 to 50 nm. Within such a range, the coordinated water and adsorbed water due to the hydrophilic substance carried together with the catalyst component such as Pt or Pt alloy on the support easily move into the ionomer at the three-phase interface. For this reason, the conductivity of protons can be further improved, and the hydrogen oxidation activity can be improved. Further, when the gas diffusion layer (GDL) disposed on the anode catalyst layer side has higher water retention than the gas diffusion layer (GDL) disposed on the cathode catalyst layer side, the inside of the anode catalyst layer is highly humidified. Since it will be in a state, improvement of hydrogen oxidation activity can further be aimed at and it is more preferred. The “average particle diameter of the hydrophilic substance” in the present invention is the average value of the crystallite diameter determined from the half width of the diffraction peak of the substance in X-ray diffraction or the particle diameter determined from a transmission electron microscope image. Can be measured.

In the present invention, the catalyst component used in the cathode catalyst layer is not particularly limited as long as it has a catalytic action for the oxygen reduction reaction, and known catalysts can be used in the same manner. Further, the catalyst component used in the anode catalyst layer is not particularly limited as long as it has a catalytic action for the oxidation reaction of hydrogen, and a known catalyst can be used in the same manner. Specific examples include metals such as platinum, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, and aluminum, and alloys thereof. It is done. Among these, those containing at least platinum are preferably used in order to improve catalyst activity, poisoning resistance to carbon monoxide and the like, heat resistance, and the like. The composition of the alloy varies depending on the type of metal to be alloyed and can be appropriately selected by those skilled in the art. Preferably, the composition of the alloy is preferably 30 to 90 atomic% for platinum and 70 to 10 atomic% for the other metal to be alloyed. In general, an alloy is a generic term for a metal element having one or more metal elements or non-metal elements added and having metallic properties. The alloy structure consists of a eutectic alloy, which is a mixture of the component elements as separate crystals, a component element completely melted into a solid solution, and a component element composed of an intermetallic compound or a compound of a metal and a nonmetal. There is what is formed, and any may be used in the present application. At this time, the catalyst component used for the cathode catalyst layer and the catalyst component used for the anode catalyst layer can be appropriately selected from the above. In the following description, unless otherwise specified, the description of the catalyst component for the cathode catalyst layer and the anode catalyst layer has the same definition for both, and is collectively referred to as “catalyst component”. However, the catalyst components of the cathode catalyst layer and the anode catalyst layer do not need to be the same, and are appropriately selected so as to exhibit the desired action as described above.

  The shape and size of the catalyst component used for the cathode catalyst layer and the anode catalyst layer are not particularly limited, and the same shape and size as those of known catalyst components can be used. However, the catalyst component is preferably granular. The size (average particle diameter) of the catalyst component is preferably 1 to 10 nm, more preferably 1 to 5 nm. Here, when the average particle size of the catalyst component is less than 1 nm, although the surface area of the catalyst component is increased, elution is easily caused by a change in potential, and there is a possibility that performance deterioration with time is large. On the other hand, if the average particle size of the catalyst component exceeds 10 nm, the surface area of the catalyst component becomes too small, and it is difficult to ensure a sufficient three-phase interface, and the power generation performance may be reduced. In particular, when the size (average particle diameter) of the catalyst component is 2 nm, the activity by the catalyst component is high, which is preferable. The sizes (average particle diameters) of the catalyst components of the cathode catalyst layer and the anode catalyst layer may be the same or different, and are appropriately selected so as to achieve the desired action as described above. Is done. The “average particle diameter of the catalyst component” in the present invention is measured by the crystallite diameter obtained from the half-value width of the diffraction peak of the substance in X-ray diffraction or the average value of the particle diameter determined from a transmission electron microscope image. be able to.

  In the present invention, the catalyst component is supported on a carrier to form an electrode catalyst. Here, the carrier is not particularly limited as long as it has conductivity, and a known carrier can be used. As such a conductive carrier, any material may be used as long as it has a specific surface area for supporting the catalyst particles in a desired dispersed state and has sufficient electronic conductivity as a current collector. Carbon is preferred. Specific examples include carbon particles made of carbon black, activated carbon, coke, natural graphite, artificial graphite and the like. In the present invention, “the main component is carbon” refers to containing a carbon atom as a main component, and is a concept including both a carbon atom only and a substantially carbon atom. In some cases, elements other than carbon atoms may be included in order to improve the characteristics of the fuel cell. In addition, being substantially composed of carbon atoms means that mixing of impurities of about 2 to 3% by mass or less is allowed.

The BET specific surface area of the carrier (conductive carrier; hereinafter the same) may be a specific surface area sufficient to support the catalyst component in a highly dispersed state, preferably 20 to 1600 m ² / g, more preferably 80 to It is good to set it as 1200 m < ² > / g. When the specific surface area is in the above range, the dispersibility of the catalyst component and the polymer electrolyte in the conductive support is good, sufficient power generation performance can be achieved, and sufficient catalyst component and polymer electrolyte are effective. Utilization rate can be achieved.

  Further, the size of the conductive carrier is not particularly limited, but from the viewpoint of controlling the ease of loading, the catalyst utilization, and the thickness of the electrode catalyst layer within an appropriate range, the average particle size is 5 to 200 nm. The thickness is preferably about 10 to 100 nm.

  In the electrode catalyst in which the catalyst component is supported on the conductive support, the supported amount of the catalyst component is preferably 10 to 80% by mass, more preferably 30 to 70% by mass with respect to the total amount of the electrode catalyst. Good. If the loading is within the above range, it is preferable because a sufficient degree of dispersion of the catalyst components on the conductive support, improvement in power generation performance, economic advantages, and catalytic activity per unit mass can be achieved. The supported amount of the catalyst component may be the same or different in the cathode catalyst layer and the anode catalyst layer. Further, the amount of the catalyst component supported can be examined by inductively coupled plasma emission spectroscopy (ICP).

  The catalyst component can be supported on the conductive carrier by a known method. For example, known methods such as impregnation method, liquid phase reduction support method, evaporation to dryness method, colloid adsorption method, spray pyrolysis method, reverse micelle (microemulsion method) can be used.

  In the present invention, in the above description, it has been described that only the catalyst component is supported on the conductive support. However, in the cathode catalyst layer, a substance having an oxygen storage / release action may be supported on the conductive support together with the catalyst component. Good. In such a case, the order in which the substance having the oxygen storage / release action and the catalyst component are supported is not particularly limited, and the method of supporting one after the other is supported first; Either is acceptable. Preferably, a method in which a substance having an oxygen storage / release action is first supported on a conductive carrier and then a catalyst component is supported. In this case, the same method as described above can be used as a method for supporting a substance having an oxygen storage / release action on a conductive carrier.

  Similarly, in the anode catalyst layer, a hydrophilic substance may be supported on a conductive carrier together with the catalyst component. In such a case, the order in which the hydrophilic substance and the catalyst component are supported is not particularly limited, and either one of the methods of supporting one of them first and then supporting the other; Good. Preferably, a method of supporting a catalyst component after first supporting a hydrophilic substance on a conductive carrier is preferable. In this case, the same method as described above can be used as the method for supporting the hydrophilic substance on the conductive carrier.

  Alternatively, in the present invention, a commercially available electrode catalyst may be used. As such commercially available products, for example, electrode catalysts such as those manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., N.E. Chemcat, E-TEK, and Johnson Matthey can be used. These electrode catalysts are obtained by supporting platinum or a platinum alloy on a carbon support (supporting concentration of catalyst species, 30 to 70% by mass). In the above, examples of the carbon support include ketjen black, vulcan, acetylene black, black pearl, graphitized carbon support (for example, graphitized ketjen black) previously heat treated at high temperature, carbon nanotube, carbon nanohorn, carbon fiber, etc. There is.

  The cathode catalyst layer of the present invention contains a polymer electrolyte in addition to a substance having an oxygen storage / release action and an electrode catalyst. Similarly, the anode catalyst layer of the present invention contains a polymer electrolyte in addition to the hydrophilic substance and the electrode catalyst. The polymer electrolyte is not particularly limited, and a known one can be used, but any member having at least high proton conductivity may be used. The polymer electrolyte that can be used in this case is roughly classified into a fluorine-based electrolyte that contains fluorine atoms in the whole or a part of the polymer skeleton and a hydrocarbon-based electrolyte that does not contain fluorine atoms in the polymer skeleton.

  Specific examples of the fluorine electrolyte include perfluorocarbon sulfonic acids such as Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), and Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.). Polymer, polytrifluorostyrene sulfonic acid polymer, perfluorocarbon phosphonic acid polymer, trifluorostyrene sulfonic acid polymer, ethylene tetrafluoroethylene-g-styrene sulfonic acid polymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene A preferred example is a fluoride-perfluorocarbon sulfonic acid-based polymer.

  Specific examples of the hydrocarbon electrolyte include polysulfone sulfonic acid, polyaryl ether ketone sulfonic acid, polybenzimidazole alkyl sulfonic acid, polybenzimidazole alkyl phosphonic acid, polystyrene sulfonic acid, polyether ether ketone sulfonic acid, polyphenyl. A suitable example is sulfonic acid.

  The polymer electrolyte preferably contains a fluorine atom because it is excellent in heat resistance, chemical stability, and the like. Among these, fluorine electrolytes such as Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.) and the like are preferable. In particular, in the present invention, when a polymer electrolyte having a sulfonic acid group such as Nafion (registered trademark, manufactured by DuPont) is used, it is preferable to use one having an EW of about 600 to 1100. In addition, EW (Equivalent Weight) represents the dry film weight per 1 mol of sulfonic acid groups, and means that the specific gravity of sulfonic acid groups is larger as it is smaller.

Further, the amount of the polymer electrolyte is not particularly limited. The ratio (Ionomer / Carbon; I / C) of the polymer electrolyte mass (I) to the conductive carrier mass (C) is 0.5 to 2.0, more preferably 0.7 to 1.6. It is preferable that the amount is small. In such a range, sufficient proton conductivity and gas diffusivity can be achieved. The above I / C ratio is determined by measuring the conductive carrier mass and the electrolyte solid content contained in the catalyst layer to be mixed in advance when preparing the catalyst ink (slurry) described in detail below. It can be calculated and controlled by adjusting the ratio. In addition, the mass (C) of the conductive support when the electrode catalyst layer is analyzed to determine the I / C is obtained by subtracting the mass of the catalyst component from the mass of the electrode catalyst. The mass of the catalyst component can be quantified by inductively coupled plasma emission spectroscopy (ICP). The polymer electrolyte mass (I) in the catalyst layer when the electrode catalyst layer is analyzed to determine the I / C is determined by the structure analysis of the polymer electrolyte by ¹⁹ F NMR and the determination of S atoms by coulometric titration. It is possible to quantify by combining the two.

  In the present invention, the cathode catalyst layer can be produced by a method such as a transfer method using a material having an oxygen storage / release action, a carrier (electrode catalyst) carrying a catalyst component, a polymer electrolyte and a solvent. Alternatively, the cathode catalyst layer can be produced by a method such as a transfer method using a carrier ink carrying a substance having an oxygen storage / release action and a catalyst component, a polymer electrolyte, and a solvent. Similarly, the anode catalyst layer can be produced by a method such as a transfer method using a hydrophilic substance, a carrier (electrode catalyst) carrying a catalyst component, a polymer electrolyte and a solvent. Alternatively, the anode catalyst layer can be produced by a method such as a transfer method using a catalyst ink comprising a carrier having a hydrophilic substance and a catalyst component supported thereon, a polymer electrolyte, and a solvent.

  The production method of the electrode catalyst layer in such a case is not particularly limited, and a known transfer method can be used in the same manner or with appropriate modification. For example, the following method can be used. That is, a catalyst ink for forming a cathode catalyst layer and an anode catalyst layer is prepared. Next, each catalyst ink is applied and dried on a transfer mount to form each catalyst layer.

  At this time, as the transfer mount, a known sheet such as a polyester sheet such as a PTFE (polytetrafluoroethylene) sheet or a PET (polyethylene terephthalate) sheet can be used. The transfer mount is appropriately selected according to the type of catalyst ink to be used (particularly, a conductive carrier such as carbon in the ink).

  Moreover, it does not restrict | limit especially as a solvent, The normal solvent used for forming an electrode catalyst layer can be used similarly. Specifically, lower alcohols such as water, cyclohexanol, ethanol, n-propyl alcohol, and 2-propyl alcohol can be used.

  Further, the amount of the solvent used is not particularly limited, and a known amount can be used. For example, in the cathode catalyst layer, the carrier on which the catalyst component is supported is not particularly limited as long as it has an amount capable of sufficiently exhibiting a desired action, that is, an action of catalyzing an oxygen reduction reaction. Preferably, the carrier on which the catalyst component is supported is preferably present in the catalyst ink in an amount of 5 to 30% by mass, more preferably 9 to 20% by mass. Further, the amount of the substance having an oxygen storage / release action is not particularly limited as long as the content in the catalyst layer is as described above.

  Similarly, in the anode catalyst layer, the support on which the catalyst component is supported is not particularly limited as long as it has an amount capable of sufficiently exhibiting a desired action, that is, an action for catalyzing an oxidation reaction of hydrogen. Preferably, the carrier on which the catalyst component is supported is preferably present in the catalyst ink in an amount of 5 to 30% by mass, more preferably 9 to 20% by mass. Further, the amount of the hydrophilic substance is not particularly limited as long as the content in the catalyst layer is as described above.

  The catalyst ink according to the present invention may contain a thickener. The use of a thickener is effective when the catalyst ink cannot be successfully applied onto a transfer mount. The thickener that can be used in this case is not particularly limited, and a known thickener can be used. For example, glycerin, ethylene glycol (EG), polyvinyl alcohol (PVA), propylene glycol (PG) and the like can be mentioned. Of these, propylene glycol (PG) is preferably used. The use of propylene glycol (PG) increases the boiling point of the catalyst ink and decreases the solvent evaporation rate. For example, when an electrode catalyst layer is formed on an electrolyte membrane by a transfer method, a catalyst ink is first applied onto a transfer mount different from the membrane using a screen printer and dried. At this time, by adding PG to the catalyst ink, the solvent evaporation rate in the applied catalyst ink can be suppressed, and the electrode catalyst layer after the drying process can be suppressed / prevented from cracking. Further, the amount of the thickener added when using the thickener is not particularly limited as long as it does not interfere with the above-described effects of the present invention, but is preferably 5 with respect to the total mass of the catalyst ink. ˜20 mass%.

  The catalyst ink according to the present invention may contain a water repellent polymer. The use of the water-repellent polymer is effective when the catalyst ink cannot be applied well onto the transfer mount. The water-repellent polymer that can be used in this case is not particularly limited, and a known water-repellent polymer can be used. Examples include fluorine-based polymer materials such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoropropylene, and tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polypropylene, and polyethylene. It is done. In addition, the amount of the water-repellent polymer added when the water-repellent polymer is used is not particularly limited as long as it is an amount that does not interfere with the above-described effect of the present invention. Is 0.1 to 20% by mass.

The catalyst ink for cathode catalyst according to the present invention is a mixture of a substance having an oxygen storage / release action, an electrode catalyst, a polymer electrolyte and a solvent, and, if necessary, a water-repellent polymer and / or a thickener. If so, the preparation method is not particularly limited. Similarly, the catalyst ink for an anode catalyst according to the present invention is appropriately mixed with a hydrophilic substance, an electrode catalyst, a polymer electrolyte and a solvent, and if necessary, a water-repellent polymer and / or a thickener. If it is a thing, the preparation method in particular is not restrict | limited. In addition, the catalyst ink is obtained by dispersing the slurry mixed as described above with an ultrasonic homogenizer, or after thoroughly pulverizing the mixed slurry with an apparatus such as a sand grinder, a circulating ball mill, or a circulating bead mill. It is preferable to prepare by adding a vacuum degassing operation.

  In the present invention, the electrode catalyst layer is preferably such that the average thickness (Ya) of the anode catalyst layer is smaller than the average thickness (Yc) of the cathode catalyst layer. As described above, in the present invention, the moisture retention in the catalyst layer can be improved. For this reason, even if the anode catalyst layer is thinned (the coating amount is reduced), the hydrogen oxidation activity can be improved. Further, the durability of the cathode catalyst layer can be improved. More specifically, Ya and Yc preferably satisfy the relationship of Ya / Yc = 0.1 to 0.6. By controlling the thickness of the catalyst layer in such a relationship, the above effect can be effectively achieved.

  In the present invention, the average thickness (Ya) of the anode catalyst layer is preferably 0.5 to 20 μm, more preferably 1 to 15 μm. Moreover, the average thickness (Yc) of the cathode catalyst layer is preferably 1 to 40 μm, more preferably 5 to 20 μm. By setting it within this range, the catalytic action of hydrogen oxidation reaction (anode side) and oxygen reduction reaction (cathode side) can be sufficiently exhibited.

  The method for applying the catalyst ink onto the transfer mount is not particularly limited, and a known method such as a screen printing method, a deposition method, or a spray method can be similarly applied.

  In the above method, the drying conditions of the applied cathode / anode catalyst layer are not particularly limited as long as the solvent can be completely removed from each catalyst layer. Specifically, the coating layer (catalyst layer) of the catalyst ink is dried in a vacuum dryer at room temperature to 100 ° C., more preferably 50 to 80 ° C., for 1 to 50 hours. At this time, if the thickness of the catalyst layer is not sufficient, the coating and drying process is repeated until a desired thickness is obtained. Next, after sandwiching the polymer electrolyte membrane between the electrode catalyst layers according to the present invention laminated in this manner, hot pressing is performed on the laminate. At this time, the hot press conditions are not particularly limited as long as the electrode catalyst layer and the polymer electrolyte membrane can be sufficiently closely bonded, but are 100 to 200 ° C., more preferably 110 to 170 ° C. It is preferable to carry out at a press pressure of 1 to 5 MPa. Thereby, the bondability between the polymer electrolyte membrane and the electrode catalyst layer can be enhanced. After performing the hot press, the transfer mount is peeled off to obtain a cathode catalyst layer-electrolyte membrane-anode catalyst layer laminate (CCM).

  In the above description, the method for producing the CCM by applying the catalyst ink by the transfer method has been described. However, the CCM has the above-described cathode catalyst catalyst ink or anode catalyst catalyst ink on the electrolyte membrane surface. A method of forming a catalyst layer on the electrolyte membrane by directly applying and then applying and drying may be used. In this case, the conditions for forming the electrode catalyst layer on the electrolyte membrane are not particularly limited, and can be used in the same manner as known methods or with appropriate modifications. For example, the catalyst ink is applied onto the electrolyte membrane so that the thickness after drying is as described above, and is 25 to 150 ° C., more preferably 60 to 120 ° C. in a vacuum dryer or under reduced pressure. And drying for 5 to 30 minutes, more preferably for 10 to 20 minutes. In addition, in the said process, when the thickness of an electrode catalyst layer is not enough, the said application | coating and drying process is repeated until it becomes desired thickness.

The electrolyte membrane used for the CCM is not particularly limited, and examples thereof include a membrane made of the same polymer electrolyte as that used for the electrode catalyst layer. In addition, perfluorosulfonic acid membranes represented by Nafion (registered trademark, manufactured by DuPont) and Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.), ion exchange resins manufactured by Dow Chemical Company, and ethylene-tetrafluoroethylene copolymer Fluoropolymer electrolytes such as resin membranes, resin membranes based on trifluorostyrene, and hydrocarbon polymer resin membranes with sulfonic acid groups, such as polymer electrolyte membranes that are generally commercially available, A membrane obtained by impregnating a microporous membrane with a liquid electrolyte, a membrane obtained by filling a porous body with a polymer electrolyte, or the like may be used. The polymer electrolyte used for the electrolyte membrane and the polymer electrolyte used for each electrode catalyst layer may be the same or different, but improve the adhesion between each electrode catalyst layer and the electrolyte membrane. From the viewpoint, it is preferable to use the same one.

  The thickness of the electrolyte membrane may be appropriately determined in consideration of the characteristics of the obtained CCM, but is preferably 5 to 300 μm, more preferably 10 to 200 μm, and particularly preferably 15 to 100 μm. From the viewpoint of strength during film formation and durability during MEA operation, it is preferably 5 μm or more, and from the viewpoint of output characteristics during MEA operation, it is preferably 300 μm or less.

  Further, as the electrolyte membrane, in addition to the above-described fluorine-based polymer electrolyte and a membrane made of a hydrocarbon resin having a sulfonic acid group, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc. You may use what formed the porous thin film impregnated with electrolyte components, such as phosphoric acid and an ionic liquid.

  In addition to the CCM, the MEA of the present invention further includes a gas diffusion layer as described in detail below. At this time, it is preferable that the gas diffusion layer is further bonded to each electrode catalyst layer in the above method by peeling off the transfer mount or sandwiching the bonded body prepared above with the gas diffusion layer. Alternatively, an electrode catalyst layer is previously formed on the surface of the gas diffusion layer to produce an electrode catalyst layer-gas diffusion layer assembly, and then the electrode catalyst layer-gas diffusion layer assembly is used as an electrolyte in the same manner as described above. It is also preferable to sandwich and bond the films by hot pressing.

  At this time, the gas diffusion layer (GDL) used in the MEA is not particularly limited, and a known one can be used in the same manner. For example, conductive and porous materials such as carbon woven fabric, paper-like paper body, felt, and non-woven fabric can be used. The thing which uses the sheet-like material which has quality as a base material etc. are mentioned. The thickness of the substrate may be appropriately determined in consideration of the characteristics of the obtained gas diffusion layer, but may be about 30 to 500 μm. If the thickness is less than 30 μm, sufficient mechanical strength or the like may not be obtained, and if it exceeds 500 μm, the distance through which gas or water permeates is undesirably increased.

  In the present invention, the gas diffusion layer on the anode side has at least one characteristic selected from the group consisting of low gas permeability, low water permeability, high water retention, and high moisture retention than the cathode side gas diffusion layer. It is preferable to have. Thereby, since the moisture retention in the catalyst layer is improved, the hydrogen oxidation activity / oxygen reduction activity can be improved even under low humidification conditions. In addition, the said characteristic can be adjusted by selecting suitably the kind of water repellent described below, the mixing ratio of a carbon particle and a water repellent.

  The method for forming the electrode catalyst layer on the surface of the gas diffusion layer is not particularly limited, and known methods such as a screen printing method, a deposition method, and a spray method can be similarly applied. In addition, the conditions for forming the electrode catalyst layer on the surface of the gas diffusion layer are not particularly limited, and the same conditions as before can be applied by the specific forming method as described above.

The gas diffusion layer preferably contains a water repellent in the base material for the purpose of further improving water repellency and preventing a flooding phenomenon. The water repellent is not particularly limited, but polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF),
Examples thereof include fluorine-based polymer materials such as polyhexafluoropropylene and tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polypropylene, and polyethylene.

  Moreover, in order to improve water repellency more, the said gas diffusion layer may have a carbon particle layer which consists of an aggregate | assembly of the carbon particle containing a water repellent on the said base material.

  The carbon particles are not particularly limited, and may be conventional ones such as carbon black, graphite, and expanded graphite. Of these, carbon blacks such as oil furnace black, channel black, lamp black, thermal black, and acetylene black are preferred because of their excellent electron conductivity and large specific surface area. The particle size of the carbon particles is preferably about 10 to 100 nm. Thereby, while being able to obtain the high drainage property by capillary force, it becomes possible to improve contact property with a catalyst layer.

  Examples of the water repellent used for the carbon particle layer include the same water repellents as those described above used for the substrate. Of these, fluorine-based polymer materials are preferably used because of their excellent water repellency and corrosion resistance during electrode reaction.

  In the carbon particle layer, the mixing ratio of the carbon particles to the water repellent may be insufficient to obtain water repellency as expected when there are too many carbon particles. If there are too many water repellents, sufficient electron conductivity may be obtained. There is a risk that it will not be obtained. Considering these, the mixing ratio of the carbon particles and the water repellent in the carbon particle layer is preferably about 90:10 to 40:60 in terms of mass ratio.

  The thickness of the carbon particle layer may be appropriately determined in consideration of the water repellency of the obtained gas diffusion layer.

  When a water repellent is contained in the gas diffusion layer, a general water repellent treatment method may be used. For example, after immersing the base material used for a gas diffusion layer in the dispersion liquid of a water repellent agent, the method of heat-drying with oven etc. is mentioned.

  When a carbon particle layer is formed on a substrate in the gas diffusion layer, a slurry is prepared by dispersing carbon particles, a water repellent, and the like in a solvent. Next, the slurry may be applied on a substrate and dried, or the slurry may be dried once and pulverized to form a powder, which may be applied onto the gas diffusion layer. Then, it is preferable to heat-process at about 250-400 degreeC using a muffle furnace or a baking furnace. In the above method, the solvent used for preparing the slurry is not particularly limited. For example, water, perfluorobenzene, dichloropentafluoropropane, alcohol solvents such as methanol and ethanol can be preferably used.

  In addition, the manufacturing method of the joined body including the electrode catalyst layer, the electrolyte membrane, and preferably the gas diffusion layer is not limited to the method described above. That is, a method in which a catalyst ink is applied and dried on an electrolyte membrane, followed by hot pressing, the electrode catalyst layer is joined to the electrolyte membrane, and the obtained joined body is sandwiched between gas diffusion layers to form MEA; Ink may be applied to the gas diffusion layer and dried to form an electrode catalyst layer, which may be joined to the electrolyte membrane by hot pressing, or any other known technique may be used as appropriate.

As described above, in the MEA of the present invention, a substance having an oxygen storage / release action is disposed in the cathode catalyst layer. Thereby, promotion of oxygen reduction reaction and suppression of platinum dissolution can be achieved. Further, a hydrophilic substance is disposed in the anode catalyst layer. Thereby, the proton production reaction can be promoted and the conductivity of the proton can be improved. Therefore, the electrolyte membrane-electrode assembly (MEA) using the cathode catalyst layer and / or the anode catalyst layer according to the present invention is excellent in power generation performance and durability.

  Therefore, by using the MEA of the present invention, it is possible to provide a highly reliable fuel cell that is excellent in power generation performance and durability. Therefore, the present invention also provides a fuel cell using the electrolyte membrane-electrode assembly of the present invention.

  The type of the fuel cell is not particularly limited. In the above description, the polymer electrolyte fuel cell has been described as an example. In addition, an alkaline fuel cell, a direct methanol fuel cell, a micro cell, and the like are used. Examples include a fuel cell. Among them, a polymer electrolyte fuel cell (PEFC) is preferable because it is small in size and can achieve high density and high output. The fuel cell is useful as a stationary power source in addition to a power source for a moving body such as a vehicle in which a mounting space is limited. However, the fuel cell is particularly useful for an automobile application in which system start / stop and output fluctuation frequently occur. It can be particularly preferably used.

  The application of the fuel cell is not particularly limited, but it is preferably applied to a vehicle. The electrolyte membrane-electrode assembly of the present invention is excellent in power generation performance and durability, and can be downsized. For this reason, the fuel cell of this invention is especially advantageous when this fuel cell is applied to a vehicle from the point of in-vehicle property.

  In particular, the polymer electrolyte fuel cell is useful as a power source for a mobile body such as an automobile in which a mounting space is limited in addition to a stationary power source. In particular, it is particularly preferable to be used as a power source for a mobile body such as an automobile in which corrosion of a carbon support or a catalytic metal (such as Pt) is likely to occur due to a high output voltage required after a relatively long shutdown.

  The configuration of the fuel cell is not particularly limited, and a conventionally known technique may be used as appropriate. Generally, the fuel cell has a structure in which an MEA is sandwiched between separators.

  The separator can be used without limitation as long as it is conventionally known, such as those made of carbon such as dense carbon graphite and a carbon plate, and those made of metal such as stainless steel. The separator has a function of separating air and fuel gas, and a channel groove for securing the channel may be formed. The thickness and size of the separator, the shape of the flow channel, and the like are not particularly limited, and may be appropriately determined in consideration of the output characteristics of the obtained fuel cell.

  Further, in order to prevent the gas supplied to each catalyst layer from leaking to the outside, a gas seal portion may be further provided at a portion where the catalyst layer is not formed on the gasket layer. Examples of the material constituting the gas seal portion include rubber materials such as fluoro rubber, silicon rubber, ethylene propylene rubber (EPDM), polyisobutylene rubber, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoro. Fluorine polymer materials such as propylene, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and thermoplastic resins such as polyolefin and polyester. The thickness of the gas seal portion may be 2 mm to 50 μm, preferably about 1 mm to 100 μm.

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

  The effects of the present invention will be described using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples.

Example 1
1. Preparation of anode catalyst layer Pt was supported on carbon black (Ketjen Black EC, manufactured by Ketjen Black International Co., Ltd., BET surface area = 800 m ² / g) as a conductive carbon material to obtain an electrode catalyst. The electrode catalyst had an average particle diameter of Pt particles of 2.6 nm and a Pt support concentration of 50% by mass. Five times the amount of purified water was added to 10 g of this electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 4.3 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.2 / 1.0.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by screen printing in two portions according to the desired thickness and dried at 60 ° C. for 24 hours. The size of the formed anode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the amount of Pt was 0.2 mg / cm ² (the average thickness of the anode catalyst layer was 7 μm). Thus, an anode catalyst layer coated sheet A1 was obtained.

2. Preparation of Cathode Catalyst Layer Pt was supported on carbon black (Ketjen Black EC, manufactured by Ketjen Black International, BET surface area = 800 m ² / g) as a conductive carbon material. Thereafter, the carbon black supporting Pt was treated at 700 ° C. for 2 hours in a gas flow atmosphere of 10% volume hydrogen-90% volume nitrogen to obtain an electrode catalyst (average particle diameter of Pt particles: 3.2 nm, Pt supported concentration: 50). Mass%). 5 g of purified water was added to 10 g of the electrode catalyst thus obtained, and a vacuum degassing operation was added for 5 minutes. To this, 4.3 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.2 / 1.0. Next, 0.01 g of cerium oxide (CeO ₂ , average particle size 50 nm) was added to the above mixture to prepare a mixed slurry.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by screen printing in four portions in an amount corresponding to the desired thickness, and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. The coating layer on the polytetrafluoroethylene sheet was adjusted so that the amount of Pt was 0.4 mg / cm ² (the average thickness of the cathode catalyst layer was 15 μm). Thus, a cathode catalyst layer coated sheet B1 was obtained. Preparation of Electrolyte Membrane Electrode Assembly (MEA) Nafion NRE211 (film thickness 25 μm) as a solid polymer electrolyte membrane and an electrode catalyst layer formed on the previously prepared polytetrafluoroethylene sheet (anode catalyst layer coated on the anode side) The cathode catalyst layer coated sheet B1) was superposed on the sheet A1 and the cathode side. At that time, the anode catalyst layer, the solid polymer electrolyte membrane, and the cathode catalyst layer were laminated in this order. Thereafter, hot pressing was performed at 130 ° C. and 2.0 MPa for 10 minutes, and only the polytetrafluoroethylene sheet was peeled off to obtain a membrane electrode assembly (MEA) M1.

In this membrane electrode assembly M1, the electrode area of the cathode catalyst layer is 25 cm ² , the amount of Pt supported is 0.4 mg per 1 cm ^{2 of the} apparent electrode area, the electrode area of the anode catalyst layer is 25 cm ² , and the amount of Pt supported is apparent The electrode area was 0.2 mg per 1 cm ² .

4). MEA Performance Evaluation The performance of the obtained membrane / electrode assembly M1 was evaluated as follows.

  On both sides of the electrolyte membrane-electrode assembly M1, commercially available carbon paper with a mill layer as a gas diffusion layer (24BC manufactured by SGL Carbon Co., Ltd., cut into a size of 6.0 cm × 5.5 cm, carbon paper thickness of 200 μm), A gas separator with a gas flow path was disposed, and was further sandwiched between gold-plated stainless steel current collector plates to form evaluation unit cells.

In the evaluation unit cell, hydrogen was supplied as a fuel to the anode side, and air was supplied as an oxidant to the cathode side. The supply pressure of both gases was atmospheric pressure, hydrogen was set to 58.6 ° C. and relative humidity 60%, air was set to 54.8 ° C. and relative humidity 50%, and the cell temperature was set to 70 ° C. The hydrogen utilization rate was 67% and the air utilization rate was 40%. Under this condition, the cell voltage when power was generated at a current density of 1.0 A / cm ² was measured as the initial cell voltage.

  Table 1 shows the compositions of the anode and cathode catalyst layers of this example and the results of the performance test. In Table 1 below, “a substance having an oxygen storage / release action” is expressed as “oxygen storage / release material”, and “a hydrophilic substance” is expressed as “hydrophilic material”, respectively.

Examples 2-8
1. Preparation of anode catalyst layer Example 1 In Example 1, except that the composition shown in Table 1 was used. In the same manner as above, anode catalyst layers (anode catalyst layer coated sheets A2 to 8) were produced.

2. Production of cathode catalyst layer Example 1 In Example 1, except that the composition shown in Table 1 was used. In the same manner, cathode catalyst layers (cathode catalyst layer coated sheets B2 to 8) were produced.

3. Production of electrolyte membrane electrode assembly (MEA) 1. Anode catalyst layer-coated sheets A2 to 8 prepared in 2 above and 2. Example 1 except that the cathode catalyst layer-coated sheets B2 to 8 prepared in 1 were used instead. In the same manner, electrode assemblies (MEA) M2 to 8 were obtained.

4). 3. MEA performance evaluation The performance of the obtained membrane electrode assembly M2-8 was determined by referring to Example 1 described above. And evaluated in the same manner.

  Table 1 shows the compositions of the anode and cathode catalyst layers of this example and the results of the performance test.

Example 9
1. Preparation of anode catalyst layer Example 3 In the same manner as above, an anode catalyst layer-coated sheet A9 was obtained.

2. Preparation of Cathode Catalyst Layer Pt was supported on carbon black (Ketjen Black EC, manufactured by Ketjen Black International Co., Ltd., BET surface area = 800 m ² / g) as a conductive carbon material to obtain an electrode catalyst. The electrode catalyst had an average particle diameter of Pt particles of 2.6 nm and a Pt support concentration of 50% by mass. Five times the amount of purified water was added to 10 g of this electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 4.3 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.2 / 1.0. Next, 6.0 g of cerium oxide was added to the mixed slurry in the same manner as in Example 1.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by a screen printing method in an amount corresponding to the desired thickness in five portions and dried at 60 ° C. for 24 hours. The size of the formed anode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the amount of Pt was 0.4 mg / cm ² . Thus, a cathode catalyst layer coated sheet B9 was obtained.

3. Production of electrolyte membrane electrode assembly (MEA) 1. The anode catalyst layer coated sheet A9 produced in 1 above and 2. Example 1 above, except that the cathode catalyst layer coated sheet B9 prepared in 1 was used instead. In the same manner, an electrode assembly (MEA) M9 was obtained.

In this membrane electrode assembly M9, the electrode area of the cathode catalyst layer is 25 cm ² , the amount of Pt supported is 0.4 mg per 1 cm ^{2 of the} apparent electrode area, the electrode area of the anode catalyst layer is 25 cm ² , and the amount of Pt supported is apparent The electrode area was 0.2 mg per 1 cm ² .

4). 3. MEA Performance Evaluation The performance of the obtained membrane electrode assembly M9 was evaluated as in Example 1 above. And evaluated in the same manner.

  Table 1 shows the compositions of the anode and cathode catalyst layers of this example and the results of the performance test.

Example 10
1. Preparation of anode catalyst layer Pt was supported on carbon black (Ketjen Black EC, manufactured by Ketjen Black International Co., Ltd., BET surface area = 800 m ² / g) as a conductive carbon material to obtain an electrode catalyst. The electrode catalyst had an average particle diameter of Pt particles of 2.6 nm and a Pt support concentration of 50% by mass. Five times the amount of purified water was added to 10 g of this electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 4.3 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.2 / 1.0. Next, 0.1 g of silica sol (solid content 10%, SiO ₂ average particle size 30 nm) was added to the mixed slurry.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by a screen printing method in three times according to the desired thickness, and dried at 60 ° C. for 24 hours. The size of the formed anode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the amount of Pt was 0.2 mg / cm ² (the average thickness of the anode catalyst layer was 7 μm). Thus, an anode catalyst layer coated sheet A10 was obtained.

2. Preparation of Cathode Catalyst Layer Pt was supported on carbon black (Ketjen Black EC, manufactured by Ketjen Black International Co., Ltd., BET surface area = 800 m ² / g) as a conductive carbon material to obtain an electrode catalyst. The electrode catalyst had an average particle diameter of Pt particles of 2.6 nm and a Pt support concentration of 50% by mass. Five times the amount of purified water was added to 10 g of this electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 4.3 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the electrode catalyst was Ionomer / Carbon = 1.2 / 1.0 (I / C ratio).

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by a screen printing method in an amount corresponding to the desired thickness in five portions and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. The coating layer on the polytetrafluoroethylene sheet was adjusted so that the amount of Pt was 0.4 mg / cm ² (the average thickness of the cathode catalyst layer was 16 μm). Thus, a cathode catalyst layer coated sheet B10 was obtained.

3. Preparation of Electrolyte Membrane Electrode Assembly (MEA) Nafion NRE211 (film thickness 25 μm) as a solid polymer electrolyte membrane and an electrode catalyst layer formed on the previously prepared polytetrafluoroethylene sheet (anode catalyst layer coated on the anode side) The cathode catalyst layer coated sheet B10) was superposed on the sheet A10 and the cathode side. At that time, the anode catalyst layer, the solid polymer electrolyte membrane, and the cathode catalyst layer were laminated in this order. Thereafter, hot pressing was performed at 130 ° C. and 2.0 MPa for 10 minutes, and only the polytetrafluoroethylene sheet was peeled off to obtain a membrane electrode assembly (MEA) M10.

In this membrane electrode assembly M10, the electrode area of the cathode catalyst layer is 25 cm ² , the amount of Pt supported is 0.4 mg per 1 cm ^{2 of the} apparent electrode area, the electrode area of the anode catalyst layer is 25 cm ² , and the amount of Pt supported is apparent The electrode area was 0.2 mg per 1 cm ² .

4). MEA Performance Evaluation The performance of the obtained membrane / electrode assembly M10 was evaluated in Example 1 4. And evaluated in the same manner.

  Table 1 shows the compositions of the anode and cathode catalyst layers of this example and the results of the performance test.

Examples 11-17
1. Preparation of anode catalyst layer Example 10 In Example 10, except that the composition shown in Table 1 was used. In the same manner as above, anode catalyst layers (anode catalyst layer-coated sheets A11 to A-17) were produced.

2. Preparation of cathode catalyst layer Example 10 In Example 10, except that the composition shown in Table 1 was used. In the same manner, cathode catalyst layers (cathode catalyst layer coated sheets B11 to 17) were produced. In Examples 15 to 17, the activated carbon had a BET surface area of 3000 m ² / g.

3. Production of electrolyte membrane electrode assembly (MEA) 1. Anode catalyst layer coated sheets A11-17 prepared in 1 above and 2. Example 10 except that the cathode catalyst layer-coated sheets B11 to B-17 prepared in the above were used instead. In the same manner, electrode assemblies (MEA) M11 to 17 were obtained.

4). 3. MEA Performance Evaluation The power generation performance of the obtained membrane electrode assemblies M11 to M17 is shown in Example 1 above. And evaluated in the same manner.

  Table 1 shows the compositions of the anode and cathode catalyst layers of this example and the results of the performance test.

Example 18
1. Preparation of anode catalyst layer Pt was supported on carbon black (Ketjen Black EC, manufactured by Ketjen Black International Co., Ltd., BET surface area = 800 m ² / g) as a conductive carbon material to obtain an electrode catalyst. The electrode catalyst had an average particle diameter of Pt particles of 2.6 nm and a Pt support concentration of 50% by mass. Five times the amount of purified water was added to 10 g of this electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 4.3 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the electrode catalyst was Ionomer / Carbon = 1.2 / 1.0 (I / C ratio). Next, 6.0 g of activated carbon was added to the mixed slurry. In this example, the activated carbon had a BET surface area of 3000 m ² / g.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by a screen printing method in an amount corresponding to the desired thickness in 6 portions and dried at 60 ° C. for 24 hours. The size of the formed anode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the amount of Pt was 0.2 mg / cm ² (the average thickness of the anode catalyst layer was 9 μm). Thus, an anode catalyst layer coated sheet A18 was obtained.

2. Preparation of cathode catalyst layer Example 12 In the same manner as above, a cathode catalyst layer-coated sheet B18 was obtained.

3. Preparation of Electrolyte Membrane Electrode Assembly (MEA) Nafion NRE211 (film thickness 25 μm) as a solid polymer electrolyte membrane and an electrode catalyst layer formed on the previously prepared polytetrafluoroethylene sheet (anode catalyst layer coated on the anode side) Sheet A18 and a cathode catalyst layer coated sheet B18) were superposed on the cathode side. At that time, the anode catalyst layer, the solid polymer electrolyte membrane, and the cathode catalyst layer were laminated in this order. Thereafter, hot pressing was performed at 130 ° C. and 2.0 MPa for 10 minutes, and only the polytetrafluoroethylene sheet was peeled off to obtain a membrane electrode assembly (MEA) M18.

In this membrane electrode assembly M18, the electrode area of the cathode catalyst layer is 25 cm ² , the amount of Pt supported is 0.4 mg per 1 cm ^{2 of the} apparent electrode area, the electrode area of the anode catalyst layer is 25 cm ² , and the amount of Pt supported is apparent The electrode area was 0.2 mg per 1 cm ² .

4). 3. MEA Performance Evaluation The performance of the obtained membrane electrode assembly M18 was evaluated in the same manner as in Example 1 4. And evaluated in the same manner.

  Table 1 shows the compositions of the anode and cathode catalyst layers of this example and the results of the performance test.

Example 19
1. Preparation of anode catalyst layer Pt was supported on carbon black (Ketjen Black EC, manufactured by Ketjen Black International Co., Ltd., BET surface area = 800 m ² / g) as a conductive carbon material. Thereafter, the carbon black supporting Pt was treated at 700 ° C. for 2 hours in a gas flow atmosphere of 10% volume hydrogen-90% volume nitrogen to obtain an electrode catalyst (average particle diameter of Pt particles 3.2 nm, Pt supported concentration). 50% by mass) was obtained. 5 g of purified water was added to 10 g of the electrode catalyst thus obtained, and a vacuum degassing operation was added for 5 minutes. To this, 4.3 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.2 / 1.0. Next, 1.5 g of activated carbon (BET surface area of 3000 m ² / g) was added to the mixed slurry.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by a screen printing method in an amount corresponding to the desired thickness in five portions and dried at 60 ° C. for 24 hours. The size of the formed anode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the amount of Pt was 0.2 mg / cm ² (the average thickness of the anode catalyst layer was 10 μm). Thus, an anode catalyst layer coated sheet A19 was obtained.

2. Preparation of Cathode Catalyst Layer Pt was supported on carbon black (DENKA acetylene black, BET surface area = 850 m ² / g) as a conductive carbon material. Thereafter, the carbon black supporting Pt was treated at 700 ° C. for 2 hours under a gas flow atmosphere of 10% volume hydrogen-90% volume nitrogen to obtain an electrode catalyst (average particle diameter of Pt particles 3.6 nm, Pt supported concentration). 50% by mass) was obtained. 5 g of purified water was added to 10 g of the electrode catalyst thus obtained, and a vacuum degassing operation was added for 5 minutes. To this, 4.3 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.2 / 1.0. Next, 0.5 g of cerium-containing zirconium oxide (Ce _0.2 Zr _0.8 O _Y1 , average particle size 50 nm) was added to the mixed slurry.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by a screen printing method in an amount corresponding to the desired thickness in 6 portions and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. The coating layer on the polytetrafluoroethylene sheet was adjusted so that the amount of Pt was 0.4 mg / cm ² (the average thickness of the cathode catalyst layer was 17 μm). Thus, a cathode catalyst layer coated sheet B19 was obtained.

3. Preparation of Electrolyte Membrane Electrode Assembly (MEA) Nafion NRE211 (film thickness 25 μm) as a solid polymer electrolyte membrane and an electrode catalyst layer formed on the previously prepared polytetrafluoroethylene sheet (anode catalyst layer coated on the anode side) The cathode catalyst layer coated sheet B19) was superposed on the sheet A19 and the cathode side. At that time, the anode catalyst layer, the solid polymer electrolyte membrane, and the cathode catalyst layer were laminated in this order. Thereafter, hot pressing was performed at 130 ° C. and 2.0 MPa for 10 minutes, and only the polytetrafluoroethylene sheet was peeled off to obtain a membrane electrode assembly (MEA) M19.

In this membrane electrode assembly M19, the electrode area of the cathode catalyst layer is 25 cm ² , the amount of Pt supported is 0.4 mg per 1 cm ^{2 of the} apparent electrode area, the electrode area of the anode catalyst layer is 25 cm ² , and the amount of Pt supported is apparent The electrode area was 0.2 mg per 1 cm ² .

4). MEA Performance Evaluation The performance of the membrane electrode assembly M19 thus obtained was evaluated in Example 1 above. And evaluated in the same manner.

  Table 1 shows the compositions of the anode and cathode catalyst layers of this example and the results of the performance test.

Examples 20-26
1. Preparation of anode catalyst layer Example 19 In Example 19, except that the composition shown in Table 1 was used. In the same manner as above, anode catalyst layers (anode catalyst layer coated sheets A20 to A26) were produced.

2. Preparation of cathode catalyst layer Example 19 In Example 19, except that the composition shown in Table 1 was used. In the same manner as above, cathode catalyst layers (cathode catalyst layer coated sheets B20 to B26) were produced.

3. Production of electrolyte membrane electrode assembly (MEA) 1. Anode catalyst layer coated sheets A20 to A26 prepared in 2 above and 2. Example 19 except that the cathode catalyst layer-coated sheets B20 to B26 prepared in 1 were used instead. In the same manner, electrode assemblies (MEA) M20 to M26 were obtained.

4). 3. MEA Performance Evaluation The power generation performance of the obtained membrane electrode assemblies M20 to M26 was determined as in Example 1 above. And evaluated in the same manner.

  Table 1 shows the compositions of the anode and cathode catalyst layers of this example and the results of the performance test.

Example 27
1. Preparation of anode catalyst layer Example 1 In the same manner as described above, an anode catalyst layer (anode catalyst layer-coated sheet A27) was produced.

2. Preparation of Cathode Catalyst Layer Carbon black (Ketjen Black EC, manufactured by Ketjen Black International Co., Ltd., BET surface area = 800 m ² / g) as a conductive carbon material, 8.7 g of 10% cerium nitrate aqueous solution and 10% zirconium nitrate aqueous solution 25.8 g was added and mixed. After stirring this mixture, 5% aqueous ammonia was added to form cerium-zirconium hydrate on the carbon surface. These were collected by filtration, dried at 150 ° C. for 12 hours, and then calcined at 500 ° C. for 2 hours. Thus, cerium-containing zirconium oxide (Ce _0.2 Zr _0
. 5.1 g of carbon carrying 0.1 g of ₈ O _Y1 ) was obtained.

  Next, 50 g of a 10% dinitrodiammineplatinic acid aqueous solution was added to 5.1 g of the cerium-containing zirconium oxide-supported carbon, mixed and stirred, and then platinum was precipitated using methanol as a reducing agent. As a result, 10.1 g of an electrode catalyst (Pt particles having an average particle diameter of 2.6 nm, Pt carrying concentration of 50% by mass) carrying platinum on cerium-containing zirconium oxide-carrying carbon was obtained.

  Five times the amount of purified water was added to 10.1 g of the electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 4.3 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.2 / 1.0.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by a screen printing method in an amount corresponding to the desired thickness in five portions and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the amount of Pt was 0.4 mg / cm ² (the average thickness of the cathode catalyst layer was 18 μm). Thus, a cathode catalyst layer coated sheet B27 was obtained.

3. Preparation of Electrolyte Membrane Electrode Assembly (MEA) Nafion NRE211 (film thickness 25 μm) as a solid polymer electrolyte membrane and an electrode catalyst layer formed on the previously prepared polytetrafluoroethylene sheet (anode catalyst layer coated on the anode side) Sheet A27 and a cathode catalyst layer coated sheet B27) were superposed on the cathode side. At that time, the anode catalyst layer, the solid polymer electrolyte membrane, and the cathode catalyst layer were laminated in this order. Thereafter, hot pressing was performed at 130 ° C. and 2.0 MPa for 10 minutes, and only the polytetrafluoroethylene sheet was peeled off to obtain a membrane electrode assembly (MEA) M27.

In this membrane electrode assembly M27, the electrode area of the cathode catalyst layer is 25 cm ² , the amount of Pt supported is 0.4 mg per 1 cm ^{2 of the} apparent electrode area, the electrode area of the anode catalyst layer is 25 cm ² , and the amount of Pt supported is apparent The electrode area was 0.2 mg per 1 cm ² .

4). 3. MEA Performance Evaluation The performance of the obtained membrane electrode assembly M27 was evaluated in the above Example 1 4. And evaluated in the same manner.

  Table 1 shows the compositions of the anode and cathode catalyst layers of this example and the results of the performance test.

Example 28
1. Preparation of anode catalyst layer Pt was supported on carbon black (Ketjen Black EC, manufactured by Ketjen Black International Co., Ltd., BET surface area = 800 m ² / g) as a conductive carbon material to obtain an electrode catalyst. The electrode catalyst had an average particle diameter of Pt particles of 2.6 nm and a Pt support concentration of 50% by mass. Five times the amount of purified water was added to 10 g of this electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 4.3 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.2 / 1.0. Next, 0.5 g of silica sol (solid content 10%, SiO ₂ average particle size 30 nm) was added to the mixed slurry.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by a screen printing method in three times according to the desired thickness, and dried at 60 ° C. for 24 hours. The size of the formed anode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the amount of Pt was 0.2 mg / cm ² (the average thickness of the anode catalyst layer was 8 μm). Thus, an anode catalyst layer coated sheet A28 was obtained.

2. Preparation of Cathode Catalyst Layer Pt was supported on carbon black (Ketjen Black EC, manufactured by Ketjen Black International Co., Ltd., BET surface area = 800 m ² / g) as a conductive carbon material to obtain an electrode catalyst. The electrode catalyst had an average particle diameter of Pt particles of 2.6 nm and a Pt support concentration of 50% by mass. Five times the amount of purified water was added to 10 g of this electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 4.3 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.2 / 1.0.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by a screen printing method in an amount corresponding to the desired thickness in five portions and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. The coating layer on the polytetrafluoroethylene sheet was adjusted so that the amount of Pt was 0.4 mg / cm ² (the average thickness of the cathode catalyst layer was 18 μm). In this way, a cathode catalyst layer coated sheet B28 was obtained.

3. Preparation of Electrolyte Membrane Electrode Assembly (MEA) Nafion NRE211 (film thickness 25 μm) as a solid polymer electrolyte membrane and an electrode catalyst layer formed on the previously prepared polytetrafluoroethylene sheet (anode catalyst layer coated on the anode side) The cathode catalyst layer coated sheet B28) was superposed on the sheet A28 and the cathode side. At that time, the anode catalyst layer, the solid polymer electrolyte membrane, and the cathode catalyst layer were laminated in this order. Thereafter, hot pressing was performed at 130 ° C. and 2.0 MPa for 10 minutes, and only the polytetrafluoroethylene sheet was peeled off to obtain a membrane electrode assembly (MEA) M28.

In this membrane electrode assembly M28, the electrode area of the cathode catalyst layer is 25 cm ² , the amount of Pt supported is 0.4 mg per 1 cm ^{2 of the} apparent electrode area, the electrode area of the anode catalyst layer is 25 cm ² , and the amount of Pt supported is apparent The electrode area was 0.2 mg per 1 cm ² .

4). MEA Performance Evaluation The performance of the membrane electrode assembly M28 thus obtained was evaluated in the above Example 1 4. And evaluated in the same manner.

  Table 1 shows the compositions of the anode and cathode catalyst layers of this example and the results of the performance test.

Example 29
1. Preparation of anode catalyst layer Pt was supported on carbon black (Ketjen Black EC, manufactured by Ketjen Black International Co., Ltd., BET surface area = 800 m ² / g) as a conductive carbon material to obtain an electrode catalyst. The electrode catalyst had an average particle diameter of Pt particles of 2.6 nm and a Pt support concentration of 50% by mass. Five times the amount of purified water was added to 10 g of this electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 4.3 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.2 / 1.0. Next, 0.5 g of silica sol (solid content 10%, SiO ₂ average particle size 30 nm) was added to the mixed slurry.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by screen printing in two portions according to the desired thickness and dried at 60 ° C. for 24 hours. The size of the formed anode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the amount of Pt was 0.2 mg / cm ² (the average thickness of the anode catalyst layer was 7 μm). Thus, an anode catalyst layer coated sheet A29 was obtained.

2. Preparation of Cathode Catalyst Layer Carbon black (Ketjen Black EC, manufactured by Ketjen Black International Co., Ltd., BET surface area = 800 m ² / g) as a conductive carbon material, 8.7 g of 10% cerium nitrate aqueous solution and 10% zirconium nitrate aqueous solution 25.8 g was added and mixed. After stirring this mixture, 5% aqueous ammonia was added to form cerium-zirconium hydrate on the carbon surface. These were collected by filtration, dried at 150 ° C. for 12 hours, and then calcined at 500 ° C. for 2 hours. Thus, 5.1 g of carbon carrying 0.1 g of cerium-containing zirconium oxide (Ce _0.2 Zr _0.8 O _Y1 ) was obtained.

  Next, 50 g of a 10% dinitrodiammineplatinic acid aqueous solution was added to 5.1 g of the cerium-containing zirconium oxide-supported carbon, mixed and stirred, and then platinum was precipitated using methanol as a reducing agent. As a result, 10.1 g of an electrode catalyst (Pt particles having an average particle diameter of 2.6 nm, Pt carrying concentration of 50% by mass) carrying platinum on cerium-containing zirconium oxide-carrying carbon was obtained.

  Five times the amount of purified water was added to 10.1 g of the electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 4.3 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.2 / 1.0.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by a screen printing method in an amount corresponding to the desired thickness in 6 portions and dried at 60 ° C. for 24 hours. The size of the formed cathode catalyst layer was 5 cm × 5 cm. The coating layer on the polytetrafluoroethylene sheet was adjusted so that the amount of Pt was 0.4 mg / cm ² (the average thickness of the cathode catalyst layer was 18 μm). Thus, a cathode catalyst layer coated sheet B29 was obtained.

3. Preparation of Electrolyte Membrane Electrode Assembly (MEA) Nafion NRE211 (film thickness 25 μm) as a solid polymer electrolyte membrane and an electrode catalyst layer formed on the previously prepared polytetrafluoroethylene sheet (anode catalyst layer coated on the anode side) The cathode catalyst layer coated sheet B29) was superposed on the sheet A29 and the cathode side. At that time, the anode catalyst layer, the solid polymer electrolyte membrane, and the cathode catalyst layer were laminated in this order. Thereafter, hot pressing was performed at 130 ° C. and 2.0 MPa for 10 minutes, and only the polytetrafluoroethylene sheet was peeled off to obtain a membrane electrode assembly (MEA) M29.

In this membrane electrode assembly M29, the electrode area of the cathode catalyst layer is 25 cm ² , the amount of Pt supported is 0.4 mg per 1 cm ^{2 of the} apparent electrode area, the electrode area of the anode catalyst layer is 25 cm ² , and the amount of Pt supported is apparent The electrode area was 0.2 mg per 1 cm ² .

4). MEA Performance Evaluation The performance of the membrane electrode assembly M29 thus obtained was evaluated in the above Example 1 4. And evaluated in the same manner.

  Table 1 shows the compositions of the anode and cathode catalyst layers of this example and the results of the performance test.

Example 30
1. Preparation of anode catalyst layer Pt was supported on carbon black (Ketjen Black EC, manufactured by Ketjen Black International Co., Ltd., BET surface area = 800 m ² / g) as a conductive carbon material to obtain an electrode catalyst. The electrode catalyst had an average particle diameter of Pt particles of 2.6 nm and a Pt support concentration of 50% by mass. Five times the amount of purified water was added to 10 g of this electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 4.3 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.2 / 1.0. Next, 6.0 g of activated carbon was added to the mixed slurry. In this example, the activated carbon had a BET surface area of 3000 m ² / g.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by a screen printing method in an amount corresponding to the desired thickness in 6 portions and dried at 60 ° C. for 24 hours. The size of the formed anode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the amount of Pt was 0.2 mg / cm ² (the average thickness of the anode catalyst layer was 10 μm). Thus, an anode catalyst layer coated sheet A30 was obtained.

2. Preparation of Cathode Catalyst Layer Pt was supported on carbon black (Ketjen Black EC, manufactured by Ketjen Black International Co., Ltd., BET surface area = 800 m ² / g) as a conductive carbon material to obtain an electrode catalyst. The electrode catalyst had an average particle diameter of Pt particles of 2.6 nm and a Pt support concentration of 50% by mass. Five times the amount of purified water was added to 10 g of this electrode catalyst, and a vacuum degassing operation was added for 5 minutes. To this, 4.3 times the amount of n-propyl alcohol was added, and a solution containing DE2020CS manufactured by DuPont (solution with a solid content of 20%, EW = 1,000) was added. The content of the polymer electrolyte in the solution was such that the mass ratio of the solid content to the carbon mass of the electrode catalyst was Ionomer / Carbon (I / C ratio) = 1.2 / 1.0. Next, 6.0 g of cerium oxide was added to the mixed slurry in the same manner as in Example 1.

The obtained mixed slurry was well dispersed with an ultrasonic homogenizer, and a catalyst slurry was prepared by applying a vacuum degassing operation. This was printed on one side of a polytetrafluoroethylene sheet by a screen printing method in an amount corresponding to the desired thickness in five portions and dried at 60 ° C. for 24 hours. The size of the formed anode catalyst layer was 5 cm × 5 cm. Further, the coating layer on the polytetrafluoroethylene sheet was adjusted so that the amount of Pt was 0.4 mg / cm ² . Thus, a cathode catalyst layer coated sheet B30 was obtained.

3. Production of electrolyte membrane electrode assembly (MEA) 1. The anode catalyst layer coated sheet A30 produced in 1 above and 2. Example 19 above except that the cathode catalyst layer coated sheet B30 produced in the above was used instead. In the same manner as above, an electrode assembly (MEA) M30 was obtained.

In this membrane electrode assembly M30, the electrode area of the cathode catalyst layer is 25 cm ² , the amount of Pt supported is 0.4 mg per 1 cm ^{2 of the} apparent electrode area, the electrode area of the anode catalyst layer is 25 cm ² , and the amount of Pt supported is apparent The electrode area was 0.2 mg per 1 cm ² .

4). 3. MEA Performance Evaluation The performance of the membrane electrode assembly M30 thus obtained was compared with that of Example 1 described above. And evaluated in the same manner.

  Table 1 shows the compositions of the anode and cathode catalyst layers of this example and the results of the performance test.

Comparative Example 1
1. Preparation of anode catalyst layer Example 3 In the same manner as above, an anode catalyst layer-coated sheet A3 was obtained.

2. Preparation of cathode catalyst layer Example 11 In the same manner as above, a cathode catalyst layer-coated sheet B11 was obtained.

3. Preparation of Electrolyte Membrane Electrode Assembly (MEA) Nafion NRE211 (film thickness 25 μm) as a solid polymer electrolyte membrane and an electrode catalyst layer formed on the previously prepared polytetrafluoroethylene sheet (anode catalyst layer coated on the anode side) The cathode catalyst layer coated sheet B11) was superposed on the sheet A3 and the cathode side. At that time, the anode catalyst layer, the solid polymer electrolyte membrane, and the cathode catalyst layer were laminated in this order. Thereafter, hot pressing was performed at 130 ° C. and 2.0 MPa for 10 minutes, and only the polytetrafluoroethylene sheet was peeled off to obtain a membrane electrode assembly (MEA) C1.

In this membrane electrode assembly C1, the electrode area of the cathode catalyst layer is 25 cm ² , the amount of Pt supported is 0.4 mg per 1 cm ^{2 of the} apparent electrode area, the electrode area of the anode catalyst layer is 25 cm ² , and the amount of Pt supported is apparent The electrode area was 0.2 mg per 1 cm ² .

4). MEA Performance Evaluation The performance of the membrane electrode assembly C1 thus obtained was evaluated in Example 1 4. And evaluated in the same manner.

  Table 1 shows the compositions of the anode and cathode catalyst layers of this example and the results of the performance test.

From Table 1 above, it is considered as follows.
-M1-30 which has a cathode catalyst layer and / or an anode catalyst layer according to the present invention exhibits significantly superior power generation performance as compared with C1 of Comparative Example 1.
-M19-26, 29, 30 having both the cathode catalyst layer and the anode catalyst layer according to the present invention is replaced with M1-18, 27, 28 having only one of the cathode catalyst layer or the anode catalyst layer according to the present invention. Compared to high power generation performance.
M9, 18, and 30 in which the content of a substance having an oxygen storage / release action and a hydrophilic substance is 27.3 mass% are 20% in the content of a substance having an oxygen storage / release action and a hydrophilic substance. The power generation performance is slightly inferior to that of mass% or less. From this, it is considered that the content of the substance having an oxygen storage / release action and the hydrophilic substance is preferably 20% by mass or less.

Claims (6)

A polymer electrolyte membrane, a cathode catalyst layer and a cathode-side gas diffusible electrode sequentially disposed on one side of the polymer electrolyte membrane, and an anode sequentially disposed on the other side of the polymer electrolyte membrane An electrolyte membrane-electrode assembly having a catalyst layer and an anode-side gas diffusing electrode,
The cathode catalyst layer includes a carrier on which a catalyst component is supported, a substance having an oxygen storage / release action, and a polymer electrolyte, and / or the anode catalyst layer is hydrophilic with a carrier on which the catalyst component is supported. An electrolyte membrane-electrode assembly comprising a material having a property and a polymer electrolyte. 2. The electrolyte membrane-electrode junction according to claim 1, wherein an average particle diameter of the catalyst component of the cathode catalyst layer is 1 to 5 nm, and / or an average particle diameter of the catalyst component of the anode catalyst layer is 1 to 5 nm. body. In the cathode catalyst layer, the substance having an oxygen storage / release action is a complex oxide of a rare earth element, and the content of the substance having an oxygen storage / release action is a substance having an oxygen storage / release action, a catalyst component, a carrier, and 0.01 to 20% by mass based on the total amount of the polymer electrolyte, and / or in the anode catalyst layer, the hydrophilic substance is a hydrophilic metal oxide or a high surface area carbon material, and The electrolyte membrane according to claim 1 or 2, wherein the content of the hydrophilic substance is 0.01 to 20% by mass with respect to the total amount of the hydrophilic substance, the catalyst component, the carrier and the polymer electrolyte. An electrode assembly. In the cathode catalyst layer, the substance having an oxygen storage / release function is CeO ₂ , ZrO ₂ , Ce _x1 Zr _1-x1 O _Y1 (x1 is an atomic ratio of Ce, and 0 <x1 <1, Y1 is , Pr _x2 Zr _1-x2 O _Y2 (x2 is the atomic ratio of Pr, 0 <x2 <1, Y2 is the number of oxygen atoms necessary to satisfy the valence of each component) , The number of oxygen atoms necessary to satisfy the valence of each of the above components), and Pr _x3 Ce _1-x3 O _Y3 (x3 is the atomic ratio of Pr, 0 <x3 <1, Y3 Is a complex oxide of at least one rare earth element selected from the group consisting of the number of oxygen atoms necessary to satisfy the valence of each component, and / or in the anode catalyst layer, material, TiO having sex Is at least one selected from the group consisting of _SiO 2, ZrO _2, and activated carbon, the electrolyte membrane according to any one of claims 1 to 3 - electrode assembly.   A fuel cell comprising the electrolyte membrane-electrode assembly according to any one of claims 1 to 4.   A vehicle equipped with the fuel cell according to claim 5.