JP2006338940A - Electrolyte membrane-electrode assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte membrane-electrode assembly in which decomposition of an electrolyte membrane at holding an OCV can be suppressed effectively. <P>SOLUTION: The assembly has a polyelectrolyte membrane, a first cathode catalyst layer arranged on one side of the polyelectrolyte membrane, a first anode catalyst layer arranged on the other side of the polyelectrolyte membrane, and a first gasket catalyst layer arranged on at least one part of the end of the first cathode catalyst layer. The assembly has a second cathode catalyst layer sandwiched by the polyelectrolyte membrane and the first cathode catalyst layer, and/or a second anode catalyst layer sandwiched by the polyelectrolyte membrane and the first anode catalyst layer. <P>COPYRIGHT: (C)2007,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 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 a gas diffusion layer and a separator. The electrolyte membrane-electrode assembly is obtained by sandwiching a polymer electrolyte membrane between a pair of electrode catalyst layers. Further, in order to prevent a fuel such as a hydrogen-containing gas and an oxidant gas from mixing with each other, the edge region of the MEA is sealed (Patent Documents 1 and 2).

In the polymer electrolyte fuel cell having the MEA as described above, the following electrochemical reaction proceeds. First, hydrogen contained in the fuel supplied to the anode side is oxidized by the catalyst component to become protons and electrons (2H ₂ → 4H ⁺ + 4e ⁻ ). Next, the generated protons pass through the solid polymer electrolyte contained in the electrode catalyst layer and the polymer electrolyte membrane in contact with the electrode catalyst layer, and reach the cathode side electrode catalyst layer. In addition, the electrons generated in the anode-side electrode catalyst layer include a conductive carrier constituting the electrode catalyst layer, a gas diffusion layer in contact with a side of the electrode catalyst layer different from the polymer electrolyte membrane, a separator, and an external circuit. To reach the cathode side electrocatalyst layer. 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). In the fuel cell, electricity can be taken out through the above-described electrochemical reaction.
JP-A-5-2442897 Japanese Patent Laid-Open No. 5-21077

  Conventionally, such a polymer electrolyte fuel cell has various problems. For example, there is a problem of deterioration of the electrolyte membrane in an idle stop (OCV: Open Circuit Voltage) state. This deterioration mechanism will be described with reference to FIG.

That is, since the electrolyte membrane does not completely block the gas (impermeability state), depending on the concentration gradient (partial pressure) of the oxidant gas or fuel, hydrogen flows from the anode side to the cathode side, Oxygen slightly permeates (dissolves and diffuses) toward the anode side (this phenomenon is also referred to as “cross leak”). In particular, at the time of OCV, the oxygen concentration at the interface between the cathode and the electrolyte membrane is higher than that at the time of power generation. Therefore, the amount of oxygen that dissolves and diffuses from the cathode side to the anode side through the electrolyte membrane is also larger than at the time of power generation. For this reason, oxygen moves from the cathode side to the anode side due to cross leak, and oxygen reacts directly with hydrogen on the anode side, causing a reaction of H ₂ + O ₂ → H ₂ O ₂ , resulting in hydrogen peroxide (H ₂ O ₂ ) is generated, hydrogen is transferred from the anode side to the cathode side, and hydrogen directly reacts with oxygen on the cathode side to similarly generate hydrogen peroxide.

  The hydrogen peroxide decomposes the electrolyte component (ionomer) contained in the electrolyte membrane or the anode or cathode, and chemically degrades the electrolyte membrane.

  The above-mentioned problem has been raised relatively recently. Currently, although a solution is strongly desired, no effective solution has been found. Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electrolyte membrane-electrode assembly that can effectively suppress decomposition of the electrolyte membrane during OCV holding.

  In order to achieve the above object, the present inventors diffuse the oxidant gas that has cross-leaked from the counter electrode into the anode catalyst layer and / or the fuel that has cross-leaked from the counter electrode diffuse into the cathode catalyst layer. In order to suppress this, it is possible to reduce the concentration of cross leak gas diffused in the catalyst layer by providing a second catalyst layer between the polymer electrolyte membrane and the catalyst layer. It has been found that the production of hydrogen peroxide can be suppressed. Furthermore, by forming a gasket layer on the polymer electrolyte membrane surface to prevent gas permeation at the end of the cathode catalyst layer, the amount of oxidant gas that cross leaks from the cathode side to the anode side can be reduced. It has been found that the production of hydrogen peroxide in the anode catalyst layer can be more effectively suppressed. Based on these findings, the present invention has been completed.

That is, the object is to provide a polymer electrolyte membrane,
A first cathode catalyst layer disposed on one side of the polymer electrolyte membrane;
A first anode catalyst layer disposed on the other side of the polymer electrolyte membrane;
An electrolyte membrane-electrode assembly having a first gasket layer formed on at least a part of an end of the first cathode catalyst layer,
A second cathode catalyst layer sandwiched between the polymer electrolyte membrane and the first cathode catalyst layer, and / or
This is achieved by an electrolyte membrane-electrode assembly having a second anode catalyst layer sandwiched between the polymer electrolyte membrane and the first anode catalyst layer.

  The electrolyte membrane-electrode assembly of the present invention can effectively prevent / suppress the decomposition of the electrolyte membrane during OCV holding. Further, the effective area of the first anode catalyst layer and / or the second anode catalyst layer is formed so as to be larger than the effective area of the first cathode catalyst layer and / or the second cathode catalyst layer. The performance during start / stop / continuous operation can be maintained for a longer period of time.

As described above, the present invention provides a polymer electrolyte membrane,
A first cathode catalyst layer disposed on one side of the polymer electrolyte membrane;
A first anode catalyst layer disposed on the other side of the polymer electrolyte membrane;
An electrolyte membrane-electrode assembly having a first gasket layer formed on at least a part of an end of the first cathode catalyst layer,
A second cathode catalyst layer sandwiched between the polymer electrolyte membrane and the first cathode catalyst layer, and / or
The present invention relates to an electrolyte membrane-electrode assembly having a second anode catalyst layer sandwiched between the polymer electrolyte membrane and the first anode catalyst layer.

  Hereinafter, the electrolyte membrane-electrode assembly of the present invention will be described taking a polymer electrolyte fuel cell using a hydrogen-containing gas as a fuel as an example.

  The electrolyte membrane-electrode assembly of the present invention (hereinafter also simply referred to as “MEA”) has a power generation reaction for the purpose of suppressing the diffusion of cross leak gas from the counter electrode into the catalyst layer that performs the power generation reaction. And a second catalyst layer between the catalyst layer and the polymer electrolyte membrane.

That is, in the MEA of the present invention, the layer having a function of reducing the oxidant gas that has cross-leaked from the cathode side that is the counter electrode on the anode side causes a reaction of 2H ₂ → 4H ⁺ + 4e ⁻ during operation (power generation). It has the structure formed between an anode catalyst layer and a polymer electrolyte membrane. As described above, since the layer having the function of reducing the oxidant gas exists between the polymer electrolyte membrane and the anode catalyst layer, the oxidant gas cross-leaked on the anode side diffuses into the anode catalyst layer. It is possible to suppress the generation of hydrogen peroxide in the anode catalyst layer.

In the present invention, the anode catalyst layer in which a reaction of 2H ₂ → 4H ⁺ + 4e ⁻ mainly occurs during operation (power generation) is referred to as a “first anode catalyst layer”, and the function of reducing cross leaked oxidant gas, A layer mainly having a function of decomposing hydrogen peroxide generated in the first anode catalyst layer is referred to as a “second anode catalyst layer”.

In the MEA of the present invention, the layer having a function of reducing fuel such as hydrogen-containing gas that has cross-leaked from the anode side, which is the counter electrode, on the cathode side is O ₂ + 4H ⁺ + 4e ⁻ → 2H during operation (power generation). It has a structure formed between a cathode catalyst layer where a ₂ O reaction occurs and a polymer electrolyte membrane. According to the layer having the function of reducing the fuel, it is possible to suppress the generation of hydrogen peroxide in the cathode catalyst layer in the same manner as the second anode catalyst layer described above.

In the present invention, the cathode catalyst layer in which the reaction of O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O mainly occurs during operation (power generation) is referred to as “first cathode catalyst layer”, and the fuel and the first anode catalyst layer A layer mainly having a function of decomposing the generated hydrogen peroxide is referred to as a “second cathode catalyst layer”.

  The MEA of the present invention only needs to have one of the second anode catalyst layer and the second cathode catalyst layer. However, since the production of hydrogen peroxide by the cross leak gas is more likely to occur in the anode catalyst layer, it is more preferable to have the second anode catalyst layer, and deterioration of the cathode catalyst layer in which the oxygen reduction reaction proceeds during operation. From the viewpoint of suppressing the above, it is preferable to have the second cathode catalyst layer. In addition, it is particularly preferable to have both the second anode catalyst layer and the second cathode catalyst layer from the viewpoint of more reliably suppressing the production of hydrogen peroxide by the cross leak gas.

  In the MEA of the present invention, it is possible to suppress the production of hydrogen peroxide in the MEA by having the second anode catalyst layer and / or the second cathode catalyst layer described above. Thereby, deterioration of the electrolyte component contained in the polymer electrolyte membrane and the first catalyst layer due to hydrogen peroxide can be prevented / suppressed to a higher degree, and a fuel cell using such an electrolyte membrane-electrode assembly is The performance during start / stop / continuous operation and OCV can be maintained for a longer period of time, and the fuel consumption can be further improved.

  Furthermore, the MEA of the present invention has a gas-impermeable gasket layer formed on at least a part of the end portion of the first cathode catalyst layer. By having the gasket layer, it is possible to more reliably suppress the oxidant gas from cross-leaking to the anode side, the amount of the oxidant gas supplied to the MEA can be reduced, and fuel efficiency is improved.

  In the present specification, the gasket layer formed and arranged at the end of the cathode catalyst layer is simply referred to as “first gasket layer”. Further, the gasket layer is formed on at least a part of the first cathode catalyst layer has a portion where the end of the first cathode catalyst layer and the end of the gasket layer overlap in the thickness direction of the MEA. The second cathode catalyst layer may be disposed between the portions where the end of the first cathode catalyst layer and the end of the gasket layer overlap.

  The first gasket layer is formed on the polymer electrolyte membrane from the end of the cathode catalyst layer toward the outside. However, considering the reduction in the amount of cross-leakage of the oxidant gas from the cathode side, the first gasket layer may be formed over the entire end portion of the first cathode catalyst layer and the entire peripheral portion of the polymer electrolyte membrane. preferable.

  In the MEA of the present invention, the effective area of the first anode catalyst layer and / or the second anode catalyst layer is larger than the effective area of the first cathode catalyst layer and / or the second cathode catalyst layer. It is preferable to be formed as follows.

In the present specification, the “effective area of the first anode catalyst layer” means an area of a region of the first anode catalyst layer in which a reaction of 2H ₂ → 4H ⁺ + 4e ⁻ occurs during operation (power generation). Specifically, it is the area of the polymer electrolyte membrane side surface in the first anode catalyst layer region that does not overlap the second gasket layer described later.

  Further, in this specification, the “effective area of the second anode catalyst layer” refers to the area of the second anode catalyst layer in which the function of reducing the oxidant gas or decomposing hydrogen peroxide occurs. Specifically, it is defined as the area of the polymer electrolyte membrane side surface in the second anode catalyst layer region that does not overlap the second gasket layer described later.

Further, in this specification, the “effective area of the first cathode catalyst layer” refers to a region in the first cathode catalyst layer where O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O reaction occurs during operation (power generation). Specifically, the area of the polymer electrolyte membrane side surface in the first cathode catalyst layer region that does not overlap with the first gasket layer.

  Further, in this specification, the “effective area of the second cathode catalyst layer” means an area of a region of the second cathode catalyst layer where a function of reducing fuel or decomposing hydrogen peroxide occurs. Specifically, it is the area of the polymer electrolyte membrane side surface in the second cathode catalyst layer region that does not overlap the first gasket layer.

In the conventional polymer electrolyte fuel cell, the position where the anode catalyst layer and the cathode catalyst layer are formed (with respect to the thickness direction of the electrolyte membrane-electrode assembly) is not completely matched, and there are many cases where misalignment occurs. The difference between the cathode potential and the electrolyte potential is particularly large in the cathode region where the anode is not opposed, and the corrosion of the carbon which is the conductive carrier (C + 2H ₂ O → CO ₂ + 4H ⁺ ) compared with the region where the anode exists (center portion). + 4e ⁻ ) occurs, and the catalytic activity is significantly reduced.

  Therefore, in the present invention, the effective area of the first and / or second anode catalyst layer is made larger than the effective area of the first and / or second cathode catalyst layer, whereby the first and / or second cathodes are formed. Since a portion where the difference between the cathode potential and the electrolyte potential is large in the catalyst layer can be significantly reduced, corrosion of carbon in the first and / or second cathode catalyst layer can be effectively prevented / suppressed.

  In addition, when the effective area of the first and / or second anode catalyst layer is larger than the effective area of the first and / or second cathode catalyst layer, the effective area in the first and / or second anode catalyst layer is high. A site where the first and / or second cathode catalyst layers do not exist is formed at a site facing through the molecular electrolyte membrane. In such a part in the first and / or second anode catalyst layer, since the first and / or second cathode catalyst layer does not exist, the cross leak amount of the oxidant gas supplied to the cathode side increases. There is a fear. However, in the present invention, since the end portions of the first and / or second cathode catalyst layers are sealed by the first gasket layer, the region where the oxidant gas cross leak occurs particularly significantly can be significantly reduced. . Therefore, the MEA having the above-described configuration has little or no surrounding portion where only the first and / or second cathode catalyst layer is present, and the cathode at the end of the first and / or second cathode catalyst layer. A structure in which little or no oxidant gas cross-leak from the anode to the anode can occur.

  Furthermore, by forming the first gasket layer at the end of the first cathode catalyst layer, the effective area in each catalyst layer can be adjusted easily and accurately. That is, conventionally, it has been difficult to adjust the formation position of each catalyst layer by adjusting the position where the catalyst layer ink is applied, but the effective area of each catalyst layer can be reduced by adjusting the arrangement of the gasket layer. Easy and accurate adjustment. Therefore, it is highly desirable when considering industrial mass production.

  Thus, in the present invention, the effective area of the first anode catalyst layer and / or the second anode catalyst layer is set larger than the effective area of the first cathode catalyst layer and / or the second cathode catalyst layer. Preferably, the effective area of the first anode catalyst layer and the second anode catalyst layer is preferably larger than the effective area of the first cathode catalyst layer or the second cathode catalyst layer. It is particularly preferred that the effective area of the second and second anode catalyst layers be greater than the effective area of the first and second cathode catalyst layers.

  In the present invention, it is essential to form the first gasket layer at the end of the first cathode catalyst layer, but at least a part of the end of the first anode catalyst layer, or It is preferable that a second gasket layer is further provided on at least a part of the periphery of the first anode catalyst layer. By forming a gasket layer on the anode catalyst layer side as well, the effective cathode catalyst layer and the effective anode catalyst layer can be aligned accurately and easily, and when the carbon support is corroded or OCV is maintained during start / stop / continuous operation. This is because the decomposition of the electrolyte membrane can be effectively prevented / suppressed. In the present specification, the gasket layer formed at the end of the anode catalyst layer is simply referred to as “second gasket layer”.

  Here, “to form the second gasket layer at the end” means that the first anode catalyst layer and the second gasket layer overlap with each other in the thickness direction. “To form a second gasket layer” means that the first anode catalyst layer and the second gasket layer do not overlap in the thickness direction. Further, the gasket layer overlaps at least a part of the end portion of the first anode catalyst layer has a portion where the end portion of the first anode catalyst layer and the end portion of the gasket layer overlap in the thickness direction of the MEA. The second anode catalyst layer may be disposed between the portions where the end of the first anode catalyst layer and the end of the gasket layer overlap.

  The second gasket layer is preferably formed on the polymer electrolyte membrane from the end of the first anode catalyst layer toward the outside. However, considering the ease of adjustment of the effective area of each catalyst layer and the sealing performance of gas (hydrogen-containing gas or oxidant gas), the second gasket layer is formed over the entire end portion of the first anode catalyst layer and the polymer. It is preferable to form a frame shape on the entire peripheral edge of the electrolyte membrane.

  In a preferred embodiment of the MEA of the present invention, on the anode side surface of the polymer electrolyte membrane, a first anode catalyst layer is formed in the central portion leaving the peripheral edge, and the edge of the first anode catalyst layer is formed in the peripheral edge. A form in which a second gasket layer is formed on the part and a second anode catalyst layer is formed between the first anode catalyst layer and the polymer electrolyte membrane can be mentioned. In addition, a first cathode catalyst layer is formed in the central portion of the polymer electrolyte membrane on the cathode side, leaving a peripheral portion, and a second gasket layer is formed on the peripheral portion at the end of the first cathode catalyst layer. And a second cathode catalyst layer formed between the first cathode catalyst layer and the polymer electrolyte membrane.

  In the present invention, it is a preferable requirement that the area of the effective anode catalyst layer is larger than the area of the effective cathode catalyst layer. At this time, the positional relationship between the effective anode catalyst layer and the effective cathode catalyst layer in the thickness direction of the MEA is: Although not particularly limited, when the effective cathode catalyst layer is completely included in the effective anode catalyst layer with respect to the thickness direction of the MEA as shown in FIG. 2 (a); or as shown in FIG. 2 (b), the MEA The effective cathode catalyst layer may be partially included in the effective anode catalyst layer with respect to the thickness direction, but the former case is more preferable. Similarly, the positional relationship of each catalyst layer is not particularly limited, but when the cathode catalyst layer is completely included in the anode catalyst layer with respect to the thickness direction of the MEA as shown in FIG. 2A; When the cathode catalyst layer is partially included in the anode catalyst layer with respect to the thickness direction of the MEA as shown in FIG. 2B; or with respect to the thickness direction of the MEA as shown in FIG. The cathode catalyst layer may be disposed at the same position as the anode catalyst layer. However, when the cathode catalyst layer is disposed at the same position as the anode catalyst layer, the cathode catalyst layer is disposed in the anode catalyst layer. The case where the cathode catalyst layer is completely included is more preferable, and the case where the cathode catalyst layer is completely included in the anode catalyst layer is particularly preferable.

  The second anode catalyst layer is formed between the first anode catalyst layer and the polymer electrolyte membrane, but the range formed between the first anode catalyst layer and the polymer electrolyte membrane is particularly limited. Not. That is, the second anode catalyst layer may be formed on at least a part of the end of the first anode catalyst layer. As a result, it is possible to reduce the amount of fuel cross leak and to reinforce the first anode catalyst layer and the polymer electrolyte membrane that are likely to be deteriorated by stress in the press treatment during MEA fabrication.

  The second cathode catalyst layer is formed between the first cathode catalyst layer and the polymer electrolyte membrane, but the range formed between the first cathode catalyst layer and the polymer electrolyte membrane is There is no particular limitation. That is, the second cathode catalyst layer may be formed on at least a part of the end portion of the first cathode catalyst layer in the same manner as the second anode catalyst layer. Thereby, it is possible to reduce the cross leak amount of the oxidant gas, and it is possible to reinforce the first cathode catalyst layer and the polymer electrolyte membrane.

  Thus, as a preferred embodiment of the MEA of the present invention, the second cathode catalyst layer is formed on at least a part of the end of the first cathode catalyst layer, and / or the second anode A form in which the catalyst layer is formed on at least a part of the end of the first anode catalyst layer can be mentioned.

  However, from the viewpoint of more reliably reducing the cross leak amount of fuel or oxidant gas in the MEA, the second catalyst layer on the cathode or anode side is provided over almost the entire surface of the first catalyst layer. It is particularly desirable. That is, the second cathode catalyst layer is formed on the entire surface of the first cathode catalyst layer on the polymer electrolyte membrane side, and / or the second anode catalyst layer is formed on the first anode catalyst layer. It is particularly desirable to form the entire surface on the polymer electrolyte membrane side.

  In the MEA of the present invention, the first gasket layer is formed at the end of the first cathode catalyst layer, and more preferably, the second gasket layer is formed at the end of the anode catalyst layer. Thereby, not only the amount of cross leak gas is reduced by improving the sealing performance of gas (hydrogen-containing gas or oxidant gas), but also the effective area of each catalyst layer can be adjusted easily and accurately. For this reason, it is not necessary to accurately align each catalyst layer in advance so that the end of each catalyst layer terminates at the same position in the thickness direction of the electrolyte membrane-electrode assembly. This is highly desirable when considering mass production.

  That is, the end portion of the second cathode catalyst layer and the end portion of the second anode catalyst layer are terminated at substantially the same position as shown in FIG. 3 with respect to the thickness direction of the electrolyte membrane-electrode assembly. However, the position may be shifted as shown in FIGS. This is because even in such a case, the gasket layer may be appropriately formed at the end of the catalyst layer so that each catalyst layer has a desired size and positional relationship. At this time, even if the end portion of the second anode catalyst layer is terminated beyond the end portion of the second cathode catalyst layer in the thickness direction of the electrolyte membrane-electrode assembly as shown in FIGS. Alternatively, the end of the second cathode catalyst layer may be terminated beyond the end of the second anode catalyst layer in the thickness direction of the electrolyte membrane-electrode assembly as shown in FIG. However, the end of the second anode catalyst layer is preferably terminated beyond the end of the second cathode catalyst layer in the thickness direction of the electrolyte membrane-electrode assembly. As described above, in the present invention, since the effective area of the second anode catalyst layer is preferably larger than the effective area of the second cathode catalyst layer, the second cathode catalyst layer is preliminarily attached to the second cathode catalyst layer in this way. By making it smaller than the size of the anode catalyst layer, the amount of catalyst and electrolyte to be used can be kept small, and the overlap with the gasket layer portion can be reduced, which is economically preferable.

  Further, the end portion of the first cathode catalyst layer and the end portion of the second cathode catalyst layer are as shown in FIGS. 3, 4, and 6 with respect to the thickness direction of the electrolyte membrane-electrode assembly. It may be terminated at substantially the same position, and a displacement may occur as shown in FIG. However, since the manufacturing method can be simplified by making each layer the same size, the end portion of the first cathode catalyst layer and the end portion of the second cathode catalyst layer are the electrolyte membrane electrode. It is desirable to terminate at substantially the same position with respect to the thickness direction of the joined body.

  Also, the end of the first anode catalyst layer and the end of the second anode catalyst layer are substantially the same as shown in FIGS. 3 to 6 with respect to the thickness direction of the electrolyte membrane-electrode assembly. It may be terminated at a position, or a displacement may occur. However, since the manufacturing method can be simplified in the same manner as described above, the end of the first anode catalyst layer and the end of the second anode catalyst layer have a thickness of the electrolyte membrane-electrode assembly. It is desirable to end at approximately the same position with respect to the direction.

  3 to 6 are for explaining a preferred embodiment of the MEA of the present invention, and are schematic views of the end portions of the catalyst layers in the MEA.

  The MEA of the present invention has a first gasket layer on at least a part of the end of the first cathode catalyst layer. At this time, as described above, the second cathode catalyst layer may be disposed between portions where the end portion of the first cathode catalyst layer and the end portion of the gasket layer overlap. In the part where each layer overlaps, the positional relationship between the end of the first cathode catalyst layer, the end of the second cathode catalyst layer, and the end of the first gasket layer is as follows. There is no particular limitation as long as the permeation of gas, particularly oxidant gas, can be sufficiently suppressed.

  For example, an end of the first gasket layer is inserted between the first cathode catalyst layer and the second cathode catalyst layer, and / or the second cathode catalyst layer and the height A positional relationship such as insertion between the molecular electrolyte membrane and the like can be preferably used. Specifically, all the end portions of the first gasket layer are formed between the first cathode catalyst layer and the second cathode catalyst layer, or the second cathode catalyst layer and the polymer. It may be inserted between the electrolyte membranes. In addition, a part of the end portion of the first gasket layer is inserted between the first cathode catalyst layer and the second cathode catalyst layer, and an end of the first gasket layer is formed. The remaining part of the part may be inserted between the second cathode catalyst layer and the polymer electrolyte membrane.

  The end portion of the first gasket layer may be disposed on the end portion of the first cathode catalyst layer, but the polymer electrolyte membrane is damaged by the press pressure at the time of manufacturing the MEA, and the anode catalyst layer and the cathode catalyst From the viewpoint of preventing a short circuit from coming into contact with the layer, the above-described positional relationship is preferably exemplified.

  Moreover, as a preferable form of MEA of this invention, the form which has the 2nd gasket layer formed in at least one part of the edge part of said 1st anode catalyst layer and said 2nd anode catalyst layer is mentioned. At this time, as described above, the second anode catalyst layer may be disposed between portions where the end of the first anode catalyst layer and the end of the second gasket layer overlap. In the portion where each layer overlaps, the positional relationship between the end of the first anode catalyst layer, the end of the second anode catalyst layer, and the end of the second gasket layer is as follows. There is no particular limitation as long as the permeation of fuel such as gas, particularly hydrogen-containing gas, can be sufficiently suppressed.

  For example, the end of the second gasket layer is inserted between the first anode catalyst layer and the second anode catalyst layer, and / or the second anode catalyst layer and the height The positional relationship inserted between the molecular electrolyte membrane is preferred. Specifically, all of the end portions of the second gasket layer are formed between the first anode catalyst layer and the second anode catalyst layer or between the second anode catalyst layer and the polymer. It may be inserted between the electrolyte membranes. In addition, a part of the end of the second gasket layer is inserted between the first anode catalyst layer and the second anode catalyst layer, and the end of the second gasket layer is inserted. The remaining part of the part may be inserted between the second anode catalyst layer and the polymer electrolyte membrane.

  The end of the second gasket layer may be disposed on the end of the first anode catalyst layer, but from the viewpoint of preventing a short circuit due to contact between the anode catalyst layer and the cathode catalyst layer during MEA fabrication. The above-mentioned positional relationship is preferably exemplified.

  The combination of the formation of the above layers is not particularly limited, but any combination of the above preferred examples may be used. Preferably, (1) the end of the first gasket layer is inserted between the end of the first cathode catalyst layer and the end of the second cathode catalyst layer, and the end of the second gasket layer Is inserted between the end of the first anode catalyst layer and the end of the second anode catalyst layer; and (2) the end of the first gasket layer is the second cathode catalyst. Inserted between the end of the layer and the polymer electrolyte membrane, and the end of the second gasket layer is inserted between the end of the first anode catalyst layer and the end of the second anode catalyst layer 4; (3) the end of the first gasket layer is inserted between the end of the first cathode catalyst layer and the end of the second cathode catalyst layer, and the second The form shown in FIG. 5 in which the end of the gasket layer is inserted between the end of the second anode catalyst layer and the polymer electrolyte membrane; (4) First The end of the sket layer is inserted between the end of the second cathode catalyst layer and the polymer electrolyte membrane, and the end of the second gasket layer is inserted into the end of the second anode catalyst layer and the polymer electrolyte. A combination of the forms shown in FIG. 6 inserted between the membrane is preferred.

  Of the above combinations, the second anode catalyst layer and / or the second cathode catalyst layer and the electrolyte membrane in the sense that the short circuit (contact between the anode / cathode catalyst layers) can be effectively prevented and the carbon corrosion hardly occurs. It is preferable that at least one of the first or second gasket layer is inserted between the first and second gasket layers. In this respect, the combination of (3), (4), and (5) is preferable. Especially, since manufacture is further easy, the combination of said (5) is used especially preferable.

  Next, components contained in each layer of the electrolyte membrane-electrode assembly of the present invention will be described.

  First, the catalyst layers used for the first and second, and the anode and the cathode, respectively, include an electrode catalyst in which a catalyst component is supported on a conductive carrier, and a polymer electrolyte.

  The catalyst components used in the first and second cathode catalyst layers are not particularly limited as long as they have a catalytic action for the oxygen reduction reaction, and known catalysts can be used in the same manner. The catalyst components used in the first and second anode catalyst layers are not particularly limited as long as they have a catalytic action in the hydrogen oxidation reaction, and known catalysts can be used in the same manner. Specifically, it is selected from platinum, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum and the like, and alloys thereof. 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 is preferably 30 to 90 atomic% for platinum and 10 to 70 atomic% for the metal to be alloyed, depending on the type of metal to be alloyed. The composition of the alloy when the alloy is used as a cathode catalyst varies depending on the type of metal to be alloyed and can be appropriately selected by those skilled in the art, but platinum is 30 to 90 atomic%, and other metals to be alloyed are 10 It is preferable to set it to -70 atomic%.

  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 component elements that form separate crystals, a component element that completely dissolves into a solid solution, and a component element that is 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.

  The catalyst component used for the first and second cathode catalyst layers and the catalyst component used for the first and second anode catalyst layers can be appropriately selected from the above. In the following description, unless otherwise specified, the descriptions of the catalyst components for the catalyst layers used in the first and second and cathode and anode are the same definitions for all, and collectively referred to as “catalyst components”. Called. However, the catalyst components for the catalyst layers used for the first and second, and the cathode and anode do not need to be the same, and are appropriately selected so as to achieve the desired action as described above.

  The shape and size of the catalyst component are not particularly limited, and the same shape and size as known catalyst components can be used, but the catalyst component is preferably granular. At this time, the smaller the average particle diameter of the catalyst particles used in the catalyst layer ink, the higher the effective electrode area where the electrochemical reaction proceeds. On the other hand, there is a phenomenon that the oxygen reduction activity decreases. Therefore, the average particle diameter of the catalyst particles contained in the catalyst layer ink is preferably 1 to 30 nm, more preferably 1.5 to 20 nm, still more preferably 2 to 10 nm, and particularly preferably 2 to 5 nm. . It is preferably 1 nm or more from the viewpoint of easy loading, and preferably 30 nm or less from the viewpoint of catalyst utilization. The “average particle diameter of the catalyst particles” in the present invention is the average value of the particle diameter of the catalyst component determined from the crystallite diameter or transmission electron microscope image determined from the half width of the diffraction peak of the catalyst component in X-ray diffraction. Can be measured.

  The electroconductive carrier in the electrode catalyst may be any electroconductive carrier as long as it has a specific surface area for supporting the catalyst component in a desired dispersed state and has sufficient electronic conductivity as a current collector. 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 conductive carrier may be a specific surface area sufficient to carry the catalyst component in a highly dispersed state, but is preferably 20 to 1600 m ² / g, more preferably 80 to 1200 m ² / g. Is good. The specific surface area, 20 m 2 / dispersibility of the catalyst component and the solid polymer electrolyte of ^g less than the that to the conductive support is lowered there is a possibility that sufficient power generation performance is obtained, a 1600 m 2 / ^g When it exceeds, there exists a possibility that the effective utilization factor of a catalyst component and a solid polymer electrolyte may fall on the contrary.

  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 amount exceeds 80% by mass, the degree of dispersion of the catalyst component on the conductive support is lowered, and although the loading amount is increased, the improvement in power generation performance is small and the economic advantage may be lowered. On the other hand, if the loading amount is less than 10% by mass, the catalytic activity per unit mass is lowered, and a large amount of electrode catalyst is required to obtain the desired power generation performance, which is not preferable. The amount of the catalyst component supported can be examined by inductively coupled plasma emission spectroscopy (ICP).

  The polymer electrolyte used in each of the catalyst layers used in the first and second and cathode and anode of the present invention is not particularly limited and a known one can be used, but at least a member having high proton conductivity If it is. Solid polymer electrolytes that can be used in this case are broadly classified into fluorine-based electrolytes that contain fluorine atoms in all or part of the polymer skeleton, and hydrocarbon-based electrolytes that do 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 of its excellent heat resistance and chemical stability. Among them, Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.) Fluorine electrolytes such as Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.) are preferred.

  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. Alternatively, a commercially available electrode catalyst may be used.

  What is necessary is just to determine suitably the mixing ratio of the electrode catalyst and polymer electrolyte in the 1st catalyst layer used for an anode and a cathode so that the electrolyte membrane electrode assembly which has desired power generation performance may be obtained. Specifically, the mixing ratio of the electrode catalyst and the polymer electrolyte is a mass ratio (electrode catalyst: polymer electrolyte), preferably 3: 1 to 1: 1, more preferably 3: 1 to 3: 2. It is good to do. If the ratio of the electrode catalyst in the catalyst layer is too small, an MEA having sufficient power generation performance may not be obtained. Even if the ratio of the electrode catalyst is too large, an improvement in power generation performance commensurate with the amount of increase in the electrode catalyst can be seen. This may lead to an increase in MEA costs.

  The thickness of the first catalyst layer used for the anode and the cathode is preferably 1 to 30 μm, more preferably considering the diffusibility of the gas supplied from the outside and the power generation performance of the electrolyte membrane-electrode assembly. It is good to set it as 1-20 micrometers.

The mixing ratio of the electrode catalyst and the polymer electrolyte in the second anode catalyst layer should be higher than that of the first anode catalyst layer from the viewpoint of improving proton conductivity from the anode to the cathode. . Specifically, the mixing ratio of the electrode catalyst and the polymer electrolyte is a mass ratio (electrode catalyst: polymer electrolyte), preferably 2: 1 to 1:10, more preferably 1: 1 to 1: 4. It is good to do. Since the second anode catalyst layer has the above-described composition, the oxidant gas that has cross-leaked from the cathode that is the counter electrode reacts with the fuel diffused from the anode catalyst layer to generate water (2H ₂ + O ₂ → 2H ₂ O), and the oxidant gas concentration on the anode side can be reduced. Further, even if the oxidant gas that has cross-leaked enters the first anode catalyst layer to generate hydrogen peroxide, the second anode catalyst layer has the above composition, so that It is also possible to cause decomposition (H ₂ O ₂ + H ₂ → 2H ₂ O) by reacting with the fuel diffused from the anode catalyst layer. Therefore, according to the second anode catalyst layer having the above-described composition, the generation of hydrogen peroxide can be suppressed by reducing the concentration of the oxidant gas that has cross-leaked. It is also possible to reduce the hydrogen oxide concentration, and the deterioration of the electrolyte components contained in the polymer electrolyte membrane and the first anode catalyst layer can be effectively suppressed.

  The thickness of the second anode catalyst layer is preferably 1 to 20 μm, more preferably 5 to 10 μm. If the thickness is less than 1 μm, the function of the second anode catalyst layer may not be sufficiently exerted. If the thickness exceeds 20 μm, proton conductivity between the first anode catalyst layer and the polymer electrolyte membrane decreases. Therefore, the power generation performance of the electrolyte membrane-electrode assembly may be deteriorated.

The mixing ratio of the electrode catalyst and the polymer electrolyte in the second cathode catalyst layer should be higher than that of the first cathode catalyst layer in terms of improving proton conductivity from the anode to the cathode. . Specifically, the mixing ratio of the electrode catalyst and the polymer electrolyte is a mass ratio (electrode catalyst: polymer electrolyte), preferably 2: 1 to 1:10, more preferably 1: 1 to 1: 4. It is good to do. When the second cathode catalyst layer has the above composition, hydrogen peroxide that has cross-leaked from the anode side can be decomposed (H ₂ O ₂ → O ₂ + 2H ⁺ + 2e ⁻ ). Furthermore, since the second cathode catalyst layer has a high potential like the first cathode catalyst layer, the decomposition reaction of hydrogen peroxide in the second cathode catalyst layer is promoted. As a result, it is possible to prevent hydrogen peroxide that has cross-leaked from the anode side from entering the first cathode catalyst layer, and to prevent deterioration of the electrolyte components contained in the first cathode catalyst layer. It becomes.

  The thickness of the second cathode catalyst layer is preferably 1 to 20 μm, more preferably 5 to 10 μm. If the thickness is less than 1 μm, the function of the second cathode catalyst layer may not be sufficiently exerted, and if it exceeds 20 μm, proton conductivity between the first cathode catalyst layer and the polymer electrolyte membrane decreases. Therefore, the power generation performance of the electrolyte membrane-electrode assembly may be deteriorated.

  Next, in the electrolyte membrane-electrode assembly of the present invention, a gasket layer is disposed on the peripheral portion of the polymer electrolyte membrane, and preferably the end of the gasket layer and the end of the catalyst layer are connected to each other in the electrolyte membrane-electrode assembly. The area of the effective catalyst layer is adjusted by overlapping in the thickness direction.

  The gasket layer may be impermeable to gas, particularly oxidant gas or hydrogen-containing gas, but generally, it is intended to adhere to the end of the polymer electrolyte membrane or the cathode / anode catalyst layer. It is composed of an adhesive layer and an impermeable layer made of a gas impermeable material. In this case, the material constituting the impermeable layer is not particularly limited as long as it is impermeable to oxygen or hydrogen-containing gas when formed into a film. Specific examples include polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), (polyvinylidene fluoride (PVDF), etc. The material that can be used for the adhesive layer is also a polymer electrolyte. There is no particular limitation as long as the membrane, the cathode / anode catalyst layer, and the gasket layer can be adhered closely, but hot melt adhesives such as polyolefin, polypropylene, thermoplastic elastomer, acrylic adhesives, polyester, polyolefin, etc. Olefin adhesives can be used.

  The thickness of the impermeable layer is not particularly limited, but is preferably 15 to 40 μm. The thickness of the adhesive layer is not particularly limited, but is preferably 10 to 25 μm.

  The polymer electrolyte membrane used in the MEA of the present invention is not particularly limited, and examples thereof include a membrane made of the same polymer electrolyte as that used for the catalyst layer. In addition, various Nafion (registered trademark of DuPont) manufactured by DuPont and perfluorosulfonic acid membranes represented by Flemion, ion exchange resins manufactured by Dow Chemical, ethylene-tetrafluoroethylene copolymer resin membrane, trifluoro Fluoropolymer electrolytes such as resin membranes based on styrene, hydrocarbon polymer membranes having sulfonic acid groups, and other commonly available solid polymer electrolyte membranes such as polytetrafluoroethylene (PTFE) ), A polymer microporous membrane made of polyvinylidene fluoride (PVDF), etc. impregnated with a liquid electrolyte such as phosphoric acid or ionic liquid, a porous material filled with a polymer electrolyte, etc. It may be used. The solid polymer electrolyte used for the polymer electrolyte membrane and the solid polymer electrolyte used for each electrode catalyst layer may be the same or different, but each electrode catalyst layer and the polymer electrolyte membrane From the viewpoint of improving the adhesiveness, it is preferable to use the same one.

  The thickness of the polymer electrolyte membrane may be appropriately determined in consideration of the properties of the obtained MEA, 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.

  The MEA according to the present invention may generally further include a gas diffusion layer, as will be described in detail below. The gas diffusion layer is not particularly limited, and known materials can be used in the same manner. For example, a base material is a sheet-like material having conductivity and porosity, such as a carbon woven fabric, a paper-like paper body, a felt, and a nonwoven fabric. And the like. 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.

  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. Although it does not specifically limit as said water repellent, It is fluorine-type, such as a polytetrafluoroethylene (PTFE), a polyvinylidene fluoride (PVDF), a polyhexafluoropropylene, a tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Examples thereof include polymer materials, 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 between the carbon particles and the water repellent may be insufficient to obtain the water repellency as expected when the carbon particles are too much. 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.

  As described above, the electrolyte membrane-electrode assembly of the present invention can suppress the corrosion of the carbon carrier used as the catalyst carrier and the deterioration of the electrolyte component contained in the electrolyte membrane-electrode assembly. In addition, by providing a gasket layer, it is possible to easily determine the area and arrangement of the catalyst layer, and it is not necessary to accurately align each catalyst layer in advance, so industrial mass production is considered. This is highly desirable. Therefore, by using such an electrolyte membrane-electrode assembly, it is possible to provide a highly reliable fuel cell that has a simple manufacturing process and excellent durability.

  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. However, in addition to the above, an alkaline fuel cell, a phosphoric acid fuel cell, Typical examples include acid electrolyte fuel cells, direct methanol fuel cells, and micro fuel cells. Among these, a polymer electrolyte fuel cell is preferable because it is small in size, and can achieve high density and high output.

  The fuel supplied to the anode side of the fuel cell has been described by taking a hydrogen-containing gas as an example because the solid polymer fuel cell has been described as an example in the above description. However, the present invention is not limited to this, and the fuel supplied to the anode side of the fuel cell can be used in any form of gas and liquid, and hydrogen-containing gas and methanol can also be used, depending on the type of fuel cell. Are appropriately selected.

  The polymer electrolyte fuel cell is useful not only as a stationary power source but also as a power source for a moving body such as an automobile having a limited mounting space. In particular, moving bodies such as automobiles that are susceptible to corrosion of the carbon support due to the high output voltage required after a relatively long shutdown, and deterioration of the polymer electrolyte due to the high output voltage being taken out during operation. It is particularly preferred to be used as a power source.

  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 is further provided at a portion on the gasket layer where the first and / or second catalyst layers are not formed. May be. 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.

  Below, the manufacturing method of the 1st electrolyte membrane electrode assembly of this invention is demonstrated. The electrolyte membrane-electrode assembly of the present invention can be produced by using a method obtained by appropriately modifying a known method. Specifically, on the polymer electrolyte membrane, a second cathode catalyst layer and / or a second anode catalyst layer, a first cathode catalyst layer, a first anode catalyst layer, and a first gasket layer, and If necessary, a method of forming the second gasket layer in an appropriate arrangement, for example, a combination of the above (1) to (4) can be used. That is, as a method for producing the electrolyte membrane-electrode assembly of the present invention, the following methods (1) to (4) are preferably exemplified.

(1) After the second cathode catalyst layer is formed on the cathode side surface of the polymer electrolyte membrane, the first gasket catalyst layer is covered with the first gasket layer so that the end of the first gasket layer covers the first cathode catalyst layer. Forming a gasket layer of;
A surface of the second cathode catalyst layer which is exposed without being formed with the first gasket layer, and at least a part of an overlapping portion between the first gasket layer and the second cathode catalyst layer; Forming a first cathode catalyst layer to coat;
After the second anode catalyst layer is formed on the anode side surface of the polymer electrolyte membrane, the second anode catalyst layer is covered with the second gasket layer so that the end of the second gasket layer covers the second anode catalyst layer. Forming the gasket layer; and the surface of the second anode catalyst layer that is exposed without being formed with the second gasket layer, and the second gasket layer and the second anode catalyst layer. Forming a first anode catalyst layer so as to cover at least a part of the overlapping portion. According to the method (1), as shown in FIG. 2, the gasket layer is formed between the end of the first catalyst layer and the end of the second catalyst layer on both the cathode side and the anode side. The end is arranged.

(2) After forming the first gasket layer on the cathode side surface of the polymer electrolyte membrane, the end of the first gasket layer is connected to the end of the second cathode catalyst layer and the first cathode catalyst layer. Forming the second cathode catalyst layer and the first cathode catalyst layer so as to coat;
After forming the second anode catalyst layer on the anode side surface of the polymer electrolyte membrane, the second anode catalyst layer is covered with the second gasket layer so that the end of the second gasket layer covers the second anode catalyst layer. Forming a gasket layer; and the surface of the second anode catalyst layer that is exposed without being formed with the second gasket layer, and the second gasket layer and the second anode catalyst layer. Forming a first anode catalyst layer to cover at least a portion of the overlapping portion. According to the method, as shown in FIG. 3, the end of the second gasket layer is arranged between the polymer electrolyte membrane and the end of the second cathode catalyst layer on the cathode side, and the first side on the anode side. The end of the second gasket layer is disposed between the end of one anode catalyst layer and the end of the second anode catalyst layer.

(3) After the second cathode catalyst layer is formed on the cathode side surface of the polymer electrolyte membrane, the end portion of the second cathode catalyst layer is covered with the end portion of the first gasket layer. Forming a first gasket layer;
A surface of the second cathode catalyst layer which is exposed without being formed with the first gasket layer, and at least a part of an overlapping portion between the first gasket layer and the second cathode catalyst layer; Forming a first cathode catalyst layer for coating; and
After the second gasket layer is formed on the anode side surface of the polymer electrolyte membrane, the ends of the second gasket layer are covered with the ends of the second anode catalyst layer and the first anode catalyst layer. Forming the second anode catalyst layer and the first anode catalyst layer. According to the above method, as shown in FIG. 4, the end of the first gasket layer is disposed between the end of the first cathode catalyst layer and the end of the second cathode catalyst layer on the cathode side. On the anode side, the end of the second gasket layer is disposed between the polymer electrolyte membrane and the end of the second anode catalyst layer.

(4) After the first gasket layer is formed on the cathode side surface of the polymer electrolyte membrane, the end portions of the first gasket layer are connected to the end portions of the second cathode catalyst layer and the first cathode catalyst layer. Forming the second cathode catalyst layer and the first cathode catalyst layer so as to cover; and, after forming a second gasket layer on the anode side surface of the polymer electrolyte membrane, Forming the second anode catalyst layer and the first anode catalyst layer so that at least the second anode catalyst layer and the first anode catalyst layer end portions are covered with the end portions of the gasket layer A method comprising: According to the above method, an electrolyte membrane-electrode assembly having a configuration in which the end of each gasket layer is disposed between the polymer electrolyte membrane and the end of the second catalyst layer as shown in FIG. It is done.

  According to the method of the present invention, in addition to the second cathode catalyst layer and / or the second anode catalyst layer, the first cathode catalyst layer, the first gasket layer, the first anode catalyst layer, and if necessary, The second gasket layer can be placed accurately and easily in the desired order. In addition, the method of said (1)-(4) described the order of the preferable process of forming each layer in MEA, and the manufacturing method of MEA of this invention is the method of said (1)-(4). It is not limited.

  In the method of the present invention, the formation positions of the first gasket layer and the second gasket layer are preferably adjusted so that the effective area of the anode catalyst layer is larger than the effective area of the cathode catalyst layer.

  By arranging the first gasket layer and, if necessary, the second gasket layer at the ends of the first cathode catalyst layer and the first anode catalyst layer, respectively, the effective area of each catalyst layer is accurately defined. can do. Therefore, since the first gasket layer is formed at the end of the first cathode catalyst layer, and preferably the second gasket layer is formed at the end of the first anode catalyst layer, the alignment of each catalyst layer is accurate. It is not always necessary, and the manufacturing method can be simplified. That is, the end portions of the first and second cathode catalyst layers and the end portions of the first and second anode catalyst layers are terminated at substantially the same position in the thickness direction of the electrolyte membrane-electrode assembly. However, the positions of the end portions of the first and second cathode catalyst layers and the end portions of the first and second anode catalyst layers may be shifted. This is because even in such a case, the gasket layer may be appropriately formed at the end of the catalyst layer so that each catalyst layer is in a desired size and position. Therefore, each layer may be formed or arranged so that the position where the end of each layer ends in the thickness direction of the MEA is a desired position. The position where the end of each layer ends in the thickness direction of the MEA is as described above.

  Further, in the method of the present invention, when the above-described methods (1) to (4) are used, a gasket layer exists between the polymer electrolyte membrane and the catalyst layer. In addition, there is an advantage that it is possible to prevent the end portions of the catalyst layers from coming into contact with each other due to breakage of the polymer electrolyte membrane when laminated as a fuel cell stack, thereby causing a short circuit of the edge portions.

In the method of the present invention, in particular, the positions of the end portions of the first and second cathode catalyst layers and the end portions of the first and second anode catalyst layers are relative to the thickness direction of the electrolyte membrane-electrode assembly. If they are offset, there is as little gap as possible between the ends of the first and second cathode catalyst layers and the ends of the first and second anode catalyst layers (eg, in FIG. “X” is preferably close to 0). This is because, when such a gap portion exists, even if electrons (e ⁻ ) and protons (H ⁺ ) generated in this portion move to the first cathode catalyst layer side, the effective area of the anode catalyst layer becomes the cathode. This is because the protons and electrons cannot efficiently react with oxygen on the cathode side and the catalytic action does not work effectively because it is larger than the effective area of the catalyst layer. In consideration of this, the width (X) of the gap portion between the end portions of the first and second cathode catalyst layers and the end portions of the first and second anode catalyst layers is 1 cm or less. More preferably, it is 3 mm or less.

  In the method of the present invention, in order to form the second catalyst layer in the anode and the cathode, a second catalyst layer ink containing an electrode catalyst, a polymer electrolyte, and a solvent in a predetermined mixing ratio is added to the surface of the polymer electrolyte membrane. Alternatively, a method of applying and drying the surface of the polymer electrolyte membrane in a state where the gasket layer is partially covered is used. In addition, since the same method is used as a formation method of a 2nd anode catalyst layer and a 2nd cathode catalyst layer, it demonstrates collectively as a formation method of a 2nd catalyst layer.

  The solvent used in the second catalyst layer ink is not particularly limited, and usual solvents used for forming the catalyst layer can be used in the same manner. Specifically, water, lower alcohols such as cyclohexanol, ethanol and 2-propanol can be used.

  The content of the solids such as the electrode catalyst and the polymer electrolyte in the second catalyst layer ink is preferably 5 to 40% by mass, more preferably 10 to 35% by mass, based on the total amount of the second catalyst layer ink. It is good to do. The mixing ratio of the electrode catalyst and the polymer electrolyte in the second catalyst layer ink is a mass ratio (electrode catalyst: polymer electrolyte), preferably 2: 1 to 1:10, more preferably 1: 1 to 1. It should be 1: 4.

  As a method for applying the second catalyst layer ink, known methods such as a die coater method, a screen printing method, a doctor blade method, and a spray method can be used. The drying of the applied second catalyst layer ink is not particularly limited, but it is 25 to 150 ° C., more preferably 60 to 120 ° C. for 5 to 30 minutes, more preferably 10 in a vacuum dryer or under reduced pressure. It can be done for ~ 20 minutes. In addition, in the said process, when the thickness of a 2nd catalyst layer is not enough, you may repeat the said application | coating and drying process until it becomes desired thickness.

  Next, in order to form the first catalyst layer in the anode and the cathode, the first catalyst layer ink containing the electrode catalyst, the polymer electrolyte, and the solvent is applied to the surface of the second catalyst layer or the gasket layer. A method of applying and drying on the surface of the second catalyst layer in such a state that it is coated is used. As the solvent, the same solvents as described above are used. In addition, since the same method is used as a formation method of a 1st anode catalyst layer and a 1st cathode catalyst layer, it demonstrates collectively as a formation method of a 1st catalyst layer.

  The content of solids such as an electrode catalyst and a polymer electrolyte in the first catalyst layer ink is preferably 5 to 30% by mass, more preferably 10 to 25% by mass, based on the total amount of the first catalyst layer ink. It is good to do. The mixing ratio of the electrode catalyst to the polymer electrolyte in the first catalyst layer ink is a mass ratio (electrode catalyst: polymer electrolyte), preferably 3: 1 to 1: 1, more preferably 3: 1 to 1. 3: 2 is good.

  As a method for applying and drying the first catalyst layer ink, the same method as described above for the second catalyst layer is used.

  The polymer electrolyte and electrode catalyst used in the first catalyst layer ink and the second catalyst layer ink are as described above in the first aspect of the present invention.

  The second catalyst layer ink and / or the first catalyst layer ink may include a thickener. The use of a thickener is effective when each ink cannot be applied well. The thickener that can be used in this case is not particularly limited, and a known thickener can be used. Examples thereof include glycerin, ethylene glycol (EG), polyvinyl alcohol (PVA), and propylene glycol (PG). When the thickener is used, the amount of the thickener added is not particularly limited as long as it does not interfere with the above effect of the present invention, but the first catalyst layer ink or the second catalyst layer ink is not limited. Preferably it is 5-20 mass% with respect to the total mass.

  The formation method in particular of a gasket layer is not restrict | limited, A well-known method can be used. For example, the adhesive may be applied to at least a part of the peripheral edge on the polymer electrolyte membrane or at least a part of the peripheral edge on the polymer electrolyte membrane while covering the end of the second catalyst layer. After applying to a thickness of 30 μm, the above-described gas-impermeable material is applied, and a method of curing the adhesive by heating it at 25 to 150 ° C. for 10 seconds to 10 minutes can be used. . Alternatively, after the gas impermeable material is formed into a sheet shape in advance, an adhesive is applied to the impermeable film to form a gasket layer, which is then applied to at least a part of the peripheral portion on the polymer electrolyte membrane. Or you may affix on at least one part of the peripheral part on a polymer electrolyte membrane, coat | covering a part of 2nd catalyst layer.

  In the above description, the method for forming the first catalyst layer and the second catalyst layer on the polymer electrolyte membrane by directly applying each ink has been described. It may be manufactured by other methods. The production method in such a case is not particularly limited, and can be used by appropriately modifying a known transfer method.

  The electrolyte membrane-electrode assembly of the present invention may further have a gas diffusion layer. When the gas diffusion layer is disposed in the electrolyte membrane-electrode assembly, the electrolyte membrane-electrode assembly obtained as described above may be further sandwiched between the gas diffusion layers. At this time, hot pressing may be performed in order to improve the bondability between the gas diffusion layer and the catalyst layer. The hot pressing conditions are the same as the hot pressing conditions described above when enhancing the bondability between the second catalyst layer and the polymer electrolyte membrane.

  The electrolyte membrane-electrode assembly (MEA) of the present invention can be applied to a fuel cell having excellent durability and good fuel efficiency.

It is explanatory drawing which shows the cross leak of oxygen at the time of OCV holding | maintenance. It is a figure which shows arrangement | positioning of the effective cathode catalyst layer, effective anode catalyst layer, cathode catalyst layer, and anode catalyst layer in MEA of this invention. It is a figure which shows the structure of MEA by the 1st embodiment of this invention. It is a figure which shows the structure of MEA by the 2nd embodiment of this invention. It is a figure which shows the structure of MEA by the 3rd embodiment of this invention. It is a figure which shows the structure of MEA by the 4th embodiment of this invention.

Claims (11)

A polymer electrolyte membrane;
A first cathode catalyst layer disposed on one side of the polymer electrolyte membrane;
A first anode catalyst layer disposed on the other side of the polymer electrolyte membrane;
An electrolyte membrane-electrode assembly having a first gasket layer formed on at least a part of an end of the first cathode catalyst layer,
A second cathode catalyst layer sandwiched between the polymer electrolyte membrane and the first cathode catalyst layer, and / or
An electrolyte membrane-electrode assembly having a second anode catalyst layer sandwiched between the polymer electrolyte membrane and the first anode catalyst layer.   The electrolyte membrane-electrode assembly according to claim 1, comprising the second cathode catalyst layer and the second anode catalyst layer.   The effective area of the first anode catalyst layer and / or the second anode catalyst layer is formed to be larger than the effective area of the first cathode catalyst layer and / or the second cathode catalyst layer. The electrolyte membrane-electrode assembly according to claim 1 or 2.   The second gasket layer formed on at least a part of an end of the first anode catalyst layer or at least a part of a peripheral part of the first anode catalyst layer. The electrolyte membrane-electrode assembly according to any one of the above.   The second cathode catalyst layer is formed on at least a part of an end portion of the first cathode catalyst layer, and / or the second anode catalyst layer is formed on an end portion of the first anode catalyst layer. The electrolyte membrane-electrode assembly according to any one of claims 1 to 4, which is formed at least in part.   The second cathode catalyst layer is formed on the entire surface of the first cathode catalyst layer on the polymer electrolyte membrane side, and / or the second anode catalyst layer is higher than the first anode catalyst layer. The electrolyte membrane-electrode assembly according to any one of claims 1 to 4, formed on the entire surface of the molecular electrolyte membrane.   The end of the second anode catalyst layer and the end of the second cathode catalyst layer terminate at substantially the same position in the thickness direction of the electrolyte membrane-electrode assembly. 6. The electrolyte membrane-electrode assembly according to any one of 6 above.   The end of the second anode catalyst layer terminates beyond the end of the second cathode catalyst layer with respect to the thickness direction of the electrolyte membrane-electrode assembly, or the end of the second cathode catalyst layer The electrolyte membrane-electrode assembly according to any one of claims 1 to 6, wherein the end ends beyond the end of the second anode catalyst layer with respect to the thickness direction of the electrolyte membrane-electrode assembly.   The end portion of the first cathode catalyst layer and the end portion of the second cathode catalyst layer terminate at substantially the same position in the thickness direction of the electrolyte membrane-electrode assembly, and / or The end portion of the anode catalyst layer and the end portion of the second anode catalyst layer terminate at substantially the same position in the thickness direction of the electrolyte membrane-electrode assembly. Electrolyte membrane-electrode assembly.   An end of the first gasket layer is inserted between the first cathode catalyst layer and the second cathode catalyst layer, and / or the second cathode catalyst layer and the polymer electrolyte. The electrolyte membrane-electrode assembly according to any one of claims 1 to 9, which is inserted between the membrane and the membrane.   An end of the second gasket layer is inserted between the first anode catalyst layer and the second anode catalyst layer, and / or the second anode catalyst layer and the polymer electrolyte. The electrolyte membrane-electrode assembly according to any one of claims 4 to 10, which is inserted between the membrane.

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