JP2006338939A - Electrolyte membrane-electrode assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte membrane-electrode assembly in which increase in volume of a cell and a stack, and reduction in power generation performance caused accompanying complication in a configuration of an MEA can be suppressed to the minimum. <P>SOLUTION: The assembly has a cathode catalyst layer formed on one surface of a polyelectrolyte membrane, an anode catalyst layer formed on the other surface, and a first gasket layer formed on at least one part of the end of the cathode catalyst layer. The thicknesses of one or more kinds selected from the group consisting of the polyelectrolyte membrane, the cathode catalyst layer, the anode catalyst layer, and the first gasket layer are formed to be thinner than those of the other sites of the assembly at the overlapping site so that at least the thickness of the assembly at a site where the cathode catalyst layer and the first gasket layer are overlapped with each other becomes approximately equal to that of the assembly at an existing part of the first gasket layer where the cathode catalyst layer and the first gasket layer are not overlapped with each other. <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 particular, the present invention is an electrolyte membrane-electrode junction in which decomposition of the electrolyte membrane during OCV (Open Circuit Voltage) holding assuming idling stop operation is suppressed, and corrosion of the cathode catalyst is preferably suppressed during start / stop / continuous operation. It relates to the body (MEA).

  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.

In the polymer electrolyte fuel cell having the MEA as described above, the following electrochemical reaction proceeds. First, hydrogen contained in the fuel gas 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.

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 oxygen or hydrogen gas, hydrogen flows from the anode side to the cathode side, and from the cathode side to the anode side. Oxygen and nitrogen are slightly permeated (dissolved and diffused) toward the 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. It is known that this hydrogen peroxide decomposes the electrolyte component (ionomer) contained in the electrolyte membrane or the anode or cathode to chemically deteriorate the electrolyte membrane. Here, considering the relationship between the potential of the anode catalyst layer and the cathode catalyst layer and the decomposition reaction of hydrogen peroxide, the potential is relatively high (about 0.6 to 1 V) with respect to the electrolyte potential. The hydrogen peroxide that cross-leaked from the anode catalyst layer directly reacts with the oxygen of the anode, so that the hydrogen peroxide that is produced becomes oxygen and proton relatively quickly by the reaction of H ₂ O ₂ → O ₂ + 2H ⁺ + 2e ^−. Decompose. On the other hand, since the potential is low on the anode side, the above-described decomposition reaction of hydrogen peroxide hardly occurs. For this reason, hydrogen peroxide generated frequently on the anode side moves into the electrolyte membrane due to concentration diffusion, oxidatively degrades the electrolyte membrane, or the presence of cations (eg, Fe ²⁺ , Cu ²⁺ ) in the electrolyte membrane. As a result, the electrolyte membrane components are deteriorated at an accelerated rate.

Incidentally, sealing of the edge region of the MEA is described in Patent Documents 1 and 2. Patent Document 1 discloses a solid polymer in which the electrode peripheral portion of the solid polymer electrolyte membrane and the electrode are not arranged for the purpose of preventing the damage of the solid polymer electrolyte membrane by increasing the mechanical strength of the outer edge of the solid polymer electrolyte membrane. It is described that the outer edge portion of the electrolyte membrane is covered with a reinforcing membrane, and the gas seal portion is disposed on the outer edge portion of the solid polymer electrolyte membrane. Patent Document 2 discloses a frame-shaped protective film, a gas sealing material and an electrode for the purpose of preventing damage to the solid polymer electrolyte film due to differential pressure of reaction gas applied to the solid polymer electrolyte film or mechanical stress. It describes that it forms in the peripheral part of a solid polymer electrolyte membrane so that both peripheral parts may be coat | covered.
JP-A-5-2442897 Japanese Patent Laid-Open No. 5-21077

  However, Patent Documents 1 and 2 aim to improve the mechanical strength of the outer edge of the solid polymer electrolyte membrane. In the structures described in these Patent Documents, the decomposition of the electrolyte membrane as described above is suppressed. Is not taken into consideration, and therefore, the problem that the portion of the electrolyte membrane subjected to a relatively large mechanical stress undergoes decomposition and degradation in a relatively short time and the durability deteriorates cannot be solved sufficiently. In particular, in the MEA disclosed in Patent Document 1, a reinforcing layer having a uniform thickness is formed so as to overlap the catalyst layer. However, such overlapping portions not only increase the volume of the MEA and cause an increase in the volume of the fuel cell and the stack, but also reduce the smoothness of the catalyst layer and the gas diffusion layer to reduce the power generation performance. There is also.

  Furthermore, the above-mentioned problem has been raised relatively recently. At present, a solution is strongly desired, but no effective solution has been found.

  Therefore, the present invention has been made in view of the above circumstances, and an electrolyte membrane-electrode that can suppress the increase in volume of cells and stacks and the decrease in power generation performance that are caused by the complexity of the MEA configuration. An object is to provide a joined body.

  As a result of intensive studies to achieve the above object, the present inventors have found that an anode catalyst is formed by forming a gasket layer at the end of the cathode catalyst layer, preferably at the ends of the cathode catalyst layer and the anode catalyst layer. It has been found that the size of each layer and the cathode catalyst layer can be easily controlled, and that the alignment of each catalyst layer is easy. Further, in particular, by taking the above-described configuration, there is no cathode catalyst layer facing through the polymer electrolyte membrane, and the periphery where only the anode catalyst layer is present is sealed with a gas-impermeable gasket layer. Oxygen cross-leak from the cathode to the anode, which has occurred remarkably at the end of the cathode catalyst layer, can be suppressed, and the production of hydrogen peroxide on the anode side in the region can be significantly suppressed. It has been found that deterioration of can be effectively prevented / suppressed. At this time, it has also been found that by making the size of the anode catalyst layer larger than that of the cathode catalyst layer, carbon corrosion of the cathode catalyst layer can be effectively prevented / suppressed. Further, when the MEA having the above-described configuration is manufactured, a cell newly generated by adopting the above-described configuration by controlling the thickness of each component of the MEA that overlaps with other layers. The inventors have found that problems such as an increase in stack volume and a decrease in power generation performance can be suppressed to a minimum, and the present invention has been completed.

  That is, the object is to provide a polymer electrolyte membrane, a cathode catalyst layer formed on one side of the polymer electrolyte membrane, an anode catalyst layer formed on the other side of the polymer electrolyte membrane, A first gasket layer formed on at least a part of an end of the cathode catalyst layer, and a thickness of an electrolyte membrane-electrode assembly at an overlapping portion of the cathode catalyst layer and the first gasket layer Is approximately equal to the thickness of the electrolyte membrane-electrode assembly where the first gasket layer does not overlap the cathode catalyst layer and the first gasket layer. One or two or more thicknesses selected from the group consisting of a catalyst layer, the anode catalyst layer, and the first gasket layer are formed to be thinner than the other portions of the overlapping portion. Electrolyte membrane - is achieved by the electrode assembly.

  Further, the object is to provide a polymer electrolyte membrane, a cathode catalyst layer formed on one surface of the polymer electrolyte membrane, an anode catalyst layer formed on the other surface of the polymer electrolyte membrane, A first gasket layer formed on at least a part of the end of the cathode catalyst layer; and a second gasket layer formed on at least a part of the end of the anode catalyst layer, The thickness of the electrolyte membrane-electrode assembly where the catalyst layer and the first gasket layer overlap is such that the cathode catalyst layer and the first gasket layer do not overlap each other. The thickness of the electrolyte membrane-electrode assembly at the overlapping portion of the anode catalyst layer and the second gasket layer is set to be substantially equal to the thickness of the membrane-electrode assembly, and the thickness of the anode catalyst layer and the second electrode layer. Gasket The polymer electrolyte membrane, the cathode catalyst layer, the anode catalyst layer, the first catalyst layer, and the first catalyst layer so as to be substantially equal to the thickness of the electrolyte membrane-electrode assembly at the site where the second gasket layer does not overlap the layer. An electrolyte membrane-electrode assembly in which one or two or more thicknesses selected from the group consisting of the gasket layer and the second gasket layer are formed thinner than the other portions of the overlap portion. Is also achieved.

  According to the present invention, an electrolyte membrane capable of effectively preventing / suppressing the decomposition of the electrolyte membrane at the time of holding the OCV while minimizing the occurrence of problems such as an increase in volume and a decrease in power generation performance due to a complicated configuration. -An electrode assembly may be provided.

  The first of the present invention is a polymer electrolyte membrane, a cathode catalyst layer formed on one surface of the polymer electrolyte membrane, an anode catalyst layer formed on the other surface of the polymer electrolyte membrane, A first gasket layer formed on at least a part of an end of the cathode catalyst layer, and an electrolyte membrane-electrode assembly at an overlapping portion of the cathode catalyst layer and the first gasket layer. The polymer electrolyte membrane, the thickness is substantially equal to the thickness of the electrolyte membrane-electrode assembly where the first gasket layer does not overlap the cathode catalyst layer and the first gasket layer. One or two or more thicknesses selected from the group consisting of the cathode catalyst layer, the anode catalyst layer, and the first gasket layer are formed to be thinner than the other portions of the overlap portion. Electrolytes - an electrode assembly.

  First, an electrolyte membrane-electrode assembly (hereinafter also simply referred to as “MEA”) according to the present invention includes a polymer electrolyte membrane and a cathode catalyst formed on one surface of the membrane, similarly to a conventional MEA. And the anode catalyst layer formed on the other surface, characterized in that a first gasket layer is formed on at least a part of the end of the cathode catalyst layer. Due to the presence of such a gasket layer, there is no cathode catalyst layer at which oxygen cross-leak from the cathode side is particularly noticeable, or such a cathode catalyst layer region can be significantly reduced. Therefore, the MEA of the present invention has a structure in which there is little or no periphery where only the cathode catalyst layer exists, and little or no oxygen cross-leak from the cathode to the anode at the end of the cathode catalyst layer occurs. be able to. Therefore, deterioration of the electrolyte membrane, which has been a serious problem in the past, can be effectively prevented / suppressed. Therefore, the fuel cell using the electrolyte membrane-electrode assembly of the present invention can maintain the performance during OCV for a long period of time, and can improve fuel efficiency. In the present specification, the gasket layer formed at the end of the cathode catalyst layer is simply referred to as “first gasket layer”. Here, “form a gasket layer at the end of the catalyst layer” means that the catalyst layer and the gasket layer overlap in the thickness direction of the joined body.

  The MEA of the present invention is the first gasket layer in which the thickness of the electrolyte membrane-electrode assembly at the overlapping portion of the cathode catalyst layer and the first gasket layer is such that the cathode catalyst layer and the first gasket layer do not overlap. 1 type or 2 types selected from the group which consists of a polymer electrolyte membrane, a cathode catalyst layer, an anode catalyst layer, and a 1st gasket layer so that it may become substantially equal to the thickness of the electrolyte membrane electrode assembly of the presence site of The above thickness is also characterized in that the overlapping part is formed thinner than its own other part. According to such a configuration, the thickness of the MEA in the surface direction can be made uniform, and an increase in volume due to the complicated configuration such as the arrangement of the gasket layer can be suppressed. Moreover, the smoothness fall of the catalyst layer etc. of MEA is suppressed and the fall of the power generation performance accompanying this can also be suppressed to the minimum. A specific configuration for realizing such a form will be described later.

  In the MEA of the present invention, as shown in FIG. 5 and subsequent drawings, it is preferable to further form a gasket layer on at least a part of the end portion on the anode catalyst layer side. Thus, by forming the gasket layer also at the end on the anode catalyst layer side, the cross leak gas in the MEA can be more reliably reduced, and the production of hydrogen peroxide can be suppressed. Thereby, deterioration of the electrolyte component contained in the polymer electrolyte membrane and the catalyst layer due to hydrogen peroxide can be prevented / suppressed to a higher degree, and the fuel cell using such an MEA can be used during start / stop / continuous operation and The performance at the time of OCV can be maintained for a longer period of time, the durability is excellent, and the fuel consumption can be further improved. In the present specification, the gasket layer formed at the end of the anode catalyst layer is simply referred to as “second gasket layer”. However, the technical scope of the present invention is not limited only to the form in which the second gasket layer is formed at the end portion of the anode catalyst layer. A form in which the second gasket layer is formed so as not to overlap with the catalyst layer (around the anode catalyst layer) can also be adopted.

  When the second gasket layer is disposed at the end of the anode catalyst layer as described above, the anode catalyst layer and the second gasket layer are separated from the same idea as described above for the first gasket layer. The thickness of the electrolyte membrane-electrode assembly at the overlapping site is substantially equal to the thickness of the electrolyte membrane-electrode assembly at the site of the second gasket layer where the anode catalyst layer and the second gasket layer do not overlap. One or two or more thicknesses selected from the group consisting of a polymer electrolyte membrane, a cathode catalyst layer, an anode catalyst layer, a first gasket layer, and the second gasket layer may have other thicknesses in the overlapping portion. It is good to form thinner than this part. That is, the second of the present invention is a polymer electrolyte membrane, a cathode catalyst layer formed on one surface of the polymer electrolyte membrane, and an anode catalyst formed on the other surface of the polymer electrolyte membrane. A first gasket layer formed on at least a part of the end of the cathode catalyst layer, and a second gasket layer formed on at least a part of the end of the anode catalyst layer. The presence of the first gasket layer is such that the thickness of the electrolyte membrane-electrode assembly at the overlapping portion of the cathode catalyst layer and the first gasket layer does not overlap the cathode catalyst layer and the first gasket layer. And the thickness of the electrolyte membrane-electrode assembly at the overlapping portion of the anode catalyst layer and the second gasket layer is substantially equal to the thickness of the electrolyte membrane-electrode assembly at the site. Said second The polymer electrolyte membrane, the cathode catalyst layer, the anode catalyst layer, and the first catalyst so as to be substantially equal to the thickness of the electrolyte membrane-electrode assembly where the second gasket layer does not overlap with the sket layer. 1 or 2 or more types of thickness selected from the group which consists of said gasket layer and said 2nd gasket layer are formed thinner than the other site | part in the said overlap part, Electrolyte membrane-electrode joining Is the body. According to such a form, the thickness of the MEA in the surface direction can be made uniform in the same manner as described above, and an increase in volume due to the complicated configuration such as the arrangement of the gasket layer can be suppressed. Moreover, the smoothness fall of the catalyst layer etc. of MEA is suppressed and the fall of the power generation performance accompanying this can also be suppressed to the minimum. A specific configuration for realizing such a configuration will also be described later.

  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 solid polymer electrolyte as that used for the electrode catalyst layer described later. 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 Solid polymer electrolyte membranes that are generally commercially available, such as fluorine-based polymer electrolytes such as resin membranes based on styrene and hydrocarbon-based resin membranes having sulfonic acid groups, can be used. Further, a porous thin film formed of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), or the like may be used in which an electrolyte component such as phosphoric acid or ionic liquid is impregnated. 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.

Here, the area of each catalyst layer formed on each side of the polymer electrolyte membrane is not particularly limited. However, in the conventional polymer electrolyte fuel cell, if the operation is stopped and left for several hours or more, air is mixed into the catalyst layer. When activated in such a state, a local battery is formed from the upstream (hydrogen supply side) to the downstream (air atmosphere) of the anode, as shown by the change from the front stage to the rear stage in FIG. Then, when such a local battery is formed in a state where the anode catalyst layer and the cathode catalyst layer are not completely coincided with each other in 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). 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) as compared with the region where the anode is present (center portion). ⁺⁺ 4e ⁻ ) occurs, and the catalytic activity is significantly reduced (see FIG. 3).

  In the MEA of the present invention, each catalyst layer is preferably formed such that the area of the effective anode catalyst layer is larger than the area of the effective cathode catalyst layer. According to such a configuration, the area of the cathode catalyst layer region facing the air existing portion downstream of the anode can be reduced, that is, the portion where the difference between the cathode potential and the electrolyte potential is large can be significantly reduced. It is also possible to obtain the advantage of effectively preventing / suppressing the corrosion of carbon.

  At this time, the positional relationship between the effective anode effective catalyst layer and the effective cathode catalyst layer is not particularly limited. However, as shown in FIG. 4A, the effective cathode catalyst layer in the effective anode catalyst layer with respect to the thickness direction of the MEA. In which the effective cathode catalyst layer is partially included in the effective anode catalyst layer with respect to the thickness direction of the MEA as shown in FIG. 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. 4A; 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. 4B; 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 completely within the anode catalyst layer. It is more preferable that the cathode catalyst layer is completely contained in the anode catalyst layer. In the present specification, the area means a geometric area and does not mean a surface area of a catalyst or the like.

In the present specification, the “effective anode catalyst layer” means a region in the anode catalyst layer where a reaction of 2H ₂ → 4H ⁺ + 4e ⁻ occurs during operation (power generation), and specifically, overlaps with the gasket layer. The anode catalyst layer region, which is simply referred to as the “anode catalyst layer” means all anode catalyst layers formed on the polymer electrolyte membrane, that is, in addition to the effective anode catalyst layer, It also includes an overlap with the second gasket layer.

Further, in this specification, the “effective cathode catalyst layer” means a region in the cathode catalyst layer where O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O reaction occurs during operation (power generation), specifically, The cathode catalyst layer region that does not overlap with the gasket layer, and simply referred to as “cathode catalyst layer” means all cathode catalyst layers formed on the polymer electrolyte membrane, in addition to the effective cathode catalyst layer. And an overlapping portion with the first gasket layer. Therefore, when the end portion of the anode catalyst layer and the second gasket layer do not overlap, the “area of the anode catalyst layer” and the “area of the effective anode catalyst layer” are equal.

  In the present invention, the positional relationship between the end portion of the cathode catalyst layer and the first gasket layer is not particularly limited as long as the permeation of gas at the end portion of the cathode catalyst layer can be sufficiently suppressed. For example, the end of the cathode catalyst layer may be covered with a first gasket layer (the form shown in FIG. 5), or the end of the first gasket layer may be covered with a cathode catalyst layer (see FIG. 6). Form shown). According to the form shown in FIG. 5, the MEA can be manufactured more easily. However, from the viewpoint of more reliably preventing the occurrence of a short circuit due to the end portion of the catalyst layer biting into the polymer electrolyte membrane, more preferably, the first gasket layer is a cathode catalyst layer as shown in FIG. A first gasket layer is formed so as to be covered by the ends of the first gasket layer. In the present invention, the first gasket layer is formed so as to cover at least a part of the peripheral portion of the electrolyte membrane. From the viewpoint of improving fuel consumption accompanying suppression of hydrogen cross-leakage at the end of the anode catalyst layer. Therefore, it is preferable that the gas sealability of the peripheral portion is maintained, and therefore the first gasket layer is preferably formed in a frame shape over the entire peripheral portion of the electrolyte membrane.

  In the present invention, it is essential to form the first gasket layer at the end of the cathode catalyst layer, but it is preferable that a gasket layer is further formed at the end of the anode catalyst layer. That's right. Thus, by forming a gasket layer also at the end on the anode catalyst layer side, the effective cathode catalyst layer and the effective anode catalyst layer can be accurately and easily aligned, and the cathode during start / stop / continuous operation can be obtained. This is because corrosion of the carbon support of the catalyst and decomposition of the electrolyte membrane during OCV retention 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”.

  The positional relationship between the end portion of the anode catalyst layer and the second gasket layer is not particularly limited as long as the permeation of gas at the end portion of the anode catalyst layer can be sufficiently suppressed. For example, the end of the anode catalyst layer may be covered with the second gasket layer (the form shown in FIG. 5), or the end of the second gasket layer may be covered with the anode catalyst layer (see FIG. 6). Form shown). According to the form shown in FIG. 5, the MEA can be manufactured more easily. However, from the viewpoint of more reliably preventing the occurrence of a short circuit due to the end of the catalyst layer biting into the polymer electrolyte membrane, more preferably, the second gasket layer is an anode catalyst layer as shown in FIG. A second gasket layer is formed so as to be covered by the ends of the first gasket layer. In the present invention, the second gasket layer is formed so as to cover at least a part of the periphery of the electrolyte membrane. From the viewpoint of improving the fuel consumption accompanying the suppression of hydrogen cross-leak at the end of the anode catalyst layer. Therefore, it is preferable that the gas sealability of the peripheral part is maintained, and therefore the second gasket layer is preferably formed in a frame shape over the entire peripheral part of the electrolyte membrane.

  In the MEA of the present invention, as described above, the thickness of the electrolyte membrane-electrode assembly at the overlapping portion of the cathode catalyst layer and the first gasket layer is such that the cathode catalyst layer and the first gasket layer do not overlap. One type selected from the group consisting of a polymer electrolyte membrane, a cathode catalyst layer, an anode catalyst layer, and a first gasket layer so as to be approximately equal to the thickness of the electrolyte membrane-electrode assembly at the site where the gasket layer is present Alternatively, it is characterized in that two or more kinds of thicknesses are formed thinner than other portions of the overlapping portion. Further, in a more preferable embodiment, the same device is applied to the overlapping portion between the anode catalyst layer and the second gasket layer. Hereinafter, the characteristic configuration of the present invention will be described with reference to the drawings, taking as an example a form in which the second gasket layer is disposed in addition to the first gasket layer. It goes without saying that the technical scope of the present invention is not limited to only the MEA to be used. In the following drawings, each component is illustrated in a separated form for the sake of simplification. Needless to say, each component is joined in the thickness direction of the MEA in the completed MEA. .

  A preferred form of the MEA of the present invention is the form shown in FIG. In the MEA of the form shown in FIG. 5, the first gasket layer is composed of a first gas impermeable layer and a first adhesive layer, and the thickness of the first gas impermeable layer is the cathode. The overlapping part with the catalyst layer is formed thinner than the other part of itself, and the second gasket layer comprises a second gas-impermeable layer and a second adhesive layer, The thickness of the second gas-impermeable layer is formed to be thinner than the other portions in the overlapping portion with the anode catalyst layer. Thereby, in the MEA, the thickness of the overlapping portion between the cathode catalyst layer and the first gasket layer and the thickness of the overlapping portion between the anode catalyst layer and the second gasket layer are substantially equal to the thickness of the non-overlapping portion. Yes.

  In the embodiment shown in FIG. 5, the end of the cathode catalyst layer is covered with the first gasket layer, and the end of the anode catalyst layer is covered with the second gasket layer. As described above, the end of the first gasket layer may be covered with the cathode catalyst layer, and the end of the second gasket layer may be covered with the anode catalyst layer as described above. The same applies to other preferable modes described later.

  Another preferred form of the MEA of the present invention is the form shown in FIG. In the MEA of the form shown in FIG. 7, the first gasket layer is composed of a first gas impermeable layer and a first adhesive layer, and the thickness of the first gas impermeable layer is the cathode catalyst. The second gasket layer is formed of a second gas-impermeable layer and a second adhesive layer. In addition, the thickness of the second gas impermeable layer is formed so as to continuously decrease from the non-overlap portion with the anode catalyst layer toward the overlap portion. As a result, in the MEA, the difference between the thickness of the overlapping portion of the cathode catalyst layer and the first gasket layer and the thickness of the overlapping portion of the anode catalyst layer and the second gasket layer and the thickness of the non-overlapping portion are reduced. Yes.

  As still another preferred form of the MEA of the present invention, there is a form shown in FIG. In the MEA shown in FIG. 8, the first gasket layer is composed of a first gas-impermeable layer and a first adhesive layer, and the thickness of the first adhesive layer is the cathode catalyst. The second gasket layer is composed of a second gas-impermeable layer and a second adhesive layer, and the second gasket layer is formed thinner than the other portions of the layer. The thickness of the adhesive layer is formed to be thinner than the other portions in the overlapping portion with the anode catalyst layer. Thereby, in the MEA, the thickness of the overlapping portion between the cathode catalyst layer and the first gasket layer and the thickness of the overlapping portion between the anode catalyst layer and the second gasket layer are substantially equal to the thickness of the non-overlapping portion. Yes.

  Still another preferred form of the MEA of the present invention is the form shown in FIG. In the MEA of the form shown in FIG. 9, the thickness of the cathode catalyst layer is formed thinner than the other portions of the cathode catalyst layer at the overlapping portion with the first gasket layer, and the thickness of the anode catalyst layer is It is formed thinner than the other part of itself at the overlapping part with the second gasket layer. Thereby, in the MEA, the thickness of the overlapping portion between the cathode catalyst layer and the first gasket layer and the thickness of the overlapping portion between the anode catalyst layer and the second gasket layer are substantially equal to the thickness of the non-overlapping portion. Yes.

  Still another preferred form of the MEA of the present invention is the form shown in FIG. In the MEA in the form shown in FIG. 10, the thickness of the polymer electrolyte membrane is formed thinner than the other portions of the polymer electrolyte membrane at the overlapping portion with the first gasket layer, and the thickness of the polymer electrolyte membrane is In the overlapping part with the second gasket layer, it is formed thinner than the other part of itself. Thereby, in the MEA, the thickness of the overlapping portion between the cathode catalyst layer and the first gasket layer and the thickness of the overlapping portion between the anode catalyst layer and the second gasket layer are substantially equal to the thickness of the non-overlapping portion. Yes.

  The combination of forming the first and second gasket layers is not particularly limited and may be any combination. Preferably, (1) the first gasket layer is formed between the cathode catalyst layer and the polymer electrolyte membrane so that the first gasket layer is covered with the end of the cathode catalyst layer, and the second gasket layer is the anode catalyst layer. Formed between the anode catalyst layer and the polymer electrolyte membrane to be coated at the end; (2) a first gasket layer is formed to cover the end of the cathode catalyst layer; And (3) a cathode catalyst layer and a polymer electrolyte membrane so that the first gasket layer is covered with the end of the cathode catalyst layer. And the second gasket layer is formed so as to cover the end of the anode catalyst layer. Among the above combinations, in the sense that the short circuit (contact between the anode / cathode catalyst layers) can be effectively prevented and the corrosion of carbon hardly occurs, the anode catalyst layer and / or the cathode catalyst layer and the electrolyte membrane may be It is preferable that at least one of the first or second gasket layer is inserted. In this respect, the combination of (1) and (3) is preferable. Moreover, although the effect of suppressing the corrosion of carbon is somewhat inferior, the combination of the above (2) is preferably used in terms of easy production.

  In the present invention, the effective anode catalyst layer and the effective cathode catalyst layer can be easily formed by forming the first gasket layer at the end of the cathode catalyst layer, and preferably the second gasket layer at the end of the anode catalyst layer. Can be adjusted accurately 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 cathode catalyst layer and the end portion of the anode catalyst layer may be terminated at substantially the same position in the thickness direction of the electrolyte membrane-electrode assembly. The positions of the end portions of the anode catalyst layer may be different. 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, the end portion of the anode catalyst layer is preferably terminated beyond the end portion of the cathode catalyst layer in the thickness direction of the electrolyte membrane-electrode assembly. As described above, in the present invention, it is essential that the area of the effective anode catalyst layer is larger than the area of the effective cathode catalyst layer, and thus the cathode catalyst layer is previously made smaller than the size of the anode catalyst layer. Thus, the amount of catalyst and electrolyte to be used can be reduced, and the overlap with the gasket layer portion can be reduced, which is economically preferable.

  While the preferred embodiments of the MEA of the present invention have been described above with reference to the drawings, it goes without saying that the specific features shown in the drawings may be used in combination in implementing the present invention. There are no particular limitations on the specific examples of the combination at that time, and any combination can be adopted as long as the effects of the present invention are not lost.

  The electrolyte membrane-electrode assembly of the present invention can be produced in the same manner as a known method or by using a suitably modified method. Specifically, on the polymer electrolyte membrane, a cathode catalyst layer, an anode catalyst layer, a first gasket layer, and, if necessary, a second gasket layer are arranged in an appropriate arrangement, for example, the arrangement described above. A sequential forming method can be used. At this time, if necessary, a desired component may be processed to have a desired thickness and used for manufacturing the MEA. There is no restriction | limiting in particular about the processing technique which makes a part of each component thin, A conventionally well-known knowledge can be referred suitably. As an example of such processing technology, for example, for polymer materials such as electrolyte membranes and gasket layers, there are techniques such as hot pressing and cold pressing, and techniques such as casting, but other techniques are used. Of course, it is good. As for the catalyst layer, a desired thickness is obtained by a method such as reducing the coating amount of the portion to be thinly processed from other portions by a technique such as a die coater method, a spray coating method, or a transfer method.

  Therefore, the MEA of the present invention uses, for example, a polymer electrolyte membrane, a catalyst layer, a gasket layer, etc., at the end of one surface of the polymer electrolyte membrane using a component processed to a desired size. A first gasket layer formed by forming a first adhesive layer on the first gas-impermeable layer so that the first adhesive layer and the polymer electrolyte membrane face each other; A second gasket layer formed by forming a second adhesive layer on a second gas impermeable layer is formed at the end of the other surface of the molecular electrolyte membrane, and the second adhesive layer and the polymer electrolyte. An arrangement step of forming a laminate by placing the membranes facing each other; pressing the laminate to bond the first gasket layer and the second gasket layer to the polymer electrolyte membrane Bonding step; and the first gasket layer A catalyst layer forming step of forming a cathode catalyst layer so as to cover an inner end portion and forming an anode catalyst layer so as to cover an inner end portion of the second gasket layer, and And the second gasket layer are bonded so that the area of the effective anode catalyst layer is larger than the area of the effective cathode catalyst layer (hereinafter referred to as “first manufacturing method”). Can be manufactured).

  In the MEA of the present invention, the catalyst layer forming step of forming the cathode catalyst layer and the anode catalyst layer on the respective surfaces of the polymer electrolyte membrane; the first gas-impermeable layer has the first adhesive layer The formed first gasket layer is formed such that the first adhesive layer and the polymer electrolyte membrane face each other, and an end portion of the cathode catalyst layer is covered with the first adhesive layer. A second gasket layer formed by forming a second adhesive layer on the second gasket layer body, the second adhesive layer and the polymer electrolyte membrane facing each other, and the anode catalyst layer An arrangement step of forming a laminate by arranging an end of the second anode adhesive layer so that the area of the effective anode catalyst layer is larger than the area of the effective cathode catalyst layer; and Press the laminate And a bonding process for bonding the first gasket layer and the second gasket layer to the polymer electrolyte membrane, by a MEA manufacturing method (hereinafter also referred to as “second manufacturing method”). Can be manufactured.

  Furthermore, the MEA of the present invention has a first gasket layer formed by forming a first adhesive layer on a first gas impermeable layer at an end of one surface of the polymer electrolyte membrane. A cathode catalyst layer forming step of forming a cathode catalyst layer so as to cover an inner end portion of the first gasket layer after disposing the adhesive layer and the polymer electrolyte membrane so as to face each other; After forming the anode catalyst layer on the other surface of the membrane, the second gasket layer formed by forming the second adhesive layer on the second gas-impermeable layer is connected to the second adhesive layer and the high-pressure layer. It is arranged so that the molecular electrolyte membrane faces and the end of the anode catalyst layer is covered with the second adhesive layer, and the area of the effective anode catalyst layer is larger than the area of the effective cathode catalyst layer. , Anode catalyst layer forming work to form a laminate And a bonding step of bonding the first gasket layer and the second gasket layer to the polymer electrolyte membrane by pressing the laminate, and a MEA manufacturing method (hereinafter referred to as “first” The third manufacturing method ”is also referred to.

  According to the method of the present invention, the cathode catalyst layer, the first gasket layer, the anode catalyst layer, and, if necessary, the second gasket layer can be accurately and easily arranged in a desired order. In addition, by disposing the first gasket layer and the second gasket layer at the ends of the cathode catalyst layer and the anode catalyst layer, respectively, the effective cathode catalyst layer and the effective anode catalyst layer can be accurately adjusted to have desired areas. Can be specified.

  In the method of the present invention, the first gasket layer is formed at the end of the cathode catalyst layer, and preferably the second gasket layer is formed at the end of the anode catalyst layer, so that the alignment of each catalyst layer needs to be accurate. Is not necessarily. That is, the end of the cathode catalyst layer and the end of the anode catalyst layer may terminate at substantially the same position in the thickness direction of the electrolyte membrane-electrode assembly. The position of the end of the anode catalyst layer 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. At this time, the end of the anode catalyst layer is preferably terminated beyond the end of the cathode catalyst layer with respect to the thickness direction of the electrolyte membrane-electrode assembly. As described above, in the present invention, it is essential that the area of the effective anode catalyst layer is larger than the area of the effective cathode catalyst layer, and thus the cathode catalyst layer is previously made smaller than the size of the anode catalyst layer. Thus, the amount of catalyst and electrolyte to be used can be reduced, and the overlap with the gasket layer portion can be reduced, which is economically preferable.

  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. 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. 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 for 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 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 size of the catalyst particles used in the catalyst ink, the higher the effective electrode area where the electrochemical reaction proceeds, and thus the higher the oxygen reduction activity. On the other hand, a phenomenon in which the oxygen reduction activity decreases is observed. Therefore, the average particle diameter of the catalyst particles contained in the catalyst 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.

  In the present invention, the catalyst particles described above are included in the catalyst ink as an electrode catalyst supported on a conductive carrier.

  The conductive carrier may have any specific surface area for supporting the catalyst particles in a desired dispersed state and has sufficient electronic conductivity as a current collector. The main component is carbon. Preferably there is. 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 cathode catalyst layer / anode catalyst layer (hereinafter also simply referred to as “catalyst layer”) of the present invention contains a polymer electrolyte in addition to 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. 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.

  Since the solid polymer electrolyte is excellent in heat resistance, chemical stability, etc., it preferably contains a fluorine atom. Among them, Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Corporation) ) And Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.).

  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.

  In the method of the present invention, the catalyst ink comprising the electrode catalyst, the solid polymer electrolyte and the solvent as described above is applied to the surface of the polymer electrolyte membrane (or the surface of the polymer electrolyte membrane with the gasket layer partially covered). The catalyst layer is formed by applying to the catalyst. In this case, the solvent 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. Also, the amount of solvent used is not particularly limited, and the same amount as known can be used. In the catalyst ink, the electrode catalyst has a desired action, that is, hydrogen oxidation reaction (anode side) and oxygen reduction reaction. Any amount may be used as long as it can sufficiently exert the action of catalyzing (cathode side). It is preferable that the electrode catalyst is present in the catalyst ink in an amount of 5 to 30% by mass, more preferably 9 to 20% by mass.

  The catalyst ink of 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. Examples thereof include glycerin, ethylene glycol (EG), polyvinyl alcohol (PVA), and propylene glycol (PG). The amount of the thickener added when the thickener is used is not particularly limited as long as it does not interfere with the above effect of the present invention, but is preferably 5 to 20 with respect to the total mass of the catalyst ink. % By mass.

  The catalyst ink of the present invention is not particularly limited in its preparation method as long as an electrode catalyst, an electrolyte and a solvent, and if necessary, a water-repellent polymer and / or a thickener are appropriately mixed. For example, a catalyst ink can be prepared by adding an electrolyte to a polar solvent, heating and stirring the mixed solution to dissolve the electrolyte in the polar solvent, and then adding an electrode catalyst thereto. Alternatively, after the electrolyte is once dispersed / suspended in a solvent, the dispersion / suspension may be mixed with an electrode catalyst to prepare a catalyst ink. In addition, a commercially available electrolyte solution (for example, DuPont Nafion solution: Nafion dispersed / suspended at a concentration of 5 wt% in 1-propanol) in which the electrolyte is previously prepared in the above other solvent is used as it is. May be used in the method.

  Each catalyst layer is formed by applying the catalyst ink as described above on the polymer electrolyte membrane or on the polymer electrolyte membrane while covering a part of the gasket layer. At this time, the conditions for forming the cathode / anode catalyst layer on the polymer electrolyte membrane are not particularly limited, and can be used in the same manner as known methods or appropriately modified. For example, the catalyst ink is applied onto the polymer electrolyte membrane so that the thickness after drying is 5 to 20 μm, 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 a catalyst layer is not enough, the said application | coating and drying process is repeated until it becomes desired thickness.

  In the present invention, the gasket layer may be impermeable to gas, particularly oxygen or hydrogen gas. In general, the gasket layer is bonded to the end of the polymer electrolyte membrane or the cathode / anode catalyst layer. It is composed of a target adhesive layer and an impermeable layer made of a gas impermeable material. At this time, the material constituting the impermeable layer is not particularly limited as long as it is impermeable to oxygen and hydrogen gas when formed into a film. Specific examples include polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), (polyvinylidene fluoride (PVDF), etc. In addition, materials that can be used for the adhesive layer are also high. There is no particular limitation as long as the molecular electrolyte 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 adhesive, polyester, polyolefin Olefin adhesives such as can be used.

  The formation method in particular of a gasket layer is not restrict | limited, A well-known method can be used. For example, after applying the adhesive to a thickness of 5 to 30 μm on the polymer electrolyte membrane or on the polymer electrolyte membrane while covering the end portion of the catalyst layer, the gas non-existence as described above is applied. A method can be used in which a transparent material is applied to a thickness of 10 to 200 μm and cured by heating at 25 to 150 ° C. for 10 seconds to 10 minutes. Alternatively, after a gas-impermeable material is formed into a sheet in advance, an adhesive is applied to the impermeable film to form a gasket layer, which is then applied to the polymer electrolyte membrane or a part of the gasket layer. It may be bonded onto the polymer electrolyte membrane while coating. At this time, the thickness of the impermeable layer is not particularly limited, but is preferably 15 to 40 μm, and the adhesive layer is also not particularly limited, but is preferably 10 to 25 μm.

  In the above description, the method for directly forming the anode / cathode catalyst layer or the gasket layer on the polymer electrolyte membrane by direct application has been described. However, the MEA of the present invention can be obtained by other methods such as a transfer method. May be manufactured. The production method 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, the catalyst ink as prepared above is applied and dried on a transfer mount to form an electrode 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). In the above process, the thickness of the electrode catalyst layer is not particularly limited as long as it can sufficiently exhibit the catalytic action of the hydrogen oxidation reaction (anode side) and the oxygen reduction reaction (cathode side). Thickness can be used. Specifically, the thickness of the electrode catalyst layer is 1 to 30 μm, more preferably 1 to 20 μm. 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. Also, the drying conditions of the applied electrode catalyst layer are not particularly limited as long as the polar solvent can be completely removed from the electrode catalyst layer. Specifically, the catalyst ink coating layer (electrode catalyst layer) is dried in a vacuum dryer at room temperature to 100 ° C., more preferably 50 to 80 ° C., for 30 to 60 minutes. 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 thus produced, 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 MEA composed of the electrode catalyst layer and the polymer electrolyte membrane can be obtained by removing the transfer mount.

  Note that the MEA according to the present invention may generally further include a gas diffusion layer, as will be described in detail below. In this case, the gas diffusion layer is obtained by peeling off the transfer mount in the above method. It is preferable that the joined body is further sandwiched between gas diffusion layers to further join each electrode catalyst layer after joining the electrode catalyst layer and the polymer electrolyte membrane. Alternatively, after an electrode catalyst layer is formed on the surface of the gas diffusion layer in advance to produce an electrode catalyst layer-gas diffusion layer assembly, the electrode catalyst layer-gas diffusion layer assembly is used in the same manner as described above. It is also preferable to sandwich and bond the molecular electrolyte membrane by hot pressing.

  At this time, the gas diffusion layer used in the MEA is not particularly limited, and a known one can be used in the same manner. For example, the conductive and porous properties such as carbon woven fabric, paper-like paper body, felt, and non-woven fabric are used. The thing which uses the sheet-like material which has 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.

  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. 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.

  When the MEA of the present invention has the gas diffusion layer as described above, the thickness of the MEA can be made uniform as described above also by controlling the thickness of the gas diffusion layer. Specifically, the form shown in FIG. 11 is illustrated. The MEA shown in FIG. 11 has a gas diffusion layer (hereinafter referred to as “first gas diffusion layer”) adjacent to the cathode catalyst layer and the first gasket layer of the electrolyte membrane-electrode assembly shown in FIG. Also, a gas diffusion layer (hereinafter also referred to as “second gas diffusion layer”) is disposed adjacent to the anode catalyst layer and the second gasket layer. And the thickness of the first gas diffusion layer is formed thinner than the other portions of the first gas diffusion layer at the overlapping portion with the first gasket layer, and the thickness of the second gas diffusion layer is the second In the overlapping part with the gasket layer, it is formed thinner than the other part of itself. Thereby, in the MEA, the thickness of the overlapping portion between the cathode catalyst layer and the first gasket layer and the thickness of the overlapping portion between the anode catalyst layer and the second gasket layer are substantially equal to the thickness of the non-overlapping portion. Yes.

  However, it is also possible to obtain the same effect only by controlling the thickness of the gas diffusion layer using a laminate in which the thicknesses of the polymer electrolyte membrane, catalyst layer, and gasket layer constituting the MEA are not controlled. is there. In such a form, a gas diffusion layer in which the thickness of the portion corresponding to the overlapping portion of the catalyst layer and the gasket layer is reduced may be employed.

  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.

  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 forming a carbon particle layer on a substrate in a gas diffusion layer, the carbon particles, water repellent, etc. are in a solvent such as water, alcohol solvents such as perfluorobenzene, dichloropentafluoropropane, methanol, ethanol, etc. A slurry is prepared by dispersing in a slurry, and the slurry is applied on a substrate and dried, or the slurry is dried and pulverized to form a powder, and this is applied to the gas diffusion layer. Use it. Then, it is preferable to heat-process at about 250-400 degreeC using a muffle furnace or a baking furnace.

  When such a carbon layer is arranged in the gas diffusion layer, the thickness of the MEA can be made uniform as described above by controlling the thickness of the carbon layer. Specifically, the form shown in FIG. 12 is illustrated. The MEA in the form shown in FIG. 12 has a carbon layer (first carbon layer) so as to be adjacent to the cathode catalyst layer and the first gasket layer of the electrolyte membrane-electrode assembly in the form shown in FIG. The second gas diffusion layer having a carbon layer (second carbon layer) is disposed adjacent to the anode catalyst layer and the second gasket layer. And the thickness of the first carbon layer is formed thinner than the other part of itself at the overlapping part with the first gasket layer, and the thickness of the second carbon layer is the second gasket layer Is formed thinner than the other parts of itself. Thereby, in the MEA, the thickness of the overlapping portion between the cathode catalyst layer and the first gasket layer and the thickness of the overlapping portion between the anode catalyst layer and the second gasket layer are substantially equal to the thickness of the non-overlapping portion. Yes.

  In addition, although it demonstrated in detail taking the example which controls the thickness of a carbon layer in the conventional gas diffusion layer by which a carbon layer is arrange | positioned at a porous sheet here, it is not restrict | limited only to such a form. . Accordingly, the gas diffusion layer is composed of a plurality of gas diffusion layers having different gas diffusivities, and at least one of the plurality of gas diffusion layers is formed to be thinner at least at the overlapping portion than the other portions. Any form is included in the technical scope of the present invention. At this time, it is preferable to reduce the thickness of the layer having a smaller gas permeability among the plurality of layers constituting the gas diffusion layer because the manufacturing is simple. In general, it is effective to dispose a layer having a lower gas permeability on the catalyst layer side in order to quickly discharge moisture generated by the electrochemical reaction to the separator flow path. A gas diffusion layer having a relatively high permeability often comes into contact with the fuel cell separator. In the manufacturing process, the gas diffusion layer having a low gas permeability is often formed in a subsequent step by using a gas diffusion layer having a high gas permeability as a base material by a transfer method, a die coater method, a spray coating method, or the like. According to these methods, the thickness can be easily controlled. For example, referring to FIG. 12, the gas diffusion layer has a carbon layer in addition to the main layer of the gas diffusion layer, but the carbon layer has a lower gas permeability than the main layer of the gas diffusion layer, The thickness of the carbon layer having a smaller gas permeability is controlled.

  In addition, the gas permeability in a gas diffusion layer means the flow volume of the gas which permeate | transmits a gas diffusion layer. A layer with a large flow rate of permeating gas has a high gas permeation performance, and a layer with a small flow rate of permeating gas has a low gas permeation performance. Gas permeability correlates with the size of pores in the gas diffusion layer. A layer having a high gas permeability generally has a large pore diameter, and a layer having a low gas permeability generally has a small pore diameter. When the gas diffusion layer is composed of a plurality of layers, the gas permeability of each layer can be measured by a Gurley method, a Darcy method, or the like.

  According to the electrolyte membrane-electrode assembly of the present invention, as described above, the deterioration of the electrolyte component contained in the electrolyte membrane-electrode assembly is suppressed, and preferably the corrosion of the carbon support used as the catalyst support is also suppressed. sell. 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. This is highly desirable. Further, the thickness of each component is controlled at the overlapping portion of the catalyst layer and the gasket layer. Thus, the MEA thickness uniformity can be improved, and an MEA capable of minimizing an increase in the volume of cells and stacks and a decrease in power generation performance caused by the complicated configuration of the MEA is provided. Is possible. Therefore, by using such an electrolyte membrane-electrode assembly, it is possible to provide a highly reliable polymer electrolyte fuel cell that is easy to manufacture, can be miniaturized, and has excellent power generation performance. it can. 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, but other than that, typical examples are an alkaline fuel cell and a phosphoric acid fuel cell. 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 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 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.

  In order to prevent the gas supplied to each catalyst layer from leaking to the outside, a gas seal portion may be further provided 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), and polyisobutylene rubber, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and polyhexafluoro. Fluorine polymer materials such as propylene, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and thermoplastic resins such as polyolefin and polyester. Further, the thickness of the gas seal portion may be about 50 μm to 2 mm, preferably about 100 μm to 1 mm.

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

  Since the electrolyte membrane-electrode assembly (MEA) of the present invention can be miniaturized and has excellent power generation performance, it can be suitably applied to a fuel cell.

It is explanatory drawing which shows the cross leak of oxygen at the time of OCV holding | maintenance. It is explanatory drawing which shows the gas atmosphere of the anode / cathode after standing for a long time, and the gas atmosphere and local cell state of the anode / cathode at the time of starting after standing for a long time. It is explanatory drawing which shows the electrochemical reaction which arises in a local battery. 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. FIG. 3 is a diagram illustrating a structure of an MEA according to a preferred embodiment of the present invention. FIG. 3 is a diagram showing the structure of an MEA according to another preferred embodiment of the present invention. FIG. 6 is a diagram illustrating a structure of an MEA according to still another preferred embodiment of the present invention. FIG. 6 is a diagram illustrating a structure of an MEA according to still another preferred embodiment of the present invention. FIG. 6 is a diagram illustrating a structure of an MEA according to still another preferred embodiment of the present invention. FIG. 6 is a diagram illustrating a structure of an MEA according to still another preferred embodiment of the present invention. FIG. 6 is a diagram illustrating a structure of an MEA according to still another preferred embodiment of the present invention. FIG. 6 is a diagram illustrating a structure of an MEA according to still another preferred embodiment of the present invention.

Claims (17)

A polymer electrolyte membrane;
A cathode catalyst layer formed on one surface of the polymer electrolyte membrane;
An anode catalyst layer formed on the other surface of the polymer electrolyte membrane;
A first gasket layer formed on at least a part of an end of the cathode catalyst layer;
And the thickness of the electrolyte membrane-electrode assembly in at least the overlapping portion of the cathode catalyst layer and the first gasket layer is such that the cathode catalyst layer and the first gasket layer do not overlap. It is selected from the group consisting of the polymer electrolyte membrane, the cathode catalyst layer, the anode catalyst layer, and the first gasket layer so as to be approximately equal to the thickness of the electrolyte membrane-electrode assembly at the site where the gasket layer is present. An electrolyte membrane-electrode assembly, wherein one or two or more types of thicknesses are formed thinner than the other parts in the overlapping part. A polymer electrolyte membrane;
A cathode catalyst layer formed on one surface of the polymer electrolyte membrane;
An anode catalyst layer formed on the other surface of the polymer electrolyte membrane;
A first gasket layer formed on at least a part of an end of the cathode catalyst layer;
A second gasket layer formed on at least a part of an end of the anode catalyst layer;
And the thickness of the electrolyte membrane-electrode assembly in at least the overlapping portion of the cathode catalyst layer and the first gasket layer is such that the cathode catalyst layer and the first gasket layer do not overlap. The thickness of the electrolyte membrane-electrode assembly at the overlapping portion of the anode catalyst layer and the second gasket layer is substantially equal to the thickness of the electrolyte membrane-electrode assembly at the location where the gasket layer is present. The polymer electrolyte membrane, the cathode catalyst layer, so that the anode catalyst layer and the second gasket layer are substantially equal to the thickness of the electrolyte membrane-electrode assembly where the second gasket layer does not overlap. One or more thicknesses selected from the group consisting of the anode catalyst layer, the first gasket layer, and the second gasket layer are different from each other in the overlapping portion. Formed by formed thinner than position, the electrolyte membrane - electrode assembly. A polymer electrolyte membrane;
A cathode catalyst layer formed on one surface of the polymer electrolyte membrane;
An anode catalyst layer formed on the other surface of the polymer electrolyte membrane;
A first gasket layer formed on at least a part of an end of the cathode catalyst layer;
A first gas diffusion layer disposed adjacent to the cathode catalyst layer and the first gasket layer;
And the thickness of the electrolyte membrane-electrode assembly in at least the overlapping portion of the cathode catalyst layer and the first gasket layer is such that the cathode catalyst layer and the first gasket layer do not overlap. An electrolyte in which the thickness of the first gas diffusion layer is formed to be thinner than the other portions of the first gas diffusion layer so as to be substantially equal to the thickness of the electrolyte membrane-electrode assembly at the portion where the gasket layer is present. Membrane-electrode assembly.   The first gas diffusion layer is composed of a plurality of gas diffusion layers having different gas diffusivities, and the thickness of the gas diffusion layer having a smaller gas permeability among the plurality of gas diffusion layers is at least in the overlapping portion. The electrolyte membrane-electrode assembly according to claim 3, wherein the electrolyte membrane-electrode assembly is formed thinner than other portions. A polymer electrolyte membrane;
A cathode catalyst layer formed on one surface of the polymer electrolyte membrane;
An anode catalyst layer formed on the other surface of the polymer electrolyte membrane;
A first gasket layer formed on at least a part of an end of the cathode catalyst layer;
A first gas diffusion layer disposed adjacent to the cathode catalyst layer and the first gasket layer;
A second gas diffusion layer disposed adjacent to the anode catalyst layer and the second gasket layer;
And the thickness of the electrolyte membrane-electrode assembly at least at the overlapping portion of the anode catalyst layer and the second gasket layer is such that the anode catalyst layer and the second gasket layer do not overlap. An electrolyte in which the thickness of the second gas diffusion layer is formed to be thinner than the other portions of itself in the overlapping portion so as to be substantially equal to the thickness of the electrolyte membrane-electrode assembly in the portion where the gasket layer is present Membrane-electrode assembly.   The second gas diffusion layer is composed of a plurality of gas diffusion layers having different gas diffusivities, and the thickness of the gas diffusion layer having a smaller gas permeability among the plurality of gas diffusion layers constituting the second gas diffusion layer. The electrolyte membrane-electrode assembly according to claim 5, wherein the overlapping portion is formed thinner than the other portion of itself.   The electrolyte membrane-electrode assembly according to any one of claims 1 to 6, wherein the first gasket layer includes a first gas impermeable layer and a first adhesive layer, The thickness of the gas impervious layer is formed thinner than the other part of itself at the overlapping part with the cathode catalyst layer, or the electrolyte membrane-electrode junction according to any one of claims 2 to 6. In the body, the second gasket layer is composed of a second gas impermeable layer and a second adhesive layer, and the thickness of the second gas impermeable layer is determined at the overlapping portion with the anode catalyst layer. An electrolyte membrane-electrode assembly, which is formed thinner than other portions.   The electrolyte membrane-electrode assembly according to any one of claims 1 to 7, wherein the first gasket layer includes a first gas-impermeable layer and a first adhesive layer, 8. The electrolyte membrane-electrode assembly according to claim 2, wherein a thickness of the adhesive layer is formed thinner than other portions of the adhesive layer at an overlapping portion with the cathode catalyst layer. The second gasket layer is composed of a second gas impermeable layer and a second adhesive layer, and the thickness of the second adhesive layer is different from that of the anode catalyst layer at the overlapping portion. An electrolyte membrane-electrode assembly, which is formed thinner than the region.   9. The electrolyte membrane-electrode assembly according to claim 1, wherein the thickness of the cathode catalyst layer is thinner than the other portions of the cathode catalyst layer at the overlapping portion with the first gasket layer. The electrolyte membrane-electrode assembly according to any one of claims 2 to 8, wherein the anode catalyst layer has a thickness other than that of the second gasket layer. An electrolyte membrane-electrode assembly formed thinner than the above.   10. The electrolyte membrane-electrode assembly according to claim 1, wherein the thickness of the polymer electrolyte membrane is thinner than other portions of the polymer electrolyte membrane at the overlapping portion with the first gasket layer. The electrolyte membrane-electrode assembly according to any one of claims 2 to 9, wherein the thickness of the polymer electrolyte membrane is different from the thickness of the polymer electrolyte membrane at the overlapping portion with the second gasket layer. An electrolyte membrane-electrode assembly, which is formed thinner than the region.   The electrolyte membrane according to any one of claims 1 to 10, wherein the cathode catalyst layer and the anode catalyst layer are formed such that an area of the effective anode catalyst layer is larger than an area of the effective cathode catalyst layer. An electrode assembly.   The electrolyte membrane-electrode assembly according to any one of claims 1 to 11, wherein an end of the cathode catalyst layer is covered with the first gasket layer.   The electrolyte membrane-electrode assembly according to any one of claims 1 to 11, wherein an end of the first gasket layer is covered with the cathode catalyst layer.   The electrolyte membrane-electrode assembly according to any one of claims 2 to 13, wherein an end portion of the anode catalyst layer is covered with the second gasket layer.   The electrolyte membrane-electrode assembly according to any one of claims 2 to 13, wherein an end portion of the second gasket layer is covered with the anode catalyst layer.   The edge part of the said cathode catalyst layer and the edge part of the said anode catalyst layer are terminated at the substantially the same position with respect to the thickness direction of an electrolyte membrane electrode assembly, respectively. Electrolyte membrane-electrode assembly.   The electrolyte according to any one of claims 1 to 15, wherein an end of the cathode catalyst layer and an end of the anode catalyst layer terminate at different positions with respect to the thickness direction of the electrolyte membrane-electrode assembly. Membrane-electrode assembly.

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