JP2018160447A - Membrane electrode assembly, electrochemical cell, stack, fuel cell and vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a membrane electrode assembly, an electrochemical cell, a stack, a fuel cell, and a vehicle each with enhanced power generation characteristics.SOLUTION: The membrane electrode assembly of an embodiment includes: a first support; a first electrode having a first catalyst layer including a plurality of first catalyst units having a laminated structure including a void layer on the first support; and an electrolyte membrane in contact with a surface facing the plurality of first catalyst units between the plurality of first catalyst units and in contact with a surface of the first catalyst unit opposite to the first support side. The membrane electrode assembly further includes a portion where the electrolyte membrane is present over at least a region up to 80% of the thickness of the first catalyst layer from the surface of the first catalyst unit in contact with the electrolyte membrane on the side opposite to the first support side toward the first support.SELECTED DRAWING: Figure 1

Description

  Embodiments relate to a membrane electrode assembly, an electrochemical cell, a stack, a fuel cell, and a vehicle.

In recent years, electrochemical cells have been actively studied. Among electrochemical cells, for example, a fuel cell includes a system that generates electricity by electrochemically reacting a fuel such as hydrogen and an oxidant such as oxygen. Among them, a polymer electrolyte fuel cell (PEFC) has been put to practical use as a stationary power source for homes and a power source for automobiles because of its low environmental load. As the catalyst layer included in each PEFC electrode, a carbon-supported catalyst in which a catalyst material is supported on a carbon black carrier is generally used. The carbon support corrodes due to the power generation of the fuel cell, the catalyst layer and the membrane electrode assembly (MEA) including the catalyst layer are greatly deteriorated, and a large amount of catalyst is used to ensure the durability of the fuel cell. Yes. One major issue for the widespread use of PEFC is cost reduction due to a reduction in the amount of noble metal catalyst used.

  In fuel cells, a carrier-less porous catalyst layer has been proposed in order to avoid catalyst deterioration due to the carbon support and to enhance the catalytic activity and electrochemical cell characteristics, ensuring excellent durability and high characteristics even with a small amount of platinum. Yes.

  On the other hand, since the electrolyte membrane used in the electrochemical cell is very expensive, the cost of the membrane / electrode assembly is also very high, and it is generally a big problem of widespread use. Furthermore, in order to improve the performance of the electrochemical cell, the membrane resistance is generally reduced by reducing the thickness of the electrolyte membrane. However, in the electrolyte membrane sandwiched between the electrodes, the mechanical stress due to swelling and shrinkage of the membrane due to fluctuations in the end humidity at the electrode end portion is large between the electrolyte membrane portion outside the electrode and the electrolyte membrane portion sandwiched between the electrodes. It is known that film cracks are likely to occur. As described above, the MEA is still not sufficient, and there is a need for further improvement.

Japanese Patent No. 5342824

  An embodiment is to provide a membrane electrode assembly, an electrochemical cell, a stack, a fuel cell, and a vehicle with improved power generation characteristics.

  The membrane electrode assembly of the embodiment is in contact with a first electrode having a first support, a first catalyst layer including a plurality of catalyst units having a laminated structure including a void layer, and an electrolyte material. The first catalyst layer exists between the first support and the electrolyte membrane, and the gap between the plurality of catalyst units of the first catalyst layer faces the support from the electrolyte membrane side. It includes a portion where the electrolyte material exists over at least 80% of the thickness of the first catalyst layer.

Sectional drawing of the gas diffusion electrode with an electrolyte (layer) which concerns on embodiment. The low magnification transmission type | mold microscope picture of the laminated catalyst cross section which concerns on embodiment. Sectional drawing of the gas diffusion electrode with an electrolyte (layer) which concerns on embodiment. The figure which shows the measurement spot of the electrode which concerns on embodiment. Explanatory drawing of the interface cross section of the gas diffusion electrode with an electrolyte (layer) concerning an embodiment. The chart figure which shows the preparation process which concerns on embodiment. Sectional drawing of the membrane electrode assembly which concerns on embodiment. Sectional drawing of the sub-gasket integrated membrane electrode assembly which concerns on embodiment. Sectional drawing of the electrochemical cell which concerns on embodiment. Sectional drawing of the stack which concerns on embodiment. Sectional drawing of the fuel cell which concerns on embodiment. The conceptual diagram of the vehicle which concerns on embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same members and the like are denoted by the same reference numerals, and the description of the members and the like once described is omitted as appropriate.

(Embodiment 1)
The membrane electrode assembly (MEA) of Embodiment 1 includes a first support and a first catalyst layer including a plurality of first catalyst units having a stacked structure including a void layer on the first support. The surface (first surface) where one electrode and the plurality of first catalyst units between the plurality of first catalyst units face each other and the surface (second surface) of the first catalyst unit opposite to the first support side. An electrolyte membrane in contact with both. Including a portion where the electrolyte membrane exists over a region of at least 80% of the thickness of the first catalyst layer from the surface of the first catalyst unit in contact with the electrolyte membrane on the side opposite to the first support side toward the first support. .

  FIG. 1 shows a cross-sectional view of a membrane electrode assembly (MEA) 100 of Embodiment 1 (a cross-sectional view of a gas diffusion electrode with an electrolyte (layer)). The MEA 100 in FIG. 1 has a first support 2, a first electrode 1 having a first catalyst layer 3, and an electrolyte membrane 4.

  When MEA 100 is used in a fuel cell, the electrodes on both sides are an anode and a cathode, respectively. Hydrogen is supplied to the anode and air is supplied to the cathode.

  The first electrode 1 is an electrode in which a first catalyst layer 3 is provided on a first support 2. The first catalyst 3 of the first electrode 1 is in direct contact with the electrolyte membrane 4. The contact in the embodiment is preferably direct contact.

  The first support 2 is a substrate that supports the first catalyst layer 3. The first support 2 is a so-called gas diffusion support that is generally required to be porous and conductive. Layered materials of titanium material or carbon material are generally employed. Although it does not specifically limit about the form of the 1st support body 2, The mesh which consists of a mesh, a fiber, a titanium sintered compact, etc. are mentioned. The water electrolysis characteristics may be improved by adjusting the aperture ratio of the porous substrate, particularly the pore structure of the portion in contact with the first catalyst layer 3, or the surface treatment of the substrate such as blasting. It is considered that the water supply to the first catalyst layer 3 and the discharge of the electrode reaction product became smooth, and the electrode reaction in the first catalyst layer 3 was promoted. You may attach another coating layer on a base material. In some cases, the durability of the electrode is greatly improved by the dense conductive layer. Although a coating layer is not specifically limited, Ceramic materials, such as a metal material, an oxide, and nitride, carbon, etc. can be used.

  The first support 2 often contains a water repellent in order to prevent water clogging, that is, a so-called flooding phenomenon. Examples of the water repellent of the first support 2 include fluorine-based materials such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyhexafluoropropylene, and tetrafluoroethylene-hexafluoropropylene copolymer (FEP). It is a polymer material. A suitable first support 2 is a laminate of a porous carbon layer and a carbon substrate, and the first catalyst layer 3 is provided on the porous carbon layer side.

  The first catalyst layer 3 includes a plurality of catalyst units provided on the first support 2. The first catalyst layer 3 is a carrier-less porous catalyst layer. In order to obtain high cell characteristics, a catalyst layer used in an electrochemical cell is generally constituted by a supported catalyst in which a material such as carbon is supported on the surface of the catalyst. Although the support material contributes little to the main electrocatalytic reaction, it can control the catalyst material, such as improving the reaction area of the catalyst material, and reports that the electrochemical cell can improve the pore structure, electrical conductivity, ion conductivity, etc. Has been. Carrier-free means that no carrier is used for the catalyst constituting the first catalyst layer. That is, the first catalyst layer 3 is composed of a catalyst material. Specifically, the first catalyst layer 3 includes a catalyst unit having a porous structure or a catalyst unit having a laminated structure including a void layer. When a noble metal catalyst is used, it is possible to maintain the high characteristics and high durability of the electrochemical cell even with a small amount of use.

  FIG. 2A and FIG. 2B show low-magnification transmission micrographs of a catalyst unit having a porous structure and a catalyst unit having a laminated structure including a void layer, respectively. FIG. 2A shows a catalyst unit having a porous structure, and FIG. 2B shows a catalyst unit having a laminated structure including a void layer. When the catalyst material is supported on a carrier, the catalyst is generally in the form of nano-sized particles, but in the case of a catalyst unit having a porous structure, the catalyst itself is in the form of a sponge. In the case of a catalyst unit having a laminated structure including a void layer, the catalyst has a nanosheet shape. It is possible to improve the characteristics of the electrochemical cell by using a sponge-like or nanosheet-like catalyst.

  Since the electrocatalytic reaction occurs on the surface of the catalyst, the shape of the catalyst affects the atomic arrangement and electronic state of the catalyst surface. In the case of a catalyst unit having a laminated structure including a void layer, it is desirable that adjacent nanosheets are partially integrated. The mechanism is not fully elucidated yet, but it is considered that proton conduction or hydrogen atom conduction for electrode reaction can be achieved more smoothly.

  Further, as shown in the low-magnification transmission micrograph of FIG. 2C, higher characteristics can be obtained by making the nanosheet inside the laminated structure porous. This is because gas diffusion and water management can be improved. It is more durable and robust to arrange a porous nanocarbon layer containing fibrous carbon (low magnification transmission micrograph of FIG. 2 (d)) or a nanoceramic material layer between nanosheets inside the laminated structure. It can be improved. Since the catalyst that contributes to the main electrode reaction is hardly supported by the fibrous carbon contained in the porous nanocarbon layer, the laminated structure unit including the porous nanocarbon layer is considered to be carrier-free. Here, it is preferable that the porosity of the catalyst layer is 50 Vol.% Or more and 90 Vol. Moreover, if the porosity of the catalyst layer is within this range, the substance can be sufficiently moved without reducing the utilization efficiency of the noble metal.

  The predetermined catalyst material employed in the carrier-less catalyst layer according to the present embodiment is, for example, at least one selected from the group consisting of noble metal elements such as Pt, Ru, Rh, Os, Ir, Pd and Au. Including. Such a catalyst material is excellent in catalytic activity, conductivity and stability. The aforementioned metal can be used as an oxide, and may be a complex oxide or a mixed oxide containing two or more metals.

The optimal noble metal element can be appropriately selected according to the reaction in which the MEA 100 is used. For example, when an oxygen reduction reaction is required as a cathode of a fuel cell, a catalyst having a composition represented by Pt _u M _1-u is desirable. Here, u is 0 <u ≦ 1, and the element M is from Co, Ni, Fe, Mn, Ta, W, Hf, Si, Mo, Ti, Zr, Nb, V, Cr, Al, and Sn. Is at least one selected from the group consisting of This catalyst contains more than 0 atomic% and 90 atomic% or less of Pt, and 10 atomic% or more and less than 100 atomic% of element M.

  The electrolyte membrane 4 is a membrane that requires ion conductivity. The electrolyte membrane 4 is in contact with the surface where the plurality of first catalyst units between the plurality of first catalyst units are opposed, and is in contact with the surface of the first catalyst unit 31 opposite to the first support 2 side. That is, the electrolyte membrane 4 is in contact with the surface of the first catalyst layer 3 opposite to the first support 2 side, and exists between the plurality of first catalyst units. The electrolyte membrane includes at least one electrolyte material selected from the group consisting of a fluororesin having a sulfonic acid group, tungstic acid and phosphotungstic acid. As the fluororesin having a sulfonic acid group, for example, Nafion (trademark, manufactured by DuPont), Flemion (trademark, manufactured by Asahi Glass Co., Ltd.), Ashiprec (trademark, manufactured by Asahi Kasei Co., Ltd.) and the like are preferably used. Inorganic materials such as tungstic acid and phosphotungstic acid are also preferable as the electrolyte material. When the membrane electrode assembly 100 of the embodiment is used for water electrolysis, the electrolyte membrane 4 further includes any one or more members selected from the group consisting of a hydrogen peroxide decomposing agent, a radical scavenger, and a reinforcing material. Is preferable in order to suppress deterioration of the film.

  The thickness of the electrolyte membrane 4 can be appropriately determined in consideration of the characteristics of the MEA 100. From the viewpoint of strength, dissolution resistance and MEA output characteristics, the thickness of the electrolyte membrane 4 is preferably 5 μm or more and 300 μm or less, more preferably 5 μm or more and 200 μm or less.

  The electrolyte membrane 4 is present between the plurality of catalyst units of the first catalyst layer 3. When the electrolyte membrane 4 is formed on the first catalyst layer 3, the electrolyte membrane 4 may penetrate into a shallow region of the first catalyst layer 3. In the embodiment, the electrolyte membrane penetrates into the first support 2 side deeply between the catalyst units in the embodiment, thereby reducing the resistance between the first catalyst layer 3 and the electrolyte membrane 4 and improving the power generation performance. descend.

  FIG. 3 shows an enlarged cross-sectional view of the membrane electrode assembly 100 (cross-sectional view of the gas diffusion electrode with electrolyte (layer)). In the cross-sectional view of FIG. 3, the catalyst unit 31 of the first catalyst layer 3 is shown. In the cross-sectional view of FIG. 3, the electrolyte membrane present between the plurality of catalyst units 31 of the first catalyst layer 3 is represented as an electrolyte membrane 4A, and the surface of the first catalyst unit 31 on the side opposite to the first support 2 side. The electrolyte membrane in contact with is denoted as electrolyte membrane 4B. The electrolyte membrane 4A existing between the catalyst units 31 exists up to the deep part on the first support 2 side, and contributes to the reduction in resistance between the catalyst unit 31 and the electrolyte membrane 4.

  Therefore, at least 80% of the thickness of the first catalyst layer 3 from the surface of the first catalyst unit 31 in contact with the electrolyte membrane 4B on the side opposite to the first support 2 side toward the first support 2 is covered. It is preferable to include a portion where the electrolyte membrane 4A exists. From the viewpoint of reducing the resistance between the catalyst unit 31 and the electrolyte membrane 4, at least from the surface of the first catalyst unit 31 in contact with the electrolyte membrane 4B on the side opposite to the first support 2 side toward the first support 2 It is more preferable to include a portion where the electrolyte membrane 4A exists over a region up to 85% of the thickness of the first catalyst layer 3. The electrolyte membrane over a region of at least 90% of the thickness of the first catalyst layer 3 from the surface of the first catalyst unit 31 in contact with the electrolyte membrane 4B on the side opposite to the first support 2 side toward the first support 2 Even more preferably, it includes a portion where 4A is present.

  The average depth at which the electrolyte membrane 4A exists between the plurality of catalyst units 31 of the first catalyst layer 3 is the first depth from the surface of the first catalyst unit 31 in contact with the electrolyte membrane 4B on the side opposite to the first support 2 side. It is preferable that it is 75% or more of the thickness of the 1st catalyst layer 3 toward 1 support body 2 for the same reason as the above. The average depth at which the electrolyte membrane 4A exists between the plurality of catalyst units 31 of the first catalyst layer 3 is the first depth from the surface of the first catalyst unit 31 in contact with the electrolyte membrane 4B on the side opposite to the first support 2 side. 1 is an average value of the depth (ratio to the thickness of the first catalyst layer 3) where the electrolyte membrane 4A exists toward the support 2. If the average depth at which the electrolyte membrane 4A is present between the plurality of catalyst units 31 of the first catalyst layer 3 is less than 75%, the resistance at the interface between the catalyst layer and the electrolyte increases, resulting in a decrease in power generation performance. Therefore, the average depth at which the electrolyte membrane 4A exists between the plurality of catalyst units 31 of the first catalyst layer 3 is the surface of the first catalyst unit 31 in contact with the electrolyte membrane 4B on the side opposite to the first support 2 side. The thickness of the first catalyst layer 3 is more preferably 80% or more from the first support 2 toward the first support 2. The average depth at which the electrolyte membrane 4A exists between the plurality of catalyst units 31 of the first catalyst layer 3 is the first depth from the surface of the first catalyst unit 31 in contact with the electrolyte membrane 4B on the side opposite to the first support 2 side. The thickness of the first catalyst layer 3 is more preferably 85% or more toward the support 2.

  The depth of the electrolyte membrane 4A existing between the plurality of first catalyst units 31 of the first catalyst layer 3 is preferably kept as uniform as possible throughout the catalyst layer 3. Therefore, the electrolyte membrane 4A between the plurality of first catalyst units 31 is equal to or greater than 60% between the plurality of first catalyst units 31 (number ratio when the two opposing first catalyst units 31 are set as one set). The electrolyte membrane over a region of at least 80% of the thickness of the first catalyst layer 3 from the surface of the first catalyst unit 31 in contact with the electrolyte membrane 4B on the side opposite to the first support 2 side toward the first support 2 Preferably 4A is present. The electrolyte membrane 4B that is in contact with the surface of the first catalyst unit 31 opposite to the first support 2 side and the electrolyte membrane 4A that exists between the plurality of first catalyst units 31 of the first catalyst layer 3 is directly Are preferably in contact with each other.

<Thickness of carrierless catalyst layer>
The measuring method of “catalyst layer thickness” is as follows.
First, a 9-spot sample was cut out from the MEA 100. Nine spots were designated in the plane of the catalyst layer shown in FIG. 4, and the average value of the catalyst layer thickness in these nine spots was defined as the average catalyst layer thickness of the electrode. Each spot is square and has an area of at least 5 mm ² . When the electrode length 40 and the electrode width 42 are L and W (L ≧ W), the distance 41 is W / 10 and the distance 43 is L / 10. The sample was cut from the center of the 9-spot sample to prepare a sample for TEM observation. In order to make it easy to observe the interface between the electrolyte membrane 4 and the first catalyst layer 3, the sample was immersed in a 0.1M to 1M Ru ion solution and pretreated.

  Subsequently, 3 spots / spot for each 9 spots of each MEA 100 were observed with a transmission electron microscope (TEM). A 15400-fold TEM image was obtained, and the catalyst material, electrolyte membrane, ionomer and pores were distinguished from the contrast. The imaging range was 12 μm × 9.5 μm.

  Finally, the catalyst layer thickness in each field of view was measured. Here, the “catalyst layer thickness” is defined as the catalyst layer thickness of the MEA 100 as an average value of the measured values of the entire visual field of each sample. Based on the thickness of the catalyst layer thus obtained, the porosity of the catalyst layer was determined as (1-platinum equivalent thickness / catalyst layer thickness).

<Intrusion ratio of electrolyte membrane 4 into first catalyst layer>
The penetration ratio of the electrolyte membrane 4 into the first catalyst layer 3 that is the depth of the electrolyte membrane 4A existing between the plurality of first catalyst units 31 of the first catalyst layer 3 is the TEM observed at the above 155,000 times. It is calculated from the image. Three spots / spot for each of nine spots of MEA100 were observed by TEM. The imaging range was 1.2 μm × 0.95 μm.

  As shown in the cross-sectional explanatory diagram of the membrane electrode assembly in FIG. 5 (the cross-sectional explanatory diagram of the gas diffusion electrode with electrolyte (layer)), the connecting line at the intersection of the catalyst unit 31 and the electrolyte membrane 4A is taken as the reference line 52. The reference line 52 is a line obtained by connecting line segments connecting the contact points with the electrolyte membrane 4A. The angles of the connecting line segments may be different as shown in FIG. Further, the reference line 52 passes through the outer periphery of the electrolyte membrane 4 </ b> A between the first catalyst units 31, and the reference line 52 is determined so that the distance from the first support 2 is the shortest. The distance between the vertical line from the reference line 52 and the vertical line where the distance to the interface between the catalyst unit 31 and the electrolyte membrane 4 is the longest, from each point of the interface between the catalyst unit 31 and the electrolyte membrane 4 on the electrolyte membrane 4 side. The maximum distance 51 among the distances up to 42 is defined as the depth (penetration depth) of the electrolyte membrane 4A existing between the plurality of first catalyst units 31 of the first catalyst layer 3.

  The average value of the depth of the electrolyte membrane 4A existing between the plurality of first catalyst units 31 of the first catalyst layer 3 is obtained by taking the average value of the three measured values for each nine spots of the MEA 100. In many cases, a plurality of catalyst units are continuous (catalyst unit group), and the TEM observation cannot identify the bite of the catalyst units inside the group. In this case, the penetration depth of the catalyst unit outside the group was adopted as the representative value of all the units in the group.

The percentage of the electrolyte membrane 4A between the plurality of first catalyst units 31 is the surface of the first catalyst unit 31 in contact with the electrolyte membrane 4B on the side opposite to the first support 2 side. Also, whether the electrolyte membrane 4A is present over at least 80% of the thickness of the first catalyst layer 3 from the first support 2 to the first support 2 is between the first catalyst units 31 of the first catalyst layer 3. It is calculated | required from a TEM image similarly to the depth of the electrolyte membrane 4A which exists.
Next, for each field of view, the ratio of the first catalyst unit 31 in which the biting ratio is 80% or more of the thickness of the first catalyst layer 3 was obtained and used as the biting distribution. The average value of the three fields of view of each spot was calculated and calculated as the catalyst layer biting average ratio and biting distribution of the spot. The average value of the measured values of all spots of each sample was defined as the MEA catalyst layer biting average ratio (penetration ratio (%)) and biting distribution (penetration distribution (%)).

  Next, a method for manufacturing the MEA 100 according to the embodiment will be briefly described. In the method for manufacturing the MEA 100 according to the embodiment, a step of forming the first catalyst layer 3 including the plurality of catalyst units 31 on the first support 2 and a solution containing an electrolyte on the first catalyst layer 3 are applied. And a step of pressure drying the member to which the electrolyte is applied. FIG. 6 shows a chart of a method for manufacturing the MEA 100 according to the embodiment.

  First, when producing the 1st catalyst layer 3 which has the 1st catalyst unit 31, a catalyst layer precursor is formed on the 1st support body 2 by sputtering or vapor deposition of a catalyst material and a pore making material simultaneously or alternately. Next, the pore forming agent is removed to obtain an electrode. When producing the 1st catalyst layer 3 which has the 1st catalyst unit 31, when a catalyst material and a pore making material are formed simultaneously, the catalyst unit 31 in which a catalyst material is sponge-like is obtained. Moreover, when producing the 1st catalyst layer 3 which has the catalyst unit 31, when a catalyst material and a pore making material are formed alternately, the 1st catalyst unit 31 which has a laminated structure of a catalyst material sheet form is obtained. .

  Next, the electrolyte membrane 4 is formed on the first catalyst layer 3. The electrolyte membrane 4 is produced by applying a dispersion solution of the electrolyte on the first catalyst layer 3 of the electrode and drying by heating. The electrolyte dispersion solution may be any solution in which the electrolyte is dispersed in a solvent, and the concentration may be any concentration that can be applied. Solvents include alcohol solvents such as water, methanol, ethanol, isopropanol, 1-propanol and ethylene glycol, ether solvents such as tetrahydrofuran and dimethoxyethylene, aprotic polarities such as N, N-dimethylformamide and N-methylpyrrolidone. Examples include, but are not limited to, solvents. Further, as the dispersion solvent, a mixed solvent of various solvents may be used. The solute is at least one member selected from the group consisting of a fluororesin having a sulfonic acid group, tungstic acid and phosphotungstic acid.

  Examples of the coating method include, but are not limited to, spin coating, blade coating, ink jet, gravure, and spray coating. The electrolyte membrane 4 is produced by heating and drying the applied electrolyte.

  Moreover, about application | coating, you may apply | coat the dispersion liquid from which a density | concentration differs, or may laminate | stack the thing from which electrolyte composition differs. Further, the electrolyte membrane 4 is similarly applied by applying a dispersion containing a hydrogen peroxide such as a metal oxide or a radical decomposing agent or a radical scavenger made of an organic compound to improve the durability of the membrane in the electrolyte dispersion solution. Can be formed.

  Heat drying at the time of forming the electrolyte membrane may be performed during coating, after coating, or both. However, pressure drying is performed before drying. The heating temperature depends on the solvent and electrolyte used, but is preferably 30 ° C. to 300 ° C. or less. Furthermore, by pressing and drying with a hot press or the like, the depth of penetration of the electrolyte into the uneven interface (the first catalyst layer 3 and the space between them) of the catalyst layer is greatly affected. Depending on the catalyst layer structure and the characteristics of the electrolyte used, the pressure and temperature and the drying time can be optimized.

There are hot presses, rollers, and the like as apparatuses for pressurizing and heating, but they are not limited. For example, when a hot press is used, the pressure applied to the first catalyst layer 3 from the surface where the electrolyte is applied is 0.5 kg / cm ² or more and 100 kg / cm ² or less, and the temperature is 80 ° C. or more and 200 ° C. or less. The pressure drying treatment time is preferably in the range of 20 seconds to 3600 seconds.

(Embodiment 2)
Embodiment 2 is a membrane electrode assembly 101 further having a second electrode. FIG. 7 shows a cross-sectional view of the membrane electrode assembly of the second embodiment. The membrane electrode assembly 101 of FIG. 7 includes a first electrode 2 having a first support 2 and a first catalyst layer 3, an electrolyte membrane 4, a second support 6 and a second electrode having a second catalyst layer 7. 5

  When the membrane electrode assembly 101 is used in a fuel cell, the second electrode 5 preferably has the same configuration as the first electrode 3. When the membrane electrode assembly 101 is used for water electrolysis, the second electrode 5 is preferably an oxide catalyst containing iridium.

When the MEA 101 is used for a fuel cell, the second catalyst layer 7 of the second electrode 5 preferably includes a plurality of second catalyst units. The electrolyte membrane 4 has a surface (second surface) opposite to the surface (first surface) where the plurality of second catalyst units between the plurality of second catalyst units face each other and the second support 6 side (second surface). It is preferable to be in contact with both. The electrolyte membrane 4 between the plurality of second catalyst units is at least a second catalyst layer from the surface of the second catalyst unit in contact with the electrolyte membrane 4 on the side opposite to the second support 6 side toward the second support 6. It is preferable to include a portion where the electrolyte membrane 4 exists over a region up to 80% of the thickness of 7. The second support 6 is preferably a gas diffusion support. The average depth at which the electrolyte membrane 4 exists between the plurality of second catalyst units is from the surface of the second catalyst unit in contact with the electrolyte membrane 4 on the side opposite to the second support 6 side toward the second support 6. The thickness of the second catalyst layer 7 is preferably 75% or more. In 60% or more of the plurality of second catalyst units, the electrolyte membrane 4 between the plurality of second catalyst units is from the surface of the second catalyst unit in contact with the electrolyte membrane 4 on the side opposite to the second support 6 side. It is preferable that the electrolyte membrane exists over the region up to 80% of the thickness of the second catalyst layer 7 toward the second support 6.
Other suitable conditions and measurement methods for the second electrode are also common to the first electrode 3.

  The outer periphery of the first electrode 3 is preferably present outside the outer periphery of the second electrode 5 by 1 mm or more and 50 mm or less from the viewpoint of preventing leakage. Further, in the MEA 101, the electrolyte membrane 4 is preferably smaller than the area of an electrode having a large area or larger than the area of a small electrode. This is because when the area of the electrolyte membrane is larger than that of a large electrode, the mechanical strength of the electrolyte membrane portion and the electrode interface is lowered, and when it is smaller than that of a small electrode, leakage between the anode electrode and the cathode electrode occurs.

  When the second electrode 5 is manufactured, the second electrode 5 is formed before the pressure heat treatment or after the pressure heat treatment when the MEA of the first embodiment is manufactured, and the second electrode 5 is subjected to the pressure heat treatment similarly to the first embodiment. It is preferable to produce it.

(Embodiment 3)
Embodiment 3 relates to a sub-gasket integrated membrane electrode assembly. In the third embodiment, a subgasket (gasket) is further joined to a portion between the electrode end portions of the MEA 101. The gasket is between the current collector plate and the membrane electrode assembly (MEA) in which a fuel supply or oxidant supply flow path is arranged, and is used as a seal to prevent leakage of fuel and oxidant. Further, the subgasket is used to adjust the electrolyte and the gasket, complements the gasket, and is used between the MEA 101 and the gasket.
The material of the subgasket and the gasket may not be the same material.

FIG. 8 is a cross-sectional view of the membrane electrode assembly 102 integrated with a subgasket. FIG. 3 is a diagram in which sub-gaskets or gaskets 12 and 13 are joined via an adhesive 11 so as to cover a gap between the end of the first electrode 3 and the end of the second electrode 5 of the MEA 101.
The subgasket-integrated membrane electrode assembly 102 includes a step of forming a first catalyst layer 3 including a plurality of catalyst units 31 on a first support 2, and an electrolyte on the first catalyst layer 3. A step of applying a solution, a step of pressurizing and drying the member to which the electrolyte is applied, a step of forming the second electrode 5 on the electrolyte membrane 4, and an adhesive 11 on the electrode end of the membrane electrode assembly 101. And a step of integrating the subgaskets or gaskets 12 and 13 with each other.

  Examples of the subgaskets 12 and 13 include, but are not limited to, polyvinylidene fluoride (PVdF), polyethylene, cyclic polyolefin (COP), and polyethylene naphthalate (PEN). In addition, as the adhesive 11 for joining the subgaskets 12 and 13 and the MEA 101, a film made of a thermoplastic resin (hot melt material) or a reactive resin is used, or an adhesive directly applied to the subgaskets 12 and 13 is used. May be. The melting point of the thermoplastic resin is higher than the temperature used by the electrochemical cell. Examples of the thermoplastic resin include, but are not limited to, polyolefin-based, polyester-based, polyamide-based, polyurethane, and polyvinyl acetate-ethylene copolymer. The thickness is optimized by the electrode thickness.

  The membrane electrode assemblies 100, 101, and 102 in the present embodiment may be electrolytic cells or MEMS (Micro Electro Mechanical Systems) type electrochemical cells. For example, the electrolysis cell may have the same configuration as the above-described fuel cell except that the first electrode 3 includes an oxygen generation catalyst electrode instead of the anode.

  It is also possible to control the penetration of the electrolyte membrane between the catalyst units by the assembly of the cell, for example, the clamping pressure perpendicular to the MEA 101.

(Embodiment 4)
The configuration of the electrochemical cell according to the present embodiment will be briefly described with reference to the cross-sectional view of the electrochemical cell 200 of FIG. The electrochemical cell 200 shown in FIG. 9 has fuel and oxidant supply flow path current collecting plates 14 and 15 and clamping plates 16 and 17 attached to both sides of the MEA 1 via an adhesive 11 and gaskets 12 and 13. ing. Insulating films 18 and 19 are provided between the current collector plates 14 and 15 with the fuel and oxidant supply flow paths and the clamping plates 16 and 17.

(Embodiment 5)
The configuration of the stack according to this embodiment will be briefly described with reference to the cross-sectional view of the stack 300 in FIG. The stack 300 has a configuration in which a plurality of membrane electrode assemblies 101 and 102 or a plurality of electrochemical cells 200 are connected in series. The clamping plates 20 and 21 are attached to both ends of the membrane electrode assembly 101 and 102 or the gas chemical cell 200.

(Embodiment 6)
The configuration of the fuel cell according to this embodiment will be briefly described with reference to the cross-sectional view of the fuel cell in FIG. The fuel cell 400 includes membrane electrode assemblies 101 and 102, a fuel supply unit 22, and an oxidant supply unit 23. The electrodes of the membrane electrode assemblies 101 and 102 used in the fuel cell 400 are the fuel electrode 3 and the oxidation electrode 7. Instead of the membrane electrode assembly 101, 102, the electrochemical cell 200 or the stack 300 may be used.

(Embodiment 7)
The configuration of the vehicle according to the present embodiment will be briefly described with reference to the conceptual diagram of the vehicle 500 in FIG. The vehicle 500 includes a fuel cell 400, a vehicle body 24, a motor 25, an axle 26, wheels 27, and a load control unit 28. The fuel electrode 3 and the oxidation electrode 7 of the fuel cell 400 are connected to the motor 25 as a load via the load control unit 28. The motor rotates the wheel 27 by rotating the axle 26 connected to the wheel 27. In addition, the fuel cell of embodiment can be used also as power sources of flying bodies, such as a drone, for example.

Hereinafter, examples and comparative examples will be described.
Table 1 summarizes the observation results of the catalyst layers, electrodes, catalyst layer-electrolyte membrane interfaces of Examples 1 to 10 and Comparative Examples 1 to 5 produced under the following conditions, the evaluation results of the electrochemical cell, and the like. Since the catalyst layer is carrier-free, the porosity of the catalyst layer was determined from the ratio between the equivalent platinum loading amount of the catalyst and the catalyst layer thickness. Table 1 summarizes the anode and cathode electrodes. Example 1-5 and Comparative Example 1-3 are anodes, and Example 6-10 and Comparative Example 4-5 are cathodes. The number of each produced electrode is named AE1-5, BAE1-3, CE1-5 and BCE4-5. In Comparative Examples 1, 2, and 4, since the electrolyte membrane is not applied, in these comparative examples, there is no thickness of the electrolyte membrane, the penetration ratio (%), the penetration distribution (%), and the electrolyte membrane material after coating. The pressure heating and drying conditions are represented by (-). Moreover, in Comparative Examples 3 and 5, the electrode was produced without heating and pressure drying. The specific manufacturing process of the electrode is shown in Table 1 and later. The rate of electrolyte penetration into the catalyst layer is expressed as the penetration rate (%). In addition, Table 1 also shows the distribution (%) of electrolyte intrusion into the catalyst layer.

<Preparation of electrode having carrier-less catalyst layer and membrane electrode composite>
(Fabrication of anode for fuel cell)
As a substrate, carbon paper Toray060 (manufactured by Toray Industries, Inc.) having a micro porous layer (MPL) having a thickness of 1 μm or more and 50 μm or less was prepared. On this substrate, a catalyst layer composed of units having a porous structure is formed by sputtering to have a Pt catalyst loading density of 0.05 mg / cm ² , and a diffusion layer having a carrier-less porous laminated catalyst layer A layer electrode was obtained. As the amount of catalyst, the amount of Pt supported was 0.05 mg / cm ² .

  An about 6.5% solution obtained by diluting 20% Nafion dispersion (manufactured by DuPont) with ethanol was applied on the catalyst layer of this electrode by spraying, followed by heating and drying at 60 ° C. for 10 minutes, followed by pressure heating and drying for 20 minutes. Thus, a gas diffusion electrode with an electrolyte membrane was obtained. This electrode was made into a square of 5.40 cm × 5.40 cm or 5.00 cm × 5.00 cm and used as an anode of Example 1, Example 2, Example 4, Example 5, and Comparative Example 3. In Example 3, a 0.5% nafion dispersion and a 7% nafion dispersion were prepared by diluting a 20% nafion solution with ethanol, and after applying the 0.5% nafion dispersion, the 7% dispersion was applied. Produced. These results are summarized in Table 1.

(Production of cathode for fuel cell)
As a substrate, carbon paper Toray 060 (manufactured by Toray Industries, Inc.) having a carbon layer with a thickness of 1 to 50 μm on the surface was prepared. On this substrate, a platinum catalyst layer composed of a unit having a porous structure or a laminated structure including a void layer was formed by sputtering, and an electrode having a carrier-less porous catalyst layer was obtained (platinum loading amount was 0). .18 mg / cm ² ). In sputtering, the process was adjusted so that the shape of the catalyst layer unit and the thickness of the catalyst layer were the values shown in Table 1 above. These electrodes were formed into a square of 5.00 cm × 5.00 cm or 5.40 cm × 5.40 cm, and the electrodes of Example 6, Example 7, Example 9, Example 10, and Comparative Example 5 were prepared. Summarized.

(Production of membrane electrode assembly (MEA))
The anode electrode with an electrolyte membrane produced above is cut into 54 mm squares. Further, the produced cathode electrode was cut into a 50 mm square. A SUS plate (100 mm square, thickness 1 mm), a silicon rubber sheet (100 mm square, thickness 2 mm), a PTFE film (100 mm square, thickness 200 μm), an anode electrode, a cathode electrode, a PTFE film, a silicon rubber sheet, and a SUS plate are laminated in this order. Then, after press-bonding with a hot press (0.3 ton, 165 ° C., 4 minutes), it was cooled to room temperature, and an actual electrode was used to produce an MEA.

  On the other hand, a PEN film (thickness 38 μm; Q51-38) manufactured by Teijin DuPont Films Ltd. was cut into a 75 mm square as a subgasket, and cut into a 54.5 mm square with a hollow (54 mm square electrode side subgasket). . Next, a polyamide hot melt film having a melting point of 140 ° C. (Nippon Matai Co., Ltd. NT-12 film thickness: 50 μm) is overlapped on the PEN film cut to 75 mm square and pressure-bonded at 130 ° C. for 2 minutes at 2 kg. . A PEN film laminated with a hot melt sheet was cut into a 50.5 mm square and a 50 mm square electrode subgasket.

  Example of Subgasket-Integrated Membrane Electrode Assembly by Combining the Produced Subgasket with the Produced MEA and the Sub-gasket Hollow Part and Thermocompression for 3 Minutes at 130 ° C. and 60 kg Press as in the MEA From Example 11, Example 17 was produced.

  In Comparative Example 7, an electrode with an electrolyte membrane that was not dried under pressure was used, and a subgasket was not used, and Comparative Example 8 was an electrode with an electrolyte membrane that was not dried under pressure as in Comparative Example 7. Used to produce an integrated subgasket.

(Evaluation of power generation performance of fuel cells)
A 25 cm ² single cell (anode; sappentine channel, cathode: interdigitated channel) was used as an evaluation cell for a fuel cell. The MEA was set in a fuel cell evaluation cell using PTFE films as the anode side and cathode side gaskets. Further, the obtained MEA for fuel cell was set between two separators provided with a flow path to produce a single cell (electrochemical cell) of a polymer electrolyte fuel cell.
Each MEA was evaluated for the following items using the produced single cell.

(Cell voltage evaluation)
The obtained single cell was conditioned for one day. Thereafter, the temperature was maintained at 80 ° C., and hydrogen was supplied as fuel to the anode and oxygen was supplied to the cathode. The flow rate of hydrogen was 0.6 L / min, and the flow rate of oxygen was 0.3 L / min. The relative humidity of hydrogen and air was 100%. Along with the supply of hydrogen and oxygen, the battery was discharged at a constant current density of 1 A / cm ² and the cell voltage (V) after 5 minutes was measured. Table 2 shows the numbers of the anodes and cathodes used (see Table 1) and the numbers of the produced MEAs. Except for Comparative Example 6, an electrolyte membrane coated and dried on either the anode or the cathode is used. In Comparative Example 6, an MEA was fabricated by sandwiching a 25.4 μm Nafion membrane (Nafion 211) used as an electrolyte membrane for a fuel cell between an anode and a cathode. In addition to the cell voltage, the membrane resistance (mΩ) of the MEA was measured by the AC impedance method (1 kHz) and is summarized in Table 2.

  As shown in Table 2, in the MEAs of Examples 11 to 17, the average penetration rate of the electrolyte into the catalyst unit is 80% or more. Each cell characteristic of the example was equivalent to or better than the MEA of Comparative Example 6 using nafion 211, which is a conventional commercially available electrolyte membrane, with a voltage of 0.66 to 0.68. As shown in Table 2, it is considered that in each example, the resistance value was reduced, and therefore, the penetration rate of the electrolyte into the catalyst layer was increased, so that the interface resistance was lowered and the performance was improved.

According to at least one embodiment described above, high cell voltage, high robustness, and durability can be achieved with a small amount of noble metal by controlling the interface between the catalyst layer and the electrolyte membrane layer of the membrane electrode assembly having a carrierless catalyst layer. The membrane electrode assembly and the subgasket integrated membrane electrode assembly can be provided. In addition, a fuel cell using such a membrane electrode assembly is excellent in power generation characteristics.
In the specification, some elements are represented by element symbols.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. As the electrochemical cell, a single cell of a polymer electrolyte fuel cell having hydrogen fuel was cited. However, other electrochemical cells such as a methanol fuel cell, a polymer electrolyte type water electrolysis, etc. are ionized through an electrolyte membrane or a diaphragm. The present invention can be similarly applied to an electrochemical cell having movement or mass transfer such as water. These novel embodiments described above can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

1 ... 1st electrode;
2 ... 1st support body;
3 ... 1st catalyst layer;
4 ... electrolyte membrane;
5 ... second electrode;
6 ... 2nd support body;
7 ... second catalyst layer;
11 ... adhesive layer;
12, 13 ... gasket;
14, 15 ... collector plate with fuel and oxidant supply flow path;
16, 17 ... clamping plate;
18, 19 ... insulating film;
20, 21 ... clamping plate;
22 ... Fuel supply unit;
23 ... oxidant supply unit;
24 ... Body;
25 ... motor;
26 ... axles;
27 ... wheels;
28 ... Load control unit;
31 ... 1st catalyst unit;
40 ... electrode length;
41 ... distance;
42 ... electrode width;
43 ... distance;
100, 101 ... membrane electrode assembly;
102 ... Sub gasket integrated membrane electrode assembly;
200 ... electrochemical cell;
300 ... Stack;
400 ... fuel cell;
500 ... vehicle;

Claims (11)

A first support;
A first electrode having a first catalyst layer including a plurality of first catalyst units having a laminated structure including a void layer on the first support;
An electrolyte membrane in contact with both the surface of the plurality of first catalyst units facing the plurality of first catalyst units and the surface of the first catalyst unit opposite to the first support side;
The electrolyte membrane over a region of at least 80% of the thickness of the first catalyst layer from the surface of the first catalyst unit in contact with the electrolyte membrane on the side opposite to the first support side toward the first support. Membrane / electrode assembly including a portion in which is present.   The membrane electrode assembly according to claim 1, wherein the first support is a gas diffusion support.   The membrane electrode assembly according to claim 1 or 2, wherein the electrolyte membrane includes one or more members selected from the group consisting of a fluororesin having a sulfonic acid group, tungstic acid and phosphotungstic acid.   The average depth at which the electrolyte membrane exists between the plurality of first catalyst units is from the surface of the first catalyst unit in contact with the electrolyte membrane on the side opposite to the first support side to the first support. The membrane electrode assembly according to any one of claims 1 to 3, wherein the thickness is 75% or more of the thickness of the first catalyst layer.   In 60% or more of the plurality of first catalyst units, the electrolyte membrane between the plurality of first catalyst units is a surface of the first catalyst unit in contact with the electrolyte membrane on the side opposite to the first support side. The membrane electrode assembly according to any one of claims 1 to 4, wherein the electrolyte membrane exists over a region extending from at least 80% of the thickness of the first catalyst layer toward the first support. A second electrode having a second support and a second catalyst layer including a plurality of second catalyst units having a stacked structure including a void layer on the second support;
The electrolyte membrane is in contact with both the surface of the plurality of second catalyst units facing the plurality of second catalyst units and the surface of the second catalyst unit opposite to the second support side,
The electrolyte membrane between the plurality of second catalyst units is at least the second catalyst from the surface of the second catalyst unit that is in contact with the electrolyte membrane on the side opposite to the second support side toward the second support. Including a portion where the electrolyte membrane exists over an area of up to 80% of the thickness of the layer;
The second support is a gas diffusion support;
The average depth at which the electrolyte membrane exists between the plurality of second catalyst units is from the surface of the second catalyst unit in contact with the electrolyte membrane on the side opposite to the second support side to the second support. Or more than 75% of the thickness of the second catalyst layer,
In 60% or more of the plurality of second catalyst units, the electrolyte membrane between the plurality of second catalyst units is a surface of the second catalyst unit in contact with the electrolyte membrane on the side opposite to the second support side. The membrane electrode assembly according to any one of claims 1 to 5, wherein the electrolyte membrane exists over a region extending from at least 80% of the thickness of the second catalyst layer toward the second support.   The membrane electrode assembly according to claim 6, wherein an outer periphery of the first electrode is present 1 mm or more and 50 mm or less outward from an outer periphery of the second electrode.   The electrochemical cell using the membrane electrode assembly of any one of Claim 1 thru | or 7.   A stack using the membrane electrode assembly according to any one of claims 1 to 7 or the electrochemical cell according to claim 8.   A fuel cell using the membrane electrode assembly according to any one of claims 1 to 7, the electrochemical cell according to claim 8, or the stack according to claim 9.   A vehicle using the fuel cell according to claim 10.