Electrodes, membrane electrode assemblies, and polymer electrolyte fuel cells, as well as blended ionomers containing gas-permeable polymers.

Abstract

To provide an electrode suitable for a polymer electrolyte fuel battery.SOLUTION: An electrode includes an electrocatalyst layer including a catalyst carrier having electronic conductivity, electrocatalyst particles dispersed and supported on the surface of the catalyst carrier, and an electrolyte material that coats the surfaces of the carrier and the electrode catalyst particles, and the electrolyte material contains a gas permeable polymer. The electrode has high gas permeability and excellent power generation performance when used as an electrode for a polymer electrolyte fuel battery.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an electrode and a membrane electrode assembly suitable for a solid polymer fuel cell, and a blend ionomer containing a gas-permeable polymer used therein.

Background Art

[0002] The electrode of a solid polymer fuel cell (PEFC) is composed of an electrode catalyst layer made of an electrode material and an electrolyte material, and a gas diffusion layer having both gas permeability and electron conductivity. As the electrode catalyst layer of a PEFC electrode (anode and cathode), an electrode containing an electrode material and an electrolyte material in which a carbon-based material is used as a catalyst carrier and electrode catalyst particles (typically Pt particles) are supported on the surface of the catalyst carrier is widely used (for example, Patent Document 1). Further, as an electrode catalyst layer that can provide more excellent electrode performance, an electrode catalyst layer containing an electrode material and an electrolyte material using an electronically conductive oxide such as tin oxide (SnO2) that is thermodynamically stable under PEFC operating conditions (strongly acidic, high potential) as a catalyst carrier instead of a carbon-based carrier has been developed (see, for example, Patent Documents 2 and 3).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] The electrode reaction of a PEFC proceeds at a so-called three-phase interface where electrode catalyst particles such as Pt, an electrolyte material (ionomer), and a reaction gas (oxygen or hydrogen) coexist. In the electrode catalyst layer, the electrode catalyst particles supported on the surface of the catalyst carrier are coated with the electrolyte material, and protons are supplied to the electrode catalyst particles through the electrolyte material. However, in order to promote the electrode reaction at the three-phase interface, it is desirable that the electrolyte material has excellent proton conductivity and can smoothly supply oxygen (air) or hydrogen gas to the three-phase interface.

[0005] However, among the materials for constructing the electrode catalyst layer, although improvements have been made for the electrode catalyst and the catalyst carrier, the electrolyte material contained in the electrode catalyst layer has received little attention, and the fact is that no fundamental solution to the problem has been achieved. [[ID=e6]]Currently, as the electrolyte material in the electrode catalyst layer, in most cases, a fluorine-based ionomer (typically Nafion or Aquivion), similar to the electrolyte membrane, is mixed with the electrode material and adsorbed in a form of physically coating the surface of the electrode material. Since the ionomer used for the electrolyte membrane has poor gas permeability (has gas barrier properties), there has been a problem that the gas supply to the electrode catalyst particles (electrode reaction field) is inhibited by the ionomer contained in the electrode.

[0006] Thus, in fact, there is room for improving the gas permeability of the electrolyte material in the electrode catalyst layer for further improving the performance of the PEFC. Under such circumstances, an object of the present invention is to provide an electrode having an electrode catalyst layer with excellent gas permeability. Furthermore, an object is to provide a membrane electrode assembly and a solid polymer fuel cell including the electrode.

Means for Solving the Problems

[0007] As a result of intensive studies to solve the above problems, the present inventor has found that the following invention meets the above object, and thus has reached the present invention.

[0008] That is, the present invention relates to the following electrodes and membrane electrode assemblies. <1> An electrode having an electrode catalyst layer comprising an electronically conductive catalyst support, electrode catalyst particles dispersed and supported on the surface of the catalyst support, and an electrolyte material covering the surfaces of the catalyst support and the electrode catalyst particles, wherein the electrolyte material contains a gas-permeable polymer. <2> The electrolyte material is a blended ionomer obtained by mixing a non-proton-conducting gas-permeable polymer and a proton-conducting polymer. <1> The electrodes described above. <3> The aproton-conducting gas-permeable polymer is an aproton-conducting polysubstituted acetylene. <2> The electrodes described above. <4> A non-proton-conducting polysubstituted acetylene having a trimethylsilyl group in its side chain. <3> The electrodes described above. <5> The aproton-conducting polysubstituted acetylene is poly[1-phenyl-2-[p-(trimethylsilyl)phenyl]acetylene]. <4> The electrodes described above. <6> For use in polymer electrolyte fuel cells or polymer electrolyte water electrolysis devices. <1> from <5> An electrode as described in any of the following. <7> A membrane electrode assembly comprising a solid polymer electrolyte membrane, a cathode bonded to one side of the solid polymer electrolyte membrane, and an anode bonded to the other side of the solid polymer electrolyte membrane, wherein at least one of the cathode and the anode is <1> from <6> A membrane electrode assembly having an electrode as described in any of the above. <8> <7> A polymer electrolyte fuel cell comprising the membrane electrode assembly described in [reference]. <9> <7> A solid polymer water electrolysis apparatus comprising the membrane electrode assembly described above.

[0009] Furthermore, the present invention relates to the following blended ionomers. <a1>A blended ionomer comprising a mixture of a non-proton-conducting gas-permeable polymer and a proton-conducting polymer. <a2>The oxygen permeability of the aproton-conducting gas-permeable polymer at 80°C is 100 Barrer or more. <a1>The blended ionomers described above. <a3>The aproton-conducting gas-permeable polymer is an aproton-conducting polysubstituted acetylene. <a1>or <a2>The blended ionomers described above. <a4>A non-proton-conducting polysubstituted acetylene having a trimethylsilyl group in its side chain. <a3>The blended ionomers described above. <a5>The aproton-conducting polysubstituted acetylene is poly[1-phenyl-2-[p-(trimethylsilyl)phenyl]acetylene]. <a4>The blended ionomers described above. <a6>The proton-conducting polymer is a perfluorosulfonic acid polymer. <a1>from <a5>A blended ionomer as described in any of the following. <a7>When the total of aproton-conducting gas-permeable polymers and proton-conducting polymers is set to 100% by weight, the proportion of aproton-conducting gas-permeable polymers is 0.5 to 30% by weight. <a1>from <a6>A blended ionomer as described in any of the following. <b1>A blended ionomer comprising a mixture of a non-proton-conducting gas-permeable polymer and a proton-conducting polymer, The non-proton-conducting gas-permeable polymer is poly[1-phenyl-2-[p-(trimethylsilyl)phenyl]acetylene, and the proton-conducting polymer is a perfluorosulfonic acid polymer. A blended ionomer in which, when the total amount of aproton-conducting gas-permeable polymer and proton-conducting polymer is set to 100% by weight, the proportion of the aproton-conducting gas-permeable polymer is 0.5 to 5% by weight. [Effects of the Invention]

[0010] The present invention provides an electrode having high gas permeability and excellent power generation performance, and a membrane electrode assembly equipped therewith. The electrode and membrane electrode assembly equipped therewith can be suitably used in polymer electrolyte fuel cells and polymer electrolyte water electrolyzers. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram of the structure of a polymer electrolyte fuel cell (PEFC). [Figure 2] This is a diagram illustrating the electrode catalyst layer in an electrode, showing (a) a conventional electrode and (b) the electrode of the present invention. [Figure 3] This figure shows the results of the electrochemical evaluation (IV properties) of PEFCs using the electrolyte materials (blended ionomers) of Examples 1 to 4 and Comparative Example 1 (Nafion). [Figure 4] This figure shows the relationship between the proportion (wt%) of the gas-permeable polymer (PTMSDPA) in the cathode of the PEFCs in Examples 1-4 and Comparative Example 1 and the current density (A cm-2) at 0.2V. [Figure 5] This figure shows the results of the electrochemical evaluation (concentration overpotential) of the PEFCs in Examples 1-4 and Comparative Example 1 (current density 1.45 A cm-2). [Figure 6] These are the small-angle X-ray scattering (SAXS) evaluation results for the blended ionomers of Examples 1-4 and Comparative Example 1 (Nafion). [Figure 7] These are the X-ray diffraction (XRD) evaluation results for the blended ionomers of Examples 1-4 and Comparative Example 1 (Nafion). [Figure 8] This figure shows the relationship between interplane spacing and hydrophilic domain size in the blended ionomers of Examples 1-4 and Comparative Example 1 (Nafion). [Figure 9] This is a schematic diagram of Nafion and its blended ionomer (PTMSDPA + Nafion) based on structural analysis. [Figure 10] These are the evaluation results for the oxygen permeability resistance in the electrode catalyst layers of Examples 1-4 and Comparative Example 1. [Modes for carrying out the invention]

[0012] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples, and can be modified and implemented as such without departing from the spirit of the invention. In this specification, "~" is used to mean an expression that includes the numerical value or physical quantity before and after it.

[0013] In this specification, "PEFC cathode conditions" refer to the conditions at the cathode during normal operation of the PEFC, meaning a temperature of room temperature to 150°C and the supply of an oxygen-containing gas such as air (oxidizing atmosphere). "PEFC anode conditions" refer to the conditions at the anode during normal operation of the PEFC, meaning a temperature of room temperature to 150°C and the supply of a hydrogen-containing fuel gas (reducing atmosphere). In the following, "at least one of the PEFC cathode conditions and anode conditions" may be referred to as "fuel cell operating conditions."

[0014] Furthermore, in this specification, "electrode" means both the anode, which reacts with a fuel gas such as hydrogen, and the cathode, which reacts with an oxidizing gas such as oxygen or air, and its use is not particularly limited to one or the other.

[0015] The present invention relates to an electrode (hereinafter referred to as "the electrode of the present invention") having an electrode catalyst layer comprising an electronically conductive catalyst support, electrode catalyst particles dispersed and supported on the surface of the catalyst support, and an electrolyte material covering the surface of the support and the electrode catalyst particles, wherein the electrolyte material contains a gas-permeable polymer. In the following, the catalyst support and the electrode catalyst particles supported thereon may be collectively referred to as the "electrode material."

[0016] <1. Electrode> The electrode of the present invention can be suitably used as an electrode (cathode and / or anode) for a PEFC. It can also be suitably used as an electrode for a solid polymer water electrolysis apparatus that uses a solid polymer electrolyte membrane similar to that of a PEFC.

[0017] Figure 1 is a conceptual diagram showing a typical configuration of a PEFC. In a PEFC, hydrogen is supplied to the fuel electrode (anode), and (reaction 1) 2H2 → 4H + +4e - The resulting proton (H + (The electrons) are supplied to the air electrode (cathode) via a solid polymer electrolyte membrane, and the generated electrons are supplied to the air electrode (cathode) via an external circuit (not shown), (reaction 2) O2 + 4H + +4e - →2H2O reacts with oxygen to produce water. This electrochemical reaction between the fuel electrode (anode) and the air electrode (cathode) generates a potential difference between the two electrodes.

[0018] The electrode (anode and cathode) according to the present invention is a gas diffusion electrode composed of an electrode catalyst layer responsible for the electrode reaction and a gas diffusion layer responsible for supplying the reaction gas to the electrode catalyst layer. Figure 2 shows explanatory diagrams of the electrode catalyst layers in a conventional electrode and the electrode of the present invention. In the electrode catalyst layer of a conventional electrode, schematic diagram shown in Figure 2(a), the electrode catalyst layer has a structure in which Pt particles (electrode catalyst particles) dispersed and supported on the surface of carbon (catalyst support) are coated with an electrolyte material. The electrolyte material used in conventional electrodes is a proton conductive electrolyte material (typically Nafion) with high gas barrier properties similar to that of an electrolyte membrane. In order to exhibit sufficient proton conductivity, the electrolyte material (high molecular weight ionomer) is adsorbed onto the surface of the electrode catalyst particles by physically coating them. Therefore, although conventional electrodes have excellent proton conductivity, they have poor gas permeability, which hinders the supply of reaction gases such as oxygen to the electrode reaction field (so-called three-phase interface). When the amount of electrolyte material in the electrode catalyst layer is reduced to improve gas permeability, there is a problem that the electrode catalyst particles tend to aggregate or fall off.

[0019] In contrast, the electrode catalyst layer of the electrode of the present invention, schematically shown in Figure 2(b), has a structure in which Pt (electrode catalyst particles) dispersed and supported on the surface of carbon (catalyst support) is coated with an electrolyte material, similar to conventional electrodes. However, because the electrolyte material contains a highly gas-permeable ionomer (details described later), the supply of reaction gas to the electrode reaction field (so-called three-phase interface) is not hindered compared to conventional electrolyte materials with high gas barrier properties (typically Nafion). Therefore, even though the electrode of the present invention has a structure in which electrode catalyst particles are coated with an electrolyte material, it is possible to smoothly supply reaction gases such as oxygen to the electrode reaction field, thus avoiding a decrease in electrode performance caused by insufficient supply of reaction gas.

[0020] The catalyst support, electrode catalyst particles, and electrolyte material constituting the electrode catalyst layer of the electrode of the present invention will be described in more detail below.

[0021] (Catalyst support) In the electrode of the present invention, the catalyst support serves as a support for the electrode catalyst particles and also as an electron conduction path for the electrode. The material is not particularly limited as long as it can be used under at least one of the cathode and anode conditions of the PEFC, and can be appropriately selected depending on the type of electrode catalyst particles and ionomer.

[0022] There are no particular restrictions on the shape of the catalyst support; it just needs to be large and shaped to ensure sufficient space for smooth diffusion of gases such as hydrogen and oxygen within the electrode, and for the discharge of water (vapor). Materials of any shape and size, such as granular or fibrous, can be used.

[0023] For example, in the case of particulate catalyst supports, the average particle size is preferably 3 to 200 nm. The "average particle size of particulate catalyst supports" can be obtained by the average value of the particle diameters of any 20 particles examined from electron microscope images.

[0024] To increase the amount of electrode catalyst supported, the catalyst support should preferably have a large surface area while maintaining mechanical strength. Specifically, the BET specific surface area should be 70 m². 2 A value of 100m / g or more is preferable, and more preferably 100m 2 / g or more, more preferably 150m 2 It is 1 / g or more.

[0025] Furthermore, the optimal amount of catalyst support in the electrode of the present invention varies depending on the physical properties of the catalyst support, such as particle size (or length in the case of fibrous material) and surface area, as well as the method of manufacturing the catalyst support. Therefore, it is determined appropriately within a range that allows a sufficient amount of electrode catalyst particles to be supported.

[0026] Typical catalyst supports include carbon-based materials, metallic materials, and oxide-based materials. One or more catalyst supports may be used.

[0027] Carbon-based materials can be used in any shape and size, such as granular or fibrous form. For granular carbon, known carbon materials used for electrodes in PEFCs (such as carbon black and mesoporous carbon) can be used. The size of the granular carbon is arbitrary, but for example, the secondary particle size is 0.03 to 500 μm (primary particle size is approximately 10 nm to 100 nm).

[0028] Furthermore, fibrous carbon refers to hollow or fibrous carbon materials, specifically including carbon nanotubes (CNTs) and carbon nanofibers. In this invention, "carbon nanotubes" includes single-walled CNTs, double-walled CNTs, multi-walled CNTs, and mixtures thereof.

[0029] In order to achieve both electrical conductivity and gas diffusion within the electrode when it is formed, the fibrous carbon is preferably 2 nm to 10 μm in diameter and 0.03 to 500 μm in length. While the term "fibrous carbon" often refers to hollow or fibrous carbon materials, such as carbon nanotubes with a diameter of 100 nm or less, or vapor-grown carbon fibers (VGCF) with a diameter of approximately 100 to 1000 nm, or activated carbon fibers with a diameter of 1 μm to 20 μm, there are no clear regulations regarding the length and designation of these carbon materials. Therefore, in this specification, these are collectively referred to as fibrous carbon.

[0030] Examples of metallic materials include conductive auxiliary materials made of titanium or titanium alloys, with fibrous materials being particularly preferred. "Titanium alloy" refers to "an alloy containing 40 mol% or more of Ti." The metal alloyed with Ti is not particularly limited, as long as it does not impair the objectives of the present invention.

[0031] As oxide-based materials, thermodynamically stable electron-conducting oxides can be used under at least one of the cathode and anode conditions of PEFCs. Specifically, electron-conducting oxides mainly composed of one selected from tin oxide, molybdenum oxide, niobium oxide, tantalum oxide, titanium oxide, and tungsten oxide can be used. Here, in the present invention, "main electron-conducting oxide" means (A) those consisting only of the matrix oxide, and (B) composite oxides doped with other elements, in which the matrix oxide is present in an amount of 50 mol% or more.

[0032] Examples of elements that can be doped include Sn, Ti, Sb, Nb, Ta, W, In, V, Cr, Mn, and Mo (however, these must be different elements from the parent oxide). The doped elements must have a higher valence than the parent oxide. For example, if the parent oxide is tin oxide, then from the above list of doping elements, elements other than Sn (e.g., Nb) would be selected.

[0033] A suitable example of an electronically conductive oxide when the electrode of the present invention is used as a cathode for a PEFC is an oxide mainly composed of tin oxide. Here, "oxide mainly composed of tin oxide" refers to a composite oxide containing 50 mol% or more of the target tin oxide. As an element, tin (Sn) is thermodynamically stable as an oxide, SnO2, under the cathode conditions of a PEFC, and does not undergo oxidative decomposition. Furthermore, tin oxide has sufficient electronic conductivity and can serve as a support capable of highly dispersed support of electrode catalyst particles (especially noble metal particles). Furthermore, when used as an anode, oxides primarily composed of tin oxide are undesirable because they are reduced to metallic Sn under the anodic conditions of PEFC.

[0034] Among oxides mainly composed of tin oxide, niobium-doped tin oxide, which is doped with 0.1 to 20 mol% niobium (Nb), is particularly preferred because it allows for the formation of fuel cell electrodes with superior electrode performance.

[0035] Another suitable example of an electronically conductive oxide for the electrode of the present invention is an oxide mainly composed of titanium oxide. As an element, titanium (Ti) is thermodynamically stable under the anode conditions of a PEFC, and its oxide, TiO2, does not undergo reduction. Furthermore, an oxide mainly composed of titanium oxide is thermodynamically stable not only under the anode conditions of a PEFC but also under the cathode conditions, and therefore can be suitably used as a cathode.

[0036] Another preferred example of the electron-conducting oxide of the electrode of the present invention is one in which the skin layer is made of a Ti-rich oxide and the core particles are made of a Ti-containing composite oxide. The Ti-rich oxide layer is stable under both cathode and anode conditions of the PEFC and has some electronic conductivity, making it suitable as a skin layer.

[0037] Examples of Ti-containing composite oxides for core particles include Ti-containing perovskite-type oxides and spinel-type oxides. Since both the skin layer and the core particle surface contain Ti, the crystal lattice matching is good. In particular, it is preferable that the Ti-containing composite oxide is a perovskite-type oxide represented by the compositional formula ABO3, where the A site is at least one selected from the group Ca, Sr, Ba, and La, and the B site is Ti. A particularly suitable Ti-containing perovskite-type oxide is SrTiO3, where the A site is Sr and the B site is Ti. Note that some of the Sr at the A site may be substituted with other atoms.

[0038] Furthermore, in the Ti-containing perovskite-type oxide, a portion of the Ti at the B site may be substituted with at least one selected from the group consisting of Sb, Nb, Ta, W, Co, V, Cr, Mn, and Mo.

[0039] When oxide-based materials are used directly as catalyst supports for electrodes, they should be of a size and shape that allows for continuous contact and ensures sufficient space for smooth diffusion of gases such as hydrogen and oxygen, and discharge of water (steam) within the fuel cell electrode. Specifically, examples include secondary particles with an average particle size of 0.1 to 5 μm (preferably 0.3 to 1 μm), which are aggregates of primary particles with an average particle size of 1 to 500 nm (preferably 1 to 100 nm).

[0040] Alternatively, the fused body may have a chain-like or cluster-like structure formed by fusing electron-conductive oxides of primary particles (average primary particle diameter of 5 nm to 100 nm).

[0041] Oxide-based materials offer excellent stability under fuel cell operating conditions, but tend to have lower electronic conductivity compared to carbon-based and metallic materials. Therefore, when the catalyst support is an oxide-based material, it can be used in combination with a conductive additive. In this specification, "conductive additive" refers to a material contained in the electrode that improves electronic conductivity when the electrode is formed.

[0042] There are no restrictions on the manner in which the electrode material and the conductive auxiliary material are immobilized, but for example, a preferred embodiment is one in which the electrode material is dispersed and supported on the surface of the conductive auxiliary material. In this case, the average particle size of the electrode material is preferably 1 to 200 nm, and more preferably 1 to 40 nm. Alternatively, the conductive auxiliary material may be coated with a thin film of electronically conductive oxide. The thin film of electronically conductive oxide can be formed, for example, by coating the conductive auxiliary material with the electronically conductive oxide using a dry method such as vapor deposition.

[0043] There are no particular restrictions on the conductive additive, but the carbon-based and metal-based conductive additives mentioned above can be used. A detailed explanation is provided above, so it will be omitted here.

[0044] (electrode catalyst particles) In the electrode of the present invention, the electrode catalyst particles may be either a noble metal catalyst or a non-noble metal catalyst, as long as they have electrochemical catalytic activity for the reduction of oxygen (and oxidation of hydrogen). Preferably, they are selected from noble metals such as Pt, Ru, Ir, Pd, Rh, Os, Au, Ag, and alloys containing these noble metals. Note that "alloys containing noble metals" include "alloys consisting only of the above noble metals" and "alloys consisting of the above noble metals and other metals containing 10% by mass or more of the above noble metals." The "other metals" alloyed with the noble metals are not particularly limited, but Co, Ni, Ti, W, Ta, Nb, and Sn can be given as preferred examples, and one or more of these may be used. Furthermore, two or more of the above noble metals and alloys containing noble metals may be used in a phase-separated state. Note that the above noble metals and alloys containing these noble metals may be referred to as "electrode catalyst metals" below.

[0045] Examples of non-precious metal catalysts include oxides of Ta, Zr, Ti, and W (TaOx, ZrOx, TiOx, WOx), nitrides (TaNx, ZrNx, TiNx), and oxynitrides (TaOxNy, ZrOxNy, TiOxNy) (where x and y are arbitrary numbers).

[0046] Among electrode catalyst metals, when the electrode of the present invention is used as an electrode for a polymer electrolyte fuel cell (PEFC), Pt and Pt-containing alloys are particularly suitable because they exhibit high electrochemical catalytic activity for oxygen reduction (and hydrogen oxidation) in the temperature range around 80°C, which is the operating temperature of the PEFC.

[0047] Furthermore, when the electrode of the present invention is used as an electrode in a solid polymer water electrolysis apparatus, Ir, Ir alloys, Pt, and Pt alloys, which have excellent electrolytic activity of water, are preferred as the electrode catalyst metal. In this case, Ir, Ir alloys, Pt, and Pt alloys may be used as Ir oxides or Pt oxides by heat treatment or the like.

[0048] The shape of the electrode catalyst particles is not particularly limited, and shapes similar to those of known electrode catalyst particles can be used. Specific shapes include spheres, ellipses, polyhedra, and core-shell structures. Furthermore, the structure of the electrode catalyst particles is not limited to crystals; it may be amorphous or a mixture of crystalline and amorphous materials.

[0049] The smaller the size of the electrode catalyst particles, the greater the effective surface area for electrochemical reaction, and therefore the higher the electrochemical catalytic activity tends to be. However, if the size is too small, the electrochemical reaction activity decreases. Therefore, the size of the electrode catalyst particles is 0.3 to 30 nm, more preferably 1 to 10 nm, as the average particle size. In this invention, the "average particle size of electrode catalyst particles" can be obtained by the average value of the particle sizes of 20 electrode catalyst particles examined from electron microscope images. When calculating the average particle size from electron microscope images, if the shape of the fine particles is other than spherical, the length in the direction showing the maximum length of the particle is taken as the particle size. That is, one preferred embodiment of the electrode catalyst particles in the electrode of this invention is an electrode catalyst particle made of Pt and a Pt-containing alloy with an average particle diameter of 0.3 to 30 nm.

[0050] The amount of electrode catalyst particles supported is determined appropriately, taking into account conditions such as the type of catalyst, the shape and size of the catalyst support. If the amount of catalyst supported is too little, the electrode performance will be insufficient, and if it is too much, the electrode catalyst particles may aggregate, leading to a decrease in performance.

[0051] When the amount of electrode catalyst particles supported is preferably 1 to 60% by mass, more preferably 10 to 50% by mass, relative to the total weight of the electrode material (electrode catalyst particles and catalyst support), excellent catalytic activity per unit mass is achieved, and the desired electrode reaction activity corresponding to the supported amount can be obtained.

[0052] Furthermore, the amount of electrode catalyst particles supported is typically 10 to 50% by mass relative to the catalyst support. Within this range, excellent catalytic activity per unit mass is achieved, and the desired electrochemical catalytic activity can be obtained according to the supported amount. If the amount of supported material is too small, the electrode reaction activity will be insufficient. If the amount is too large, aggregation of the electrode catalyst particles is likely to occur, leading to a decrease in the effective surface area for the electrochemical reaction of oxygen and hydrogen. The amount of supported electrode catalyst particles can be determined, for example, by inductively coupled plasma emission spectrometry (ICP).

[0053] A known metal support method can be used to support the electrode catalyst precursor or electrode catalyst particles on the catalyst support. The electrode catalyst precursor can be any material that, after being supported with the aforementioned electrode catalyst precursor, is reduced to become a zero-valent electrode catalyst metal. When the electrode catalyst particles are platinum (Pt), specific examples of electrode catalyst precursors include platinum halides such as platinum chloride, platinum bromide, and platinum iodide; inorganic salts of platinum such as chloroplatinic acid, ammonium tetrachloroplatinate, and potassium hexachloroplatinate; and organic salts of platinum such as platinum acetylacetonate, platinum hexafluoroacetylacetonate, dichloro(1,5-cyclooctadiene)platinum, and platinum cyanide. If the electrode catalyst particles are made of a metal other than Pt, the corresponding precursor should be used.

[0054] As a method of support, suitable methods that can obtain highly dispersed electrode catalyst particles with small particle size include the noble metal acetylacetonate method using noble metal acetylacetonate and the colloid method using noble metal colloid.

[0055] The method using noble metal acetylacetonate as the electrode catalyst precursor (noble metal acetylacetonate method) involves supporting the noble metal acetylacetonate, which is the electrode catalyst precursor, on a support, and then directly converting the electrode catalyst precursor into electrode catalyst particles. In this method, since the noble metal precursor does not contain residual impurities, an improvement in catalytic activity is expected.

[0056] Examples of noble metal acetylacetonates include those of noble metals such as Pt, Ru, Ir, Pd, Rh, Os, Au, and Ag, and one or more of these can be used. The solvent can be any organic solvent that can disperse the noble metal acetylacetonate, such as acetone and dichloromethane.

[0057] The colloid method involves dispersing a support in a solution containing a colloid of an electrode catalyst precursor (particularly a noble metal colloid), and then reducing the colloid of the electrode catalyst precursor to support it as electrode catalyst particles on the support. The colloid method can produce electrode metal particles with a uniform nano-size particle size distribution without the use of surfactants or organic solvents.

[0058] The electrode catalyst particles or electrode catalyst precursors supported on the catalyst carrier may contain metal oxides in an unstoichiometric ratio and have low activity in their current state. Therefore, the electrochemical catalytic activity of the metal that forms the electrode catalyst is activated by heat treatment in an inert atmosphere such as nitrogen or argon, or a reducing atmosphere containing hydrogen.

[0059] The heat treatment conditions should be appropriately selected depending on the composition of the electron-conducting oxide and the type of metal or precursor used as the electrode catalyst.

[0060] (Electrolyte materials) The electrolyte material used in the electrode of the present invention (hereinafter sometimes referred to as "the electrolyte material of the present invention") may be any polymer that has gas permeability to a degree that does not inhibit the electrode reaction and also has ionic conductivity (proton conductivity).

[0061] A key feature of the electrode of the present invention is that the electrolyte material coating the surface of the electrode material (catalyst support and electrode catalyst particles) contains a gas-permeable polymer and has high gas permeability. As a result, compared to electrodes using conventional electrolyte materials with high gas barrier properties, the supply of reaction gas to the electrode material (especially the electrode catalyst particles) is not hindered even under high-load operation that consumes a large amount of reaction gas, thereby enabling high power generation capacity.

[0062] In the present invention, the "gas-permeable polymer" is a polymer material having a higher oxygen gas permeability than the ionomer used for the electrolyte membrane. Typically, the oxygen permeability at 80°C is more than 10 Barrer, preferably 100 Barrer or more, and more preferably 200 Barrer or more. Note that 1 Barrer = 10 -10 cm 3 (STP)·cm / cm 2 ·s·cmHg).

[0063] More specifically, the gas-permeable polymer preferably has a higher oxygen permeability than Nafion 212 which is widely used as an electrolyte membrane. The oxygen permeability (80°C) of Nafion 212 is 10 Barrer.

[0064] Note that the gas-permeable polymer includes both those that do not have proton conductivity by themselves and those that have proton conductivity. When there is no need to distinguish whether or not it has proton conductivity, it is simply described as "gas-permeable polymer".

[0065] Either a "non-proton-conductive gas-permeable polymer" that does not have proton conductivity by itself or a "proton-conductive gas-permeable polymer" that has proton conductivity can be used as the gas-permeable polymer. When a non-proton-conductive gas-permeable polymer that does not have proton conductivity is used for the electrolyte material of the present invention, it can be mixed with other proton-conductive polymers and used as a blend ionomer. In the present invention, "blend ionomer" means a mixed polymer that contains a gas-permeable polymer and has proton conductivity as a whole mixture by mixing with a proton-conductive polymer. Note that the non-proton-conductive gas-permeable polymer does not have proton conductivity by itself, but has proton conductivity by mixing with a proton-conductive polymer to form a blend ionomer.

[0066] The mixing ratio of aproton-conducting gas-permeable polymer and proton-conducting polymer is appropriately determined within a range that can provide the gas permeability and proton conductivity necessary to advance the electrode reaction in the electrode catalyst layer. For example, when the total of the aproton-conducting gas-permeable polymer and the proton-conducting polymer is 100% by weight, the proportion of the aproton-conducting gas-permeable polymer is 0.5 to 30% by weight.

[0067] The proton-conducting polymer mixed with the aproton-conducting gas-permeable polymer can be any known fluorine-based or hydrocarbon-based electrolyte material used as an electrolyte material for PEFCs, as long as it does not impair the effects of the present invention.

[0068] As a fluorine-based electrolyte material, for example, perfluorosulfonic acid polymers can be used. Perfluorosulfonic acid polymers are polymers (for example, the structural units shown below) in which side chains containing sulfonic acid groups are bonded to the main chain of a fluororesin. By introducing highly electronegative fluorine atoms, they become chemically very stable, have a high degree of dissociation of sulfo groups, and can achieve high proton conductivity.

[0069] [ka]

[0070] Suitable examples of commercially available perfluorosulfonic acid polymers include Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Corporation), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.), and Aquivion (registered trademark, manufactured by Solvay).

[0071] In particular, a suitable commercially available perfluorosulfonic acid polymer is "5% Nafion TM Dispersion solution DE520 CS type and "5% Nafion TM The dispersion solution "DE521 CS type" can be used. These are copolymers of perfluorosulfonic acid (PFSA) and polytetrafluoroethylene (PTFE) which have excellent chemical stability (H + It is of the ) type and is used for creating thin films for fuel cells and as a coating agent, etc.

[0072] Examples of hydrocarbon-based polymer electrolyte materials include polymers such as polysulfonic acid, polyvinyl sulfonic acid, polystyrene sulfonic acid, polyarylether ketone sulfonic acid, polyphenyl sulfonic acid, polybenzimidazole sulfonic acid, polybenzimidazole phosphonic acid, and polyimide sulfonic acid, as well as polymers having side chains such as alkyl groups.

[0073] The structure of the gas-permeable ionomer of the present invention is not particularly limited as long as it does not impair the objective of the present invention, but the polysubstituted acetylene described below is a preferred example. Polysubstituted acetylene is a polymer consisting of a main chain made of an acetylene skeleton and side chains having functional groups. Due to the steric repulsion between the rigid main chain skeleton and the bulky substituents, the polymer as a whole has a sparse structure and therefore exhibits high gas permeability.

[0074] As the polysubstituted acetylene, either aproton-conducting polysubstituted acetylene or proton-conducting polysubstituted acetylene can be used.

[0075] As the aproton-conducting polysubstituted acetylene, polyacetylene having a trimethylsilyl group in the side chain is preferred, and examples include polymers having a polyacetylene skeleton represented by any of the structural units of the following formulas (1) to (5). The degree of polymerization (the numerical values ​​of n (and m) in the formula) is arbitrary as long as it does not impair gas permeability.

[0076] [ka]

[0077] Among these, poly[1-phenyl-2-[p-(trimethylsilyl)phenyl]acetylene (PTMSDPA), represented by the structural unit of formula (2), is a suitable example. PTMSDPA has an oxygen permeability of 260 Barrer at 80°C, which is significantly higher than that of Nafion (10 Barrer). Therefore, when PTMSDPA is incorporated into a blended ionomer, high gas permeability can be achieved even in small amounts. When PTMSDPA is used as the aproton-conducting gas-permeable polymer and perfluorosulfonic acid polymer (typically Nafion) is used as the proton-conducting polymer, the proportion of PTMSDPA is preferably 0.5 to 5% by weight, and more preferably 1 to 3% by weight, when the total of the aproton-conducting gas-permeable polymer and the proton-conducting polymer is 100% by weight.

[0078] Furthermore, the proton-conducting polysubstituted acetylene is preferably a polyacetylene having proton-conducting functional groups in its side chains. Examples of proton-conducting functional groups include sulfonic acid groups, phosphoric acid groups, and carboxylic acid groups. Among these, sulfonic acid groups are preferred because they are excellent at improving proton conductivity.

[0079] A suitable example of a proton-conducting polysubstituted acetylene is a polymer having a polyacetylene skeleton represented by the following structural units. The degree of polymerization (the value of m in the formula) is arbitrary as long as it does not impair gas permeability.

[0080] [ka]

[0081] (Gas diffusion layer) The gas diffusion layer is not particularly limited as long as it does not impair the objectives of the present invention, and conventionally known gas diffusion layers can be used. For example, conductive carbon-based sheet-like members having a pore size distribution of about 100 nm to 90 μm, which have been conventionally used as gas diffusion layers in PEFCs, can be used, and preferably, water-repellent treated carbon cloth, carbon paper, carbon nonwoven fabric, etc. can be used. Alternatively, sheet-like members other than carbon-based materials such as stainless steel may also be used. The thickness of such a gas diffusion layer is not particularly limited, but is usually about 50 μm to 1 mm. Furthermore, the gas diffusion layer may have a microporous layer on one side consisting of an aggregate of carbon fine particles with an average particle size of about 10 to 100 nm and a water-repellent agent.

[0082] <2. Membrane electrode assemblies, polymer electrolyte fuel cells, and polymer electrolyte water electrolyzers> The membrane electrode assembly of the present invention is a membrane electrode assembly having a solid polymer electrolyte membrane, a cathode bonded to one side of the solid polymer electrolyte membrane, and an anode bonded to the other side of the solid polymer electrolyte membrane, wherein at least one of the cathode and the anode is the electrode of the present invention.

[0083] The membrane electrode assembly (MEA) of the present invention can be suitably used in applications such as polymer electrolyte fuel cells and polymer electrolyte water electrolyzers. In the membrane electrode assembly of the present invention, the components other than the electrodes are the same as those of known membrane electrode assemblies for polymer electrolyte fuel cells or polymer electrolyte water electrolyzers (see, for example, Japanese Patent No. 6598159 and Japanese Patent No. 6779470), so a detailed description is omitted.

[0084] Furthermore, in the PEFC according to the present invention, components other than the electrodes of the present invention (at least one of the fuel electrode and the air electrode) are the same as those of known polymer electrolyte fuel cells, so a detailed explanation is omitted (see, for example, Japanese Patent No. 6598159). In practice, a fuel cell stack is formed by stacking a number of polymer electrolyte fuel cells (single cells) according to the power generation performance of the present invention, and it is used by assembling other incidental devices such as a gas supply device and a cooling device.

[0085] Furthermore, in the polymer electrolyte water electrolysis apparatus of the present invention, the components other than the membrane electrode assembly of the present invention are the same as those of known polymer electrolyte water electrolysis apparatuses, so a detailed explanation is omitted (see, for example, Japanese Patent No. 6779470).

[0086] The present invention has been described above with reference to the drawings, but the matters disclosed herein, with the exception of the fuel cell body described below, are illustrative and not restrictive. In particular, matters not explicitly disclosed herein, such as various parameters, dimensions, weight, and volume of components, do not deviate from what is normally practiced by those skilled in the art, and values ​​that can be easily anticipated by those skilled in the art can be adopted. [Examples]

[0087] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0088] <Synthesis of gas-permeable polymers> As a gas-permeable polymer, poly[1-phenyl-2-[p-(trimethylsilyl)phenyl]acetylene (PTMSDPA) was synthesized by a method in accordance with non-patent literature (Macromolecules 1992, 25 (21), 5816-5820). The trimethyl[4-(phenylethyl)phenyl]silane, tantalum chloride, super-dehydrated toluene, methanol, ethanol, tetrahydrofuran (THF), and Nafion 5-millimeter dispersion (DE520 CS type) used in the synthesis were purchased from Fujifilm Wako Pure Chemical Industries, Ltd.

[0089] The structural formulas for Nafion and PTMSDPA are shown below.

[0090] [ka]

[0091] [ka]

[0092] The synthesis of PTMSDPA was carried out under a dry nitrogen atmosphere. First, a monomer solution was prepared by dissolving trimethyl[4-(phenylethyl)phenyl]silane (1 g, 4 mmol) in toluene (3 mL) in a Schlenk tube. Next, a catalyst solution was prepared in another Schlenk tube by mixing tantalum chloride (143 mg, 0.4 mmol), tetrabutyltin (0.26 mL, 0.8 mmol), and toluene (3 mL). This catalyst solution was aged at 80°C for 10 minutes. Subsequently, the monomer solution added directly to the catalyst solution was polymerized at 80°C for 24 hours. To stop the polymerization, a small amount of methanol was added to the reaction mixture. Finally, the reaction mixture was diluted with toluene (200 mL) and precipitated with an excess amount of methanol. The precipitated polymer was obtained by vacuum filtration and drying. Polymerization was analyzed by gel permeation chromatography (GPC) and H2. 1 This was confirmed through NMR analysis.

[0093] <Preparation of gas-permeable electrolyte materials> An electrolyte material (hereinafter referred to as "electrolyte material (blended ionomer)") was prepared, consisting of a mixture of PTMSDPA (aproton-conducting gas-permeable polymer) and Nafion (a proton-conducting polymer).

[0094] The electrolyte materials (blended ionomers) for Examples 1-4 were prepared using the following procedure. First, PTMSDPA dissolved in THF and a 5% Nafion dispersion were placed in a container in the weight ratios shown in Table 1 (1.25, 2.5, 3.75, 10 wt%) relative to Nafion (total polymer concentration 28 wt%), and the mixture was heated using an ultrasonic homogenizer for 10 minutes to obtain solutions containing the electrolyte materials (blended ionomers) of Examples 1 to 4. In addition, a Nafion dispersion without PTMSDPA was prepared as the electrolyte material for Comparative Example 1.

[0095] Table 1 summarizes the compositions of the electrolyte materials (blended ionomers) for Examples 1 to 4 and the electrolyte material for Comparative Example 1.

[0096] [Table 1]

[0097] <Electrochemical evaluation (single cell, power generation, durability evaluation)> Electrochemical evaluation was performed using MEAs having cathodes formed using the electrolyte materials (blended ionomers) of Examples 1 to 4. Furthermore, 46 wt% Pt / C (Tanaka Kikinzoku Kogyo Co., Ltd., TEC10E50E) was used as the electrode material constituting the electrodes (anode and cathode). In addition, the Pt content was 0.3 mg / cm³ during the formation of the electrodes (anode and cathode). 2 I adjusted it so that it would work.

[0098] (Example 1) First, an anode formation dispersion solution was prepared by dispersing an electrode material (46 wt% Pt / C) in a predetermined organic solvent containing a Nafion solution onto a Nafion membrane (Nafion 212, thickness: 50 μm) as the electrolyte membrane. The resulting dispersion solution was spray-printed onto the Nafion membrane to create an anode (electrode catalyst layer) of a predetermined thickness on the Nafion membrane. A water-repellent carbon paper (Toray Industries, Ltd., model number: EC-TP1-060T) was placed on top of the anode (electrode catalyst layer) as a gas diffusion layer. Next, the electrode material (Pt / C) and the electrolyte material solution from Example 1 (a mixed solution of PTMSDPA and Nafion) were mixed so that the weight ratio of the electrode (after drying) was electrode material:electrolyte material solution:=72:28 to prepare a dispersion solution for cathode formation. The obtained dispersion was spray-printed onto the opposite side of the Nafion film on which the anode was formed to create a cathode (electrode catalyst layer) of a predetermined thickness on the Nafion film. Carbon paper was placed on the anode and cathode, respectively, and pressed under predetermined conditions (0.3kN, 130°C) to obtain the MEA of Example 1.

[0099] (Examples 2-4) The MEAs of Examples 2 to 4 were obtained in the same manner as in Example 1, except that the electrolyte material solutions of Examples 2 to 4 were used as the dispersion solution for cathode formation instead of the electrolyte material solution of Example 1.

[0100] (Comparative Example 1) As a comparative example, a conventional MEA was prepared using a cathode containing electrode material that does not contain the gas-permeable polymer PTMSDPA. The MEA of Comparative Example 1 was obtained in the same manner as in Example 1, except that the electrolyte material solution of Comparative Example 1 (Nafion dispersion) was used as the dispersion solution for cathode formation instead of the electrolyte material solution of Example 1.

[0101] <Electrochemical evaluation> The single-cell power generation evaluation fixtures incorporating the MEAs of Examples 1-4 and Comparative Example 1 were placed in a constant temperature bath set to 80°C, and the electrochemical evaluation of PEFCs (single cells) using the MEAs of Examples 1-4 and Comparative Example 1 was performed. The evaluation equipment used was a fuel cell evaluation device (Toyo Technica Co., Ltd., model number: PE-8900K) and a potentiometer / galvanostat (Solatron, model number: SI1287).

[0102] (Anode condition) Electrode area: 1cm 2 Supply gas type: H2 Gas supply rate: 139 mL / min (relative humidity: 95%) (Cathode condition) Electrode area: 1cm 2 Supply gas type: Air Gas supply rate: 332 mL / min (relative humidity: 95%)

[0103] Figures 3-5 show the electrochemical evaluation of PEFCs (single cells) using MEA in Examples 1-4 and Comparative Example 1. Note that in Figures 3 and 5, PTMSDPA is abbreviated as "ACE".

[0104] In the IV characteristics shown in Figure 3, compared to Comparative Example 1 (Naion212), Examples 1-3 show that the amount of gas supplied to the catalyst affects performance in the high current density region (1.3 A cm²). -2 The above results showed a high current density. As shown in Figure 4, the current density (A cm) at a cell voltage of 0.2V -2 When the samples were evaluated, Example 2 (PTMSDPA 2.5 wt%) showed the highest result at 1.59 A cm². -2 The results showed that in Examples 3 and 4, where PTMSDPA(ACE) was 2.5 wt% or higher, the water repellency of PTMSDPA(ACE) was lower than that of Nafion, resulting in lower water drainage capacity and reduced performance. Furthermore, in the concentration overpotential evaluation shown in Figure 5, Examples 1 to 3 showed lower values ​​compared to Comparative Example 1. Since concentration overpotential is a component caused by the amount of gas supplied to the catalyst and drainage, Example 2 (PTMSDPA 2.5 wt%), which had a good balance between gas permeability and water repellency, showed the lowest overpotential.

[0105] <Structural analysis> The electrolyte material (blended ionomer) solutions of Examples 1-4 and Comparative Example 1 shown in Table 1 were sprayed onto a polyvinylidene dichloridene substrate heated on a hot plate to obtain films for structural analysis. The obtained films were immersed in water for 60 minutes, and structural analysis was performed in the hydrated state by small-angle X-ray scattering (SAXS) and X-ray diffraction (XRD).

[0106] Small-angle X-ray scattering (SAXS) was performed at beamline BL-06 of the Kyushu Synchrotron Radiation Research Center in Saga Prefecture. The X-ray energy used was 9 keV (λ = 1.38065 Å), and the monochromator resolution was dE ~ 0.9 eV. The hydrophilic domain size d (nm) of Nafion (Comparative Example 1) and the electrolyte materials (blended ionomers) of Examples 1 to 4 was calculated using the following formula (A). d = 2π / q (A) Here, q is the scattering vector obtained from the SAXS results.

[0107] X-ray diffraction (XRD) measurements were performed using Cu Kα (1.5406 Å) with diffraction angles (2θ) in the range of 3° to 40°, using a SmartLab 9kW AMK X-ray diffractometer (Rigaku Corporation). The interplanar spacing of both Nafion blend ionomers was determined according to Bragg's equation (B) below. d = nλ / 2sinθ (B) Here, n is the order of diffraction, θ is the peak position, λ is the wavelength of the incident X-ray, and d is the interplane spacing.

[0108] Figure 6 shows the SAXS results for the electrolyte materials (blended ionomers) of Examples 1-4 and Nafion (Comparative Example 1), and Figure 7 shows the XRD results.

[0109] In SAXS evaluation, as shown in Figure 6, the q peak (1.2 nm), which exhibits a scattering vector characteristic of Nafion, shifted as the amount of PTMSDPA increased. This result confirmed that PTMSDPA was incorporated into the hydrophobic region, reducing the size of the hydrophilic domain. Furthermore, XRD evaluation showed that, as shown in Figure 7, the peak at the observed diffraction angle (2θ) shifted to a lower angle as the PTMSDPA mass fraction increased.

[0110] Figure 8 shows the relationship between the interplane spacing and hydrophilic domain size of the blended ionomers of Examples 1-4 and Comparative Example 1, as determined by formulas (A) and (B). As shown in Figure 8, it was confirmed that the interplanar spacing of the blended ionomer increased with increasing PTMSDPA mass fraction, while the hydrophilic domain size decreased with increasing PTMSDPA mass fraction.

[0111] From these results, it was found that PTMSDPA is incorporated into a portion of the hydrophobic region of Nafion, increasing the interplanar spacing in the blended ionomer, and that PTMSDPA compresses the hydrophilic domains of Nafion. Figure 9 shows a schematic diagram of Nafion and the blended ionomer (PTMSDPA + Nafion) based on the above structural analysis.

[0112] <Oxygen permeability test> Table 2 and Figure 10 show the oxygen permeability resistance (R) in the electrode catalyst layer of Examples 1-4 and Comparative Example 1. cL The experimental conditions and evaluation results are shown below. The oxygen permeability resistance in the electrode catalyst layer is expressed by equation (C). R total =R GDL +R CL (C) Here, R total The total oxygen permeability resistance of the catalyst layer, R GDL This is the oxygen permeability resistance of GDL, R CL is the oxygen permeability resistance of the catalyst layer. The partial pressure of oxygen in the cathode was changed with nitrogen, and the critical current density (current density at 0.2V) was measured. From the relationship between oxygen partial pressure and critical current density (D), R total Calculate the total pressure and R total From the oxygen permeability resistance R of the catalyst layer CL The result was calculated. i lim =(1 / R total )(nFP o2 (RT) (D) Here, i lim is the limiting current density, n is the number of electrons, F is the Faraday constant, P o2 θ is the partial pressure of oxygen, R is the gas constant, and T is the absolute temperature. Under the experimental conditions in Table 2, the limiting current density at different oxygen partial pressures was plotted, and the slope of the resulting graph was given by equation (D) = 1 / R total This is the result. Next, the same experiment was performed at different total pressures, and R was applied to the total pressure. total Plot the following. Since the resistance of GDL depends on the gas pressure, R at a total pressure of 0 kPa. total The value of (the Y-intercept of the graph) is R CL It corresponds to this.

[0113] [Table 2]

[0114] As shown in Figure 10, the electrode catalyst layer using a blend ionomer containing Nafion and PTMSDPA (Examples 1-4) has a higher oxygen permeability resistance (R) than when using Nafion alone (Comparative Example 1). cL Since all of these values ​​were small, it was confirmed that the oxygen permeability in the electrode catalyst layer was improved by including PTMSDPA. In particular, in Example 2 (PTMSDPA: 2.5 wt%), compared with Nafion alone (Comparative Example 1), R cL It had decreased by 38%. The electrochemical evaluation described above (Figures 3-5) showed that Example 2 (PTMSDPA 2.5 wt%) performed best, confirming that improving oxygen permeability in the electrode catalyst layer by including PTMSDPA contributes to improving electrode performance.

[0115] Furthermore, the oxygen permeability resistance in the electrode catalyst layer is the oxygen permeability resistance of the vacancies in the catalyst layer (R pore ) and the oxygen permeability resistance (R) of the ionomer coated between the vacancy and platinum. Pt It can be divided into ) and expressed as equation (E). R CL =R pore +R Pt (E) Amount of platinum in the cathode catalyst layer (L) O Change the settings as shown in Table 2, and R for each platinum amount. CL This value was calculated based on formula (F) L O 2 For R CL x L O When plotted, the oxygen permeability resistance (R) of the ionomer is used as the Y-intercept. Pt ) is calculated. R CL x L O = R pt + (R Pore x L O 2 ) / 3 (F) The calculated R Pt The oxygen permeability resistance was 0.93 s / m for Comparative Example 1, 0.53 s / m for Example 2, and 0.51 s / m for Example 4. Example 2 showed an oxygen permeability resistance 43% lower than that of Comparative Example 1. This confirms that the inclusion of PTMSDPA improves the oxygen permeability of the ionomer covering the catalyst, which contributes to the improvement of electrode performance. [Industrial applicability]

[0116] The electrodes of the present invention are suitable for PEFC electrodes and solid polymer water electrolysis devices that require operation at high current densities.

Claims

1. An electrode having an electrode catalyst layer comprising an electron-conductive catalyst support, electrode catalyst particles dispersed and supported on the surface of the catalyst support, and an electrolyte material covering the surfaces of the catalyst support and the electrode catalyst particles, wherein the electrolyte material is a blended ionomer obtained by mixing a non-proton-conducting gas-permeable polymer and a proton-conducting polymer, and the oxygen permeability of the non-proton-conducting gas-permeable polymer at 80°C is 100 Barre or more.

2. The electrode according to claim 1, wherein the aproton-conducting gas-permeable polymer is an aproton-conducting polysubstituted acetylene.

3. The electrode according to claim 2, wherein the aproton-conducting polysubstituted acetylene has a trimethylsilyl group in its side chain.

4. The electrode according to claim 3, wherein the aproton-conducting polysubstituted acetylene is poly[1-phenyl-2-[p-(trimethylsilyl)phenyl]acetylene.

5. The electrode according to claim 1, which is for use in a polymer electrolyte fuel cell or a polymer electrolyte water electrolysis device.

6. A membrane electrode assembly comprising a solid polymer electrolyte membrane, a cathode bonded to one side of the solid polymer electrolyte membrane, and an anode bonded to the other side of the solid polymer electrolyte membrane, wherein at least one of the cathode and the anode is the electrode described in any one of claims 1 to 5.

7. A polymer electrolyte fuel cell comprising the membrane electrode assembly described in claim 6.

8. A blended ionomer containing a gas-permeable polymer obtained by mixing a non-proton-conducting gas-permeable polymer and a proton-conducting polymer, wherein the oxygen permeability of the non-proton-conducting gas-permeable polymer at 80°C is 100 Barre or more.

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