Catalyst, method for producing catalyst, electrode, ion exchange membrane-electrode assembly, and various electrolysis devices

Abstract

The present invention provides an electrode catalyst having improved hydrophobic performance of the carrier, a method for producing this electrode catalyst, an electrode that uses this electrode catalyst, an ion exchange membrane-electrode assembly, and various electrolysis devices.　The electrode catalyst comprises a carrier containing carbon, and inorganic particles and / or a metal complex supported on the carrier. The volatile content of the carrier is 0.7% or less.

Description

Catalyst, its manufacturing method, electrode, ion exchange membrane-electrode assembly, and various electrolysis devices

[0001] The present invention relates to a catalyst and a method for producing the same, as well as an electrode, an ion-exchange membrane-electrode assembly, and various electrolysis devices that use the catalyst.

[0002] Research into carbon dioxide reduction using electrical energy is being conducted worldwide. Among carbon dioxide reduction devices, polymer electrolyte electrolysis cells with membrane electrode assemblies (MEAs) have been found to be superior to other devices in that they can directly reduce gaseous carbon dioxide and use a thin-film polymer electrolyte to sufficiently reduce ion migration resistance.

[0003] Because the ion exchange membrane of the MEA has the property of permeating not only ions but also electrolytes due to its structure, a small amount of electrolyte supplied to the anode often permeates the ion exchange membrane, resulting in excess moisture inside the cathode catalyst layer. This phenomenon has adverse effects such as interfering with the supply of carbon dioxide to the cathode catalyst, resulting in a decrease in electrolytic performance such as current density and selectivity.

[0004] As a method for controlling the moisture content of the catalyst layer, a method of adding a polymer to the catalyst layer has been reported (see, for example, Patent Document 1).

[0005] Patent Document 1 discloses an invention in which a metal electrode body is provided with a modification layer containing a hydrophobic polymer such as polystyrene in a reduction reaction electrode used in a reduction reaction of a carbon compound, thereby making it possible to at least one of suppressing the rate of hydrogen production due to a side reaction in the reduction reaction of the carbon compound and improving the rate of production of a reduction product in the reduction reaction of the carbon compound.

[0006] Japanese Patent Application Laid-Open No. 2021-21095

[0007] However, since the hydrophobicity of the support used in the electrode catalyst is not improved, there is a problem that the effect of suppressing the deterioration of electrode performance is likely to be insufficient.

[0008] Therefore, an object of the present invention is to provide an electrode catalyst in which the hydrophobicity of the support itself is improved, a method for producing the same, and an electrode, an ion exchange membrane-electrode assembly, and various electrolysis devices that use the catalyst.

[0009] In order to achieve the above object, the present invention provides the following catalyst and its production method, as well as an electrode, an ion-exchange membrane-electrode assembly, and various electrolysis devices that use the catalyst.Furthermore, the present invention provides the following fuel cell.

[0010] [1] An electrode catalyst comprising a carbon-containing support and inorganic fine particles and / or a metal complex supported on the support, wherein the support has a volatile content of 0.7% or less. [2] The electrode catalyst according to [1], wherein the support has an X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu-Kα radiation at 25°C, in which the half-width of an X-ray diffraction peak (X-ray diffraction peak corresponding to the (002) plane of graphite) having the highest intensity within a diffraction angle range of 20° to 30° is 5° or less. [3] The electrode catalyst according to [1] or [2], wherein the support has a crystallite size La of 5 nm or more of a six-membered ring plane of graphite. [4] The electrode catalyst has a water vapor adsorption amount of 30 cm at 25°C and a relative humidity of 70%. ３(STP) / g or less. [5] The electrocatalyst according to any one of [1] to [3], wherein the inorganic fine particles are fine particles of one or more types selected from the group consisting of gold, silver, copper, nickel, iron, cobalt, zinc, chromium, palladium, tin, manganese, aluminum, indium, bismuth, molybdenum, platinum, ruthenium, rhodium, iridium, and carbon nitride. [6] The electrocatalyst according to any one of [1] to [5], wherein the metal complex is one or more types of metal complexes in which a ligand is coordinated to a metal selected from the group consisting of copper, nickel, iron, cobalt, zinc, manganese, molybdenum, and aluminum, or an ion of the metal. [7] The electrocatalyst according to any one of [1] to [6], wherein the support contains one or more elements selected from the group consisting of nitrogen, oxygen, sulfur, selenium, boron, and phosphorus. [8] The electrode catalyst according to any one of [1] to [7], wherein the support has nitrogen on its surface, and the inorganic fine particles and / or the metal complex are supported on the support via the nitrogen. [9] The electrode catalyst according to any one of [1] to [8], wherein the inorganic fine particles are fine particles made of one metal element selected from the group consisting of gold, silver, copper, nickel, iron, cobalt, zinc, chromium, palladium, tin, manganese, aluminum, indium, bismuth, molybdenum, platinum, ruthenium, rhodium, and iridium.

[10] The electrode catalyst according to any one of [1] to [9], wherein the metal complex is made of one metal element selected from the group consisting of copper, nickel, iron, cobalt, zinc, manganese, molybdenum, and aluminum.

[11] The electrode catalyst according to [9] or

[10] , wherein the one metal element is nickel.

[12] The electrode catalyst according to any one of [1] to

[11] , wherein the electrode catalyst has an average particle size of more than 10 nm and not more than 200 nm.

[13] The method for producing the electrode catalyst according to any one of [1] to

[12] , wherein the water vapor adsorption amount at 25°C and a relative humidity of 95% is 25 cm ３(STP) / g or less, and raw materials for the inorganic fine particles and / or the metal complex.

[14] A method for producing an electrode catalyst according to

[13] above, wherein the mixing step further comprises mixing a nitrogen-containing compound.

[15] A catalyst layer comprising at least the electrode catalyst according to any one of [1] to

[12] above and a binder resin.

[16] An electrode comprising at least the catalyst layer according to

[15] above and a gas diffusion layer.

[17] An ion exchange membrane-electrode assembly comprising the electrode according to

[16] above.

[18] The ion exchange membrane-electrode assembly according to

[17] above, wherein the ion exchange membrane comprises an anion exchange membrane.

[19] A carbon dioxide reduction electrolysis device comprising the ion exchange membrane-electrode assembly according to

[17] or

[18] above.

[20] A water electrolysis device comprising the ion exchange membrane-electrode assembly according to

[17] or

[18] above.

[21] An ammonia electrolytic synthesis device comprising the ion exchange membrane-electrode assembly according to

[17] or

[18] .

[22] A fuel cell comprising the ion exchange membrane-electrode assembly according to

[17] or

[18] .

[0011] According to the present invention, it is possible to provide an electrode catalyst in which the hydrophobicity of the support itself is improved, a method for producing the same, and an electrode, an ion exchange membrane-electrode assembly, and various electrolysis devices that use the catalyst.

[0012] 1 is a graph showing the water vapor adsorption amounts of Examples and Comparative Examples. It is an explanatory diagram showing a method for measuring the half-width of the X-ray diffraction peak corresponding to the (002) plane of the graphite-like structure in carbon black. It is a chart showing the X-ray diffraction peak corresponding to the (110) plane of the graphite-like structure in the carbon black used in Example 1. It is a chart showing the X-ray diffraction peak corresponding to the (002) plane of the graphite-like structure in the carbon black used in Example 1.

[0013] The following describes in detail the embodiments of the present invention (hereinafter referred to as "the present embodiments"); however, the present invention is not limited to these embodiments, and various modifications are possible without departing from the spirit of the present invention.

[0014] In this specification, unless otherwise specified, a numerical range of "X (lower limit) to Y (upper limit)" means "X or more and Y or less." Furthermore, when multiple numerical ranges are described, the lower limit and upper limit of each numerical range can be combined in any way.

[0015] [Electrode catalyst] The electrode catalyst according to this embodiment includes a support containing carbon and inorganic fine particles and / or a metal complex supported on the support, and the support has a volatile content of 0.7% or less.

[0016] (Support) The electrode catalyst according to this embodiment includes a support, and the support includes carbon. Carbon is usually conductive, and therefore a support including carbon is a conductive support. Examples of carbon include carbon black (furnace black, acetylene black, ketjen black, medium thermal carbon black, etc.), activated carbon, graphite, carbon nanotubes, carbon nanofibers, carbon nanohorns, graphene nanoplatelets, nanoporous carbon, etc., and among these, carbon black is preferred from the viewpoint of improving the active site density.

[0017] The support used has a volatile content of 0.7% or less. Here, the volatile content refers to the amount of volatilization (weight loss) when the support is heated at 950°C for 7 minutes. The volatile content is preferably 0.5% or less, more preferably 0.4% or less or 0.35% or less, and even more preferably 0.3% or less or 0.25% or less. Alternatively, it is also preferable that the volatile content is 0.2% or less. The lower limit of the volatile content is preferably a value in the range of 0 to 0.1%, and is preferably, for example, 0.01%, 0.05%, or 0.1%. This results in an electrode catalyst with improved hydrophobicity of the support itself.

[0018] In this specification, the volatile content can be measured, for example, in accordance with JIS M 8812 (2006) "Coals and Cokes" as follows. Specifically, a sample is heated to 900°C or 950°C without contacting with air, and the volatile content is calculated by subtracting the moisture value from the weight loss after 7 minutes. In this embodiment, 950°C was used.

[0019] In an X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu-Kα radiation at 25°C, the support preferably has an X-ray diffraction peak (corresponding to the (002) plane of graphite) with the highest intensity within a diffraction angle range of 15° to 35°, preferably 20° to 30°, with a half-width of 5° or less, more preferably 4° or less or 3° or less, even more preferably 2.5° or less or 2° or less, and most preferably 1.9° or less or 1.8° or less. The lower limit of the half-width is preferably a value in the range of 0 to 1°, and is preferably 0.1°, 0.5°, or 1°, for example. This makes it easier to obtain an electrode catalyst with improved hydrophobicity of the support itself. In this embodiment, the "(002) plane of graphite" includes not only the (002) plane of graphite, but also the (002) plane of a graphite-like structure and the (002) plane of a quasi-graphite structure.

[0020] In this specification, the FWHM can be measured as follows. That is, the FWHM is measured based on the peak shape obtained from an X-ray diffraction (XRD) pattern. The general measurement procedure is as follows: First, a region including the target diffraction peak (e.g., a peak corresponding to the (002) plane in a graphite-like structure) is identified on the XRD chart. Next, as shown in Figure 2, a straight line (baseline) is drawn between two points in the background region on either side of the peak (e.g., 2θ = 15° ± 2° and 35° ± 2°). This baseline is used as a reference for the relative intensity from the peak top. Next, an auxiliary line is drawn perpendicular to this baseline from the peak top, and the position on the perpendicular line where the intensity is half (50%) is determined. The difference in 2θ angle between the two obtained points is the FWHM of the peak. In actual measurements, XRD analysis software is generally used to smooth the peak and remove noise, and then the FWHM is automatically calculated. For example, a B-spline function is used for smoothing, and measurement accuracy can be improved by setting appropriate parameters. Typical conditions for X-ray diffraction measurement are, for example, using a MiniFlex600 (trade name) manufactured by Rigaku Holdings Corporation, at a room temperature of 25° C., using Cu-Kα radiation (wavelength λ=1.5405 Å, tube voltage 40 kV, tube current 15 mA). Analysis software (PDXL (trade name)) manufactured by the same company can be used for the analysis.

[0021] The support preferably has a crystallite size La of the six-membered ring plane of graphite of 5 nm or more, more preferably 5.5 nm or more, and even more preferably 6 nm or more. The upper limit of the crystallite size La is preferably 30 nm, for example, 7 nm, 10 nm, or 15 nm. This makes it easier to obtain an electrode catalyst with improved hydrophobicity of the support itself. In this embodiment, the "six-membered ring plane of graphite" includes not only the six-membered ring plane of graphite, but also the six-membered ring plane of a graphite-like structure and the six-membered ring plane of a quasi-graphite structure. The crystallite size La in the present invention can be obtained, for example, by the measurement and calculation methods described in the Examples below, but can also be replaced by any method that obtains an equivalent value.

[0022] In this specification, the crystallite size La can be measured as follows. That is, the crystallite size (La) is calculated using the Scherrer formula from the diffraction peak width (half-width) and diffraction angle obtained by X-ray diffraction (XRD). The general measurement procedure is as follows. First, X-ray diffraction measurements of the target sample are performed using an X-ray diffractometer (e.g., MiniFlex600 manufactured by Rigaku Holdings Co., Ltd.). Measurement conditions include Cu-Kα radiation (wavelength λ = 1.5405 Å), a tube voltage of 40 kV, and a tube current of 15 mA. Measurement is performed in step scan mode, with the scan speed and slit size appropriately set. The temperature is generally room temperature (25°C). From the obtained X-ray diffraction pattern, the diffraction peak with the highest intensity within a specified angle range (e.g., 2θ = 75° to 80°) is selected, and its half-width (β) is measured. A fitting method is used to remove the background, and second-order differential methods are used to detect the peak. Based on the diffraction angle (θ) and half-width (β) of the selected diffraction peak, the crystallite size La is calculated by the following Scherrer formula (formula (1) below). where, La: crystallite size (nm) K: Scherrer constant (usually about 0.9) λ: X-ray wavelength (1.5405 Å) β: peak half-width (radian) θ: diffraction angle (degrees)

[0023] The support preferably has an average particle diameter of more than 10 nm and not more than 200 nm, more preferably 15 to 100 nm, and even more preferably 20 to 50 nm. This makes it easier to obtain an electrode catalyst with improved hydrophobicity of the support itself. Note that the average particle diameter in the present invention refers to the arithmetic mean diameter determined by observing support particles (e.g., carbon black particles) under an electron microscope, but can also be replaced by a method that provides an equivalent value.

[0024] The catalyst (inorganic fine particles and / or metal complex) supported on the support is small, for example, nickel fine particles are very small, so the average particle size of the electrode catalyst according to this embodiment is also approximately the same as the average particle size of the support. That is, the average particle size of the electrode catalyst according to this embodiment is preferably greater than 10 nm and not greater than 200 nm, more preferably 15 to 100 nm, and even more preferably 20 to 50 nm.

[0025] The carrier has a water vapor adsorption capacity of 25 cm at 25°C and a relative humidity of 70%. ３ (STP) / g or less, and ３ (STP) / g or less or 15 cm ３ (STP) / g or less is more preferable, and ３ (STP) / g or less or 5 cm ３ (STP) / g or less is more preferable, and ３ (STP) / g or less, 3cm ３ (STP) / g or less, 2cm ３ (STP) / g or less or 1.5 cm ３ It is most preferable that the solubility is (STP) / g or less.

[0026] Commercially available products can be used as the support material, such as #4000B (manufactured by Mitsubishi Chemical) or TOKABLACK #3845 (manufactured by Tokai Carbon). On the other hand, VULCAN (registered trademark) XC-72R (manufactured by CABOT), a product commonly used for electrode catalysts, does not satisfy the above conditions. Only one type of support may be used, or two or more types may be used in combination.

[0027] The support may contain one or more elements selected from the group consisting of nitrogen, oxygen, sulfur, selenium, boron, and phosphorus. Among these elements, nitrogen is preferably contained. The nitrogen is preferably nitrogen derived from a nitrogen-containing compound. These elements may be incorporated into the support or may be present on the surface of the support. For example, an embodiment in which the catalyst (inorganic fine particles and / or metal complex) is supported on the support via nitrogen present on the surface of the support is cited as a preferred example.

[0028] (Inorganic fine particles, metal complex) The electrode catalyst according to this embodiment contains inorganic fine particles and / or metal complexes, which may be simply referred to as catalysts. The inorganic fine particles and metal complexes are not particularly limited as long as they exhibit catalytic activity.

[0029] Examples of inorganic fine particles include fine particles of one or more types selected from the group consisting of gold, silver, copper, nickel, iron, cobalt, zinc, chromium, palladium, tin, manganese, aluminum, indium, bismuth, molybdenum, platinum, ruthenium, rhodium, iridium, and carbon nitride. Appropriate fine particles can be selected depending on the intended use of the electrode catalyst. For example, when used in a carbon dioxide reduction electrolysis device, fine particles of one or more types selected from the group consisting of gold, silver, copper, nickel, iron, cobalt, zinc, chromium, palladium, tin, manganese, aluminum, indium, bismuth, molybdenum, and carbon nitride are preferred.

[0030] The inorganic fine particles are preferably fine particles made of one metal element selected from the group consisting of gold, silver, copper, nickel, iron, cobalt, zinc, chromium, palladium, tin, manganese, aluminum, indium, bismuth, molybdenum, platinum, ruthenium, rhodium, and iridium, and are more preferably nickel fine particles.

[0031] The average particle size of the fine particles is not particularly limited, but for example, from the viewpoint of the reaction rate of the carbon dioxide reduction reaction, the average particle size of inorganic fine particles as a catalyst for carbon dioxide reduction is preferably 65 nm or less, preferably 60 nm or less, preferably 50 nm or less, preferably 40 nm or less, and preferably 30 nm or less. Furthermore, there is no restriction on the lower limit of the average particle size, but from the viewpoint of ease of production, it is preferably 1 nm or more, more preferably 2 nm or more. The average particle size can be measured by photographic observation using a scanning electron microscope or the like.

[0032] Examples of the metal complex include one or more metal complexes in which a ligand is coordinated to a metal selected from the group consisting of copper, nickel, iron, cobalt, zinc, manganese, molybdenum, and aluminum, or an ion of the metal. An appropriate metal complex can be selected depending on the intended use of the electrode catalyst.

[0033] The metal complex is preferably a metal complex containing one metal element selected from the group consisting of copper, nickel, iron, cobalt, zinc, manganese, molybdenum, and aluminum, and more preferably a nickel complex.

[0034] The type of ligand is not particularly limited, and examples thereof include phthalocyanine complexes, porphyrin complexes, pyridine complexes, metal-supported covalently bonded triazine structures, and metal-organic structures. Among these, phthalocyanine complexes, porphyrin complexes, pyridine complexes, and metal-supported covalently bonded triazine structures are preferred, phthalocyanine complexes, porphyrin complexes, and metal-supported covalently bonded triazine structures are more preferred, and porphyrin complexes and metal-supported covalently bonded triazine structures are even more preferred. The metal complex may contain only one type of ligand, or may contain two or more types.

[0035] The inorganic fine particles and metal complexes can be supported on the carrier by carrying out known methods such as vapor deposition, deposition, adsorption, accumulation, adhesion, welding, physical mixing, and spraying.

[0036] The electrode catalyst according to this embodiment has a water vapor adsorption capacity of 30 cm at 25°C and a relative humidity of 70%. ３ (STP) / g or less, and ３ (STP) / g or less or 22 cm ３ (STP) / g or less is more preferable, and 20 cm ３ (STP) / g or less or 18 cm ３ (STP) / g or less, and more preferably 17 cm ３ (STP) / g or less, 16cm ３ (STP) / g or less, 15cm ３ (STP) / g or less or 14 cm ３ It is most preferable that the solubility is (STP) / g or less.

[0037] [Method for producing an electrode catalyst] The method for producing an electrode catalyst according to this embodiment is a method for producing an electrode catalyst according to the embodiment, and includes a mixing step of mixing the support with raw materials for the inorganic fine particles and / or the metal complex. The support has a water vapor adsorption of 25 cm at 25°C and a relative humidity of 95%. ３ (STP) / g or less, and ３ (STP) / g or less or 15 cm ３ (STP) / g or less is more preferable, and ３ (STP) / g or less or 5 cm ３ (STP) / g or less is more preferable, and ３ (STP) / g or less, 3cm ３ (STP) / g or less, 2cm ３ (STP) / g or less or 1.5 cm ３ (STP) / g or less is most preferable. Other production conditions and steps can be carried out in accordance with known production methods.

[0038] The mixing step is preferably a step of further mixing a nitrogen-containing compound. The nitrogen-containing compound is not particularly limited and examples thereof include pentaethylenehexamine, tetraethylenepentamine, triethylenepentamine, diethylenetriamine, ethylenediamine, diethylamine, etc. From the viewpoint of improving electrolytic activity, pentaethylenehexamine, tetraethylenepentamine, and triethylenepentamine are preferred, and pentaethylenehexamine and tetraethylenepentamine are more preferred.

[0039] The content of the nitrogen-containing compound in the material of the electrode catalyst according to this embodiment is preferably 5 to 75 mass %, more preferably 10 to 60 mass %, and even more preferably 20 to 50 mass %, from the viewpoint of improving the active site density.

[0040] [Catalyst Layer] The catalyst layer according to this embodiment is a catalyst layer containing at least the electrode catalyst according to this embodiment and a binder resin.

[0041] An ionomer can be used as the binder resin. From the viewpoint of improving conductivity, the ionomer is preferably a polymer electrolyte. The polymer electrolyte is more preferably an ion exchange resin. The ion exchange resin may be a cation exchange resin or an anion exchange resin, but is preferably an anion exchange resin. When an anion exchange resin is used, the anion exchange resin itself has the ability to adsorb carbon dioxide, which, together with the ease of ion transfer of the ion exchange resin, makes it possible to greatly improve the efficiency of carbon dioxide electrolysis.

[0042] Examples of cation exchange resins include fluororesins having sulfonic groups and styrene-divinylbenzene copolymers having sulfonic groups. Commercially available products can also be used, such as Nafion (manufactured by Chemours), Aquivion (manufactured by Solvay Specialty Polymers), DIAION (manufactured by Mitsubishi Chemical Corporation), and Fumasep (manufactured by FUMATECH).

[0043] Examples of anion exchange resins include resins having one or more ion exchange groups selected from the group consisting of quaternary ammonium groups, primary amino groups, secondary amino groups, and tertiary amino groups. Commercially available products can also be used, such as Sustainion (manufactured by Dioxide Materials), Fumasep (manufactured by FUMATECH), PENTION (manufactured by Xergy), DURION (manufactured by Xergy), NEOSEPTA (manufactured by Astom), and TOYOPEARL (manufactured by Tosoh).

[0044] When an electrode having a catalyst layer according to this embodiment is used as a cathode in a carbon dioxide reduction electrolysis device, it is preferable to use the same resin as that used in the solid electrolyte (ion exchange membrane) of the ion exchange membrane-electrode assembly as the binder resin, from the viewpoint of improving electrical conductivity.

[0045] When an electrode having a catalyst layer according to this embodiment is used as a cathode of a water electrolysis apparatus, an ammonia electrosynthesis apparatus, or a fuel cell, it is preferable to use the same ion exchange resin as that of the ion exchange membrane as the binder resin, from the viewpoint of reducing ion migration resistance.

[0046] The catalyst layer according to this embodiment can be produced according to a known production method, except that the electrode catalyst according to this embodiment is used.

[0047] [Electrode] The electrode according to this embodiment is an electrode that has at least the catalyst layer according to this embodiment and a gas diffusion layer.

[0048] The gas diffusion layer may be made of, for example, carbon paper, nonwoven fabric, metal mesh, etc. Examples of materials for these layers include graphite carbon, glassy carbon, titanium, and SUS steel.

[0049] The electrode according to this embodiment can be manufactured according to a known manufacturing method, except that the catalyst layer according to this embodiment is used.

[0050] [Ion Exchange Membrane-Electrode Assembly] The ion exchange membrane-electrode assembly according to this embodiment is an ion exchange membrane-electrode assembly having the electrode according to the embodiment described above. The ion exchange membrane may be a commercially available product as a cation exchange membrane or an anion exchange membrane. It is preferable that the ion exchange membrane includes an anion exchange membrane.

[0051] From the viewpoint of reducing ionic resistance, the ion exchange membrane preferably has an average thickness in a dry state of 60 μm or less. From the viewpoint of preventing pinhole formation, the average thickness in a dry state is preferably 10 μm or more. From the viewpoint of a balance between ionic resistance and pinhole prevention, the average thickness of the ion exchange membrane in a dry state is more preferably 15 to 50 μm, and even more preferably 20 to 40 μm.

[0052] When an anion exchange membrane is used as the ion exchange membrane, the basic site density is 0.5 to 5.0 mmol / cm in a dry state. ３ and preferably 2.5 mmol / cm ３ Above, 4.5 mmol / cm ３ More preferably, it is less than 2.9 mmol / cm ３ Above, 4.5 mmol / cm ３ It is more preferable that it is less than 10 ...

[0053] Examples of the cation exchange membrane that can be used include strongly acidic cation exchange membranes in which sulfonic groups have been introduced into a fluororesin matrix, such as Nafion 117, Nafion 115, Nafion 212, and Nafion 350 (manufactured by Chemrous Corporation), and strongly acidic cation exchange membranes in which sulfonic groups have been introduced into a styrene-divinylbenzene copolymer matrix, such as Neosepta CSE (manufactured by Astom Corporation).

[0054] Examples of anion exchange membranes include those having one or more ion exchange groups selected from the group consisting of quaternary ammonium groups, primary amino groups, secondary amino groups, and tertiary amino groups. Specific examples include Neosepta (registered trademark) ASE, AHA, ACS, and AFX (manufactured by Astom Corporation), and Selemion (registered trademark) AMVN, DSVN, AAV, ASVN, and AHO (manufactured by Asahi Glass Co., Ltd.).

[0055] The ion exchange membrane-electrode assembly according to this embodiment can be produced according to a known production method, except that the electrode according to this embodiment is used.

[0056] The ion exchange membrane-electrode assembly according to this embodiment includes an electrode having the catalyst layer according to this embodiment, and therefore does not interfere with the carbon dioxide reduction reaction in the catalyst layer, allowing stable production of synthesis gas containing CO. Therefore, the electrolysis efficiency of the carbon dioxide electroreduction reaction is excellent.

[0057] The ion exchange membrane-electrode assembly according to this embodiment can be applied not only to carbon dioxide reduction electrolysis, but also to water electrolysis, nitrogen electrolysis (ammonia electrosynthesis), and the like, which similarly require hydrophobicity.

[0058] [Electrolysis Device] The electrolysis device according to this embodiment is a carbon dioxide reduction electrolysis device including the ion exchange membrane-electrode assembly according to the embodiment described above.

[0059] The electrolysis device according to this embodiment is a water electrolysis device including the ion exchange membrane-electrode assembly according to the embodiment.

[0060] The electrolysis device according to this embodiment is an ammonia electrolysis device including the ion exchange membrane-electrode assembly according to the embodiment.

[0061] The electrolytic device according to this embodiment can be manufactured according to a known manufacturing method, except that the ion exchange membrane-electrode assembly according to this embodiment is used.

[0062] [Fuel Cell] The fuel cell according to this embodiment is a fuel cell including the ion exchange membrane-electrode assembly according to the embodiment described above.

[0063] The fuel cell according to this embodiment can be manufactured according to a known manufacturing method, except that the ion exchange membrane-electrode assembly according to this embodiment is used.

[0064] The present invention will now be described with reference to examples, but the present invention is not limited to these examples.

[0065] [Production of Cathode Electrode Catalyst] 0.4 g of a support (carbon black) from any of Examples 1 to 3 and Comparative Examples 1 to 3 below, 1.1 mmol of pentaethylenehexamine, and 0.7 mmol of nickel(II) chloride hexahydrate were added to 15 mL of ethanol in a beaker and mixed. The resulting ethanol dispersion was then irradiated with ultrasound for 10 minutes. The ethanol dispersion was then heated and dried to evaporate the ethanol, and the resulting mixture was calcined in an inert gas atmosphere at 900°C for 10 seconds or more using a calcination furnace. The calcined product was then washed with an aqueous sulfuric acid solution, and the solid was recovered using a suction filter. The solid was then vacuum-dried at 60°C overnight to obtain a catalyst powder (intermediate) in which the nickel complex (catalyst) was supported on the support.

[0066] 0.3 g of the obtained catalyst powder was placed in a pot together with 10 g of zirconia balls with a diameter of 0.5 mm and 10 mL of water, and treated for 20 minutes at a rotation speed of 800 rpm using a planetary ball mill to recover a catalyst slurry. The catalyst slurry was washed with an aqueous sulfuric acid solution, and the solid matter was recovered using a suction filter. The solid matter was vacuum-dried at 60°C overnight to obtain the final catalyst powders (cathode electrode catalysts) of Examples 1 to 3 and Comparative Examples 1 to 3.

[0067] <Carbon black used> Example 1: Mitsubishi Chemical, product name #4000B Example 2: Tokai Carbon, product name TOKABLACK #3845 Example 3: Tokai Carbon, product name TOKABLACK #3855 Comparative Example 1: Cabot, product name VULCAN (registered trademark) XC-72R Comparative Example 2: Mitsubishi Chemical, product name #3400B Comparative Example 3: Tokai Carbon, product name TOKABLACK #5500

[0068] The volatile content [%] and average particle size [nm] of the support are transcribed from the product catalog in Table 1. The volatile content [%] is a value obtained by referring to JIS M 8812. The crystallite size (La) [nm] and XRD half width [°] of the support are also shown in Table 1, which were determined according to the following method. The X-ray diffraction peaks of the (110) and (002) planes of the "carbon black having a graphite-like structure" (#4000B (trade name) manufactured by Mitsubishi Chemical) used in Example 1 are shown in Figures 3 and 4, respectively. Furthermore, the water vapor adsorption amounts [cm] of the support (before catalyst loading) and the final catalyst powder (cathode electrode catalyst) were also measured. ３ (STP) / g] was measured according to the following method, and the amount of water vapor adsorption at a relative humidity of 70% is shown in Table 1.

[0069] (Crystallite size (La)) X-ray diffraction measurement was performed under the following conditions using an X-ray diffractometer (MiniFlex600 (trade name) manufactured by Rigaku Holdings Corporation), and the X-ray diffraction peak with the highest intensity within the diffraction angle range of 75° to 80° in the obtained X-ray diffraction pattern was measured. The crystallite size La was calculated using the angle of the obtained X-ray diffraction peak and Scherrer's formula (formula (1) below). In formula (1), K is the Scherrer constant, λ is the measured X-ray wavelength, β is the half-width, and θ is the diffraction angle (the angle of the X-ray diffraction peak with the highest intensity within the diffraction angle range of 75° to 80°).

[0070] (X-ray diffraction measurement conditions) Radiation source: Cu-Kα radiation (λ=1.5405 Å) Tube voltage, tube current: 40 kV, 15 mA Measurement mode: step scan Scan conditions: 5° / min Measurement range: 2θ=3° to 100° Distance to detector (goniometer radius): 150 mm Soller slit: 13.0 mm Divergence / entrance slit: 13.0 mm Receiving slit: open Receiving Soller slit: 5.0° Detector: high-performance multipurpose powder diffraction analyzer (D / Tex Ultra2 (trade name) manufactured by Rigaku Holdings Co., Ltd.), one-dimensional semiconductor element Measurement temperature: 25°C Background removal: fitting method Peak width threshold: 1.00 Intensity threshold: 10.00 Peak search: second-order differential method σ cut value: I / σ>3.0

[0071] (XRD Half-Width) X-ray diffraction measurement was performed at 25°C using an X-ray diffractometer (MiniFlex600 (trade name) manufactured by Rigaku Holdings Co., Ltd.) using Cu-Kα radiation (tube voltage 40 kV, tube current 15 mA). In the obtained X-ray diffraction pattern, the half-width of the X-ray diffraction peak having the highest intensity within the diffraction angle range of 20° to 30° (the X-ray diffraction peak corresponding to the (002) plane of the graphite-like structure in carbon black) was measured. The measurement conditions for X-ray diffraction were the same as those for the above-mentioned "crystallite size (La)." Analysis software (PDXL (trade name) manufactured by Rigaku Holdings Co., Ltd.) was used to calculate the half-width. The analysis software conditions are as follows: (Analysis Software Conditions) Smoothing: B-spline smoothing Smoothing parameter: 10.00 Smoothing points: 11 X threshold: 1.5

[0072] (Water Vapor Adsorption Amount) For the carrier before catalyst loading and the carrier with catalyst loaded (i.e., electrode catalyst), the water vapor adsorption amount at 25°C and a water vapor pressure of 3.1 kPa (saturated water vapor pressure) at 25°C was measured using a BELSORP-max (manufactured by BEL Japan). In the measurement, 0.2 to 0.3 g of sample was heated at 120°C for 5 hours or more under vacuum conditions to remove any adsorbed gas on the surface, and then water vapor was introduced at 25°C to determine the water vapor adsorption amount. Figure 1 shows a graph plotting the water vapor adsorption amount versus relative pressure for the carrier before catalyst loading. Here, the relative pressure on the horizontal axis in Figure 1 means the value obtained by dividing the water vapor pressure at each measurement point by the saturated water vapor pressure (3.1 kPa) at 25°C. This can be expressed as the following formula: Relative pressure = (water vapor pressure at each measurement point) / (saturated water vapor pressure [= 3.1 kPa]) In Fig. 1, when the relative pressure on the horizontal axis is 0.7, this means that the relative pressure = 2.2 / 3.1. Since a relative pressure of 0.7 is synonymous with "relative humidity of 70%," the water vapor adsorption amount on the vertical axis when the relative pressure on the horizontal axis is 0.7 is the water vapor adsorption amount at a relative humidity of 70% listed in Table 1.

[0073] It was confirmed that the carriers of Examples 1 to 3 had a small amount of water vapor adsorption and were highly hydrophobic, both before and after catalyst loading.

[0074] [Production of cathode] 22 mg of the obtained catalyst powder was dispersed in ethanol, and 2 mg of a binder resin (cation exchange resin: Nafion (registered trademark) DE2020, manufactured by Chemours) was added to the dispersion as a binder and mixed to prepare a catalyst dispersion. The catalyst dispersion was subjected to ultrasonic treatment for 10 minutes and exposed to a reduced pressure environment of 10 kPa (absolute pressure) in a vacuum chamber for 10 minutes. The treated catalyst dispersion was sprayed onto a gas diffusion layer equipped with a microporous layer using a spray coater so that the supported amount when dried was 1 to 2 mg / cm. ２ The cathodes of Examples 1 to 3 and Comparative Examples 1 to 3 were manufactured by coating the catalyst layer so as to form a catalyst layer.

[0075] [Production of Anode] An iridium oxide catalyst (manufactured by Heraeus) and a binder resin (cation exchange resin: Nafion (registered trademark) DE2020, manufactured by Chemours) were mixed in a solid mass ratio of catalyst:binder resin = 7:1 to obtain a mixture. The mixture was dispersed in an isopropanol-water mixture to prepare a catalyst dispersion. A titanium particle aggregate sheet (manufactured by Toho Titanium Co., Ltd., WEBTi (registered trademark), porosity 61% (catalog value)) was used as the substrate layer. 100 titanium particles contained in the aggregate sheet were randomly selected, and the major axis diameter (a) and minor axis diameter (b) were measured using a scanning electron microscope. The number average value of the b / a value (aspect ratio) was 2. In addition, in photographic observation of the surface of the substrate layer using a scanning electron microscope, the openings were approximated to an ellipse for 100 randomly selected openings, and the major axis of the openings was measured, yielding an average value of 15 μm. The substrate layer was heated to 90° C., and a catalyst dispersion mixed with pressurized air was sprayed onto the substrate layer in a mist form from a spray device to form a catalyst layer, thereby producing an anode commonly used in all Examples and Comparative Examples. The catalyst dispersion was sprayed at a concentration of 2 mg / cm2 so that the supported amount of catalyst and binder resin (total amount of catalyst and binder resin) was 2 mg / cm2. ２ The spraying was stopped when the temperature reached 100°C. The spraying device used was an externally mixed two-fluid nozzle (manufactured by Apiros Co., Ltd., product name "LPVN (registered trademark) 10").

[0076] [Production of Ion Exchange Membrane-Electrode Assemblies] An anion exchange membrane having a thickness of approximately 30 μm was attached to the produced cathode and anode, and then pressure-bonded to produce ion membrane-electrode assemblies of Examples 1 to 3 and Comparative Examples 1 to 3. The anion exchange membrane used was made of a fluorine-based resin (basic site density 2.1 mmol / cm) having an aromatic ring in the main chain and quaternary ammonium groups bonded to the main chain as side chains. ３ ) is a membrane based on the substrate.

[0077] [Evaluation of Electrolysis Efficiency of Carbon Dioxide Reduction Electrolysis Device] (1) Measurement of CO Generation Current Density In the ion exchange membrane-electrode assemblies of Examples 1 to 3 and Comparative Examples 1 to 3, each anode was filled with an electrolyte (0.5 mol / L KHCO ３ A carbon dioxide reduction electrolysis device was manufactured using this electrolysis device. ２was supplied to the cathode, and the cell was heated to 70°C. The applied potential of the cathode was set to -2.6 V relative to the anode, and CO ２ was electrolyzed to CO. The CO generation current density [mA / cm ２ The results of the measurement one hour after the start of electrolysis are shown in Table 1.

[0078] The results shown in Table 1 confirm that the carbon dioxide reduction electrolysis devices manufactured using the ion exchange membrane-electrode assemblies of Examples 1 to 3 have higher electrolysis performance than the carbon dioxide reduction electrolysis devices manufactured using the ion exchange membrane-electrode assemblies of Comparative Examples 1 to 3.

[0079] (2) Measurement of current density decrease rate The current density decrease rate (per hour) [%] was calculated. In "(1) Measurement of CO generation current density," the CO generation current density was recorded immediately after the start of measurement and after 1 hour had elapsed, and the decrease rate was calculated. The results are shown in Table 1.

[0080] The results shown in Table 1 confirm that the carbon dioxide reduction electrolysis devices manufactured using the ion exchange membrane-electrode assemblies of Comparative Examples 1 and 2 had a higher rate of current density reduction than the carbon dioxide reduction electrolysis devices manufactured using the ion exchange membrane-electrode assemblies of Examples 1 to 3.

[0081]

Claims

a support comprising carbon; inorganic fine particles and / or metal complexes supported on the carrier; Including, The support has a volatile content of 0.7% or less.

2. The electrode catalyst according to claim 1, wherein, in an X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu-Kα radiation at 25°C, the support has an X-ray diffraction peak having the highest intensity within a diffraction angle range of 20° to 30° (an X-ray diffraction peak corresponding to a (002) plane of graphite) having a half-width of 5° or less.

3. The electrode catalyst according to claim 1, wherein the support has a crystallite size La of 5 nm or more of a six-membered ring plane of graphite. 　 The electrode catalyst has a water vapor adsorption capacity of 30 cm at 25°C and a relative humidity of 70%. ３ The electrode catalyst according to any one of claims 1 to 3, wherein the electrocatalyst has a surface area of ​​0.01 mPa s or less.

5. The electrode catalyst according to claim 1, wherein the inorganic fine particles are fine particles of one or more types selected from the group consisting of gold, silver, copper, nickel, iron, cobalt, zinc, chromium, palladium, tin, manganese, aluminum, indium, bismuth, molybdenum, platinum, ruthenium, rhodium, iridium, and carbon nitride. 　 The electrode catalyst according to any one of claims 1 to 5, wherein the metal complex is one or more metal complexes in which a ligand is coordinated to a metal selected from the group consisting of copper, nickel, iron, cobalt, zinc, manganese, molybdenum, and aluminum, or an ion of the metal.

7. The electrode catalyst according to claim 1, wherein the support contains one or more elements selected from the group consisting of nitrogen, oxygen, sulfur, selenium, boron, and phosphorus.

8. The electrode catalyst according to claim 1, wherein the support has nitrogen on its surface, and the inorganic fine particles and / or the metal complex are supported on the support via the nitrogen. 　 The electrode catalyst according to any one of claims 1 to 8, wherein the inorganic fine particles are fine particles made of one metal element selected from the group consisting of gold, silver, copper, nickel, iron, cobalt, zinc, chromium, palladium, tin, manganese, aluminum, indium, bismuth, molybdenum, platinum, ruthenium, rhodium, and iridium. 　 The electrode catalyst according to any one of claims 1 to 9, wherein the metal complex is a metal complex containing one metal element selected from the group consisting of copper, nickel, iron, cobalt, zinc, manganese, molybdenum, and aluminum.

11. The electrode catalyst according to claim 9, wherein the one metal element is nickel. 　 The electrode catalyst according to any one of claims 1 to 11, wherein the electrode catalyst has an average particle size of more than 10 nm and not more than 200 nm. 　 A method for producing the electrode catalyst according to any one of claims 1 to 12, The water vapor adsorption capacity at 25°C and 70% relative humidity is 25 cm ３ (STP) / g or less; raw materials for the inorganic fine particles and / or the metal complex; A method for producing an electrode catalyst, comprising: mixing the above components. 　 The method for producing an electrode catalyst according to claim 13 , wherein the mixing step further comprises mixing a nitrogen-containing compound. 　 A catalyst layer comprising at least the electrode catalyst according to any one of claims 1 to 12 and a binder resin. 　 An electrode comprising at least the catalyst layer according to claim 15 and a gas diffusion layer. 　 An ion exchange membrane-electrode assembly comprising the electrode according to claim 16.

18. The ion exchange membrane-electrode assembly according to claim 17, wherein the ion exchange membrane comprises an anion exchange membrane. 　 A carbon dioxide reduction electrolysis device comprising the ion exchange membrane-electrode assembly according to claim 17 or 18. 　 A water electrolysis device comprising the ion exchange membrane-electrode assembly according to claim 17 or 18. 　 An apparatus for electrolytic synthesis of ammonia, comprising the ion exchange membrane-electrode assembly according to claim 17 or 18. 　 A fuel cell comprising the ion exchange membrane-electrode assembly according to claim 17 or 18.

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