Anode, ion exchange membrane-electrode assembly, electrolytic device, and fuel cell

Abstract

To provide an anode that is less susceptible to short-circuiting and exhibits high electrochemical activity or power generation performance, an ion exchange membrane-electrode assembly including the anode, and a carbon dioxide reduction electrolytic device, a water electrolysis device, an ammonia electrolytic synthesis device, and a fuel cell, each of which includes the ion exchange membrane-electrode assembly.SOLUTION: An anode includes: a substrate layer that includes at least an aggregate of metal particles having an aspect ratio of 10 or less, wherein the aspect ratio is a number-average value of b / a values when a major axis diameter of the metal particle obtained by measuring randomly selected 100 metal particles using a scanning electron microscope is defined as a, and a minor axis diameter of the metal particle is defined as b; and a catalyst layer that includes at least a catalyst and a resin.SELECTED DRAWING: None

Description

Technical Field

[0001] The technology of the present disclosure relates to an anode, an ion exchange membrane-electrode assembly, an electrolyzer, and a fuel cell.

Background Art

[0002] In recent years, various electrolyzers and batteries such as carbon dioxide reduction electrolyzers, water electrolyzers, ammonia electrolytic synthesis devices, and fuel cells have been developed with devices equipped with an ion exchange membrane-electrode assembly in which an ion exchange membrane and an electrode are joined. The electrode includes a catalyst layer containing a catalyst for promoting a reaction on each of the cathode side and the anode side, and often has a structure in which a base material for supplying a reaction component to the catalyst layer is adjacent to the catalyst layer.

[0003] For example, Patent Document 1 discloses a water electrolysis / fuel cell having a laminate in which a pair of gas diffusion layers sandwich a membrane electrode assembly in which catalyst electrode layers are laminated on both sides of an electrolyte membrane, and a protective layer is provided at least in part between the gas diffusion layer and the catalyst electrode layer to suppress protrusions from the surface of the gas diffusion layer.

[0004] Also, Patent Document 2 discloses an electrochemical element in which an anode is disposed in contact with one side surface of an ion exchange membrane made of a fluorocarbon polymer and a cathode is disposed in contact with the other side surface, and the ion exchange membrane contains non-conductive pillar particles.

[0005] Patent Document 3 discloses a gas diffusion layer for a gas diffusion electrode having at least a catalyst layer containing an electrode catalyst and a gas diffusion layer having electron conductivity and gas diffusibility, wherein a second surface facing the first surface to be disposed on the side of the catalyst layer is rougher than the first surface, and the surface roughness of the first surface and the second surface measured by a specific measurement method is within a predetermined range.

[0006] Patent Document 4 discloses a metal-supported electrolyte-electrode assembly in which at least a first electrode that functions as either the anode-side electrode or the cathode-side electrode, an electrolyte, and a second electrode that functions as the remaining one of the cathode-side electrode or the anode-side electrode are laminated, and the electrolyte is present between the first electrode and the second electrode. The metal substrate is made of a porous body having open pores on the end face facing the first electrode side. The first electrode has a first layer facing the metal substrate and a second layer facing the electrolyte. The first layer fills the open pores of the metal substrate, the second layer covers the unevenness present on the upper end face of the first layer, and the surface roughness of the upper end face of the second layer facing the electrolyte is smaller than that of the upper end face of the first layer.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0008] The base material is required to have high permeability in order to supply reaction components to the catalyst layer as described above. For example, in a carbon dioxide reduction electrolyzer, the base material of the cathode is generally a relatively inexpensive and highly porous carbon material because it has the role of permeating gaseous reactants and products. On the other hand, since the reactant (water) permeating the base material of the anode is a liquid, a relatively higher porosity is required for the base material than for the cathode in order to ensure sufficient mass transfer. In addition, since a noble potential is applied to the anode and an oxidative atmosphere is formed, if a carbon material is used for the base material, problems of corrosion and deterioration are likely to occur. Therefore, a metal material such as titanium may be used as a non-woven fabric. As shown in Fig. 4, the metal non-woven fabric often has a structure in which metal fibers (fiber diameter: about several hundred to several μm) spreading in the planar direction are intertwined with each other. Due to this structure, the following three problems have been caused.

[0009] (1) When an ion exchange membrane - electrode assembly is manufactured by pressing an electrode and an ion exchange membrane together, pressure concentrates on the membrane directly above the metal fiber portion, and locally the anode and cathode are in direct contact with each other, which becomes a short-circuit factor. (2) The metal fiber ends (flyers) pierce through the membrane, which also becomes a short-circuit factor. (3) When recesses or holes are formed in the base material due to the overlapping of metal fibers, the catalyst of the catalyst layer located at the position of the recesses or holes is less likely to contact the ion exchange membrane during the pressing of the electrode and the ion exchange membrane. Therefore, the effective reaction area of the catalyst with respect to the ion exchange membrane decreases, which becomes a factor in reducing the electrolysis efficiency.

[0010] In particular, in recent years, a thin film of 20 to 50 μm may be used as the ion exchange membrane, and the problems (1) and (2) become prominent.

[0011] In contrast, attempts have been made to prevent short circuits by inserting a protective layer between the ion exchange membrane and the catalyst layer as in Patent Document 1, or by mixing an insulating material into the ion exchange membrane as in Patent Document 2. However, adding a material that does not contribute to ion conduction to the electrode results in a decrease in electrolysis efficiency due to a decrease in ion conductivity.

[0012] Even if the surface of the base material is mechanically processed on one side to change the size of the unevenness (smoothness) as in Patent Document 3, the problem (2) due to fuzzing still remains. Further, it is technically difficult to control the surface shape by performing the treatment as in Patent Document 3 on the metal fiber. Even if the surface smoothness is controlled during the formation of the catalyst layer of the solid oxide fuel cell as in Patent Document 4, the catalyst layer of the polymer electrolyte type electrolytic cell containing a polymer is more likely to be deformed compared to the solid oxide type composed only of metal and metal oxide. Therefore, there was a problem of eventually causing a short circuit when the ion exchange membrane and the electrode were pressure-bonded.

[0013] The technology of the present disclosure has been made in view of the above circumstances, and the problem of the technology of the present disclosure is to provide an anode that is less likely to cause a short circuit and has high electrolytic activity or power generation performance, an ion exchange membrane-electrode assembly including the anode, and a carbon dioxide reduction electrolysis apparatus, a water electrolysis apparatus, an ammonia electrolytic synthesis apparatus, and a fuel cell including the ion exchange membrane-electrode assembly, and an object thereof is to solve the problem.

Means for Solving the Problem

[0014] <1> A base material layer containing at least an aggregate of metal particles having an aspect ratio of 10 or less, wherein the aspect ratio is the number average value of the b / a values when the major axis diameter of the metal particles measured using a scanning electron microscope for 100 randomly selected metal particles is a and the minor axis diameter of the metal particles is b, and A catalyst layer containing at least a catalyst and a resin An anode including

[0015] <2> The anode according to <1>, wherein the average value of the major axis diameters of 100 randomly extracted openings is 20 μm or less in the photographic observation of the surface of the base material layer by a scanning electron microscope. <3> The anode according to <1> or <2>, wherein the porosity of the base material layer is 30% or more. <4> The anode according to any one of <1> to <3>, wherein the metal of the metal particles contains one or more selected from the group consisting of titanium, nickel, cobalt, iron, tin, tungsten, tantalum, copper, silver, gold, platinum, iridium, ruthenium, and palladium.

[0016] <5> An ion exchange membrane - electrode assembly having a cathode, the anode according to any one of <1> to <4>, and an ion exchange membrane.

[0017] <6> The ion exchange membrane - electrode assembly according to <5>, wherein the ion exchange membrane includes an anion exchange membrane. <7> The ion exchange membrane - electrode assembly according to <5> or <6>, wherein the average thickness of the ion exchange membrane in the dry state is 60 μm or less.

[0018] <8> A carbon dioxide reduction electrolysis device including the ion exchange membrane - electrode assembly according to any one of <5> to <7>. <9> A water electrolysis device including the ion exchange membrane - electrode assembly according to any one of <5> to <7>. <10> An ammonia electrolytic synthesis device including the ion exchange membrane - electrode assembly according to any one of <5> to <7>. <11> A fuel cell including the ion exchange membrane - electrode assembly according to any one of <5> to <7>.

Advantages of the Invention

[0019] According to the technology of the present disclosure, it is possible to provide an anode that is less likely to cause a short - circuit and has high electrolytic activity or power generation performance, an ion exchange membrane - electrode assembly including the anode, and a carbon dioxide reduction electrolysis device, a water electrolysis device, an ammonia electrolytic synthesis device, and a fuel cell including the ion exchange membrane - electrode assembly.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0021] The upper and lower limit values of the numerical ranges described in this specification can be arbitrarily combined. For example, when the numerical ranges "A to B" and "C to D" are described, the numerical ranges "A to D" and "C to B" are also included in the scope of the present disclosure. In addition, the numerical range "lower limit value to upper limit value" described in this specification means, unless otherwise specified, that it is greater than or equal to the lower limit value and less than or equal to the upper limit value.

[0022] <Anode> The anode according to this embodiment includes at least an aggregate of metal particles having an aspect ratio of 10 or less, and the aspect ratio is the number average value of the b / a values when the major axis diameter of the metal particles measured using an electron microscope for 100 randomly selected metal particles is a and the minor axis diameter of the metal particles is b, and a base material layer, and a catalyst layer containing at least a catalyst and a resin. The anode according to this embodiment can be applied not only to a carbon dioxide reduction electrolysis device but also to anodes of various devices such as a water electrolysis device, an ammonia electrolytic synthesis device, and a fuel cell. However, in this specification, mainly, the anode in a carbon dioxide reduction electrolysis device will be described.

[0023] First, the structure of the anode will be described. Fig. 2 shows a schematic diagram of an ion exchange membrane - electrode assembly preferably used in this embodiment. The ion exchange membrane - electrode assembly shown in Fig. 2 is particularly suitable for application to a carbon dioxide reduction electrolyzer. As shown in Fig. 2, an ion exchange membrane - electrode assembly 60 is shown, which has a cathode - side base material layer (gas diffusion layer) 10, a cathode - side catalyst layer 20, an ion exchange membrane 30, an anode - side catalyst layer 40, and an anode - side base material layer 50. Details of the ion exchange membrane - electrode assembly 60 will be described later. As shown in Fig. 2, the cathode - side base material layer (gas diffusion layer) 10 is adjacent to the cathode - side catalyst layer 20, takes in carbon dioxide (CO2) from the outside air, and supplies it to the cathode - side catalyst layer 20. On the other hand, the anode - side base material layer 50 is adjacent to the anode - side catalyst layer 40, takes in water (H2O) from the electrolytic solution, and supplies it to the anode - side catalyst layer 40. The cathode - side catalyst layer 20 includes at least a catalyst 22 that promotes the reaction at the cathode and a resin 24 that serves as a matrix resin for the catalyst 22. The anode - side catalyst layer 40 includes at least a catalyst 42 that promotes the reaction at the anode and a resin 44 that serves as a matrix resin for the catalyst 42. Hereinafter, unless otherwise specified, the reference numerals in Fig. 2 will be omitted in the description.

[0024] As described above, the anode according to this embodiment includes a base material layer and a catalyst layer. The base material layer includes at least an aggregate of metal particles having an aspect ratio of 10 or less as a base material, and the catalyst layer includes at least a catalyst and a resin. Furthermore, the aspect ratio in the base material layer is obtained as the number - average value of the b / a values when, for 100 randomly selected metal particles, the major - axis diameter of the metal particles is measured using a scanning electron microscope as a, and the minor - axis diameter of the metal particles is b.

[0025] Since the anode according to this embodiment includes at least an aggregate of metal particles having an aspect ratio of 10 or less, it is possible to suppress the piercing of the ion exchange membrane by the fiber ends generated in the conventional metal non - woven fabric. Also, when manufacturing an ion exchange membrane - electrode assembly by crimping the anode and the ion exchange membrane, it is possible to suppress the piercing of the ion exchange membrane by the fiber ends. As described above, when the metal fibers overlap, recesses and holes are formed in the base material layer. However, the recesses and holes formed by the aggregation of metal particles are smaller than those formed by the overlapping of metal fibers. Therefore, when the anode and the ion exchange membrane are crimped, the amount of catalyst that is difficult to contact the ion exchange membrane can be reduced. Thus, the effective reaction area of the catalyst with respect to the ion exchange membrane increases, and the electrolysis efficiency in the electrolyzer and the power generation performance in the battery can be improved, respectively. In this specification, the recesses and holes formed by the aggregation of metal particles are collectively referred to as "openings". The definition of the opening will be described later. A recess means an opening with a shallow depression, and a hole means an opening with a deeper depression than the recess.

[0026] Hereinafter, the base material layer and the catalyst layer included in the anode will be described in more detail. As described above, the anode in the carbon dioxide reduction electrolyzer will be mainly described. For the water electrolyzer, the ammonia electrolytic synthesis apparatus, and the fuel cell, when the preferred embodiments are different from those of the carbon dioxide reduction electrolyzer, they will be described separately. However, when not otherwise specified, the same embodiments as those of the carbon dioxide reduction electrolyzer can be adopted.

[0027] 〔Base material layer〕 The base material layer of the anode according to the present embodiment includes, as a base material, at least an aggregate of metal particles having an aspect ratio of 10 or less. Since the aspect ratio of the metal particles included in the base material layer is 10 or less and the base material layer includes an aggregate of metal particles, a short circuit is less likely to occur, and an anode with high electrolytic activity or power generation performance can be obtained. The aspect ratio of the metal particles is preferably from 1 to 10, more preferably from 1 to 7, and still more preferably from 1 to 5. Further, from the viewpoint of increasing the reaction area of the catalyst, the major axis diameter (a) of the metal particles is preferably from 0.01 to 1000 μm, more preferably from 1 to 100 μm, and still more preferably from 5 to 50 μm.

[0028] The aspect ratio of the metal particles is determined as the number average value of the b / a values by photographically observing 100 randomly selected metal particles using a scanning electron microscope and measuring the major axis diameter (a) and minor axis diameter (b) of the 100 metal particles. The number average value of the b / a value as the aspect ratio of the metal particles can be obtained, for example, by photographically observing 100 randomly selected metal particles using a scanning electron microscope and performing image analysis by importing the obtained photograph into image analysis software such as ImageJ.

[0029] The base material layer according to this embodiment preferably has a porosity of 30% or more, more preferably 40% or more, and still more preferably 50% or more. When the porosity of the base material layer is 30% or more, the permeability of the reactant (water) becomes high, and the electrolytic activity or power generation performance can be made higher. The porosity of the base material layer is preferably 30 to 80%, more preferably 40 to 75%, and still more preferably 50 to 70% in view of the balance between the permeability of the reactant (water) and the reaction area of the catalyst. The porosity of the base material layer can be controlled by adjusting the temperature, time, pressing pressure, etc. during the sintering of the metal particles. For example, by shortening the high-temperature holding time during sintering, the porosity can be increased (= the density can be decreased). In addition, the porosity of the base material layer can be measured by the mercury intrusion method (JIS Z 8890:2017) or X-ray CT (Computed Tomography).

[0030] The base material layer according to this embodiment has openings by including aggregates of metal particles having an aspect ratio of 10 or less. Here, the opening means a region having a depression of 5% or more of the total thickness of the base material layer perpendicularly from the surface of the base material layer toward the inside of the base material layer. The depression also includes a hole penetrating from the surface to the back surface of the base material layer. In addition, the surface of the base material layer means a surface formed by connecting the upper ends of adjacent particles in a photographic observation of the base material layer using a scanning electron microscope. The base material layer according to this embodiment preferably has an average major axis length of the openings of 20 μm or less. Specifically, in the photographic observation of the surface of the base material layer by a scanning electron microscope, it is preferable that 100 openings are randomly extracted, and the average major axis length of the 100 openings is 20 μm or less. When the average major axis length of the openings is 20 μm or less, the effective reaction area of the catalyst with respect to the ion exchange membrane can be further increased, and the electrolysis efficiency and power generation performance can be further improved.

[0031] Here, the major axis length of the opening is the major axis length of the opening in the photograph by a scanning electron microscope, and means the major axis length when the opening is approximated by an ellipse. From the viewpoint of the balance between the increase in the effective reaction area of the catalyst with respect to the ion exchange membrane and the permeability of the product of the oxidation reaction by the catalyst, the average major axis length of the openings is more preferably 1 to 20 μm, and even more preferably 5 to 15 μm.

[0032] The type of metal of the metal particles is not particularly limited. For example, titanium, nickel, cobalt, iron, tin, tungsten, tantalum, copper, silver, gold, platinum, iridium, ruthenium, palladium, etc. may be mentioned. One type of metal may be used, or two or more types of metal may be used. Among them, titanium is preferable from the viewpoint of corrosion resistance.

[0033] Since the anode of the carbon dioxide reduction electrolysis device functions as an oxidation electrode that causes an oxidation reaction to obtain oxygen from water, it is preferable to use the base material according to this embodiment, which has excellent liquid permeability, as the base material of the electrode.

[0034] (Base material of fuel cell) When the anode according to this embodiment is used as the anode of a fuel cell, the aspect ratio of the metal particles, the major axis diameter (a) of the metal particles, the porosity of the base material, and the metal type of the metal particles are preferably the following. From the viewpoint of preventing short circuit, the aspect ratio of the metal particles is preferably 1 to 10, and more preferably 1 to 7. The major axis diameter (a) of the metal particles is preferably from 0.01 to 1000 μm, more preferably from 1 to 100 μm, from the viewpoint of ensuring the reaction area of the catalyst. The porosity of the substrate is preferably from 20 to 80%, more preferably from 40 to 80%, from the viewpoint of the permeability of the product (water). The metal of the metal particles is preferably titanium, nickel, platinum, gold, or tin, more preferably titanium or nickel, from the viewpoints of corrosion resistance and catalytic activity.

[0035] The substrate may be used alone as a single layer or may be laminated and used in two or more layers. As the substrate according to the present embodiment, a commercially available product may be used. For example, an aggregate sheet "WEBTi (registered trademark)" manufactured by Toho Titanium Co., Ltd. can be used.

[0036] [Catalyst layer] The catalyst layer according to the present embodiment contains at least a catalyst and a resin.

[0037] (Catalyst) The catalyst according to the present embodiment preferably comprises a carrier containing carbon and having inorganic fine particles or metal complexes supported thereon. In the catalyst in the technology of the present disclosure, the component exhibiting catalytic action is inorganic fine particles or metal complexes supported on a carrier. In the technology of the present disclosure, the inorganic fine particles and metal complexes are referred to as "catalyst sources", and the carrier on which the catalyst source is supported is referred to as "catalyst". The inorganic fine particles and metal complexes are not particularly limited as long as they are components exhibiting catalytic action. In the technology of the present disclosure, the inorganic fine particles mean metals and inorganic compounds having an average particle diameter measured by photographic observation using a scanning electron microscope or the like of 1 to 100 nm.

[0038] Moreover, the catalyst in the technology of the present disclosure is preferably coated with an ionomer. By coating the catalyst with an ionomer, an ion conduction channel is easily formed between the coated catalyst and a solid electrolyte (ion exchange membrane) described later, the ion movement generated by the reaction becomes easy, and it becomes possible to improve the electrolysis efficiency and power generation performance.

[0039] [Catalyst source of carbon dioxide reduction electrolyzer] When the catalyst layer is used as the anode-side catalyst layer of the carbon dioxide reduction electrolyzer, it is preferable to use a catalyst source in which the inorganic fine particles and the metal complex have an action of generating at least oxygen by an oxidation reaction. Specifically, iridium oxide, rhodium oxide, ruthenium oxide, platinum, and their complexes are used. From the viewpoint of catalytic activity, iridium oxide, rhodium oxide, and ruthenium oxide are preferable, and iridium oxide and ruthenium oxide are more preferable. From the viewpoint of ensuring the surface area, the average particle size of the inorganic fine particles as the catalyst source of the anode-side catalyst layer of the carbon dioxide reduction electrolyzer is preferably 0.5 to 50 nm, and more preferably 0.5 to 20 nm. The average particle size can be measured by photograph observation using a scanning electron microscope or the like.

[0040] [Catalyst source of water electrolyzer and ammonia electrolytic synthesis device] When the catalyst layer is used as the anode-side catalyst layer of a water electrolyzer or an ammonia electrolytic synthesis device, it is preferable to use a catalyst source in which the inorganic fine particles and the metal complex have an action of generating at least oxygen by an oxidation reaction. Specifically, iridium oxide, platinum, nickel, cobalt, iron, etc. are used. From the viewpoint of catalytic activity, iridium oxide, nickel, and cobalt are preferable, and iridium oxide and nickel are more preferable. From the viewpoint of ensuring the surface area, the average particle size of the inorganic fine particles as the catalyst source of the anode-side catalyst layer of the water electrolyzer and the ammonia electrolytic synthesis device is preferably 0.5 to 50 nm, and more preferably 0.5 to 20 nm. The average particle size can be measured by photographic observation using a scanning electron microscope or the like.

[0041] [Catalyst source for fuel cell] When the catalyst layer is used as the anode-side catalyst layer of a fuel cell, it is preferable to use an inorganic fine particle and a metal complex as a catalyst source having an action of oxidizing at least hydrogen by an oxidation reaction. Specifically, platinum, ruthenium, palladium, cobalt, etc. are used. From the viewpoint of catalytic activity, platinum, ruthenium, and palladium are preferable, and platinum and ruthenium are more preferable. From the viewpoint of ensuring the surface area, the average particle size of the inorganic fine particles as the catalyst source of the anode-side catalyst layer of the fuel cell is preferably 0.5 to 50 nm, and more preferably 0.5 to 20 nm. The average particle size can be measured by photographic observation using a scanning electron microscope or the like.

[0042] [Carrier] The carrier according to this embodiment is not particularly limited, but preferably contains carbon from the viewpoint of imparting conductivity. Since carbon usually has conductivity, a carrier containing carbon is a conductive carrier. Examples of the carrier containing carbon include carbon blacks (such as 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. Among them, carbon black is preferable from the viewpoint of improving the active site density.

[0043] From the perspective of improving the active site density and current density, the primary particle diameter of carbon black is preferably 5 to 200 nm, more preferably 10 to 100 nm, and even more preferably 10 to 50 nm. The primary particle diameter of carbon black can be measured by a transmission electron microscope. The primary particle diameter can be measured by measuring the length in the longest direction of the particles revealed by the microscope as the major axis and calculating the average value of the obtained major axes. From the same perspective, it is preferable that the secondary particle diameter (particle diameter of the aggregate) of carbon black is small, and it is preferable that the carbon black has a large amount of functional groups. The carbon black may be a commercially available product, and examples thereof include Vulcan (registered trademark) XC-72 (manufactured by Cabot), BLACKPEARL2000 (manufactured by Cabot Corporation), and the like. Only one type of carrier may be used, or two or more types may be used in combination.

[0044] (Resin) The resin functions as a binder resin in the catalyst layer, is a matrix resin (continuous phase) capable of dispersing and immobilizing the catalyst according to the present embodiment, and also has a function of transmitting ions generated by electrolysis and improving the electrolysis efficiency. As the resin having such a function, it is preferable to use an ionomer. Further, in order not to impair the conductivity of the catalyst layer, the ionomer is preferably conductive and more 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.

[0045] Examples of the cation exchange resin include a fluororesin having a sulfone group and a styrene-divinylbenzene copolymer having a sulfone group. Commercially available products can also be used, and examples thereof include Nafion (manufactured by Chemours), Aquivion (manufactured by Solvay Specialty Polymers), DIAION (manufactured by Mitsubishi Chemical), Fumasep (manufactured by FUMATECH), and the like. Examples of the anion exchange resin include resins having one or more ion exchange groups selected from the group consisting of a quaternary ammonium group, a primary amino group, a secondary amino group, and a tertiary amino group. 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 Asahi Kasei), TOYOPEARL (manufactured by Tosoh), and the like.

[0046] From the viewpoint of improving conductivity, the anion exchange resin preferably has a base point density of 2.0 to 5.0 mmol / cm 3 in the dry state, more preferably 2.5 mmol / cm 3 or more and less than 4.5 mmol / cm 3 , and even more preferably 2.9 mmol / cm 3 or more and less than 4.5 mmol / cm 3 . The base point density of the anion exchange resin can be obtained from the integral value of the signal when 1 1H NMR measurement is performed on the anion exchange resin. In addition, for the anion exchange resin, the dry state means a state in which the anion exchange resin does not contain free water. For example, the anion exchange resin can be dried by heating in a vacuum.

[0047] When the anode according to this embodiment is used as the anode of a carbon dioxide reduction electrolyzer, from the viewpoint of improving conductivity, it is preferable to use the same resin as the solid electrolyte (ion exchange membrane). When the anode according to this embodiment is used as the anode of a water electrolyzer, an ammonia electrolytic synthesis device, or a fuel cell, from the viewpoint of reducing the ion transfer resistance, it is preferable to use the same ion exchange resin as the ion exchange membrane.

[0048] In addition, from the perspective of further improving the production efficiency in the oxidation reaction using the catalyst, the content of the catalyst according to the present embodiment in the catalyst layer is preferably 5 to 90% by mass, more preferably 10 to 80% by mass, and still more preferably 15 to 60% by mass.

[0049] The anode according to the present embodiment only needs to include the above-described base material layer and catalyst layer, and the structure is not particularly limited. For example, it may have a laminated structure of the anode-side catalyst layer 40 and the anode-side base material layer 50 included in the ion exchange membrane-electrode assembly shown in FIG. 2, or a structure in which the catalyst and the resin enter the opening of the base material layer and the base material (aggregate of metal particles) is coated with the catalyst layer. The anode obtained by the method of "spraying a resin solution in which a catalyst is dispersed in a mist form onto the base material layer" described later has a structure in which the catalyst and the resin enter the opening of the base material layer and the base material of the base material layer is coated with the catalyst layer. In other words, it is a structure in which the catalyst layer and the base material layer are integrated.

[0050] The manufacturing method of the anode according to the present embodiment is not particularly limited. For example, a resin solution in which a catalyst is dispersed may be formed into a sheet shape and laminated on the base material layer; the base material layer may be immersed in a resin solution in which a catalyst is dispersed, taken out, and dried for manufacturing; or a resin solution in which a catalyst is dispersed may be sprayed onto the base material layer in a mist form and dried for manufacturing. Among the above, from the perspective of maintaining the permeability of the base material layer, it is preferable to use the method of spraying a resin solution in which a catalyst is dispersed in a mist form onto the base material layer.

[0051] The resin solution in which the catalyst is dispersed (catalyst dispersion) can be prepared, for example, by mixing 5 to 10 parts by mass of the catalyst with 1 part by mass of the resin and adding it to a solvent soluble in the resin. The solvent soluble in the resin varies depending on the resin used. For example, an alcohol such as isopropanol can be used. The solvent may further contain water. The catalyst dispersion can be atomized and the catalyst can be attached to the substrate layer by spraying the catalyst dispersion together with pressurized air while heating the substrate layer to 80 to 100 °C.

[0052] <Ion exchange membrane - electrode assembly> The ion exchange membrane - electrode assembly according to this embodiment has a cathode, the anode according to the above - described embodiment, and an ion exchange membrane. Since the ion exchange membrane - electrode assembly according to this embodiment includes the anode of the present disclosure, short - circuit is less likely to occur and the electrolytic activity or power generation performance is high.

[0053] 〔Ion exchange membrane〕 The ion exchange membrane - electrode assembly according to this embodiment has an ion exchange membrane. The ion exchange membrane is a solid electrolyte, and a polymer membrane can be used. Various ionomers can be used as the polymer, which may be a cation - exchange resin or an anion - exchange resin, but an anion - exchange resin is preferably used. That is, the ion exchange membrane is preferably an anion - exchange membrane. More preferably, the same anion - exchange resin as the ionomer used in the above - described catalyst layer is used. As the ion exchange membrane, commercially available products as cation - exchange membranes or anion - exchange membranes may be used.

[0054] From the viewpoint of reducing ion resistance, the average thickness of the ion exchange membrane in the dry state is preferably 60 μm or less. Also, from the viewpoint of preventing pinhole formation, the average thickness of the ion exchange membrane in the dry state is preferably 10 μm or more. From the viewpoint of balancing ion resistance and pinhole prevention, the average thickness of the ion exchange membrane in the dry state is more preferably 15 to 50 μm, and even more preferably 20 to 40 μm.

[0055] Also, when an anion - exchange membrane is used for the ion exchange membrane, the base point density is preferably 0.5 to 5.0 mmol / cm 3 in the dry state, preferably 2.5 mmol / cm 3 or more, 4.5 mmol / cm3 It is more preferably less than 2.9 mmol / cm 3 and more preferably not less than 4.5 mmol / cm 3 and less than that.

[0056] Examples of the cation exchange membrane include strongly acidic cation exchange membranes in which a sulfonic group is introduced into a fluororesin matrix, Nafion 117, Nafion 115, Nafion 212, Nafion 350 (manufactured by Chemours), strongly acidic cation exchange membranes in which a sulfonic group is introduced into a styrene-divinylbenzene copolymer matrix, Neosepta CSE (manufactured by Asahi Kasei), and the like. Examples of the anion exchange membrane include anion exchange membranes having one or more ion exchange groups selected from the group consisting of a quaternary ammonium group, a primary amino group, a secondary amino group, and a tertiary amino group. Specifically, for example, Neosepta (registered trademark) ASE, AHA, ACS, AFX (manufactured by Asahi Kasei), Selemion (registered trademark) AMVN, DSVN, AAV, ASVN, AHO (manufactured by Asahi Glass), and the like can be mentioned.

[0057] (Ion Exchange Membrane in Carbon Dioxide Reduction Electrolysis Device) In a carbon dioxide reduction electrolysis device, the reduction reaction at the cathode (negative electrode) varies depending on the type of ion exchange membrane. When a cation exchange membrane is used as the ion exchange membrane, the reduction reactions of the following reaction formulas (1) and (2) occur. When an anion exchange membrane is used as the ion exchange membrane, the reduction reactions of the following reaction formulas (3) and (4) occur.

[0058] CO2 + 2H + + 2e - → CO + H2O (1) 2H + + 2e - → H2 (2) H2O + CO2 + 2e - → CO + 2OH - (3) 2H2O + 2e - → H2 + 2OH - (4)

[0059] In a carbon dioxide reduction electrolysis device, the oxidation reaction at the anode varies depending on the type of ion exchange membrane. When a cation exchange membrane is used as the ion exchange membrane, the oxidation reaction of the following reaction formula (5) occurs, and when an anion exchange membrane is used as the ion exchange membrane, the oxidation reaction of the following reaction formula (6) occurs.

[0060] 2H2O→O2+4H + +4e - (5) 4OH - →O2+2H2O+4e - (6)

[0061] (Ion exchange membrane in a water electrolysis device) In a water electrolysis device, the ion exchange membrane may be a cation exchange membrane or an anion exchange membrane.

[0062] (Ion exchange membrane in an ammonia electrolytic synthesis device) In an ammonia electrolytic synthesis device, the ion exchange membrane may be a cation exchange membrane or an anion exchange membrane, but from the viewpoint of preventing the formation of ammonium salts, it is preferable to use an anion exchange membrane.

[0063] (Ion exchange membrane in a fuel cell) In a fuel cell, the ion exchange membrane may be a cation exchange membrane or an anion exchange membrane, but from the viewpoint of reducing ion resistance, it is preferable to use a cation exchange membrane.

[0064] Cathode The cathode is not particularly limited, but like the anode, it can include a base material layer and a catalyst layer.

[0065] (Base material layer) Since the cathode (negative electrode) of the carbon dioxide reduction electrolysis device functions as a reduction electrode for reducing carbon dioxide to carbon monoxide, the base material layer of the cathode is preferably a gas diffusion layer that permeates carbon dioxide and carbon monoxide. Since the cathode of the water electrolysis device functions as a reduction electrode that generates at least hydrogen by a reduction reaction, the base material layer of the cathode of the water electrolysis device is preferably a gas diffusion layer that permeates hydrogen. Further, although the cathode of the ammonia electrolytic synthesis device functions as a reduction electrode that generates at least ammonia, since hydrogen is generated as a byproduct, similar to the water electrolysis device, the base material layer of the cathode is preferably a gas diffusion layer that permeates hydrogen. Since the cathode of the fuel cell functions as a reduction electrode that reduces at least oxygen by a reduction reaction, the base material layer of the cathode of the fuel cell is preferably a gas diffusion layer that permeates oxygen.

[0066] The gas diffusion layer preferably contains carbon fibers. As the carbon fibers, carbon paper or non-woven fabric can be used. For example, graphite carbon, glassy carbon, etc. can be mentioned. The gas diffusion layer may further include one or two or more porous layers.

[0067] (Catalyst layer) The catalyst layer on the cathode side preferably contains a catalyst and a resin. Also in the catalyst layer on the cathode side, similar to the catalyst layer on the anode side, the catalyst preferably consists of a carrier containing carbon and having an inorganic fine particle or a metal complex supported thereon.

[0068] [Carbon dioxide reduction electrolysis device] In the catalyst layer on the cathode side of the carbon dioxide reduction electrolysis device, it is preferable to use an inorganic fine particle and a metal complex as a catalyst source having an action of generating at least carbon monoxide by a reduction reaction. Specifically, the inorganic fine particles for carbon dioxide reduction are preferably fine particles selected from the group consisting of gold, silver, copper, nickel, iron, cobalt, zinc, chromium, palladium, tin, manganese, aluminum, indium, bismuth, molybdenum, and carbon nitride. Only one inorganic fine particle may be used, or two or more may be used in combination. Among these, from the viewpoint of the reaction efficiency of the carbon dioxide reduction reaction, the material of the inorganic fine particles is preferably silver, gold, zinc, tin, copper, and bismuth, more preferably silver, gold, copper, and tin, and still more preferably silver, gold, and copper.

[0069] From the viewpoint of the reaction rate of the carbon dioxide reduction reaction, the average particle size of the inorganic fine particles as the catalyst source of the cathode-side catalyst layer of the carbon dioxide reduction electrolysis device 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. Also, there is no limitation on the lower limit value of the average particle size, but from the aspect of ease of production, it is preferably 1 nm or more, and more preferably 5 nm or more. The average particle size can be measured by photographic observation using a scanning electron microscope or the like.

[0070] The metal complex as the catalyst source of the cathode-side catalyst layer of the carbon dioxide reduction electrolysis device is a metal complex in which a ligand is coordinated to a metal or an ion of the metal. The metal ion is preferably selected from the group consisting of copper, nickel, iron, cobalt, zinc, manganese, molybdenum, and aluminum. Among these, from the viewpoint of the reaction efficiency of the carbon dioxide reduction reaction, the metal is preferably nickel, cobalt, iron, copper, zinc, and manganese, more preferably nickel, cobalt, iron, and copper, and still more preferably nickel, cobalt, and iron. The metal complex may contain only one kind of metal or an ion of the metal, or may contain two or more kinds. The type of the ligand is not particularly limited, and examples thereof include phthalocyanine complexes, porphyrin complexes, pyridine complexes, metal-supported covalent triazine structures, metal-organic structures, and the like. Among them, phthalocyanine complexes, porphyrin complexes, pyridine complexes, and metal-supported covalent triazine structures are preferred, phthalocyanine complexes, porphyrin complexes, and metal-supported covalent triazine structures are more preferred, and porphyrin complexes and metal-supported covalent triazine structures are still more preferred. The metal complex may contain only one kind of ligand, or may contain two or more kinds.

[0071] [Water electrolysis device, ammonia electrolytic synthesis device] In the cathode side catalyst layer of the water electrolysis device and the ammonia electrolytic synthesis device, it is preferable to use a catalyst source in which inorganic fine particles and metal complexes have an action of generating at least hydrogen by a reduction reaction. Specifically, platinum, ruthenium, nickel, carbon, etc. are used, and from the viewpoint of catalytic activity, platinum, ruthenium, nickel are preferable, and platinum and nickel are more preferable. From the viewpoint of ensuring the surface area, the average particle diameter of the inorganic fine particles as the catalyst source of the cathode side catalyst layer of the water electrolysis device is preferably 0.5 to 50 nm, and more preferably 0.5 to 20 nm. The average particle diameter can be measured by photographic observation using a scanning electron microscope or the like.

[0072] [Fuel cell] In the cathode side catalyst layer of the fuel cell, it is preferable to use a catalyst source in which inorganic fine particles and metal complexes have an action of reducing at least oxygen by a reduction reaction. Specifically, platinum, carbon nitride, nickel complex, cobalt complex, etc. are used, and from the viewpoint of catalytic activity, platinum, carbon nitride, nickel complex are preferable, and platinum and nickel complex are more preferable. From the viewpoint of ensuring the surface area, the average particle diameter of the inorganic fine particles as the catalyst source of the cathode side catalyst layer of the fuel cell is preferably 0.5 to 500 nm, and more preferably 0.5 to 20 nm. The average particle diameter can be measured by photographic observation using a scanning electron microscope or the like.

[0073] The resin contained in the cathode side catalyst layer can be the same as the resin contained in the anode side catalyst layer. Here, in the carbon dioxide reduction electrolyzer, from the viewpoint of reducing the ion transfer resistance, it is preferable to use the same ion exchange resin as the ion exchange membrane for the resin. In particular, when an anion exchange resin is used, the anion exchange resin itself has the ability to adsorb carbon dioxide, and it becomes possible to greatly improve the electrolysis efficiency of carbon dioxide in combination with the ease of ion transfer of the ion exchange resin. Also, in the water electrolyzer, ammonia electrolytic synthesis apparatus, and fuel cell, from the viewpoint of reducing the ion transfer resistance, it is preferable to use the same ion exchange resin as the ion exchange membrane for the resin.

[0074] The content of the catalyst according to this embodiment in the catalyst layer on the cathode side is preferably 5 to 90% by mass, more preferably 10 to 80% by mass, and still more preferably 15 to 60% by mass from the viewpoint of further improving the production efficiency of the reduction reaction using the catalyst.

[0075] The ion exchange membrane - electrode assembly according to this embodiment can be manufactured by pressing a cathode, an ion exchange membrane, and the anode according to this embodiment with the catalyst layer sides of the cathode and the anode facing the ion exchange membrane. When the anode is the anode obtained by the method of "spraying a resin solution in which a catalyst is dispersed in a mist form onto the base material layer" described above, the surface of the base material layer on the side where the resin solution is sprayed, in other words, the surface of the base material layer where the catalyst is attached, may be opposed to the ion exchange membrane. When the cathode is manufactured in the same manner as the anode, similarly in the cathode, the surface where the catalyst is attached may be opposed to the ion exchange membrane. The base material layer of the anode according to this embodiment contains an aggregate of metal particles having an aspect ratio of 10 or less as the base material, so the openings formed by the aggregation of the metal particles are small, and when the anode and the ion exchange membrane are pressed together, the amount of the catalyst that is difficult to contact the ion exchange membrane can be reduced. Therefore, the effective reaction area of the catalyst with respect to the ion exchange membrane increases, and the electrolysis efficiency in the electrolyzer and the power generation performance in the battery can be improved respectively.

[0076] <Carbon Dioxide Reduction Electrolysis Device> The carbon dioxide reduction electrolysis device according to this embodiment includes the ion exchange membrane - electrode assembly according to this embodiment. Since the carbon dioxide reduction electrolysis device according to this embodiment includes the ion exchange membrane - electrode assembly according to this embodiment, short - circuit is less likely to occur and the electrolytic activity is high. The carbon dioxide reduction electrolysis device according to this embodiment preferably has an anode according to this embodiment, an anode that forms a pair of electrodes with the anode, an ion exchange membrane interposed in a contact state between the cathode and the anode, and a voltage application unit that applies a voltage between the cathode and the anode.

[0077] FIG. 3 is a schematic diagram of the carbon dioxide reduction electrolysis device preferably used in this embodiment. FIG. 3 shows a carbon dioxide reduction electrolysis device 800 having an anode (positive electrode) 400, a cathode (negative electrode) 200 that forms a pair of electrodes with the anode (positive electrode) 400, an ion exchange membrane 300 interposed in a contact state between the cathode 200 and the anode 400, and a voltage application unit 700 that applies a voltage between the cathode 200 and the anode 400. The carbon dioxide reduction electrolysis device 800 shown in FIG. 3 further has a cathode current collector plate 100, an anode current collector plate 500, and an electrolytic solution 600. The anode according to the above - described embodiment is used as the anode (positive electrode) 400. Also, the ion exchange membrane 300 is the same as the ion exchange membrane 30 in FIG. 2, and the ion exchange membrane 300 is preferably an anion exchange membrane. The details of the cathode 200, the ion exchange membrane 300, and the anode 400 are as described above. Hereinafter, each element other than the cathode 200, the ion exchange membrane 300, and the anode 400 will be described with the symbols omitted.

[0078] 〔Cathode Current Collector Plate〕 Examples of the cathode current collector (negative electrode current collector) include metal materials such as copper (Cu), nickel (Ni), stainless steel (SUS), nickel-plated steel, and brass. Among them, copper is preferred in terms of ease of processing and cost. When the material of the cathode current collector is a metal material, examples of its shape include a metal foil, a metal plate, a metal thin film, an expanded metal, a punched metal, and a foamed metal.

[0079] The cathode current collector may be provided with a gas supply hole for supplying a raw material gas containing carbon dioxide to the cathode and a gas recovery hole for recovering a product gas containing carbon monoxide. By having the gas supply hole and the gas recovery hole, the raw material gas can be uniformly and efficiently fed into the cathode and the product gas (including the unreacted raw material gas) can be discharged. The gas supply hole and the gas recovery hole may each independently have only one or two or more. In addition, the shape, location, size, etc. of the gas supply hole and the gas recovery hole are not limited and are appropriately set. In addition, when the cathode current collector is breathable, the gas supply hole and the gas recovery hole are not necessarily required. Note that when the cathode has a role of transmitting electrons, the cathode current collector is not necessarily required.

[0080] 〔Anode current collector〕 The anode current collector (positive electrode current collector) preferably has electron conductivity and rigidity to support the anode in order to receive electrons from the anode. From this perspective, for the anode current collector, metal materials such as titanium (Ti), copper (Cu), nickel (Ni), stainless steel (SUS), nickel-plated steel, and brass can be preferably used.

[0081] The anode current collector may be provided with a gas flow path for feeding a raw material gas (such as H2O) to the anode. By having the gas flow path in the anode current collector, the raw material gas can be uniformly and efficiently fed into the anode. Note that the number, shape, location, size, etc. of the gas flow path are not limited and are appropriately set.

[0082] 〔Voltage application unit〕 The voltage application unit plays a role of applying a voltage between the cathode and the anode by applying a voltage to the cathode current collector plate and the anode current collector plate. Here, since both current collector plates are conductors, while supplying electrons to the cathode, they will receive electrons from the anode. Also, a control unit (not shown) may be electrically connected to the voltage application unit to apply an appropriate voltage.

[0083] 〔Electrolyte〕 The electrolyte is preferably an aqueous solution with a pH of 5 or higher. For example, an aqueous carbonate solution, an aqueous bicarbonate solution (e.g., KHCO3 aqueous solution), an aqueous sulfate solution, an aqueous borate solution, an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, an aqueous sodium chloride solution, etc. can be mentioned.

[0084] (Reaction gas supply unit) In the carbon dioxide reduction electrolysis device according to this embodiment, a reaction gas supply unit (not shown) may be provided outside the carbon dioxide reduction electrolysis device. That is, it is only necessary to supply CO2, which is a reaction gas, to the catalyst layer provided in the cathode. The reaction gas may be supplied from the reaction gas supply unit to the gas supply hole through a pipe (not shown), etc., or may be provided so that the reaction gas is sprayed onto the surface of the cathode current collector plate on the side opposite to the contact surface with the cathode. Also, it is environmentally preferable to use the factory exhaust gas discharged from the factory as this reaction gas.

[0085] 〔CO generation method〕 Next, the CO generation method using the carbon dioxide reduction electrolysis device according to this embodiment will be described. First, CO2, which is a reaction gas as a raw material, is supplied to the carbon dioxide reduction electrolysis device in a gas phase state by a reaction gas supply unit (not shown). At this time, CO2 is supplied to the cathode, for example, through the gas supply hole provided in the cathode current collector plate. Next, the CO2 supplied to the cathode comes into contact with the catalyst layer of the cathode. When a cation exchange membrane is used as the ion exchange membrane, the reduction reactions of the aforementioned reaction formulas (1) and (2) occur. When an anion exchange membrane is used as the solid electrolyte, the reduction reactions of the aforementioned reaction formulas (3) and (4) occur, thereby generating synthesis gas containing at least CO and H2. Next, the synthesis gas containing the generated CO and H2 is sent to a gas recovery device (not shown) through the gas recovery holes provided in the cathode current collector plate and recovered for each predetermined gas.

[0086] <Water electrolysis device> The water electrolysis device according to this embodiment includes the ion exchange membrane-electrode assembly according to this embodiment. Since the water electrolysis device according to this embodiment includes the ion exchange membrane-electrode assembly according to this embodiment, short circuits are less likely to occur and the electrolysis activity is high. In the water electrolysis device, the electrolytic solution is preferably pure water or an aqueous solution with a pH of 12 or higher. For example, an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, etc. can be mentioned.

[0087] 〔H2 generation method〕 Next, a method for generating H2 using the water electrolysis device according to this embodiment will be described. First, H2O is supplied to the water electrolysis device in a gaseous state or in a liquid phase as a raw material. At this time, H2O is supplied to the cathode, for example, through the gas supply holes provided in the cathode current collector plate. Next, the H2O supplied to the cathode comes into contact with the catalyst layer on the cathode side. When a cation exchange membrane is used as the ion exchange membrane, the reduction reaction of the aforementioned reaction formula (2) occurs. When an anion exchange membrane is used as the ion exchange membrane, the reduction reaction of the aforementioned reaction formula (4) occurs, thereby generating H2. Next, the generated H2 is sent to a gas recovery device through the gas recovery holes provided in the cathode current collector plate and recovered.

[0088] <Ammonia Electrolytic Synthesis Device> The ammonia electrolytic synthesis device according to this embodiment includes the ion exchange membrane - electrode assembly according to this embodiment. Since the ammonia electrolytic synthesis device according to this embodiment includes the ion exchange membrane - electrode assembly according to this embodiment, short - circuit is less likely to occur and the electrolytic activity is high. In the ammonia electrolytic synthesis device, the electrolytic solution is preferably pure water, an aqueous solution, or an organic electrolytic solution. For example, ammonium salt aqueous solution, sulfate aqueous solution, borate aqueous solution, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, sodium chloride aqueous solution, sulfuric acid aqueous solution, lithium perchlorate alcohol solution, etc. can be mentioned.

[0089] [NH3 Generation Method] Next, the NH3 generation method using the ammonia electrolytic synthesis device according to this embodiment will be described. First, N2 is supplied to the ammonia electrolytic synthesis device in a gaseous state as a raw material. At this time, N2 is supplied to the cathode, for example, through the gas supply hole provided in the cathode current collector plate. Next, when the N2 supplied to the cathode contacts the catalyst layer of the cathode, when a cation exchange membrane is used as the ion exchange membrane, the reduction reaction of reaction formula (7) occurs, and when an anion exchange membrane is used as the ion exchange membrane, the reduction reaction of reaction formula (8) occurs, thereby generating NH3.

[0090] N2+6H + +6e - →2NH3(7) N2+6H2O+6e - →2NH3+6OH - (8)

[0091] Next, the generated NH3 is sent to a gas recovery device through the gas recovery hole provided in the cathode current collector plate, for example, and is recovered.

[0092] <Fuel Cell> The fuel cell according to this embodiment includes the ion exchange membrane - electrode assembly according to this embodiment. By including the ion exchange membrane - electrode assembly according to this embodiment, the fuel cell according to this embodiment is less likely to short - circuit and has high power generation performance.

[0093] 〔Power generation method〕 Next, a power generation method using the fuel cell according to this embodiment will be described. First, H2 is supplied to the fuel cell in the gas phase as fuel. At this time, H2 is supplied to the anode, for example, through the gas supply holes provided in the anode current collector plate. Next, when the H2 supplied to the anode contacts the catalyst layer of the anode, if a cation exchange membrane is used as the ion exchange membrane, the reduction reaction of reaction formula (9) occurs, and if an anion exchange membrane is used as the ion exchange membrane, the reduction reaction of reaction formula (10) occurs, thereby generating electricity.

[0094] H2→2H + +2e - (9) H2+2OH - →2H2O+2e - (10)

Examples

[0095] Next, the technology of the present disclosure will be specifically described by way of examples, but the technology of the present disclosure is not limited by these examples in any way.

[0096] 〔Example 1〕 (Manufacture of anode) Iridium oxide catalyst [manufactured by Heraeus] and binder resin [Nafion (registered trademark) DE2020, manufactured by Chemours] were mixed at a ratio such that the mass ratio of the solid content was catalyst: binder resin = 7:1 to obtain a mixture. The mixture was dispersed in an isopropanol - water mixture to prepare a catalyst dispersion. As the base material layer, an aggregate sheet 1 of titanium particles [manufactured by Toho Titanium Co., Ltd., trade name: WEBTi (registered trademark), porosity: 61%] was used. The porosity is a catalog value. 100 titanium particles contained in the aggregate sheet 1 were randomly selected, and their major axis diameter (a) and minor axis diameter (b) were measured using a scanning electron microscope. The number average value (aspect ratio) of the b / a value was 2. Also, in the photographic observation of the surface of the base material layer by a scanning electron microscope, for 100 randomly extracted openings, the openings were approximated as ellipses and their major axes were measured. As a result, the average value was 15 μm. The base material layer was heated to 90 °C, and a catalyst dispersion was applied to the base material layer from a spraying device in a state where it was mixed with pressurized air and atomized. The spraying of the catalyst dispersion was stopped when the supported amounts of the catalyst and the binder resin (total amount of the catalyst and the binder resin) reached 2 mg / cm 2 and the anode 1 was manufactured. Note that as the spraying device, an external mixing type two-fluid nozzle (manufactured by Appiros Co., Ltd., trade name: "LPVN (registered trademark) 10") was used.

[0097] (Manufacture of the cathode) In a beaker, 1.1 mmol of pentaethylenehexamine and 0.7 mmol of nickel(II) chloride hexahydrate were mixed with 0.4 g of a carbon black carrier having a primary particle diameter of 30 nm in 15 mL of ethanol, and the resulting ethanol dispersion was irradiated with ultrasonic waves for 10 minutes. Then, ethanol was evaporated by heating and drying the ethanol dispersion, and the obtained mixture was heated in an inert gas at 900 °C for 10 seconds or more using a firing furnace and fired. Then, the product was washed with an aqueous sulfuric acid solution, the solid was recovered using a suction filter, and the solid was vacuum dried at 60 °C overnight to obtain a catalyst powder (intermediate) supporting the Ni complex.

[0098] Furthermore, 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 the catalyst powder was pulverized for 20 minutes at 800 rpm using a planetary ball mill apparatus, and the catalyst slurry was recovered. The catalyst slurry was washed again 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 powder. 22 mg of the obtained catalyst powder was dispersed in ethanol to form a dispersion, and 2 mg of "Nafion (registered trademark)" (cation exchange resin) manufactured by Chemours was mixed as an ionomer with respect to the dispersion. After mixing, the dispersion was irradiated with ultrasonic waves for 10 minutes, and the dispersion was exposed to a vacuum chamber with a reduced pressure environment of 10 kPa (absolute pressure) for 10 minutes. Then, using a spray coater, the dispersion was applied onto a gas diffusion layer provided with a microporous layer so that the supported amount during drying was 1 to 2 mg / cm 2 to obtain a cathode (negative electrode) 1. The cathode has a coating film of the dispersion as a catalyst layer.

[0099] (Manufacture of ion exchange membrane - electrode assembly) An anion exchange membrane (ion exchange membrane A) with a thickness of 30 μm, a cathode (negative electrode) 1, and an anode (positive electrode) 1 were laminated and pressure-bonded to obtain an ion exchange membrane - electrode assembly 1. The ion exchange membrane A is a fluororesin having an aromatic ring in the main chain and a quaternary ammonium group bonded to the main chain as a side chain (base point density 2.1 mmol / cm 3 ).

[0100] [Example 2] In the production of the anode (positive electrode) 1, in place of the aggregate sheet 1 as the base material layer, an aggregate sheet 2 of titanium particles [manufactured by Toho Titanium Co., Ltd., WEBTi (registered trademark), porosity 45%] was used, and the anode (positive electrode) 2 was produced in the same manner as in Example 1. The porosity of the aggregate sheet 2 is a catalog value. 100 titanium particles contained in the aggregate sheet 2 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 (aspect ratio) of the b / a value was 2. In addition, in the photographic observation of the surface of the base material layer using a scanning electron microscope, for 100 randomly extracted openings, when the openings were approximated by ellipses and their major axes were measured, the average value was 10 μm. In the production of the ion exchange membrane-electrode assembly 1, an ion exchange membrane-electrode assembly was produced in the same manner as in Example 1 except that the anode (positive electrode) 2 was used instead of the anode (positive electrode) 1, and it was designated as the ion exchange membrane-electrode assembly 2.

[0101] [Example 3] In the production of the ion exchange membrane-electrode assembly 1, an ion exchange membrane-electrode assembly was produced in the same manner as in Example 1 except that the ion exchange membrane B was used instead of the ion exchange membrane A, and it was designated as the ion exchange membrane-electrode assembly 3. Here, the ion exchange membrane B is a 20-μm-thick anion exchange membrane, a fluororesin [manufactured by Versogen, PiperION (registered trademark)] having an aromatic ring in the main chain and a cyclic quaternary ammonium group bonded to the main chain as a side chain.

[0102] [Comparative Example 1] In the production of the anode (positive electrode) 1, an anode (positive electrode) 101 was produced in the same manner as in Example 1 except that a titanium nonwoven fabric (manufactured by Taiyo Wire Mesh Co., Ltd., porosity 56%) was used instead of the aggregate sheet 1 as the base material layer. The porosity of the titanium nonwoven fabric is a catalog value. 100 titanium fibers contained in the titanium nonwoven fabric were randomly selected, and their major axis length (a') and minor axis diameter (b') were measured using a scanning electron microscope. The number average value (aspect ratio) of the b' / a' value was more than 100. In addition, in the photographic observation of the surface of the base material layer using a scanning electron microscope, for 100 randomly extracted openings, when the openings were approximated by ellipses and their major axes were measured, the average value was 35 μm. In the production of the ion exchange membrane-electrode assembly 1, an ion exchange membrane-electrode assembly was produced in the same manner as in Example 1 except that the anode (positive electrode) 101 was used instead of the anode (positive electrode) 1, and it was designated as the ion exchange membrane-electrode assembly 101.

[0103] [Comparative Example 2] In the production of the ion exchange membrane-electrode assembly 101, an ion exchange membrane-electrode assembly was produced in the same manner as in Comparative Example 1 except that ion exchange membrane B was used instead of ion exchange membrane A, and it was designated as ion exchange membrane-electrode assembly 102.

[0104] <Evaluation> 1. Evaluation of electrolysis efficiency (CO production current density) In the ion exchange membrane-electrode assemblies 1 to 3 of Examples 1 to 3 and the ion exchange membrane-electrode assemblies 101 to 102 of Comparative Examples 1 and 2, each anode (positive electrode) had a structure in contact with an electrolytic solution (0.5 mol / L aqueous KHCO3 solution) tank, and a carbon dioxide reduction electrolysis apparatus was assembled. Using the produced apparatus, pure CO2 was supplied to the cathode. Under the condition that the cell was heated to 70°C, the applied potential of the cathode was set to -2.6 V with respect to the anode, and CO2 was electrolyzed to produce CO, and the CO production current density [mA / cm 2 was measured. The results are shown in Table 1.

[0105] 2. Short circuit evaluation (leakage current density) In the electrolysis efficiency evaluation, the current density that did not contribute to the production of CO and H2 was measured and taken as the leakage current density [mA / cm 2 . The results are shown in Table 1.

[0106]

Table 1

[0107] As shown in Table 1, leakage current density was detected in the carbon dioxide reduction electrolysis apparatuses of Comparative Examples 1 and 2 that used titanium nonwoven fabric as the anode substrate, indicating that a short circuit occurred. On the other hand, the short circuit evaluation (leakage current density) of Examples 1 to 3 was "N.D." (Not Detected). That is, under the conditions where leakage current occurred in the carbon dioxide reduction electrolysis apparatuses of Comparative Examples 1 and 2, no leakage current density was detected, and the short circuit suppression effect was confirmed. Also, the same effect was confirmed with the two types of ion exchange membranes.

[0108] It was also confirmed that the CO production current density increased by an amount equal to or greater than the amount of the leak current density eliminated. Despite the fact that the current generated by the electrolysis reaction is less likely to flow than the current flowing through the short-circuit region due to the presence of the reaction overvoltage, such a significant increase in the current density was observed. This is presumably because the effective area for the anodic reaction has increased due to the change in the substrate structure.

[0109] FIG. 1 shows an electron micrograph of the surface of the substrate layer (aggregate sheet 1) on the anode side of Example 1, and FIG. 4 shows an electron micrograph of the surface of the substrate layer (titanium nonwoven fabric) on the anode side of Comparative Example 1. Further, FIG. 5 shows an electron micrograph of the anode surface of Example 1, and FIG. 6 shows an electron micrograph of the anode surface of Comparative Example 1. As can be seen from the comparison between FIG. 1 and FIG. 4, the anode-side substrate layer (aggregate sheet 1) of Example 1 has a smaller opening area and an increased effective area for the anodic reaction compared to the anode-side substrate layer (titanium nonwoven fabric) of Comparative Example 1. This can also be confirmed from the comparison between FIG. 5 and FIG. 6, which are anodes on which the catalyst layer is formed on the substrate layer. The area of the opening of the anode-side substrate layer of Comparative Example 1 was measured with the surface of the substrate layer being the surface formed by connecting the upper ends of adjacent fibers in the photograph observation of the substrate layer by a scanning electron microscope, and the opening being the region where there is a depression of 5% or more of the total thickness of the substrate layer in the direction perpendicular to the surface of the substrate layer and inward of the substrate layer.

[0110] In addition, when a titanium nonwoven fabric is used as the anode-side substrate layer, protrusions are caused by the fiber ends as shown by the arrows in FIG. 6, which is one of the causes of short circuit.

[0111] When an aggregate of metal particles is used as the anode substrate, the current density is higher at 61% than at 45% porosity (Example 1 compared to Example 2). This is presumably because increasing the porosity enables the supply and discharge of reactants (liquid water) and products (O2 gas) to be carried out efficiently.

Industrial Applicability

[0112] According to this embodiment, in various electrolytic devices and batteries such as a carbon dioxide reduction electrolytic device, a water electrolytic device, an ammonia electrolytic synthesis device, and a fuel cell, short circuits are less likely to occur, and high electrolytic activity or power generation performance can be obtained. For example, in the carbon dioxide reduction electrolytic device provided with the anode according to this embodiment, by using renewable energy such as a solar cell for the voltage application unit with, for example, CO2 gas discharged from a factory as a raw material, a synthesis gas containing at least CO and H2 can be generated at a desired production ratio. The synthesis gas thus generated can be used to produce fuel base materials, chemical raw materials, etc. by methods such as Fischer-Tropsch synthesis and methanation.

Explanation of symbols

[0113] 10 Cathode-side base material (gas diffusion layer) 20 Cathode-side catalyst layer 22 Resin 24 Catalyst 30 Ion exchange membrane (solid electrolyte) 40 Anode-side catalyst layer 42 Resin 44 Catalyst 50 Anode-side base material 60 Ion exchange membrane-electrode assembly 100 Cathode current collector 200 Cathode 300 Ion exchange membrane (solid electrolyte) 400 Anode 500 Anode current collector 600 Electrolyte solution 700 Voltage application unit 800 Carbon dioxide reduction electrolytic device

Claims

1. a base layer including at least an aggregate of metal particles having an aspect ratio of 10 or less, the aspect ratio being a number average value of b / a, where a is the major axis diameter of the metal particles and b is the minor axis diameter of the metal particles, as measured for 100 randomly selected metal particles using a scanning electron microscope; A catalyst layer containing at least a catalyst and a resin; an anode comprising:

2. 2. The anode according to claim 1, wherein, in photographic observation of the surface of the substrate layer using a scanning electron microscope, the average major axis of 100 openings randomly selected is 20 μm or less.

3. 3. The anode according to claim 1, wherein the substrate layer has a porosity of 30% or more.

4. 3. The anode according to claim 1 or 2, wherein the metal of the metal particles contains one or more selected from the group consisting of titanium, nickel, cobalt, iron, tin, tungsten, tantalum, copper, silver, gold, platinum, iridium, ruthenium, and palladium.

5. 3. An ion exchange membrane-electrode assembly comprising a cathode, the anode according to claim 1 or 2, and an ion exchange membrane.

6. 6. The ion exchange membrane-electrode assembly according to claim 5, wherein the ion exchange membrane comprises an anion exchange membrane.

7. 6. The ion exchange membrane-electrode assembly according to claim 5, wherein the ion exchange membrane has an average thickness in a dry state of 60 μm or less.

8. A carbon dioxide reduction electrolysis device comprising the ion exchange membrane-electrode assembly according to claim 5.

9. A water electrolysis device comprising the ion exchange membrane-electrode assembly according to claim 5.

10. An apparatus for electrolytic synthesis of ammonia, comprising the ion exchange membrane-electrode assembly according to claim 5.

11. A fuel cell comprising the ion exchange membrane-electrode assembly according to claim 5.

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