Method for producing gas diffusion layer, cathode, ion exchange membrane-electrode assembly, and solid electrolyte electrolysis device

Abstract

Provided is a method for producing a gas diffusion layer (10) having a carbon fiber layer (10a) containing carbon fibers and a porous layer (10c) containing a conductive substance and a binder resin, the gas diffusion layer (10) being produced by a spray method or a vapor phase method. A conductive substance (P) is applied from the surface (10b) side of a carbon fiber layer (10a) of a laminate having the carbon fiber layer (10a) and a porous layer (10c). This production method makes it possible to produce a gas diffusion layer having high electrolytic activity.

Description

Technical Field

[0001] The technology of the present application relates to a method for manufacturing a gas diffusion layer, a cathode, an ion exchange membrane-electrode assembly, and a solid electrolyte electrolysis device. Background Art

[0002] Carbon dioxide is emitted when energy is extracted from fossil fuels and other sources. Rising atmospheric carbon dioxide concentrations are believed to be one of the causes of global warming. Carbon dioxide is an extremely stable substance, and therefore, has traditionally had few uses. However, in an era of increasingly severe global warming, there is a demand for new technologies that can convert carbon dioxide into other substances and recycle it as a resource. For example, carbon dioxide reduction devices capable of directly reducing gaseous carbon dioxide are being developed.

[0003] In the carbon dioxide reduction device, the polymer electrolyte type electrolysis device using a polymer electrolyte has attracted much attention from the viewpoint of being able to directly reduce gaseous carbon dioxide and being able to fully reduce the mobility resistance of ions by using a thin film polymer electrolyte. The carbon dioxide reduction cathode (cathode) generally has a structure in which a catalyst layer including a catalyst is stacked on a gas diffusion layer. For example, the gas diffusion layer generally uses a porous material with conductivity in order to feed carbon dioxide into the catalyst layer, and various studies have been conducted on the improvement of conductivity, gas diffusivity, etc.

[0004] For example, Patent Document 1 proposes a gas diffusion electrode comprising carbon fibers, carbon powder, and a fluororesin containing a hydrophilic organic solvent as a binder. This method discloses a process in which the mixture is applied to the carbon fibers using a doctor blade method, followed by immersion in water to cure the resin and form pores.

[0005] Patent Document 2 discloses a method of forming a mixture containing carbon fibers, carbon powder, and a thermosetting resin into a sheet and thermally curing the sheet to form a gas diffusion layer.

[0006] Furthermore, Patent Document 3 discloses a gas diffusion electrode for a fuel cell in which conductivity is improved by forming a metal coating on a conductive porous body such as carbon fibers by sputtering.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 11-31515

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2010-15908

[0011] Patent Document 3: Japanese Patent Application Laid-Open No. 2007-095586 Summary of the Invention

[0012] Problems to be solved by the invention

[0013] However, the doctor blade method disclosed in Patent Document 1 applies an excessive amount of the mixture to the carbon fibers, making it impossible to control the coating amount and ensuring the necessary pores for gas diffusion. Furthermore, conductive material adheres to the surface of the gas diffusion layer on the side where the catalyst layer is to be layered, creating the negative effect of acting as an active site for unintended reactions (side reactions). Furthermore, in addition to the difficulty of producing uniform and large-area gas diffusion layers and electrodes, there are also issues with the numerous subsequent steps after coating, which can lead to high manufacturing costs.

[0014] The method disclosed in Patent Document 2 suffers from the high costs of the thermosetting resin and the thermosetting process, as well as the difficulty in controlling the structure and, consequently, the physical properties of the resulting thermosetting product. Furthermore, as in Patent Document 1, it is difficult to obtain sufficient pores for gas diffusion.

[0015] In the invention disclosed in Patent Document 3, when metal is sputtered only on the gas diffusion layer, the metal particles surround one side of the catalyst layer and act as other catalysts for the same reason as the problem in Patent Document 1. Therefore, it is possible to trigger a reaction different from the CO2 reduction reaction (for example, a reaction to generate H2 through water reduction), which leads to the problem that it cannot be applied to electrolytic cells for CO2 reduction.

[0016] The technology of the present application is developed in view of the above situation. The subject of the technology of the present application is to provide a method for manufacturing a gas diffusion layer with high electrolytic activity, a cathode having the gas diffusion layer, an ion exchange membrane-electrode assembly and a solid electrolyte electrolysis device, the purpose of which is to solve the problem.

[0017] Means used to solve problems

[0018] <1> A method for producing a gas diffusion layer, wherein the gas diffusion layer comprises a carbon fiber layer comprising carbon fibers and a porous layer comprising a conductive substance 1 and a binder resin, wherein the conductive substance 2 is applied to the surface of the carbon fiber layer of a laminate comprising the carbon fiber layer and the porous layer by a spraying method or a vapor phase method.

[0019] <2> according to <1> In the method for manufacturing a gas diffusion layer, the porosity of the porous layer is 10-60%, and the average pore diameter is 10-500 nm.

[0020] <3> according to <1> or <2> In the method for producing a gas diffusion layer, the conductive material 1 and the conductive material 2 are each independently one or more selected from carbon materials and metals.

[0021] <4> according to <1> ~ <3> In any one of the methods for producing a gas diffusion layer, a mixed solution containing the conductive substance 2 and a binder resin is sprayed from the surface side of the carbon fiber layer.

[0022] <5> according to <4> The method for manufacturing a gas diffusion layer, wherein the mixed solution is such that the total amount of the conductive material 2 and the binder resin in the mixed solution is 0.05 to 2 mg / cm 2 way of spraying.

[0023] <6> according to <1> ~ <3> The method for producing a gas diffusion layer according to any one of the above aspects, wherein the conductive material 2 is applied from the surface side of the carbon fiber layer by vapor deposition or sputtering.

[0024] <7> according to <6> The method for manufacturing a gas diffusion layer, wherein the amount of the conductive material 2 provided is 0.5 to 5 μg / cm 2 .

[0025] <8> cathode, which has a <1> ~ <7> A gas diffusion layer manufactured by the method for manufacturing a gas diffusion layer described in any one of the preceding claims, wherein the gas diffusion layer comprises a carbon fiber layer and a porous layer, the carbon fiber layer comprising a conductive substance 2 and carbon fibers, a portion of the carbon fibers being covered by the conductive substance 2, the porous layer comprising a conductive substance 1 and a binder resin, and the cathode having a catalyst layer on the porous layer side.

[0026] <9> A cathode having a gas diffusion layer, wherein the gas diffusion layer has a carbon fiber layer and a porous layer, wherein the carbon fiber layer contains a conductive substance 2 and carbon fibers, wherein a portion of the carbon fibers is covered with the conductive substance 2, and the conductive substance 2 is present from the surface to a position at a depth of more than 60%, wherein the porous layer contains a conductive substance 1 and a binding resin, has a porosity of 10 to 60%, and an average pore diameter of 10 to 500 nm, and wherein the cathode has a catalyst layer on the porous layer side.

[0027] <10> according to <8> or <9> The cathode, wherein the carbon fiber layer further comprises a binder resin, and the loading amount of the conductive material 2 and the binder resin is 0.05 to 2 mg / cm 2 .

[0028] <11> according to <8> ~ <10> The cathode according to any one of the preceding claims, wherein the conductive material 1 and the conductive material 2 are each independently one or more selected from carbon materials and metals.

[0029] <12> Ion exchange membrane-electrode assembly having <8> ~ <11> The cathode, solid electrolyte and anode described above.

[0030] <13> according to <12> In the ion exchange membrane-electrode assembly, the solid electrolyte is an anion exchange membrane.

[0031] <14> A solid electrolyte electrolysis device comprising:

[0032] <8> ~ <11> The cathode of any one of the above;

[0033] an anode forming a pair of electrodes with the aforementioned cathode;

[0034] a solid electrolyte sandwiched between the cathode and the anode in a contact state; and

[0035] A voltage applying unit applies a voltage between the cathode and the anode.

[0036] <15> according to <14> In the solid electrolyte electrolysis device, the solid electrolyte is an anion exchange membrane.

[0037] Effects of the Invention

[0038] According to the technology of the present application, a method for producing a gas diffusion layer having high electrolytic activity, a cathode including the gas diffusion layer, an ion exchange membrane-electrode assembly, and a solid electrolyte electrolysis device can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of an ion exchange membrane-electrode assembly preferably used in this embodiment.

[0040] Figure 2 This is a schematic diagram of a stack of gas diffusion layers and catalyst layers.

[0041] Figure 3 This is a schematic diagram showing an example of a method for producing a gas diffusion layer that can be preferably used in this embodiment.

[0042] Figure 4 This is a schematic diagram of a solid electrolyte electrolysis device that can be preferably used in this embodiment.

[0043] Figure 5 This is an electron microscope image of a cross section of the carbon fibers of the gas diffusion layer of Example 1.

[0044] Figure 6 This is an electron microscope image of a cross section of the carbon fibers of the gas diffusion layer of Example 2.

[0045] Figure 7 This is an electron microscope image of a cross section of carbon fibers of the gas diffusion layer of Comparative Example 2.

[0046] Figure 8 This is the depth-direction distribution of the detection number ratio of Ag / C fluorescent X-rays near the interface between the carbon fiber layer and the porous layer in the gas diffusion layer of Example 1.

[0047] Figure 9 This is the depth-direction distribution of the S / C fluorescent X-ray detection number ratio near the interface between the carbon fiber layer and the porous layer in the gas diffusion layer of Example 2. DETAILED DESCRIPTION

[0048] The upper and lower limits of the numerical ranges described in this specification may be arbitrarily combined. For example, when "A to B" and "C to D" are described as numerical ranges, the numerical ranges of "A to D" and "C to B" are also included in the scope of this application.

[0049] In addition, the numerical range "lower limit value to upper limit value" described in this specification means more than the lower limit value and less than the upper limit value unless otherwise specified.

[0050] <Method for Manufacturing Gas Diffusion Layer>

[0051] The method for manufacturing a gas diffusion layer described in this embodiment is as follows: the gas diffusion layer has a carbon fiber layer containing carbon fibers and a porous layer containing a conductive substance 1 and a binder resin. In the method for manufacturing the gas diffusion layer, the conductive substance 2 is applied to the surface side of the carbon fiber layer of a laminate having the carbon fiber layer and the porous layer by a spraying method or a vapor phase method.

[0052] The gas diffusion layer manufactured by the gas diffusion layer manufacturing method described in this embodiment can be used not only in carbon dioxide reduction electrolysis devices, but also in water electrolysis devices, fuel cells, gas diffusion electrodes for air batteries, etc. However, in this specification, the manufacturing method of the gas diffusion layer in the carbon dioxide reduction electrolysis device is mainly described.

[0053] First, the structure of the gas diffusion layer will be described.

[0054] Figure 1 A schematic diagram showing an ion exchange membrane-electrode assembly preferably used in this embodiment is shown. Figure 1The ion exchange membrane-electrode assembly 50 is shown, which includes a gas diffusion layer 10, a catalyst layer 20, a solid electrolyte 30, and an anode 40. Details of the ion exchange membrane-electrode assembly 50 will be described later.

[0055] like Figure 1 As shown, the gas diffusion layer 10 is adjacent to the catalyst layer 20 , absorbs carbon dioxide (CO 2 ) from the outside air, and supplies the carbon dioxide (CO 2 ) to the catalyst layer 20 .

[0056] Figure 2 Schematic diagram of a stack of gas diffusion layer 10 and catalyst layer 20. Gas diffusion layer 10 includes carbon fiber layer 10a and porous layer 10c. Catalyst layer 20 includes catalyst 24 and is adjacent to gas diffusion layer 10, strictly speaking, adjacent to porous layer 10c. Figure 2 , the arrow D1 indicates the depth direction of the carbon fiber layer 10a as viewed from the surface 10b of the carbon fiber layer 10a. The depth direction of the carbon fiber layer 10a can also be understood as the stacking direction of the gas diffusion layer 10 and the catalyst layer 20, or as the thickness direction of the carbon fiber layer 10a.

[0057] Figure 3 This is a schematic diagram showing an example of a method for producing a gas diffusion layer that can be preferably used in this embodiment. Figure 3 The following situation is shown: in a gas diffusion layer 10 having a stack of a carbon fiber layer 10a and a porous layer 10c, a conductive substance P (conductive substance 2) is applied from a coating device C toward the surface 10b of the carbon fiber layer 10a by a spray method or a vapor phase method, and the conductive substance P (conductive substance 2) is attached to the depth direction D1 of the carbon fiber layer 10a.

[0058] In the method for producing the gas diffusion layer preferably used in this embodiment, "applying the conductive material 2 from the surface side of the carbon fiber layer by a spraying method or a vapor phase method" means: Figure 3 In this embodiment, the conductive material P (conductive material 2) is applied from the coating device C toward the surface 10b of the carbon fiber layer 10a. This means that the conductive material P (conductive material 2) is applied not only to the surface 10b of the carbon fiber layer 10a, but also to the interior of the carbon fiber layer 10a in the depth direction D1. Specifically, the conductive material 2 can be applied to a position extending from the surface 10b toward a depth direction D1 that is 60% or more of the thickness of the carbon fiber layer.

[0059] It should be noted that in Figure 3 The direction D2 of applying the conductive material P (conductive material 2) is shown to be perpendicular to the surface 10b of the carbon fiber layer 10a, but it does not necessarily need to be perpendicular. The conductive material P (conductive material 2) can be applied at an acute to obtuse angle relative to the surface 10b.

[0060] Here, if the carbon fiber layer is, for example, a hexahedral flat plate, all six sides of the carbon fiber layer are surfaces of the carbon fiber layer. However, in the method for manufacturing a gas diffusion layer preferably used in this embodiment, the carbon fiber layer 10a is used adjacent to the porous layer 10c. Therefore, the conductive material P (conductive material 2) applied from the coating device C to the surface of the carbon fiber layer 10a does not contact the adjacent surface of the porous layer 10c.

[0061] Therefore, in this embodiment, the "surface of the carbon fiber layer" can be changed to "the exposed surface of the carbon fiber layer". Furthermore, in particular, the surface with the largest area among the surfaces of the carbon fiber layer is regarded as the "surface of the carbon fiber layer" in the method for manufacturing the gas diffusion layer described in this embodiment. Figure 3 In the text, the surface 10b of the carbon fiber layer 10a is mainly referred to as the "surface of the carbon fiber layer." However, this does not exclude the possibility that the conductive material P (conductive material 2) applied from the coating device C enters the side surfaces of the carbon fiber layer 10a and adheres to the side surfaces and interior of the carbon fiber layer 10a.

[0062] The carbon fiber layer is usually a porous layer with a structure in which carbon fibers are stacked in a direction perpendicular to the plane and spread out in a grid pattern along the plane. Figure 2 The conductivity in the depth direction D1 (the same direction and the opposite direction) is low, and the resistance tends to become larger, thus causing a decrease in electrolysis efficiency caused by the voltage drop during electrolysis. The potential drop caused by resistance is proportional to the current density, so this efficiency reduction occurs particularly significantly when a high current density is applied. This problem occurs not only in CO2 electrolysis, but also often occurs in water electrolysis, fuel cells, and air batteries.

[0063] Therefore, gas diffusion electrodes often use a gas diffusion layer containing a highly conductive carbon powder (amorphous carbon; carbon black) in addition to a carbon substrate. However, as described in Patent Documents 1 to 3, conventional methods for imparting conductivity have the disadvantage of making it difficult to secure the pores necessary for gas diffusion, or causing the conductive material to adhere to the surface of the gas diffusion layer on the side where the catalyst layer is to be deposited, thereby acting as an active site for unintended reactions (side reactions).

[0064] This is believed to be because, when the surface of the gas diffusion layer is solidly coated using the doctor blade method described in Patent Document 1, or when the gas diffusion layer is immersed in a solution containing a conductive material, the carbon fibers are almost entirely covered with the conductive material, resulting in a thicker coating. Consequently, the hydrophobicity inherent in the carbon fibers in the gas diffusion layer obtained using conventional conductivity-imparting methods is impaired. Furthermore, the carbon fiber network is covered with a thick coating, impairing gas diffusivity.

[0065] In contrast, the method for producing a gas diffusion layer according to the present embodiment can produce a gas diffusion layer having high electrical conductivity, hydrophobicity, and electrolytic activity in the depth direction.

[0066] It is believed that by applying the conductive material 2 from the surface side of the carbon fiber layer by spraying or vapor phase method, the conductive material 2 can be attached to a portion of the surface of the carbon fibers, thereby maintaining the hydrophobicity of the carbon fibers and obtaining a highly hydrophobic gas diffusion layer.

[0067] It is also considered that the conductive material 2 applied from the surface side of the carbon fiber layer passes through the pores of the carbon fiber layer and reaches the carbon fiber surface in the depth direction of the carbon fiber layer, thereby obtaining a gas diffusion layer with high conductivity in the depth direction.

[0068] Furthermore, it is considered that since the coating thickness of the conductive substance 2 on the carbon fiber surface can be reduced, the gas diffusivity can be maintained.

[0069] In addition, since the gas diffusion layer is highly hydrophobic, when it is used in an electrolysis device containing an electrolyte, the electrolyte leaking through the catalyst layer can be prevented from soaking the gas diffusion layer, making it less likely to impair the supply of CO2 to the catalyst layer.

[0070] Therefore, it is considered that the CO 2 reduction reaction in the catalyst layer can be enhanced and the electrolysis activity can be improved.

[0071] Hereinafter, the method of applying the conductive material 2 will be described in more detail.

[0072] [Method of applying conductive material 2]

[0073] In the method for producing a gas diffusion layer according to the present embodiment, the conductive material 2 is applied from the surface side of the carbon fiber layer by a spray method or a vapor phase method.

[0074] By applying the conductive material 2 using a spray or vapor phase method, it is possible to improve the conductivity of the carbon fiber layer using a simple and effective method without adversely affecting the catalyst layer while maintaining the porous structure using carbon fibers. By applying the conductive material 2 using a spray or vapor phase method, it is possible to gradually accumulate fine conductive material particles on the order of μm or less on the carbon fibers. Therefore, it is easy to control the amount of conductive material 2 loaded on the carbon fibers, and it is also less likely to clog the μm-level pores of the carbon fibers. Furthermore, the same apparatus as used in the catalyst layer production process can be used, thus reducing manufacturing costs.

[0075] The component applied by the spray method or the vapor phase method only needs to contain the conductive substance 2 , and may be a mixture containing the conductive substance 2 and a binder resin, a solvent, etc., or may be the conductive substance 2 alone.

[0076] As a method for imparting the conductive material 2, a spray method (also referred to as a spray method) of spraying the conductive material 2 can be listed as a spray method, and a vapor deposition / sputtering method of imparting the conductive material 2 by vapor deposition or sputtering can be listed as a gas phase method.

[0077] (Conductive material 2)

[0078] As the conductive substance 2 , for example, carbon materials and metals can be used.

[0079] Examples of carbon materials include carbon black (furnace black, acetylene black, Ketjen black, thermal black, etc.), activated carbon, graphite, carbon nanotubes, carbon nanofibers, carbon nanohorns, graphene nanosheets, nanoporous carbon, and the like. Among these, carbon black is preferred from the viewpoint of small primary particle size and low material cost.

[0080] Examples of the metal include silver, copper, aluminum, nickel, iron, and indium. Silver is preferred from the viewpoint of high stability and conductivity.

[0081] The conductive material 2 may use only one of the above-mentioned components or two or more of them.

[0082] To more efficiently apply the conductive material 2 to the carbon fiber layer by spraying, the conductive material 2 is preferably in a granular form. The primary particle size of the conductive material particles is preferably 10 to 100 nm, more preferably 10 to 50 nm. The primary particle size of the conductive material particles can be measured using a transmission electron microscope.

[0083] From the same viewpoint, the secondary particle size (aggregate particle size) of the conductive material particles is preferably small.

[0084] (Binder resin)

[0085] The binder resin is a component used to adhere the conductive material 2 to the carbon fibers, and an ionomer is preferably used. Furthermore, to avoid impairing the conductivity of the gas diffusion layer, the ionomer is preferably conductive, and more preferably a polymer electrolyte. The polymer electrolyte is further preferably an ion exchange resin. The ion exchange resin may be a cation exchange resin or an anion exchange resin, and is preferably an anion exchange resin.

[0086] In particular, when an anion exchange resin is used, the anion exchange resin itself has carbon dioxide adsorption capacity, ion conduction of the anion exchange resin is facilitated, and the electrolysis efficiency of carbon dioxide can be greatly improved.

[0087] Examples of the cation exchange resin include fluorine resins having a sulfonic group and styrene-divinylbenzene copolymers having a sulfonic group. Commercially available products may 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).

[0088] Examples of anion exchange resins include resins having one or more ion exchange groups selected from quaternary ammonium groups, primary amino groups, secondary amino groups, and tertiary amino groups. Commercially available products may also be used, and examples thereof include 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 Corporation).

[0089] From the viewpoint of improving conductivity, the basic site density of the anion exchange resin in a dry state is preferably 2.0 to 5.0 mmol / L. 3 , more preferably 2.5 mmol / 3 Above and less than 4.5mmol / 3 , more preferably 2.9 mmol / 3 Above and less than 4.5mmol / 3 .

[0090] The base point density of anion exchange resin can be determined by 1 It can be obtained by integrating the signal during HNMR measurement.

[0091] In addition, regarding the anion exchange resin, the dry state refers to a state in which the anion exchange resin does not contain free water. For example, the anion exchange resin can be made into a dry state by heating in a vacuum.

[0092] (Solvent)

[0093] The solvent is used as a dispersion medium for the conductive substance, and it is preferable to use a solvent that does not react with the conductive substance 2 and the binder resin.

[0094] Specific examples include alcohol, water, toluene, and dimethyl sulfoxide. Among them, alcohol is preferred, and ethanol is more preferred.

[0095] The solvent may be used alone or in combination of two or more.

[0096] In the mixed solution containing the conductive substance 2 and the binder resin, the ratio (a / r) of the mass (a) of the conductive substance 2 to the mass (r) of the binder resin is preferably 1 / 1 to 10 / 1, more preferably 2 / 1 to 8 / 1, and even more preferably 3 / 1 to 7 / 1.

[0097] When metal is used as the conductive material 2 , the conductive material 2 is preferably provided to the carbon fiber layer by vapor deposition or sputtering.

[0098] As described above, when a spray method is used, it is preferred to spray a mixed solution containing a conductive substance 2 and a binder resin from the surface side of the carbon fiber layer. When a vapor deposition / sputtering method is used, it is preferred to impart the conductive substance 2 from the surface side of the carbon fiber layer by vapor deposition or sputtering.

[0099] Next, the spray method and the vapor deposition / sputtering method will be described.

[0100] (Spray method)

[0101] In the spray method, for example, a mixed solution containing the conductive material 2 and the binder resin is sprayed from the surface side of the carbon fiber layer.

[0102] Specifically, for example, a spray device is used as Figure 3 The coating device C shown sprays the mixed solution onto the surface of the carbon fiber layer from a spray device. When spraying the mixed solution, the carbon fiber layer is preferably heated to 65-85°C and the mixed solution is mixed with pressurized air to form an atomized layer. Furthermore, to prevent the conductive material 2 from surrounding the catalyst layer-side surface of the carbon fiber layer, a porous layer is preferably provided on the catalyst layer-side surface of the carbon fiber layer.

[0103] The mixed solution may contain the conductive material 2 and the binder resin in the above-mentioned amount ratio (a / r).

[0104] The mixed solution preferably has a total concentration of the conductive material 2 and the binder resin of 0.05 to 2 mg / cm2 from the viewpoint of balancing the conductivity, hydrophobicity, and gas diffusivity of the carbon fiber layer. 2 It is preferably sprayed in a manner of 0.10 to 1.50 mg / cm 2 It is preferably sprayed in a manner of 0.15 to 1.00 mg / cm 2 way of spraying.

[0105] By spraying the mixed solution in the above range, the amount of the conductive substance 2 and the binder resin supported in the carbon fiber layer is within the same range as the total amount of the conductive substance 2 and the binder resin in the mixed solution.

[0106] (Evaporation / Sputtering method)

[0107] In the vapor deposition / sputtering method, the conductive material 2 (particularly a metal) is applied from the surface side of the carbon fiber layer by vapor deposition or sputtering, for example.

[0108] By depositing clusters or atoms of the conductive substance 2 on a portion of the carbon fibers, conductivity can be imparted in the depth direction while maintaining the hydrophobicity and gas diffusivity of the carbon fiber layer.

[0109] Specifically, for example, a vapor deposition device or a sputtering device is used as Figure 3 The coating device C shown applies the conductive material 2 to the surface of the carbon fiber layer from the vapor deposition device to the sputtering device. When applying the conductive material 2, it is preferable to perform vapor deposition or sputtering while replacing the inside of the device with a dilute inert gas (such as argon).

[0110] From the viewpoint of the balance among conductivity, hydrophobicity, and gas diffusivity of the carbon fiber layer, the amount of the conductive material 2 applied is preferably 0.5 to 5 μg / cm 2 , more preferably 0.7 to 4 μg / cm 2 More preferably, it is 1 to 3 μg / cm 2 .

[0111] By providing the conductive substance 2 in the above-mentioned range, the amount of the conductive substance 2 supported in the carbon fiber layer falls within the same range as the provided amount.

[0112] Gas diffusion layer

[0113] The gas diffusion layer manufactured by the method for manufacturing a gas diffusion layer according to this embodiment includes a carbon fiber layer and a porous layer.

[0114] (Carbon fiber layer)

[0115] The carbon fiber layer used in the method for producing a gas diffusion layer according to this embodiment includes carbon fibers.

[0116] Carbon fiber can be made of carbon paper or nonwoven fabric, and examples thereof include graphite carbon and glassy carbon.

[0117] The carbon fiber layer may further include a metal mesh such as titanium or SUS steel, or may be formed of carbon fibers alone.

[0118] It is preferable that the fiber layer does not contain a binder resin, that is, the content of the binder resin in the carbon fiber layer is 0% by mass.

[0119] (Porous layer)

[0120] The porous layer used in the method for producing the gas diffusion layer according to this embodiment includes a conductive substance 1 and a binder resin. The porous layer has a porous structure by laminating conductive substances with pores.

[0121] By including a porous layer in addition to the carbon fiber layer, the gas diffusion layer can prevent the conductive material 2 from adhering to the surface of the gas diffusion layer adjacent to the catalyst layer without impairing the conductivity and gas diffusivity of the gas diffusion layer. The porous layer is preferably located between the carbon fiber layer and the catalyst layer. The porous layer may be a single layer or may be two or more layers.

[0122] The porous layer preferably has a porosity of 10-60% and an average pore diameter of 10-500 nm. A porosity of 10% or greater improves the gas diffusion rate, while a porosity of 60% or less improves the catalyst layer's loading efficiency. Furthermore, an average pore diameter of 10 μm or greater improves the gas diffusion rate, while an average pore diameter of 500 μm or less improves the catalyst layer's loading efficiency.

[0123] The porosity of the porous layer is more preferably 10 to 50%, and further preferably 12 to 40%.

[0124] The average pore diameter of the porous layer is more preferably 30 to 450 nm, further preferably 60 to 400 nm.

[0125] The porosity and average pore size of the porous layer can be measured by mercury intrusion porosimetry (JIS Z 8890:2017) or X-ray CT (Computed Tomography).

[0126] The conductive substance 1 and the binder resin may be the conductive substance 2 and the binder resin described as the components of the mixed solution used when the conductive substance 2 is applied to the carbon fiber layer by spraying.

[0127] That is, the conductive material 1 contained in the porous layer can be made of carbon materials and metals as long as they are gas permeable, conductive, and can capture nanoparticles. They can be in sheet form such as graphene sheets or in mesh form such as titanium foam.

[0128] Among them, conductive material 1 is preferably carbon black, activated carbon, graphite, carbon nanotubes, carbon nanofibers, nanoporous carbon, aluminum, and titanium, and more preferably carbon black and carbon nanotubes. Conductive material 1 may be used alone or in combination of two or more.

[0129] The content of the conductive material 1 in the porous layer is preferably 50 to 99.9% by mass, more preferably 70 to 99% by mass. The content of the binder resin in the porous layer is preferably 0.1 to 50% by mass, more preferably 1 to 30% by mass.

[0130] As the porous layer, a commercially available gas diffusion layer in which a carbon fiber layer and a porous layer are laminated can be used.

[0131] The gas diffusion layer according to this embodiment manufactured as described above includes a carbon fiber layer containing a conductive substance 2 and carbon fibers, with a portion of the carbon fibers being covered with the conductive substance 2, and a porous layer containing a conductive substance 1 and a binder resin.

[0132] By the method for manufacturing the gas diffusion layer preferably used in this embodiment, the conductive material 2 in the carbon fiber layer is not only applied to the surface of the carbon fiber layer, but also applied to the interior of the carbon fiber layer in the depth direction. In other words, the conductive material 2 is present from the surface to a position that is 60% or more of the thickness of the carbon fiber layer in the depth direction. Here, the "surface of the carbon fiber layer" refers to the opposite side of the surface adjacent to the porous layer, which means Figure 2 and Figure 3 Surface 10b in.

[0133] The conductive material 2 is preferably present at 70% or more of the thickness of the carbon fiber layer in the depth direction from the surface of the carbon fiber layer, more preferably at least 80%, and may be 100%.

[0134] The depth of the conductive material 2 from the surface of the carbon fiber layer can be determined using a scanning electron microscope and a dispersed-type fluorescent X-ray analyzer. Specifically, an image is obtained using a scanning electron microscope, the measurement location is detected, the sample is irradiated with electron beams, and the fluorescent X-rays emitted by the sample are analyzed using an X-ray analyzer. The depth-wise distribution of the fluorescent X-ray detection ratio of the element / C or binder resin / C of the conductive material 2 near the interface between the carbon fiber layer and the porous layer in the gas diffusion layer can be measured. Here, "C" refers to carbon.

[0135] For example, the count ratio at various locations near the interface between the carbon fiber layer and the porous layer is measured using an electron microscope at a magnification of 100 to 500 times. For example, if the thickness of the carbon fiber layer is 315 μm, and the conductive material is confirmed to be present from the interface to a position approximately 20 μm toward the carbon fiber layer, it can be said that the conductive material is present from the surface of the carbon fiber layer to a position that is at least 90% of the thickness of the carbon fiber layer in the depth direction.

[0136] For example, when Ag as the conductive material 2 is applied to the carbon fiber layer by vapor deposition / sputtering, the depth-direction distribution of the detection number ratio of Ag / C fluorescent X-rays near the interface between the carbon fiber layer and the porous layer is measured.

[0137] In addition, for example, when a ionomer having a sulfonic group (S) is used as a binder resin and a mixed solution containing a conductive substance 2 and a binder resin is sprayed on the carbon fiber layer by a spray method, the depth direction distribution of the detection number ratio of S / C of fluorescent X-rays near the interface between the carbon fiber layer and the porous layer is measured.

[0138] For example, by plotting the count ratios of Ag / C to S / C on the vertical axis and the position of the detection target (Ag or S) on the horizontal axis, the position of the conductive material 2 present in the carbon fiber layer can be confirmed. A larger count ratio indicates a greater presence of the conductive material 2 at each position in the carbon fiber layer.

[0139] Since part of the carbon fibers are covered with the conductive substance 2 , the conductive substance 2 is present throughout the interior in the depth direction, thereby increasing the conductivity of the gas diffusion layer in the depth direction.

[0140] It is sufficient for the carbon fibers to have at least a portion of their surface covered with the conductive substance 2, and the entire surface may be covered with the conductive substance 2. The extent to which the carbon fibers are covered with the conductive substance 2 can be confirmed using an electron microscope.

[0141] <Cathode>

[0142] The cathode (cathode) described in this embodiment is manufactured by the manufacturing method of the gas diffusion layer described in this embodiment, and has a gas diffusion layer, the gas diffusion layer having a carbon fiber layer and a porous layer, the carbon fiber layer containing a conductive substance 2 and carbon fiber, and a portion of the carbon fiber is covered with the conductive substance 2, the porous layer containing a conductive substance 1 and a bonding resin, and the cathode has a catalyst layer on the side of the aforementioned porous layer.

[0143] More specifically, the cathode (cathode) described in this embodiment has a gas diffusion layer, the gas diffusion layer has a carbon fiber layer and a porous layer, the carbon fiber layer contains a conductive substance 2 and carbon fibers, a portion of the aforementioned carbon fibers is covered with the aforementioned conductive substance 2, and the aforementioned conductive substance 2 exists from the surface to a position of more than 60% in the depth direction, the porous layer contains a conductive substance 1 and a binding resin, the porosity is 10 to 60%, the average pore size is 10 to 500 nm, and the cathode has a catalyst layer on the side of the aforementioned porous layer.

[0144] The method for confirming the degree of coverage of the carbon fibers by the conductive substance 2 and the position of the conductive substance 2 in the carbon fiber layer is as described above.

[0145] In the method for manufacturing a gas diffusion layer according to this embodiment, when the carbon fiber layer is manufactured by a spraying method, the carbon fiber layer further contains a binder resin. From the perspective of balancing the conductivity, hydrophobicity, and gas diffusivity of the carbon fiber layer, the loading amount of the conductive material 2 and the binder resin in the carbon fiber layer is preferably 0.05 to 2 mg / cm 2 From the same viewpoint, the amount of the conductive material 2 and the binder resin supported in the carbon fiber layer when produced by the spraying method is more preferably 0.10 to 1.50 mg / cm 2 , more preferably 0.15 to 1.00 mg / cm 2 .

[0146] In the method for manufacturing a gas diffusion layer according to this embodiment, when the carbon fiber layer is manufactured by vapor deposition / sputtering, the amount of the conductive material 2 carried by the carbon fiber layer is preferably 0.5 to 5 μg / cm2 from the viewpoint of balancing the conductivity, hydrophobicity, and gas diffusivity of the carbon fiber layer. 2 From the same viewpoint, the amount of the conductive material 2 carried by the carbon fiber layer when produced by the vapor deposition / sputtering method is more preferably 0.7 to 4 μg / cm 2 , more preferably 1 to 3 μg / cm 2 .

[0147] As described above, the gas diffusion layer produced by the method for producing a gas diffusion layer according to this embodiment can be used not only in carbon dioxide reduction electrolysis devices but also in water electrolysis devices, fuel cells, gas diffusion electrodes for air batteries, and the like. Similarly, the catalyst layer is not limited to carbon dioxide reduction applications and can be used in various batteries, electrodes, and the like.

[0148] When a catalyst layer for carbon dioxide reduction is used as a catalyst layer, the cathode described in this embodiment has a gas diffusion layer manufactured by the method for manufacturing a gas diffusion layer described in this embodiment. Therefore, the CO2 supplied to the catalyst layer will not decrease, and the electrolysis activity is excellent.

[0149] The details of the gas diffusion layer are as described in the description of the method for producing the gas diffusion layer.

[0150] Catalyst layer

[0151] The catalyst layer according to this embodiment contains at least a catalyst and may further contain an ionomer.

[0152] The catalyst layer described in this embodiment is located on the porous layer side of the gas diffusion layer. In other words, in the stacked structure of carbon fiber layer / porous layer / catalyst layer, it is located on the side of the porous layer surface opposite to the carbon fiber layer side.

[0153] (catalyst)

[0154] The catalyst according to this embodiment is preferably formed of a carrier containing carbon and supporting inorganic fine particles or a metal complex.

[0155] In the catalyst of the present application technology, the component showing catalytic effect is the inorganic particles or metal complex supported on the carrier, but in the present application technology, the inorganic particles and metal complex are called "catalyst sources" and the carrier supporting the catalyst source is called "catalyst".

[0156] [Inorganic fine particles, metal complexes]

[0157] In the carrier according to this embodiment, inorganic fine particles or metal complexes are supported as a catalyst source.

[0158] Inorganic fine particles and metal complexes are not particularly limited as long as they exhibit catalytic activity. In the present technology, inorganic fine particles refer to metals and inorganic compounds having an average particle size of 1 to 100 nm as measured by photographic observation using a scanning electron microscope or the like.

[0159] For example, when the catalyst source is used for a catalyst layer for a fuel cell, platinum, gold, nickel, ruthenium, rhodium, etc. can be used as inorganic fine particles. In addition, nickel complexes, cobalt complexes, iron complexes, manganese complexes, zinc complexes, etc. can be used as metal complexes.

[0160] In addition, for example, when the catalyst source is used for a catalyst layer for a secondary battery electrode, platinum, gold, nickel, iridium, metal oxides, etc. can be used as inorganic fine particles, and nickel complexes, cobalt complexes, iron complexes, manganese complexes, zinc complexes, etc. can be used as metal complexes.

[0161] When the catalyst layer is used as a catalyst layer for reducing carbon dioxide, it is preferable to use a catalyst source having the function of generating at least carbon monoxide by a reduction reaction as the inorganic fine particles and the metal complex.

[0162] Specifically, the inorganic fine particles for reducing carbon dioxide are preferably selected from the group consisting of gold, silver, copper, nickel, iron, cobalt, zinc, chromium, palladium, tin, manganese, aluminum, indium, bismuth, molybdenum, and carbon nitride.

[0163] Among the above, 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 even more preferably silver, gold, and copper.

[0164] From the viewpoint of the reaction speed of the carbon dioxide reduction reaction, the average particle diameter of the inorganic particles as the carbon dioxide reduction catalyst source is preferably below 65nm, preferably below 60nm, preferably below 50nm, preferably below 40nm, and preferably below 30nm. In addition, the lower limit of the average particle diameter is not limited, and from the aspect of ease of manufacture, is preferably above 1nm, more preferably above 5nm.

[0165] The average particle size can be measured by, for example, photographic observation using a scanning electron microscope or the like.

[0166] The metal complex serving as a catalyst source for reducing carbon dioxide 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 copper, nickel, iron, cobalt, zinc, manganese, molybdenum and aluminum.

[0167] Among the above, 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 even more preferably nickel, cobalt and iron. The metal complex may contain only one metal or ion of the metal, or may contain two or more.

[0168] 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. Preferred are phthalocyanine complexes, porphyrin complexes, pyridine complexes, and metal-supported covalently bonded triazine structures; more preferred are phthalocyanine complexes, porphyrin complexes, and metal-supported covalently bonded triazine structures; and even more preferred are porphyrin complexes and metal-supported covalently bonded triazine structures. The metal complex may contain only one ligand or two or more.

[0169] The inorganic fine particles and the metal complex can be supported on the carrier described in this embodiment by performing known methods such as vapor deposition, precipitation, adsorption, deposition, bonding, welding, physical mixing, and spraying.

[0170] In addition, the catalyst in the present technology is preferably covered with an ionomer. By covering the catalyst with an ionomer, ion conductive channels are easily formed between the covered catalyst and the solid electrolyte described later, ions generated by the reaction are easily transferred, and electrolysis efficiency can be improved.

[0171] [Ionomer]

[0172] The catalyst layer may further comprise an ionomer.

[0173] The ionomer functions as a binder resin in the catalyst layer. It is a matrix resin (continuous phase) that can disperse and fix the additives and catalysts described in this embodiment. It also has the function of conducting ions generated by electrolysis and improving the CO2 electrolysis efficiency.

[0174] The ionomer may be the binder material described as a component of the mixed solution used when the conductive material is applied to the carbon fiber layer by spraying, and is preferably an anion exchange resin.

[0175] When the cathode (cathode) according to this embodiment is used in the ion exchange membrane-electrode assembly and solid electrolyte electrolysis device described below, the ionomer is preferably made of the same resin as the solid electrolyte (ion exchange membrane) from the viewpoint of improving conductivity.

[0176] [Carrier]

[0177] The support according to this embodiment is not particularly limited, but preferably contains carbon from the viewpoint of imparting conductivity.

[0178] Carbon generally has electrical conductivity, and therefore, a support containing carbon is a conductive support.

[0179] The carbon-containing carrier is not limited as long as it is a conductive material that can be used as a gas diffusion layer in an electrode provided in a device for reducing carbon dioxide. Examples thereof include carbon black (furnace black, acetylene black, Ketjen black, thermal black, etc.), activated carbon, graphite, carbon nanotubes, carbon nanofibers, carbon nanohorns, graphene nanosheets, nanoporous carbon, etc. Among them, carbon black is preferred from the viewpoint of increasing the active site density.

[0180] The primary particle size of carbon black is preferably 5 to 200 nm, more preferably 10 to 100 nm, and even more preferably 10 to 50 nm, from the perspective of increasing active site density and current density. The primary particle size of carbon black can be measured using a transmission electron microscope. The primary particle size can be determined by measuring the longest diameter of the particles observed under the microscope as the major diameter and calculating the average of the obtained major diameters.

[0181] From the same viewpoint, the secondary particle size (aggregate particle size) of carbon black is preferably small, and carbon black having a large amount of functional groups is preferred.

[0182] Carbon black may be a commercially available product, and examples thereof include Vulcan (registered trademark) XC-72 (manufactured by Cabot Corporation) and BLACKPEARL 2000 (manufactured by Cabot Corporation).

[0183] The carrier may be used alone or in combination of two or more.

[0184] From the viewpoint of further improving the production efficiency of synthesis gas containing CO, the content of the catalyst according to this embodiment in the catalyst layer is preferably 5 to 90 mass %, more preferably 10 to 80 mass %, and even more preferably 15 to 60 mass %.

[0185] <Ion Exchange Membrane-Electrode Assembly>

[0186] The ion exchange membrane-electrode assembly according to this embodiment includes the cathode according to the above-described embodiment, a solid electrolyte, and an anode.

[0187] The ion exchange membrane-electrode assembly according to this embodiment includes a cathode including a gas diffusion layer manufactured by the method for manufacturing a gas diffusion layer of the present application, and therefore has high electrolytic activity and a high CO 2 reduction reaction rate.

[0188] like Figure 1 As shown, the ion exchange membrane-electrode assembly according to this embodiment has a PEM-type structure in which a solid electrolyte 30 is sandwiched between a catalyst layer 20 and an anode 40. The catalyst layer 20 includes a plurality of catalysts 24 according to this embodiment and an ionomer 22. In addition, the catalyst layer 20 is combined with a gas diffusion layer 10 on the surface opposite to the surface in contact with the solid electrolyte 30, thereby forming a cathode (cathode) according to this embodiment.

[0189] like Figure 1 As shown, carbon dioxide (CO 2 ) is supplied from the surface 10 b side of the gas diffusion layer 10 to the catalyst layer 20 , and carbon monoxide (CO) is generated by a reduction reaction.

[0190] Below, in Figure 1 Symbols are omitted for explanation.

[0191] Solid electrolyte

[0192] The ion exchange membrane-electrode assembly according to this embodiment includes a solid electrolyte.

[0193] A polymer membrane can be used as the solid electrolyte. The polymer can be various ionomers, which can be cation exchange resins or anion exchange resins, preferably anion exchange resins. That is, the solid electrolyte is preferably an anion exchange membrane. Furthermore, it is more preferable to use the same anion exchange resin as the ionomer used in the catalyst layer.

[0194] As the solid electrolyte, a commercially available cation exchange membrane or anion exchange membrane can be used.

[0195] When an anion exchange membrane is used as the solid electrolyte, the base point density in a dry state is preferably 0.5 to 5.0 mmol / cm3 , more preferably 2.5 mmol / cm 3 Above and less than 4.5mmol / cm 3 , more preferably 2.9mmol / cm 3 Above and less than 4.5mmol / cm 3 .

[0196] As the cation exchange membrane, for example, a strongly acidic cation exchange membrane obtained by introducing a sulfonic group into a fluororesin matrix, Nafion 117, Nafion 115, Nafion 212, Nafion 350 (produced by Chemours); a strongly acidic cation exchange membrane obtained by introducing a sulfonic group into a styrene-divinylbenzene copolymer matrix, NEOCEPTA CSE (produced by ASTOM), etc. can be used.

[0197] Examples of the anion exchange membrane include anion exchange membranes having one or more ion exchange groups selected from quaternary ammonium groups, primary amino groups, secondary amino groups, and tertiary amino groups. Specific examples include NEOCEPTA (registered trademark) ASE, AHA, ACS, and AFX (manufactured by ASTOM Co., Ltd.), and SELEMION (registered trademark) AMVN, DSVN, AAV, ASVN, and AHO (manufactured by Asahi Glass Co., Ltd.).

[0198] Regarding the reduction reaction of carbon dioxide, the reduction reaction in the cathode (cathode) described in this embodiment varies depending on the type of solid electrolyte. When a cation exchange membrane is used as the solid electrolyte, the reduction reaction of the following reaction formula (1) and reaction formula (2) occurs. When an anion exchange membrane is used as the solid electrolyte, the reduction reaction of the following reaction formula (3) and reaction formula (4) occurs.

[0199] CO2+2H + +2e - →CO+H2O (1)2H + +2e - →H2 (2)

[0200] H2O+CO2+2e - →CO+2OH - (3)2H2O+2e - →H2+2OH - (4)

[0201] 〔anode〕

[0202] The oxidation reaction in the anode varies depending on the type of solid electrolyte. When a cation exchange membrane is used as the solid electrolyte, the oxidation reaction of the following reaction formula (5) occurs, and when an anion exchange membrane is used as the solid electrolyte, the oxidation reaction of the following reaction formula (6) occurs.

[0203] 2H2O→O2+4H + +4e - (5)

[0204] 4OH - →O2+2H2O+4e - (6)

[0205] The anode is a gas diffusion electrode including a gas diffusion layer.

[0206] The gas diffusion layer includes, for example, a metal mesh. Examples of the anode electrode material include Ir, IrO2, Ru, RuO2, Co, CoOx, Cu, CuOx, Fe, FeOx, FeOOH, FeMn, Ni, NiOx, NiOOH, NiCo, NiCe, NiC, NiFe, NiCeCoCe, NiLa, NiMoFe, NiSn, NiZn, SUS, Au, and Pt.

[0207] <Solid electrolyte electrolysis device>

[0208] The solid electrolyte electrolysis device according to this embodiment includes: the cathode according to the above embodiment; an anode forming a pair of electrodes with the cathode; a solid electrolyte sandwiched between the cathode and the anode in a contact state; and a voltage application unit for applying voltage between the cathode and the anode.

[0209] The solid electrolyte electrolysis device according to this embodiment includes a cathode (cathode) including a gas diffusion layer manufactured by the method for manufacturing a gas diffusion layer of the present application, and therefore has high electrolysis activity and a high CO 2 reduction reaction rate.

[0210] Figure 4 This is a schematic diagram of a solid electrolyte electrolysis device that can be preferably used in this embodiment.

[0211] Figure 4 The following solid electrolyte electrolysis device 800 is shown, which has: the cathode (cathode) 200 described in this embodiment, the anode (anode) 400 forming a pair of electrodes with the cathode 200, the solid electrolyte 300 clamped between the cathode 200 and the anode 400 in a contact state, and the voltage application part 700 for applying voltage between the cathode 200 and the anode 400.

[0212] Figure 4The solid electrolyte electrolysis device 800 shown further includes a cathode current collecting plate 100 , an anode current collecting plate 500 , and an electrolyte 600 .

[0213] The cathode described in the above embodiment is used as the cathode 200. In addition, the solid electrolyte 300 and Figure 1 The solid electrolyte 30 is the same as that in the embodiment of the present invention, and the solid electrolyte 300 is preferably an anion exchange membrane. Figure 1 The anode 40 in is the same.

[0214] The details of the cathode 200 , the solid electrolyte 300 , and the anode 400 are as described above.

[0215] Hereinafter, each element other than the cathode 200 , the solid electrolyte 300 , and the anode 400 will be described with reference numerals omitted.

[0216] 〔Cathode collector plate〕

[0217] Examples of the cathode current collector plate (cathode current collector plate) include metal materials such as copper (Cu), nickel (Ni), stainless steel (SUS), nickel-plated steel, and brass. Among them, copper is preferred from the perspectives of ease of processing and cost. Regarding the shape of the cathode current collector plate, when the material is a metal material, examples include metal foil, metal plate, metal film, expanded metal, punched metal, and foamed metal.

[0218] The cathode collector plate may be provided with a gas supply hole for supplying a raw gas containing carbon dioxide to the cathode and a gas recovery hole for recovering a generated gas containing carbon monoxide. By having a gas supply hole and a gas recovery hole, the raw gas can be fed to the cathode evenly and efficiently, and the generated gas (including unreacted raw gas) can be discharged. The gas supply hole and the gas recovery hole may be independently provided with only one or more than two. In addition, the shape, position, size, etc. of the gas supply hole and the gas recovery hole are not limited and can be set appropriately. Moreover, when the cathode collector plate is air permeable, the gas supply hole and the gas recovery hole may not be required.

[0219] It should be noted that when the cathode has the function of conducting electrons, a cathode collector plate is not necessarily required.

[0220] 〔Anode collector plate〕

[0221] In order to receive electrons from the anode, the anode collector plate (anode collector plate) preferably has conductivity while also having the rigidity to support the anode. From this viewpoint, the anode collector plate can suitably use metal materials such as titanium (Ti), copper (Cu), nickel (Ni), stainless steel (SUS), nickel-plated steel, brass, etc.

[0222] The anode current collector plate may be provided with a gas flow path for supplying a raw material gas (such as HO) to the anode. Providing the anode current collector plate with a gas flow path allows for uniform and efficient supply of the raw material gas to the anode. It should be noted that the number, shape, location, and size of the gas flow paths are not limited and may be set as appropriate.

[0223] [Voltage application section]

[0224] The voltage application unit applies voltage between the cathode and anode by applying voltage to the cathode and anode collector plates. Since the two collector plates are conductive, they supply electrons to the cathode and receive electrons from the anode. Furthermore, to apply an appropriate voltage, the voltage application unit may be electrically connected to a control unit (not shown).

[0225] Electrolyte

[0226] The electrolyte solution is preferably an aqueous solution with a pH of 5 or higher.

[0227] Examples thereof include carbonate aqueous solutions, bicarbonate aqueous solutions (eg, KHCO 3 aqueous solutions), sulfate aqueous solutions, borate aqueous solutions, sodium hydroxide, potassium hydroxide aqueous solutions, and sodium chloride aqueous solutions.

[0228] (Reaction gas supply unit)

[0229] The solid electrolyte electrolysis device described in this embodiment may include a reaction gas supply unit (not shown) outside the solid electrolyte electrolysis device. Specifically, CO2 can be supplied as a reaction gas to the catalyst layer provided on the cathode. The reaction gas can be supplied from the reaction gas supply unit to the gas supply holes via piping (not shown), or the reaction gas can be blown onto the surface of the cathode current collector plate opposite to the surface in contact with the cathode. For environmental reasons, factory exhaust gas is preferably used as the reaction gas.

[0230] [CO generation method]

[0231] Next, a CO generation method using the solid electrolyte electrolysis device according to this embodiment will be described.

[0232] First, a reaction gas supply unit (not shown) supplies CO 2 , a raw material reaction gas, in a gaseous state to the solid electrolyte electrolysis device. At this time, CO 2 is supplied to the cathode through, for example, a gas supply hole provided in the cathode current collector plate.

[0233] Next, the CO2 supplied to the cathode contacts the catalyst layer of the cathode, whereby when a cation exchange membrane is used as a solid electrolyte, the reduction reactions of the above-mentioned reaction formulas (1) and (2) occur, and when an anion exchange membrane is used as a solid electrolyte, the reduction reactions of the above-mentioned reaction formulas (3) and (4) occur, thereby generating a synthetic gas containing at least CO and H2.

[0234] Next, the generated synthesis gas containing CO and H 2 is sent to a gas recovery device (not shown) through a gas recovery hole provided in the cathode current collector plate, for example, and is recovered as a predetermined gas.

[0235] Example

[0236] Next, the technology of the present application will be specifically described using examples, but the technology of the present application is not limited to these examples at all.

[0237] <Manufacturing of Gas Diffusion Layer>

[0238] [Example 1]

[0239] The gas diffusion layer of Example 1 was produced using a sputtering method. Specifically, the method is as follows.

[0240] A magnetron sputtering apparatus was used to sputter the carbon fiber layer 1 having the porous layer on the opposite side of the surface thereof. The sputtering current was 20 mA and the loading amount was 2 μg / cm 2 Pure Ag (99.99 mass %) was imparted in a manner to obtain the gas diffusion of Example 1.

[0241] A magnetron sputtering apparatus, trade name "JFC-1600" manufactured by JEOL Ltd., was used, and sputtering was performed in a state where the interior was replaced with dilute Ar.

[0242] The carbon fiber layer 1 having a porous layer is Sigracet (registered trademark) 39BB, manufactured by SGL Carbon. The thickness of the carbon fiber layer portion of the carbon fiber layer 1 is 315 μm, the porosity of the porous layer is 15-30%, and the average pore diameter is 100-300 nm (catalog value).

[0243] [Comparative Example 1]

[0244] The gas diffusion layer of Comparative Example 1 was produced using a sputtering method. Specifically, the method is as follows.

[0245] A magnetron sputtering apparatus (JFC-1600, manufactured by JEOL Ltd.) was used to sputter the carbon fiber layer 2 without a porous layer at a sputtering current of 20 mA and a loading of 2 μg / cm 3 in a state where the interior was substituted with a thin layer of Ar.2 Pure Ag (99.99 mass %) was imparted in a manner to obtain the gas diffusion of Reference Example 1.

[0246] As the carbon fiber layer 2 not including a porous layer, "TGP-H-060" manufactured by Toray Industries, Inc. was used.

[0247] [Example 2]

[0248] The gas diffusion layer of Example 2 was produced using a spraying method. Specifically, the method is as follows.

[0249] Carbon black (the conductive material 2 described in this embodiment) with a primary particle size of 30 nm is mixed with a binder resin 1 or a binder resin 2 in such a manner that the ratio (a / r) of the mass of the conductive material (a) to the mass of the binder resin (r) becomes 5 / 1, and is dispersed in ethanol to prepare a mixed solution 1.

[0250] While the carbon fiber layer 1 having the porous layer was heated to 75°C, the mixed solution 1 was mixed with pressurized air and atomized from a spray device onto the surface of the carbon fiber layer 1 opposite to the surface adjacent to the porous layer. The mixed solution 1 was sprayed onto the conductive material and the binder resin in an amount of 0.2 mg / cm 2 The process was stopped at the moment of , and the gas diffusion layer of Example 2 was obtained.

[0251] The binder resin 1 used was "Nafion (registered trademark) D521" manufactured by Chemours, Inc. The spray device used was an external mixing two-fluid nozzle (manufactured by APIROS, trade name "LPVN (registered trademark) 10").

[0252] [Example 3]

[0253] In the production of the gas diffusion layer of Example 2, the mixed solution 1 was sprayed onto the conductive material and the binder resin so that the loading amount was 0.6 mg / cm 2 The gas diffusion layer of Example 3 was manufactured in the same manner as above except that the reaction mixture was stopped at the time of .

[0254] [Example 4]

[0255] The gas diffusion layer of Example 4 was produced using a spraying method. Specifically, the method is as follows.

[0256] Carbon black (the conductive material 2 described in this embodiment) with a primary particle size of 30 nm is mixed with a binder resin 2 in such a manner that the ratio (a / r) of the mass of the conductive material (a) to the mass of the binder resin (r) becomes 5 / 1, and is dispersed in ethanol to produce a mixed solution 2.

[0257] While the carbon fiber layer 1 having the porous layer was heated to 75°C, the mixed solution 2 was mixed with pressurized air and atomized onto the surface of the carbon fiber layer 1 opposite to the surface having the porous layer. The mixed solution 2 was sprayed onto the conductive material and the binder resin in an amount of 0.4 mg / cm 2 The process was stopped at the moment of , and the gas diffusion layer of Example 4 was obtained.

[0258] The binder resin 2 used was "Teflon (registered trademark) PTFEDISP 30" manufactured by Chemours. An external mixing two-fluid nozzle (manufactured by APIROS, trade name "LPVN (registered trademark) 10") was used as the spray device.

[0259] [Comparative Example 2]

[0260] As the gas diffusion layer of Comparative Example 2, a carbon fiber layer 1 including a porous layer (manufactured by SGL Carbon Co., Ltd., trade name “Sigracet (registered trademark) 39BB”) was used.

[0261] [Comparative Example 3]

[0262] The gas diffusion layer of Comparative Example 3 was produced using a liquid phase method. Specifically, the method is as follows.

[0263] The carbon fiber layer 1 having a porous layer was immersed in the mixed solution 1 prepared in the production of the gas diffusion layer of Example 2, and the mixed solution 1 was adjusted to 0.8 mg / cm 2 A mixture of the conductive material and the binder resin was supported on the carbon fiber layer 1 to obtain a gas diffusion layer of Comparative Example 3.

[0264] <Measurement of the Amount of Side Reactions>

[0265] An anion exchange membrane with a thickness of about 30 μm, an iridium oxide-supported carbon anode (manufactured by Dioxide Materials) as an anode, and the gas diffusion layer of Example 1 or Comparative Example 1 as a cathode (cathode) were laminated to form a membrane-electrode assembly.

[0266] It should be noted that as the substrate of the anion exchange membrane, a fluorine-based resin (basic point density of 2.1 mmol / cm 3 ). In addition, the anode is configured to be in contact with the electrolyte tank.

[0267] Using this device, pure CO2 was supplied to the cathode (cathode). Under the condition that the battery was heated to 80°C, the applied potential of the cathode was set to -2.6V relative to the anode, CO2 was electrolyzed, and the current density [mA / cm 2 ]. The results are summarized in Table 1.

[0268] [Table 1]

[0269] Table 1

[0270]

[0271] As shown in Table 1, when a conductive material is added to a carbon fiber layer having a porous layer (Example 1), the partial current density due to H2 generation as a side reaction significantly increases, and the amount of CO generated decreases, compared to the case without a porous layer (Comparative Example 1). This indicates that in Comparative Example 1, the conductive material surrounds the surface of the gas diffusion electrode, thus acting as active sites for the side reaction. However, by providing the carbon fiber layer with a porous layer, the formation of these active sites can be significantly suppressed.

[0272] <Measurement of Resistance of Gas Diffusion Electrode>

[0273] Two gold electrodes were used to clamp the gas diffusion layers (geometric area of ​​2.25 cm) of Examples 1 to 4 and Comparative Examples 2 to 3. 2 ), applying 100mA / cm 2 The voltage drop between the gold electrodes was measured using the four-terminal method under conditions of a DC current of 1.5 volts. The vertical resistance of the electrodes was then measured. The results are summarized in Table 2.

[0274] [Table 2]

[0275] Table 2

[0276]

[0277] As shown in Table 2, when Ag was added to the carbon fiber layer having a porous layer by a vapor phase method (Example 1) and when carbon black was added (Examples 2, 3, and 4), the resistance was significantly reduced compared to the case where no Ag was added (Comparative Example 2).

[0278] When carbon black is applied to a porous carbon fiber layer by a liquid phase method (Comparative Example 3), the electrical resistance is reduced, but conductive material adheres to the surface of the porous layer. Therefore, when the porous layer is adjacent to the catalyst layer, it may have the adverse effect of acting as an active site for unintended reactions (side reactions).

[0279] Furthermore, it was found that by supplying fine particles of the conductive material using the spraying method and the sputtering method, the conductive material could uniformly reach the interior of the gas diffusion layer. Therefore, the gas diffusion layers produced in Examples 1 to 4 had excellent conductivity in the depth direction.

[0280] <Evaluation of Hydrophobicity of Gas Diffusion Layer>

[0281] The cross-sectional electron microscope images of the carbon fibers of the gas diffusion layers of Example 1, Example 2, and Comparative Example 2 are shown in FIG. Figure 5 、 6 and 7. It should be noted that Figure 5 (Example 1) is a reflected electron image, Figure 6 (Example 2) and Figure 7 (Comparative Example 2) is a secondary electron image.

[0282] Depend on Figures 5-7 It can be seen that: Example 1 ( Figure 5 ) and Example 2 ( Figure 6 )'s gas diffusion layer does not bury the pores inside the gas diffusion layer, and a portion of the carbon fiber surface is covered with a conductive material, maintaining porosity and hydrophobicity due to the carbon fiber.

[0283] It should be noted that in Figure 5 Below the photo is recorded:

[0284] 1μm Test 2022 / 09 / 08

[0285] X 1000015.0kV COMPOSEM WD7.8mm 10:30:12

[0286] The length of the white line corresponds to 1 μm.

[0287] exist Figure 6 Below the photo is recorded:

[0288] 1μm Test 20

[0289] X 100005.0kV SEI SEM WD7.2mm

[0290] The length of the white line corresponds to 1 μm.

[0291] exist Figure 7 Below the photo is recorded:

[0292] 1μm Test 2022 / 09 / 08

[0293] X 100005.0kV SEI SEM WD8.0mm 10:09:57

[0294] The length of the white line corresponds to 1 μm.

[0295] <Evaluation of the Position of the Conductive Material in the Carbon Fiber Layer>

[0296] Under the following measurement conditions, for the gas diffusion layer of Example 1, the depth-direction distribution of the detection ratio of the fluorescent X-rays of Ag / C near the interface between the carbon fiber layer and the porous layer was measured; for the gas diffusion layer of Example 2, the depth-direction distribution of the detection ratio of the fluorescent X-rays of S / C near the interface between the carbon fiber layer and the porous layer was measured.

[0297] (Measurement conditions)

[0298] Scanning electron microscope: Field emission scanning electron microscope (Model: JSM-7001F, manufactured by JEOL Ltd.)

[0299] Energy dispersive X-ray fluorescence analyzer: UltraDry (manufactured by Thermo Fisher Scientific)

[0300] Accelerating voltage: 15 kV

[0301] In the measurement of the gas diffusion layer of Example 1, the position of the conductive material present in the carbon fiber layer was confirmed by plotting the count ratio of Ag / C on the vertical axis and the position of the detection object (Ag) on ​​the horizontal axis. Figure 8 The electron microscope was used at a magnification of 500 times, and the count ratio at each position near the interface between the carbon fiber layer and the porous layer was measured.

[0302] exist Figure 8 In the "Ag(L) / C(K) count ratio" on the vertical axis, "Ag(L)" refers to the L line of Ag, and "C(K)" refers to the K line of carbon. The "Position (μm)" on the horizontal axis indicates the depth distance from the interface between the carbon fiber layer and the porous layer (with the porous layer side as positive), with the interface between the carbon fiber layer and the porous layer being 0 μm.

[0303] In the measurement of the gas diffusion layer of Example 2, the position of the conductive material present in the carbon fiber layer was confirmed by plotting the S / C count ratio as the vertical axis and the position of the detection object (S) as the horizontal axis. Figure 9 The magnification of the electron microscope was set to 300 times, and the count ratio at each position near the interface between the carbon fiber layer and the porous layer was measured.

[0304] exist Figure 9In the "S(K) / C(K) count ratio" on the vertical axis, "S(K)" refers to the sulfur K line, and "C(K)" refers to the carbon K line. The "position (μm)" on the horizontal axis indicates the depth distance from the interface between the carbon fiber layer and the porous layer (with the porous layer side as positive), with the interface between the carbon fiber layer and the porous layer being 0 μm.

[0305] Figure 8 is the depth-direction distribution of the detection number ratio of Ag / C fluorescent X-rays near the interface between the carbon fiber layer and the porous layer in the gas diffusion layer of Example 1, Figure 9 Graph 1 shows the depth-direction distribution of the S / C fluorescent X-ray detection ratio near the interface between the carbon fiber layer and the porous layer in the gas diffusion layer of Example 2.

[0306] A larger count ratio means that more detection targets exist at each position in the carbon fiber layer.

[0307] In the measurement of the gas diffusion layer of Example 1, Ag, which is a conductive material, was used as the detection object. Figure 8 The larger the count ratio in , the more Ag exists at each position in the carbon fiber layer.

[0308] In the measurement of the gas diffusion layer of Example 2, the sulfonic groups contained in the binder resin 1 (manufactured by Chemours, trade name "Nafion (registered trademark) D521") used as the binder resin were detected. Figure 9 A larger count ratio indicates that more sulfonyl groups are present at various locations in the carbon fiber layer. The gas diffusion layer of Example 2 was produced by spraying a mixed solution 1 containing a conductive substance and a binder resin onto the surface of the carbon fiber layer 1. Therefore, it is believed that the conductive substance, along with the binder resin, also penetrates from the surface of the carbon fiber layer into the interior in the depth direction, and that the conductive substance is also present at locations where sulfonyl groups are detected.

[0309] Depend on Figure 8 As can be seen, it can be confirmed that in the gas diffusion layer of Example 1, a large amount of conductive material exists from the interface between the carbon fiber layer and the porous layer to a position of about 20 μm toward the carbon fiber layer side (a position that is more than 90% of the thickness of the carbon fiber layer from the surface in the depth direction).

[0310] In addition, by Figure 9 As can be seen, in the gas diffusion layer of Example 2, a large number of sulfonic acid groups were confirmed to be present from the interface between the carbon fiber layer and the porous layer to a position approximately 10 μm toward the carbon fiber layer (a position representing at least 90% of the thickness of the carbon fiber layer in the depth direction from the surface). Therefore, it can be said that a large amount of conductive material was present from the surface to a position approximately 100% in the depth direction.

[0311] From the above, it was confirmed that the conductive substance exists up to the vicinity of the interface between the carbon fiber layer and the porous layer, although there is a local concentration deviation.

[0312] <Production of Catalyst>

[0313] 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 support having a primary particle size of 30 nm (the support according to this embodiment) in 15 mL of ethanol to prepare an ethanol dispersion.

[0314] The obtained ethanol dispersion was irradiated with ultrasound for 10 minutes, and then heated and dried to evaporate the ethanol, thereby obtaining a mixture. The obtained mixture was calcined in an inert gas atmosphere at 900°C for more than 10 seconds using a calcining furnace. Thereafter, the product was washed with an aqueous sulfuric acid solution, and the solid was recovered using a suction filter. The solid was vacuum-dried at 60°C overnight to obtain a catalyst powder (intermediate) loaded with a Ni complex.

[0315] 0.3 g of the resulting catalyst powder was then placed in a jar along with 10 g of 0.5 mm diameter zirconia balls and 10 mL of water. The mixture was milled at 800 rpm for 20 minutes using a planetary ball mill to recover the catalyst slurry. The catalyst slurry was then washed again with aqueous sulfuric acid, and the solids were recovered using a suction filter. The recovered solids were vacuum-dried at 60°C overnight to obtain the final catalyst powder.

[0316] In addition, the primary particle size of carbon black is determined by laser diffraction particle size distribution measurement.

[0317] <Manufacturing of Solid Electrolyte Electrolysis Device>

[0318] [Example 5]

[0319] 22 mg of the resulting catalyst powder was dispersed in ethanol, and 2 mg of "Nafion (registered trademark)" (cation exchange resin) manufactured by Chemours was mixed with the dispersion as an ionomer. After mixing, the dispersion was irradiated with ultrasonic waves for 10 minutes and then exposed to a vacuum chamber at a reduced pressure of 10 kPa (absolute pressure) for 10 minutes.

[0320] Then, the porous layer side surface of the gas diffusion layer of Example 2 was sprayed with a sprayer so that the loading amount at the time of drying was 1 to 2 mg / cm 2 The cathode has a coating film of the dispersion as a catalyst layer.

[0321] An ion exchange membrane A having a thickness of about 30 μm and a carbon anode supporting iridium oxide (manufactured by Dioxide Materials) were attached to the obtained cathode to prepare an ion exchange membrane-electrode assembly.

[0322] It should be noted that the ion exchange membrane A is an anion exchange membrane with a thickness of about 30 μm. The substrate is a fluorine-based resin (with a basic point density of 2.1 mmol / cm2) having an aromatic ring in the main chain and a quaternary ammonium group bonded to the main chain as a side chain. 3 ).

[0323] The anode (positive electrode) was configured to be in contact with an electrolyte (0.5 mol / L KHCO 3 aqueous solution) tank.

[0324] [Example 6]

[0325] The solid electrolyte electrolysis device of Example 6 was manufactured in the same manner as in Example 5 except that the gas diffusion layer of Example 4 was used instead of the gas diffusion layer of Example 2.

[0326] [Example 7]

[0327] The solid electrolyte electrolysis device of Example 7 was manufactured in the same manner as in the manufacture of the solid electrolyte electrolysis device of Example 5, except that the gas diffusion layer of Example 1 was used instead of the gas diffusion layer of Example 2.

[0328] [Example 8]

[0329] The solid electrolyte electrolysis device of Example 8 was manufactured in the same manner as in the manufacture of the solid electrolyte electrolysis device of Example 5, except that the ion exchange membrane B was used instead of the ion exchange membrane A.

[0330] The ion exchange membrane B is a product of Dioxide Materials, Inc., under the trade name "X37-50grade60," and has a structure having polystyrene as a main chain and imidazolium-based ion exchange groups as side chains.

[0331] [Comparative Example 4]

[0332] The solid electrolyte electrolysis device of Example 5 was manufactured in the same manner as that of Comparative Example 4, except that the gas diffusion layer of Comparative Example 2 was used instead of the gas diffusion layer of Example 2.

[0333] [Comparative Example 5]

[0334] The solid electrolyte electrolysis device of Comparative Example 4 was manufactured in the same manner as above except that the ion exchange membrane B was used instead of the ion exchange membrane A to manufacture the solid electrolyte electrolysis device of Comparative Example 5.

[0335] [Comparative Example 6]

[0336] The solid electrolyte electrolysis device of Comparative Example 6 was manufactured in the same manner as in Example 5 except that the gas diffusion layer of Comparative Example 3 was used instead of the gas diffusion layer of Example 2.

[0337] <Evaluation of Solid Electrolyte Electrolysis Device>

[0338] [Examples 5 to 8 and Comparative Examples 4 to 6]

[0339] (Current density)

[0340] Using each of the solid electrolyte electrolysis devices of Examples 5 to 8 and Comparative Examples 4 to 6, pure CO 2 was supplied to the cathode at a flow rate of 100 sccm.

[0341] In the solid electrolyte electrolysis apparatuses of Examples 5 to 7, Comparative Examples 4, and Comparative Example 6 using ion exchange membrane A, CO2 was electrolyzed under the condition that the cell was heated to 80°C. In the solid electrolyte electrolysis apparatuses of Example 8 and Comparative Example 5 using ion exchange membrane B, CO2 was electrolyzed under the condition that the cell was heated to 70°C with the cathode potential set to -2.6 V relative to the anode. The CO generation current density [mA / cm 2 ] and CO selectivity [%], and the results are summarized in Table 3.

[0342] [Table 3]

[0343]

[0344] As can be seen from Table 3, the resistance decreased, and as a result, an effect of improving the current density when a constant voltage was applied was confirmed. When both ion exchange membranes A and B were used, the same improvement effect was confirmed.

[0345] Industrial applicability

[0346] According to this embodiment, a solid electrolyte electrolysis device can generate a synthesis gas containing at least CO and H2 in a desired production ratio by using CO2 gas, such as that discharged from factories, as a raw material and utilizing renewable energy such as a solar cell facing a voltage application unit. The synthesis gas thus generated can be used to generate fuel base materials, chemical raw materials, and the like through methods such as Fischer-Tropsch synthesis (FT synthesis) and methanation.

[0347] Description of Reference Numerals

[0348] 10 Gas Diffusion Layer

[0349] 20 catalyst layers

[0350] 22 ionomer

[0351] 24 catalysts

[0352] 30 Solid electrolyte (ion exchange membrane)

[0353] 40 anode (anode)

[0354] 50 ion exchange membrane-electrode assembly

[0355] 100 cathode collector plate

[0356] 200 cathode (cathode)

[0357] 300 solid electrolyte (ion exchange membrane)

[0358] 400 anode (anode)

[0359] 500 anode collector plate

[0360] 600 electrolyte

[0361] 700 voltage applying unit

[0362] 800 solid electrolyte electrolysis device

Claims

1. A method for manufacturing a gas diffusion layer, wherein: The gas diffusion layer includes a carbon fiber layer containing carbon fibers and a porous layer containing a conductive substance 1 and a binder resin. In the method for producing the gas diffusion layer, the conductive material 2 is applied from the surface side of the carbon fiber layer of the laminate comprising the carbon fiber layer and the porous layer by a spray method or a vapor phase method.

2. The method for manufacturing a gas diffusion layer according to claim 1, wherein: The porosity of the porous layer is 10-60%, and the average pore diameter is 10-500 nm.

3. The method for manufacturing a gas diffusion layer according to claim 1 or 2, wherein: The conductive material 1 and the conductive material 2 are each independently one or more selected from carbon materials and metals.

4. The method for producing a gas diffusion layer according to any one of claims 1 to 3, wherein: A mixed solution containing the conductive material 2 and a binder resin is sprayed from the surface side of the carbon fiber layer.

5. The method for manufacturing a gas diffusion layer according to claim 4, wherein: The mixed solution is such that the total amount of the conductive material 2 and the binder resin in the mixed solution is 0.05 to 2 mg / cm 2 way of spraying.

6. The method for producing a gas diffusion layer according to any one of claims 1 to 3, wherein: The conductive material 2 is applied from the surface side of the carbon fiber layer by vapor deposition or sputtering.

7. The method for manufacturing a gas diffusion layer according to claim 6, wherein: The amount of the conductive material 2 is 0.5 to 5 μg / cm 2 .

8. A cathode comprising a gas diffusion layer manufactured by the method for manufacturing a gas diffusion layer according to any one of claims 1 to 7, wherein the gas diffusion layer comprises a carbon fiber layer and a porous layer, wherein the carbon fiber layer comprises a conductive substance 2 and carbon fibers, a portion of the carbon fibers being covered with the conductive substance 2, and the porous layer comprises a conductive substance 1 and a binder resin, and The cathode has a catalyst layer on the porous layer side.

9. A cathode comprising a gas diffusion layer, the gas diffusion layer comprising a carbon fiber layer and a porous layer, the carbon fiber layer comprising a conductive substance 2 and carbon fibers, the carbon fibers being partially covered with the conductive substance 2, the conductive substance 2 being present at a depth of 60% or more from the surface, the porous layer comprising a conductive substance 1 and a binder resin, having a porosity of 10 to 60% and an average pore diameter of 10 to 500 nm, and The cathode has a catalyst layer on the porous layer side.

10. The cathode according to claim 8 or 9, wherein The carbon fiber layer further comprises a binder resin, and the loading amount of the conductive material 2 and the binder resin is 0.05 to 2 mg / cm 2 .

11. The cathode according to any one of claims 8 to 10, wherein The conductive material 1 and the conductive material 2 are each independently one or more selected from carbon materials and metals. 12 . An ion exchange membrane-electrode assembly comprising the cathode according to claim 8 , a solid electrolyte, and an anode.

13. The ion exchange membrane-electrode assembly according to claim 12, wherein: The solid electrolyte is an anion exchange membrane.

14. A solid electrolyte electrolysis device comprising: The cathode according to any one of claims 8 to 11; an anode forming a pair of electrodes with the cathode; a solid electrolyte sandwiched between the cathode and the anode in a contact state; and A voltage applying unit applies a voltage between the cathode and the anode.

15. The solid electrolyte electrolysis device according to claim 14, wherein: The solid electrolyte is an anion exchange membrane.

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