Hydrogen generation cathode

Abstract

To provide a cathode for hydrogen generation that can prevent a catalyst layer from being peeled from a conductive base material and an overvoltage from rising when the power supply is stopped.SOLUTION: A cathode for hydrogen generation comprises a conductive base material and a catalyst layer on the surface of the conductive base material. The catalyst layer includes at least platinum and an insulating oxide including crystalline zirconium. The conductive base material includes a metal including nickel. The value of [IZrO2 / INi]×100 is 0.1-40, when INi is the peak intensity of an x-ray diffracted by the (111) surface of the nickel, and IZrO2 is the peak intensity of an x-ray diffracted by the (012) surface of the insulating oxide including the crystalline zirconium.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cathode body for hydrogen generation. [Background technology]

[0002] In recent years, renewable energy technologies such as wind power generation and solar power generation have been attracting attention in order to solve problems such as global warming caused by greenhouse gases such as carbon dioxide and dwindling fossil fuel reserves.

[0003] Renewable energy output is highly variable because it depends on weather conditions. As a result, it is not always possible to transport the electricity generated by renewable energy to the general power grid, raising concerns about the potential for imbalances in power supply and demand and the instability of the power grid.

[0004] Therefore, research is being conducted into converting electricity generated from renewable energy into a form that can be stored and transported, and using this electricity.Specifically, research is being conducted into generating storable and transportable hydrogen through the electrolysis of water using electricity generated from renewable energy, and using this hydrogen as an energy source or raw material.

[0005] Hydrogen is widely used industrially in oil refining, chemical synthesis, metal refining, etc., and in recent years, the possibility of its use has expanded in hydrogen stations for fuel cell vehicles (FCVs), smart communities, hydrogen power plants, etc. For this reason, there are high expectations for the development of technology to obtain hydrogen, especially from renewable energy sources.

[0006] Methods for electrolyzing water include solid polymer water electrolysis, high-temperature steam electrolysis, and alkaline water electrolysis. However, alkaline water electrolysis is considered to be one of the most promising methods because it has been industrialized for several decades, can be carried out on a large scale, and is inexpensive compared to other water electrolysis devices.

[0007] However, in order to adapt alkaline water electrolysis as a means for storing and transporting energy in the future, it is necessary to enable water electrolysis by efficiently and stably utilizing electric power, which has large output fluctuations as described above, and there is a need to solve various issues with electrolytic cells and devices for alkaline water electrolysis.

[0008] It is well known that adopting a so-called zero-gap structure, in which the gap between the diaphragm and the electrode is substantially eliminated, as the structure of the electrolysis cell is particularly effective for solving the problem of reducing the electrolysis voltage in alkaline water electrolysis and improving the power consumption rate of hydrogen production (see Patent Documents 1 and 2). In the zero-gap structure, the generated gas is quickly released to the side of the electrode opposite the diaphragm through the pores in the electrode, thereby reducing the distance between the electrodes and minimizing the occurrence of gas accumulation near the electrodes, thereby reducing the electrolysis voltage. The zero-gap structure is extremely effective in reducing the electrolysis voltage and is adopted in a variety of electrolysis devices.

[0009] Furthermore, many techniques have been published for improving the durability of electrodes against repeated energization and deenergization (see Patent Documents 3 and 4). Patent Document 3 discloses a cathode having a catalyst layer containing at least platinum (Pt) on the surface of a conductive substrate containing nickel (Ni). In the cathode of the example, which is said to have high reverse current resistance, 2 A large amount of precious metals including platinum is used. Since the use of a large amount of precious metals including platinum is expensive and from the viewpoint of resource conservation, it is preferable that the platinum content is low. Patent Document 4 describes a method for producing a low hydrogen overvoltage cathode in which a catalytic layer containing platinum and zirconium oxide (ZrO2) is formed on a conductive metal substrate containing nickel. The method involves dissolving a nitric acid aqueous solution (wherein the total mole percentage of platinum and zirconium in the aqueous solution is 100%) containing platinum nitrite or nitrate and zirconium oxynitrate in an amount of 2 to 10 g / m2. 2 After drying, the coating is thermally decomposed at a temperature of 300 to 550°C. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent No. 5553605 [Patent Document 2] International Publication No. 2015 / 098058 [Patent Document 3] Japanese Patent Application Publication No. 2019-73806 [Patent Document 4] Patent No. 5317012 Summary of the Invention [Problem to be solved by the invention]

[0011] However, the conventional cathodes for alkaline water electrolysis described in Patent Documents 3 and 4 have a problem in that repeated application of a forward current that promotes the intended electrolysis reaction and a reverse current (reverse current) that occurs after the forward current is stopped causes nickel components to elute from the substrate surface, resulting in the detachment of the catalyst layer on the substrate surface and an increase in overvoltage. Therefore, it has been difficult to maintain high energy conversion efficiency over the long term when using a variable power source such as renewable energy.

[0012] Therefore, an object of the present invention is to provide a cathode for hydrogen generation in which the catalyst layer is prevented from peeling off from the conductive substrate and an increase in overvoltage occurs when current flow is stopped. [Means for solving the problem]

[0013] That is, the present invention is as follows. [1] a conductive substrate and a catalyst layer on a surface of the conductive substrate; the catalyst layer contains at least platinum and an insulating oxide containing crystalline zirconium; the catalyst layer includes a zirconium layer containing an insulating oxide containing crystalline zirconium, and a platinum layer containing platinum on a surface of the zirconium layer, or includes a mixed layer containing a mixture of platinum and the insulating oxide containing crystalline zirconium, the conductive substrate contains a metal including nickel, The conductive substrate is a mesh made by weaving metal wires having a wire diameter of 0.05 to 1.0 mm and a pitch of 20 to 60 meshes, and a specific surface area of ​​200 to 6000 m 2 / m 3 or a punched metal having a pore diameter of 2 to 8 mm, a pitch of 2 to 10 mm, an opening ratio of 20 to 80%, and a thickness of 0.5 to 2 mm, When the peak intensity of the X-ray diffracted by the (111) plane of the nickel is INi and the peak intensity of the X-ray diffracted by the (012) plane of the crystalline zirconium-containing insulating oxide is IZrO2, the value of [IZrO2 / INi] × 100 is 0.1 to 40%. A cathode for hydrogen generation, characterized by: [2 ] before The average thickness of the zirconium layer is 0.007 μm or more. ] The cathode for hydrogen generation described above. [ 3 The cathode for hydrogen generation according to [1] or [2], wherein the mixed layer has an average thickness of 0.05 μm or more. [ 4 ] The crystalline zirconium-containing insulating oxide includes a composite oxide of Zr and an X element (X is at least one selected from the group consisting of Ce, Y, Ca, and Mg), [1] to [ 3 10. The cathode for hydrogen generation according to claim 1, wherein the cathode is a cathode for hydrogen generation. [ 5 ] The weight of the platinum is 2 to 10 g / m 2 That is, [1]~[ 4 10. The cathode for hydrogen generation according to claim 1, wherein the cathode is a cathode for hydrogen generation. [ 6 ] Double layer capacitance is 0.001~0.2F / cm 2 That is, [1]~[ 5 10. The cathode for hydrogen generation according to claim 1, wherein the cathode is a cathode for hydrogen generation. [ 7 ] A method for producing a cathode for generating hydrogen, the cathode having a catalytic layer on a conductive substrate, the catalytic layer including: a zirconium layer containing an insulating oxide containing crystalline zirconium; and a platinum layer containing platinum on a surface of the zirconium layer, a coating solution containing at least zirconium is applied to the surface of a conductive substrate, and the coating solution is thermally decomposed at 100 to 700°C in an oxygen-containing atmosphere to form a zirconium layer containing an insulating oxide containing crystalline zirconium; a coating solution containing at least a platinum compound is applied to the surface of the zirconium layer, and the coating solution is thermally decomposed at 100 to 700°C in an oxygen-containing atmosphere to form a platinum layer containing platinum on the surface of the zirconium layer; The weight of the zirconium layer is 0.1 g / m 2 More than 20.0g / m 2 is A method for producing a cathode for hydrogen generation, comprising: [ 8 ] A method for producing a cathode for hydrogen generation having a catalytic layer on a conductive substrate, the catalytic layer including a mixed layer containing a mixture of platinum and an insulating oxide containing crystalline zirconium, A ZrO2 sol is applied to the surface of a conductive substrate and thermally decomposed at 100 to 700°C in an oxygen-containing atmosphere to form a zirconium layer containing an insulating oxide containing crystalline zirconium; a coating solution containing at least a platinum compound is applied to the surface of the zirconium layer, and the coating solution is thermally decomposed at 100 to 700°C in an oxygen-containing atmosphere to form a mixed layer containing a mixture of platinum and an insulating oxide containing crystalline zirconium, The weight of the crystalline zirconium-containing insulating oxide is 0.1 g / m 2 More than 18.0g / m 2 is A method for producing a cathode for hydrogen generation, comprising: [Effects of the Invention]

[0014] According to the present invention, dissolution of the conductive substrate surface due to reverse current when the current flow is stopped is suppressed, and peeling at the interface between the conductive substrate and the catalyst layer is suppressed, thereby providing a cathode for hydrogen generation with improved reverse current durability. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram showing an outline of an electrolysis device used in Examples, Reference Examples, and Comparative Examples. [Figure 2] FIG. 1 is a diagram showing an outline of a bipolar electrolytic cell used in an electrolysis test. [Figure 3A] FIG. 10 is a diagram showing the peak of an X-ray diffracted by the (111) plane of nickel (Ni peak) and the peak of an X-ray diffracted by the (012) plane of an insulating oxide containing crystalline zirconium (ZrO peak) in Example 4. [Figure 3B] FIG. 10 is a diagram showing the peaks (Ni peaks) of X-rays diffracted by the (111) plane of nickel in Comparative Example 5. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail. Note that the present invention is not limited to the following embodiment, and various modifications can be made within the scope of the gist of the present invention.

[0017] (Cathode for hydrogen generation) In hydrogen production by alkaline water electrolysis in a bipolar electrolyzer, reducing energy consumption, specifically the electrolysis voltage, is a major challenge. Because this electrolysis voltage is highly dependent on the cathode, the performance of the cathode is important.

[0018] The electrolysis voltage for alkaline water electrolysis is divided into the theoretically required voltage for water electrolysis, the overvoltage for the anodic reaction (oxygen generation), the overvoltage for the cathodic reaction (hydrogen generation), and the voltage due to the distance between the anode and cathode. Here, overvoltage refers to the voltage that must be applied in excess of the theoretical decomposition potential when a certain current is passed, and its value depends on the current value. In other words, when passing the same current, using electrodes with a lower overvoltage can reduce the power consumption to generate the same amount of hydrogen.

[0019] In order to achieve low overvoltage, the cathode must have high electrical conductivity, high hydrogen generation capacity, high wettability of the electrode surface with the electrolyte, etc. By including platinum in the cathode, it becomes possible to satisfy these requirements for a long period of time even when the electrolytic cell is operated under a fluctuating power supply.

[0020] However, as described above, in conventional cathodes for alkaline water electrolysis, repeated application of a forward current that promotes the intended electrolytic reaction and a reverse current (reverse current) that occurs after the forward current is stopped causes nickel components to elute from the substrate surface, resulting in the detachment of the platinum-containing catalyst layer on the substrate surface and an increase in overvoltage.

[0021] The cathode for hydrogen generation of this embodiment has a conductive substrate and a catalytic layer on the surface of the conductive substrate, the catalytic layer containing at least platinum and an insulating oxide containing crystalline zirconium, the conductive substrate containing a metal containing nickel, and is characterized in that, when the peak intensity of X-rays diffracted by the (111) plane of the nickel is INi and the peak intensity of X-rays diffracted by the (012) plane of the insulating oxide containing crystalline zirconium is IZrO2, the value of [IZrO2 / INi] × 100 is 0.1 to 40%. The hydrogen generation cathode of this embodiment has the above-mentioned characteristics, and thus can prevent nickel from eluting from the conductive base material, and can prevent the catalyst layer from falling off and overvoltage from increasing when a forward current that advances the intended electrolytic reaction is repeatedly applied and a reverse current (reverse current) that occurs after the forward current is stopped. Furthermore, the inclusion of an insulating oxide containing crystalline zirconium in the catalyst layer makes it possible to provide an electrode that is highly durable even with a small amount of precious metal.

[0022] In the cathode for hydrogen generation of this embodiment, the value of [IZrO2 / INi] × 100, which represents the crystallinity of the insulating oxide containing zirconium, is 0.1 to 40%, preferably 1 to 30%, and more preferably 2 to 20%, from the viewpoint of suppressing dissolution of Ni in the conductive base material. If the value of the crystallinity [IZrO2 / INi] x 100 exceeds 40%, the resistance of the cathode increases, making it difficult to obtain a desired overvoltage. Furthermore, when the crystallinity [IZrO2 / INi] x 100 is less than 0.1%, the zirconium is not crystallized, and the insulating oxide containing zirconium gradually dissolves over time during electrolysis or when immersed in the electrolyte. As a result, nickel dissolves from the substrate surface when the forward current that drives the intended electrolytic reaction is repeated, followed by the reverse current that occurs after the forward current is stopped, causing the catalyst layer on the substrate surface to fall off and increasing the overvoltage. In the cathode for hydrogen generation of this embodiment, the value of the crystallinity [IZrO2 / INi]×100 is 0.1 to 40%, and therefore the zirconium-containing insulating oxide is crystalline. The zirconium-containing insulating oxide may be zirconium oxide, or a composite oxide of Zr and an X element (X is at least one element selected from the group consisting of Ce, Y, Ca, and Mg). Zirconium oxide crystals include tetragonal, monoclinic, and cubic crystals, and any crystal may be used as long as it satisfies the above crystallinity. The peak intensity (INi) of X-rays diffracted by the (111) plane of nickel and the peak intensity (IZrO2) of X-rays diffracted by the (012) plane of the insulating oxide containing crystalline zirconium are values ​​measured using an X-ray diffraction device, and specifically, can be measured by the method described in the examples below.

[0023] The area of ​​the surface of the hydrogen generation cathode in this embodiment used for electrolysis can be determined in a pseudo manner by measuring the capacitance of the electric double layer formed at the interface between the cathode and the electrolyte (hereinafter also referred to as "double layer capacitance"). The double layer capacitance can be measured, for example, by electrochemical impedance spectroscopy. The double layer capacitance is calculated by analyzing a Cole-Cole plot, which is a plot of the real and imaginary parts obtained by AC impedance measurement, using equivalent circuit fitting. If the double layer capacity is small, the number of reaction active sites will be small, and a sufficiently low overvoltage may not be obtained. On the other hand, if the amount of catalyst attached is increased too much in order to increase the double layer capacity, the mechanical strength of the catalyst layer may decrease, and durability may decrease. Therefore, the double layer capacity of the cathode for hydrogen generation of this embodiment is set to 0.001 to 0.2 F / cm. 2 is preferably 0.01 to 0.15 F / cm 2 , and more preferably 0.03 to 0.08 F / cm 2 is.

[0024] [Catalyst layer] The catalyst layer constituting the cathode for hydrogen generation of this embodiment is formed on the surface of a conductive substrate, and contains at least platinum and an insulating oxide containing crystalline zirconium.

[0025] The weight of the catalyst layer is 2 to 40 g / m 2 It is preferable that the density is 4 to 20 g / m 2 More preferably, it is 6 to 10 g / m 2 When the weight per unit area of ​​the catalyst layer is within the above range, elution of nickel components from the surface of the conductive substrate can be suppressed. The average thickness of the catalyst layer is preferably 0.05 to 3.0 μm, more preferably 0.1 to 2.0 μm, and even more preferably 0.2 to 1.0 μm. When the average thickness of the catalyst layer is within the above range, the catalyst layer can be prevented from falling off from the substrate. The ranges of the basis weight and average thickness of the catalyst layer may be selected individually so as to suitably obtain the effects of the present invention.

[0026] The platinum weight per unit area of ​​the catalyst layer is 2.0 to 10.0 g / m from the viewpoint of appropriate mechanical strength and resource conservation. 2 It is preferable that the density is 3.0 to 9.0 g / m 2 More preferably, it is 4.0 to 8.0 g / m 2 It is more preferable that:

[0027] The weight of the insulating oxide containing crystalline zirconium contained in the catalyst layer is 0.1 to 20.0 g / m 2 It is preferable that the density is 0.3 to 10.0 g / m 2 More preferably, it is 0.5 to 3.0 g / m 2 When the basis weight of the insulating oxide containing crystalline zirconium is within the above range, the catalyst layer can / tends to suppress elution of nickel from the conductive substrate due to back charging and maintain a low overvoltage.

[0028] The catalyst layer may be in an embodiment including a zirconium layer containing an insulating oxide containing crystalline zirconium, and a platinum layer containing platinum on the surface of the zirconium layer. The catalyst layer may also be in a form including a mixed layer containing a mixture of platinum and an insulating oxide containing crystalline zirconium.

[0029] [[When zirconium layer and platinum layer are included]] In one embodiment, when the catalyst layer includes a zirconium layer containing an insulating oxide containing crystalline zirconium and a platinum layer containing platinum on the surface of the zirconium layer, the catalyst layer may include layers other than the zirconium layer and the platinum layer, but is preferably composed of the zirconium layer and the platinum layer. Although it is not clear why such excellent reverse current durability is obtained by using a cathode including a zirconium layer and a platinum layer, it is presumed that the zirconium layer coating the nickel surface of the conductive substrate significantly improves durability, suppresses the elution of nickel from the substrate surface, and provides corrosion resistance and suppresses the corrosion reaction on the surface of the conductive substrate even when a forward current that advances the intended electrolytic reaction and a reverse current (reverse current) that occurs after the forward current is stopped are repeatedly applied.

[0030] In the above embodiment, the weight of the zirconium layer is 0.1 g / m 2 or more, and the weight of the platinum layer is 2.0 g / m 2 When the basis weights of the zirconium layer and the platinum layer are each within the above ranges, the nickel surface of the conductive substrate is well coated with the zirconium layer and the platinum layer, thereby suppressing elution of nickel from the conductive substrate surface and preventing the catalyst layer on the substrate surface from falling off or peeling off.

[0031] The platinum layer has a weight of 2.0g / m 2 With this, the entire conductive substrate can be coated with platinum, and even if the catalyst layer is worn away by reverse current, a sufficient amount of platinum is guaranteed to maintain a low overvoltage. 2 If the thickness is less than this, the conductive substrate may be exposed in some areas, making it impossible to obtain a desired overvoltage. On the other hand, if the weight of the platinum layer is increased too much, the mechanical strength decreases and the catalyst layer becomes more likely to physically peel off. For this reason, the weight of the platinum layer is set to 10.0 g / m 2 It is preferable that: The weight of the platinum layer is 3.0 to 9.0 g / m 2 More preferably, it is 4.0 to 8.0 g / m2 It is more preferable that:

[0032] In addition, the weight of the zirconium layer is 0.1 g / m 2 If the above conditions are met, even if the catalyst layer is worn away by reverse current, elution of nickel from the conductive substrate is suppressed, and a low overvoltage can be maintained. On the other hand, if the weight of the zirconium layer is increased too much, it becomes a resistance component and the desired overvoltage cannot be obtained. For this reason, the weight of the zirconium layer is set to 20.0 g / m 2 It is preferable that: The weight of the zirconium layer is 0.3 to 10.0 g / m 2 More preferably, it is 0.5 to 3.0 g / m 2 It is more preferable that:

[0033] In the above embodiment, the average thickness of the zirconium layer is preferably 0.007 to 1.5 μm, more preferably 0.02 to 0.7 μm, and even more preferably 0.03 to 0.3 μm. When the average thickness of the zirconium layer is within the above range, a zirconium layer with fewer cracks can be formed.

[0034] From the viewpoint of covering the entire zirconium layer, the average thickness of the platinum layer is preferably 0.06 μm or more. If the platinum layer is thinner than 0.06 μm, the zirconium layer is exposed, and the overvoltage tends to increase. Furthermore, if the platinum layer is thicker than 2.0 μm, it becomes a resistive component and the desired overvoltage cannot be generated, so it is preferable that the thickness is 2.0 μm or less. The average thickness of the platinum layer is more preferably 0.1 to 1.0 μm, even more preferably 0.15 to 0.5 μm, and even more preferably 0.17 to 0.4 μm.

[0035] The ranges of the basis weight and average thickness of the zirconium layer and the basis weight and average thickness of the platinum layer may be selected individually to suitably obtain the effects of the present invention.

[0036] Examples of raw zirconium salts for the zirconium layer include zirconium oxynitrate, a dispersion of fine particles of zirconium oxide, and zirconium chloride.

[0037] [[When a mixed layer is included]] In another embodiment, when the catalyst layer includes a mixed layer containing a mixture of platinum and an insulating oxide containing crystalline zirconium, the catalyst layer may include layers other than the mixed layer, but preferably consists of only the mixed layer.

[0038] Although it is not clear why such excellent reverse current durability is obtained by using a cathode containing a zirconium layer and a platinum layer, it is presumed that the platinum penetrates into the gaps in the insulating oxide containing crystalline zirconium, thereby covering the conductive base material with a mixed layer having a dense structure in which platinum and crystalline zirconium are intricately intertwined. Therefore, even when a forward current that advances the intended electrolytic reaction and a reverse current (reverse current) that occurs after the forward current is stopped are repeatedly applied, the conductive base material has corrosion resistance and the corrosion reaction on the surface of the conductive base material is suppressed.

[0039] In the above embodiment, the weight of the insulating oxide containing crystalline zirconium is 0.1 g / m 2 or more, and the platinum weight is 2.0 g / m 2 When the basis weights of the crystalline zirconium-containing insulating oxide and platinum are each within the above-mentioned ranges, the nickel surface of the conductive substrate is well coated with the crystalline zirconium-containing insulating oxide and platinum, thereby suppressing elution of nickel from the conductive substrate surface and preventing the catalyst layer on the substrate surface from falling off or peeling off.

[0040] Platinum weight is 2.0g / m 2 In this case, even if the catalyst layer is depleted by reverse current, the amount of platinum is sufficient to maintain a low overvoltage. On the other hand, if the weight of platinum is increased too much, the mechanical strength decreases and the mixed layer becomes more susceptible to physical peeling. For this reason, the platinum weight is set at 40.0 g / m2 It is preferable that: The platinum weight is 4.0 to 20.0 g / m 2 More preferably, it is 6.0 to 10.0 g / m 2 It is more preferable that:

[0041] In addition, the weight of the insulating oxide containing crystalline zirconium is 0.1 g / m 2 If the above conditions are met, even if the catalyst layer is worn away by reverse current, elution of nickel from the conductive substrate is suppressed, and a low overvoltage can be maintained. On the other hand, if the weight of the insulating oxide containing crystalline zirconium is increased too much, it becomes a resistance component and the desired overvoltage cannot be obtained. For this reason, the weight of the insulating oxide containing crystalline zirconium is set to 20 g / m 2 It is preferable that: The weight of the insulating oxide containing crystalline zirconium is 0.5 to 10 g / m 2 More preferably, it is 0.8 to 5 g / m 2 It is more preferable that:

[0042] The ranges of the basis weights of the crystalline zirconium-containing insulating oxide and platinum may be selected individually to suitably obtain the effects of the present invention.

[0043] The mixed layer preferably has an average thickness of 0.05 μm or more. When the mixed layer has an average thickness of 0.05 μm or more, elution of nickel components from the surface of the conductive substrate is suppressed, and peeling of the catalyst layer can be suppressed. On the other hand, if the thickness of the mixed layer is too large, the mechanical strength decreases and the catalyst layer becomes more likely to physically peel off. For this reason, the average thickness of the mixed layer is preferably 3.0 μm or less. The average thickness of the mixed layer is more preferably 0.1 to 2.0 μm, and even more preferably 0.2 to 1.0 μm.

[0044] The ratio of zirconium atoms to metal atoms contained in the mixed layer is more preferably 1 to 90 mol %, more preferably 10 to 80 mol %, and even more preferably 20 to 60 mol %, from the viewpoint of low overvoltage and reverse current resistance.

[0045] From the viewpoint of low overvoltage and reverse current resistance, the ratio of platinum atoms to metal atoms contained in the mixed layer is more preferably 10 to 99 mol%, more preferably 40 to 90 mol%, and even more preferably 60 to 80 mol%.

[0046] The range of the average thickness of the mixed layer and the ratio of zirconium atoms and platinum atoms to the metal atoms contained in the mixed layer may each be selected individually to suitably obtain the effects of the present invention.

[0047] [Conductive base material] The conductive substrate constituting the cathode for hydrogen generation of this embodiment contains a metal including nickel in order to have resistance to the use environment. The shape of the conductive substrate is not particularly limited, and an appropriate shape can be selected depending on the purpose. Examples of shapes include punched metal, nonwoven fabric, foam metal, porous metal foil, expanded metal, and a so-called mesh made by weaving metal wires, and any of these can be used. Among these, mesh, foam metal, punched metal, and the like that do not have corners or protrusions are preferred from the viewpoint of achieving the effect of improving the reverse charge resistance described above. If the conductive substrate has corners or protrusions, such as expanded metal, the corners or protrusions can become starting points for interfacial peeling of the catalyst layer, making it difficult to achieve the above-mentioned effect.

[0048] When a mesh is used for the conductive substrate, the dimensions are not particularly limited, but in order to achieve both an increase in the amount of gas generated due to an increase in the electrolysis surface area and efficient removal of the gas generated by electrolysis from the electrode surface, the wire diameter is preferably 0.05 to 1.0 mm and the pitch is 20 to 60 mesh, more preferably 0.1 to 0.3 mm and 30 to 50 mesh.

[0049] When using foam metal as the conductive substrate, there are no particular restrictions on the dimensions, but the specific surface area should be 200 to 6000 m to achieve both an increase in the amount of gas generated due to an increase in the electrolytic surface area and efficient removal of the gas generated by electrolysis from the electrode surface. 2 / m 3 is preferable, 1000 to 6000 m 2 / m 3 is more preferable.

[0050] When a perforated metal is used as the conductive substrate, the dimensions are not particularly limited. However, in order to achieve both an increase in the amount of gas generated due to an increase in the electrolysis surface area and efficient removal of the gas generated by electrolysis from the electrode surface, and from the viewpoint of mechanical strength, the hole diameter is preferably 2 to 8 mm, the pitch is 2 to 10 mm, the opening ratio is 20 to 80%, and the thickness is preferably 0.5 to 2 mm. The sheet material before being processed into a punched metal is preferably a rolled sheet material, electrolytic foil, etc. The electrolytic foil is preferably further subjected to post-treatment of plating with the same elements as the base material to form irregularities on one or both sides.

[0051] The thickness (gauge thickness) of the conductive substrate is not particularly limited, but from the viewpoints of obtaining good handleability, having good adhesive strength with diaphragms such as ion exchange membranes and microporous membranes, and with current collectors, and being easy to handle, the thickness is preferably 300 μm or less, more preferably 100 μm or less, and from the viewpoints of handleability and economy, the thickness is even more preferably 50 μm or less.

[0052] In the case of the conductive substrate, it is preferable to alleviate residual stress during processing by annealing the conductive substrate in an oxidizing atmosphere. Furthermore, the conductive substrate is preferably subjected to a treatment to increase the surface area in order to improve adhesion to the catalyst layer, such as blasting using cut wire, steel grid, alumina grid, or the like, acid treatment using sulfuric acid or hydrochloric acid, or plating with the same element as the substrate. The arithmetic mean surface roughness (Ra) of the substrate surface is not particularly limited, but is preferably 0.05 to 50 μm, more preferably 0.1 to 10 μm, and even more preferably 0.1 to 8 μm. The arithmetic mean surface roughness (Ra) of the substrate surface can be measured using a stylus surface roughness measuring instrument.

[0053] Requirements for a cathode for hydrogen generation include low overvoltage and resistance to corrosion of the cathode substrate and catalytic layer, detachment of the catalytic layer, dissolution in the electrolyte, adhesion of inclusions to the diaphragm, etc., even when an unstable current such as that from renewable energy is used.

[0054] The cathode for hydrogen generation in this embodiment is preferably a porous body in order to increase the surface area available for electrolysis and to efficiently remove gas generated by electrolysis from the electrode surface. In particular, in the case of a zero-gap electrolytic cell, it is necessary to degas the gas generated from the back side of the surface in contact with the diaphragm, so it is preferable that the surface of the cathode opposite to the surface in contact with the membrane is perforated.

[0055] The surface of the cathode may be coated with a layer containing at least one platinum group element selected from the group consisting of ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), and iridium (Ir) in addition to Pt and Zr. This further reduces the overvoltage of the cathode. The platinum group element contained in the layer on the surface of the cathode is preferably Pd or Ir.

[0056] [Method of manufacturing cathode for hydrogen generation] Examples of a method for producing the cathode for hydrogen generation of this embodiment, i.e., a method for forming a catalytic layer on a conductive substrate, include a plating method, a thermal spraying method such as a plasma spraying method, a pyrolysis method in which a precursor layer solution is applied to a substrate and then heat is applied, a method in which a catalytic substance is mixed with a binder component and then fixed to a substrate, and a vacuum film formation method such as a sputtering method.

[0057] The pyrolysis method allows the formation of a thin film of uniform thickness on a porous substrate, which allows the substrate surface to be efficiently coated with a small amount of raw material. The thermal decomposition method preferably includes a coating step of coating a coating liquid containing a catalyst onto the surface of a substrate, a precursor layer forming step of drying the coating liquid to form a precursor layer, and a firing step of heating the substrate on whose surface the precursor layer has been formed to pyrolyze the precursor layer and form a catalyst layer.

[0058] The coating step may be, for example, a method of coating a coating liquid containing a metal element onto the surface of the substrate. Examples of metal elements include Pt, Zr, and at least one platinum group element selected from the group consisting of Ru, Rh, Pd, Os, and Ir. The form of the metal in the coating solution is not particularly limited, and it may be in the form of fine particles of the metal or metal compound, or may be dissolved and ionized. In the case of fine particles, it is preferable that the metal is dispersed in the solution to form a homogeneous precursor layer. Therefore, the particle size is preferably 100 nm or less. In the case of ionized metal salts, examples include halide salts such as fluorides, chlorides, bromides, and iodides; inorganic compound salts such as nitrates, sulfates, and phosphates; and organic compound salts such as acetates. Among these, chlorides and nitrates are preferred because the raw materials are industrially available. Furthermore, nitrates are more preferred because they minimize degradation of the substrate due to the anionic components remaining after decomposition, allowing for the production of electrodes with good storage stability. The solvent for the solution may be any solvent capable of dissolving the solute, such as a metal salt. Since a high-concentration solution can be prepared, which increases the coating amount and improves productivity, it is preferable for the solution to contain at least one of water or an alcohol having 2 to 5 carbon atoms. If the metal salt concentration in the solution is low, a lot of energy is required to volatilize the solvent. On the other hand, if the metal salt concentration is high, unevenness may occur, resulting in an uneven thickness of the catalyst layer. Therefore, the metal salt concentration in the coating solution used in the precursor formation step is preferably 0.001 to 1 mol / L, more preferably 0.01 to 0.5 mol / L.

[0059] In the coating step, various known methods can be used to coat the substrate surface with a coating liquid containing a metal element. For example, a dip method in which the substrate is immersed in the liquid, a method in which the substrate is coated with the liquid using a brush, a roll method in which a sponge roll is impregnated with the liquid and the substrate is coated with the liquid, and an electrostatic coating method in which the coating liquid and the substrate are charged with opposite charges and sprayed using a spray or the like. In particular, the roll method and the electrostatic coating method are preferably used in terms of productivity and the ability to uniformly coat the catalyst layer. Prior to applying the coating liquid to the substrate, the substrate may be subjected to a surface treatment to provide irregularities on the surface. Providing irregularities on the substrate surface improves the adhesion between the substrate and the catalyst layer. The method of surface treatment is not particularly limited, and examples thereof include blasting and etching using a chemical solution.

[0060] In the precursor layer forming step, the drying temperature when the coating liquid applied to the substrate surface is dried to form the precursor layer is preferably 40 to 200° C., more preferably 60 to 150° C. The drying time is preferably 1 to 60 minutes, more preferably It lasts for 5 to 30 minutes.

[0061] The calcination temperature for forming the catalyst layer in the calcination step should be equal to or higher than the thermal decomposition temperature of the metal salt used, but is preferably 300°C or higher. This is because the thermal decomposition of many metal salts proceeds at 300°C or higher. To ensure good thermal decomposition and removal of unreacted substances, the calcination temperature is preferably 400°C or higher, more preferably 500°C or higher. Calcination at a temperature higher than 1000°C may cause the substrate to soften and deform, so the calcination temperature is preferably 1000°C or lower, more preferably 800°C or lower, and even more preferably 600°C or lower. The calcination time is preferably 1 to 60 minutes, more preferably 5 to 60 minutes, and even more preferably 5 to 30 minutes.

[0062] It is preferable to repeat the precursor layer forming step and the calcination step multiple times. To form a catalyst layer of the desired thickness, the amount of liquid applied per time or the concentration of the metal salt in the coating liquid can be adjusted. However, if the amount of liquid applied per time or the metal concentration in the coating liquid is too high, unevenness may occur, and each layer may not be formed uniformly. Therefore, by repeating the precursor layer forming step and the calcination step multiple times, a more uniform catalyst layer of the desired thickness can be formed. The number of repetitions is not particularly limited as long as the desired thickness is obtained, but 5 to 30 times is preferred.

[0063] After repeating the precursor layer forming step and the firing step multiple times, a main firing step may be further included in order to enhance crystallinity. The main firing temperature is preferably 1000°C or lower, more preferably 800°C or lower. The main firing time is preferably 5 minutes to 24 hours, more preferably 30 minutes to 10 hours, and even more preferably 60 minutes to 5 hours. The temperature and time ranges for the main baking may be selected individually to suitably obtain the effects of the present invention.

[0064] When manufacturing a cathode for hydrogen generation having a catalyst layer including a zirconium layer containing an insulating oxide containing crystalline zirconium on a conductive base material and a platinum layer containing platinum on the surface of the zirconium layer, for example, a coating liquid containing at least zirconium is applied to the surface of the conductive base material (coating step 1), the coating liquid is dried (precursor layer formation step 1), and the resulting mixture is fired (thermal decomposition and crystallization) in an oxygen-containing atmosphere such as air (firing step 1) to form a zirconium layer containing an insulating oxide containing crystalline zirconium. The zirconium layer thus formed is formed using a solution (coating liquid) as a raw material, and therefore is a dense oxide layer (ZrO layer), unlike when formed using a ZrO sol, which will be described later. Next, a coating liquid containing at least a platinum compound is applied to the surface of the zirconium layer (coating step 2), the coating liquid is dried (precursor layer formation step 2), and the resulting mixture is fired (thermal decomposition and crystallization) in an oxygen-containing atmosphere such as air (firing step 2), thereby forming a platinum layer on the dense ZrO layer. The firing is preferably carried out in two stages: a preliminary firing for thermally decomposing ZrO2 and platinum, and a main firing for crystallizing them. The calcination (thermal decomposition) temperature for forming the zirconium layer is 100 to 700° C., preferably 200 to 650° C., more preferably 300 to 600° C., and even more preferably 400 to 550° C., from the viewpoint of removing organic and inorganic substances from the raw materials such as zirconium nitrate. The calcination (thermal decomposition) time is preferably 1 to 60 minutes, and more preferably 5 to 30 minutes. The firing (main firing) temperature for crystallizing zirconium oxide is preferably 200 to 800°C, more preferably 300 to 750°C, even more preferably 400 to 700°C, and even more preferably 450 to 650°C, in order to crystallize ZrO2. The main firing time is preferably 0.5 to 24 hours, and more preferably 1 to 10 hours. If the firing time is less than 0.5 hours, the crystallization of the ZrO2 layer does not proceed easily. The calcination (thermal decomposition) temperature for forming the platinum layer is 100 to 700° C., preferably 200 to 650° C., more preferably 300 to 600° C., and even more preferably 400 to 550° C. The calcination (thermal decomposition) time is preferably 1 to 60 minutes, and more preferably 5 to 30 minutes. The firing (main firing) temperature for crystallizing platinum is preferably 200 to 800°C, more preferably 300 to 750°C, even more preferably 400 to 700°C, and even more preferably 450 to 650°C. As the raw material salt of zirconium used in the zirconium-containing coating liquid, zirconium oxynitrate, a dispersion of fine particles of zirconium oxide, zirconium chloride, etc. can be used. As the coating liquid containing a platinum compound, a dinitrodiammine platinum nitrate solution, a hexaammine platinum solution, a platinum chloride solution, or the like can be used.

[0065] When a hydrogen generation cathode having a catalyst layer including a mixed layer containing a mixture of platinum and an insulating oxide containing crystalline zirconium on a conductive base material is produced, the mixed layer can be formed, for example, by applying a coating liquid containing at least a platinum compound and zirconium to the surface of the conductive base material (coating step), drying the coating liquid (precursor layer forming step), and firing (thermal decomposition and crystallization) in an oxygen-containing atmosphere such as air (firing step). The firing is preferably carried out in two stages: a preliminary firing for thermally decomposing ZrO2 and platinum, and a main firing for crystallizing them. The calcination (pyrolysis) temperature for forming the mixed layer is 100 to 800° C., preferably 250 to 800° C., more preferably 350 to 700° C., and even more preferably 450 to 600° C. The calcination (pyrolysis) time is preferably 5 to 60 minutes, and more preferably 5 to 30 minutes. The firing (main firing) temperature for crystallizing the mixed layer is preferably 200 to 800°C, more preferably 300 to 750°C, even more preferably 400 to 700°C, and even more preferably 450 to 650°C, in order to crystallize platinum and ZrO2. The main firing time is preferably 0.5 to 24 hours, and more preferably 1 to 10 hours. If the firing time is less than 0.5 hours, the crystallization of ZrO2 does not proceed easily. As the raw material salt of zirconium used in the coating liquid containing a platinum compound and zirconium, for example, ZrO2 sol can be used, and as the platinum compound, dinitrodiammine platinum nitrate solution, hexaammine platinum solution, platinum chloride solution, etc. can be used. The ZrO2 sol is a solution in which ZrO2 particles having a size of several nanometers to several tens of nanometers are dispersed. The particle size of the ZrO2 particles is preferably 1 to 100 nm, more preferably 10 to 50 nm.

[0066] Another method for producing a hydrogen generation cathode having a catalyst layer including a mixed layer containing a mixture of platinum and an insulating oxide containing crystalline zirconium on a conductive substrate is to apply ZrO sol diluted with distilled water to a desired concentration to the surface of the conductive substrate (application step 1), dry the ZrO sol (precursor layer formation step 1), and then calcinate (thermal decomposition and crystallization) the ZrO sol in an oxygen-containing atmosphere such as air (calcination step 1), thereby forming a zirconium layer containing an insulating oxide containing crystalline zirconium. Next, a coating liquid containing at least a platinum compound is applied to the surface of the zirconium layer (coating step 2), the coating liquid is dried (precursor layer formation step 2), and the layer is fired (thermal decomposition and crystallization) in an oxygen-containing atmosphere such as air (firing step 2), whereby platinum penetrates into the gaps between the ZrO2 particles, forming a mixed layer containing a mixture of platinum and an insulating oxide containing crystalline zirconium. The firing is preferably carried out in two stages: a preliminary firing for thermally decomposing ZrO2 and platinum, and a main firing for crystallizing them. The calcination (pyrolysis) temperature for forming the mixed layer is preferably 100 to 700° C., more preferably 200 to 650° C., and even more preferably 300 to 600° C. The calcination (pyrolysis) time is preferably 1 to 60 minutes, and more preferably 5 to 30 minutes. The firing (main firing) temperature for crystallizing the mixed layer is preferably 200 to 800°C, more preferably 300 to 750°C, even more preferably 400 to 700°C, and even more preferably 450 to 650°C, in order to crystallize platinum and ZrO2. The main firing time is preferably 0.5 to 24 hours, and more preferably 1 to 10 hours. If the firing time is less than 0.5 hours, the crystallization of ZrO2 does not proceed easily. The preferred range of particle size for the ZrO2 fine particles in the ZrO2 sol is the same as the range described above. As the coating liquid containing a platinum compound, a dinitrodiammine platinum nitrate solution, a hexaammine platinum solution, a platinum chloride solution, or the like can be used. [Example]

[0067] The present invention will now be described with reference to examples and examples. Reference examples and The present invention will be explained in more detail using comparative examples, but it goes without saying that the present invention is not limited to these examples and can be practiced with various modifications within the scope of the present invention.

[0068] Example , reference example The raw materials used in the comparative examples are described below.

[0069] (Coating liquid) The coating solution was prepared as follows: Coating solution 1: A solution prepared by dissolving zirconium oxynitrate dihydrate (manufactured by Kanto Chemical) in distilled water to a concentration of 1% by mass. Coating solution 2: Dinitrodiammine platinum nitrate solution (Tanaka Kikinzoku) dissolved in distilled water to a platinum concentration of 25 g / L. Coating solution 3: A solution prepared by dissolving zirconium oxide sol (manufactured by Taki Chemical Co., Ltd.) in distilled water to a concentration of 1% by mass. Coating solution 4: Zirconium oxynitrate dihydrate (Kanto Chemical) and cerium nitrate hexahydrate (Kanto Chemical) were mixed so that the molar ratio of zirconium to cerium was 75:25, and the mixture was dissolved in distilled water to a concentration of 1% by mass. Coating solution 5: Zirconium oxide sol (manufactured by Taki Chemical) and yttrium nitrate (manufactured by Kanto Chemical) were mixed so that the molar ratio of zirconium to yttrium was 92:8, and the mixture was dissolved in distilled water to a concentration of 1% by mass. Coating solution 6: A solution prepared by dissolving zirconium oxynitrate dihydrate (manufactured by Kanto Chemical) in distilled water to a concentration of 0.1% by mass. Coating solution 7: A solution prepared by dissolving zirconium oxide sol (manufactured by Taki Chemical Co., Ltd.) in distilled water to a concentration of 0.1% by mass. Coating solution 8: Dinitrodiammine platinum nitrate solution (manufactured by Tanaka Kikinzoku) and zirconium oxynitrate dihydrate (manufactured by Kanto Chemical) were mixed so that the molar ratio of platinum to zirconium was 80:20, and the mixture was dissolved in distilled water to a concentration of 5% by mass. Coating solution 9: A solution prepared by dissolving 3.04 mg of dinitrodiammineplatinum(II) and 1.69 mg of zirconium nitrate dihydrate in an 8% aqueous nitric acid solution so that the molar ratio of platinum to zirconium was 60:40. Coating solution 10: A solution prepared by mixing a palladium nitrate solution (Tanaka Precious Metals) and a dinitrodiammine platinum nitrate solution (Tanaka Precious Metals) so that the molar ratio of palladium to platinum was 50:50, and dissolving the mixture in distilled water to a concentration of 2.5% by mass.

[0070] Example 1 The conductive substrate was a plain-woven mesh substrate made of nickel fine wires with a circular cross section and a diameter of 0.15 mm woven at a mesh size of 40. The conductive substrate was blasted with alumina powder having a weight-average particle size of 100 μm or less, and then cut into a size of 8.5 cm × 17.0 cm. The substrate was then acid-treated in 6N hydrochloric acid at room temperature for 10 minutes, washed with water, and dried. The dried conductive substrate was heated and sintered in a muffle furnace at 500°C for 30 minutes to form a nickel oxide layer on the surface of the conductive substrate. The weight of the conductive substrate after heating and sintering was measured using a PG503-S electronic balance manufactured by Mettler-Toledo K.K.

[0071] -Coating process 1- A tray containing the above-mentioned coating liquid 1 was placed at the bottom of the coating roll, an EPDM coating roll was soaked with the coating liquid 1, a roll was placed above it so that the roll and coating liquid 1 were always in contact, and a PVC roller was placed on top of that, and the coating liquid 1 was applied to the conductive substrate (roll method). Before the coating liquid 1 dried, the conductive substrate was quickly passed between two EPDM sponge rolls, and the coating liquid that accumulated at the intersections of the mesh of the conductive substrate was absorbed and removed.

[0072] -Precursor layer formation process 1- The conductive substrate subjected to the coating step 1 was dried at 60° C. for 10 minutes to form a precursor layer.

[0073] -Firing process 1- The conductive substrate on which the precursor layer was formed was subjected to a heat treatment in an air atmosphere at 500° C. for 10 minutes using a muffle furnace to pyrolyze the precursor layer. This cycle of the coating step 1, precursor layer forming step 1, and firing step 1 was repeated five times. Then, main firing was carried out in an air atmosphere at 550° C. for three hours to prepare a cathode (1-1). The weight of the cathode (1-1) was measured using an electronic balance, and the difference between the weight of the conductive substrate before the formation of the zirconium layer was divided by the area of ​​8.5 cm × 17.0 cm to calculate the weight of the zirconium layer per unit area (basis weight).

[0074] -Coating process 2- A tray containing the coating liquid 2 was placed at the bottom of the coating roll, an EPDM coating roll was soaked with the coating liquid 2, a roll was placed above it so that the roll and the coating liquid 2 were always in contact, and a PVC roller was placed on top of that, and the coating liquid 2 was applied to the cathode (1-1) (roll method). Before the coating liquid 2 dried, the conductive substrate was quickly passed between two EPDM sponge rolls, and the coating liquid that accumulated at the intersections of the mesh of the conductive substrate was absorbed and removed.

[0075] -Precursor layer formation process 2- The cathode (1-1) subjected to the coating step 2 was dried at 60° C. for 10 minutes to form a precursor layer.

[0076] -Firing process 2- The cathode (1-1) on which the precursor layer was formed was subjected to a heat treatment in an air atmosphere at 500° C. for 10 minutes using a muffle furnace to pyrolyze the precursor layer. This cycle of the coating step 2, precursor layer forming step 2, and firing step 2 was repeated eight times. Further, main firing was carried out in an air atmosphere at 500° C. for one hour to prepare a cathode (1-2). The weight of the cathode (1-2) was measured using an electronic balance, and the difference between the weight of the cathode (1-2) and the weight of the cathode (1-1) before the platinum layer was formed was divided by the area of ​​8.5 cm x 17.0 cm to calculate the weight of the platinum layer per unit area (basis weight).

[0077] Example 2 The conductive substrate was a plain-woven mesh substrate made of nickel fine wires with a circular cross section and a diameter of 0.15 mm woven at a mesh size of 40. The conductive substrate was blasted with alumina powder having a weight-average particle size of 100 μm or less, and then cut into a size of 8.5 cm × 17.0 cm. The substrate was then acid-treated in 6N hydrochloric acid at room temperature for 10 minutes, washed with water, and dried. The dried conductive substrate was heated and sintered in a muffle furnace at 500°C for 30 minutes to form a nickel oxide layer on the surface of the conductive substrate. The weight of the conductive substrate after heating and sintering was measured using a PG503-S electronic balance manufactured by Mettler-Toledo K.K.

[0078] -Coating process 1- A tray containing the above-mentioned coating liquid 1 was placed at the bottom of the coating roll, an EPDM coating roll was soaked with the coating liquid 1, a roll was placed above it so that the roll and coating liquid 1 were always in contact, and a PVC roller was placed on top of that, and the coating liquid 1 was applied to the conductive substrate (roll method). Before the coating liquid 1 dried, the conductive substrate was quickly passed between two EPDM sponge rolls, and the coating liquid that accumulated at the intersections of the mesh of the conductive substrate was absorbed and removed.

[0079] -Precursor layer formation process 1- The conductive substrate subjected to the coating step was dried at 60° C. for 10 minutes to form a precursor layer.

[0080] -Firing process 1- The conductive substrate on which the precursor layer was formed was subjected to a heat treatment in an air atmosphere at 500° C. for 10 minutes using a muffle furnace to pyrolyze the precursor layer. This cycle of the coating step 1, precursor layer forming step 1, and firing step 1 was repeated 22 times. Further, main firing was carried out in an air atmosphere at 600° C. for 4 hours to prepare a cathode (2-1). The weight of the cathode (2-1) was measured using an electronic balance, and the difference between the weight of the cathode (2-1) and the weight of the conductive substrate before the formation of the zirconium layer was divided by the area of ​​8.5 cm × 17.0 cm to calculate the weight of the zirconium layer per unit area (basis weight).

[0081] -Coating process 2- A tray containing the coating liquid 2 was placed at the bottom of the coating roll, an EPDM coating roll was soaked with the coating liquid 2, a roll was placed above it so that the roll and coating liquid 2 were always in contact, and a PVC roller was placed on top of that, and the coating liquid 2 was applied to the cathode (2-1) (roll method). Before the coating liquid 2 dried, the conductive substrate was quickly passed between two EPDM sponge rolls, and the coating liquid that accumulated at the intersections of the mesh of the conductive substrate was absorbed and removed.

[0082] -Precursor layer formation process 2- The cathode (2-1) subjected to the coating step 2 was dried at 60° C. for 10 minutes to form a precursor layer.

[0083] -Firing process 2- The cathode (2-1) on which the precursor layer was formed was subjected to a heat treatment in an air atmosphere at 500° C. for 10 minutes using a muffle furnace to pyrolyze the precursor layer. This cycle of the coating step 2, the precursor layer forming step 2, and the baking step 2 was repeated nine times. Then, the resultant was subjected to main baking in an air atmosphere at 500° C. for one hour to prepare a cathode (2-2). The weight of the cathode (2-2) was measured using an electronic balance, and the difference between the weight of the cathode (2-2) and the weight of the cathode (2-1) before the platinum layer was formed was divided by the area of ​​8.5 cm x 17.0 cm to calculate the weight of the platinum layer per unit area (basis weight).

[0084] Example 3 The conductive substrate was a plain-woven mesh substrate made of nickel fine wires with a circular cross section and a diameter of 0.15 mm woven at a mesh size of 40. The conductive substrate was blasted with alumina powder having a weight-average particle size of 100 μm or less, and then cut into a size of 8.5 cm × 17.0 cm. The substrate was then acid-treated in 6N hydrochloric acid at room temperature for 10 minutes, washed with water, and dried. The dried conductive substrate was heated and sintered in a muffle furnace at 500°C for 30 minutes to form a nickel oxide layer on the surface of the conductive substrate. The weight of the conductive substrate after heating and sintering was measured using a PG503-S electronic balance manufactured by Mettler-Toledo K.K.

[0085] -Coating process 1- A tray containing the above-mentioned coating liquid 1 was placed at the bottom of the coating roll, an EPDM coating roll was soaked with the coating liquid 1, a roll was placed above it so that the roll and coating liquid 1 were always in contact, and a PVC roller was placed on top of that, and the coating liquid 1 was applied to the conductive substrate (roll method). Before the coating liquid 1 dried, the conductive substrate was quickly passed between two EPDM sponge rolls, and the coating liquid that accumulated at the intersections of the mesh of the conductive substrate was absorbed and removed.

[0086] -Precursor layer formation process 1- The conductive substrate subjected to the coating step 1 was dried at 60° C. for 10 minutes to form a precursor layer.

[0087] -Firing process 1- The conductive substrate on which the precursor layer was formed was subjected to a heat treatment in an air atmosphere at 500° C. for 10 minutes using a muffle furnace to pyrolyze the precursor layer. This cycle of the coating step 1, precursor layer forming step 1, and firing step 1 was repeated twice, followed by main firing at 560° C. for 3 hours in an air atmosphere to produce a cathode (3-1). The weight of the cathode (3-1) was measured using an electronic balance, and the difference between the weight of the cathode (3-1) and the weight of the conductive substrate before the formation of the zirconium layer was divided by the area of ​​8.5 cm × 17.0 cm to calculate the weight of the zirconium layer per unit area (basis weight).

[0088] -Coating process 2- A tray containing the coating liquid 2 was placed at the bottom of the coating roll, an EPDM coating roll was soaked with the coating liquid 2, a roll was placed above it so that the roll and coating liquid 2 were always in contact, and a PVC roller was placed on top of that, and the coating liquid 2 was applied to the cathode (3-1) (roll method). Before the coating liquid 2 dried, the conductive substrate was quickly passed between two EPDM sponge rolls, and the coating liquid that accumulated at the intersections of the mesh of the conductive substrate was absorbed and removed.

[0089] -Precursor layer formation process 2- The cathode (3-1) subjected to the coating step 2 was dried at 60° C. for 10 minutes to form a precursor layer.

[0090] -Firing process 2- The cathode (3-1) on which the precursor layer was formed was subjected to a heat treatment in an air atmosphere at 500° C. for 10 minutes using a muffle furnace to pyrolyze the precursor layer. This cycle of the coating step 2, precursor layer forming step 2, and baking step 2 was repeated five times. Then, baking was carried out in an air atmosphere at 500° C. for one hour to prepare a cathode (3-2). The weight of the cathode (3-2) was measured using an electronic balance, and the difference between the weight of the cathode (3-2) and the weight of the cathode (3-1) before the platinum layer was formed was divided by the area of ​​8.5 cm x 17.0 cm to calculate the weight of the platinum layer per unit area (basis weight).

[0091] Example 4 The conductive substrate was a plain-woven mesh substrate made of nickel fine wires with a circular cross section and a diameter of 0.15 mm woven at a mesh size of 40. The conductive substrate was blasted with alumina powder having a weight-average particle size of 100 μm or less, and then cut into a size of 8.5 cm × 17.0 cm. The substrate was then acid-treated in 6N hydrochloric acid at room temperature for 10 minutes, washed with water, and dried. The dried conductive substrate was heated and sintered in a muffle furnace at 500°C for 30 minutes to form a nickel oxide layer on the surface of the conductive substrate. The weight of the conductive substrate after heating and sintering was measured using a PG503-S electronic balance manufactured by Mettler-Toledo K.K.

[0092] -Coating process 1- A tray containing the coating liquid 3 was placed at the bottom of the coating roll, an EPDM coating roll was soaked with the coating liquid 3, a roll was placed above it so that the roll and the coating liquid 3 were always in contact, and a PVC roller was placed on top of that, and the coating liquid 3 was applied to the conductive substrate (roll method). Before the coating liquid 3 dried, the conductive substrate was quickly passed between two EPDM sponge rolls, and the coating liquid that accumulated at the intersections of the mesh of the conductive substrate was absorbed and removed.

[0093] -Precursor layer formation process 1- The conductive substrate subjected to the coating step 1 was dried at 60° C. for 10 minutes to form a precursor layer.

[0094] -Firing process 1- The conductive substrate on which the precursor layer was formed was subjected to a heat treatment in an air atmosphere at 500° C. for 10 minutes using a muffle furnace to pyrolyze the precursor layer. This cycle of the coating step 1, precursor layer forming step 1, and firing step 1 was repeated four times. Then, main firing was carried out in an air atmosphere at 500° C. for one hour to prepare a cathode (4-1). The weight of the cathode (4-1) was measured using an electronic balance, and the difference between the weight and the weight of the conductive base material before the formation of the catalyst layer was divided by the area of ​​8.5 cm × 17.0 cm to calculate the weight (basis weight) of the crystalline zirconium-containing insulating oxide per unit area.

[0095] -Coating process 2- A tray containing the coating liquid 2 was placed at the bottom of the coating roll, an EPDM coating roll was soaked with the coating liquid 2, a roll was placed above it so that the roll and coating liquid 2 were always in contact, and a PVC roller was placed on top of that, and the coating liquid 2 was applied to the cathode (4-1) (roll method). Before the coating liquid 2 dried, the conductive substrate was quickly passed between two EPDM sponge rolls, and the coating liquid that accumulated at the intersections of the mesh of the conductive substrate was absorbed and removed.

[0096] -Precursor layer formation process 2- The cathode (4-1) subjected to the coating step 2 was dried at 60° C. for 10 minutes to form a precursor layer.

[0097] -Firing process 2- The cathode (4-1) on which the precursor layer was formed was subjected to a heat treatment in an air atmosphere at 500° C. for 10 minutes using a muffle furnace to pyrolyze the precursor layer. This cycle of the coating step 2, the precursor layer forming step 2, and the baking step 2 was repeated seven times. Then, the resultant was baked in an air atmosphere at 500° C. for one hour to prepare a cathode (4-2). The weight of the cathode (4-2) was measured using an electronic balance, and the difference between the weight of the cathode (4-2) and the weight of the cathode (4-1) was divided by the area of ​​8.5 cm x 17.0 cm to calculate the weight of platinum per unit area (basis weight). 3A is a diagram showing the peak of X-rays diffracted by the (111) plane of nickel (Ni peak) and the peak of X-rays diffracted by the (012) plane of the insulating oxide containing crystalline zirconium (ZrO peak) in Example 4. Since the ZrO peak is observed, it was confirmed that the insulating oxide containing zirconium in Example 4 was crystalline. When the abundance ratio of oxygen, platinum, and zirconium in the catalyst layer of Example 4 was measured, the atomic ratio was O:Pt:Zr=39.5:46.0:14.5, and it was determined to be a mixed layer of platinum and zirconium oxide.

[0098] Example 5 A cathode was produced in the same manner as in Example 4, except that the cycle of application step 1, precursor layer forming step 1, and firing step 1 was repeated three times, and the cycle of application step 2, precursor layer forming step 2, and firing step 2 was repeated six times.

[0099] Example 6 A cathode was produced in the same manner as in Example 4, except that the cycle of coating step 1, precursor layer forming step 1, and firing step 1 was repeated twice, and the cycle of coating step 2, precursor layer forming step 2, and firing step 2 was repeated three times.

[0100] Example 7 The conductive substrate was a plain-woven mesh substrate made of nickel fine wires with a circular cross section and a diameter of 0.15 mm woven at a mesh size of 40. The conductive substrate was blasted with alumina powder having a weight-average particle size of 100 μm or less, and then cut into a size of 8.5 cm × 17.0 cm. The substrate was then acid-treated in 6N hydrochloric acid at room temperature for 10 minutes, washed with water, and dried. The dried conductive substrate was heated and sintered in a muffle furnace at 500°C for 30 minutes to form a nickel oxide layer on the surface of the conductive substrate. The weight of the conductive substrate after heating and sintering was measured using a PG503-S electronic balance manufactured by Mettler-Toledo K.K.

[0101] -Coating process 1- A tray containing the coating liquid 4 was placed at the bottom of the coating roll, an EPDM coating roll was soaked with the coating liquid 4, a roll was placed above it so that the roll and the coating liquid 4 were always in contact, and a PVC roller was placed on top of that to apply the coating liquid 4 to the conductive substrate (roll method). Before the coating liquid 4 dried, the conductive substrate was quickly passed between two EPDM sponge rolls, and the coating liquid that accumulated at the intersections of the mesh of the conductive substrate was absorbed and removed.

[0102] -Precursor layer formation process 1- The conductive substrate subjected to the coating step 1 was dried at 60° C. for 10 minutes to form a precursor layer.

[0103] -Firing process 1- The conductive substrate on which the precursor layer was formed was subjected to a heat treatment in an air atmosphere at 500° C. for 10 minutes using a muffle furnace to pyrolyze the precursor layer. This cycle of the coating step 1, precursor layer forming step 1, and firing step 1 was repeated four times. Then, main firing was carried out in an air atmosphere at 600° C. for three hours to produce a cathode (7-1). The weight of the cathode (7-1) was measured using an electronic balance, and the difference between the weight of the conductive substrate before and after the formation of the zirconium layer was divided by the area of ​​8.5 cm × 17.0 cm to calculate the weight of the zirconium layer per unit area (basis weight). The weight of zirconium oxide per unit area (basis weight) and the weight of cerium per unit area (basis weight) were determined from the molar ratio of zirconium to cerium.

[0104] -Coating process 2- A tray containing the coating liquid 2 was placed at the bottom of the coating roll, an EPDM coating roll was soaked with the coating liquid 2, a roll was placed above it so that the roll and coating liquid 2 were always in contact, and a PVC roller was placed on top of that, and the coating liquid 2 was applied to the cathode (7-1) (roll method). Before the coating liquid 2 dried, the conductive substrate was quickly passed between two EPDM sponge rolls, and the coating liquid that accumulated at the intersections of the mesh of the conductive substrate was absorbed and removed.

[0105] -Precursor layer formation process 2- The cathode (7-1) that had been subjected to the coating process was dried at 60° C. for 10 minutes to form a precursor layer.

[0106] -Firing process 2- The cathode (7-1) on which the precursor layer was formed was subjected to a heat treatment in an air atmosphere at 500° C. for 10 minutes using a muffle furnace to pyrolyze the precursor layer. This cycle of the coating step 2, the precursor layer forming step 2, and the baking step 2 was repeated six times. Then, the resultant was baked in an air atmosphere at 500° C. for one hour to prepare a cathode (7-2). The weight of the cathode (7-2) was measured using an electronic balance, and the difference between the weight of the cathode (7-2) and the weight of the cathode (7-1) before the platinum layer was formed was divided by the area of ​​8.5 cm x 17.0 cm to calculate the weight of the platinum layer per unit area (basis weight).

[0107] Example 8 The conductive substrate was a plain-woven mesh substrate made of nickel fine wires with a circular cross section and a diameter of 0.15 mm woven at a mesh size of 40. The conductive substrate was blasted with alumina powder having a weight-average particle size of 100 μm or less, and then cut into a size of 8.5 cm × 17.0 cm. The substrate was then acid-treated in 6N hydrochloric acid at room temperature for 10 minutes, washed with water, and dried. The dried conductive substrate was heated and sintered in a muffle furnace at 500°C for 30 minutes to form a nickel oxide layer on the surface of the conductive substrate. The weight of the conductive substrate after heating and sintering was measured using a PG503-S electronic balance manufactured by Mettler-Toledo K.K.

[0108] -Coating process 1- A tray containing the coating liquid 5 was placed at the bottom of a coating roll, an EPDM coating roll was soaked with the coating liquid 5, a roll was placed above it so that the roll and the coating liquid 5 were always in contact, and a PVC roller was placed on top of that, and the coating liquid 5 was applied to the conductive substrate (roll method). Before the coating liquid 5 dried, the conductive substrate was quickly passed between two EPDM sponge rolls, and the coating liquid that accumulated at the intersections of the mesh of the conductive substrate was absorbed and removed.

[0109] -Precursor layer formation process 1- The conductive substrate subjected to the coating step 1 was dried at 60° C. for 10 minutes to form a precursor layer.

[0110] -Firing process 1- The conductive substrate on which the precursor layer was formed was subjected to a heat treatment in an air atmosphere at 500° C. for 10 minutes using a muffle furnace to pyrolyze the precursor layer. This cycle of the coating step 1, precursor layer forming step 1, and firing step 1 was repeated 10 times. Further, main firing was carried out in an air atmosphere at 550° C. for 3 hours to prepare a cathode (8-1). The weight of the cathode (8-1) was measured using an electronic balance, and the difference between the weight of the cathode (8-1) and the weight of the conductive substrate before the formation of the catalyst layer was divided by the area of ​​8.5 cm × 17.0 cm to calculate the weight (basis weight) of the crystalline zirconium-containing insulating oxide per unit area. The weight (basis weight) of the zirconium oxide per unit area and the weight (basis weight) of yttrium per unit area were determined from the molar ratio of zirconium to yttrium.

[0111] -Coating process 2- A tray containing the coating liquid 2 was placed at the bottom of the coating roll, an EPDM coating roll was soaked with the coating liquid 2, a roll was placed above it so that the roll and coating liquid 2 were always in contact, and a PVC roller was placed on top of that, and the coating liquid 2 was applied to the cathode (8-1) (roll method). Before the coating liquid 2 dried, the conductive substrate was quickly passed between two EPDM sponge rolls, and the coating liquid that accumulated at the intersections of the mesh of the conductive substrate was absorbed and removed.

[0112] -Precursor layer formation process 2- The cathode (8-1) subjected to the coating step 1 was dried at 60° C. for 10 minutes to form a precursor layer.

[0113] -Firing process 2- The cathode (8-1) on which the precursor layer was formed was subjected to a heat treatment in an air atmosphere at 500° C. for 10 minutes using a muffle furnace to pyrolyze the precursor layer. This cycle of the coating step 2, precursor layer forming step 2, and baking step 2 was repeated 20 times. Further, the resultant was subjected to main baking in an air atmosphere at 500° C. for 1 hour to prepare a cathode (8-2). The weight of the cathode (8-2) was measured using an electronic balance, and the difference between the weight of the cathode (8-2) and the weight of the cathode (8-1) was divided by the area of ​​8.5 cm x 17.0 cm to calculate the weight of platinum per unit area (basis weight).

[0114] Example 9 The conductive substrate was a plain-woven mesh substrate made of nickel fine wires with a circular cross section and a diameter of 0.15 mm woven at a mesh size of 40. The conductive substrate was blasted with alumina powder having a weight-average particle size of 100 μm or less, and then cut into a size of 8.5 cm × 17.0 cm. The substrate was then acid-treated in 6N hydrochloric acid at room temperature for 10 minutes, washed with water, and dried. The dried conductive substrate was heated and sintered in a muffle furnace at 500°C for 30 minutes to form a nickel oxide layer on the surface of the conductive substrate. The weight of the conductive substrate after heating and sintering was measured using a PG503-S electronic balance manufactured by Mettler-Toledo K.K.

[0115] -Coating process 1- A tray containing the above-mentioned coating liquid 1 was placed at the bottom of the coating roll, an EPDM coating roll was soaked with the coating liquid 1, a roll was placed above it so that the roll and coating liquid 1 were always in contact, and a PVC roller was placed on top of that, and the coating liquid 1 was applied to the conductive substrate (roll method). Before the coating liquid 1 dried, the conductive substrate was quickly passed between two EPDM sponge rolls, and the coating liquid that accumulated at the intersections of the mesh of the conductive substrate was absorbed and removed.

[0116] -Precursor layer formation process 1- The conductive substrate subjected to the coating step 1 was dried at 60° C. for 10 minutes to form a precursor layer.

[0117] -Firing process 1- The conductive substrate on which the precursor layer was formed was subjected to a heat treatment in an air atmosphere at 500° C. for 10 minutes using a muffle furnace to pyrolyze the precursor layer. This cycle of the coating step 1, precursor layer forming step 1, and firing step 1 was repeated four times. Then, main firing was carried out in an air atmosphere at 500° C. for one hour to prepare a cathode (9-1). The weight of the cathode (9-1) was measured using an electronic balance, and the difference between the weight of the cathode (9-1) and the weight of the conductive substrate before the formation of the zirconium layer was divided by the area of ​​8.5 cm x 17.0 cm to calculate the weight of the zirconium layer per unit area (basis weight).

[0118] -Coating process 2- A tray containing the coating liquid 3 was placed at the bottom of the coating roll, an EPDM coating roll was soaked with the coating liquid 3, a roll was placed above it so that the roll and the coating liquid 3 were always in contact, and a PVC roller was placed on top of that, and the coating liquid 3 was applied to the cathode (9-1) (roll method). Before the coating liquid 3 dried, the conductive substrate was quickly passed between two EPDM sponge rolls, and the coating liquid that accumulated at the intersections of the mesh of the conductive substrate was absorbed and removed.

[0119] -Precursor layer formation process 2- The cathode (9-1) subjected to the coating step 1 was dried at 60° C. for 10 minutes to form a precursor layer.

[0120] -Firing process 2- The cathode (9-1) on which the precursor layer was formed was subjected to a heat treatment in an air atmosphere at 500° C. for 10 minutes using a muffle furnace to pyrolyze the precursor layer. This cycle of the coating step 1, precursor layer forming step 1, and firing step 1 was repeated four times. Then, main firing was carried out in an air atmosphere at 500° C. for one hour to prepare a cathode (9-2). The weight of the cathode (9-2) was measured using an electronic balance, and the difference between the weight of the cathode (9-2) and the weight of the cathode (9-1) was divided by the area of ​​8.5 cm × 17.0 cm to calculate the weight (basis weight) of zirconium oxide per unit area of ​​the zirconium oxide layer formed on the cathode (9-1).

[0121] -Coating process 3- A tray containing the coating liquid 2 was placed at the bottom of the coating roll, an EPDM coating roll was soaked with the coating liquid 2, a roll was placed above it so that the roll and coating liquid 2 were always in contact, and a PVC roller was placed on top of that, and the coating liquid 2 was applied to the cathode (9-2) (roll method). Before the coating liquid 2 dried, the conductive substrate was quickly passed between two EPDM sponge rolls, and the coating liquid that accumulated at the intersections of the mesh of the conductive substrate was absorbed and removed.

[0122] -Precursor layer formation process 3- The cathode (9-2) subjected to the coating step 3 was dried at 60° C. for 10 minutes to form a precursor layer.

[0123] -Firing process 3- The cathode (9-2) on which the precursor layer was formed was subjected to a heat treatment in an air atmosphere at 500° C. for 10 minutes using a muffle furnace to pyrolyze the precursor layer. This cycle of the coating step 3, the precursor layer forming step 3, and the baking step 3 was repeated seven times. Further, the resultant was subjected to main baking at 500° C. for one hour in an air atmosphere to prepare a cathode (9-3). The weight of the cathode (9-3) was measured using an electronic balance, and the difference between the weight of the cathode (9-3) and the weight of the cathode (9-2) was divided by the area of ​​8.5 cm x 17.0 cm to calculate the weight of platinum per unit area (basis weight).

[0124] ( reference Example 10) A cathode was prepared in the same manner as in Example 1, except that foamed nickel (Celmet #4, manufactured by Sumitomo Electric Industries, Ltd.) was used as the conductive substrate.

[0125] ( reference Example 11) An electrolytic nickel foil with a gauge thickness of 16 μm was prepared as a conductive substrate. One side of this nickel foil was subjected to a surface roughening treatment by electrolytic nickel plating. Circular holes were punched into this nickel foil to form a porous foil. A cathode was produced in the same manner as in Example 1, except for using this nickel foil.

[0126] (Comparative Example 1) A cathode was produced in the same manner as in Example 1, except that the coating step 1, the precursor layer forming step 1, and the firing step 1 were not performed.

[0127] (Comparative Example 2) A cathode was produced in the same manner as in Example 1, except that the cycle of the application step 1, the precursor layer formation step 1 and the firing step 1 was repeated 32 times.

[0128] (Comparative Example 3) A cathode was produced in the same manner as in Example 1, except that Coating Liquid 6 was used in Coating Step 1, and the cycle of Coating Step 1, Precursor Layer Forming Step 1, and Firing Step 1 was repeated once.

[0129] Comparative Example 4 A cathode was produced in the same manner as in Example 4, except that the coating step 1, precursor layer forming step 1, and firing step 1 were not performed, and the cycle of the coating step 2, precursor layer forming step 2, and firing step 2 was repeated six times.

[0130] (Comparative Example 5) The conductive substrate was a plain-woven mesh substrate made of nickel fine wires with a circular cross section and a diameter of 0.15 mm woven at a mesh size of 40. The conductive substrate was blasted with alumina powder having a weight-average particle size of 100 μm or less, and then cut into a size of 8.5 cm × 17.0 cm. The substrate was then acid-treated in 6N hydrochloric acid at room temperature for 10 minutes, washed with water, and dried. The dried conductive substrate was heated and sintered in a muffle furnace at 500°C for 30 minutes to form a nickel oxide layer on the surface of the conductive substrate. The weight of the conductive substrate after heating and sintering was measured using a PG503-S electronic balance manufactured by Mettler-Toledo K.K.

[0131] -Coating process 1- A tray containing the coating liquid 8 was placed at the bottom of the coating roll, an EPDM coating roll was soaked with the coating liquid 8, a roll was placed above it so that the roll and coating liquid 8 were always in contact, and a PVC roller was placed on top of that to apply the coating liquid 8 to the conductive substrate (roll method). Before the coating liquid 8 dried, the conductive substrate was quickly passed between two EPDM sponge rolls, and the coating liquid that accumulated at the intersections of the meshes of the conductive substrate was absorbed and removed.

[0132] -Precursor layer formation process 1- The conductive substrate subjected to the coating step 1 was dried at 60° C. for 10 minutes to form a precursor layer.

[0133] -Firing process 1- The conductive substrate on which the precursor layer was formed was subjected to a heat treatment in an air atmosphere at 500° C. for 10 minutes using a muffle furnace to pyrolyze the precursor layer. This cycle of the coating step 1, precursor layer forming step 1, and firing step 1 was repeated eight times. Further, main firing was carried out in an air atmosphere at 500° C. for one hour to prepare a cathode (5-1). The weight of the cathode (5-1) was measured using an electronic balance, and the difference between the weight of the cathode (5-1) and the weight of the conductive substrate before the formation of the catalyst layer was divided by the area of ​​8.5 cm × 17.0 cm to calculate the weight of the catalyst layer per unit area (basis weight). The weight of platinum per unit area (basis weight) and the weight of zirconium per unit area (basis weight) were determined from the molar ratio of platinum to zirconium. 3B is a diagram showing the peaks (Ni peaks) of X-rays diffracted by the (111) plane of nickel in Comparative Example 5. No ZrO peak was observed, confirming that the zirconium-containing insulating oxide in Comparative Example 5 was not crystalline. In the catalyst layer of Comparative Example 5, the abundance ratios of oxygen, platinum, and zirconium were measured from the catalyst layer surface to 0.16 μm in the thickness direction. The atomic ratio was O:Pt:Zr=8.0:92.0:0, and it was determined that the catalyst layer was not a mixed layer of platinum and zirconium oxide, but a single platinum layer.

[0134] (Comparative Example 6) A cathode was produced in the same manner as in Example 4, except that the cycle of the application step 1, the precursor layer formation step 1 and the firing step 1 was repeated 23 times.

[0135] (Comparative Example 7) A cathode was produced in the same manner as in Example 4, except that Coating Liquid 7 was used in Coating Step 1, and the cycle of Coating Step 1, Precursor Layer Forming Step 1, and Firing Step 1 was repeated once.

[0136] (Comparative Example 8) Nickel expand metal (SW 3.8 × LW 8.0 × t 1.0 × st 1.2) was used as the conductive substrate, and its surface was blasted with #180 alumina, and then etched in 20% hydrochloric acid at room temperature for 60 minutes.

[0137] -Coating process 1- Coating Liquid 9 (70 mL) was applied to both sides of the conductive substrate with a brush.

[0138] -Precursor layer formation process 1- The conductive substrate subjected to the coating step 1 was dried at 100° C. for 10 minutes to form a precursor layer.

[0139] -Firing process 1- The conductive substrate on which the precursor layer was formed was heated and baked in an air atmosphere at 500° C. for 20 minutes using a muffle furnace to pyrolyze the precursor layer. The cycle of the coating step 1, the precursor layer forming step 1 and the baking step 1 was repeated several times to prepare a cathode (8-1). The weight of the cathode (8-1) was measured using an electronic balance, and the difference between the weight of the cathode (8-1) and the weight of the conductive substrate before the formation of the catalyst layer was divided by the area of ​​3.8 cm × 8.0 cm to calculate the weight of the catalyst layer per unit area (basis weight). The weight of platinum per unit area (basis weight) and the weight of zirconium per unit area (basis weight) were calculated from the molar ratio of platinum to zirconium.

[0140] Comparative Example 9 The conductive substrate was a plain-woven mesh substrate made of nickel fine wires with a circular cross section and a diameter of 0.15 mm woven at a mesh size of 40. The conductive substrate was blasted with alumina powder having a weight-average particle size of 100 μm or less, and then cut into a size of 8.5 cm × 17.0 cm. The substrate was then acid-treated in 6N hydrochloric acid at room temperature for 10 minutes, washed with water, and dried. The dried conductive substrate was heated and sintered in a muffle furnace at 500°C for 10 minutes to form a nickel oxide layer on the surface of the conductive substrate. The weight of the conductive substrate after heating and sintering was measured using a PG503-S electronic balance manufactured by Mettler-Toledo K.K.

[0141] -Coating process 1- A tray containing the coating liquid 10 was placed at the bottom of the coating roll, an EPDM coating roll was soaked with the coating liquid 10, a roll was placed above it so that the roll and the coating liquid 10 were always in contact, and a PVC roller was placed on top of that, and the coating liquid 10 was applied to the conductive substrate (roll method). Before the coating liquid 10 dried, the conductive substrate was quickly passed between two EPDM sponge rolls, and the coating liquid that accumulated at the intersections of the mesh of the conductive substrate was absorbed and removed.

[0142] -Precursor layer formation process 1- The conductive substrate subjected to the coating step 1 was dried at 50° C. for 10 minutes to form a precursor layer.

[0143] -Firing process 1- The conductive substrate on which the precursor layer was formed was heated and baked in an air atmosphere at 500° C. for 10 minutes using a muffle furnace to pyrolyze the precursor layer. This cycle of the coating step 1, precursor layer forming step 1, and firing step 1 was repeated five times. Then, main firing was carried out in an air atmosphere at 500° C. for 1 hour to prepare a cathode (9-1) having a thickness of 0.16 mm. The weight of the cathode (9-1) was measured using an electronic balance, and the difference between the weight of the cathode (9-1) and the weight of the conductive substrate before the formation of the catalyst layer was divided by the area of ​​8.5 cm × 17.0 cm to calculate the weight of the catalyst layer per unit area (basis weight). The weight of platinum per unit area (basis weight) was calculated from the molar ratio of palladium to platinum.

[0144] (Comparative Example 10) The conductive substrate was a plain-woven mesh substrate made of nickel fine wires with a circular cross section and a diameter of 0.15 mm woven at a mesh size of 40. The conductive substrate was blasted with alumina powder having a weight-average particle size of 100 μm or less, and then cut into a size of 8.5 cm × 17.0 cm. The substrate was then acid-treated in 6N hydrochloric acid at room temperature for 10 minutes, washed with water, and dried. The dried conductive substrate was heated and sintered in a muffle furnace at 500°C for 10 minutes to form a nickel oxide layer on the surface of the conductive substrate. The weight of the conductive substrate after heating and sintering was measured using a PG503-S electronic balance manufactured by Mettler-Toledo K.K. Next, a palladium nitrate solution (Tanaka Precious Metals) and a dinitrodiammine platinum nitrate solution (Tanaka Precious Metals) were mixed so that the molar ratio of palladium to platinum was 50:50 to prepare a coating liquid.

[0145] -Coating process 1- A tray containing the above-mentioned coating liquid 1 was placed at the bottom of the coating roll, an EPDM coating roll was soaked with the coating liquid 1, a roll was placed above it so that the roll and coating liquid 1 were always in contact, and a PVC roller was placed on top of that, and the coating liquid 1 was applied to the conductive substrate (roll method). Before the coating liquid 1 dried, the conductive substrate was quickly passed between two EPDM sponge rolls, and the coating liquid that accumulated at the intersections of the mesh of the conductive substrate was absorbed and removed.

[0146] -Precursor layer formation process 1- The conductive substrate subjected to the coating step 1 was dried at 50° C. for 10 minutes to form a precursor layer.

[0147] -Firing process 1- The conductive substrate on which the precursor layer was formed was heated and baked in an air atmosphere at 500° C. for 10 minutes using a muffle furnace to pyrolyze the precursor layer. This cycle of the coating step 1, precursor layer forming step 1, and firing step 1 was repeated 18 times. Further, main firing was carried out in an air atmosphere at 500° C. for 1 hour to prepare a cathode (10-1) having a thickness of 0.16 mm. The weight of the cathode (10-1) was measured using an electronic balance, and the difference between the weight of the cathode (10-1) and the weight of the conductive base material before the formation of the catalytic layer was divided by the area of ​​8.5 cm × 17.0 cm to calculate the weight of the catalytic layer per unit area (basis weight). The weight of platinum per unit area (basis weight) was then determined from the molar ratio of palladium to platinum.

[0148] Example , reference example The measurement and evaluation methods used in the comparative examples will be explained below.

[0149] (crystallinity) An X-ray diffraction chart of the cathode was obtained using an X-ray diffractometer (Rigaku Corporation, RINT2000 model) under measurement conditions of 40 kV excitation voltage, 200 mA excitation current, and 2θ / θ operation axis. Using the X-ray diffraction analysis software "JADE," peaks derived from the Kα line in the X-ray diffraction chart were removed, and baseline correction was performed to calculate the peak intensity I of the X-ray diffracted by the (111) plane of nickel, and the peak intensity IZrO2 of the X-ray diffracted by the (012) plane of the crystalline zirconium-containing insulating oxide. The crystallinity IZrO2 / INi × 100 was calculated from the obtained I and IZrO2.

[0150] (Average thickness of catalyst layer) The cathode was embedded in epoxy resin and then processed with an Ar ion beam (BIB) to prepare a cross section. The BIB processed cross section was observed with an SEM (Hitachi High-Technologies Corporation S-4800) to obtain a backscattered electron image (magnification: 3000). Based on this backscattered electron image, the average thickness of the catalyst layer was calculated using the image analysis software ImageJ as follows. After filtering with a median filter under the condition of Radius: 3.0 pixels, a binarized image was created using the MaxEntropy method, and image analysis was used to determine the catalyst layer area in a cross section perpendicular to the lamination direction of the catalyst layer. Separately, binarization was performed using the Otus method, holes were filled inside the catalyst layer, edges were extracted, and the length of the interface line segment in the above cross section between the embedding resin and the catalyst layer was calculated. The catalyst layer thickness was then calculated using the following definition formula. Catalyst layer thickness (μm) = Catalyst layer area (μm 2 ) / interface line length (μm) For each cathode, the thickness of the catalyst layer was calculated at three points by the above method, and the average value was taken as the average thickness of the catalyst layer.

[0151] (Confirmation of mixed layer generation) The cathode was cross-sectionally processed and subjected to elemental analysis of the catalyst layer using a scanning transmission electron microscope (HD-2300A manufactured by Hitachi, Ltd.) at an accelerating voltage of 200 kV. Elemental analysis was performed at 10 points, and the average value was calculated. By determining the atomic ratio (oxygen:platinum:zirconium) of the catalyst layer, it was determined whether or not a mixed layer was formed. If it was formed, it was marked as "yes," and if it was not formed, it was marked as "no."

[0152] (cathode overvoltage) The cathode was cut to a size of 2 cm x 2 cm and fixed to a PTFE-coated nickel rod with a nickel screw. A platinum mesh was used as the counter electrode, and the current density was 0.6 A / cm in a 32 wt% sodium hydroxide aqueous solution at 80°C. 2The hydrogen overvoltage was measured. The hydrogen overvoltage was measured by the three-electrode method using a Luggin capillary to eliminate the effects of ohmic loss due to solution resistance. The distance between the tip of the Luggin capillary and the cathode was always fixed at 1 mm. The hydrogen overvoltage measurement device used was a Solartron potentiogalvanostat "1470E System." A silver-silver chloride (Ag / AgCl) electrode was used as the reference electrode for the three-electrode method. Ohmic loss, which could not be completely eliminated using the three-electrode method, was measured using the AC impedance method, and the hydrogen overvoltage was corrected based on the measured ohmic loss. The ohmic loss was measured using a Solartron frequency response analyzer "1255B."

[0153] (double layer capacity) The double layer capacitance of the cathode was calculated by analyzing the Cole-Cole plot, which was a plot of the real and imaginary parts obtained by AC impedance measurement using an impedance measurement device (Solartron frequency characteristic analyzer "1255B"), using equivalent circuit fitting. The potential sweep rate was set to four points: 50, 100, 200, and 400 mV / sec. The potential sweep range was -0.72 to -0.58 V. The current density value at a potential of -0.5 V was read, and the double layer capacitance (F / cm) was calculated using the least squares method from the slopes of the four points. 2 ) was calculated.

[0154] (Reverse power test 1) Using the three-electrode method described above, cyclic voltammetry measurements were performed with a sweep range from -1.25 V vs. Ag / AgCl to +0.2 V vs. Ag / AgCl. The potential sweep rate was 500 mV / sec. One cycle was equivalent to reverse voltage, starting from -1.25 V, passing through +0.2 V, and then reaching -1.25 V again. The overvoltage was measured before the reverse voltage test, and then again after 10 cycles. After another 90 cycles, the overvoltage was measured and used as the overvoltage after 100 cycles. The same procedure was repeated to measure the overvoltage after 100, 500, 1000, 1500, 2000, 2500, 5000, and 10,000 cycles. These results were plotted with the total number of cycles on the horizontal axis and the overvoltage on the vertical axis, and an approximation line was drawn between several plotted points from when the overvoltage started to rise until it stopped rising. The total number of cycles on the approximation line at which the overvoltage reached 150 mV was calculated and used as an index of reverse current resistance. In addition, the overvoltage after 10,000 total cycles was also used as an index of reverse current resistance.

[0155] Example , reference example The evaluation results for the comparative example are shown in Table 1.

[0156] [Table 1-1]

[0157] [Table 1-2]

[0158] Example 2-1 An electrolytic cell for alkaline water electrolysis and a bipolar electrolytic cell were prepared as follows.

[0159] -cathode- A cathode was prepared in the same manner as in Example 4 using a plain weave mesh substrate made of 40 meshes of nickel fine wires with a diameter of 0.15 mm as the conductive substrate. The cathode was cut out to fit the cell area and used in the zero-gap bipolar element of Example 2-1.

[0160] -Partition walls, outer frames- The bipolar element used had a partition wall separating the anode and cathode and an outer frame surrounding the partition wall. All of the materials used for the partition wall and the frame of the bipolar element, which come into contact with the electrolyte, were nickel.

[0161] -anode- The anode was made by using a nickel expand substrate that had been subjected to a blasting treatment in advance, and spraying nickel oxide granules onto both sides of the conductive substrate by plasma spraying.

[0162] -Conductive elastic body- The conductive elastic body was made by weaving nickel wire with a diameter of 0.15 mm and corrugating it to a wave height of 5 mm. Its thickness was 5 mm, and its repulsive force at 50% compression deformation was 150 g / cm. 2 The mesh size was about 5 mesh.

[0163] -diaphragm- Zirconium oxide (trade name "EP Zirconium Oxide," manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) and N-methyl-2-pyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd.) were placed in a ball mill pot containing SUS balls with a particle size of 0.5 mm. The mixture was stirred at 70 rpm for 3 hours to disperse the mixture, yielding a mixture. The resulting mixture was filtered through a stainless steel sieve (30 mesh) to separate the balls from the mixture. Polysulfone ("Udel" (registered trademark), manufactured by Solvay Advanced Polymers) and polyvinylpyrrolidone (weight average molecular weight (Mw) 900,000, manufactured by Wako Pure Chemical Industries, Ltd.) were added to the mixture from which the balls had been separated, and the mixture was stirred and dissolved for 12 hours using a Three-One motor to obtain a coating solution with the following composition. Polysulfone: 15 parts by mass Polyvinylpyrrolidone: 6 parts by mass N-methyl-2-pyrrolidone: 70 parts by mass Zirconium oxide: 45 parts by mass The above coating solution was applied to both surfaces of a polyphenylene sulfide mesh substrate (manufactured by Kureha Corporation, film thickness 280 μm, mesh size 358 μm, fiber diameter 150 μm) using a comma coater to a coating thickness of 150 μm on each side. Immediately after coating, the substrate coated with the coating solution was exposed to steam from a coagulation bath containing a 30°C pure water / isopropanol mixture (manufactured by Wako Pure Chemical Industries, Ltd., pure water / isopropanol = 50 / 50 (v / v)). Immediately thereafter, the substrate coated with the coating solution was immersed in the coagulation bath. Then, a coating film was formed on the surface of the substrate by coagulating the polysulfone. The coating film was then thoroughly washed with pure water to obtain a porous membrane. The average pore size of this porous membrane was 0.3 μm in terms of water permeability at 90°C. The thickness was 580 μm. The porosity was 43%. The mode diameter of ZrO2 was 5.0 μm. The ratio of the mode diameter of the inorganic particles to the average pore size of the porous membrane (mode diameter / average pore size) was 2.6.

[0164] -gasket- The gasket used was a square with a thickness of 4.0 mm, a width of 18 mm, and an inner dimension of 504 mm square. It had an opening on the inside that was the same dimensions as the electrode chamber in a plan view, and a slit structure for inserting and holding a diaphragm. The slit structure had a 0.4 mm gap in the center of the thickness direction of the inner wall of the opening, for inserting and holding a diaphragm. This gasket was made of EPDM rubber, and had a tensile stress of 4.0 MPa at 100% deformation.

[0165] -Zero-gap type multi-pole element- The external header type zero gap cell unit 60 (not shown) was a rectangle measuring 540 mm x 620 mm, and the area of ​​the current-carrying surfaces of the anode 2a and cathode 2c was 500 mm x 500 mm. The cathode side of the zero gap bipolar element 60 was composed of a laminate of the cathode 2c, conductive elastic body 2e, and cathode current collector 2r, connected to the partition wall 1 via the cathode rib 6, and provided with a cathode chamber 5c through which the electrolyte flows. The anode side was composed of the anode 2a connected to the partition wall 1 via the anode rib 6, and provided with an anode chamber 5a through which the electrolyte flows. The depth of the anode chamber 5a (anode chamber depth, the distance between the partition wall and the anode) was 25 mm, and the depth of the cathode chamber 5c (cathode chamber depth, the distance between the partition wall and the cathode current collector) was 25 mm, and they were made of nickel. The thickness of the nickel partition wall 1 to which the nickel anode rib 6, which was 25 mm high and 1.5 mm thick, and the nickel cathode rib 6, which was 25 mm high and 1.5 mm thick, was attached by welding, was 2 mm. A nickel expand base material that had been pre-blasted was used as the cathode current collector 2r. The base material had a thickness of 1 mm and an aperture ratio of 54%. A conductive elastic body 2e was fixed onto the cathode current collector 2r by spot welding. By stacking this zero-gap type bipolar element 60 via a gasket that holds the diaphragm 4, a zero-gap structure Z in which the anode 2a and cathode 2c are pressed against the diaphragm 4 can be formed.

[0166] (Comparative Example 2-1) A zero-gap type bipolar element was produced in the same manner as in Example 2-1, except that a cathode produced in the same manner as in Comparative Example 8 was used.

[0167] (Comparative Example 2-2) A zero-gap type bipolar element was produced in the same manner as in Example 2-1, except that a cathode produced in the same manner as in Comparative Example 10 was used.

[0168] (Reverse power test 2) A bipolar electrolytic cell 50 was fabricated by stacking the electrodes in the order shown in FIG. The following elements were stacked in this order: an anode terminal cell element 51a using the anode 2a of Example 2-1, the diaphragm 4 described above, a portion where two pairs of zero gap bipolar elements of Example 2-1 are overlapped with the diaphragm 4 sandwiched between them, a bipolar element including the cathode of Example 2-1 and the anode of Comparative Example 2-1, the diaphragm 4 described above, a portion where two pairs of zero gap bipolar elements of Comparative Example 2-1 are overlapped with the diaphragm 4 sandwiched between them, the diaphragm 4 described above, a bipolar element including the cathode of Comparative Example 2-1 and the anode of Comparative Example 2-2, the diaphragm 4 described above, a portion where two pairs of zero gap bipolar elements of Comparative Example 2-2 are overlapped with the diaphragm 4 sandwiched between them, the diaphragm 4 described above, and a cathode terminal cell element 51c using the cathode of Comparative Example 2-2. An electrolysis device 70 was produced using the bipolar electrolytic cell 50 shown in FIG. 2 including four electrolytic cells (zero gap structure) in which the diaphragm 4 described above was in contact with the anode described above and the cathode of Example 2-1, four electrolytic cells (zero gap structure) in which the diaphragm 4 described above was in contact with the anode described above and the cathode of Comparative Example 2-1, and four electrolytic cells (zero gap structure) in which the diaphragm 4 described above was in contact with the anode described above and the cathode of Comparative Example 2-2. 1, the electrolysis device 70 includes a bipolar electrolytic cell 50, a liquid feed pump 71 for circulating the electrolyte, and a gas-liquid separation tank 72 for separating the electrolyte from hydrogen and / or oxygen. The gas-liquid separation tank 72 and the bipolar electrolytic cell 50 are filled with an electrolyte that is a 30% KOH aqueous solution. The liquid feed pump 71 circulates the electrolyte through the anode chamber 5a of the bipolar electrolytic cell 50, the gas-liquid separation tank 72 for the anode, and the anode chamber 5a, and also through the cathode chamber 5c of the bipolar electrolytic cell 50, the gas-liquid separation tank 72 for the cathode, and the cathode chamber 5c. The temperature was adjusted to 90°C. In the electrolysis device 70, the gas separated in the gas-liquid separation tank 72 is recovered through a pressure gauge 78, a pressure control valve 80, an oxygen concentration meter 75, or a hydrogen concentration meter 76. Electric power can be controlled by a rectifier 74. A flow meter 77 and a heat exchanger 79 are provided in the flow path of the circulating electrolyte. The arrows in Fig. 1 indicate the flow directions of the circulating liquid (electrolyte) and gas. The circulation flow path used SGP carbon steel piping with a Teflon (registered trademark) lining on the inner surface for the electrolyte contact part, and 20A piping was used. The gas-liquid separation tank 72 had a height of 1400 mm and a volume of 1 m 3 The following was used. The gas-liquid separation tank 72 is 1400 mm high and has a volume of 1 m 3 The following items were used. The liquid volume of each gas-liquid separation tank 72 was set to about 50% of the design volume. In an external header type electrolytic cell (not shown), an electrolysis frame that serves as the housing of the bipolar element is provided with four external pipes (anode inlet header 10ai, cathode inlet header 10ci, anode outlet header 10ao, and cathode outlet header 10co) for circulating the electrolyte. Each of these external pipes is connected to each electrode chamber of the electrolytic cell by an external hose. This piping structure is called the external header structure. The external header piping is divided into a cathode side external header piping and an anode side external header piping. Therefore, within each element, the electrolyte enters the cathode chamber 5c from the cathode inlet header 10ci via an external hose, and then flows from the cathode chamber 5c to the cathode outlet header 10co via an external hose. Similarly, on the anode side, the electrolyte enters the anode chamber 5a from the anode inlet header 10ai via an external hose, and then flows from the anode chamber 5a to the anode outlet header 10ao via an external hose. Because the inlet header of the external header is located below the electrolysis frame and the outlet header is located above the electrolysis frame, the electrolyte flows from bottom to top. It also rises in a direction approximately perpendicular to the electrode surface. A thermocouple is installed in the external hose of each cell, allowing the temperature difference before and after passing through the element to be measured. In this example, there are nine anode chambers 5a and nine cathode chambers 5c, and the structure is such that the electrolyte flows from the inlet header to the outlet header in each of the nine chambers. In the cathode chamber 5c, hydrogen gas is generated by electrolysis, and in the anode chamber 5a, oxygen gas is generated, so that in the cathode outlet header 10co, a mixed-phase flow of electrolyte and hydrogen gas is formed, and in the anode outlet header 10ao, a mixed-phase flow of electrolyte and oxygen gas is formed. Electricity was applied from the rectifier 74 to the bipolar electrolytic cell 50 with respect to the areas of the cathode and anode under the conditions of Electrolysis Test 1 described below. The pressure inside the cell after the start of energization was measured with a pressure gauge 78, and was adjusted so that the cathode side pressure was 50 kPa and the oxygen side pressure was 49 kPa. The pressure was adjusted using a control valve 80 installed downstream of the pressure gauge 78. In the electrolysis device 70, the gas separated in the gas-liquid separation tank 72 is recovered through a pressure gauge 78, a pressure control valve 80, an oxygen concentration meter 75, or a hydrogen concentration meter 76. Furthermore, the power can be controlled by a rectifier 74. Furthermore, a flow meter 77 and a heat exchanger 79 are provided in the flow path of the circulating electrolyte. The electrolysis apparatus for alkaline water electrolysis was produced using a rectifier, an oxygen concentration meter, a hydrogen concentration meter, a pressure gauge, a liquid feed pump, a gas-liquid separation tank, a water supply device, and the like, all of which are commonly used in the relevant technical field.

[0169] -Electrolysis test 1- Using the electrolysis device 70, a current density of 6 kA / m 2 After electrolysis, the positive current was applied continuously for 11 hours to achieve a value of 6 kA / m. After electrolysis, the electrolysis was stopped. 2 The positive current was applied for 11 hours. One cycle of positive current and one cycle of stop was defined as one cycle of current application, and 1500 cycles of current application were performed. The voltage versus voltage of each cell of Example 2-1, Comparative Example 2-1, and Comparative Example 2-2 was monitored, and the transition of the voltage versus voltage was recorded. Of these, the cell including the anode terminal element 51a and the cell including the cathode terminal cell element 51c were excluded because reverse current was unlikely to occur in these cells. The cell voltage after 1500 cycles was compared in Table 2 by taking the average value (V) of three cells for each of Example 2-1, Comparative Example 2-1, and Comparative Example 2-2.

[0170] [Table 2]

[0171] As shown in Table 2, in Example 2-1, the average overvoltage of the three cells after 1500 cycles was 1.80 V, which was 30 mV higher than the initial overvoltage, while in Comparative Example 2-1, the overvoltage was 240 mV higher than the initial value. In Comparative Example 2-2, the overvoltage was 260 mV higher than the initial value. This means that even when reverse voltage was applied, Example 2-1 maintained a low overvoltage for a longer period of time than Comparative Examples 2-1 and 2-2. In this test, a three-electrode cell test (Examples 1 to 3) was performed. 9, Reference example 10, Compared to Comparative Examples 1-11 and 1-10, the continuous current flow time per cycle (the elapsed time of electrolytic potential) was longer, resulting in a larger amount of charge accumulated in the anode and a larger amount of reverse current flowing. As a result, deterioration of the cathode due to reverse current cycles occurred more significantly, and the overvoltage tended to increase more quickly. The increase in cell voltage was due to the difference in the degree of reverse current deterioration of each cathode. In other words, it can be concluded that the cathode of Example 2-1 had higher reverse current resistance than Comparative Examples 2-1 and 2-2, which contributed to the long-term low cell voltage. [Industrial Applicability]

[0172] The hydrogen generation cathode of the present invention, in a bipolar electrolytic cell for alkaline water electrolysis having a zero gap structure, suppresses dissolution of the conductive substrate surface due to a reverse current when current flow is stopped, and suppresses peeling at the interface between the conductive substrate and the catalyst layer, thereby preventing an increase in overvoltage and enabling high energy conversion efficiency to be maintained for a long period of time. [Explanation of symbols]

[0173] 2a anode 2c cathode 4 Diaphragm 50 bipolar electrolyzer 51a Anode terminal element 51c Cathode Terminal Element 70 Electrolyzer 71 Liquid transfer pump 72 Gas-liquid separation tank 74 Rectifier 75 Oxygen concentration meter 76 Hydrogen concentration meter 77 Flow meter 78 Pressure Gauge 79 Heat exchanger 80 Pressure control valve

Claims

1. a conductive substrate and a catalyst layer on a surface of the conductive substrate; the catalyst layer contains at least platinum and an insulating oxide containing crystalline zirconium; the catalyst layer includes a zirconium layer containing an insulating oxide containing crystalline zirconium, and a platinum layer containing platinum on a surface of the zirconium layer, or includes a mixed layer containing a mixture of platinum and the insulating oxide containing crystalline zirconium, The conductive substrate contains a metal including nickel, and is either a mesh made by weaving metal wires having a wire diameter of 0.05 to 1.0 mm and a pitch of 20 to 60 meshes, a foam metal having a specific surface area of ​​200 to 6000 m 2 / m 3 , or a punched metal having a pore diameter of 2 to 8 mm, a pitch of 2 to 10 mm, an opening ratio of 20 to 80%, and a thickness of 0.5 to 2 mm; The peak intensity of the X-ray diffracted by the (111) plane of the nickel is INi, and the peak intensity of the X-ray diffracted by the (012) plane of the crystalline zirconium-containing insulating oxide is IZrO ２ When [IZrO ２ / INi] × 100 is 0.1 to 40% A cathode for hydrogen generation, characterized in that:

2. 2. The cathode for hydrogen generation according to claim 1, wherein the zirconium layer has an average thickness of 0.007 μm or more.

3. 3. The cathode for hydrogen generation according to claim 1, wherein the mixed layer has an average thickness of 0.05 μm or more.

4. The cathode for hydrogen generation according to any one of claims 1 to 3, wherein the crystalline zirconium-containing insulating oxide comprises a composite oxide of Zr and an X element (X is at least one element selected from the group consisting of Ce, Y, Ca, and Mg).

5. The weight of the platinum is 2 to 10 g / m ２ The cathode for hydrogen generation according to any one of claims 1 to 4,

6. Double layer capacitance of 0.001 to 0.2 F / cm ２ The cathode for hydrogen generation according to any one of claims 1 to 5,

7. A method for producing a cathode for generating hydrogen, the cathode having a catalytic layer on a conductive substrate, the catalytic layer including: a zirconium layer containing an insulating oxide containing crystalline zirconium; and a platinum layer containing platinum on a surface of the zirconium layer, a coating solution containing at least zirconium is applied to the surface of a conductive substrate, and the coating solution is thermally decomposed at 100 to 700°C in an oxygen-containing atmosphere to form a zirconium layer containing an insulating oxide containing crystalline zirconium; a coating solution containing at least a platinum compound is applied to the surface of the zirconium layer, and the coating solution is thermally decomposed at 100 to 700°C in an oxygen-containing atmosphere to form a platinum layer containing platinum on the surface of the zirconium layer; The weight of the zirconium layer is 0.1 g / m ２ 20.0g / m or more ２ is A method for producing a cathode for hydrogen generation, comprising:

8. A method for producing a cathode for hydrogen generation having a catalytic layer on a conductive substrate, the catalytic layer including a mixed layer containing a mixture of platinum and an insulating oxide containing crystalline zirconium, On the surface of the conductive substrate, ZrO ２ A sol is applied and thermally decomposed at 100 to 700°C in an oxygen-containing atmosphere to form a zirconium layer containing an insulating oxide containing crystalline zirconium; a coating solution containing at least a platinum compound is applied to the surface of the zirconium layer, and the coating solution is thermally decomposed at 100 to 700°C in an oxygen-containing atmosphere to form a mixed layer containing a mixture of platinum and an insulating oxide containing crystalline zirconium; The weight of the crystalline zirconium-containing insulating oxide is 0.1 g / m ２ 18.0g / m or more ２ is A method for producing a cathode for hydrogen generation, comprising:

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