Anode-side separator and water electrolysis device

Abstract

To provide an anode-side separator capable of improving electroconductivity and durability.SOLUTION: The anode-side separator according to the present invention, i.e., an anode-side separator used in a water electrolysis device, comprising a metal substrate made from titanium or stainless steel, and a conductive oxide film including indium tin oxide (ITO) disposed on a surface of the metal substrate, is characterized in that the crystal orientation ratio of a (400) plane of the conductive oxide film is 0.01 or higher.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an anode separator for use in a water electrolysis system and a water electrolysis system including the same. [Background technology]

[0002] In recent years, a water electrolysis device that produces hydrogen by electrolyzing raw material water or the like has been known in which water electrolysis cells using an electrolyte membrane such as a solid polymer electrolyte membrane are stacked. The water electrolysis cell includes, for example, an anode catalyst layer and a cathode catalyst layer provided on one side and the other side of the solid polymer electrolyte membrane, an anode power feeder and an anode-side separator stacked on the anode catalyst layer, and a cathode power feeder and a cathode-side separator stacked on the cathode catalyst layer.

[0003] The anode-side separator must have high conductivity to transmit electricity to the anode catalyst layer. Furthermore, when using a metal substrate for strength reasons, durability becomes an issue due to the susceptibility to corrosion. For this reason, the anode-side separator is configured with a highly conductive and durable conductive layer provided on the surface of the metal substrate. For example, the separator described in Patent Document 1 includes a metal substrate made of titanium or the like and a precious metal layer (conductive layer) made of Au directly laminated on the metal substrate. This separator not only has high conductivity and durability, but also has an adjusted surface roughness of the metal substrate, improving adhesion between the metal substrate and the precious metal layer. Furthermore, the separator described in Patent Document 2 includes a metal substrate made of titanium or stainless steel and a conductive oxide film containing indium tin oxide (ITO) provided on the surface of the metal substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-127707 [Patent Document 2] Japanese Patent Application Publication No. 2023-137149 Summary of the Invention [Problem to be solved by the invention]

[0005] The anode-side separator described in Patent Document 1 has a precious metal layer provided on the surface of a metal substrate, and therefore has excellent durability. However, its high cost makes it difficult to adopt in actual products. To address this issue, the use of a separator having an inexpensive conductive oxide film provided on the surface of a metal substrate, such as the separator described in Patent Document 2, has been considered as an anode-side separator having a conductive layer provided on the surface of a metal substrate. However, such separators are required to have even higher conductivity. Meanwhile, in water electrolysis devices, a high voltage of, for example, about 1.8 V or more is applied to the water electrolysis cell, and therefore separators used in water electrolysis devices are required to have even higher durability.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an anode-side separator that can improve electrical conductivity and durability, and a water electrolysis apparatus including the same. [Means for solving the problem]

[0007] In order to solve the above-described problems, an anode-side separator of the present invention is an anode-side separator for use in a water electrolysis system, comprising: a metal base made of titanium or stainless steel; and a conductive oxide film containing indium tin oxide (ITO) provided on a surface of the metal base, wherein the conductive oxide film has a crystal orientation ratio of 0.01 or more in a (400) plane.

[0008] The water electrolysis apparatus of the present invention is characterized by including the above-described anode-side separator. [Effects of the Invention]

[0009] According to the present invention, the conductivity and durability can be improved. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. 1 is an exploded cross-sectional view schematically illustrating the configuration of a water electrolysis cell, which is a structural unit of a water electrolysis device according to a first embodiment and includes an anode separator according to a first embodiment. [Figure 2] FIG. 2 is an enlarged view of the X portion of FIG. [Figure 3] 1 is a photograph showing the appearance of a sample of a metal substrate of an anode-side separator in Example 1. [Figure 4] 1 is a graph showing the contact resistance before and after a durability test versus the crystal orientation ratio of the (400) plane of the conductive oxide film of the anode-side separator samples of Examples 1 to 17. DETAILED DESCRIPTION OF THE INVENTION

[0011] First, an anode-side separator and a water electrolysis device according to an embodiment will be outlined, taking a first embodiment as an example. Fig. 1 is an exploded cross-sectional view schematically illustrating the configuration of a water electrolysis cell, which is a constituent unit of a water electrolysis device according to the first embodiment, including the anode-side separator according to the first embodiment. Fig. 2 is an enlarged view of the portion X in Fig. 1.

[0012] 1, the water electrolysis apparatus 100 according to the first embodiment is configured by stacking a plurality of water electrolysis cells 20. Each water electrolysis cell 20 is a solid polymer water electrolysis cell including a membrane electrode assembly 10, and an anode separator 12 and a cathode separator 14 according to the first embodiment that sandwich the membrane electrode assembly 10 therebetween.

[0013] The membrane electrode assembly 10 includes a solid polymer electrolyte membrane 2, an anode catalyst layer 4a and a cathode catalyst layer 4c provided on one main surface 2a and the other main surface 2c of the solid polymer electrolyte membrane 2, an anode current collector 6a stacked on the main surface 4aa of the anode catalyst layer 4a, and a cathode current collector 6c stacked on the main surface 4cc of the cathode catalyst layer 4c. An anode separator 12 is stacked on the main surface 6aa of the anode current collector 6a, and a cathode separator 14 is stacked on the main surface 6cc of the cathode current collector 6c.

[0014] 1 and 2, the anode-side separator 12 includes a metal substrate 8 made of pure titanium and a conductive oxide film 9 containing indium tin oxide (ITO) provided on the entire surface 8s of the metal substrate 8. The conductive oxide film 9 has a crystal orientation ratio of 0.13 or more in the (400) plane. In the anode-side separator 12, fluid passage grooves 8g are provided on the main surface 8a of the metal substrate 8 facing the solid polymer electrolyte membrane 2, thereby providing fluid passages 12p, and a water inlet 12f and a water outlet 12d communicating with the fluid passages 12p are also provided.

[0015] The cathode-side separator 14 includes a metal substrate 16 made of titanium, stainless steel, or aluminum. In the cathode-side separator 14, fluid passage grooves 16g are provided on a main surface 16a of the metal substrate 16 facing the solid polymer electrolyte membrane 2, thereby providing fluid passages 14p, and a hydrogen outlet 14d is provided in communication with the fluid passages 14p.

[0016] The anode-side separator 12 and the cathode-side separator 14 transmit electricity to the anode catalyst layer 4a and the cathode catalyst layer 4c via the anode power supply 6a and the cathode power supply 6c, respectively, and also electrically connect to adjacent water electrolysis cells (not shown). In the water electrolysis device 100, multiple water electrolysis cells 20 are stacked in the opposing direction of the anode-side separator 12 and the cathode-side separator 14, and are clamped from both sides in the stacking direction by end plates (not shown).

[0017] When using such a water electrolysis apparatus 100 to produce hydrogen gas by electrolyzing raw water, first, raw water is supplied to the fluid passage 12p from the water supply port 12f of the anode-side separator 12. At the same time, electricity is transmitted to the anode catalyst layer 4a and the cathode catalyst layer 4c by the anode-side separator 12 and the cathode-side separator 14 via the anode power supply 6a and the cathode power supply 6c, respectively. As a result, the raw water is electrolyzed in the anode catalyst layer 4a, generating hydrogen ions (H +), electrons, and oxygen gas (O2) are produced. Next, due to the potential difference between the anode catalyst layer 4a and the cathode catalyst layer 4c, the hydrogen ions permeate the solid polymer electrolyte membrane 2, which is a cation-permeable membrane, and move from the anode catalyst layer 4a side to the cathode catalyst layer 4c side. The hydrogen ions then receive electrons from the cathode catalyst layer 4c and are molecularized, producing hydrogen gas (H2) in the fluid passages 14p of the cathode-side separator 14. The hydrogen gas is extracted from the hydrogen outlet 14d. Meanwhile, the oxygen gas obtained in the fluid passages 12p of the anode-side separator 12 is discharged from the drain outlet 12d together with most of the raw water.

[0018] The effects of the anode-side separator 12 and water electrolysis device 100 according to the first embodiment will be described below. Here, we will explain the problems of a water electrolysis device using an anode-side separator, in which a conductive oxide film containing indium tin oxide is provided on the surface of a metal substrate made of a general-purpose metal other than titanium or stainless steel (e.g., aluminum) instead of the anode-side separator 12 according to the first embodiment, as in the prior art. When an anode-side separator having a conductive oxide film provided on the surface of a metal substrate is used in a water electrolysis device, the conductive oxide film is generally porous. As a result, raw water supplied to the fluid passage penetrates the conductive oxide film, and the conductive oxide film and the metal substrate, which contain different metals, come into contact in the raw water. This forms a corrosion cell between the conductive oxide film and the metal substrate and the raw water, causing current to flow and bimetallic corrosion. Furthermore, when raw water is electrolyzed in a water electrolysis device, a high voltage of, for example, about 1.8 V is typically applied to the constituent water electrolysis cells, exposing the anode-side separator to a high-voltage environment. In such a situation, when an anode-side separator is used in which a general-purpose metal other than titanium or stainless steel is used as the metal substrate, corrosion of the metal substrate due to galvanic corrosion is accelerated because general-purpose metals other than titanium and stainless steel do not have sufficient corrosion resistance, and the durability of the anode-side separator becomes an issue.

[0019] In contrast, the pure titanium used for the metal substrate 8 in the anode-side separator 12 according to the first embodiment has significantly higher corrosion resistance than general-purpose metals other than titanium and stainless steel. Therefore, in the water electrolysis apparatus 100 according to the first embodiment, the conductive oxide film 9 and the metal substrate 8 containing different metals come into contact in the raw water. Even when the anode-side separator 12 is exposed to a high-voltage environment, for example, when a high voltage of approximately 1.8 V is applied to the water electrolysis cell, corrosion of the metal substrate 8 due to galvanic corrosion can be suppressed. Furthermore, in the anode-side separator 12 according to the first embodiment, the conductive oxide film 9 provided as a conductive layer on the surface 8s of the metal substrate 8 contains indium tin oxide, which is less expensive than precious metals such as Au contained in precious metal layers provided as conductive layers on the surfaces of metal substrates in separators of the prior art. Therefore, the anode-side separator 12 can be manufactured at a lower cost than separators of the prior art.

[0020] Furthermore, a conductive oxide film containing indium tin oxide, such as the conductive oxide film 9 included in the anode-side separator 12 according to the first embodiment, is expected to exhibit high conductivity among conductive oxide films. The conductivity and durability of a conductive oxide film containing indium tin oxide increase as the crystal orientation ratio of the (400) plane of the conductive oxide film increases, resulting in a higher density of the conductive oxide film. In the anode-side separator 12, the crystal orientation ratio of the (400) plane of the conductive oxide film 9 is 0.01 or greater, thereby improving the conductivity and durability of the conductive oxide film 9 compared to other conductive oxide films containing indium tin oxide. Furthermore, the increased durability of the conductive oxide film 9 suppresses the progression of corrosion reactions in the metal substrate 8. This improves the conductivity and durability of the anode-side separator 12. This improves the electrolysis performance of the water electrolysis device 100 and the durability of the water electrolysis device 100. Furthermore, since the crystal orientation ratio of the (400) plane of the conductive oxide film 9 is 0.13 or more, the conductivity and durability of the conductive oxide film 9 are remarkably high, especially among conductive oxide films containing indium tin oxide. This allows the conductivity and durability of the anode-side separator 12 to be sufficiently improved. As a result, the electrolysis performance of the water electrolysis device 100 can be sufficiently improved, and the durability of the water electrolysis device 100 can be sufficiently improved.

[0021] Next, the configurations of the anode separator and water electrolysis apparatus according to the embodiment, and the method for producing hydrogen gas according to the embodiment will be described in detail.

[0022] 1. Anode side separator The anode separator according to the embodiment is an anode separator for use in a water electrolysis system, and includes a metal substrate made of titanium or stainless steel and a conductive oxide film containing indium tin oxide (ITO) provided on the surface of the metal substrate, the conductive oxide film having a (400) crystal orientation ratio of 0.01 or more. Here, the "surface of the metal substrate" refers to the outer surface of the metal substrate, and may be one or the other main surface of the metal substrate. The metal substrate, conductive oxide film, and other components of the anode separator are described in detail below.

[0023] (1) Metal base material The titanium used in the metal substrate is not particularly limited, but examples thereof include pure titanium and titanium alloys. The pure titanium is not particularly limited, but examples thereof include those specified in JIS H 4600:2012. The titanium alloy is not particularly limited, but examples thereof include Ti-Al. Of the titanium alloys, pure titanium is preferable because it has particularly high corrosion resistance. The stainless steel used in the metal substrate is, for example, austenitic stainless steel such as SUS304.

[0024] The shape of the metal substrate is not particularly limited as long as it is a shape of a typical metal substrate constituting an anode-side separator used in a typical water electrolysis apparatus, and may be a shape in which grooves for fluid passages of a separator are provided in the metal substrate. For example, when the water electrolysis apparatus includes a solid polymer water electrolysis cell, examples of shapes in which grooves for fluid passages are provided in the metal substrate include a shape in which grooves for fluid passages are provided on the main surface (membrane-forming surface) of the metal substrate facing the solid polymer electrolyte membrane, as in the first embodiment, and a shape in which a flow path portion in which grooves for fluid passages are provided on the main surface (membrane-forming surface) of the metal substrate and a flat portion in which no grooves are provided on the main surface. The metal substrate may also be a flat plate shape in which no grooves for fluid passages are provided in the metal substrate. When the metal substrate has a flat plate shape, it constitutes, for example, a flat-type separator with separate fluid passages. The surface roughness Rz of the metal substrate is, for example, in the range of 0.05 μm to 0.8 μm, preferably 0.1 μm or more, and particularly preferably 0.3 μm or more. The thickness of the metal substrate is not particularly limited and can be set according to the material of the metal substrate, taking into consideration strength, processing, etc., and is, for example, within the range of 0.08 mm to 1 mm.

[0025] (2) Conductive oxide film The conductive oxide film is not particularly limited as long as it contains indium tin oxide (ITO) provided on the surface of the metal substrate. When the water electrolysis apparatus is a water electrolysis apparatus including a solid polymer water electrolysis cell, the conductive oxide film is preferably provided at least on the main surface (film formation surface) of the metal substrate facing the solid polymer electrolyte membrane, as in the first embodiment, or may be provided on the entire surface of the metal substrate. The crystal orientation ratio of the (400) plane of the conductive oxide film is not particularly limited as long as it is 0.01 or more, but is preferably 0.13 or more. This is because the conductivity and durability of the conductive oxide film are significantly improved.

[0026] Here, a method for determining the crystal orientation ratio of the (400) plane of a conductive oxide film will be described. To determine the crystal orientation ratio, first, an X-ray diffraction spectrum is measured for the conductive oxide film using, for example, powder X-ray diffraction (XRD). Next, in the X-ray diffraction spectrum, the area of ​​the diffraction line portion (peak portion) due to each of four crystal planes including the (222), (400), (431), and (440) planes of the conductive oxide film is calculated by integration. Then, the area of ​​the diffraction line portion due to each of the four crystal planes is calculated as the crystal orientation amount Q of the four crystal planes. n (n = 1 to 4). Next, the crystal orientation ratio R of the four crystal planes is calculated. n (n=1 to 4) is calculated by the following formula (1): From this, the crystal orientation ratio R2 is determined as the crystal orientation ratio of the (400) plane.

[0027] R n =Q n / (Total of Q1 to Q4) (1) (In formula (1), n ​​is 1 to 4, and R n (n=1 to 4) indicates the crystal orientation ratio of the (222), (400), (431), and (440) planes, respectively, and Q n (n=1 to 4) indicates the crystal orientation of the (222), (400), (431), and (440) planes, respectively.)

[0028] The thickness of the conductive oxide film is not particularly limited, but is, for example, in the range of 0.05 μm to 0.8 μm, and preferably 0.3 μm or more. A thickness of 0.05 μm or more enables the conductive oxide film to be uniformly formed. Furthermore, a thickness of 0.3 μm or more ensures sufficient durability of the anode separator even when the surface of the metal substrate becomes rough after undergoing a pressing process. On the other hand, a thickness of 0.8 μm or less prevents the conductive oxide film from peeling off from the metal substrate due to residual stress.

[0029] (3) Manufacturing method of anode side separator The method for producing the anode-side separator is not particularly limited, but examples thereof include a method of preparing a metal substrate made of titanium or stainless steel and forming a conductive oxide film containing indium tin oxide (ITO) on the surface of the metal substrate by a PVD method or the like. Examples of methods for forming the conductive oxide film include PVD methods such as ion plating, vacuum deposition, and sputtering, among which ion plating is preferred, and ion plating using a pressure gradient plasma gun is particularly preferred.

[0030] The method for adjusting the crystal orientation ratio of the (400) plane of a conductive oxide film to 0.01 or more or 0.13 or more (hereinafter, sometimes referred to as a "method for adjusting the crystal orientation ratio of a conductive oxide film") is not particularly limited, but includes, for example, a method of adjusting the O2 (oxygen) partial pressure in the atmosphere in a chamber when forming a conductive oxide film by a PVD method. Another method for adjusting the crystal orientation ratio of a conductive oxide film includes a method of adjusting the component ratio of a target (solid material) when forming a conductive oxide film by a PVD method. Another method for adjusting the crystal orientation ratio of a conductive oxide film includes a method of heat-treating the conductive oxide film after its formation. Examples of the heat treatment method include a method of heat-treating the conductive oxide film at a predetermined furnace temperature for a predetermined treatment time using an atmospheric furnace, an argon furnace, or the like. Another method for adjusting the crystal orientation ratio of a conductive oxide film includes a method of pre-heating the metal substrate so that the temperature of the metal substrate (the temperature of the surface of the metal substrate) when forming the conductive oxide film is a predetermined value. Another example of a method for adjusting the crystal orientation ratio of a conductive oxide film is to adjust the energy used to evaporate a target (solid material) to a predetermined value when forming a conductive oxide film by PVD. Another example is to form an intermediate film, which is advantageous for crystallization of the conductive oxide film, on the surface of a metal substrate before forming the conductive oxide film, and then form the conductive oxide film on the surface of the intermediate film. These methods for adjusting the crystal orientation ratio of a conductive oxide film can transition the indium tin oxide crystals of the conductive oxide film from crystals dominated by the (222) plane to crystals dominated by the (400) plane, thereby adjusting the crystal orientation ratio of the (400) plane of the conductive oxide film to 0.01 or more or 0.13 or more.

[0031] 2.Water electrolysis device The water electrolysis device according to the embodiment is not particularly limited as long as it includes the anode-side separator according to the embodiment. For example, a water electrolysis device including a solid polymer water electrolysis cell using a solid polymer electrolyte membrane, such as the water electrolysis device according to the first embodiment, is preferred.

[0032] An example of a solid polymer water electrolysis cell is one that includes a membrane electrode assembly, and an anode-side separator and a cathode-side separator that sandwich the membrane electrode assembly, as in the water electrolysis cell according to the first embodiment. An example of such a solid polymer water electrolysis cell is one in which the membrane electrode assembly includes a solid polymer electrolyte membrane, an anode catalyst layer and a cathode catalyst layer provided on one and the other main surfaces of the solid polymer electrolyte membrane, respectively, an anode current feeder stacked on the main surface of the anode catalyst layer, and a cathode current feeder stacked on the main surface of the cathode catalyst layer, wherein the anode-side separator is stacked on the main surface of the anode current feeder, and the cathode-side separator is stacked on the main surface of the cathode current feeder.

[0033] The solid polymer electrolyte membrane prevents the flow of electrons and gases, while also preventing the flow of hydrogen ions (H + ) from the anode catalyst layer side to the cathode catalyst layer side. The solid polymer electrolyte membrane is not particularly limited, but is made of, for example, a polymer electrolyte resin, which is a solid polymer material such as perfluorosulfonic acid (PFSA) ionomer, and is an ion exchange membrane with an ion-conductive polymer membrane as the electrolyte.

[0034] The anode catalyst layer has the function of generating hydrogen ions, electrons, and oxygen gas from raw water. The anode catalyst layer is, for example, composed of a catalyst and an ionomer, and is formed by coating the catalyst with the ionomer. The catalyst is, for example, not limited to, a supported catalyst in which a platinum group metal such as platinum or an alloy thereof is supported on a support particle. The support particle is, for example, not limited to, a carbon support particle such as carbon black. The ionomer is, for example, composed of a polymer electrolyte resin, which is a solid polymer material such as a fluororesin of the same nature as a solid polymer electrolyte membrane, and has proton conductivity due to its ion exchange groups. Unlike the anode catalyst layer, the cathode catalyst layer has the function of converting hydrogen ions and electrons into hydrogen gas (H2). The cathode catalyst layer is, for example, not limited to, a catalyst and an ionomer, and is formed by coating the catalyst with the ionomer. The catalyst and ionomer are the same as those of the anode catalyst layer.

[0035] The anode and cathode power supply members are not particularly limited as long as they are conductive materials with gas permeability, but may be made of, for example, a conductive porous material, specifically, a porous metal material such as a sintered body of titanium powder, or a porous fiber material such as carbon fiber or graphite fiber.

[0036] The anode-side separator is as described above in the section "1. Anode-side separator." Examples of the cathode-side separator include a metal substrate made of titanium, stainless steel, aluminum, or the like. The shape of the metal substrate of the cathode-side separator is not particularly limited as long as it is a common shape. The thickness of the metal substrate of the cathode-side separator is not particularly limited and can be set according to the material of the metal substrate, taking into consideration strength, processing, and the like.

[0037] 3. Hydrogen gas production method The method for producing hydrogen gas according to the embodiment is not particularly limited as long as it is a method for producing hydrogen gas by electrolyzing raw material water or the like using the water electrolysis device according to the embodiment, but may be, for example, a method using pure water as a raw material. [Example]

[0038] Hereinafter, the anode separator and the water electrolysis device according to the embodiment will be described in more detail with reference to examples.

[0039] [Example 1] First, a metal substrate (thickness: 100 μm) made of pure titanium (pure Ti) was prepared as an actual component used in a separator for a practical product. The metal substrate had a flow path portion with grooves for fluid passages on the main surface (film-forming surface) and a flat portion without grooves on the main surface. Next, a 5 cm × 6 cm area including the flow path portion and the flat portion was cut from the metal substrate of the practical component to obtain a metal substrate sample. Figure 3 is a photograph showing the appearance of a metal substrate sample for the anode-side separator of Example 1. Next, the natural oxide film and other elements on the main surface of the sample metal substrate were removed in advance by reverse sputtering. Next, a conductive oxide film containing ITO was formed on the main surface of the sample metal substrate by ion plating using a specified ion plating device under the following film-forming conditions. This resulted in the production of an anode-side separator sample.

[0040] (Film formation conditions) Target: Composite containing In2O3 (95 wt%) and SnO2 (5 wt%) Metal substrate temperature: 300℃ Gas introduced into the chamber: Ar (argon) only O2 partial pressure ratio of the atmosphere in the chamber (O2 partial pressure / Ar partial pressure): 0 Conductive oxide film thickness: 100 nm

[0041] [Example 2] An anode separator sample was prepared in the same manner as in Example 1, except that the conductive oxide film was formed under conditions in which the weight ratio of SnO2 in the target was 7.5 wt % and the weight ratio of In2O3 was 92.5 wt %.

[0042] [Example 3] An anode-side separator sample was prepared in the same manner as in Example 1, except that the conductive oxide film was formed under conditions in which the weight ratio of SnO2 in the target was 10 wt % and the weight ratio of In2O3 was 90 wt %.

[0043] [Example 4] An anode-side separator sample was prepared in the same manner as in Example 1, except that the conductive oxide film was formed under the following conditions: the weight ratio of SnO in the target was 15 wt %, the weight ratio of InO was 85 wt %, the gases introduced into the chamber were Ar and O, and the O partial pressure ratio of the atmosphere in the chamber was 1 / 3.

[0044] [Example 5] An anode-side separator sample was prepared in the same manner as in Example 1, except that the conductive oxide film was formed under conditions in which the weight ratio of SnO2 in the target was 15 wt % and the weight ratio of In2O3 was 85 wt %.

[0045] [Example 6] A metal substrate (natural oxide film thickness: approximately 50 nm) made of pure titanium (pure Ti) was prepared as the metal substrate for the actual part, and a metal substrate sample was obtained from the metal substrate for the actual part. Next, the natural oxide film and other films on the main surface of the metal substrate of the sample were removed in advance by reverse sputtering, and then a conductive oxide film was formed under the film formation conditions of Ar and O2 introduced into the chamber, with the O2 partial pressure ratio of the atmosphere in the chamber set to 1 / 3. Except for the above points, a sample anode-side separator was prepared in the same manner as in Example 1.

[0046] [Example 7] An anode-side separator sample was prepared in the same manner as in Example 6, except that the conductive oxide film was formed under the conditions that only Ar was introduced into the chamber and the O2 partial pressure ratio of the atmosphere in the chamber was set to 0.

[0047] [Example 8] An anode-side separator sample was prepared in the same manner as in Example 6, except that the conductive oxide film was formed under conditions in which the weight ratio of SnO2 in the target was 7.5 wt % and the weight ratio of In2O3 was 92.5 wt %.

[0048] [Example 9] An anode-side separator sample was prepared in the same manner as in Example 8, except that the conductive oxide film was formed under the conditions that only Ar was introduced into the chamber and the O2 partial pressure ratio of the atmosphere in the chamber was set to 0.

[0049] [Example 10] An anode-side separator sample was prepared in the same manner as in Example 6, except that the conductive oxide film was formed under conditions in which the weight ratio of SnO2 in the target was 10 wt % and the weight ratio of In2O3 was 90 wt %.

[0050] [Example 11] An anode-side separator sample was prepared in the same manner as in Example 10, except that the conductive oxide film was formed under the conditions that only Ar was introduced into the chamber and the O2 partial pressure ratio of the atmosphere in the chamber was set to 0.

[0051] [Example 12] An anode-side separator sample was prepared in the same manner as in Example 6, except that the conductive oxide film was formed under conditions in which the weight ratio of SnO2 in the target was 15 wt % and the weight ratio of In2O3 was 85 wt %.

[0052] [Example 13] An anode-side separator sample was prepared in the same manner as in Example 12, except that the conductive oxide film was formed under the conditions that only Ar was introduced into the chamber and the O2 partial pressure ratio of the atmosphere in the chamber was set to 0.

[0053] [Example 14] A metal substrate made of stainless steel (SUS304) was prepared as the metal substrate for the actual part, and a sample of the anode side separator was produced in the same manner as in Example 1, except that a metal substrate sample was obtained from the metal substrate for the actual part.

[0054] [Example 15] An anode-side separator sample was prepared in the same manner as in Example 14, except that the conductive oxide film was formed under conditions in which the weight ratio of SnO2 in the target was 7.5 wt % and the weight ratio of In2O3 was 92.5 wt %.

[0055] [Example 16] An anode-side separator sample was prepared in the same manner as in Example 14, except that the conductive oxide film was formed under conditions in which the weight ratio of SnO2 in the target was 10 wt % and the weight ratio of In2O3 was 90 wt %.

[0056] [Example 17] An anode-side separator sample was prepared in the same manner as in Example 14, except that the conductive oxide film was formed under conditions in which the weight ratio of SnO2 in the target was 15 wt % and the weight ratio of In2O3 was 85 wt %.

[0057] [Evaluation of the crystal orientation of conductive oxide films] The crystal orientation of the conductive oxide film was evaluated for the anode-side separator samples of Examples 1 to 17. First, the X-ray diffraction spectrum was measured for the portion of the conductive oxide film of each sample formed on the flat portion of the metal substrate using powder X-ray diffractometry (XRD). Next, in the X-ray diffraction spectrum, the area of ​​the diffraction line portion (peak portion) due to each of four crystal planes, including the (222), (400), (431), and (440) planes of the conductive oxide film, was calculated by integration. The area of ​​the diffraction line portion due to each of the four crystal planes was then calculated as the crystal orientation amount Q of the four crystal planes. n (n = 1 to 4). Next, the crystal orientation ratio Rn (n=1 to 4) was calculated using the above formula (1). The results are shown in Table 1 below.

[0058] [Evaluation of contact resistance before durability test] For the anode-side separator samples of Examples 1 to 17, the contact resistance [mΩ·cm] before the durability test (initial) was 2 The contact resistance between the sample and the carbon sheet was calculated. The results are shown in Table 1.

[0059] [Evaluation of contact resistance after durability test] For the anode-side separator samples of Examples 1 to 17, the contact resistance [mΩ·cm] after the durability test was 2 The corrosion resistance was measured. A durability test (potential corrosion test) was conducted on each sample in accordance with the Japanese Industrial Standards (JIS Z 2294:2004) for electrochemical high-temperature corrosion testing of metallic materials. Specifically, the sample was immersed in a corrosive solution (dilute sulfuric acid aqueous solution) whose temperature was adjusted to 80°C using temperature-controlled water and whose pH was adjusted to 4 using sulfuric acid. A counter electrode made of a titanium plate and the sample (sample electrode) were electrically connected in this state, creating a potential difference of 2 V between the counter electrode and the sample electrode in a two-electrode system. The test time was 130 hours, causing the sample to corrode. The contact resistance of each sample after the durability test was calculated using the same method as that used before the durability test. The results are shown in Table 1 below.

[0060] [Table 1]

[0061] [Consideration] 4 is a graph showing the contact resistance before and after the durability test versus the crystal orientation ratio of the (400) plane of the conductive oxide film of the anode-side separator samples of Examples 1 to 17. As is clear from Table 1 and FIG. 4 above, in all of the samples of Examples 1 to 17, the crystal orientation ratio of the (400) plane of the conductive oxide film was 0.01 or more, and the contact resistance before the durability test was 10 mΩ cm 2 Furthermore, among the anode-side separator samples of Examples 1 to 17, in the samples in which the crystal orientation ratio of the (400) plane of the conductive oxide film was 0.13 or more, the contact resistance not only before the durability test but also after the durability test was 10 mΩ cm 2 or less, which was within the range of the specification value. Furthermore, from Table 1 above, it was found that in the conductive oxide films of the samples of Examples 1 to 17, by reducing the O2 partial pressure ratio in the atmosphere in the chamber under the film-forming conditions of the manufacturing conditions, the crystal structure of the conductive oxide film tends to shift from a crystal structure dominated by the (222) plane to a crystal structure dominated by the (400) plane.

[0062] Although the embodiments of the anode separator and the water electrolysis apparatus of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various design modifications can be made without departing from the spirit of the present invention as defined in the claims. [Explanation of symbols]

[0063] 100: Water electrolysis device, 20: Water electrolysis cell, 10: Membrane electrode assembly, 12: Anode side separator, 8: Metal substrate, 9: Conductive oxide film, 14: Cathode side separator

Claims

1. An anode-side separator for use in a water electrolysis apparatus, a metal substrate made of titanium or stainless steel; a conductive oxide film containing indium tin oxide (ITO) provided on the surface of the metal substrate; an anode-side separator, wherein the conductive oxide film has a crystal orientation ratio of the (400) plane of 0.01 or more;

2. 2. The anode-side separator according to claim 1, wherein the conductive oxide film has a crystal orientation ratio of the (400) plane of 0.13 or more.

3. A water electrolysis device comprising the anode separator according to claim 1 or 2.

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