Anode-side separator and water electrolysis device

Abstract

To provide an anode side separator capable of improving conductivity.SOLUTION: An anode side separator according to the present invention is an anode side separator used in a water electrolysis apparatus characterized in that it comprises a metal base material made of titanium or stainless steel, a conductive oxide film including indium tin oxide (ITO) provided on the surface of the metal base, and a precious metal film including platinum (Pt) provided on the surface of the conductive oxide film.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an anode-side separator used in a water electrolysis device and a water electrolysis device including the same.

Background Art

[0002] In recent years, as a water electrolysis device for producing hydrogen by electrolyzing raw materials such as water, a device in which water electrolysis cells using an electrolyte membrane such as a solid polymer electrolyte membrane are stacked is known. The water electrolysis cell is provided, for example, with an anode catalyst layer and a cathode catalyst layer on one surface and the other surface of the electrolyte membrane, respectively. An anode current collector and an anode-side separator are stacked on the anode catalyst layer, and a cathode current collector and a cathode-side separator are stacked on the cathode catalyst layer.

[0003] Since the anode-side separator functions to transmit electricity to the anode catalyst layer, high conductivity is required. Further, when a metal base material is used from the viewpoint of strength or the like, corrosion easily occurs in the metal base material, so corrosion resistance becomes a problem. For this reason, the anode-side separator is configured to have a conductive layer with high conductivity and excellent corrosion resistance provided on the surface of the metal base material. For example, the anode-side separator described in Patent Document 1 includes a metal base material made of titanium or the like, and a noble metal layer (conductive layer) made of Au directly laminated on the metal base material, has high conductivity and high corrosion resistance, and the surface roughness of the metal base material is adjusted to improve the adhesion between the metal base material and the noble metal layer. Further, the member constituting the anode described in Patent Document 2 includes an electrode base material (metal base material) made of a metal such as aluminum, and a conductive oxide film (conductive layer) provided on the surface of the electrode base material and forming a nanostructure.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

[0005] The anode separator described in Patent Document 1 has a noble metal layer on the surface of a metal substrate, which gives it excellent corrosion resistance, but it is expensive and difficult to adopt in actual products. To address this, as an anode separator with a conductive layer on the surface of a metal substrate, it is being considered to use a component like the one described in Patent Document 2, which has an inexpensive conductive oxide film on the surface of a metal substrate. On the other hand, in anode separators with a conductive oxide film on the surface of a metal substrate, the contact resistance of the conductive oxide film is not sufficiently low, so improvement in conductivity is required.

[0006] The present invention has been made in view of these points, and its object is to provide an anode-side separator used in a water electrolysis apparatus and a water electrolysis apparatus equipped therewith, which can improve conductivity. [Means for solving the problem]

[0007] To solve the above problems, the anode-side separator of the present invention is an anode-side separator used in a water electrolysis apparatus, characterized by comprising: 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; and a noble metal film containing platinum (Pt) provided on the surface of the conductive oxide film.

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

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

[0010] [Figure 1] This is a schematic exploded cross-sectional view showing the configuration of a water electrolysis cell, which is a constituent unit of the water electrolysis apparatus according to the first embodiment, equipped with an anode-side separator according to the first embodiment. [Figure 2] This is an enlarged view of the X portion in Figure 1. [Modes for carrying out the invention]

[0011] First, the outline of the anode-side separator and water electrolysis apparatus according to the embodiment will be described by illustrating the first embodiment. Figure 1 is a schematic exploded cross-sectional view showing the configuration of a water electrolysis cell, which is a constituent unit of the water electrolysis apparatus according to the first embodiment, equipped with the anode-side separator according to the first embodiment. Figure 2 is an enlarged view of portion X in Figure 1.

[0012] As shown in Figure 1, the water electrolysis apparatus 100 according to the first embodiment is constructed by stacking multiple sets of water electrolysis cells 20. The water electrolysis cell 20 is a solid polymer type water electrolysis cell comprising a membrane electrode assembly 10 and an anode-side separator 12 and a cathode-side separator 14 according to the first embodiment that sandwich the membrane electrode assembly 10.

[0013] The membrane electrode assembly 10 comprises 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 power supply 6a laminated on the main surface 4aa of the anode catalyst layer 4a, and a cathode power supply 6c laminated on the main surface 4cc of the cathode catalyst layer 4c. The anode-side separator 12 is laminated on the main surface 6aa of the anode power supply 6a, and the cathode-side separator 14 is laminated on the main surface 6cc of the cathode power supply 6c.

[0014] As shown in Figures 1 and 2, the anode-side separator 12 comprises a metal substrate 8 made of pure titanium, a conductive oxide film 9 containing indium tin oxide (ITO) provided on the entire surface 8s of the metal substrate 8, and a noble metal film 7 containing platinum (Pt) provided on the entire surface 9s of the conductive oxide film 9. The thickness of the noble metal film 7 is in the range of 3 nm to 5 nm. In the anode-side separator 12, a fluid passage 12p is provided by providing a groove 8g for a fluid passage on the main surface 8a side of the metal substrate 8 facing the solid polymer electrolyte film 2, and a water inlet 12f and a drain outlet 12d communicating with the fluid passage 12p are provided.

[0015] The cathode-side separator 14 comprises a metal substrate 16 made of titanium, stainless steel, or aluminum. In the cathode-side separator 14, a fluid passage 14p is provided by providing a groove 16g for a fluid passage on the main surface 16a side of the metal substrate 16 facing the solid polymer electrolyte membrane 2, and a hydrogen outlet 14d communicating with the fluid passage 14p is provided.

[0016] The anode separator 12 and the cathode separator 14 each 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 function to electrically connect to adjacent water electrolysis cells (not shown). In the water electrolysis apparatus 100, multiple sets of water electrolysis cells 20 are stacked in the direction opposite to the anode separator 12 and the cathode separator 14, and are fastened from both sides in the stacking direction by end plates (not shown).

[0017] When producing hydrogen gas by electrolyzing raw water using such a water electrolysis apparatus 100, first, raw water is supplied from the water inlet 12f of the anode separator 12 to the fluid passage 12p. At the same time, the anode separator 12 and the cathode 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. As a result, the raw water is electrolyzed in the anode catalyst layer 4a, producing hydrogen ions (H +) electrons, and oxygen gas (O 2 ) is generated. Next, hydrogen ions permeate through the solid polymer electrolyte membrane 2, which is a cation-permeable membrane, due to the potential difference between the anode catalyst layer 4a and the cathode catalyst layer 4c, and move from the anode catalyst layer 4a side to the cathode catalyst layer 4c side. Then, by receiving electrons from the cathode catalyst layer 4c and being molecularized, hydrogen ions result in hydrogen gas (H 2 ) being obtained in the fluid passage 14p of the cathode-side separator 14. The hydrogen gas is taken out from the hydrogen outlet 14d. On the other hand, the oxygen gas obtained in the fluid passage 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 the water electrolysis device 100 according to the first embodiment as described above will be described below.

[0019] As in the prior art, in the water electrolysis device 100, instead of the anode-side separator 12 according to the first embodiment, a problem of a water electrolysis device using an anode-side separator provided with a conductive oxide film containing indium tin oxide on the surface of a metal substrate made of a general-purpose metal other than titanium and stainless steel (for example, aluminum, etc.) will be described. In a water electrolysis device, generally when using an anode-side separator provided with a conductive oxide film on the surface of a metal substrate, since the conductive oxide film is a porous body, the raw water supplied to the fluid passage penetrates into the conductive oxide film, and as a result, the conductive oxide film and the metal substrate containing different metals come into contact in the raw water. Thereby, a corrosion cell is formed between the conductive oxide film, the metal substrate, and the raw water, and an electric current flows, causing dissimilar metal contact corrosion. Further, in a water electrolysis device, when electrolyzing raw water, usually, for example, a high voltage of about 1.8 V is applied to the water electrolysis cell of the constituent unit, so the anode-side separator is exposed to a high voltage environment. In such a situation, when using an anode-side separator in which a general-purpose metal other than titanium and stainless steel is used as the metal substrate, since the general-purpose metal other than titanium and stainless steel does not have sufficient corrosion resistance, the corrosion of the metal substrate due to dissimilar metal contact corrosion is promoted, and the corrosion resistance of the anode-side separator becomes a problem.

[0020] In contrast, in the electrolyzer 100 according to the first embodiment, in the anode-side separator 12 according to the first embodiment, since the thickness of the noble metal film 7 is less than 10 nm, the surface 9s of the conductive oxide film 9 is not completely covered by the noble metal film 7, and as a result, the conductive oxide film 9 is exposed in the raw material water, and the conductive oxide film 9 and the metal base material 8 containing different metals come into contact with each other in the raw material water. However, the pure titanium used for the metal base material 8 has significantly higher corrosion resistance than general-purpose metals other than titanium and stainless steel. Therefore, even in a situation where the conductive oxide film 9 and the metal base material 8 come into contact with each other in the raw material water and, for example, a high voltage of about 1.8 V is applied to the electrolytic cell for water electrolysis, and the anode-side separator 12 is exposed to a high-voltage environment, corrosion of the metal base material 8 due to dissimilar metal contact corrosion can be suppressed.

[0021] In addition to this, in the anode-side separator 12 according to the first embodiment, compared with an anode-side separator not provided with the noble metal film 7 on the surface 9s of the conductive oxide film 9, since the surface 12s of the anode-side separator 12 is composed of the surface 7s of the noble metal film 7, the contact resistance of the surface 12s of the anode-side separator 12 can be reduced. Thereby, the conductivity of the anode-side separator 12 can be improved. Therefore, the performance of the electrolyzer 100 according to the first embodiment can be enhanced.

[0022] Furthermore, unlike the anode-side separator 12 according to the first embodiment, in an anode-side separator that does not have a conductive oxide film and has a noble metal film directly provided on the surface of a metal substrate, if the thickness of the noble metal film is less than 10 nm, the surface of the metal substrate may not be completely covered by the noble metal film. For this reason, in a water electrolysis apparatus 100 according to the first embodiment that uses such an anode-side separator instead of the anode-side separator 12 according to the first embodiment, when the raw water is electrolyzed, the surface of the metal substrate is exposed to the raw water, so a passivation film (oxide film) is formed on the exposed portion of the surface of the metal substrate. For this reason, as the water electrolysis apparatus is used, the formation of a passivation film on the exposed portion of the surface of the metal substrate progresses, and the contact resistance of the surface of the anode-side separator increases. Thus, the durability of the anode-side separator becomes a problem. In contrast, in the anode-side separator 12 according to the first embodiment, a noble metal film 7 is provided on the surface 8s of the metal substrate 8 via a conductive oxide film 9. Therefore, even though the thickness of the noble metal film 7 is less than 10 nm, exposure of the surface 8s of the metal substrate 8 to the raw water is suppressed when the raw water is electrolyzed in the water electrolysis apparatus 100 according to the first embodiment. As a result, the increase in contact resistance due to the progression of the formation of a passivation film on the exposed portion of the surface 8s of the metal substrate 8 is suppressed. Thus, the durability of the anode-side separator 12 can be improved, and the durability of the water electrolysis apparatus 100 can be improved.

[0023] On the other hand, unlike the anode-side separator 12 according to the first embodiment, in an anode-side separator that does not have a conductive oxide film and has a noble metal film directly provided on the surface of a metal substrate, if the thickness of the noble metal film is 10 nm or more, even if the surface of the metal substrate is completely covered by the noble metal film, the material cost of platinum used for the noble metal film will be high. In contrast, in the anode-side separator 12 according to the first embodiment, since the thickness of the noble metal film 7 is 5 nm or less, the material cost of platinum used for the noble metal film 7 is low, and even when taking into account the material cost of the conductive oxide film 9, the cost can be reduced.

[0024] In the anode-side separator according to the embodiment, as in the first embodiment, titanium or stainless steel, which have significantly higher corrosion resistance than other general-purpose metals, is used as the metal substrate. Therefore, corrosion of the metal substrate can be suppressed. For this reason, in the water electrolysis apparatus according to the embodiment, by providing the anode-side separator according to the embodiment, corrosion of the metal substrate due to galvanic corrosion can be suppressed. In addition, in the anode-side separator according to the embodiment, as in the first embodiment, the surface of the anode-side separator is composed of the surface of a noble metal film, thereby improving the conductivity of the anode-side separator. This makes it possible to improve the performance of the water electrolysis apparatus according to the embodiment. Furthermore, in the anode-side separator according to the embodiment, if the thickness of the noble metal film is less than 10 nm, durability can be improved compared to an anode-side separator without a conductive oxide film and with a noble metal film thickness of less than 10 nm, as in the first embodiment. Also, if the thickness of the noble metal film is 5 nm or less, the cost can be reduced compared to an anode-side separator without a conductive oxide film and with a noble metal film thickness of 10 nm or more, as in the first embodiment.

[0025] Next, the configuration of the anode-side separator and water electrolysis apparatus according to the embodiment, as well as the hydrogen gas production method according to the embodiment, will be described in detail.

[0026] 1. Anode-side separator The anode-side separator according to this embodiment is an anode-side separator used in a water electrolysis apparatus, comprising: 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; and a noble metal film containing platinum (Pt) provided on the surface of the conductive oxide film. Here, "surface of the metal substrate" means the outer surface of the metal substrate, and may be one main surface of the metal substrate or the other main surface of the metal substrate. The metal substrate, conductive oxide film, noble metal film, and other components of the anode-side separator will be described in detail below.

[0027] (1) Metal base material The titanium used as a metal substrate is not particularly limited, but examples include pure titanium and titanium alloys. Pure titanium is not particularly limited, but examples include those specified in JIS H 4600:2012. Titanium alloys are not particularly limited, but examples include Ti-Al, Ti-Nb, Ti-Ta, Ti-6Al-4V, and Ti-Pd. Among the titanium used as a metal substrate, pure titanium is preferred because it has particularly high corrosion resistance.

[0028] Examples of stainless steel used as a metal substrate include austenitic stainless steel such as SUS304 and SUS316, ferritic stainless steel such as SUS430, and martensitic stainless steel such as SUS420.

[0029] The shape of the metal substrate is not particularly limited, as long as it is a general shape of a metal substrate that constitutes an anode-side separator used in a general water electrolysis apparatus, and may also be a shape in which grooves for the fluid passage of the separator are provided in the metal substrate. If the water electrolysis apparatus is a water electrolysis apparatus that includes a solid polymer type water electrolysis cell, the shape in which grooves for the fluid passage are provided may be, for example, as in the first embodiment, a shape in which grooves for the fluid passage are provided on the main surface side of the metal substrate facing the solid polymer electrolyte membrane. The shape of the metal substrate may also be a flat plate shape in which grooves for the fluid passage are provided in the metal substrate. When the shape of the metal substrate is a flat plate shape, for example, it constitutes a flat type separator with separated fluid passages. The surface roughness Rz of the metal substrate is, for example, in the range of 0.05 μm or more and 0.8 μm or less, and is preferably in the range of 0.1 μm or more, and particularly preferably in the range of 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 and processing, but is, for example, in the range of 0.1 mm to 1 mm.

[0030] (2) Conductive oxide film The conductive oxide film is not particularly limited as long as it contains indium tin oxide (ITO) and is provided on the surface of the metal substrate. If the water electrolysis apparatus is a water electrolysis apparatus that includes a solid polymer type water electrolysis cell, the conductive oxide film is preferably provided on at least the main surface of the metal substrate facing the solid polymer electrolyte film, as in the first embodiment, but it may also be provided on the entire surface of the metal substrate.

[0031] The thickness of the conductive oxide film is not particularly limited, but is, for example, within the range of 0.05 μm to 0.8 μm, and preferably within the range of 0.3 μm or more. This is because a thickness of 0.05 μm or more of the conductive oxide film enables the uniform formation of the conductive oxide film. Furthermore, a thickness of 0.3 μm or more of the conductive oxide film ensures sufficient corrosion resistance of the anode-side separator when the surface of the metal substrate becomes rough after going through the pressing process. On the other hand, a thickness of 0.8 μm or less of the conductive oxide film suppresses the delamination of the conductive oxide film from the metal substrate due to residual stress.

[0032] (3) Precious metal film The precious metal film is not particularly limited as long as it contains platinum (Pt) provided on the surface of the conductive oxide film. Preferably, the thickness of the precious metal film is within the range of less than 10 nm. This is because durability can be improved compared to anode-side separators that do not have a conductive oxide film and have a precious metal film thickness of less than 10 nm. In particular, preferably, the thickness of the precious metal film is within the range of 3 nm to 5 nm. This is because a thickness of 3 nm or more of the precious metal film can sufficiently reduce the contact resistance on the surface of the anode-side separator, and a thickness of 5 nm or less of the precious metal film can reduce costs compared to anode-side separators that do not have a conductive oxide film and have a precious metal film thickness of 10 nm or more. In other words, it is possible to achieve both a reduction in contact resistance and a reduction in cost.

[0033] The thickness of the precious metal film refers to the average thickness of the precious metal film. While there are no particular limitations on the method for measuring the thickness of the precious metal film, examples include cross-sectional observation using TEM or FE-SEM, Auger analysis, and XPS analysis.

[0034] (4) Method for manufacturing the anode separator The method for manufacturing the anode separator is not particularly limited, but examples include the following: In one example of a manufacturing method, first, a metal substrate made of titanium or stainless steel is prepared. Next, a conductive oxide film containing indium tin oxide (ITO) is deposited on the surface of the metal substrate using an ion plating method, a sputtering method, or the like. Next, a noble metal film containing platinum (Pt) is deposited on the surface of the conductive oxide film using a PVD (physical vapor deposition) method. This produces the anode separator. Examples of PVD methods used for depositing the noble metal film include ion plating and sputtering.

[0035] 2.Water electrolysis device The water electrolysis apparatus according to the embodiment is not particularly limited as long as it is equipped with an anode-side separator according to the embodiment, but a water electrolysis apparatus including a solid polymer type water electrolysis cell using a solid polymer electrolyte membrane, such as the water electrolysis apparatus according to the first embodiment, is preferred.

[0036] Examples of solid polymer type water electrolysis cells include those comprising, for example, a membrane electrode assembly and an anode-side separator and a cathode-side separator according to the embodiment that sandwich the membrane electrode assembly, as in the water electrolysis cell according to the first embodiment. A water electrolysis apparatus including such a solid polymer type water electrolysis cell is usually configured such that multiple sets of water electrolysis cells are stacked in the direction opposite to the anode-side separator and the cathode-side separator, and adjacent water electrolysis cells are electrically connected by the anode-side separator and the cathode-side separator. Examples of such solid polymer type water electrolysis cells include a membrane electrode assembly comprising a solid polymer electrolyte membrane, an anode catalyst layer and a cathode catalyst layer provided on one main surface and the other main surface of the solid polymer electrolyte membrane, an anode power supply laminated on the main surface of the anode catalyst layer, and a cathode power supply laminated on the main surface of the cathode catalyst layer, wherein the anode-side separator is laminated on the main surface of the anode power supply and the cathode-side separator is laminated on the main surface of the cathode power supply.

[0037] Solid polymer electrolyte membranes block the flow of electrons and gases, and also block hydrogen ions (H + It has the function of moving ions from the anode catalyst layer side to the cathode catalyst layer side. The solid polymer electrolyte membrane is not particularly limited, but for example, it is composed of a polymer electrolyte resin which is a solid polymer material such as perfluorosulfonic acid (PFSA) ionomer, and consists of an ion exchange membrane in which the polymer membrane having ion conductivity is the electrolyte.

[0038] The anode catalyst layer has the function of generating hydrogen ions, electrons, and oxygen gas from raw water. The anode catalyst layer is not particularly limited, but for example, it consists of a catalyst and an ionomer, and is formed by coating the catalyst with the ionomer. The catalyst is not particularly limited, but for example, a supported catalyst is formed by supporting platinum group metals such as platinum, iridium, ruthenium, or alloys thereof on carrier particles. The carrier particles are not particularly limited, but for example, carbon carrier particles such as carbon black are used. The ionomer is, for example, a polymer electrolyte resin which is a solid polymer material such as a fluorine-based resin of the same quality as the solid polymer electrolyte membrane, and has proton conductivity due to the ion exchange groups it possesses. Unlike the anode catalyst layer, the cathode catalyst layer generates hydrogen ions and electrons into hydrogen gas (H 2 It has the function of making the cathode catalyst layer a catalyst. The cathode catalyst layer is not particularly limited, but for example, it consists of 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.

[0039] One method for fabricating a membrane electrode assembly is to form an anode catalyst layer and a cathode catalyst layer on one main surface and the other main surface of a solid polymer electrolyte membrane, respectively, and then sandwich the resulting assembly between an anode power supply and a cathode power supply. One method for forming the catalyst layer is to apply a catalyst layer forming coating solution to a predetermined position on the main surface of the solid polymer electrolyte membrane and dry it as needed. The catalyst layer forming coating solution is a liquid in which a catalyst and an ionomer are dispersed in a dispersion medium.

[0040] The anode and cathode power supply members are not particularly limited as long as they are conductive members with gas permeability, but for example, they are composed of conductive porous materials, specifically porous metallic materials such as sintered titanium powder, or porous fibrous materials such as carbon fibers or graphite fibers.

[0041] The anode separator is as described in the "1. Anode Separator" section above. The cathode separator may be made of a metal substrate such as titanium, stainless steel, or aluminum. The shape of the metal substrate of the cathode separator is not particularly limited, as long as it is the shape of a general metal substrate that constitutes a cathode separator used in a general water electrolysis apparatus. The thickness of the metal substrate of the cathode separator is not particularly limited and can be set according to the material of the metal substrate, taking into consideration strength and processing, but is for example in the range of 0.1 mm to 1 mm.

[0042] 3. Method for producing hydrogen gas In the hydrogen gas production method according to the embodiment, hydrogen gas is produced by electrolyzing raw water using the water electrolysis apparatus according to the embodiment. The hydrogen gas production method is not particularly limited, but it is preferable to use raw water with a pH of 4 or higher and neutral (pH of 7 or lower). This is because using raw water with a pH of 4 or higher suppresses the dissolution of indium tin oxide (ITO) contained in the conductive oxide film of the anode-side separator of the water electrolysis apparatus, thereby suppressing an increase in the contact resistance of the anode-side separator. [Examples]

[0043] The anode-side separator and water electrolysis apparatus according to the embodiment will be described in more detail below with reference to examples and comparative examples.

[0044] [Example 1] First, a metal plate was prepared by punching out a 5cm x 6cm area of ​​the channel portion of a metal substrate (thickness: 100μm) made of pure titanium, which is used in actual anode-side separator products. Next, a conductive oxide film containing indium tin oxide (ITO) was deposited to a thickness of 100nm on one main surface of the metal plate using the ion plating method. Then, a noble metal film containing platinum (Pt) was deposited to a thickness of 5nm on the surface of the conductive oxide film using the ion plating method. This created a test sample of the anode-side separator.

[0045] [Example 2] A test sample of the anode-side separator was prepared in the same manner as in Example 1, except that a precious metal film was deposited to a thickness of 3 nm.

[0046] [Comparative Example 1] First, a metal plate was prepared in the same manner as in Example 1. Next, a conductive oxide film was deposited on one main surface of the metal plate, in the same manner as in Example 1. This prepared a test sample of the anode-side separator.

[0047] [Comparative Example 2] First, a metal plate was prepared in the same manner as in Example 1. Next, a noble metal film containing platinum (Pt) was deposited to a thickness of 30 nm on one main surface of the metal plate using the ion plating method. This prepared a test sample of the anode separator.

[0048] [Comparative Examples 3-5] In Comparative Example 3, a test sample of the anode separator was prepared in the same manner as in Comparative Example 2, except that a precious metal film was deposited to a thickness of 10 nm. In Comparative Example 4, a test sample of the anode separator was prepared in the same manner as in Comparative Example 2, except that a precious metal film was deposited to a thickness of 5 nm. In Comparative Example 5, a test sample of the anode separator was prepared in the same manner as in Comparative Example 2, except that a precious metal film was deposited to a thickness of 3 nm.

[0049] [Comparative Example 6] A metal plate was prepared in the same manner as in Example 1. The metal plate was then used alone as a test sample for the anode-side separator.

[0050] [Contact resistance before durability testing] For the test samples of Examples 1 and 2 and Comparative Examples 1 to 6, the contact resistance [mΩ·cm] was measured before the durability test. 2The contact resistance between the test sample and the carbon sheet was determined by measurement. Specifically, a carbon sheet (TGP-H-060 manufactured by Toray Industries, Inc.) was placed on the surface of the test sample (the surface of a noble metal film (Examples 1 and 2 and Comparative Examples 2-5), the surface of a conductive oxide film (Comparative Example 1), or one main surface of a metal plate (Comparative Example 6)), a constant load (1 MPa) was applied using a measuring jig, and the current from the power supply was adjusted so that the current flowing through the test sample was 1 A, as measured by an ammeter. The voltage applied to the test sample was measured with a voltmeter, and the contact resistance between the test sample and the carbon sheet was calculated.

[0051] [Contact resistance after durability testing] Durability tests (potential constant corrosion tests) were performed on the test samples of Examples 1 and 2 and Comparative Examples 1 to 6 in accordance with the Japanese Industrial Standards (JIS) electrochemical high-temperature corrosion test method for metal materials (JIS Z 2294:2004). Specifically, the test samples were immersed in an etching solution (dilute sulfuric acid aqueous solution) whose temperature was adjusted to 80°C using temperature-controlled water and whose pH was adjusted to 4 by the amount of sulfuric acid. In this state, a counter electrode made of titanium plate and the test sample (sample electrode) were electrically connected to create a potential difference of 2V between the counter electrode and the sample electrode in a two-electrode system, and the test time was set to 135 hours to corrode the test samples.

[0052] For the test samples after the durability test of Examples 1 and 2 and Comparative Examples 1 to 6, the contact resistance [mΩ·cm] was determined using the same method as the contact resistance before the durability test. 2 The value was determined by measurement.

[0053] [Material costs for membranes] The total material costs of the conductive oxide film and the noble metal film in the test samples of Examples 1 and 2 and Comparative Examples 1 to 6 were calculated as the film material costs for the test samples of Examples 1 and 2 and Comparative Examples 1 to 6, respectively.

[0054] [evaluation] Table 1 below shows the film composition, the thickness of the conductive oxide film and the noble metal film, as well as the contact resistance before and after the durability test and the cost of the film material for the test samples of Examples 1 and 2 and Comparative Examples 1 to 6.

[0055] [Table 1]

[0056] As shown in Table 1 above, in the test samples of Examples 1 and 2, which have a conductive oxide film and a noble metal film, the contact resistance both before and after the durability test was reduced to within the standard range, unlike the test sample of Comparative Example 1, which has a conductive oxide film but no noble metal film.

[0057] Furthermore, in the test samples of Examples 1 and 2, which have a conductive oxide film and a noble metal film thickness of less than 10 nm, the increase in contact resistance after the durability test was suppressed, unlike the test samples of Comparative Examples 4 and 5, which do not have a conductive oxide film and a noble metal film thickness of less than 10 nm. In addition, in the test samples of Examples 1 and 2, which have a conductive oxide film and a noble metal film thickness of 5 nm or less, the film material cost was reduced to within the standard range, unlike the test samples of Comparative Examples 2 and 3, which do not have a conductive oxide film and a noble metal film thickness of 10 nm or more.

[0058] Although embodiments of the anode separator and water electrolysis apparatus of the present invention have been described in detail above, the present invention is not limited to the embodiments described above, and various design modifications can be made without departing from the spirit of the invention as described in the claims. [Explanation of Symbols]

[0059] 100: Water electrolysis device, 20: Water electrolysis cell, 10: Membrane electrode assembly, 12: Anode-side separator, Surface: 12s, 8: Metal substrate, Surface: 8s, 9: Conductive oxide film, Surface: 9s, 7: Noble metal film, Surface: 7s, 14: Cathode-side separator

Claims

1. an anode-side separator used in a water electrolysis apparatus, A metal base material made of titanium or stainless steel, A conductive oxide film containing indium tin oxide (ITO) is provided on the surface of the metal substrate, A noble metal film containing platinum (Pt) is provided on the surface of the conductive oxide film, Equipped with, An anode-side separator characterized in that the thickness of the noble metal film is within the range of 3 nm to 5 nm.

2. A water electrolysis apparatus characterized by comprising the anode-side separator described in Claim 1.

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