JP2024070597A - Anode-side separator and water electrolysis device - Google Patents

Abstract

[Problem] To provide an anode-side separator capable of increasing electrical conductivity. [Solution] The anode-side separator of the present invention is an anode-side separator used in a water electrolysis device, and is characterized in that it comprises 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, and the crystallinity of the conductive oxide film is 20% or more. [Selected Figure] Figure 2

Description

The present invention relates to an anode-side separator for use in a water electrolysis device and a water electrolysis device equipped with the same.

In recent years, a water electrolysis device that produces hydrogen by electrolyzing raw water, etc., has been known that has stacked water electrolysis cells using electrolyte membranes such as solid polymer electrolyte membranes. The water electrolysis cell has, 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, respectively, 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.

The anode-side separator must be highly conductive to transmit electricity to the anode catalyst layer. In addition, when using a metal substrate from the viewpoint of strength, corrosion resistance becomes an issue because the metal substrate is prone to corrosion. For this reason, the anode-side separator is configured to have a conductive layer with high conductivity and excellent corrosion resistance on the surface of the metal substrate. For example, the separator described in Patent Document 1 has a metal substrate made of titanium or the like and a precious metal layer (conductive layer) made of Au that is directly laminated on the metal substrate, and has high conductivity and high corrosion resistance. In addition, the surface roughness of the metal substrate is adjusted to improve the adhesion between the metal substrate and the precious metal layer. Furthermore, the member constituting the anode described in Patent Document 2 has an electrode substrate made of a metal such as aluminum and a conductive oxide film that is provided on the surface of the electrode substrate and forms a nanostructure.

JP 2018-127707 A JP 2013-231208 A

The anode-side separator described in Patent Document 1 has a precious metal layer on the surface of the metal substrate, and therefore has excellent corrosion resistance, but is expensive and difficult to use in actual products. To address this issue, it has been considered to use an anode-side separator having a conductive layer on the surface of the metal substrate, such as the member described in Patent Document 2, in which an inexpensive conductive oxide film is provided on the surface of a metal substrate made of aluminum or the like, and in this case, a conductive oxide film with high conductivity is required. Meanwhile, in a water electrolysis device, a high voltage of about 1.8 V is usually applied to the water electrolysis cell. For this reason, corrosion resistance becomes an issue again in an anode-side separator having a conductive oxide film on the surface of a metal substrate made of aluminum or the like.

As a result, anode-side separators have been proposed that have a conductive oxide film on the surface of a metal substrate, and that include a conductive oxide film containing indium tin oxide (ITO), which is considered to have high conductivity among conductive oxides, with emphasis placed on the durability of the conductive oxide film.

The present invention was made in consideration of these points, and its purpose is to provide an anode-side separator with high electrical conductivity and a water electrolysis device equipped with the same.

In order to solve the above problems, the anode-side separator of the present invention is an anode-side separator used in a water electrolysis device, and is characterized in that it comprises 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, and the crystallinity of the conductive oxide film is 20% or more.

The water electrolysis device of the present invention is also characterized by having the above-mentioned anode-side separator.

According to the present invention, it is possible to increase the electrical conductivity.

FIG. 2 is an exploded cross-sectional view illustrating a schematic configuration of a water electrolysis cell, which is a constituent unit of the water electrolysis device according to the first embodiment, including the anode separator according to the first embodiment. FIG. 2 is an enlarged view of a portion X in FIG. 1 is a graph showing the change in contact resistance before a durability test versus the crystallinity of the conductive oxide film of the anode-side separator in the comparative example and Examples 1 to 5. 1 is a graph showing the change in contact resistance after a durability test versus the crystallinity of the conductive oxide film of the anode-side separator in the comparative example and Examples 1 to 5.

First, the anode-side separator and water electrolysis device according to the embodiment will be described with reference to the first embodiment. FIG. 1 is an exploded cross-sectional view showing the structure of a water electrolysis cell, which is a constituent unit of the water electrolysis device according to the first embodiment and includes the anode-side separator according to the first embodiment. FIG. 2 is an enlarged view of the X portion of FIG. 1.

As shown in FIG. 1, the water electrolysis device 100 according to the first embodiment is configured by stacking a plurality of water electrolysis cells 20. The water electrolysis cells 20 are solid polymer water electrolysis cells including 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.

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 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.

As shown in Figs. 1 and 2, the anode-side separator 12 comprises 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 crystallinity of the conductive oxide film 9 is 40% or more. In the anode-side separator 12, a groove 8g for a fluid passage is provided on the main surface 8a side of the metal substrate 8 facing the solid polymer electrolyte membrane 2, thereby providing a fluid passage 12p, and a water supply port 12f and a drain port 12d communicating with the fluid passage 12p are provided.

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

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 at the same time electrically connect to the adjacent water electrolysis cell (not shown). In the water electrolysis device 100, multiple sets of 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).

When hydrogen gas is produced by electrolyzing raw water using such a water electrolysis device 100, 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, 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 feeder 6a and the cathode power feeder 6c, respectively. As a result, the raw water is electrolyzed in the anode catalyst layer 4a to generate hydrogen ions (H ⁺ ), electrons, and oxygen gas (O ² ). Next, the hydrogen ions permeate 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, the hydrogen ions receive electrons from the cathode catalyst layer 4c and are molecularized, and hydrogen gas (H ² ) is obtained in the fluid passage 14p of the cathode 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 port 12d together with most of the raw water.

The effects of the anode separator 12 and the water electrolysis apparatus 100 described above will be described below.
Here, the problem of the water electrolysis apparatus 100 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 and stainless steel (e.g., aluminum, etc.) instead of the anode-side separator 12 according to the first embodiment as in the conventional art will be described. In the case of using an anode-side separator in which a conductive oxide film is provided on the surface of a metal substrate, the conductive oxide film is generally porous, so that the raw water supplied to the fluid passage permeates the conductive oxide film, and the conductive oxide film and the metal substrate containing different metals come into contact with each other in the raw water. As a result, a corrosion cell is formed between the conductive oxide film and the metal substrate and the raw water, causing a current to flow and causing bimetallic corrosion. Furthermore, in the water electrolysis apparatus, when the raw water is electrolyzed, a high voltage of, for example, about 1.8 V is usually applied to the water electrolysis cell of the constituent unit, so that the anode-side separator is exposed 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 and stainless steel is used as the metal substrate, the corrosion of the metal substrate due to galvanic corrosion is accelerated because the general-purpose metals other than titanium and stainless steel do not have sufficient corrosion resistance, and the corrosion resistance of the anode-side separator becomes an issue.

In contrast, the pure titanium used in 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 device 100 according to the first embodiment, the conductive oxide film 9 and the metal substrate 8 containing different metals come into contact with each other in the raw water in the anode-side separator 12, and even in a situation in which the anode-side separator 12 is exposed to a high-voltage environment by applying a high voltage of, for example, about 1.8 V to the water electrolysis cell, corrosion of the metal substrate 8 due to bimetallic corrosion can be suppressed. In addition, in the anode-side separator 12 according to the first embodiment, the indium tin oxide contained in the conductive oxide film 9 provided as a conductive layer on the surface 8s of the metal substrate 8 is less expensive than precious metals such as Au contained in the precious metal layer provided as a conductive layer on the surface of the metal substrate in the separator of the conventional technology. Therefore, the anode-side separator 12 can reduce costs compared to the separator of the conventional technology.

Furthermore, a conductive oxide film containing indium tin oxide, such as the conductive oxide film 9 provided on the surface 8s of the metal substrate 8 in the anode-side separator 12 according to the first embodiment, is assumed to have a high conductivity among conductive oxide films, but the conductivity and durability depend on the crystallinity. The conductive oxide film 9 according to the first embodiment has a crystallinity of 40% or more, and therefore has a high conductivity compared to a film with a crystallinity of less than 20%, such as an amorphous film. Therefore, the conductivity of the anode-side separator can be increased. Furthermore, the conductive oxide film 9 is energetically more stable than a film with a crystallinity of less than 40%, so that dissolution is suppressed when used in a water electrolysis device, and the durability is high. Therefore, the durability of the anode-side separator can be improved. Therefore, the electrolysis performance of the water electrolysis device 100 can be sufficiently improved, and the durability of the water electrolysis device 100 can be improved.

In the anode-side separator according to the embodiment, as in the first embodiment, titanium or stainless steel, which has significantly higher corrosion resistance than other general-purpose metals, is used for the metal substrate. This makes it possible to suppress corrosion of the metal substrate. In addition, a conductive oxide film containing indium tin oxide, which is less expensive than precious metals, is used as the conductive layer provided on the surface of the metal substrate. This makes it possible to reduce costs. In addition, the conductive oxide film has a crystallinity of 20% or more, which makes it possible to increase the conductivity of the anode-side separator. Furthermore, when the conductive oxide film has a crystallinity of 40% or more, the durability of the anode-side separator can be improved.

Next, the configuration of the anode separator and water electrolysis device according to the embodiment, as well as the hydrogen gas production method according to the embodiment, will be described in detail.

1. Anode-side separator The anode-side separator according to the embodiment is an anode-side separator used in a water electrolysis device, 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, and the crystallinity of the conductive oxide film is 20% or more. Here, the "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 and the conductive oxide film of the anode-side separator, as well as other components, will be described in detail below.

(1) Metal Substrate Titanium used in the metal substrate is not particularly limited, but examples thereof include pure titanium and titanium alloys. Pure titanium is not particularly limited, but examples thereof include those specified in JIS H 4600:2012. Titanium alloys are not particularly limited, but examples thereof include Ti-Al and the like. Of the titanium, pure titanium is preferable because it has particularly high corrosion resistance. Stainless steel used in the metal substrate is, for example, austenitic stainless steel such as SUS304.

The shape of the metal substrate is not particularly limited as long as it is a general shape of a metal substrate constituting an anode-side separator used in a general water electrolysis device, and may be a shape in which grooves for fluid passages of a separator are provided on the metal substrate. When the water electrolysis device is a water electrolysis device including a solid polymer type water electrolysis cell, the shape in which grooves for fluid passages are provided on the metal substrate may be, for example, a shape in which grooves for fluid passages are provided on the main surface side of the metal substrate facing the solid polymer electrolyte membrane, as in the first embodiment. The shape of the metal substrate may be a flat plate shape in which grooves for fluid passages are not provided on the metal substrate. In addition, when the metal substrate is a flat plate shape, for example, it constitutes a flat type separator in which the fluid passages are separated. The surface roughness Rz of the metal substrate is, for example, in the range of 0.05 μm to 0.8 μm, and is preferably 0.1 μm or more, particularly 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., but is, for example, in the range of 0.08 mm to 1 mm.

(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 base material. When the water electrolysis device is a water electrolysis device containing a solid polymer water electrolysis cell, the conductive oxide film is preferably provided on at least the main surface of the metal base material facing the solid polymer electrolyte membrane as in the first embodiment, and may be provided on the entire surface of the metal base material.

The crystallinity of the conductive oxide film is not particularly limited as long as it is 20% or more, but 40% or more is preferable. This is because the conductive oxide film is energetically more stable, is less likely to dissolve when used in a water electrolysis device, and is more durable, thereby improving the durability of the anode-side separator.

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 in the range of 0.3 μm or more. When the thickness of the conductive oxide film is 0.05 μm or more, the conductive oxide film can be uniformly formed. Furthermore, when the thickness of the conductive oxide film is 0.3 μm or more, the corrosion resistance of the anode-side separator can be sufficiently ensured when the surface of the metal substrate becomes rough due to the pressing process. On the other hand, when the thickness of the conductive oxide film is 0.8 μm or less, the conductive oxide film can be prevented from peeling off from the metal substrate due to residual stress.

(3) Manufacturing method of anode-side separator The manufacturing method of the anode-side separator is not particularly limited, but examples thereof include a manufacturing method in which a metal base material made of titanium or stainless steel is prepared, and a conductive oxide film containing indium tin oxide (ITO) is formed on the surface of the metal base material by using a sputtering method. In this manufacturing method, the method for making the crystallinity of the conductive oxide film 20% or more or 40% or more is not particularly limited, but a method of adjusting the film formation conditions such as the target used during film formation by sputtering, the cathode power, and the film formation time, a method of heat-treating the conductive oxide film after the conductive oxide film is formed, and the like are used.

The method of adjusting the film formation conditions during film formation by the sputtering method includes, for example, appropriately selecting the type of target to be used according to the product of the sputtering device used for film formation, and setting the cathode power and film formation time, etc. The type of target to be used includes, for example, a composite material containing In ₂ O ₃ and SnO ₂ , in which the weight ratio of In ₂ O ₃ and SnO ₂ is set to various ratios, etc.

Methods for heat treating the conductive oxide film after it has been formed include, for example, a method for heat treating the conductive oxide film in an atmospheric furnace at a specified atmospheric furnace temperature and heat treatment time, and a method for heat treating the conductive oxide film in an argon furnace at a specified argon furnace temperature and heat treatment time.

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, like the water electrolysis device according to the first embodiment, a water electrolysis device including a solid polymer water electrolysis cell using a solid polymer electrolyte membrane is preferable.

As the solid polymer water electrolysis cell, for example, like the water electrolysis cell according to the first embodiment, there 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 an example of such a solid polymer water electrolysis cell, there 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 main surface and the other main surface of the solid polymer electrolyte membrane, respectively, 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, and 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.

The solid polymer electrolyte membrane has a function of preventing the flow of electrons and gases and of transferring 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, for example, made of a polymer electrolyte resin that is a solid polymer material such as perfluorosulfonic acid (PFSA) ionomer, and is an ion exchange membrane that uses an ion-conductive polymer membrane as an electrolyte.

The anode catalyst layer has a 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 catalyst supported on a carrier particle, and a platinum group metal such as platinum or an alloy thereof is supported on the carrier particle. The carrier particle is, for example, not limited to a carbon carrier 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 quality as the solid polymer electrolyte membrane, and has proton conductivity due to the ion exchange group it has. Unlike the anode catalyst layer, the cathode catalyst layer has a function of converting hydrogen ions and electrons into hydrogen gas (H ² ). 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 the ionomer are the same as those of the anode catalyst layer.

The anode and cathode power supplies are not particularly limited as long as they are conductive materials that have gas permeability, but may be made of, for example, conductive porous materials, specifically porous metal materials such as sintered titanium powder, or porous fiber materials such as carbon fibers and graphite fibers.

The anode side separator is as described above in the section "1. Anode side separator." The cathode side separator may be, for example, one having 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, etc.

3. Hydrogen Gas Production Method The hydrogen gas production method 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.

The following provides a more detailed explanation of the anode-side separator and water electrolysis device according to the embodiment, with examples, comparative examples, and reference examples.

1. Evaluation of change in contact resistance relative to the crystallinity of the conductive oxide film of the anode-side separator Anode-side separators of the comparative example and the example were prepared, and the crystallinity of the conductive oxide film and the contact resistance before and after the durability test were calculated, and the change in contact resistance before and after the durability test relative to the crystallinity of the conductive oxide film was evaluated.

[Comparative Example]
First, a flat metal substrate made of pure titanium was prepared. Next, a natural oxide film and the like were removed from one main surface (film-forming surface) of the metal substrate by reverse sputtering, and then a conductive oxide film containing indium tin oxide (ITO) was formed to a thickness of 100 nm on one main surface of the metal substrate using a sputtering device (UHSP-PL2060TO) manufactured by Shimadzu Corporation under the following conditions by using a sputtering method. This produced an anode-side separator.

Target used: composite containing In ₂ O ₃ (90 wt%) and SnO ₂ (10 wt%) Cathode power: 4.4 kW (DC)
Film formation time: 20 seconds Preheating: None

[Example 1]
An anode-side separator was prepared in the same manner as in the comparative example, except that the cathode power and deposition time during deposition of the conductive oxide film were set to 3 kW (DC) and 80 seconds, respectively.

[Example 2]
An anode-side separator was prepared in the same manner as in the comparative example, except that the cathode power and deposition time during deposition of the conductive oxide film were set to 1.5 kW (DC) and 180 seconds, respectively.

[Example 3]
An anode-side separator was prepared in the same manner as in the comparative example, except that the cathode power and film-forming time during the formation of the conductive oxide film were set to 4 kW (DC) and 60 seconds, respectively.

[Example 4]
As in the comparative example, a metal substrate was prepared, and a conductive oxide film was formed on one main surface of the metal substrate. The metal substrate and the conductive oxide film were then placed in an atmospheric furnace and heat-treated in the atmospheric furnace at 350° C. for 5 minutes to produce an anode-side separator.

[Example 5]
As in the comparative example, a metal substrate was prepared, and a conductive oxide film was formed on one main surface of the metal substrate. The metal substrate and the conductive oxide film were then placed in an argon furnace and heat-treated in the argon furnace at 250° C. for 5 minutes to produce an anode-side separator.

[Degree of crystallinity of conductive oxide film]
X-ray diffraction spectra were measured by powder X-ray diffraction (XRD) for the conductive oxide films of the anode-side separators of the Comparative Example and Examples 1 to 5. Then, fitting was performed for the diffraction line portions (peak portions) due to crystalline matter and the scattered light portions (halo portions) due to amorphous matter in the X-ray diffraction spectra to determine the integrated intensity of each portion, and the crystallinity was calculated by the following formula (1).

X = Ic / (Ic + Ia) × 100 (1)
(In formula (1), "X" represents the degree of crystallinity, "Ic" represents the integrated intensity of the peak portion, and "Ia" represents the integrated intensity of the halo portion.)

[Contact resistance before durability test]
Test samples were cut out from the anode-side separators of the Comparative Example and Examples 1 to 5, and the contact resistance [mΩ·cm ² ] of the test samples before the durability test was calculated. Specifically, a carbon sheet (TGP-H-060 manufactured by Toray Industries, Inc.) was placed on the conductive oxide film side of the test sample, and a constant load (1 MPa) was applied using a measuring jig. A current from a power source was adjusted so that the current flowing through the test sample was 1 A as measured by an ammeter, and the voltage applied to the test sample was measured using a voltmeter, and the contact resistance between the test sample and the carbon sheet was calculated.

[Contact resistance after durability test]
A durability test (constant potential corrosion test) was conducted on the anode-side separators of the comparative example and Examples 1 to 5 in accordance with the electrochemical high-temperature corrosion test method for metallic materials of the Japanese Industrial Standards (JIS Z 2294:2004). Specifically, a test sample was cut out from the anode-side separator, and the test sample was immersed in a corrosive solution (dilute sulfuric acid aqueous solution) whose temperature was adjusted to 80° C. by temperature-adjusting water and whose pH was adjusted to 4 by the amount of sulfuric acid. In this state, a counter electrode made of a platinum plate and the test sample (sample electrode) were electrically connected to generate a potential difference of 2 V between the counter electrode and the sample electrode, and the test sample was corroded. During the test, the potential of the test sample was kept constant by a reference electrode. The test time was 60 hours. HZ-Pro manufactured by Hokuto Denko was used as a test device for the test.

For the test samples of the comparative example and examples 1 to 5 after the durability test, the contact resistance was calculated using the same method as that used to calculate the contact resistance before the durability test.

[evaluation]
The degrees of crystallinity calculated for the conductive oxide film of the anode-side separator of the Comparative Example and Examples 1 to 5 are shown in Table 1 below. The contact resistances calculated for the test samples of the Comparative Example and Examples 1 to 5 before and after the durability test are also shown in Table 1 below. Fig. 3 is a graph showing the change in contact resistance before the durability test versus the crystallinity of the conductive oxide film of the anode-side separator of the Comparative Example and Examples 1 to 5. Fig. 4 is a graph showing the change in contact resistance after the durability test versus the crystallinity of the conductive oxide film of the anode-side separator of the Comparative Example and Examples 1 to 5.

3, in the anode-side separators of the comparative example and Examples 1 to 5, when the crystallinity of the conductive oxide film was 19.8% or more, the contact resistance before the durability test was less than 10 mΩ· ^cm2 and did not exceed the range of the standard value, but the contact resistance after the durability test was 10 mΩ· ^cm2 or more and sometimes exceeded the range of the standard value. On the other hand, when the crystallinity of the conductive oxide film was 38.2% or more, the contact resistance after the durability test was also less than 10 mΩ· ^cm2 and did not exceed the range of the standard value.

In addition, the test samples of the anode-side separators of the Comparative Example and Examples 1 to 5 after the durability test were observed visually and with an optical microscope. As a result, discoloration was observed in the conductive oxide film in the test samples of the Comparative Example and Example 1 after the durability test, which suggests that the indium tin oxide contained in the conductive oxide film had dissolved. In contrast, no discoloration was observed in the conductive oxide film in the test samples of Examples 2 to 5 after the durability test, which suggests that the dissolution of the indium tin oxide contained in the conductive oxide film had been suppressed. Furthermore, it was confirmed that no corrosion of the metal substrate had occurred in the test samples of the Comparative Example and Examples 1 to 5 after the durability test.

2. Evaluation of Change in Contact Resistance Before and After Heat Treatment of Anode-Side Separator The change in contact resistance before and after heat treatment of the anode-side separator was evaluated when the heat treatment was performed in an air furnace or an argon furnace.

(1) In the case of heat treatment in an atmospheric furnace First, the contact resistance was calculated for the anode-side separator prepared in the same manner as in the comparative example before heat treatment was performed under various conditions (conditions of air furnace temperature and heat treatment time) in an atmospheric furnace. Specifically, test samples were cut out from the anode-side separator before heat treatment was performed under various conditions, and the contact resistance of the test samples was calculated using the same method as the calculation method of contact resistance in the above item "1. Evaluation of change in contact resistance with respect to crystallinity of conductive oxide film of anode-side separator". Next, the same anode-side separator was subjected to heat treatment under various conditions in an atmospheric furnace, and the contact resistance was calculated. Specifically, test samples were cut out from the anode-side separator after heat treatment was performed under various conditions, and the contact resistance of the test samples was calculated using the same method as the calculation method of contact resistance described above. The change in contact resistance after the heat treatment under various conditions relative to the contact resistance before the heat treatment under various conditions was calculated as the change in contact resistance due to the heat treatment under various conditions (conditions of atmospheric furnace temperature and heat treatment time). The calculation results are shown in Table 2 below.

(2) Case of heat treatment in an argon furnace First, the contact resistance was calculated for the anode-side separator prepared in the same manner as in the comparative example before the heat treatment was performed under various conditions (argon furnace temperature and heat treatment time) in an argon furnace. Specifically, a test sample was cut out from the anode-side separator before the heat treatment was performed under various conditions, and the contact resistance of the test sample was calculated by the same method as the above-mentioned method of calculating the contact resistance. Next, the contact resistance was calculated for the same anode-side separator after the heat treatment was performed under various conditions in an argon furnace. Specifically, a test sample was cut out from the anode-side separator after the heat treatment was performed under various conditions, and the contact resistance of the test sample was calculated by the same method as the above-mentioned method of calculating the contact resistance. Then, the change in the contact resistance after the heat treatment was performed under various conditions relative to the contact resistance before the heat treatment was performed under various conditions was calculated as the change in contact resistance due to the heat treatment under various conditions (argon furnace temperature and heat treatment time). The calculation results are shown in Table 3 below.

(3) Evaluation As shown in Table 2 above, when heat treatment was performed in an atmospheric furnace under various conditions (conditions of atmospheric furnace temperature and heat treatment time), the contact resistance of the test sample could be reduced by heat treatment under conditions other than the conditions where the atmospheric furnace temperature was too low and the heat treatment time was too short, and the conditions where the atmospheric furnace temperature was too high and the heat treatment time was too long. It is considered that the crystallinity of the conductive oxide film could be improved under conditions other than the condition where the atmospheric furnace temperature was too low and the heat treatment time was too short. It is considered that the effect of reducing the contact resistance due to the improvement in the crystallinity of the conductive oxide film was offset by the oxidation of the conductive oxide film under conditions where the atmospheric furnace temperature was too high and the heat treatment time was too long.

As shown in Table 3 above, when heat treatment was performed in an argon furnace under various conditions (argon furnace temperature and heat treatment time), the contact resistance of the test sample was reduced by heat treatment under all conditions except for those in which the argon furnace temperature was too low and the heat treatment time was too short. It is believed that the crystallinity of the conductive oxide film was improved.

The above provides a detailed explanation of the embodiments of the anode-side separator and water electrolysis device of the present invention, but the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the spirit of the present invention as described in the claims.

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 (3)

An anode-side separator for use in a water electrolysis apparatus, comprising:
A metal substrate made of titanium or stainless steel;
A conductive oxide film including indium tin oxide (ITO) provided on a surface of the metal base material,
The anode-side separator is characterized in that the conductive oxide film has a crystallinity of 20% or more. The anode-side separator according to claim 1, characterized in that the crystallinity of the conductive oxide film is 40% or more. A water electrolysis device comprising the anode-side separator according to claim 1 or 2.

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