JP7392087B1 - Water electrolysis cell parts, water electrolysis cells and water electrolysis cell stacks - Google Patents

Abstract

[Problem] To provide a member for a water electrolysis cell in which cracks are reduced between a coating material and a base material of an anode gas diffusion layer or a base material of a separator, and corrosion can be suppressed by forming a joint interface with low penetration resistance. do. [Solution] A member for a water electrolysis cell, which is at least one of an anode gas diffusion layer and a separator, includes a base material of at least one of the base material of the anode gas diffusion layer and the separator base material; A coating material containing conductive ceramics located at least in a portion thereof, and a titanium layer containing oxygen located between the base material and the coating material, the thickness of the titanium layer containing oxygen being 78 cm. 7 nm or less, and the thickness of the coating material is 190 nm or more and 4223 nm or less. [Selection diagram] None

Description

The present disclosure relates to a water electrolysis cell member, a water electrolysis cell, and a water electrolysis cell stack.

Water electrolysis (hereinafter sometimes referred to as "water electrolysis") is a method of producing hydrogen and oxygen from water by electrolysis. For example, in technologies that utilize hydrogen as an energy source, water electrolysis is a promising technology for sustainable hydrogen production.

A water electrolysis cell used for water electrolysis includes a separator, an anode gas diffusion layer, an anode catalyst layer, an electrolyte membrane, etc. in this order (for example, see Patent Document 1 below).

Patent No. 7053128

Members that come into contact with the oxygen gas generated at the anode, such as gas diffusion layers (GDLs), separators, etc., are exposed to a highly oxidizing atmosphere. Therefore, the gas diffusion layer, the separator, etc. are easily corroded, and as a result, the resistance of the water electrolysis cell is likely to increase, and the life of the water electrolysis cell is likely to be shortened.

From the viewpoint of reducing contact resistance with the catalyst and suppressing corrosion, there is a method of plating a noble metal such as platinum between the anode catalyst layer and the anode gas diffusion layer in the water electrolysis cell described in Patent Document 1. However, cracks are likely to occur in the anode gas diffusion layer, and uncoated portions may be exposed and corrosion may not be suppressed.

The purpose of the present disclosure is for a water electrolysis cell in which cracks are reduced between a coating material and a base material of an anode gas diffusion layer or a base material of a separator, and corrosion can be suppressed by forming a joint interface with low penetration resistance. An object of the present invention is to provide a member, and a water electrolysis cell and a water electrolysis cell stack including the same.

The present disclosure includes the following aspects.
<1> A water electrolysis cell member that is at least one of an anode gas diffusion layer and a separator,
At least one base material of an anode gas diffusion layer base material and a separator base material;
a coating material containing conductive ceramics located on at least a portion of the surface of the base material;
a titanium layer containing oxygen located between the base material and the coating material,
The thickness of the titanium layer containing oxygen is 78.7 nm or less,
The coating material has a thickness of 190 nm or more and 4223 nm or less.
<2> The conductive ceramic includes at least one of a nitride, a carbide, and a carbonitride, and the nitride, the carbide, and the carbonitride each independently include titanium, zirconium, vanadium, niobium, and tantalum. The member for a water electrolysis cell according to <1>, comprising at least one type of.
<3> The water electrolysis cell member according to <1>, wherein the conductive ceramic contains titanium nitride.
<4> The water electrolysis cell member according to any one of <1> to <3>, wherein the oxygen-containing titanium layer has a thickness of 45.5 nm or less.
<5> The water electrolysis cell member according to any one of <1> to <4>, wherein the oxygen-containing titanium layer has a thickness of 10.9 nm or less.
<6> The water electrolysis cell member according to any one of <1> to <5>, wherein the coating material has a thickness of 490 nm or more and 4223 nm or less.
<7> The water electrolysis cell member according to any one of <1> to <6>, wherein the coating material has a thickness of 2042 nm or more and 4223 nm or less.
<8> A water electrolysis cell comprising a separator, an anode gas diffusion layer, an anode catalyst, a cathode catalyst, and an electrolyte membrane,
A water electrolysis cell, wherein at least one of the separator and the anode gas diffusion layer included in the water electrolysis cell is composed of the member for a water electrolysis cell according to any one of <1> to <7>.
<9> A water electrolysis cell stack formed by laminating a plurality of water electrolysis cells according to <8>.

According to the present disclosure, cracks are reduced between the coating material and the base material of the anode gas diffusion layer or the base material of the separator, and a joint interface with low penetration resistance is formed to suppress corrosion for a water electrolysis cell. A member, a water electrolysis cell, and a water electrolysis cell stack including the member are provided.

FIG. 1 is a schematic cross-sectional view of a water electrolysis cell. FIG. 2 is a graph showing the relationship between the penetration resistance of the coating material-coated base materials shown in Examples 1 to 7 and Comparative Examples 1 to 4 and the thickness of the oxygen-containing titanium layer. FIG. 3 is a graph showing the relationship between the penetration resistance of the coating material-coated substrates shown in Examples 1 to 7 and Comparative Examples 1 to 4 and the thickness of the coating material.

Embodiments of the present disclosure will be described below. The present disclosure is not limited to the following embodiments, and can be implemented with appropriate changes within the scope of the purpose of the present disclosure. The proportions of dimensions in the drawings do not necessarily represent the proportions of actual dimensions.

In the present disclosure, a numerical range expressed using "~" means a range that includes the numerical values written before and after "~" as lower and upper limits.

In numerical ranges described step by step in this disclosure, the upper limit stated in one numerical range may be replaced with the upper limit of another numerical range described step by step, and the upper limit described in a certain numerical range The lower limit value given may be replaced by a lower limit value of another numerical range described step by step. In the numerical ranges described step by step in this disclosure, the upper limit or lower limit described in a certain numerical range may be replaced with the value shown in the Examples.

In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

<Materials for water electrolysis cells>
The water electrolysis cell member of the present disclosure will be described below.
The member for a water electrolysis cell of the present disclosure is a member for a water electrolysis cell that is at least one of an anode gas diffusion layer and a separator, and includes at least one of the base material of the anode gas diffusion layer and the separator base material, and the base material of the anode gas diffusion layer and the separator base material. A coating material containing conductive ceramics located on at least a portion of the surface of a base material, and a titanium layer containing oxygen located between the base material and the coating material, the titanium layer containing oxygen. The thickness of the coating material is 78.7 nm or less, and the thickness of the coating material is 190 nm or more and 4223 nm or less.

The water electrolysis cell member of the present disclosure is at least one of an anode gas diffusion layer and a separator (preferably an anode separator), and is used as a constituent member of a water electrolysis cell. In the water electrolysis cell member of the present disclosure, the presence of the titanium layer containing oxygen between the coating material containing conductive ceramics and the base material relieves residual stress between the coating material and the base material, and the anode Corrosion of the gas diffusion layer or separator is suppressed, and as a result, low penetration resistance can be achieved.

Furthermore, by reducing the thickness of the coating material, cracks between the coating material and the base material of the anode gas diffusion layer or the separator are reduced, and a bonding interface with low penetration resistance can be formed. Further, by reducing the thickness of the titanium layer containing oxygen, a bonding interface with even lower penetration resistance can be formed.

The anode gas diffusion layer is a gas diffusion layer disposed at the anode in a water electrolysis cell. The separator is a member disposed on the opposite side of the electrolyte membrane in the gas diffusion layer.

A water electrolysis cell is the smallest unit capable of producing hydrogen and oxygen by electrolysis of water. The gas diffusion layer may be applied to a water electrolysis device. A water electrolysis device is a device that generates hydrogen and oxygen by electrolyzing water. The water electrolysis device may include a water electrolysis cell stack formed by stacking a plurality of water electrolysis cells.

(Base material)
The water electrolysis cell member of the present disclosure includes at least one of a base material of an anode gas diffusion layer and a separator base material. When the water electrolysis cell member is an anode gas diffusion layer, the base material is a base material of the anode gas diffusion layer, and when the water electrolysis cell member is a separator, the base material is a separator base material.

The material of the base material is not particularly limited, and examples thereof include metals such as titanium and stainless steel, and carbon. The base material may contain titanium, from the viewpoint that a titanium layer containing oxygen is likely to be formed between the base material and the coating material by water electrolysis described below, and from the viewpoint of suppressing cracking and electrical resistance of the coating material. preferable.

From the viewpoint of allowing fluid to flow through the base material, the base material may be composed of a porous body, a powder sintered body, a fiber sintered body, a metal mesh, felt, or the like.

(Coating material)
The water electrolysis cell member of the present disclosure includes a coating material containing conductive ceramics located on at least a portion of the surface of a base material. The coating material only needs to contain one or more types of conductive ceramics, and may be a layer or film made of conductive ceramics.

The conductive ceramic contained in the coating material preferably contains at least one of nitride, carbide, and carbonitride, and nitride, carbide, and carbonitride each independently include titanium, zirconium, vanadium, niobium, It is preferable that at least one kind of tantalum is included.

The conductive ceramic may be a nitride, a carbide, a carbonitride, or a nitride. Nitride, carbide, and carbonitride may contain at least titanium, and may contain other metals (for example, at least one of zirconium, vanadium, niobium, and tantalum) together with titanium.

Examples of the conductive ceramics contained in the coating material include titanium nitride, titanium carbonitride, zirconium nitride, vanadium nitride, niobium nitride, and tantalum nitride. Among these, since a titanium layer containing oxygen is likely to be formed by water electrolysis, it is preferable to contain titanium nitride, and more preferably to be made of titanium nitride.

The method of forming a coating material containing conductive ceramics on a base material is not particularly limited. For example, the coating material can be formed by AIP (arc ion plating), PLD (pulsed laser deposition), gas nitriding, or the like. In order to roughen the surface and improve adhesion with the coating material, the base material may be subjected to blasting treatment.

When the thickness of the coating material is thin, cracks between the coating material and the base material of the anode gas diffusion layer or the separator tend to be reduced, and the internal resistance tends to be reduced. Therefore, the thickness of the coating material is 190 nm or more and 4223 nm or less, preferably 490 nm or more and 4223 nm or less, more preferably 2042 nm or more and 4223 nm or less, and even more preferably 2042 nm or more and 3000 nm or less.
By adjusting the thickness of the coating material, it is possible to suppress the occurrence and propagation of cracks in the coating material, so it is possible to reduce the thickness of the titanium layer containing oxygen that forms at the interface between the coating material and the base material. can. By reducing the thickness of the coating material, it tends to be possible to suppress the occurrence and propagation of cracks. Increasing the thickness of the coating material tends to suppress an increase in penetration resistance.

(Titanium layer containing oxygen)
The water electrolysis cell member of the present disclosure includes a titanium layer containing oxygen located between a base material and a coating material. Due to the presence of the titanium layer containing oxygen between the coating material containing conductive ceramics and the base material, a highly adhesive bonding interface is formed between the coating material and the base material, making it possible to suppress corrosion. For example, the thickness of the titanium layer containing oxygen can be evaluated by cross-sectionally processing the vicinity of the base material and coating material with a focused ion beam, and then analyzing it with a scanning transmission electron microscope and an energy dispersive X-ray spectrometer. can.

From the viewpoint of suppressing the contact resistance of the coating material, the thickness of the titanium layer containing oxygen is 78.7 nm or less, preferably 45.5 nm or less, and 10. More preferably, the thickness is 9 nm or less. Penetration resistance can be reduced by reducing the thickness of the titanium layer containing oxygen.

The method for forming the oxygen-containing titanium layer located between the base material and the coating material is not particularly limited. For example, titanium oxide, titanium nitride, etc. may be laminated on the base material by sputtering or the like. A base material provided with a coating material is incorporated as at least one of an anode gas diffusion layer and a separator into a water electrolysis cell, a water electrolysis stack formed by laminating water electrolysis cells, etc., and water electrolysis is performed using the water electrolysis cell, water electrolysis stack, etc. By performing this step, the base material provided with the coating material may be exposed to an oxygen atmosphere.

When exposing a base material with a coating material to an oxygen atmosphere by performing water electrolysis as described above, adjusting the cell temperature, water flow rate, current density, water electrolysis time, etc. during water electrolysis can make it possible to contain oxygen. The thickness of the titanium layer can be adjusted.

<Water electrolysis cell>
The water electrolysis cell of the present disclosure will be described below.
A water electrolysis cell of the present disclosure includes a separator, an anode gas diffusion layer, an anode catalyst, a cathode catalyst, and an electrolyte membrane, the separator and anode gas diffusion layer included in the water electrolysis cell. At least one of the layers is composed of the water electrolysis cell member of the present disclosure described above.

In the water electrolysis cell of the present disclosure, at least one of the separator (preferably a separator for an anode) and the anode gas diffusion layer is composed of the above-described member for a water electrolysis cell of the present disclosure.

For example, the water electrolysis cell of the present disclosure may include an anode separator made of the water electrolysis cell member of the present disclosure described above, and the anode separator made of the water electrolysis cell member of the present disclosure described above. It may include a gas diffusion layer or both.

The separator, anode gas diffusion layer, anode catalyst, cathode catalyst, electrolyte membrane, etc. that may be composed of materials other than the aforementioned water electrolysis cell members of the present disclosure include separators and anode gas diffusion layers used in conventionally known water electrolysis cells. layers, anode catalysts, cathode catalysts and electrolyte membranes, etc. may be applied.

The water electrolysis cell may further include other components. Other components may be selected from known water electrolysis cell components. Other components include, for example, a cathode gas diffusion layer, a gasket, a sealing material, and the like.

For example, the electrolyte membrane may be selected from known electrolyte membranes (which may be ion exchange membranes) used for water electrolysis. The electrolyte membrane preferably has a property of selectively permeating protons (H ⁺ ). Examples of the electrolyte membrane include polymer electrolyte membranes (PEM). Examples of the polymer electrolyte membrane include perfluorocarbon membranes having sulfonic acid groups. Examples of perfluorocarbon membranes having sulfonic acid groups include Nafion membranes.

The electrolyte membrane is a polymer having proton conductivity due to having an ionic group, and may be, for example, either a fluoropolymer electrolyte or a hydrocarbon polymer electrolyte.

Here, the fluoropolymer electrolyte refers to a polymer in which most or all of the hydrogen atoms in alkyl groups and/or alkylene groups have been replaced with fluorine atoms. Representative examples of fluoropolymer electrolytes having ionic groups include "Nafion" (registered trademark) (manufactured by Chemours Corporation), "Aquivion" (registered trademark) (manufactured by Solvay), and "Flemion" (registered trademark). ) (manufactured by AGC Corporation) and "Aciplex" (registered trademark) (manufactured by Asahi Kasei Corporation).

As the hydrocarbon electrolyte, an aromatic hydrocarbon polymer having an aromatic ring in the main chain is preferred. Here, the aromatic ring includes not only a hydrocarbon aromatic ring consisting only of carbon atoms and hydrogen atoms such as a benzene ring and a naphthalene skeleton, but also a hetero ring such as a pyridine ring, an imidazole ring, and a thiol ring. good. Moreover, some aliphatic units may constitute the polymer together with the aromatic ring units.

Specific examples of aromatic hydrocarbon polymers include polysulfone, polyether sulfone, polyphenylene oxide, polyarylene ether, polyphenylene sulfide, polyphenylene sulfide sulfone, polyparaphenylene, polyarylene, polyarylene ketone, polyether ketone, and polyarylene phosphine. Examples include polymers having a structure selected from oxide, polyetherphosphine oxide, polybenzoxazole, polybenzthiazole, polybenzimidazole, polyamide, polyimide, polyetherimide, and polyimide sulfone in the main chain together with an aromatic ring. In addition, polysulfone, polyether sulfone, polyether ketone, etc. mentioned here are general terms for structures having sulfone bonds, ether bonds, ketone bonds, etc. in their molecular chains, and include polyether ketone ketone, polyether ether ketone, etc. , polyetheretherketoneketone, polyetherketoneetherketoneketone, polyetherketone sulfone, etc. The aromatic hydrocarbon polymer may have a plurality of these structures. Among these, as the aromatic hydrocarbon polymer, a polymer having a polyetherketone skeleton, that is, a polyetherketone polymer is particularly preferred.

The electrolyte membrane may be combined with a reinforcing material. By using the reinforcing material, for example, when the electrolyte membrane and the electrode are bonded together using a hot press method, gas leakage and short circuits within the electrode due to damage to the membrane are less likely to occur.

Specific examples of reinforcing materials include PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PVDF (polyvinylidene fluoride), and FEP (tetrafluoroethylene-hexafluoropropylene copolymer). fluorine-based polymers such as polymers such as PE (polyethylene), thermoplastic resins such as PP (polypropylene), PI (polyimide), PSF (polysulfone), PES (polyethersulfone), PEEK (polyetheretherketone), PPSS (polyphenylene sulfide sulfone), PPO (polyphenylene oxide), PEK (polyetherketone), PBI (polybenzimidazole), PPS (polyphenylene sulfide), PPP (polyparaphenylene), PPQ (polyphenylquinoxaline), polybenzoxazole ( Examples include homogeneous porous membranes made of engineering plastics such as PBO), polybenzothiazole (PBT), and polyparaphenylene terephthalamide (PPTA).

The anode catalyst and cathode catalyst may be selected from known catalysts used for water electrolysis. Examples of catalyst components include platinum, gold, silver, palladium, iridium, rhodium, ruthenium, tin, iron, cobalt, nickel, molybdenum, tungsten, vanadium, alloys thereof, and oxides thereof. The catalyst may be in the form of particles. Further, the anode catalyst may include a catalyst supported on a carrier. Examples of the carrier for the anode catalyst include metal oxides such as titanium oxide and tin oxide. The cathode catalyst may include a catalyst supported on a carrier. Examples of the carrier for the cathode catalyst include conductive carbon materials such as carbon black.

The water electrolysis cell may be equipped with an anode catalyst layer containing an anode catalyst (preferably anode catalyst particles) and an ionomer, and may be equipped with a cathode catalyst layer containing a cathode catalyst (preferably cathode catalyst particles) and an ionomer. . This increases the contact area between the catalyst and the ionomer within the catalyst layer, which tends to accelerate the reaction. Ionomers are materials that function as proton conductors. The anode catalyst layer and the cathode catalyst layer may be formed by being applied to an electrolyte membrane independently, or may be a layer formed by thermally transferring a layer applied to a base film to the electrolyte membrane. It's okay.

The arrangement of each component in the water electrolysis cell may be determined with reference to known water electrolysis cells. For example, an electrolyte membrane may be located between an anode catalyst and a cathode catalyst in at least a portion of the cross section of the water electrolysis cell. In the water electrolysis cell, the electrolyte membrane and the anode and cathode catalysts are preferably located between the anode gas diffusion layer and the cathode gas diffusion layer. In the water electrolysis cell, the electrolyte membrane, anode catalyst and cathode catalyst, and gas diffusion layer are preferably located between two separators.

An example of a water electrolysis cell is shown in FIG. FIG. 1 is a schematic cross-sectional view of a water electrolysis cell. As shown in FIG. 1, the water electrolysis cell 100 includes, in order from the top of FIG. 1, an anode separator 60, an anode gas diffusion layer 20, a catalyst coated membrane (CCM) 10, and a cathode gas diffusion layer. 30 and a cathode separator 70. The electrolyte membrane 10 with a catalyst layer is composed of an anode catalyst 12, an electrolyte membrane 11, and a cathode catalyst 13. Further, a gasket 40 is arranged between the anode separator 60 and the electrolyte membrane 11, and a gasket 50 is arranged between the cathode separator 70 and the electrolyte membrane 11.

It is preferable that at least one of the anode separator 60 and the anode gas diffusion layer 20 is made of the above-described water electrolysis cell member of the present disclosure. When the anode separator 60 is composed of the water electrolysis cell member of the present disclosure described above, the coating material is preferably located on the anode gas diffusion layer 20 side, and the anode gas diffusion layer 20 is the water electrolysis cell member of the present disclosure described above. In the case of a cell member, the coating material is preferably located on the anode catalyst 12 side.

<Water electrolysis device>
The water electrolysis device of the present disclosure will be described below.
The water electrolysis device of the present disclosure may be a water electrolysis cell stack formed by laminating a plurality of the water electrolysis cells of the present disclosure described above, and the water electrolysis cell stack or the water electrolysis cell of the present disclosure and other components. The device may be equipped with the following.

Other components may be selected from known water electrolysis device components. Other components include, for example, auxiliary equipment such as a power conditioner, water pump, ion exchange resin, heat exchanger, and dehumidifier.

Hereinafter, the present disclosure will be explained in detail with reference to Examples. However, the present disclosure is not limited to the following examples. The matters shown in the following examples may be changed as appropriate without departing from the spirit of the present disclosure.

<Example 1>
The base material was a Ti fiber sintered body (manufactured by Bekaert Japan Co., Ltd.) with a fiber diameter of 20 μm, a thickness of 200 μm, a porosity of 56%, and a vertical and horizontal length of 5 cm each. A base material) was prepared, and titanium nitride was prepared as a coating material for producing the coating material. After blasting the Ti fiber base material, titanium nitride was grown by a gas nitriding method to form a coating material made of titanium nitride (titanium nitride coating material) on the Ti fiber base material. The Ti fiber base material was placed in a chamber that allows gas ventilation, and after heating the sample to a temperature of 650° C., nitrogen gas was introduced into the chamber and nitriding treatment was performed for 20 hours.

After processing the cross section of the Ti fiber base material with the titanium nitride coating material, we used a scanning transmission electron microscope and an energy dispersive X-ray spectrometer (JSM-6510A manufactured by JEOL Ltd.) to examine the titanium nitride coating material. The thickness (nm) was measured. The thickness of the titanium nitride coating material was the average value of 10 randomly selected points. log{thickness of coating material (nm)}=3.46.

Next, an anode gas diffusion layer made of a Ti fiber base material provided with a titanium nitride coating material, an anode side separator (anode separator), an anode catalyst, a cathode catalyst, an electrolyte membrane, a cathode gas diffusion layer, and a cathode gas diffusion layer. side separator (cathode separator), anode side end plate, anode side current collector plate, anode side end plate, insulating sheet placed between the current collector plates, cathode side end plate, cathode side A water electrolysis cell was fabricated, including a current collector plate and an insulating sheet placed between the end plate on the cathode side and the current collector plate. As an anode separator, the vertical and horizontal lengths of the electrode installation part are each 5 cm, and 26 channels are arranged in parallel within an area of 5 cm on each side, each with a groove width of 1 mm and a depth of 2 mm. In addition, a titanium separator plated with Pt was used. As for the cathode separator, the vertical and horizontal lengths of the electrode installation part are each 5 cm, and 26 channels are arranged in parallel within an area of 5 cm on each side, each having a groove width of 1 mm and a depth of 2 mm. A carbon separator was used. A carbon material (manufactured by SGL Carbon Japan Co., Ltd.) was used as the cathode gas diffusion layer, and the layer was cut to have a vertical and horizontal length of 5 cm. As the electrolyte membrane with a catalyst layer, a commercially available product manufactured by FC Kaihatsu Co., Ltd. was used. The vertical and horizontal lengths of the anode and cathode are each 5 cm, and the anode catalyst is composed of a mixture of a catalyst powder containing iridium oxide and an ionomer, and the cathode catalyst is composed of a mixture of a Pt/C catalyst and an ionomer. For the anode and cathode gaskets, polytetrafluoroethylene (Teflon ^™ ) sheets with the electrode installation portions cut out were used. An anode made of a Ti fiber base material with an anode separator and a titanium nitride coating material, in which an electrode layer is arranged in the cutout part of the electrode installation part of the gasket, and the electrode installation part and the anode and cathode flow path overlap. A gas diffusion layer, an electrolyte membrane with a catalyst layer, a cathode gas diffusion layer, and a cathode separator were laminated. A water electrolysis cell was fabricated by laminating the anode and cathode separators in the order of current collector plate, insulating sheet, and end plate, and fastening them with bolts. The separator on the anode side was equipped with a water inlet and piping for discharging generated oxygen and unreacted water, and the separator on the cathode side was equipped with piping for discharging generated hydrogen. The anode and cathode current collector plates were each connected to an external power source (manufactured by Kikusui Electronics Co., Ltd., PWR2001L).

Water electrolysis was performed by applying a current to the water electrolysis cell described above under the following conditions.
Cell temperature: 60℃
Water flow rate: 100mL/min
Current density: 2000mA/ ^cm2
Water electrolysis time: 25 hours

After water electrolysis, the water electrolysis cell was disassembled, and the anode gas diffusion layer made of a Ti fiber base material provided with a titanium nitride coating material was taken out. After processing the thin film cross-section with a focused ion beam (FEI, Versa3D), we examined the Ti fiber base material using a combination of scanning transmission electron microscopy and energy dispersive X-ray spectrometer (JEOL Ltd., JEM-ARM200F). It was confirmed that a thin layer containing titanium and oxygen was formed at the interface of the titanium nitride coating material. This layer is presumed to be an oxygen-containing titanium layer formed by oxygen diffusion through grain boundaries in the titanium nitride coating material. The thickness of the titanium layer containing oxygen was the average value of five randomly extracted points. The thickness of the titanium layer containing oxygen was 5 nm.

<Example 2>
In the same manner as in Example 1, titanium nitride was grown on a Ti fiber base material by a gas nitriding method to form a titanium nitride coating material on the Ti fiber base material. The same procedure as in Example 1 was carried out except that the nitriding treatment time was 15 hours. log{thickness of coating material (nm)}=3.28.
Next, a water electrolysis cell was prepared in the same manner as in Example 1, and water electrolysis was performed in the same manner as in Example 1 except that the water electrolysis time was changed to 120 hours. The thickness of the titanium layer containing oxygen was 19 nm.

<Example 3>
In the same manner as in Example 1, titanium nitride was grown on a Ti fiber base material by a gas nitriding method to form a titanium nitride coating material on the Ti fiber base material. The same procedure as in Example 1 was carried out except that the nitriding treatment time was 8 hours. log{thickness of coating material (nm)}=3.02.
Next, a water electrolysis cell was prepared in the same manner as in Example 1, and water electrolysis was performed in the same manner as in Example 1 except that the water electrolysis time was changed to 200 hours. The thickness of the titanium layer containing oxygen was 32 nm.

<Example 4>
In the same manner as in Example 1, titanium nitride was grown on a Ti fiber base material by a gas nitriding method to form a titanium nitride coating material on the Ti fiber base material. The same procedure as in Example 1 was carried out except that the nitriding treatment time was 4 hours. log{thickness of coating material (nm)}=2.73.
Next, a water electrolysis cell was prepared in the same manner as in Example 1, and water electrolysis was performed in the same manner as in Example 1 except that the current density was changed to 4000 mA/cm ² and the water electrolysis time was changed to 120 hours. The thickness of the titanium layer containing oxygen was 48 nm.

<Example 5>
In the same manner as in Example 1, titanium nitride was grown on a Ti fiber base material by a gas nitriding method to form a titanium nitride coating material on the Ti fiber base material. The same procedure as in Example 1 was carried out except that the nitriding treatment time was 2 hours. log{thickness of coating material (nm)}=2.33.
Next, a water electrolysis cell was prepared in the same manner as in Example 1, except that the cell temperature was changed to 80° C., the current density was changed to 4000 mA/cm ² , and the water electrolysis time was changed to 120 hours. Water electrolysis was performed. The thickness of the titanium layer containing oxygen was 65 nm.

<Example 6>
Titanium nitride was deposited on the Ti fiber base material described in Example 1 by arc ion plating (AIP) to form a titanium nitride coating material on the Ti fiber base material. A base material made of a Ti fiber sintered body was placed in a chamber, and a bias power source and a process gas of nitrogen were each connected to the chamber. The substrate was heated to 200° C. and titanium nitride was deposited for a treatment time of 5 hours. The thickness of the titanium nitride coating material was evaluated by the method described in Example 1, and was found to be log{thickness of coating material (nm)}=3.01.
Next, a water electrolysis cell was prepared in the same manner as in Example 1, and water electrolysis was performed in the same manner as in Example 1 except that the water electrolysis time was changed to 120 hours. The thickness of the titanium layer containing oxygen was 20 nm.

<Example 7>
A Ti plate (manufactured by Nilaco) with a thickness of 1 mm was cut out so that the vertical and horizontal lengths were each 5 cm. A flow path was formed by etching to a depth of 300 μm based on the width of the grooves and peaks of the flow path of the anode separator described in Example 1, and a base material (Ti base material) was obtained. Titanium nitride was deposited on the Ti base material by the AIP method, and a coating material made of titanium nitride (titanium nitride coating material) was formed on the Ti base material. The procedure was the same as in Example 6 except that the substrate was heated to 650° C. and the treatment time was 8 hours. log{thickness of coating material (nm)}=3.02.
Next, a water electrolysis cell was produced. As the anode separator described in Example 1, a separator was used in which no flow path was formed and the vertical and horizontal lengths were each 5 mm so that a Ti base material on which titanium nitride was formed at a depth of 1 mm could be placed. Water electrolysis was carried out in the same manner as in Example 1, except that the anode gas diffusion layer was a Ti fiber sintered body with the titanium nitride coating material described in Example 1, and the water electrolysis time was changed to 120 hours. went. The thickness of the titanium layer containing oxygen was 20 nm.

<Comparative example 1>
In the same manner as in Example 6, titanium nitride was grown on the Ti fiber base material by the gas nitriding method to form a titanium nitride coating material on the Ti fiber base material. The same procedure as in Example 1 was carried out except that the nitriding treatment time was 40 hours. log{thickness of coating material (nm)}=3.63.
Next, a water electrolysis cell was prepared in the same manner as in Example 1, and water electrolysis was performed in the same manner as in Example 1 except that the water electrolysis time was changed to 120 hours. The thickness of the titanium layer containing oxygen was 112 nm.

<Comparative example 2>
In the same manner as in Example 6, titanium nitride was deposited by AIP method on a base material made of SUS316L plate (SUS base material), and a coating material made of titanium nitride (titanium nitride coating material) was deposited on the SUS316L base material. was formed. The same procedure as in Example 6 was carried out except that the treatment time was 25 hours. log{thickness of coating material (nm)}=3.64.
A water electrolysis cell was produced in the same manner as in Example 6 except that a SUS base material provided with a titanium nitride coating material was used and the water electrolysis time was 120 hours.

Regarding the water electrolysis cell after water electrolysis, it was confirmed in the same manner as in Example 1 that a thin layer was formed at the interface between the SUS base material and the titanium nitride coating material. This layer is presumed to be a titanium layer containing oxygen (Ti is derived from the titanium nitride coating material) formed by oxygen diffusion in the titanium nitride coating material. The thickness of the titanium layer containing oxygen was 94 nm.

<Comparative example 3>
A Ti fiber base material was prepared in the same manner as in Example 1, and platinum (Pt) was prepared as a coating material for producing a coating material. A Ti fiber base material was coated with Pt by a plating method. log{thickness of coating material (nm)}=2.29.
A water electrolysis cell was produced in the same manner as in Example 1, except that a Ti fiber base material with a Pt coating material was used as an anode gas diffusion layer, the cell temperature was 80 ° C., and the water electrolysis time was 120 hours. . The thickness of the titanium layer containing oxygen was 95 nm.

<Comparative example 4>
In the same manner as in Example 1, titanium nitride was grown on a Ti fiber base material by a gas nitriding method to form a titanium nitride coating material on the Ti fiber base material. The same procedure as in Example 1 was carried out except that the nitriding treatment time was 1 hour. log{thickness of coating material (nm)}=1.97.
Next, a water electrolysis cell was prepared in the same manner as in Example 1, and water electrolysis was performed in the same manner as in Example 1 except that the cell temperature was changed to 80° C. and the water electrolysis time was changed to 120 hours. The thickness of the titanium layer containing oxygen was 108 nm.

(Evaluation of peeling of coating material)
After the water electrolysis test, the water electrolysis cell was disassembled, and the surface of the anode catalyst layer was observed using a scanning transmission electron microscope and an energy dispersive X-ray spectrometer (JSM-6510A manufactured by JEOL Ltd.) to observe the fine structure and elements. By performing the analysis, it was confirmed whether the coating material was peeled off from the base material and transferred to the surface of the anode catalyst layer. If no transfer was observed, it was determined that the adhesion between the base material and the coating material was good.

(Crack evaluation)
For each Example and each Comparative Example, whether or not cracks were generated in the coating material was evaluated as follows. After the water electrolysis test, the water electrolysis cell was disassembled, and the surface of the anode catalyst layer was observed using a scanning transmission electron microscope and an energy dispersive X-ray spectrometer (JSM-6510A manufactured by JEOL Ltd.) to observe the fine structure and elements. By conducting an analysis, it was confirmed whether or not cracks had occurred in the coating material.

(Measurement of penetration resistance)
The penetration resistance of each Example and each Comparative Example was measured as follows.
First, as a measurement sample, a base material provided with the coating material after water electrolysis obtained in each Example and each Comparative Example was prepared. Each measurement sample (area 3.14 cm ^{2 , thickness 0.2 mm) was placed between two upper and lower electrodes (platinum foil, area 3.14 cm 2 )} electrically connected to a digital low resistance meter (Tsuruga Denki Co., Ltd., 3566). ) and pressurized to 1 MPa using a digital force gauge (model number: ZTA-1000N, manufactured by Imada Co., Ltd.). The resistance value at this time was read using a digital low resistance meter and was defined as the penetration resistance.

Table 1 shows the results of the evaluation of peeling of the coating material, crack evaluation, and measurement of penetration resistance in each Example and each Comparative Example.

As shown in Table 1, in Examples 1 to 7, Comparative Example 1, Comparative Example 2, and Comparative Example 4, in which a Ti fiber sintered body or a Ti plate using titanium nitride as the coating material, titanium nitride in the base material Almost no uncoated parts were observed. Furthermore, no peeling of the coating material was observed even after disassembling the water electrolysis cell, and the adhesion between the coating material and the base material was good. On the other hand, in Comparative Example 3 in which Pt was used as the coating material, many areas not covered with Pt were observed even after coating. After water electrolysis, peeling of the coating material from the base material was observed, indicating that the adhesion between the coating material and the base material was insufficient.

Furthermore, in Examples 1 to 7 and Comparative Example 4, no cracks were observed in the coating material, but in Comparative Example 1 and Comparative Example 2, cracks occurred in the coating material regardless of the type of base material. It was confirmed. This indicates that by increasing the thickness of the coating material, the stress generated within the coating material increased, causing cracks to occur. Since the thickness of the coating material of Comparative Example 1 in which cracks occurred was 4223 nm, it was found that cracks could be suppressed by being thinner than this.

FIG. 2 shows the results of evaluating the relationship between the penetration resistance of the coating material-coated substrates shown in Examples 1 to 7 and Comparative Examples 1 to 4 and the thickness of the oxygen-containing titanium layer. When Y is the penetration resistance and X is the thickness of the titanium layer containing oxygen, the following equation (1) is obtained by approximating with a quadratic function passing through the origin.
Y=0.0052X ² + 0.8627X...(1)
In Comparative Examples 1 and 2, in which the coating material had cracks, and in Comparative Example 3, in which the coating material was not coated before the water electrolysis test and the adhesion was insufficient, the thickness of the titanium layer containing oxygen was thick and there was no penetration. There was a lot of resistance. This means that in Examples 1 to 7, the thickness of the titanium layer containing oxygen, which induces an increase in penetration resistance, was suppressed to a small thickness, whereas in Comparative Examples 1 to 3, cracks, uncoated parts, etc. This indicates that a high-resistance oxygen-containing titanium layer was preferentially formed, increasing the thickness of the oxygen-containing titanium layer and causing an increase in penetration resistance. In Comparative Example 4, no cracks or peeling were observed in the coating material, but the oxygen-containing titanium layer was thick and the penetration resistance was high. Titanium nitride is a material with low electrical resistance, but water electrolysis turns it into a titanium layer that mostly contains oxygen, which is thought to be the cause of the increase in electrical resistance of the coating material. For this reason, the thickness of the titanium layer containing oxygen is preferably 78.7 nm so that the penetration resistance is 100 mΩ·cm ² or less. In order to reduce the resistance of the water electrolysis cell, the thickness is more preferably 45.5 nm or less so that the penetration resistance is 50 mΩ·cm ² or less, and more preferably 10.9 nm or less so that the penetration resistance is 10 mΩ·cm ² or less. I found it favorable.

FIG. 3 shows the results of evaluating the relationship between the penetration resistance of the coating material-coated substrates shown in Examples 1 to 7 and Comparative Examples 1 to 4 and the thickness of the coating material. Among these, for Examples 1 to 7 and Comparative Example 4, in which there were no peeling or cracks in the coating material, penetration resistance was set as Y, log{thickness of coating material (nm)} was set as Z, and approximated by a quadratic function. , the following equation (2) was obtained.
Y=55.594Z ² -398.13Z+718.78...(2)
If the thickness of the coating material is too thin, the penetration resistance increases because the proportion of the coating material occupied by the titanium layer containing high resistance oxygen increases. On the other hand, as shown in Comparative Examples 1 and 2, if the thickness of the coating material is too thick, cracks will occur, leading to high penetration resistance. From this, the thickness of the coating material is preferably 190 nm or more and 4223 nm or less so that the penetration resistance is 100 mΩ·cm ² or less. In order to reduce the resistance of the water electrolysis cell, it is more preferable that the thickness is 490 nm or more and 4223 nm or less so that the penetration resistance is 50 mΩ·cm ² or less, and it is more preferably 2042 nm or more and 4223 nm or less that the penetration resistance is 10 mΩ·cm ² or less. I found it favorable.

10: Electrolyte membrane with catalyst layer 11: Electrolyte membrane 12: Anode catalyst 13: Cathode catalyst 20: Anode gas diffusion layer 30: Cathode gas diffusion layer 40: Gasket 50: Gasket 60: Anode separator 70: Cathode separator 100: Cell

Claims (5)

A water electrolysis cell member that is at least one of an anode gas diffusion layer and a separator,
At least one base material of an anode gas diffusion layer base material and a separator base material;
a coating material containing conductive ceramics located on at least a portion of the surface of the base material;
a titanium layer containing oxygen located between the base material and the coating material,
The thickness of the titanium layer containing oxygen is 20 nm or less,
The thickness of the coating material is 1032 nm or more and 3000 nm or less,
The base material includes titanium,
The conductive ceramic is a member for a water electrolysis cell containing titanium nitride . The member for a water electrolysis cell according to claim 1, wherein the thickness of the titanium layer containing oxygen is 10.9 nm or less. The member for a water electrolysis cell according to claim 1, wherein the thickness of the coating material is 2042 nm or more and 3000 nm or less. A water electrolysis cell comprising a separator, an anode gas diffusion layer, an anode catalyst, a cathode catalyst, and an electrolyte membrane,
A water electrolysis cell, wherein at least one of the separator and the anode gas diffusion layer included in the water electrolysis cell is composed of the member for a water electrolysis cell according to any one of claims 1 to 3 . A water electrolysis cell stack formed by laminating a plurality of water electrolysis cells according to claim 4 .