Method for manufacturing catalyst film for water electrolysis cell and apparatus for manufacturing catalyst film

Abstract

Provided is a method for manufacturing a catalyst film for a water electrolysis cell, said method including: (1) a step for forming a metal-iridium-containing first film on a substrate by sputtering using a metal-iridium-containing target in a first space; and (2) a step for moving the substrate into a second space that contains oxygen plasma, oxidizing the first film, and forming an indium-oxide-containing first oxide film.

Description

Method for manufacturing a catalytic membrane for a water electrolysis cell and apparatus for manufacturing the catalytic membrane

[0001] The present invention relates to a method for producing a catalytic membrane for a water electrolysis cell.

[0002] In recent years, water electrolysis has been attracting attention as a hydrogen generation technology from the perspective of carbon neutrality.

[0003] In PEM (Proton Exchange Membrane) water electrolysis, which is one type of water electrolysis, protons (H ＋ The protons travel through a cation exchange membrane to the cathode where they are reduced, producing hydrogen.

[0004] Japanese Patent Application Laid-Open No. 2019-167620

[0005] In PEM water electrolysis, a catalyst is used to promote the proton generation reaction at the anode side. The raw material for this catalyst, iridium metal, is expensive, so reducing the manufacturing cost of water electrolysis cells is one of the challenges for practical application.

[0006] For example, Patent Document 1 proposes that, from the viewpoint of cost reduction, the catalyst be formed into a laminated structure of an iridium oxide layer and a void layer to increase the specific surface area, thereby reducing the amount of iridium oxide used.

[0007] However, even with this technology, it is difficult to say that the production cost of the catalyst has been reduced sufficiently, and there is still a demand for measures to effectively recycle metallic iridium and improve the "effective utilization rate" of metallic iridium.

[0008] The present invention has been made in view of the above background, and an object of the present invention is to provide a method for producing a catalyst membrane for a water electrolysis cell, which can significantly improve the "effective utilization rate" of metallic iridium.

[0009] Another object of the present invention is to provide an apparatus for producing such a catalyst film.

[0010] The present invention provides a method for producing a catalyst film for a water electrolysis cell, comprising the steps of: (1) sputtering a first film containing metallic iridium on a substrate in a first space using a target containing metallic iridium; and (2) moving the substrate to a second space containing oxygen plasma to oxidize the first film and form a first oxide film containing indium oxide.

[0011] The present invention also provides an apparatus for producing a catalytic film for a water electrolysis cell, comprising: a substrate holder accommodated in a processing chamber; the substrate holder is cylindrically configured with a central axis and an outer circumferential surface, and one or more substrates can be attached to the outer circumferential surface with a film-forming surface facing outward; and the substrate holder can rotate about the central axis; within the processing chamber, a plurality of spaces facing the substrate holder are arranged adjacent to each other along the direction of rotation of the substrate holder; the plurality of spaces include at least a first film-forming chamber and a first processing chamber; in the first film-forming chamber, a metallic iridium film can be sputter-formed on the film-forming surface of the substrate using a first target containing metallic iridium; and in the first processing chamber, the metallic iridium film can be oxidized by oxygen plasma to form a first oxide film; and by rotation of the substrate holder, the substrate can undergo successive formation of a metallic iridium film in the first film-forming chamber and formation of the first oxide film in the first processing chamber; The first film formation chamber is separated from an adjacent space by a partition plate, and at least a portion of the components released from the first target and not used in forming the metallic iridium film are attached to the partition plate in a metallic state.

[0012] The present invention provides a method for producing a catalytic membrane for a water electrolysis cell that can significantly improve the "effective utilization rate" of metallic iridium, and also provides an apparatus for producing such a catalytic membrane.

[0013] Fig. 1 is a diagram schematically showing a flow of a method for manufacturing a catalyst film according to one embodiment of the present invention; Fig. 2 is a diagram schematically showing a flow of another method for manufacturing a catalyst film according to one embodiment of the present invention; Fig. 3 is a diagram schematically showing a flow of yet another method for manufacturing a catalyst film according to one embodiment of the present invention; Fig. 4 is a diagram schematically showing a flow of yet another method for manufacturing a catalyst film according to one embodiment of the present invention; Fig. 5 is a diagram schematically showing an example of the configuration of an apparatus that can be used in the method for manufacturing a catalyst film according to one embodiment of the present invention.

[0014] An embodiment of the present invention will be described below.

[0015] As mentioned above, conventional methods for producing catalyst membranes for water electrolysis cells have the problem of high production costs.

[0016] For example, in a conventional method for manufacturing a catalytic film, a "reactive sputtering method" is used to form iridium oxide. In this method, a substrate and a metallic iridium target are placed in a chamber. The chamber is then controlled to an oxidizing environment, and the metallic iridium target is sputtered to form an iridium oxide film on the substrate.

[0017] In this method, some of the metallic iridium vapor scattered from the target is not used in film formation and instead adheres to the chamber walls, where it is oxidized by the environment and transformed into iridium oxide.

[0018] As a method for recycling iridium, a reduction and calcination method of iridium chloride is known. As described in a patent document (Japanese Patent No. 2505492), iridium oxide has the disadvantage of being less efficient at converting to iridium chloride than metallic iridium.

[0019] Thus, the conventional method has a problem in that the amount of iridium used in film formation relative to the amount of iridium consumed in the target, that is, the so-called "effective utilization rate," decreases.

[0020] In contrast, one embodiment of the present invention provides a method for producing a catalyst film for a water electrolysis cell, the method comprising the steps of: (1) in a first space, sputtering a first film containing metallic iridium onto a substrate using a target containing metallic iridium; and (2) moving the substrate to a second space containing oxygen plasma, and oxidizing the first film to form a first oxide film containing indium oxide.

[0021] In one embodiment of the present invention, a metallic iridium film is sputter deposited in a first space within a chamber, and then the metallic iridium film is oxidized in another space.

[0022] In this process, the iridium component that is scattered from the target in the first space and adheres to the chamber wall adheres to the chamber wall in a metallic state. Therefore, any iridium component that is not used in forming the metallic iridium film can be later recovered from the chamber wall in a metallic state. This recycling of metallic iridium results in an increased "effective utilization rate" of metallic iridium.

[0023] As a result, in one embodiment of the present invention, the manufacturing costs of catalysts for water splitting cells can be significantly reduced.

[0024] Furthermore, in the configuration obtained by one embodiment of the present invention, in which "a metallic iridium film is formed by sputtering in the first space," the metallic iridium film is formed to be sufficiently thin, and sufficient voids are formed within the film stack. As a result, the specific surface area of ​​the iridium oxide is large, and when applied as a catalyst for a water electrolysis cell, high electrolysis efficiency can be achieved even with a small amount of catalyst.

[0025] The above steps (1) and (2) may be repeated two or more times.

[0026] (Method for Producing a Catalyst Film According to an Embodiment of the Present Invention) Hereinafter, an example of a method for producing a catalyst film according to an embodiment of the present invention will be described in more detail with reference to the drawings.

[0027] FIG. 1 shows a schematic flow of a method for producing a catalyst film according to one embodiment of the present invention (hereinafter referred to as the "first method").

[0028] As shown in FIG. 1 , the first method includes: (A) a step of sputtering a first film containing metallic iridium on a substrate in a first space using a target containing metallic iridium (step S110); (B) a step of moving the substrate to a second space and sputtering a second metal film on the first film using a target containing a different metal (step S120); (C) a step of moving the substrate to a third space and oxidizing the first film and the second metal film with oxygen plasma to form a mixed oxide film containing iridium oxide and an oxide of the second metal (step S130); (D) a step of repeating steps (A) to (C) to form a film stack (step S140); and (E) a step of removing the oxide of the second metal from the mixed oxide film to form voids in the film stack (step S150).

[0029] However, steps S140 to S150 are steps that are performed as needed and are not essential steps.

[0030] Each step will be described below.

[0031] (Step S110) First, a substrate for film formation is prepared.

[0032] The type of substrate is not particularly limited. The substrate may be, for example, a porous substrate or an electrolyte membrane for a PEM water electrolysis cell. The porous substrate may be made of titanium. The electrolyte membrane may be, for example, a fluororesin having sulfonic acid groups (e.g., Nafion (trademark, manufactured by DuPont), Flemion (trademark, manufactured by Asahi Kasei), and Aciplex (trademark, manufactured by AGC).

[0033] The substrate is placed in a first space containing a first target containing metallic iridium.

[0034] Next, a first film containing metallic iridium is sputter-deposited on the substrate using a first target.

[0035] The sputtering conditions are not particularly limited as long as the environment is such that the first film is not oxidized. For example, the first space is a reduced pressure environment with a pressure in the range of 1 Pa to 2.0 Pa.

[0036] The substrate may be heated during film formation. Heating the substrate can enhance the crystallinity of the first film. The heating temperature is not limited to, but is in the range of 100°C to 1000°C, for example.

[0037] The thickness of the first film to be formed is, for example, in the range of 0.1 nm to 2.0 nm.

[0038] (Step S120) Next, the substrate is moved from the first space to a second space, which contains a second target containing a metal other than iridium (hereinafter referred to as the "second metal").

[0039] The second metal is, for example, selected from the group consisting of nickel, nickel-based materials, cobalt, and cobalt-based materials.

[0040] Next, a second film containing a second metal is sputter-deposited on the substrate using a second target.

[0041] The sputtering conditions are not particularly limited as long as the environment is such that the second film is not oxidized. For example, the second space is a reduced pressure environment with a pressure in the range of 0.1 Pa to 2.0 Pa.

[0042] In step S120, the substrate may be heated during film formation. The heating temperature is not limited to, but is in the range of 100°C to 1000°C, for example.

[0043] The thickness of the second film to be formed is, for example, in the range of 0.1 nm to 2 nm.

[0044] In addition, when the first film and the second film are sufficiently thin, the first film and the second film are substantially not in a laminated form but in a mixed form (i.e., a mixed film). Therefore, in the following description, an example will be described in which the first film and the second film exist in such a mixed form.

[0045] (Step S130) Next, the substrate is moved to a third space.

[0046] The third space is an oxidizing environment containing oxygen plasma, and therefore the first film and the second film on the substrate are oxidized in the third space to form a mixed oxide film containing iridium oxide and an oxide of the second metal.

[0047] (Step S140) Next, the above-described steps S110 to S130 are repeated as many times as necessary.

[0048] This results in a laminate of mixed oxide films being formed on the substrate.

[0049] The resulting laminate may be fired at a firing temperature ranging from 100°C to 1000°C, for example, but not limited to this.

[0050] (Step S150) Thereafter, if necessary, the oxide of the second metal is selectively removed from the mixed oxide film of the laminate.

[0051] The method for removing the second metal oxide is not particularly limited, and for example, the second metal oxide may be selectively removed by wet etching.

[0052] This allows voids to be formed within the film stack.

[0053] In the porous film laminate, the specific surface area of ​​the iridium oxide is large, and when applied as a catalyst for a water electrolysis cell, high electrolysis efficiency can be achieved even with a small amount of catalyst.

[0054] It should be noted that step S150 does not necessarily have to be performed consecutively after step S140. That is, step S150 may be performed before the film laminate obtained in step S140 is actually used as a catalyst.

[0055] In the first method, steps S110 and S120 are performed in separate spaces. Therefore, the iridium components scattered from the target and attached to the chamber wall in step S110 remain in a metallic state on the chamber wall. Therefore, the iridium not used in the film formation can be later recovered in a metallic state from the chamber wall and recycled.

[0056] As a result, the first method can significantly reduce the production costs of catalysts for water splitting cells.

[0057] (Another Method for Manufacturing a Catalyst Film According to an Embodiment of the Present Invention) Next, another method for manufacturing a catalyst film according to an embodiment of the present invention will be described.

[0058] FIG. 2 is a schematic diagram showing the flow of another method for producing a catalyst film according to one embodiment of the present invention (hereinafter referred to as the "second method").

[0059] As shown in FIG. 2 , the second method includes: (F) a step of sputtering a first film containing metallic iridium on a substrate in a first space using a target containing metallic iridium (step S210); (G) a step of moving the substrate to a second space and oxidizing the first film with oxygen plasma to form a first oxide film containing iridium oxide (step S220); and (H) a step of moving the substrate to a third space and sputtering a second metal film on the first oxide film using a target containing a second metal. (I) moving the substrate to a fourth space and oxidizing the second metal film with oxygen plasma to form a second oxide film (step S240); (J) repeating steps (F) to (I) to form a film stack including alternating layers of the first oxide film and the second oxide film on the substrate (step S250); and (K) removing the second oxide film to form an air gap layer in the film stack (step S260).

[0060] However, steps S250 to S260 are steps that are performed as needed and are not essential steps.

[0061] Each step will be described below.

[0062] (Step S210) For details of step S210, refer to step S110 in the first method described above, and therefore, no further description will be given here.

[0063] (Step S220) In the second method, after the first film is formed, the substrate is moved to a second space.

[0064] The second space is an oxidizing environment containing oxygen plasma, so that the first film on the substrate is oxidized in the second space to form a first oxide film containing iridium oxide.

[0065] (Step S230) Next, the substrate is moved to a third space.

[0066] The third space contains a second target containing a second metal.

[0067] The second metal is, for example, selected from the group consisting of nickel, nickel-based materials, cobalt, and cobalt-based materials.

[0068] Next, a second film containing a second metal is sputter-deposited using a second target.

[0069] The sputtering conditions are not particularly limited as long as the environment does not oxidize the second film.

[0070] The film forming conditions for the second film are the same as those described in step S120 of the first method, and will not be further described here.

[0071] (Step S240) Next, the substrate is moved to the fourth space.

[0072] The fourth space is an oxidizing environment containing oxygen plasma, so that the second film on the substrate is oxidized in the fourth space to form a second oxide film containing an oxide of the second metal.

[0073] (Step S250) Next, the above-described steps S210 to S240 are repeated as many times as necessary.

[0074] As a result, a film stack having a structure in which the first oxide film and the second oxide film are alternately repeated is formed on the substrate.

[0075] The resulting film stack may then be fired at a temperature ranging from 100°C to 1000°C, for example, but not limited to this.

[0076] (Step S260) Thereafter, if necessary, the second oxide film is selectively removed from the film stack. The method for removing the second oxide film is not particularly limited. For example, the second oxide film may be removed by any of the methods described in step S150 of the first method.

[0077] This allows a void layer to be formed within the film stack.

[0078] In the porous film laminate, the specific surface area of ​​the iridium oxide is large, and when applied as a catalyst for a water electrolysis cell, high electrolysis efficiency can be achieved even with a small amount of catalyst.

[0079] Similar to step S150 above, step S260 may be performed before the film stack is actually applied as a catalyst.

[0080] In the second method, steps S210 and S220 are also performed in separate spaces. Therefore, the iridium components scattered from the target and attached to the chamber wall in step S210 remain in a metallic state on the chamber wall. Therefore, the iridium not used in the film formation can be later recovered in a metallic state from the chamber wall.

[0081] As a result, the second method can significantly reduce the manufacturing costs of catalysts for water splitting cells.

[0082] In the above description, the second method includes a step (step S250) of forming a film stack including alternating layers of a first oxide film and a second oxide film by alternately repeating steps S210 to S240.

[0083] However, the second method is not limited to this. For example, steps S210 and S220 may be repeated to first form a first oxide film of a certain thickness, and then steps S230 and S240 may be repeated to form a second oxide film of a certain thickness. Then, step S250 may be performed to form a film stack in which the first oxide film and the second oxide film are alternately arranged.

[0084] Also, in the above description, in step S240, the second metal film is oxidized by oxygen plasma to form a second oxide film.

[0085] However, in step S240, the second metal film may be nitrided with nitrogen plasma to form a nitride film, or alternatively, in step S240, the second metal film may be treated with a mixed plasma of nitrogen and oxygen to form an oxynitride film.

[0086] In the second method, the number of materials to be laminated is not limited to two, and films of three or more different materials may be laminated.

[0087] (Yet Another Method for Manufacturing a Catalyst Film According to an Embodiment of the Present Invention) Next, yet another method for manufacturing a catalyst film according to an embodiment of the present invention will be described.

[0088] FIG. 3 is a schematic diagram showing the flow of yet another method for producing a catalyst film according to one embodiment of the present invention (hereinafter referred to as the "third method").

[0089] As shown in FIG. 3 , the third method includes: (L) a step of sputtering a first film containing metallic iridium on a substrate in a first space using a target containing metallic iridium (step S310); (M) a step of moving the substrate to a second space and oxidizing the first film with oxygen plasma to form a first oxide film containing iridium oxide (step S320); (N) a step of sputtering a second oxide film on the first oxide film using a metal oxide target (step S330); (O) a step of repeating steps (L) to (N) to form a film stack including alternating layers of the first oxide film and the second oxide film on the substrate (step S340); and (P) a step of removing the second oxide film to form a void layer in the film stack (step S350).

[0090] However, steps S340 to S350 are steps that are performed as needed and are not essential steps.

[0091] Each step will be described below.

[0092] (Step S310) to (Step S320) For details of steps S310 to S320, refer to steps S210 to S220 in the second method described above, and therefore will not be further described here.

[0093] (Step S330) Next, the substrate is moved to a third space.

[0094] The third space contains a metal oxide target, for example, selected from the group consisting of nickel oxide, nickel oxide-based materials, cobalt oxide, and cobalt oxide-based materials.

[0095] The element ratio (O / Ni) of oxygen (O) to nickel (Ni) in the nickel oxide target is preferably 0.5 or less.

[0096] The element ratio (O / Co) of oxygen to cobalt (Co) in the cobalt oxide target is preferably 1.0 or less.

[0097] A second oxide film is then sputter deposited using a metal oxide target.

[0098] The sputtering conditions are not particularly limited, but the third space is a reduced pressure environment with a pressure in the range of 0.1 Pa to 2.0 Pa, for example.

[0099] In step S330, the substrate may be heated during film formation. The heating temperature is not limited to, but is in the range of 100° C. to 1000° C., for example.

[0100] The thickness of the second oxide film is, but is not limited to, in the range of 10 nm to 100 nm, for example.

[0101] (Step S340) Next, the above-described steps S310 to S330 are repeated as many times as necessary.

[0102] As a result, a film stack having a structure in which the first oxide film and the second oxide film are alternately repeated is formed on the substrate.

[0103] The resulting film stack may be fired at a temperature ranging from 100°C to 1000°C, for example, but not limited to this.

[0104] (Step S350) Thereafter, if necessary, the second oxide film is selectively removed from the film stack. The method for removing the second oxide film is not particularly limited. For example, the second oxide film may be removed by any of the methods described in step S150 of the first method.

[0105] This allows a void layer to be formed within the film stack.

[0106] In the porous film laminate, the specific surface area of ​​the iridium oxide is large, and when applied as a catalyst for a water electrolysis cell, high electrolysis efficiency can be achieved even with a small amount of catalyst.

[0107] It should be noted that step S350 may be performed before the film stack is actually applied as a catalyst.

[0108] In the third method, steps S310 and S320 are also performed in separate spaces. Therefore, the iridium components scattered from the target and attached to the chamber wall in step S310 remain in a metallic state on the chamber wall. Therefore, the iridium not used in the film formation can be later recovered in a metallic state from the chamber wall.

[0109] As a result, the third method can significantly reduce the manufacturing costs of catalysts for water splitting cells.

[0110] In the above description, the third method includes a step (step S340) of forming a film stack including alternating layers of a first oxide film and a second oxide film by alternately repeating steps S310 to S330.

[0111] However, the third method is not limited to this. For example, steps S310 and S320 may be repeated to first form a first oxide film of a certain thickness, and then step S330 may be performed. Then, step S340 may be performed to form a film stack in which the first oxide film and the second oxide film are alternately arranged.

[0112] In the above description, a second oxide film is formed on the first oxide film using a metal oxide target other than iridium oxide in step S330. However, the third method is not limited to this. For example, a nitride film or an oxynitride film may be formed instead of the second oxide film in step S330. In this case, a film stack including alternating layers of the first oxide film and the nitride film or the oxynitride film is formed in step S340. Thereafter, in step S350, the nitride film or the oxynitride film may be selectively removed to form an air gap layer within the film stack.

[0113] (Yet Another Method for Manufacturing a Catalyst Film According to an Embodiment of the Present Invention) Next, yet another method for manufacturing a catalyst film according to an embodiment of the present invention will be described.

[0114] FIG. 4 is a schematic diagram showing the flow of yet another method for producing a catalyst film according to one embodiment of the present invention (hereinafter referred to as the "fourth method").

[0115] As shown in FIG. 4 , the fourth method includes: (Q) a step of sputtering a first film containing metallic iridium on a substrate in a first space using a target containing metallic iridium (step S410); (R) a step of moving the substrate to a second space and oxidizing the first film with oxygen plasma to form a first oxide film containing iridium oxide (step S420); (S) a step of moving the substrate to a third space and evaporating a third material having proton conductivity on the first oxide film to form a third film (step S430); and (T) a step of repeating steps (Q) to (S) to form a film stack on the substrate including alternating layers of the first oxide film and the third material (step S440).

[0116] However, step S440 is a step that is performed as needed and is not an essential step.

[0117] Each step will be described below.

[0118] (Step S410) to (Step S420) For details of steps S410 to S420, refer to steps S210 to S220 in the second method described above, and therefore will not be further described here.

[0119] (Step S430) Next, the substrate is moved to a third space.

[0120] In the third space, a third material is vapor-deposited on the first film to form a third film.

[0121] The third material is selected from materials having proton conductivity. For example, the third material may be a fluororesin having a sulfonic acid group (e.g., Nafion (trademark, manufactured by DuPont), Flemion (trademark, manufactured by Asahi Kasei), and Aciplex (trademark, manufactured by AGC).

[0122] As a result, an electrolyte membrane having proton conductivity is formed as the third membrane.

[0123] The thickness of the third film is, but is not limited to, in the range of 10 nm to 100 nm, for example.

[0124] (Step S440) Next, the above-described steps S410 to S430 are repeated as many times as necessary.

[0125] As a result, a film stack having a structure in which the first oxide film and the third film are alternately repeated is formed on the substrate.

[0126] In the fourth method, steps S410 and S420 are also performed in separate spaces. Therefore, the iridium components scattered from the target and attached to the chamber wall in step S410 remain in a metallic state on the chamber wall. Therefore, the iridium not used in the film formation can be later recovered in a metallic state from the chamber wall.

[0127] As a result, the fourth method can significantly reduce the manufacturing costs of catalysts for water splitting cells.

[0128] (Apparatus for Implementing a Method According to an Embodiment of the Present Invention) Next, with reference to FIG. 5, an example of the configuration of an apparatus for implementing a method according to an embodiment of the present invention will be described.

[0129] Here, the configuration and operation of the apparatus will be described using the second method described above as an example for producing a film stack, although it will be clear to those skilled in the art that the apparatus described below can also be used to carry out methods other than the second method by modifying some of its configuration.

[0130] FIG. 5 is a schematic diagram showing an example of the configuration of an apparatus used in the second method.

[0131] As shown in FIG. 5, the apparatus 100 includes a processing chamber 115, and a substrate holder 120, a film forming chamber 127, and a processing chamber 170 housed in the processing chamber.

[0132] 5, two film formation chambers 127 are formed facing each other, and are referred to herein as first and second film formation chambers 127A and 127B, respectively. Similarly, two processing chambers 170 are formed facing each other, and are referred to herein as first and second processing chambers 170A and 170B, respectively. Therefore, the processing chamber 115 is partitioned clockwise into a first film formation chamber 127A, a first processing chamber 170A, a second film formation chamber 127B, and a second processing chamber 170B.

[0133] The substrate holder 120 serves to hold a substrate W on which a film is to be formed. The substrate holder 120 is cylindrical and has a central axis C that extends in the vertical direction (the Z direction in FIG. 5 ). The substrate holder 120 is housed in the processing chamber 115 so that the central axis C is positioned approximately in the center of the processing chamber 115.

[0134] The substrate holder 120 also has an outer circumferential surface 123 centered on the central axis C (Z direction). A plurality of substrates W can be mounted on this outer circumferential surface 123 using fixing means such as bolts.

[0135] The first film formation chamber 127A in the processing chamber 115 is partitioned by two partition plates 129, one end of which is fixed to the side wall of the processing chamber 115. The other ends of both partition plates 129 are disposed facing the substrate holder 120. Each partition plate 129 extends in the direction of the central axis C of the substrate holder 120. Therefore, the first film formation chamber 127A also extends in the direction of the central axis C.

[0136] A first target 130A for film formation is disposed on the sidewall side of the processing chamber 115 of the first film formation chamber 127A. An electrode (not shown) or the like is disposed on the rear surface of the first target 130A, i.e., on the sidewall side of the processing chamber 115.

[0137] The first target 130A is a metallic iridium target, so that a metallic iridium film (first film) can be formed by sputtering in the first film formation chamber 127A.

[0138] The second film formation chamber 127B has a configuration similar to that of the first film formation chamber 127A. However, a second target 130B is disposed in the second film formation chamber 127B. The second target 130B is composed of a second metal other than iridium. Therefore, in the second film formation chamber 127B, a film of the second metal (second film) is sputter-deposited. As described above, the second metal is selected from nickel, a material mainly composed of nickel, cobalt, and a material mainly composed of cobalt.

[0139] The processing chamber 170 is provided to oxidize the film formed in the film formation chamber 127 .

[0140] For example, in the first processing chamber 170A, the first film is oxidized by oxygen plasma, and in the second processing chamber 170B, the second film is oxidized by oxygen plasma.

[0141] When manufacturing a film stack using such an apparatus 100, first, substrates W are placed on the outer peripheral surface 123 of the substrate holder 120. For example, in the example shown in FIG.

[0142] The substrate W is held by the substrate holder 120 so that the first main surface 179 and the second main surface (corresponding to the "deposition surface" on which the film is formed) 180 extend along the direction of the central axis C of the substrate holder 120.

[0143] The substrate W may be, for example, a porous titanium substrate or an electrolyte membrane having proton conductivity.

[0144] If necessary, the substrate W may be heated to a heating temperature in the range of 100°C to 600°C, for example.

[0145] Next, a vacuum is created inside the processing chamber 115. For example, the pressure in the first deposition chamber 127A and the second deposition chamber 127B may be in the range of 0.3 Pa to 2.0 Pa.

[0146] 5, the substrate holder 120 is then rotated about the central axis C. This causes the substrate W to also rotate about the central axis C. The rotation speed may be, for example, in the range of 50 rpm to 200 rpm.

[0147] Next, in the first film formation chamber 127A, sputtering is performed on the first target 130A, thereby forming a first film on the substrate W in the first film formation chamber 127A.

[0148] Since the substrate W rotates clockwise together with the substrate holder 120, the substrate on which the first film is formed is then moved to the first processing chamber 170A. In the first processing chamber 170A, the first film is oxidized by oxygen plasma to form a first oxide film.

[0149] Next, the substrate W is moved to the second film formation chamber 127B by the rotation of the substrate holder 120. In the second film formation chamber 127B, sputtering is performed on the second target 130B. As a result, a second film is formed on the substrate W in the second film formation chamber 127B.

[0150] The substrate is then moved to the second processing chamber 170B, where the second film is oxidized by oxygen plasma to form a second oxide film.

[0151] In this way, by repeatedly passing through the first film formation chamber 127A, the first processing chamber 170A, the second film formation chamber 127B, and the first processing chamber 170B, a film stack in which first oxide films and second oxide films are arranged alternately can be formed on the second main surface 180 of the substrate W.

[0152] Furthermore, in the apparatus 100, the thickness and oxidation state of the first film can be adjusted by controlling the rotation speed of the substrate holder 120. For example, when the substrate holder 120 is rotated at a high speed, such as 100 rpm, an oxygen-deficient iridium oxide film can be formed. For example, a first film having an iridium to oxygen ratio (O / Ir ratio) of 1.0 or more and less than 2.0 can be formed.

[0153] In the apparatus 100, the first film formation chamber 127A is separated from the first processing chamber 170A. Therefore, in the first film formation chamber 127, the iridium component that is emitted from the first target 130A and is not used in film formation on the substrate W is attached in a metallic state to the two partition plates 129 that separate the first film formation chamber 127.

[0154] Therefore, after using the apparatus 100, the partition plate 129 is removed from the processing chamber 115, and the metallic iridium that was not used in film formation can be easily recovered by peeling off the metallic iridium from the surface of the partition plate 129.

[0155] The recovered metallic iridium can be recovered by a recovery method such as wet treatment, in which the iridium is dissolved in an acidic solution such as hydrochloric acid or chlorine, and the resulting solution is then subjected to reduction firing.

[0156] The method for manufacturing a film stack by the second method has been described above using the apparatus 100 as an example, but it will be apparent to those skilled in the art that the first and third methods can also be implemented using a similar apparatus.

[0157] For example, the first method can be implemented in the apparatus 100 by omitting the first treatment chamber 170A and rotating the substrate holder 120 at high speed. Alternatively, the third method can be implemented in the apparatus 100 by placing an oxide target in the second deposition chamber 127B and omitting the second treatment chamber 170B.

[0158] It will be apparent to those skilled in the art that the film stack can be manufactured in various other ways.

[0159] (Membrane laminate according to one embodiment of the present invention) Next, the characteristics of the catalyst obtained by the method for producing a catalyst membrane for a water electrolysis cell according to one embodiment of the present invention as described above will be described.

[0160] As an example, the characteristics of a film stack (hereinafter referred to as the "first film stack") manufactured by the second method described above and having a void layer formed by performing step S260 will be described.

[0161] The first film stack includes a plurality of iridium oxide layers.

[0162] Each iridium oxide layer may have a ratio of iridium to oxygen (O / Ir ratio) that deviates from the stoichiometric composition. For example, the Ir / O ratio may be equal to or greater than 1.0 and less than 2.0.

[0163] An iridium oxide layer having such a composition tends to be easily obtained in the above-described apparatus 100 when the oxygen concentration in the second processing chamber is reduced or when the power density of the plasma source in the second processing chamber is reduced.

[0164] Furthermore, in the first film laminate, when measured by XRD using the θ-2θ method, the peak intensity ratio of any one of diffraction peak 1A derived from the Ir(111) plane, diffraction peak 2A derived from the Ir(101) plane, diffraction peak 3A derived from the Ir(220) plane, and diffraction peak 4A derived from the Ir(200) plane may be 9 / 10 or more of the total peak intensity ratios of peaks 1A to 4A.

[0165] Furthermore, the first film laminate may have a full width at half maximum of 1 degree or less for any of diffraction peaks 1A derived from the Ir(111) plane, diffraction peak 2A derived from the Ir(101) plane, diffraction peak 3A derived from the Ir(220) plane, and diffraction peak 4A derived from the Ir(200) plane, as measured by XRD using the θ-2θ method.

[0166] Furthermore, the larger the specific surface area of ​​the first film laminate, the more preferable it is.

[0167] The first membrane stack may also be formed on an anode for a water electrolysis cell, or on an electrolyte membrane having proton conductivity.

[0168] (Aspects of the present invention) Aspects of the present invention will be described below.

[0169] (Aspect 1) A method for producing a catalyst film for a water electrolysis cell, the method comprising: (1) in a first space, sputtering a first film containing metallic iridium onto a substrate using a target containing metallic iridium; and (2) moving the substrate to a second space containing oxygen plasma to oxidize the first film and form a first oxide film containing indium oxide.

[0170] (Aspect 2) The method according to aspect 1, wherein steps (1) and (2) are repeated.

[0171] (Aspect 3) The method according to aspect 1 or 2, wherein the method is carried out in a state where the substrate is heated.

[0172] (Aspect 4) The method according to any one of Aspects 1 to 3, wherein the step (1) is carried out at a pressure in the range of 0.1 Pa to 2.0 Pa.

[0173] (Aspect 5) The method according to any one of Aspects 1 to 4, further comprising: (3) after step (1), moving the substrate to a third space and sputtering a second metal film on the substrate using a target containing a second metal, the second metal being selected from the group consisting of nickel, a nickel-based material, cobalt, and a cobalt-based material; and in step (2), the first film and the second metal film are oxidized together to form a mixed oxide film containing iridium oxide and an oxide of the second metal.

[0174] (Aspect 6) The method according to aspect 5, further comprising: (4) repeating steps (1), (3), and (2) to form a film stack.

[0175] (Aspect 7) The method of aspect 6, further comprising: (5) selectively removing the oxide of the second metal from the mixed oxide film to form voids within the film stack.

[0176] (Aspect 8) The method according to any one of Aspects 1 to 4, further comprising, after step (2), the steps of: (6-1) sputtering a second metal film on the first oxide film using a target containing a second metal, the second metal being selected from the group consisting of nickel, a nickel-based material, cobalt, and a cobalt-based material; (6-2) oxidizing the second metal film to form a second oxide film; and (6-3) repeating steps (1), (2), (6-1), and (6-2) to form a film stack including alternating layers of the first oxide film and the second oxide film on the substrate.

[0177] (Aspect 9) The method according to aspect 8, wherein the step (6-1) is performed after the steps (1) and (2) are repeated, and the step (6-3) is performed after the steps (6-1) and (6-2) are repeated.

[0178] (Aspect 10) The method according to any one of Aspects 1 to 4, further comprising, after step (2), (7-1) a step of sputtering a second oxide film on the first oxide film using a metal oxide target, wherein the metal oxide is selected from the group consisting of nickel oxide, a material mainly composed of nickel oxide, cobalt oxide, and a material mainly composed of cobalt oxide; and (7-2) a step of repeating steps (1), (2), and (7-1) to form a film stack including alternating layers of the first oxide film and the second oxide film on the substrate.

[0179] (Aspect 11) The method according to aspect 10, wherein the step (7-1) is carried out after the steps (1) and (2) are repeated.

[0180] (Aspect 12) The method according to aspect 8 or 10, further comprising the step of: (8) removing the second oxide film to form an air gap layer within the film stack.

[0181] (Aspect 13) The method according to any one of Aspects 1 to 12, wherein the method is carried out in a single chamber having a plurality of partitioned spaces.

[0182] (Aspect 14) The method according to aspect 13, wherein a rotatable substrate holder having the substrate attached thereto is disposed within the chamber, and the method is performed by rotating the substrate holder.

[0183] (Aspect 15) The method according to any one of Aspects 1 to 14, wherein in (1), at least a portion of the metallic iridium component released from the target and not used in forming the first film is recovered in a metallic state.

[0184] (Aspect 16) The method according to any one of Aspects 1 to 4, further comprising, after the step (2), the steps of: (9-1) depositing a third material having proton conductivity to form a third film; and (9-2) repeating the steps (1), (2), and (9-1) to form a film stack including alternating layers of the first oxide film and the third film on the substrate.

[0185] (Aspect 17) The method according to any one of aspects 1 to 16, wherein the substrate is a substrate containing titanium or an electrolyte membrane for a water electrolysis cell.

[0186] (Aspect 18) An apparatus for producing a catalyst film for a water electrolysis cell, comprising: a substrate holder accommodated in a processing chamber; the substrate holder is cylindrically configured with a central axis and an outer circumferential surface, and one or more substrates can be attached to the outer circumferential surface with a film-forming surface facing outward; and the substrate holder can rotate about the central axis; within the processing chamber, a plurality of spaces facing the substrate holder are arranged adjacent to each other along a direction of rotation of the substrate holder; the plurality of spaces include at least a first film-forming chamber and a first processing chamber; in the first film-forming chamber, a metal iridium film can be sputter-formed on the film-forming surface of the substrate using a first target containing metal iridium; and in the first processing chamber, the metal iridium film can be oxidized by oxygen plasma to form a first oxide film; and by rotation of the substrate holder, the substrate can undergo successive formation of a metal iridium film in the first film-forming chamber and formation of the first oxide film in the first processing chamber, The first film formation chamber is separated from an adjacent space by a partition plate, and at least a portion of the components released from the first target and not used in forming the metallic iridium film are attached to the partition plate in a metallic state.

[0187] This application claims priority based on Japanese Patent Application No. 2024-047804, filed on March 25, 2024, the entire contents of which are incorporated herein by reference.

[0188] 100 Apparatus 115 Processing chamber 120 Substrate holder 123 Outer circumferential surface 127 (127A, 127B) Film formation chamber (first film formation chamber, second film formation chamber) 129 Partition plate 130A First target 130B Second target 170 (170A, 170B Processing chamber (first processing chamber, second processing chamber)) 179 First main surface 180 Second main surface C Central axis W Substrate

Claims

1. A method for producing a catalyst film for a water electrolysis cell, comprising: (1) in a first space, sputtering a first film containing metallic iridium onto a substrate using a target containing metallic iridium; and (2) moving the substrate to a second space containing oxygen plasma to oxidize the first film and form a first oxide film containing indium oxide.

2. The method of claim 1, wherein steps (1) and (2) are repeated.

3. The method of claim 1, wherein the method is carried out while the substrate is heated.

4. The method according to claim 1, wherein step (1) is carried out at a pressure in the range of 0.1 Pa to 2.0 Pa.

5. The method of claim 1, further comprising the step of: (3) after step (1), moving the substrate to a third space and sputtering a second metal film on the substrate using a target containing a second metal, the second metal being selected from the group consisting of nickel, a nickel-based material, cobalt, and a cobalt-based material; and in step (2), the first film and the second metal film are oxidized together to form a mixed oxide film containing iridium oxide and an oxide of the second metal.

6. The method of claim 5, further comprising: (4) repeating steps (1), (3) and (2) to form a film stack.

7. The method of claim 6, further comprising the step of: (5) selectively removing the oxide of the second metal from the mixed oxide film to form voids within the film stack.

8. The method of claim 1, further comprising, after step (2), the steps of: (6-1) sputtering a second metal film on the first oxide film using a target containing a second metal, the second metal being selected from the group consisting of nickel, a nickel-based material, cobalt, and a cobalt-based material; (6-2) oxidizing the second metal film to form a second oxide film; and (6-3) repeating steps (1), (2), (6-1), and (6-2) to form a film stack on the substrate including alternating layers of the first oxide film and the second oxide film.

9. The method of claim 8, wherein step (6-1) is performed after steps (1) and (2) are repeated, and step (6-3) is performed after steps (6-1) and (6-2) are repeated.

10. The method of claim 1, further comprising, after step (2), the steps of: (7-1) sputtering a second oxide film on the first oxide film using a metal oxide target, wherein the metal oxide is selected from the group consisting of nickel oxide, a material mainly composed of nickel oxide, cobalt oxide, and a material mainly composed of cobalt oxide; and (7-2) repeating steps (1), (2), and (7-1) to form a film stack including alternating layers of the first oxide film and the second oxide film on the substrate.

11. The method according to claim 10, wherein the step (7-1) is performed after the steps (1) and (2) are repeated.

12. The method of claim 8 or 10, further comprising the step of: (8) removing the second oxide film to form an air gap layer within the film stack.

13. The method of claim 8 or 11, wherein the method is carried out in a single chamber having a plurality of partitioned spaces.

14. The method of claim 13, wherein a rotatable substrate holder having the substrate attached thereto is disposed within the chamber, and the method is carried out by rotating the substrate holder.

15. The method according to claim 1, wherein in (1), at least a portion of the metallic iridium component that is released from the target and not used in forming the first film is recovered in a metallic state.

16. The method of claim 1, further comprising, after step (2), (9-1) depositing a third material having proton conductivity to form a third film, and (9-2) repeating steps (1), (2), and (9-1) to form a film stack including alternating layers of the first oxide film and the third film on the substrate.

17. The method of claim 1, wherein the substrate is a titanium-containing substrate or an electrolyte membrane for a water electrolysis cell.

18. An apparatus for producing a catalytic film for a water electrolysis cell, comprising: a substrate holder accommodated in a processing chamber; the substrate holder is cylindrically configured with a central axis and an outer circumferential surface; one or more substrates can be attached to the outer circumferential surface with the surface to be coated facing outward; the substrate holder can rotate about the central axis; within the processing chamber, a plurality of spaces facing the substrate holder are arranged adjacent to each other along the direction of rotation of the substrate holder; the plurality of spaces have at least a first film-forming chamber and a first processing chamber; in the first film-forming chamber, a metallic iridium film can be sputter-formed on the surface to be coated of the substrate using a first target containing metallic iridium; in the first processing chamber, the metallic iridium film can be oxidized by oxygen plasma to form a first oxide film; and by rotation of the substrate holder, the substrate can be subjected to the formation of a metallic iridium film in the first film-forming chamber and the formation of the first oxide film in the first processing chamber successively; The first film formation chamber is separated from an adjacent space by a partition plate, and at least a portion of the components released from the first target and not used in forming the metallic iridium film are attached to the partition plate in a metallic state.

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