EP4640924A1

EP4640924A1 - Electrochemical cell and electrolytic device

Info

Publication number: EP4640924A1
Application number: EP23924177.1A
Authority: EP
Inventors: Hidehiko Tajima; Naoto Tagami; Kosuke INABA; Shoichi Furukawa; Shigeru Tsurumaki; Daisuke Mukai
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 2023-02-22
Filing date: 2023-11-10
Publication date: 2025-10-29
Also published as: JP2024119282A; EP4640924A4; JP7843723B2; WO2024176533A1; TW202444968A; TWI900937B; AU2023432785A1

Abstract

An electrochemical cell according to the present disclosure includes: an ion-exchange membrane; a cathode catalyst layer disposed further toward one side than the ion-exchange membrane; an anode catalyst layer disposed further toward the other side, opposite to the one side, than the ion-exchange membrane; and a ceramic-particle-containing layer disposed between the cathode catalyst layer and the ion-exchange membrane, and/or between the anode catalyst layer and the ion-exchange membrane.

Description

Technical Field

The present disclosure relates to an electrochemical cell and an electrolyzer.
This application claims priority from Japanese Patent Application No. 2023-026068 filed in Japan on February 22, 2023 , the contents of which are incorporated herein by reference.

Background Art

Patent Document 1 discloses a membrane electrode assembly (MEA) including two macroporous carbon-based backing layers, an ionomer layer (ion-exchange membrane) disposed between the two macroporous carbon-based backing layers, and a layer structure in which a catalyst layer (electrode catalyst layer), a barrier layer, and a microporous layer are disposed between the macroporous carbon-based backing layer and the ionomer layer in order from the ionomer layer side. The catalyst layer is joined to both surfaces of the ionomer layer.

Citation List

Patent Document

Patent Document 1: JP 6430969 B2

Summary of Invention

Technical Problem

In the field of electrochemical cells including a membrane electrode assembly, there may be a case where an electrode catalyst layer in contact with an ion-exchange membrane is formed to have a rough surface. Therefore, portions where the electrode catalyst layer is in close contact with the ion-exchange membrane and portions where the electrode catalyst layer is not in close contact with the ion-exchange membrane are sparsely present in some cases. In order to inhibit concentration of contact resistance at the close contact portion, a surface pressure may be imparted to the ion-exchange membrane from the electrode catalyst layer side. However, in this case, depending on the magnitude of the imparted surface pressure, there may be a case where defects such as damage occur in the ion-exchange membrane due to the roughness of the surface of the electrode catalyst layer.
The present disclosure has been made to solve the issue described above, and an object thereof is to provide an electrochemical cell and an electrolyzer in each of which defects are less likely to occur even a large surface pressure is imparted.

Solution to Problem

In order to solve the issue described above, an electrochemical cell according to the present disclosure includes an ion-exchange membrane, a cathode catalyst layer disposed further toward one side than the ion-exchange membrane, an anode catalyst layer disposed further toward the other side, opposite to the one side, than the ion-exchange membrane, and a ceramic-particle-containing layer disposed between the cathode catalyst layer and the ion-exchange membrane, and/or between the anode catalyst layer and the ion-exchange membrane.
An electrolyzer according to the present disclosure includes an electrolysis cell, which is the electrochemical cell, an electrolyte supply unit that supplies an electrolyte to the electrolysis cell, and a power supply unit that applies voltage to the electrolysis cell.

Advantageous Effects of Invention

According to the present disclosure, it is possible to provide an electrochemical cell and an electrolyzer in each of which defects are less likely to occur even when a large surface pressure is imparted.

Brief Description of Drawings

FIG. 1 is a schematic configuration diagram illustrating an overall configuration of an electrolyzer according to a first embodiment of the present disclosure.
FIG. 2 is a diagram schematically illustrating an electrochemical cell according to the first embodiment of the present disclosure.
FIG. 3 is a diagram schematically illustrating a cross section of a ceramic-particle-containing layer according to the first embodiment of the present disclosure.
FIG. 4 is an exploded perspective view schematically illustrating an electrochemical cell according to the first embodiment of the present disclosure.
FIG. 5 is a cross-sectional view illustrating the electrochemical cell according to the first embodiment of the present disclosure.
FIG. 6 is a diagram (cross-sectional view) for describing a pressing mechanism according to the first embodiment of the present disclosure.
FIG. 7 is a cross-sectional view illustrating a method of manufacturing a membrane electrode assembly according to the first embodiment of the present disclosure.
FIG. 8 is a cross-sectional view illustrating a method of manufacturing a membrane electrode assembly according to a second embodiment of the present disclosure.
FIG. 9 is a cross-sectional view illustrating a method of manufacturing a membrane electrode assembly according to a third embodiment of the present disclosure.
FIG. 10 is a diagram illustrating a relationship between a surface pressure and a contact resistance in comparison between a case where a ceramic-particle-containing layer according to the embodiment of the present disclosure is present and a case where the ceramic-particle-containing layer is not present.
FIG. 11 is a diagram illustrating a relationship between a current density and a cell voltage in comparison between a case where the ceramic-particle-containing layer according to the embodiment of the present disclosure is present and a case where the ceramic-particle-containing layer is not present.

Description of Embodiments

Hereinafter, an electrolyzer 1 according to an embodiment of the present disclosure and a method of manufacturing a membrane electrode assembly 43 included in the electrolyzer 1 will be described with reference to the drawings. In the following description, components having the same or similar functions are denoted by the same reference numerals. As used herein "facing toward" means that two members overlap when viewed in a certain direction, and may include a case where another member (for example, another layer) presents between the two members.
Referring to FIG. 5, Z direction, X direction, and Y direction are defined. The Z direction is a direction (left-right direction in FIG. 5) from a first separator 41 toward a second separator 42 to be described later. The Z direction is also a layering direction when an ion-exchange membrane 50, a ceramic-particle-containing layer 51, a cathode catalyst layer 54, a cathode power feeder 55, an anode catalyst layer 56, and an anode power feeder 57 of a membrane electrode assembly 43 described later form a layer structure. The X direction is a direction intersecting (for example, orthogonal to) the Z direction, and is a direction from a central region C of the membrane electrode assembly 43 toward one end portion of the membrane electrode assembly 43 (vertical direction in FIG. 5). The Y direction is a direction intersecting (for example, orthogonal to) the Z direction and the X direction, and is, for example, a direction perpendicular to the plane of FIG. 5. The term "area" as used herein means an area as viewed in the Z direction (that is, an area extending in the X direction and the Y direction). In addition, the "outline size" in the present specification means an outline size as viewed in the Z direction. That is, the "outline size" and the "area" may mean substantially the same in some cases, and they may be read interchangeably as appropriate.

First Embodiment

FIG. 1 is a schematic configuration diagram illustrating an overall configuration of an electrolyzer 1 of a first embodiment. In the present embodiment, the electrolyzer 1 is an apparatus (an electrolyzer) that generates hydrogen (H₂) by electrolyzing water (H₂O) contained in an electrolyte. Note that, the electrolyzer 1 is not limited to the configuration in which water is electrolyzed to produce hydrogen, and may be, for example, an apparatus that electrolyzes an electrolyte for the purpose of producing or purifying an organic or inorganic substance contained in the electrolyte or concentrating a designated substance. Moreover, in the present embodiment, the electrolyzer 1 is, for example, an anion exchange membrane (AEM) type apparatus. However, the electrolyzer 1 is not limited to the anion exchange membrane type, and may be a proton exchange membrane (PEM: Polymer Electrolyte Membrane) type apparatus, a fuel cell, a CO₂ electrolytic reduction apparatus, a salt electrolyzer, a chemical product electro synthesis apparatus, or the like. The electrolyzer 1 includes, for example, a cell stack 10, an electrolyte supply unit 20, and a power supply unit 30.

Cell stack

The cell stack 10 is an assembly of a plurality of electrochemical cells 11. The cell stack 10 is formed by, for example, arranging the plurality of electrochemical cells 11 in one direction. Each of the electrochemical cell 11 includes a cathode chamber Sa and an anode chamber Sb. The electrochemical cell 11 will be described in detail later.

Electrolyte supply unit

The electrolyte supply unit 20 is a supply unit that supplies an electrolyte to each of the electrochemical cells 11. The electrolyte is, for example, pure water or an alkaline aqueous solution. In the electrolyte in the present embodiment, a potassium hydroxide (KOH) aqueous solution is employed as the alkali aqueous solution. The electrolyte supply unit 20 includes a cathode side supply unit 20a and an anode side supply unit 20b.
The cathode side supply unit 20a is a supply unit that supplies an electrolyte to the cathode chamber Sa of each of the electrochemical cells 11. The cathode side supply unit 20a includes, for example, a hydrogen gas-liquid separation device 21, a first pump 22, a hydrogen recovery unit 23, a first electrolyte supply unit 24, and piping lines L1 and L2. In the cell stack 10 in which the plurality of electrochemical cells 11 are stacked, for example, the piping lines L1 and L2 are connected to a piping structure in the electrochemical cell 11, this piping structure being referred to as a manifold in which the electrochemical cells 11 are connected to each other, an electrolyte is supplied on the piping line L1 side, and the electrolyte and generated hydrogen are discharged on the piping line L2 side.
The hydrogen gas-liquid separation device 21 stores the electrolyte. A supply port of the hydrogen gas-liquid separation device 21 is connected to the cathode chamber Sa of the electrochemical cell 11 via the piping line L1. The first pump 22 is provided partway in the piping line L1, and is configured to deliver the electrolyte stored in the hydrogen gas-liquid separation device 21 toward the cathode chamber Sa of the electrochemical cell 11.
A return port of the hydrogen gas-liquid separation device 21 is connected to the cathode chamber Sa of the electrochemical cell 11 via the piping line L2. An electrolyte containing hydrogen generated in the electrochemical cell 11 flows from the electrochemical cell 11 into the hydrogen gas-liquid separation device 21. The hydrogen gas-liquid separation device 21 includes a gas-liquid separator that separates hydrogen contained in the electrolyte. Hydrogen separated from the electrolyte by the hydrogen gas-liquid separation device 21 is recovered by the hydrogen recovery unit 23. An electrolyte is replenished from the first electrolyte supply unit 24 into the hydrogen gas-liquid separation device 21.
On the other hand, the anode side supply unit 20b is a supply unit that supplies an electrolyte to the anode chamber Sb of each of the electrochemical cells 11. The anode side supply unit 20b includes, for example, an oxygen gas-liquid separation device 26, a second pump 27, an oxygen recovery unit 28, a second electrolyte supply unit 29, and piping lines L3 and L4. In the cell stack 10 in which the plurality of electrochemical cells 11 are stacked, for example, the piping lines L3 and L4 are connected to a piping structure in the electrochemical cell 11, this piping structure being referred to as a manifold in which the electrochemical cells 11 are connected to each other, an electrolyte is supplied on the piping line L3 side, and the electrolyte and generated oxygen are discharged on the piping line L4 side.
The oxygen gas-liquid separation device 26 stores an electrolyte. A supply port of the oxygen gas-liquid separation device 26 is connected to the anode chamber Sb of the electrochemical cell 11 via the piping line L3. The second pump 27 is provided partway in the piping line L3, and is configured to deliver the electrolyte stored in the oxygen gas-liquid separation device 26 toward the anode chamber Sb of the electrochemical cell 11.
The return port of the oxygen gas-liquid separation device 26 is connected to the anode chamber Sb of the electrochemical cell 11 via the piping line L4. An electrolyte containing oxygen (O₂) generated in the electrochemical cell 11 flows from the electrochemical cell 11 into the oxygen gas-liquid separation device 26. The oxygen gas-liquid separation device 26 includes a gas-liquid separator that separates oxygen contained in the electrolyte. The oxygen separated from the electrolyte by the oxygen gas-liquid separation device 26 is recovered by the oxygen recovery unit 28. An electrolyte is replenished from the second electrolyte supply unit 29 to the oxygen gas-liquid separation device 26.

Power supply unit

A power supply unit 30 is a DC power supply device that applies voltage to the electrochemical cell 11. The power supply unit 30 applies a DC voltage, which is required for electrolysis of the electrolyte, across an anode 48 and a cathode 47 (see FIG. 2) of the electrochemical cell 11. In the cell stack 10 in which the plurality of electrochemical cells 11 are stacked, for example, electric wires from the power supply unit 30 are connected to the electrodes at both ends of the cell stack 10, and the required DC current and the required voltage are applied in multiples of the number of stacked layers to supply the required power. Note that, in the present embodiment, the following equation (i) is established. (Electrolytic current (A) required for one electrochemical cell 11) × (Electrolytic voltage (V) required for one electrochemical cell 11) × (The number of stacked electrochemical cells 11) = Supply power (W)...(i)

Configuration of electrochemical cell

Next, the electrochemical cell 11 will be described in detail. The electrochemical cell 11 is a device that generates a specific substance (a desired substance) by causing a chemical reaction (an electrolysis) in an electrolyte by electric energy input from the outside, or a device that generates electric energy to be output to the outside by causing a chemical reaction in an electrolyte.
In the present embodiment, the electrochemical cell 11 is an electrolysis cell (water electrolysis cell) that generates hydrogen by causing electrolysis of water contained in an electrolyte by electric energy input from the outside. Note that, the electrochemical cell 11 is not limited to an electrolysis cell that electrolyzes water to produce hydrogen, and may be, for example, a different type of device such as for electrolytic reduction of carbon dioxide (CO₂), a fuel cell, a salt electrolyzer, a chemical product electrolytic synthesis device, or the like.
FIG. 2 is a cross-sectional view schematically illustrating the electrochemical cell 11. The electrochemical cell 11 or the like includes, for example, a first separator 41, a second separator 42, and a membrane electrode assembly 43.

First separator

The first separator 41 is a member that defines one surface of an accommodation space S of the electrochemical cell 11. The accommodation space S is a space including a cathode chamber Sa and an anode chamber Sb to be described later. The first separator 41 has, for example, a rectangular plate shape, and is formed of a metal member such as stainless steel, titanium, or nickel, or a conductive carbon plate sealed with a conductive carbon plate or a mold resin. A negative voltage is applied to the first separator 41 from the power supply unit 30 via, for example, a first current collector 61 (see FIGS. 4 and 6) described later.
The first separator 41 includes a first separator end portion 41e1 (for example, a lower end portion) and a second separator end portion 41e2 (for example, an upper end portion) located on a side opposite to the first separator end portion 41e1. The piping line L1 described above is connected to the first separator end portion 41e1 of the first separator 41. The piping line L2 described above is connected to the second separator end portion 41e2 of the first separator 41.
The first separator 41 has a first inner surface 41a facing a cathode chamber Sa described later. On the first inner surface 41a, there is formed a first flow path FP1 through which an electrolyte supplied from the piping line L1 flows. The first flow path FP1 is, for example, a channel provided to be recessed from the first inner surface 41a. The electrolyte having flown through the first flow path FP1 is discharged to the outside of the electrochemical cell 11 through the piping line L2.
Note that, each structure (for example, a flow path structure of an electrolyte) illustrated in FIG. 2 is merely an example, and does not limit the content of the present embodiment. For example, as the flow path structure, various structures can be used according to the size and purpose of the device, the usage environment, and the like. The same applies to each structure illustrated in other drawings.

Second separator

The second separator 42 is a member that is disposed with the accommodation space S spaced apart from at least a portion of the first separator 41 and defines the other surface of the accommodation space S. The second separator 42 has, for example, a rectangular plate shape, and is formed of a metal member such as stainless steel, titanium, or nickel, or a conductive carbon plate sealed with a conductive carbon plate or with a mold resin. A positive voltage is applied to the second separator 42 from the power supply unit 30 via a second current collector 62 (see FIGS. 4 and 6) described later. The first separator 41 and the second separator 42 included in the same electrochemical cell 11 form as a pair of separators an electrolytic bath 40 of the electrochemical cell 11.
The second separator 42 has a first separator end portion 42e1 (for example, a lower end portion) and a second separator end portion 42e2 (for example, an upper end portion) located on a side opposite to the first separator end portion 42e1. The piping line L3 described above is connected to the first separator end portion 42e1 of the second separator 42. The piping line L4 described above is connected to the second separator end portion 42e2 of the second separator 42.
The second separator 42 has a second inner surface 42a facing the anode chamber Sb described later. On the second inner surface 42a, there is formed a second flow path FP2 through which an electrolyte supplied from the piping line L3 flows. The second flow path FP2 is, for example, a channel provided to be recessed from the second inner surface 42a. The electrolyte having flown through the second flow path FP2 is discharged to the outside of the electrochemical cell 11 through the piping line L4.
Note that, for convenience of description, herein described a configuration in which the first inner surface 41a of the first separator 41 has a flow path channel (first flow path FP1) and the second inner surface 42a of the second separator 42 has a flow path channel (second flow path FP2). However, for example, the first separator 41 of the electrochemical cell 11 included in the cell stack 10 (see FIG. 1) may be a bipolar plate having a similar flow path channel (first flow path FP1, indicated by two-dot chain line in FIG. 2) on a surface 41b opposite to the first inner surface 41a, in addition to the first inner surface 41a. The second separator 42 of the electrochemical cell 11 included in the cell stack 10 may also be a bipolar plate having a similar flow path channel (second flow path FP2, indicated by two-dot chain line in FIG. 2) on the surface 42b opposite to the second inner surface 42a, in addition to the second inner surface 42a. Note that, flow path channels provided on both surfaces of the first separator 41 and on both surfaces of the second separator 42 may be different in shape and arrangement from each other.

Configuration of membrane electrode assembly

The membrane electrode assembly 43 (MEA) is a structure in which an ion-exchange membrane, a catalyst, and a power feeder are assembled. The membrane electrode assembly 43 is disposed between the first separator 41 and the second separator 42, and is located in the accommodation space S. The membrane electrode assembly 43 includes, for example, an ion-exchange membrane 50, a ceramic-particle-containing layer 51, a cathode catalyst layer 54, a cathode power feeder 55, an anode catalyst layer 56, and an anode power feeder 57.

Ion-exchange membrane

The ion-exchange membrane 50 is a membrane that selectively transmits ions. The ion-exchange membrane 50 is, for example, a solid polymer electrolyte membrane. The ion-exchange membrane 50 is, for example, an anion exchange membrane (AEM) with hydroxide ion (OH^-) conductivity. However, the ion-exchange membrane 50 is not limited to the example described above, and may be, for example, a proton exchange membrane (PEM) of a type different from the example described above.
The ion-exchange membrane 50 has, for example, a rectangular sheet shape and has flexibility. The outline size of the ion-exchange membrane 50 is smaller than the outline size of the first separator 41 or of the second separator 42. The ion-exchange membrane 50 is disposed between the first separator 41 and the second separator 42, and is located in the accommodation space S described above. The ion-exchange membrane 50 includes a first polymer that forms a predetermined molecular skeleton and whose molecular weight is a predetermined first amount. The term "molecular skeleton" as used herein means, for example, a three-dimensional continuous and stereoscopic positional relationship between molecules (or atoms) contained in a polymer (the first polymer and a second polymer described later), or the like. To elaborate further, molecular skeletons herein refer to polymeric main chains and side chains, as well as chemical compositions and atomic arrangements of ion-exchange groups and the like.
The ion-exchange membrane 50 has a first exchange membrane surface 50a facing toward the first inner surface 41a of the first separator 41, and a second exchange membrane surface 50b located on a side opposite to the first exchange membrane surface 50a. The second exchange membrane surface 50b of the ion-exchange membrane 50 faces toward the second inner surface 42a of the second separator 42. The first exchange membrane surface 50a and the second exchange membrane surface 50b are each an example of a "first surface". In the accommodation space S, a cathode chamber Sa is defined between the first exchange membrane surface 50a of the ion-exchange membrane 50 and the first inner surface 41a of the first separator 41. In addition, in the accommodation space S, an anode chamber Sb is defined between the second exchange membrane surface 50b of the ion-exchange membrane 50 and the second inner surface 42a of the second separator 42.
In the cathode chamber Sa, when voltage is applied to the electrochemical cell 11, a chemical reaction presented in the following (Chemical Formula 1) occurs, and hydrogen is produced from the electrolyte. Note that "XX is produced" as used herein can include a case where other substances are simultaneously produced along with the production of XX. Hydroxide ions produced in the cathode chamber Sa pass through the membrane electrode assembly 43 and move from the cathode chamber Sa to the anode chamber Sb.

2H₂O + 2e^-→H₂ + 2OH^-... (Chemical Formula 1)
In the anode chamber Sb, when voltage is applied to the electrochemical cell 11, a chemical reaction presented in the following (Chemical Formula 2) occurs, and oxygen is produced from the electrolyte.

2OH^--1/2O₂ + H₂O + 2e^-... (Chemical Formula 2)
As a result, when the electrochemical cell 11 is viewed as a whole, a chemical reaction presented in the following (Chemical Formula 3) occurs.

H₂O→H₂ + 1/2O₂... (Chemical Formula 3)
As an example of a membrane having a relatively high ionic conductivity, the ion-exchange membrane 50 may include a polystyrene-based or tetraphenyl-based composition in a main chain, and may include an imidazolium group or a quaternary ammonium group in a side chain. On the other hand, instead of this, as an example of a membrane having relatively high oxidation resistance, the ion-exchange membrane 50 may include a polysulfone-based or bromobutylstyrene-based composition.

Ceramic-particle-containing layer

The ceramic-particle-containing layer 51 is a layer provided on both surfaces (the first exchange membrane surface 50a and the second exchange membrane surface 50b) of the ion-exchange membrane 50. Hydroxide ions can pass through the ceramic-particle-containing layer 51. FIG. 3 is a diagram schematically illustrating a cross section of the ceramic-particle-containing layer 51. As illustrated in FIG. 3, the ceramic-particle-containing layer 51 (a first layer 52 and a second layer 53 described later) contains ceramic particles Cs and non-ceramic particles Ad. In the present embodiment, the ceramic-particle-containing layer 51 is made up of the ceramic particles Cs and the non-ceramic particles Ad. The ceramic particles Cs and the non-ceramic particles Ad in the ceramic-particle-containing layer 51 are present at a predetermined ratio (mass ratio or volume ratio). Moreover, the ceramic-particle-containing layer 51 is formed to have a predetermined thickness (T illustrated in FIG. 3). In the present embodiment, the thickness of the ceramic-particle-containing layer 51 is, for example, 3 µm or more and 10 µm or less. Note that, in the ceramic-particle-containing layer 51, there is a void Ga through which an electrolyte can pass.
The ceramic particles Cs have insulating properties. The ceramic particles Cs include, for example, one or more of aluminum oxide (alumina: Al₂O₃), silica (SiO₂), zirconium oxide (zirconia: ZrO₂), yttrium oxide (Y₂O₃), silicon nitride (Si₃N₄), silicon carbide (SiC), or the like. In the present embodiment, the particle diameter of the ceramic particles Cs is 1 µm or more and 10 µm or less. Note that, when a potassium hydroxide aqueous solution is employed as the electrolyte, the ceramic particles Cs preferably include one or more of aluminum oxide (alumina), silicon nitride, silicon carbide, or the like.
The non-ceramic particles Ad contain, for example, one or more of a polymer binder, an ionomer, or the like. In the present embodiment, the non-ceramic particles Ad contain both a polymer binder and an ionomer. The polymer binder functions as a binder for the ceramic particles Cs. That is, the polymer binder binds the ceramic particles Cs to each other. As the polymer binder in the present embodiment, for example, a fluorine-based binder can be employed. Examples of the fluorine-based binder that can be employed include polytetrafluoroethylene (PTFE), polyvinylidene difluoride (PVDF), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and ethylenetetrafluoroethylene copolymer (ETFE). Note that the polymer binder is any binder that has an action of binding the ceramic particles, and a non-fluorine-based binder can also be adopted as the polymer binder.
An ionomer is an ion exchange resin component for reducing the overall electrical resistance of the ceramic-particle-containing layer 51. Examples of the ionomer that is employed include diaza(bicyclo-octane)polyethersulfone, or poly[(p-terphenyl-4,4'-diyl)(N,N-dimethyl-piperidinium-bicarbonate-4,4-diyl)-co-(p-terphenyl-4,4'-diyl)(2,2,2-trifluoro-1-phenylethylidene-diyl)], or poly[(p-terphenyl-4,4'-diyl)(N,N-dimethyl-piperidinium-bicarbonate-4,4-diyl)], which are cationic polymers in which a quaternary ammonium group is introduced into an aromatic polymer skeleton. Alternatively, as the ionomer, it is also possible to adopt an anionic polymer in which an anionic functional group such as a sulfonic acid group or a carboxylic acid group is introduced into a fluorine-based polymer skeleton. Moreover, in the present embodiment, the ionomer includes a second polymer having a molecular weight smaller than the first polymer contained in the ion-exchange membrane 50 and having the same molecular skeleton as that of the first polymer. The molecular weight of the second polymer is a predetermined second amount. The second amount is smaller than the first amount. Note that, the relationship between the molecular weight of the second polymer and the molecular weight of the first polymer is not limited to the description set forth above, and the molecular weight of the second polymer may be the same as the molecular weight of the first polymer, or the molecular weight of the second polymer may be greater than the molecular weight of the first polymer. In the present embodiment, the entirety of the ceramic-particle-containing layer 51 has insulating properties.
Returning to FIG. 2, in the present embodiment, the ceramic-particle-containing layer 51 includes: the first layer 52 disposed in the cathode chamber Sa and in contact with the first exchange membrane surface 50a of the ion-exchange membrane 50; and the second layer 53 disposed in the anode chamber Sb and in contact with the second exchange membrane surface 50b of the ion-exchange membrane 50. That is, the ion-exchange membrane 50 is sandwiched by the first layer 52 and the second layer 53 on both sides. Herein, a side on which the first layer 52 is provided with respect to the ion-exchange membrane 50 (the left side of FIG. 2) is referred to as "one side", and a side opposite to the one side (the right side of FIG. 2) is referred to as "the other side". Therefore, the first layer 52 is disposed further toward one side than the ion-exchange membrane 50, and the second layer 53 is disposed further toward the other side than the ion-exchange membrane 50. As will be described later, each of the first layer 52 and the second layer 53 is a coating layer formed by coating the ion-exchange membrane 50. The first layer 52 and the second layer 53 each have, for example, a rectangular sheet shape. In the present embodiment, the outline sizes of the first layer 52 and of the second layer 53 are the same as or smaller than the outline size of the ion-exchange membrane 50. However, the outline sizes of the first layer 52 and of the second layer 53 are greater than the outline sizes of the cathode power feeder 55 and of the anode power feeder 57 to which surface pressure (pushing pressure in the layering direction) described later is applied.

Cathode catalyst layer

The cathode catalyst layer 54 is a layer (an electrode catalyst layer) that promotes the chemical reaction in the cathode chamber Sa described above. The cathode catalyst layer 54 has, for example, a rectangular sheet shape. In the present embodiment, the outline size of the cathode catalyst layer 54 is formed, for example, to be same as that of the first layer 52. The cathode catalyst layer 54 is disposed in the cathode chamber Sa, and is provided over the entire area of the first layer 52 from a side opposite to the ion-exchange membrane 50. Accordingly, the cathode catalyst layer 54 is disposed further toward one side than the ion-exchange membrane 50. The cathode catalyst layer 54 has a first cathode catalyst surface 54a that is in contact with the entire area of the first layer 52, and a second cathode catalyst surface 54b facing away from the first cathode catalyst surface 54a. That is, the first layer 52 is in contact with the first cathode catalyst surface 54a of the cathode catalyst layer 54. The first cathode catalyst surface 54a is formed to be rougher than the first exchange membrane surface 50a and the second exchange membrane surface 50b of the ion-exchange membrane 50. The first cathode catalyst surface 54a is an example of a "second surface". The cathode power feeder 55 described later is connected to the entire area of the second cathode catalyst surface 54b. A negative voltage is applied to the cathode catalyst layer 54 from the power supply unit 30 via the first separator 41 and the cathode power feeder 55, and the cathode catalyst layer 54 functions as a portion of the cathode 47 of the electrochemical cell 11.
As the material of the cathode catalyst layer 54, there can be used various materials that promote the chemical reaction in the cathode chamber Sa set forth above. For example, the cathode catalyst layer 54 contains one or more of nickel, a nickel alloy, cerium oxide, lanthanum oxide, or platinum. Note that, the "∘∘ oxide" as used herein may contain another material besides ∘∘ and oxygen. Note that, the cathode catalyst layer 54 may contain, for example, another material such as carbon in addition to the above-described materials.

Cathode power feeder

The cathode power feeder 55 is an electrical connector that transmits the voltage applied to the first separator 41 to the cathode catalyst layer 54. The cathode power feeder 55 is disposed in the cathode chamber Sa. The cathode power feeder 55 is located between the first inner surface 41a of the first separator 41 and the cathode catalyst layer 54, and is in contact with both the first inner surface 41a of the first separator 41 and the cathode catalyst layer 54. That is, the cathode catalyst layer 54 is formed on a surface of the cathode power feeder 55 facing toward the side of the ion-exchange membrane 50. Hereinafter, for convenience of description, a surface of the cathode power feeder 55 on which the cathode catalyst layer 54 is formed is referred to as a "cathode surface 55a". The cathode surface 55a and the second cathode catalyst surface 54b of the cathode catalyst layer 54 are in contact with each other.
The cathode power feeder 55 has a structure through which an electrolyte and a gas can pass. The cathode power feeder 55 is formed of, for example, a metal mesh structure, a sintered body, fiber, a conductive carbon fiber mesh structure, or nonwoven fabric. In the present embodiment, the outline size of the cathode power feeder 55 is smaller than the outline size of the cathode catalyst layer 54. In the present embodiment, the cathode 47 of the electrochemical cell 11 is formed by the cathode catalyst layer 54 and the cathode power feeder 55.

Anode catalyst layer

The anode catalyst layer 56 is a layer (an electrode catalyst layer) that promotes the chemical reaction in the anode chamber Sb described above. The anode catalyst layer 56 has, for example, a rectangular sheet shape. In the present embodiment, the anode catalyst layer 56 is formed to have the same outline size as that of the second layer 53, for example. The anode catalyst layer 56 is disposed in the anode chamber Sb, and is provided over the entire area of the second layer 53 from a side opposite to the ion-exchange membrane 50. Therefore, the anode catalyst layer 56 is disposed on the other side of the ion-exchange membrane 50. The anode catalyst layer 56 has a first anode catalyst surface 56a that is in contact with the entire area of the second layer 53, and a second anode catalyst surface 56b facing away from the first anode catalyst surface 56a. That is, the second layer 53 is in contact with the first anode catalyst surface 56a of the anode catalyst layer 56. The first anode catalyst surface 56a is formed to be rougher than the first exchange membrane surface 50a and the second exchange membrane surface 50b of the ion-exchange membrane 50. The first anode catalyst surface 56a is an example of a "second surface". The anode power feeder 57 described later is connected to the entire area of the second anode catalyst surface 56b. A positive voltage is applied to the anode catalyst layer 56 from the power supply unit 30 via the second separator 42 and the anode power feeder 57, and the anode catalyst layer 56 functions as a portion of the anode 48 of the electrochemical cell 11. In the present embodiment, the anode catalyst layer 56 is formed to have the same thickness as that of the cathode catalyst layer 54.
As a material of the anode catalyst layer 56, there can be used various materials that promote the chemical reaction in the anode chamber Sb described above. For example, the anode catalyst layer 56 includes one or more of nickel, a nickel alloy, nickel oxide, copper oxide, iridium oxide, niobium oxide, lead oxide, or bismuth oxide. As described above, the "XX oxide" herein may include another material besides XX and oxygen. For example, the "nickel oxide" may include another material such as iron (Fe) or cobalt (Co) besides nickel and oxygen. Note that, the "copper oxide" may include another material such as cobalt besides copper (Cu) and oxygen. The "iridium oxide" may include another material such as ruthenium (Ru) besides iridium (Ir) and oxygen. The "lead oxide" may include another material such as ruthenium besides lead (Pb) and oxygen. The "bismuth oxide" may include another material such as ruthenium besides bismuth (Bi) and oxygen. Note that, the anode catalyst layer 56 may include, for example, another material such as carbon besides the above-described materials.
Therefore, the ceramic-particle-containing layer 51 (the first layer 52 and the second layer 53) described above is provided, as a separate body from the cathode catalyst layer 54 and the anode catalyst layer 56, between the ion-exchange membrane 50 and the cathode catalyst layer 54 and between the ion-exchange membrane 50 and the anode catalyst layer 56, and forms a layer structure (five layers) together with the ion-exchange membrane 50, the cathode catalyst layer 54, and the anode catalyst layer 56. That is, boundary surfaces exist between the first layer 52 and the cathode catalyst layer 54 and between the second layer 53 and the anode catalyst layer 56. Similarly, boundary surfaces exist between the first layer 52 and the ion-exchange membrane 50 and between the second layer 53 and the ion-exchange membrane 50.

Anode power feeder

The anode power feeder 57 is an electrical connector that transmits the voltage applied to the second separator 42 to the anode catalyst layer 56. The anode power feeder 57 is disposed in the anode chamber Sb. The anode power feeder 57 is located between the second inner surface 42a of the second separator 42 and the anode catalyst layer 56, and is in contact with both the second inner surface 42a of the second separator 42 and the anode catalyst layer 56. That is, the anode catalyst layer 56 is formed on a surface of the anode power feeder 57 facing toward the side of the ion-exchange membrane 50. Hereinafter, for convenience of description, a surface of the anode power feeder 57 on which the anode catalyst layer 56 is formed is referred to as an "anode surface 57a". The anode surface 57a and the second anode catalyst surface 56b of the anode catalyst layer 56 are in contact with each other.
The anode power feeder 57 has a structure through which an electrolyte and a gas can pass. The anode power feeder 57 is formed of, for example, a metal mesh structure, a sintered body, fiber, or a conductive carbon fiber mesh structure, nonwoven fabric, or the like. In the present embodiment, the outline size of the anode power feeder 57 is smaller than the outline size of the anode catalyst layer 56. In the present embodiment, the anode 48 of the electrochemical cell 11 is formed by the anode catalyst layer 56 and the anode power feeder 57.
FIG. 4 is an exploded perspective view schematically illustrating the electrochemical cell 11. In addition to the above-described configuration, the electrochemical cell 11 further includes, for example, a first current collector 61, a second current collector 62, a first insulator 63, a second insulator 64, a first insulating material 65, a second insulating material 66, a first end flange 67, and a second end flange 68. Note that, in FIG. 4, illustrations of a support part 70, a sealing part 80, and a pressing mechanism 90, which will be described later, are omitted.

First current collector

The first current collector 61 is an electrical connector that transmits a negative voltage applied from the power supply unit 30 to the first separator 41. The first current collector 61 is a metal plate member (for example, a copper plate). The first current collector 61 is in contact with the first separator 41 from the side opposite to the accommodation space S of the electrochemical cell 11, for example, and is electrically connected to the first separator 41. A negative voltage necessary for electrolysis in the electrochemical cell 11 is applied from the power supply unit 30 to the first current collector 61. Note that, the first current collector 61 may be shared by two electrochemical cells 11 adjacent to each other in the cell stack 10.

Second current collector

The second current collector 62 is an electrical connector that transmits a positive voltage applied from the power supply unit 30 to the second separator 42. The second current collector 62 is a metal plate member (e.g., a copper plate). The second current collector 62 is in contact with the second separator 42 from the side opposite to the accommodation space S of the electrochemical cell 11, for example, and is electrically connected to the second separator 42. A positive voltage necessary for electrolysis in the electrochemical cell 11 is applied from the power supply unit 30 to the second current collector 62. Note that, the second current collector 62 may be shared by two electrochemical cells 11 adjacent to each other in the cell stack 10.

First insulator

The first insulator 63 is an insulating member between the outer periphery of the first separator 41 and the outer periphery of the second separator 42. The first insulator 63 is a frame-shaped sheet member slightly larger than the outline of the first layer 52, the outline of the cathode catalyst layer 54, and the outline of the cathode power feeder 55. The first insulator 63 is attached to the first inner surface 41a of the first separator 41 and covers an end portion of the first inner surface 41a (see FIGS. 5 and 6). The material of the first insulator 63 is not particularly limited as long as it is an insulating material, and is, for example, a sheet-shaped resin such as PTFE.

Second insulator

Similarly to the first insulator 63, the second insulator 64 is an insulating member between the outer periphery of the first separator 41 and the outer periphery of the second separator 42. The second insulator 64 is a frame-shaped sheet member slightly larger than the outline of the second layer 53, the outline of the anode catalyst layer 56, and the outline of the anode power feeder 57. The second insulator 64 is attached to the second inner surface 42a of the second separator 42 and covers an end portion of the second inner surface 42a (see FIGS. 5 and 6). The material of the second insulator 64 is not particularly limited as long as it is an insulating material, and is, for example, a sheet-like resin such as PTFE. Incidentally, the first insulator 63 and the second insulator 64 may be an integrated insulator.

First insulating material

The first insulating material 65 is located between the first current collector 61 and the first end flange 67. The outline size of the first insulating material 65 is, for example, the same as the outline size of the first current collector 61 or larger than the outline size of the first current collector 61.

Second insulating material

The second insulating material 66 is located between the second current collector 62 and the second end flange 68. The outline size of the second insulating material 66 is, for example, the same as the outline size of the second current collector 62 or larger than the outline size of the second current collector 62.

First end flange

The first end flange 67 is located on a side of the first insulating material 65 opposite to the accommodation space S of the electrochemical cell 11. The first end flange 67 is formed of, for example, a metal plate member (for example, a stainless plate). The outline size of the first end flange 67 is larger than the outline size of the first insulating material 65, for example.

Second end flange

The second end flange 68 is located on a side of the second insulating material 66 opposite to the accommodation space S of the electrochemical cell 11. The second end flange 68 is formed of, for example, a metal plate member (for example, a stainless plate). The outline size of the second end flange 68 is larger than the outline size of the second insulating material 66, for example.
Note that, the electrochemical cell 11 is not limited to the configuration described above. For example, when the cell stack 10 is formed by arranging the plurality of electrochemical cells 11 side by side, two electrochemical cells 11 adjacent to each other among the plurality of electrochemical cells 11 may share the first separator 41 or the second separator 42, each of which is a bipolar plate. In this case, the current collector (the first current collector 61 or the second current collector 62), the insulator (the first insulator 63 or the second insulator 64), the insulating material (the first insulating material 65 or the second insulating material 66), and the end flange (the first end flange 67 or the second end flange 68) do not need to present between two adjacent electrochemical cells 11.

Structure of outer periphery of electrochemical cell

FIG. 5 is a cross-sectional view illustrating the electrochemical cell 11. In the present embodiment, the outline size of the ion-exchange membrane 50 is larger than each of the outline size of the ceramic-particle-containing layer 51 (the first layer 52 and the second layer 53), the outline size of the cathode catalyst layer 54, and the outline size of the cathode power feeder 55. In other words, the area of the ion-exchange membrane 50 is larger than each of the area of the ceramic-particle-containing layer 51, the area of the cathode catalyst layer 54, and the area of the cathode power feeder 55. The ion-exchange membrane 50 protrudes further toward outside (the outer peripheral side) than the cathode catalyst layer 54 and the cathode power feeder 55 in a direction (for example, the X direction or the Y direction) orthogonal to the thickness direction (Z direction) of the membrane electrode assembly 43. The term "outside" or "outer peripheral side" as used herein means a side away from the central region C of the membrane electrode assembly 43 in a direction (e.g., X direction or Y direction) orthogonal to the thickness direction (Z direction) of the membrane electrode assembly 43.
As illustrated in FIG. 5, the electrochemical cell 11 further includes, for example, a support part 70 and a sealing part 80 besides the above-described configuration. The support part 70 is a member that supports the membrane electrode assembly 43 inside the electrochemical cell 11 (specifically, between the first separator 41 and the second separator 42). The sealing part 80 is a member that closes the accommodation space S between the first separator 41 and the second separator 42 from the outer peripheral side. Hereinafter, the support part 70 and the sealing part 80 will be described.

Support part

The support part 70 is disposed between the first separator 41 and the second separator 42. The support part 70 is located further toward inside (inner peripheral side) than an outer edge portion 50e of the ion-exchange membrane 50 and supports the ion-exchange membrane 50. The term "outer edge portion 50e" as used herein means an edge portion away from the central region C of the membrane electrode assembly 43 in a direction (for example, the X direction or the Y direction) orthogonal to the thickness direction (Z direction) of the membrane electrode assembly 43. As used herein, the term "inside" or "inner peripheral side" means an inside (a side close to the central region C) as viewed from the central region C of the membrane electrode assembly 43. In the present embodiment, the support part 70 includes, for example, a first support part 71 and a second support part 72. The first support part 71 is a support part on the cathode 47 side. The first support part 71 is disposed between the first inner surface 41a of the first separator 41 and the second cathode catalyst surface 54b of the cathode catalyst layer 54. The first support part 71 is located further toward inside (inner peripheral side) than the outer edge portion 50e of the ion-exchange membrane 50. The first support part 71 is sandwiched between the first inner surface 41a (or the first insulator 63) and the second cathode catalyst surface 54b at a position further toward outside (outer peripheral side) than the cathode power feeder 55, and supports the ion-exchange membrane 50 with respect to the first inner surface 41a. The first support part 71 has an annular shape (for example, a frame shape) along the outer edge portion 50e of the ion-exchange membrane 50, and is formed in an annular shape slightly smaller than the outer edge portion 50e of the ion-exchange membrane 50. The second support part 72 is a support part on the anode 48 side. The second support part 72 is disposed between the second inner surface 42a of the second separator 42 and the second anode catalyst surface 56b of the anode catalyst layer 56. The second support part 72 is located further toward inside (inner peripheral side) than the outer edge portion 50e of the ion-exchange membrane 50. The second support part 72 is sandwiched between the second inner surface 42a and the second anode catalyst surface 56b at a position further toward outside (outer peripheral side) than the anode power feeder 57, and supports the ion-exchange membrane 50 with respect to the second inner surface 42a. The second support part 72 has an annular shape (for example, a frame shape) along the outer edge portion 50e of the ion-exchange membrane 50, and is formed in an annular shape slightly smaller than the outer edge portion 50e of the ion-exchange membrane 50.

Sealing part

The sealing part 80 is disposed between the first separator 41 and the second separator 42. The sealing part 80 is located further toward outside (outer peripheral side) than the outer edge portion 50e of the ion-exchange membrane 50, and seals the accommodation space S of the electrochemical cell 11. In the present embodiment, the sealing part 80 includes a first sealing part 81 and a second sealing part 82. However, the first sealing part 81 and the second sealing part 82 may be integrally formed. That is, the first sealing part 81 and the second sealing part 82 may be a single member. The sealing part 80 may be formed integrally with at least one of the first insulator 63 and the second insulator 64 described above. The first sealing part 81 is a sealing part on the cathode 47 side. The first sealing part 81 is located further toward outside (outer peripheral side) than the outer edge portion 50e of the ion-exchange membrane 50. The first sealing part 81 is sandwiched between the first inner surface 41a of the first separator 41 and the second sealing part 82 and seals a portion of the outer peripheral side of the accommodation space S. In the present embodiment, the first sealing part 81 is sandwiched between the first insulator 63 attached to the first inner surface 41a and the second sealing part 82. The first sealing part 81 has an annular shape (for example, a frame shape) along the outer edge portion 50e of the ion-exchange membrane 50, and is formed in an annular shape slightly larger than the outer edge portion 50e of the ion-exchange membrane 50. The second sealing part 82 is a sealing part on the anode 48 side. The second sealing part 82 is located further toward outside than the outer edge portion 50e of the ion-exchange membrane 50. The second sealing part 82 is sandwiched between the second inner surface 42a of the second separator 42 and the first sealing part 81 and seals a portion of the outer peripheral side of the accommodation space S. In the present embodiment, the second sealing part 82 is sandwiched between the second insulator 64 attached to the second inner surface 42a and the first sealing part 81. The second sealing part 82 has an annular shape (for example, a frame shape) along the outer edge portion 50e of the ion-exchange membrane 50, and is formed in an annular shape slightly larger than the outer edge portion 50e of the ion-exchange membrane 50.
The electrochemical cell 11 further includes, for example, a pressing mechanism 90 besides the above-described configuration. FIG. 6 is a diagram for explaining the pressing mechanism 90. In FIG. 6, besides the configuration illustrated in FIG. 5, the first current collector 61, the second current collector 62, the first insulating material 65, the second insulating material 66, the first end flange 67, the second end flange 68, and the pressing mechanism 90 are further illustrated.

Pressing mechanism

The pressing mechanism 90 includes, for example, a first component 91 and a second component 92. In the present embodiment, for example, the first component 91 is a bolt (such as a stud bolt) having no head, and the second component 92 is a nut that can be screwed onto the first component 91. The first component 91 and the second component 92 are made of a material such as metal.
Here, as illustrated in FIG. 6, according to the present embodiment, in each of the first end flange 67, the first insulating material 65, the second insulating material 66, and the second end flange 68, there is formed a hole that penetrates through them in a direction (Z direction, hereinafter referred to as "layering direction") in which they are stacked each other, and the holes formed in each of them overlap each other in the layering direction (left-right direction in FIG. 6) to form an insertion hole 11h extending in the layering direction. In the present embodiment, a plurality of (for example, three or more) insertion holes 11h are arranged at intervals along the frame shape of the first insulator 63, the second insulator 64, the support part 70 (the first support part 71 and the second support part 72), and the sealing part 80 (the first sealing part 81 and the second sealing part 82). Note that, in FIG. 6, only two insertion holes 11h are illustrated for convenience of illustration. That is, the electrochemical cell 11 includes a plurality of the pressing mechanisms 90.
The first component 91 is inserted into each of the insertion holes 11h described above. In the present embodiment, two second components 92 are screwed onto each of the first components 91 inserted into each of the insertion holes 11h. Out of the two second components 92 screwed onto the first component 91, one of the second components 92 abuts the first end flange 67 from the side opposite to the first insulating material 65. On the other hand, out of the two second components 92 screwed onto the first component 91, the other of the second components 92 abuts the second end flange 68 from the side opposite to the second insulating material 66. That is, the two second components 92 screwed onto the respective first components 91 impart surface pressure in the layering direction to the respective elements of the electrochemical cell 11 disposed between the first end flange 67 and the second end flange 68 with the first end flange 67 and the second end flange 68 interposed therebetween.
Therefore, the plurality of pressing mechanisms 90 apply a predetermined surface pressure (arrows Ps illustrated in FIG. 6) between the ion-exchange membrane 50 and the cathode catalyst layer 54 with the ceramic-particle-containing layer 51 interposed therebetween and between the ion-exchange membrane 50 and the anode catalyst layer 56 with the ceramic-particle-containing layer 51 interposed therebetween. The magnitude of the predetermined surface pressure is adjusted by, for example, the tightening torque of the second component 92. Note that, in the present embodiment, the pressing force in the layering direction of the two second components 92 screwed onto the first component 91 is equally adjusted in all of the pressing mechanism 90.

Method of manufacturing membrane electrode assembly

Next, a method of manufacturing the membrane electrode assembly 43 will be described.
FIG. 7 is a cross-sectional view illustrating a method of manufacturing the membrane electrode assembly 43 in the present embodiment.
First, as illustrated in FIG. 7(a), the first layer 52 of the ceramic-particle-containing layer 51 is provided on the first exchange membrane surface 50a of the ion-exchange membrane 50. The first layer 52 is formed, for example, by applying a material for forming the first layer 52 to the first exchange membrane surface 50a of the ion-exchange membrane 50 (coating the first exchange membrane surface 50a of the ion-exchange membrane 50 with a material for forming the first layer 52), and pressing the applied material for forming the first layer 52 and the ion-exchange membrane 50 under a predetermined temperature and a predetermined pressure. The "material for forming the first layer 52" mentioned here is a slurry formed by mixing the above-described ceramic particles Cs, non-ceramic particles Ad (polymer binder and ionomer), and a predetermined solvent. By pressing under a predetermined temperature and a predetermined pressure, the solvent is volatilized from the slurry applied on the first exchange membrane surface 50a (the slurry is dried). As a result, the first layer 52 as a coating layer is formed on the first exchange membrane surface 50a. That is, the first exchange membrane surface 50a of the ion-exchange membrane 50 comes into contact with the first layer 52 of the ceramic-particle-containing layer 51. Similarly, the second layer 53 is provided on the second exchange membrane surface 50b of the ion-exchange membrane 50. The second layer 53 is formed, for example, by applying a material for forming the second layer 53 to the second exchange membrane surface 50b of the ion-exchange membrane 50 (coating the second exchange membrane surface 50b of the ion-exchange membrane 50 with a material for forming the second layer 53), and pressing the applied material for forming the second layer 53 and the ion-exchange membrane 50 under a predetermined temperature and a predetermined pressure. The "material for forming the second layer 53" mentioned here is the same slurry as the material for forming the first layer 52. By pressing under a predetermined temperature and a predetermined pressure, the solvent is volatilized from the slurry applied on the second exchange membrane surface 50b (the slurry is dried). As a result, the second layer 53 as a coating layer is formed on the second exchange membrane surface 50b. That is, the second exchange membrane surface 50b of the ion-exchange membrane 50 comes into contact with the second layer 53 of the ceramic-particle-containing layer 51. For the application of the material for forming the first layer 52 and the material for forming the second layer 53, for example, a coating method, a CVD method, an electroless plating method, a method using a catalyst ink, a method of applying by spraying, or the like may be appropriately selected. Note that there is no restriction on the order in which the first layer 52 and the second layer 53 are provided on the ion-exchange membrane 50.
Subsequently, as illustrated in FIG. 7(b), the cathode catalyst layer 54 is provided on the first layer 52 of the ceramic-particle-containing layer 51. The cathode catalyst layer 54 is formed, for example, by applying a material of the cathode catalyst layer 54 onto the first layer 52 (coating the first layer 52 with a material of the cathode catalyst layer 54), and pressing the applied material of the cathode catalyst layer 54, the ion-exchange membrane 50, and the ceramic-particle-containing layer 51 under a predetermined temperature and a predetermined pressure. As a result, the cathode catalyst layer 54 is formed on the first layer 52. That is, the first cathode catalyst surface 54a of the cathode catalyst layer 54 comes into contact with the first layer 52 of the ceramic-particle-containing layer 51. Similarly, the anode catalyst layer 56 is provided on the second layer 53 of the ceramic-particle-containing layer 51. The anode catalyst layer 56 is formed, for example, by applying a material of the anode catalyst layer 56 onto the second layer 53 (coating the second layer 53 with a material of the anode catalyst layer 56), and pressing the applied material of the anode catalyst layer 56, the ion-exchange membrane 50, and the ceramic-particle-containing layer 51 under a predetermined temperature and a predetermined pressure. As a result, the anode catalyst layer 56 is formed on the second layer 53. That is, the first anode catalyst surface 56a of the anode catalyst layer 56 comes into contact with the second layer 53 of the ceramic-particle-containing layer 51. For the application of the material of the cathode catalyst layer 54 and the material of the anode catalyst layer 56, for example, a coating method, a CVD method, an electroless plating method, a method using a catalyst ink, a method of applying by spraying, or the like may be appropriately selected. Note that there is no restriction on the order in which the cathode catalyst layer 54 and the anode catalyst layer 56 are provided on the ceramic-particle-containing layer 51. Providing the cathode catalyst layer 54 and the anode catalyst layer 56 do not need to be later than providing the first layer 52 and the second layer 53 on the ion-exchange membrane 50, for example, only the first layer 52 is provided on the ion-exchange membrane 50 and then the cathode catalyst layer 54 may be provided on the first layer 52, or only the second layer 53 is provided on the ion-exchange membrane 50 and then the anode catalyst layer 56 may be provided on the second layer 53.
Subsequently, as illustrated in FIG. 7(c), the cathode power feeder 55 is stacked on the second cathode catalyst surface 54b of the cathode catalyst layer 54. The cathode power feeder 55 is pressed at a predetermined temperature and a predetermined pressure while being stacked on the cathode catalyst layer 54, whereby the cathode power feeder 55 and the cathode catalyst layer 54 are connected to each other. That is, the cathode surface 55a of the cathode power feeder 55 comes into in contact with the second cathode catalyst surface 54b of the cathode catalyst layer 54. As a result, the cathode power feeder 55 is provided on the cathode catalyst layer 54. Similarly, the anode power feeder 57 is stacked on the second anode catalyst surface 56b of the anode catalyst layer 56. The anode power feeder 57 is pressed at a predetermined temperature and a predetermined pressure while being stacked on the anode catalyst layer 56, whereby the anode power feeder 57 and the anode catalyst layer 56 are connected to each other. That is, the anode surface 57a of the anode power feeder 57 comes into contact with the second anode catalyst surface 56b of the anode catalyst layer 56. As a result, the anode power feeder 57 is provided on the anode catalyst layer 56. Note that there is no restriction on the order of the connection between the cathode power feeder 55 and the cathode catalyst layer 54 and the connection between the anode power feeder 57 and the anode catalyst layer 56.
Thereby, the membrane electrode assembly 43 is completed. The ceramic-particle-containing layer 51 is provided, as a separate body from the cathode catalyst layer 54 and the anode catalyst layer 56, between the ion-exchange membrane 50 and the cathode catalyst layer 54 and between the ion-exchange membrane 50 and the anode catalyst layer 56, and forms a layer structure together with the cathode 47 (the cathode catalyst layer 54 and the cathode power feeder 55) and the anode 48 (the anode catalyst layer 56 and the anode power feeder 57).

Action and Effect

As a comparative example, consideration is given to a structure of the electrochemical cell 11 in which the cathode catalyst layer 54 and the anode catalyst layer 56 are provided on both surfaces (the first exchange membrane surface 50a and the second exchange membrane surface 50b) of the ion-exchange membrane 50. Here, when the cathode catalyst layer 54 and the anode catalyst layer 56 are formed by coating or the like, a surface of the cathode catalyst layer 54 (the first cathode catalyst surface 54a) and a surface of the anode catalyst layer 56 (the first anode catalyst surface 56a), which are in contact with the ion-exchange membrane 50, are formed to be rough in some cases. For this reason, there may be sparsely present a portion where the cathode catalyst layer 54 and the anode catalyst layer 56 are close contact with the ion-exchange membrane 50 and a portion where the cathode catalyst layer 54 and the anode catalyst layer 56 are not in close contact with the ion-exchange membrane 50. In order to suppress concentration of contact resistance in the close contact portion, surface pressure is imparted to the ion-exchange membrane 50 from the electrode catalyst layer side in some cases. However, depending on the imparted surface pressure, defects such as damage may occur in the ion-exchange membrane 50 due to the roughness (asperities) of the surfaces of the cathode catalyst layer 54 and the anode catalyst layer 56.
On the other hand, in the present embodiment, the electrochemical cell 11 includes the ceramic-particle-containing layer 51 disposed between the ion-exchange membrane 50 and the cathode catalyst layer 54 and between the ion-exchange membrane 50 and the anode catalyst layer 56. According to such a configuration, even when asperities sparsely occur on the surface (the first cathode catalyst surface 54a) of the cathode catalyst layer 54 and the surface (the first anode catalyst surface 56a) of the anode catalyst layer 56, the cathode catalyst layer 54 and the anode catalyst layer 56 press the ceramic-particle-containing layer 51 when surface pressure is applied. That is, the asperities of the cathode catalyst layer 54 and of the anode catalyst layer 56 do not have a direct influence on the ion-exchange membrane 50. Therefore, even when a large surface pressure is imparted, there can be avoided an occurrence of defects such as damage in the ion-exchange membrane 50. That is, durability of the electrochemical cell 11 can be improved.

Second Embodiment

Next, a second embodiment will be described with reference to FIG. 8. FIG. 8 is a cross-sectional view illustrating a method of manufacturing the membrane electrode assembly 43 of the second embodiment. In the second embodiment, a method of manufacturing the membrane electrode assembly 43 is different from the method of manufacturing the membrane electrode assembly 43 described in the first embodiment.
First, as illustrated in FIG. 8(a), the cathode catalyst layer 54 is provided on the cathode surface 55a of the cathode power feeder 55. The cathode catalyst layer 54 is formed, for example, by applying a material of the cathode catalyst layer 54 to the cathode surface 55a of the cathode power feeder 55 (coating the cathode surface 55a of the cathode power feeder 55 with a material of the cathode catalyst layer 54), and pressing the applied material of the cathode catalyst layer 54 and the cathode power feeder 55 at a predetermined temperature and a predetermined pressure. Similarly, the anode catalyst layer 56 is provided on the anode surface 57a of the anode power feeder 57. The anode catalyst layer 56 is formed by, for example, applying a material of the anode catalyst layer 56 to the anode surface 57a of the anode power feeder 57 (coating the anode surface 57a of the anode power feeder 57 with a material of the anode catalyst layer 56), and pressing the applied material of the anode catalyst layer 56 and the anode power feeder 57 at a predetermined temperature and a predetermined pressure. For the application of the material of the cathode catalyst layer 54 and the material of the anode catalyst layer 56, for example, a coating method, a chemical vapor deposition (CVD) method, an electroless plating method, a method using a catalyst ink, a method of applying a catalyst by spraying, or the like may be appropriately selected. Note that there is no restriction on the order in which the cathode catalyst layer 54 and the anode catalyst layer 56 are provided on the cathode power feeder 55 and the anode catalyst layer 56.
Subsequently, as illustrated in FIG. 8(b), the first layer 52 of the ceramic-particle-containing layer 51 is provided on the cathode catalyst layer 54. The first layer 52 is formed, for example, by applying a material for forming the first layer 52 to the cathode catalyst layer 54 (coating the cathode catalyst layer 54 with a material for forming the first layer 52), and pressing the applied material for forming the first layer 52, the cathode catalyst layer 54, and the cathode power feeder 55 under a predetermined temperature and a predetermined pressure. As a result, the first layer 52 is formed on the cathode catalyst layer 54. Similarly, the second layer 53 of the ceramic-particle-containing layer 51 is provided on the anode catalyst layer 56. The second layer 53 is formed, for example, by applying a material for forming the second layer 53 to the anode catalyst layer 56 (coating the anode catalyst layer 56 with a material for forming the second layer 53), and pressing the applied material of the second layer 53, the anode catalyst layer 56, and the anode power feeder 57 under a predetermined temperature and a predetermined pressure. As a result, the second layer 53 is formed on the anode catalyst layer 56. For the application of the material for forming the first layer 52 and the material for forming the second layer 53, for example, a coating method, a CVD method, an electroless plating method, a method using a catalyst ink, a method of applying a catalyst by spraying, or the like may be appropriately selected. Note that there is no restriction on the order of providing the first layer 52 on the cathode catalyst layer 54 and providing the second layer 53 on the anode catalyst layer 56.
Subsequently, as illustrated in FIG. 8(c), the first layer 52 formed on the cathode catalyst layer 54 is pressed at a predetermined temperature and a predetermined pressure while being stacked on the first exchange membrane surface 50a of the ion-exchange membrane 50, whereby the cathode 47 (the cathode catalyst layer 54 and the cathode power feeder 55) and the ion-exchange membrane 50 are connected to each other with the first layer 52 interposed therebetween. Similarly, the second layer 53 formed on the anode catalyst layer 56 is pressed at a predetermined temperature and a predetermined pressure while being stacked on the second exchange membrane surface 50b of the ion-exchange membrane 50, whereby the anode 48 (the anode catalyst layer 56 and the anode power feeder 57) and the ion-exchange membrane 50 are connected to each other with the second layer 53 interposed therebetween. Note that there is no restriction on the order of the connection between the cathode 47 and the ion-exchange membrane 50 with the first layer 52 interposed therebetween and the connection between the anode 48 and the ion-exchange membrane 50 with the second layer 53 interposed therebetween.
The membrane electrode assembly 43 described in the first embodiment can also be completed by the manufacturing method described in the present embodiment. According to the method described in the present embodiment, a material (slurry) for forming the ceramic-particle-containing layer 51 (the first layer 52 and the second layer 53) is not required to be applied to the surfaces of the ion-exchange membrane 50 (the first exchange membrane surface 50a and the second exchange membrane surface 50b). For this reason, for example, there is no warping of the ion-exchange membrane 50 due to absorbing a solvent or the like contained in the slurry. Accordingly, the manufacturability of the membrane electrode assembly 43 (the electrochemical cell 11) can be enhanced.

Third Embodiment

Next, a third embodiment will be described with reference to FIG. 9. FIG. 9 is a cross-sectional view illustrating a method of manufacturing the membrane electrode assembly 43 of the third embodiment. In the third embodiment, a method of manufacturing the membrane electrode assembly 43 is different from the method of manufacturing the membrane electrode assembly 43 described in the first embodiment and in the second embodiment.
First, as illustrated in FIG. 9(a), the first layer 52 of the ceramic-particle-containing layer 51 is provided on the first exchange membrane surface 50a of the ion-exchange membrane 50. Similarly, the second layer 53 is provided on the second exchange membrane surface 50b of the ion-exchange membrane 50. As a method of providing the first layer 52 of the ceramic-particle-containing layer 51 on the first exchange membrane surface 50a of the ion-exchange membrane 50 and a method of providing the second layer 53 of the ceramic-particle-containing layer 51 on the second exchange membrane surface 50b of the ion-exchange membrane 50, the method described with reference to FIG. 7(a) in the first embodiment may be adopted.
Subsequently, as illustrated in FIG. 9(b), the cathode catalyst layer 54 is provided on the cathode surface 55a of the cathode power feeder 55. Similarly, the anode catalyst layer 56 is provided on the anode surface 57a of the anode power feeder 57. As a method of providing the cathode catalyst layer 54 on the cathode surface 55a of the cathode power feeder 55 and a method of providing the anode catalyst layer 56 on the anode surface 57a of the anode power feeder 57, the method described in the second embodiment with reference to FIG. 8(a) may be adopted.
Note that there is no restriction on the order of performing the method illustrated in FIG. 9(a) and the method illustrated in FIG. 9(b).
Subsequently, as illustrated in FIG. 9(c), the cathode catalyst layer 54 formed on the cathode power feeder 55 is pressed at a predetermined temperature and a predetermined pressure while being stacked on the first layer 52 of the ceramic-particle-containing layer 51 formed on the first exchange membrane surface 50a of the ion-exchange membrane 50, whereby the cathode 47 (the cathode catalyst layer 54 and cathode power feeder 55) and the ion-exchange membrane 50 are connected to each other with the first layer 52 interposed therebetween. Similarly, the anode catalyst layer 56 formed on the anode power feeder 57 is pressed at a predetermined temperature and a predetermined pressure while being stacked on the second layer 53 of the ceramic-particle-containing layer 51 formed on the second exchange membrane surface 50b of the ion-exchange membrane 50, whereby the anode 48 (the anode catalyst layer 56 and the anode power feeder 57) and the ion-exchange membrane 50 are connected to each other with the second layer 53 interposed therebetween. Note that there is no restriction on the order of the connection between the cathode 47 and the ion-exchange membrane 50 with the first layer 52 interposed therebetween and the connection between the anode 48 and the ion-exchange membrane 50 with the second layer 53 interposed therebetween.
The membrane electrode assembly 43 described in the first embodiment can also be completed by the manufacturing method described in the present embodiment.
FIG. 10 is a diagram illustrating an example of the relationship between the surface pressure and the contact resistance in comparison between a case where the ceramic-particle-containing layer 51 is present in the electrochemical cell 11 according to each embodiment described above and a case where the ceramic-particle-containing layer is not present. The "surface pressure" indicated on the horizontal axis in FIG. 10 means the magnitude of surface pressure acting between the cathode catalyst layer 54 and the ion-exchange membrane 50 and between the anode catalyst layer 56 and the ion-exchange membrane 50 caused by the pressing mechanism 90. Note that, the magnitude of the surface pressure may be measured based on the magnitude of the tightening torque described above, or may be measured, for example, by disposing pressure-sensitive paper or the like in the electrochemical cell 11. The "contact resistance" indicated based on the vertical axis in FIG. 10 means the magnitude of the contact resistance generated in the cathode catalyst layer 54 and in the anode catalyst layer 56. FIG. 10 illustrates results obtained by the analysis of the present inventors. As indicated by the solid curve in FIG. 10, the contact resistance of the cathode catalyst layer 54 and the anode catalyst layer 56 decreases with increasing surface pressure acting between the ion-exchange membrane 50 and the cathode catalyst layer 54 with the ceramic-particle-containing layer 51 interposed therebetween and between the ion-exchange membrane 50 and the anode catalyst layer 56 with the ceramic-particle-containing layer 51 interposed therebetween (with the ceramic-particle-containing layer 51). As indicated by the dotted curve in FIG. 10, the contact resistance of the cathode catalyst layer 54 and the anode catalyst layer 56 decreases with increasing surface pressure acting between the ion-exchange membrane 50 and the cathode catalyst layer 54 with no ceramic-particle-containing layer 51 interposed therebetween and between the ion-exchange membrane 50 and the anode catalyst layer 56 with no ceramic-particle-containing layer 51 interposed therebetween (without the ceramic-particle-containing layer 51). However, in the case of "without the ceramic-particle-containing layer 51", it was found that when a surface pressure higher than a certain surface pressure (A illustrated in FIG. 10) was applied, a short circuit occurred due to damage of the ion-exchange membrane 50, and the contact resistance rapidly decreased. The short circuit due to the damage of the ion-exchange membrane 50 is an example of a "defects occurring in the ion-exchange membrane 50". The predetermined surface pressure to be applied by the pressing mechanism 90 described in the first to third embodiments is adopted from a range of surface pressure (R illustrated in FIG. 10) larger than the certain surface pressure (A). In other words, the predetermined surface pressure described in the embodiment set forth above is adjusted to a value higher than that of the surface pressure at which defects occur in the ion-exchange membrane 50 in the same configurations, except when the ceramic-particle-containing layer 51 is not present.
FIG. 11 is a diagram illustrating a relationship between the current density and the cell voltage in comparison between a case where the ceramic-particle-containing layer 51 is present in the electrochemical cell 11 according to each embodiment described above and a case where the ceramic-particle-containing layer is not present in the electrochemical cell. The "current density" indicated on the horizontal axis in FIG. 11 means the current density in the cathode catalyst layer 54 and in the anode catalyst layer 56. The "cell voltage" indicated on the vertical axis in FIG. 11 means the magnitude of the voltage applied to the cathode catalyst layer 54 and the anode catalyst layer 56. That is, FIG. 11 also illustrates an I-V characteristic indicating a relationship between the voltage (V) applied to the cathode catalyst layer 54 and the anode catalyst layer 56 and the current (I) flowing in the cathode catalyst layer 54 and in the anode catalyst layer 56 with the applied voltage. The relationship between the current density and the cell voltage illustrated in FIG. 11 is at the time when, for example, the pressing mechanism 90 applies a constant surface pressure. FIG. 11 illustrates results obtained by the analysis of the present inventors. As indicated by the solid curve and the dotted curve in FIG. 11, the voltage applied to the cathode catalyst layer 54 and the anode catalyst layer 56 increases with increasing current density in the cathode catalyst layer 54 and in the anode catalyst layer 56. However, the voltage applied to the cathode catalyst layer 54 and the anode catalyst layer 56 with no ceramic-particle-containing layer 51 interposed therebetween (without the ceramic-particle-containing layer 51) is greater than the voltage applied to the cathode catalyst layer 54 and the anode catalyst layer 56 with the ceramic-particle-containing layer 51 interposed therebetween (with the ceramic-particle-containing layer 51). Therefore, it is understood that the contact resistance generated in the cathode catalyst layer 54 and in the anode catalyst layer 56 is larger in the case of "without the ceramic-particle-containing layer 51" as compared with the case of "with the ceramic-particle-containing layer 51".

Fourth Embodiment

Next, a fourth embodiment will be described.
In the present embodiment, the thickness of the ceramic-particle-containing layer 51 (the first layer 52 and the second layer 53) in the electrochemical cell 11 is greater than the maximum height of the surface roughness (roughness of surface) of the second surface (the first cathode catalyst surface 54a of the cathode catalyst layer 54 and the first anode catalyst surface 56a of the anode catalyst layer 56). Specifically, the thickness (T illustrated in FIG. 3) of the first layer 52 is greater than the maximum height of the surface roughness of the first cathode catalyst surface 54a. The thickness (T illustrated in FIG. 3) of the second layer 53 is greater than a maximum height of the surface roughness of the first anode catalyst surface 56a. The term "surface roughness" as used herein means, for example, the roughness of surface defined in JIS B 0601:1994, JIS B 0031:1994, or the like. The maximum height (Rmax) of the surface roughness refers to a value which is obtained in a manner that, for example, from a roughness profile, only a sampling length is extracted in the direction of the mean line thereof, the interval between the profile peak line and the profile valley line of the extracted portion is measured in the direction of the vertical magnification of the roughness profile, and this value is expressed in micrometers (µm).

Action and Effect

The present inventors have found that the probability of occurrence of defects occurring in the ion-exchange membrane 50 is reduced when increasing the surface pressure exerted by the pressing mechanism 90 in a case where the thickness of the ceramic-particle-containing layer 51 is greater than the maximum height of the surface roughness of the second surface as compared with a case where the thickness of the ceramic-particle-containing layer 51 is smaller than the maximum height of the surface roughness of the second surface. Therefore, according to the configuration of the present embodiment, the action and effect described in the first embodiment can be achieved with higher accuracy. That is, the contact resistance can be reduced by increasing the surface pressure exerted by the pressing mechanism 90, and as a result, better I-V characteristics of the electrochemical cell 11 can be achieved.

Other Embodiments

As described above, the embodiments of the present disclosure have been described in detail with reference to the drawings, however, the specific configuration is not limited to the configuration of the embodiments, and addition, omission, substitution, and other modifications of the configuration can be made without deviating from the essence of the present disclosure.
For example, the ceramic-particle-containing layer 51 may be disposed only further toward the cathode catalyst layer 54 side than the ion-exchange membrane 50. That is, the second layer 53 is not required to present between the ion-exchange membrane 50 and the anode catalyst layer 56, and only the first layer 52 may be disposed between the ion-exchange membrane 50 and the cathode catalyst layer 54. In this case, the anode catalyst layer 56 may be surface pressure-bonded to the second exchange membrane surface 50b of the ion-exchange membrane 50, for example. The ceramic-particle-containing layer 51 may be disposed only further toward the anode catalyst layer 56 side than the ion-exchange membrane 50. That is, the first layer 52 is not required to present between the ion-exchange membrane 50 and the cathode catalyst layer 54, and only the second layer 53 may be disposed between the ion-exchange membrane 50 and the anode catalyst layer 56. In summary, the ceramic-particle-containing layer 51 may be provided only on one surface (the first exchange membrane surface 50a or the second exchange membrane surface 50b) of the ion-exchange membrane 50. Note that, in this case, the cathode catalyst layer 54 may be surface pressure-bonded to the first exchange membrane surface 50a of the ion-exchange membrane 50, for example.
The ceramic-particle-containing layer 51 (the first layer 52 and the second layer 53) is not required to be in contact with the cathode catalyst layer 54 and the anode catalyst layer 56. In this case, a layer made of, for example, another material may be interposed between the ceramic-particle-containing layer 51 and the cathode catalyst layer 54 and between the ceramic-particle-containing layer 51 and the anode catalyst layer 56. The ceramic-particle-containing layer 51 (the first layer 52 and the second layer 53) is not required to be in contact with the ion-exchange membrane 50 (the first exchange membrane surface 50a and the second exchange membrane surface 50b). In this case, a layer made of, for example, another material may be interposed between the ceramic-particle-containing layer 51 and the ion-exchange membrane 50.

Supplementary Note

The electrochemical cell 11 and the electrolyzer 1 described in each embodiment are understood as follows, for example.

(1) An electrochemical cell 11 according to a first embodiment includes: an ion-exchange membrane 50; a cathode catalyst layer 54 disposed further toward one side than the ion-exchange membrane 50; an anode catalyst layer 56 disposed further toward the other side, opposite to the one side, than the ion-exchange membrane 50; and a ceramic-particle-containing layer 51 disposed between the cathode catalyst layer 54 and the ion-exchange membrane 50, and/or between the anode catalyst layer 56 and the ion-exchange membrane 50.
This allows, when a surface pressure acts between the ion-exchange membrane 50 and the cathode catalyst layer 54 and between the ion-exchange membrane 50 and the anode catalyst layer 56, the cathode catalyst layer 54 and the anode catalyst layer 56 to press the ceramic-particle-containing layer 51. That is, the asperities of the cathode catalyst layer 54 and of the anode catalyst layer 56 do not have a direct influence on the ion-exchange membrane 50.
(2) The electrochemical cell 11 according to a second embodiment may be the electrochemical cell 11 according to (1), and the electrochemical cell 11 may be an electrolysis cell.
This allows the above-described action to be achieved in the electrolysis cell. That is, durability of the electrolysis cell can be improved.
(3) An electrochemical cell 11 according to a third embodiment is the electrochemical cell 11 according to (1) or (2), in which the ceramic-particle-containing layer 51 may be in contact with the cathode catalyst layer 54 or the anode catalyst layer 56, and is in contact with the ion-exchange membrane 50.
Accordingly, when a surface pressure acts between the ion-exchange membrane 50 and the cathode catalyst layer 54 or between the ion-exchange membrane 50 and the anode catalyst layer 56, the cathode catalyst layer 54 or the anode catalyst layer 56 directly presses the ceramic-particle-containing layer 51. That is, the asperities generated in the cathode catalyst layer 54 or in the anode catalyst layer 56 have a direct influence on the ceramic-particle-containing layer 51. Therefore, there is no need to provide, other than the ceramic-particle-containing layer 51, any dedicated layer or the like for absorbing the impact of direct pressure from the cathode catalyst layer 54 or from the anode catalyst layer 56. This allows, for example, an increase in overall electrical resistance of the electrochemical cell 11 to be suppressed, and electrolysis in the electrochemical cell 11 to can be efficiently realized.
(4) The electrochemical cell 11 according to a fourth embodiment is the electrochemical cell 11 according to any one of (1) to (3), in which the ceramic-particle-containing layer 51 may have insulating properties.
As a result, for example, even when a defect such as perforation occurs in the ion-exchange membrane 50 due to use of the electrochemical cell 11 over time, the ceramic-particle-containing layer 51 having insulating properties is interposed between the cathode catalyst layer 54 and the anode catalyst layer 56, so that it is possible to suppress electricity from flowing between the cathode catalyst layer 54 and the anode catalyst layer 56.
(5) An electrochemical cell 11 according to a fifth embodiment is the electrochemical cell 11 according to (3), in which the ion-exchange membrane 50 may include a first surface in contact with the ceramic-particle-containing layer 51, the cathode catalyst layer 54 or the anode catalyst layer 56 may include a second surface in contact with the ceramic-particle-containing layer 51, and the second surface may be rougher than compared to the first surface.
As a result, even if the roughness of the second surface of the cathode catalyst layer 54 or of the anode catalyst layer 56 is greater than the roughness of the first surface of the ion-exchange membrane 50, an impact associated with action of the surface pressure can be absorbed by the ceramic-particle-containing layer 51. Therefore, it is possible to further avoid occurrence of a defect such as damage in the ion-exchange membrane 50.
(6) An electrochemical cell 11 according to a sixth embodiment is the electrochemical cell 11 according to (5), in which the thickness of the ceramic-particle-containing layer 51 may be greater than the maximum height of the surface roughness of the second surface.
The present inventors have found that the probability of defects occurring in the ion-exchange membrane 50 is reduced when increasing the surface pressure in a case where the thickness of the ceramic-particle-containing layer 51 is greater than the maximum height of the surface roughness of the second surface as compared with a case where the thickness of the ceramic-particle-containing layer 51 is smaller than the maximum height of the surface roughness of the second surface. That is, the action described above can be realized with higher accuracy by more specific setting.
(7) An electrochemical cell 11 according to a seventh embodiment is the electrochemical cell 11 according to any one of (1) to (6), in which the ceramic-particle-containing layer 51 may contain ceramic particles Cs and a polymer binder.
Thereby, since the polymer binder binds the ceramic particles Cs to each other, the retentivity of the ceramic-particle-containing layer 51 can be enhanced. Therefore, for example, as compared with the case where there is provided the ceramic-particle-containing layer 51 containing no polymer binder, it is possible to suppress the ceramic particles Cs from falling off from the ceramic-particle-containing layer 51 due to use of the electrochemical cell 11 over time.
(8) An electrochemical cell 11 according to an eighth embodiment is the electrochemical cell 11 according to any one of (1) to (7), in which the ceramic-particle-containing layer 51 may contain ceramic particles Cs and an ionomer.
This allows ions to easily pass through the ceramic-particle-containing layer 51 from the cathode catalyst layer 54 toward the anode catalyst layer 56, for example, as compared with the case where there is provided the ceramic-particle-containing layer 51 not containing an ionomer. That is, the electrical resistance of the ceramic-particle-containing layer 51 can be reduced.
(9) An electrochemical cell 11 according to a ninth embodiment is the electrochemical cell 11 according to (8), in which the ion-exchange membrane 50 includes a first polymer, and the ionomer may include a second polymer, the second polymer being the same as the first polymer or having the same molecular skeleton as the first polymer.
This enhances a chemical compatibility (affinity) with the ion-exchange membrane 50, and the adhesion between the ceramic-particle-containing layer 51 and the ion-exchange membrane 50 is enhanced when the ceramic-particle-containing layer 51 is in contact with the ion-exchange membrane 50, as compared with, for example, a case where there is provided the ceramic-particle-containing layer 51 not containing the second polymer.
(10) An electrochemical cell 11 according to a tenth embodiment may be the electrochemical cell 11 according to any one of (1) to (9), in which the ceramic-particle-containing layer 51 may be a coating layer containing ceramic particles Cs.
As a result, manufacturability is improved as compared with a case where, for example, the ceramic-particle-containing layer 51 (e.g., a sheet-like material containing ceramic particles Cs) is separately prepared and then adhered.
(11) An electrochemical cell 11 according to an eleventh embodiment is the electrochemical cell 11 according to any one of (1) to (10), and further includes a pressing mechanism 90 that applies a predetermined surface pressure between the ion-exchange membrane 50 and the cathode catalyst layer 54 with the ceramic-particle-containing layer 51 interposed therebetween or between the ion-exchange membrane 50 and the anode catalyst layer 56 with the ceramic-particle-containing layer 51 interposed therebetween, in which the predetermined surface pressure may be adjusted to a value higher than that of a surface pressure at which a defect occurs in the ion-exchange membrane 50 in the same configurations, except when the ceramic-particle-containing layer 51 is not present.
The present inventors have compared and studied an electrochemical cell 11 including an ion-exchange membrane 50 and a cathode catalyst layer 54 or an anode catalyst layer 56 with a ceramic-particle-containing layer 51 interposed therebetween, and an electrochemical cell having the same configurations except when the ceramic-particle-containing layer 51 is not present. As a result, the present inventors have found that the contact resistance of the cathode catalyst layer 54 or of the anode catalyst layer 56 in the former electrochemical cell 11 is reduced with increasing the surface pressure acting between the electrochemical cell and the ion-exchange membrane 50, without causing a defect in the ion-exchange membrane 50, as compared with the latter electrochemical cell. That is, the action described above can be realized with higher accuracy by more specific setting.
(12) An electrolyzer 1 according to a twelfth embodiment includes an electrolysis cell, the electrolysis cell being the electrochemical cells 11 according to any one of (1) to (11), an electrolyte supply unit 20 that supplies an electrolyte to the electrolysis cell, and a power supply unit 30 that applies voltage to the electrolysis cell.

Industrial Applicability

Reference Signs List

1...Electrolyzer 10...Cell stack 11...Electrochemical cell 11h...Insertion hole 20...Electrolyte supply unit 20a...Cathode side supply unit 20b...Anode side supply unit 21...Hydrogen gas-liquid separation device 22...First pump 23...Hydrogen recovery unit 24... First electrolyte supply unit 26...Oxygen gas-liquid separation device 27...Second pump 28...Oxygen recovery unit 29...Second electrolyte supply unit 30...Power supply unit 40...Electrolytic bath 41...First separator 41a...First inner surface 41b, 42b...Surface 41e1...First separator end portion of first separator 41e2...Second separator end portion of first separator 42...Second separator 42a...Second inner surface 42e1...First separator end portion of second separator 42e2...Second separator end portion of second separator 43...Membrane electrode assembly 47...Cathode 48... Anode 50...Ion-exchange membrane 50a...First exchange membrane surface 50b...Second exchange membrane surface 50e...Outer edge portion 51...Ceramic-particle-containing layer 52...First layer 53...Second layer 54...Cathode catalyst layer 54a...First cathode catalyst surface 54b...Second cathode catalyst surface 55...Cathode power feeder 55a...Cathode surface 56...Anode catalyst layer 56a...First anode catalyst surface 56b...Second anode catalyst surface 57...Anode power feeder 57a...Anode surface 61...First current collector 62...Second current collector 63...First insulator 64...Second insulator 65...First insulating material 66...Second insulating material 67...First end flange 68...Second end flange 70...Support part 71...First support part 72...Second support part 80...Sealing part 81...First sealing part 82...Second sealing part 90...Pressing mechanism 91...First component 92...Second component Ad...Non-ceramic particles C...Central region Cs...Ceramic particles FP1...First flow path FP2...Second flow path L1, L2, L3, L4...Piping line S...Accommodation space Sa...Cathode chamber Sb... Anode chamber

Claims

An electrochemical cell, comprising:
an ion-exchange membrane;

a cathode catalyst layer disposed further toward one side than the ion-exchange membrane;

an anode catalyst layer disposed further toward the other side, opposite to the one side, than the ion-exchange membrane; and

a ceramic-particle-containing layer disposed between the cathode catalyst layer and the ion-exchange membrane, and/or between the anode catalyst layer and the ion-exchange membrane.
The electrochemical cell according to claim 1,
wherein the electrochemical cell is an electrolysis cell.
The electrochemical cell according to claim 1,
wherein the ceramic-particle-containing layer is in contact with the cathode catalyst layer or the anode catalyst layer, and is in contact with the ion-exchange membrane.
The electrochemical cell according to claim 3,
wherein the ceramic-particle-containing layer has insulating properties.
The electrochemical cell according to claim 3,
wherein the ion-exchange membrane comprises a first surface in contact with the ceramic-particle-containing layer, and

the cathode catalyst layer or the anode catalyst layer comprises a second surface in contact with the ceramic-particle-containing layer, and

the second surface is rougher compared to the first surface.
The electrochemical cell according to claim 5,
wherein a thickness of the ceramic-particle-containing layer is greater than a maximum height of a surface roughness of the second surface.
The electrochemical cell according to any one of claims 1 to 3,
wherein the ceramic-particle-containing layer comprises ceramic particles and a polymer binder.
The electrochemical cell according to any one of claims 1 to 3,
wherein the ceramic-particle-containing layer comprises ceramic particles and an ionomer.
The electrochemical cell according to claim 8,
wherein the ion-exchange membrane comprises a first polymer, and

the ionomer comprises a second polymer, the second polymer being the same as the first polymer or having the same molecular skeleton as the first polymer.
The electrochemical cell according to any one of claims 1 to 3,
wherein the ceramic-particle-containing layer is a coating layer comprising ceramic particles.
The electrochemical cell according to any one of claims 1 to 3,
further comprising a pressing mechanism configured to apply a predetermined surface pressure between the ion-exchange membrane and the cathode catalyst layer with the ceramic-particle-containing layer interposed therebetween, or between the ion-exchange membrane and the anode catalyst layer with the ceramic-particle-containing layer interposed therebetween,

wherein the predetermined surface pressure is adjusted to a value higher than that of a surface pressure at which a defect occurs in the ion-exchange membrane under the same configurations except when the ceramic-particle-containing layer is not present.
An electrolyzer, comprising:
an electrolysis cell, the electrolysis cell being the electrochemical cell described in claim 1 or 2;

an electrolyte supply unit configured to supply an electrolyte to the electrolysis cell; and

a power supply unit configured to apply voltage to the electrolysis cell.