Electrolysis cell and electrolysis device

Abstract

This electrolysis cell comprises: an ion exchange membrane; and a membrane-like electrode which is disposed in contact with at least the surface on the anode side among the anode side and the cathode side of the ion exchange membrane and is formed from a porous body of a stainless alloy containing a nickel element. The electrode has: an inner layer member disposed on the surface side; and an outer layer member disposed outside the inner layer member and having a higher porosity than the inner layer member.

Description

Electrolytic cell and electrolytic device

[0001] This application claims priority to Japanese Patent Application No. 2024-016345, filed February 6, 2024, the contents of which are incorporated herein by reference.

[0002] Water electrolysis devices (electrolysis devices) are known as devices for generating hydrogen. In this type of device, an electrolytic cell separated into a cathode chamber and an anode chamber by an ion exchange membrane is filled with water, and water is electrolyzed by supplying electricity to the cathode and anode. In the cathode chamber, hydrogen is generated by a reaction between water and electrons. The hydroxide ions produced by this reaction permeate the ion exchange membrane and reach the anode chamber. In the anode chamber, oxygen and water are generated from these hydroxide ions. By continuing this reaction, large amounts of hydrogen can be obtained.

[0003] On both sides of the ion exchange membrane in the thickness direction, a current supply is disposed between the anode and the cathode. Conventionally, current supply has been made of a metal substrate or carbon supported with a precious metal such as platinum or iridium oxide. However, the use of precious metals is costly, and there has been a growing demand for alternative configurations. Therefore, the device disclosed in Patent Document 1 below uses a sintered body of powdered stainless steel as the electrode. It is said that porous stainless steel electrodes can be obtained by sintering the powder.

[0004] Patent No. 7179314

[0005] Here, gas is generated inside the porous electrode from the surface side of the ion exchange membrane. This gas passes through the pores inside the electrode and is released into the electrolyte. However, if a porous electrode is simply used as described above, the resistance to gas passage increases toward the outside of the electrode, and the generated gas remains inside the electrode. In other words, the gas discharge efficiency decreases. As a result, there is a problem in that the desired gas recovery efficiency cannot be achieved.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an electrolytic cell and an electrolytic device that can be manufactured and operated inexpensively and have improved gas recovery efficiency.

[0007] In order to solve the above problems, the electrolytic cell according to the present disclosure includes an ion exchange membrane and a membrane electrode formed of a porous body of a stainless steel alloy containing nickel, which is provided so as to abut on at least the anode side surface of the anode side and cathode side of the ion exchange membrane, and the electrode has an inner layer member provided on the surface side, and an outer layer member provided outside the inner layer member and having a higher porosity than the inner layer member.

[0008] The electrolysis device according to the present disclosure includes the electrolysis cell described above, an electrolyte solution supply unit that supplies an electrolyte solution to the electrolysis cell, and a power supply unit that applies a voltage to the electrolysis cell.

[0009] According to the present disclosure, it is possible to provide an electrolytic cell and an electrolytic device that can be manufactured and operated inexpensively and have improved gas recovery efficiency.

[0010] Fig. 1 is a schematic diagram showing the configuration of an electrolysis device according to an embodiment of the present disclosure; Fig. 2 is a schematic cross-sectional view showing the configuration of an electrolysis cell according to an embodiment of the present disclosure; Fig. 3 is an exploded perspective view showing the configuration of an electrolysis cell according to an embodiment of the present disclosure; Fig. 4 is an enlarged cross-sectional view of an anode and a cathode according to an embodiment of the present disclosure; Fig. 5 is a graph showing an example of the cell voltage (overvoltage) over time of an electrolysis cell according to an embodiment of the present disclosure; Fig. 6 is an enlarged cross-sectional view showing modified examples of an anode and a cathode according to an embodiment of the present disclosure;

[0011] Electrolytic cells and electrolytic devices according to embodiments of the present disclosure will be described below with reference to the drawings. In the following description, components having the same or similar functions will be denoted by the same reference numerals. In the present disclosure, "facing" means that two components overlap when viewed in a certain direction, and may also include the case where another component (e.g., another layer) exists between the two components.

[0012] First, the Z direction, X direction, and Y direction are defined. The Z direction is the direction from a first separator 41 to a second separator 42 (described later) (see FIG. 2 ). The X direction is a direction intersecting (e.g., perpendicular to) the Z direction and is a direction from a center C of a membrane electrode assembly 43 (described later) toward one end of the membrane electrode assembly 43. The Y direction is a direction intersecting (e.g., perpendicular to) the Z direction and the X direction and is, for example, the depth direction of the paper in FIG. 2 . In this disclosure, "area" means the area when viewed in the Z direction (i.e., the area extending in the X and Y directions). Furthermore, in this disclosure, "external size" means the external size when viewed in the Z direction. In other words, "external size" and "area" may mean substantially the same thing and may be interpreted interchangeably as appropriate.

[0013] 1. Configuration of Electrolysis Device Fig. 1 is a schematic diagram showing the overall configuration of an electrolysis device 1 according to this embodiment. The electrolysis device 1 is, for example, a device that generates hydrogen by electrolyzing water contained in an electrolytic solution. The electrolysis device 1 is, for example, an anion exchange membrane (AEM) type electrolysis device. However, the electrolysis device 1 is not limited to the above example, and may be a different type of electrolysis device, such as a device that electrolytically reduces carbon dioxide.

[0014] The electrolysis device 1 includes, for example, an electrolysis cell stack 10 , an electrolyte supply unit 20 , and a power supply unit 30 .

[0015] (Electrolytic Cell Stack) The electrolytic cell stack 10 is an assembly of multiple electrolytic cells 11. For example, the electrolytic cell stack 10 is formed by arranging multiple electrolytic cells 11 in one direction. Each electrolytic cell 11 includes a cathode chamber Sa and an anode chamber Sb. The electrolytic cells 11 will be described in detail later.

[0016] (Electrolyte Solution Supply Unit) The electrolyte solution supply unit 20 is a supply unit that supplies an electrolyte solution to each electrolytic cell 11. The electrolyte solution is, for example, pure water or an alkaline aqueous solution. The electrolyte solution supply unit 20 includes a cathode side supply unit 20a and an anode side supply unit 20b.

[0017] The cathode side supply unit 20a is a supply unit that supplies the electrolytic solution to the cathode chamber Sa of each electrolytic cell 11. The cathode side supply unit 20a includes, for example, a hydrogen gas-liquid separator 21, a first pump 22, a hydrogen recovery unit 23, a first electrolytic solution supply unit 24, and piping lines L1 and L2.

[0018] The hydrogen-gas-liquid separator 21 stores the electrolytic solution. A supply port of the hydrogen-gas-liquid separator 21 is connected to the cathode chamber Sa of the electrolytic cell 11 via a piping line L1. A first pump 22 is provided in the piping line L1 and sends the electrolytic solution stored in the hydrogen-gas-liquid separator 21 toward the cathode chamber Sa of the electrolytic cell 11.

[0019] A return port of the hydrogen-gas-liquid separator 21 is connected to the cathode chamber Sa of the electrolytic cell 11 via a piping line L2. An electrolytic solution containing hydrogen produced in the electrolytic cell 11 flows into the hydrogen-gas-liquid separator 21 from the electrolytic cell 11. The hydrogen-gas-liquid separator 21 has a gas-liquid separation unit that separates the hydrogen contained in the electrolytic solution. The hydrogen separated from the electrolytic solution by the hydrogen-gas-liquid separator 21 is recovered by a hydrogen recovery unit 23. The hydrogen-gas-liquid separator 21 is replenished with electrolytic solution from a first electrolytic solution supply unit 24.

[0020] On the other hand, the anode side supply unit 20b is a supply unit that supplies the electrolytic solution to the anode chamber Sb of each electrolytic cell 11. The anode side supply unit 20b includes, for example, an oxygen gas-liquid separator 26, a second pump 27, an oxygen recovery unit 28, a second electrolytic solution supply unit 29, and piping lines L3 and L4.

[0021] The oxygen-gas-liquid separator 26 stores the electrolytic solution. A supply port of the oxygen-gas-liquid separator 26 is connected to the anode chamber Sb of the electrolytic cell 11 via a piping line L3. A second pump 27 is provided in the piping line L3 and sends the electrolytic solution stored in the oxygen-gas-liquid separator 26 toward the anode chamber Sb of the electrolytic cell 11.

[0022] A return port of the oxygen-gas-liquid separator 26 is connected to the anode chamber Sb of the electrolytic cell 11 via a piping line L4. The oxygen-containing electrolytic solution produced in the electrolytic cell 11 flows into the oxygen-gas-liquid separator 26 from the electrolytic cell 11. The oxygen-gas-liquid separator 26 has a gas-liquid separation unit that separates the oxygen contained in the electrolytic solution. The oxygen separated from the electrolytic solution by the oxygen-gas-liquid separator 26 is recovered by an oxygen recovery unit 28. The oxygen-gas-liquid separator 26 is replenished with electrolytic solution from a second electrolytic solution supply unit 29.

[0023] (Power Supply Unit) The power supply unit 30 is a DC power supply device that applies a voltage to the electrolytic cell 11. The power supply unit 30 applies a DC voltage required for electrolysis of the electrolyte between the anode and cathode of the electrolytic cell 11.

[0024] 2. Configuration of Electrolytic Cell 2.1 Basic Structure of Electrolytic Cell Next, the electrolytic cell 11 will be described in detail. Fig. 2 is a cross-sectional view schematically showing the electrolytic cell 11. The electrolytic cell 11 includes, for example, a first separator 41, a second separator 42, and a membrane electrode assembly 43.

[0025] (First Separator) The first separator 41 is a member that defines one side of the internal space S of the electrolysis cell 11. The internal space S is a space that includes a cathode chamber Sa and an anode chamber Sb, which will be described later. The first separator 41 has, for example, a rectangular plate shape and is made of a metal member. A negative voltage is applied to the first separator 41 from the power supply unit 30, for example, via a first current collector 61 (see FIG. 3), which will be described later.

[0026] The first separator 41 has a first end 41e1 (e.g., a lower end) and a second end 41e2 (e.g., an upper end) located opposite the first end 41e1. The above-mentioned piping line L1 is connected to the first end 41e1 of the first separator 41. The above-mentioned piping line L2 is connected to the second end 41e2 of the first separator 41. The first separator 41 has a first inner surface 41a facing the cathode chamber Sa described below. The first inner surface 41a is formed with a first flow path FP1 through which the electrolytic solution supplied from the piping line L1 flows. The first flow path FP1 is, for example, a groove provided in the first inner surface 41a. The electrolytic solution that has flowed through the first flow path FP1 is discharged to the outside of the electrolytic cell 11 through the piping line L2. Note that the structures (e.g., flow path structure) shown in FIG. 2 are merely examples and do not limit the content of this embodiment. For example, various flow channel structures can be used depending on the size, purpose, and usage environment of the device, and this also applies to the structures shown in the other figures.

[0027] (Second Separator) The second separator 42 is disposed with an internal space S between it and at least a part of the first separator 41, and is a member that defines the other side of the internal space S. The second separator 42 is, for example, a rectangular plate and is made of a metal member. A positive voltage is applied to the second separator 42 from the power supply unit 30 via a second current collector 62 (see FIG. 3 ), which will be described later. The first separator 41 and the second separator 42 included in the same electrolytic cell 11 form, as a pair of separators, the electrolytic cell 40 of the electrolytic cell 11.

[0028] The second separator 42 has a first end 42e1 (e.g., a lower end) and a second end 42e2 (e.g., an upper end) located opposite the first end 42e1. The above-mentioned piping line L3 is connected to the first end 42e1 of the second separator 42. The above-mentioned piping line L4 is connected to the second end 42e2 of the second separator 42. The second separator 42 has a second inner surface 42a facing the anode chamber Sb described below. A second flow path FP2 is formed on the second inner surface 42a, through which the electrolytic solution supplied from the piping line L3 flows. The second flow path FP2 is, for example, a groove provided in the second inner surface 42a. The electrolytic solution that has flowed through the second flow path FP2 is discharged to the outside of the electrolytic cell 11 via the piping line L4.

[0029] For ease of explanation, the configuration described herein is one in which the first inner surface 41a of the first separator 41 has a flow path groove (first flow path FP1), and the second inner surface 42a of the second separator 42 has a flow path groove (second flow path FP2). However, for example, the first separator 41 of the electrolysis cell 11 included in the electrolysis cell stack 10 (see FIG. 1 ) may be a bipolar plate having a similar flow path groove (first flow path FP1, shown by a two-dot chain line in FIG. 2 ) on the surface 41b opposite the first inner surface 41a in addition to the first inner surface 41a. Furthermore, the second separator 42 of the electrolysis cell 11 included in the electrolysis cell stack 10 may be a bipolar plate having a similar flow path groove (second flow path FP2, shown by a two-dot chain line in FIG. 2 ) on the surface 42b opposite the second inner surface 42a in addition to the second inner surface 42a. The flow path grooves provided on both surfaces of the first separator 41 may have different shapes and arrangements. Furthermore, the flow path grooves provided on both sides of the second separator 42 may have different shapes and arrangements.

[0030] The membrane electrode assembly (MEA) 43 is a structure in which an ion exchange membrane and electrodes are assembled. The membrane electrode assembly 43 is disposed between a first separator 41 and a second separator 42, and is located in the internal space S. The membrane electrode assembly 43 includes, for example, a first ion exchange membrane 51, a second ion exchange membrane 52, an ionomer layer 53, a cathode 47, and an anode 48.

[0031] The first ion exchange membrane 51 is a membrane that selectively transmits ions. The first ion exchange membrane 51 is, for example, a solid polymer electrolyte membrane. The first ion exchange membrane 51 is, for example, an anion exchange membrane (AEM) that is hydroxide ion conductive. However, the first ion exchange membrane 51 is not limited to the above example and may be a type of ion exchange membrane different from the above example. The first ion exchange membrane 51 is, for example, a rectangular sheet. The outer size of the first ion exchange membrane 51 is smaller than the outer size of the first separator 41 or the second separator 42. The first ion exchange membrane 51 is disposed between the first separator 41 and the second separator 42 and is located in the internal space S described above. The first ion exchange membrane 51 has a first surface 51a facing the first inner surface 41a of the first separator 41 and a second surface 51b located on the opposite side from the first surface 51a. In the internal space S, a cathode chamber Sa is defined between the first surface 51 a of the first ion exchange membrane 51 and the first inner surface 41 a of the first separator 41 .

[0032] In the cathode chamber Sa, when a voltage is applied to the electrolytic cell 11, the following chemical reaction occurs, and hydrogen is produced from the electrolytic solution. In this application, the phrase "XX is produced" may also include the case where other substances are produced simultaneously with the production of XX. The 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. 2H ２ O + 2e － →H ２ +2OH － ...(Chemical 1)

[0033] (Second Ion Exchange Membrane) The second ion exchange membrane 52 is a membrane that selectively transmits ions. The second ion exchange membrane 52 is, for example, a solid polymer electrolyte membrane. The second ion exchange membrane 52 is, for example, an anion exchange membrane with hydroxide ion conductivity. However, the second ion exchange membrane 52 is not limited to the above example and may be an ion exchange membrane of a type different from the above example. The second ion exchange membrane 52 is, for example, in the form of a rectangular sheet. The outer size of the second ion exchange membrane 52 is smaller than the outer size of the first separator 41 or the second separator 42. For example, the outer size of the second ion exchange membrane 52 is the same as the outer size of the first ion exchange membrane 51. The second ion exchange membrane 52 is disposed between the first separator 41 and the second separator 42 and is located in the internal space S described above. The second ion exchange membrane 52 has a third surface 52a facing the second inner surface 42a of the second separator 42 and a fourth surface 52b located on the opposite side to the third surface 52a. In the internal space S, an anode chamber Sb is defined between the third surface 52a of the second ion exchange membrane 52 and the second inner surface 42a of the second separator 42.

[0034] In the anode chamber Sb, when a voltage is applied to the electrolytic cell 11, the following chemical reaction occurs, producing oxygen from the electrolyte: － →1 / 2O ２ +H ２ O + 2e － ...(Case 2)

[0035] As a result, the following chemical reaction occurs in the electrolysis cell 11 as a whole: ２ O → H ２ +1 / 2O ２ ...(Chem.3)

[0036] In this disclosure, ordinal numbers such as "first" and "second" are used in the names of components for the sake of convenience. For example, the names "third" and "fourth" do not imply that the same component is also designated by the names "first" and "second." In this embodiment, the names "third surface 52a" and "fourth surface 52b" of the second ion exchange membrane 52 do not imply that the second ion exchange membrane 52 has a first surface and a second surface. Therefore, the names "third surface 52a" and "fourth surface 52b" may be read as the "first surface 52a" and "second surface 52b" of the second ion exchange membrane 52.

[0037] In this embodiment, the first ion exchange membrane 51 and the second ion exchange membrane 52 are integrated with the second surface 51b of the first ion exchange membrane 51 facing the fourth surface 52b of the second ion exchange membrane 52. In the present disclosure, the phrase "the first ion exchange membrane 51 and the second ion exchange membrane 52 being integrated" does not necessarily mean that the first ion exchange membrane 51 and the second ion exchange membrane 52 are directly bonded to each other, but may also mean that another layer (for example, an ionomer layer 53, which will be described later) is present between the first ion exchange membrane 51 and the second ion exchange membrane 52. It is also possible to adopt a configuration that does not include the ionomer layer 53, or a configuration in which the first ion exchange membrane 51 and the second ion exchange membrane 52 form a single membrane.

[0038] The materials of the first ion exchange membrane 51 and the second ion exchange membrane 52 may be the same or different. For example, the materials of the first ion exchange membrane 51 and the second ion exchange membrane 52 are selected as follows. That is, because no oxidation reaction occurs in the cathode chamber Sa, the first ion exchange membrane 51 does not need to have high oxidation resistance. Therefore, for example, a membrane made of a material with higher ionic conductivity than the second ion exchange membrane 52 is used as the first ion exchange membrane 51. On the other hand, because an oxidation reaction occurs in the anode chamber Sb, it is preferable that the second ion exchange membrane 52 have high oxidation resistance. Therefore, for example, a membrane made of a material with higher oxidation resistance than the first ion exchange membrane 51 is used as the second ion exchange membrane 52.

[0039] An example of a "membrane with high ionic conductivity" is a membrane containing a polystyrene-based or tetraphenyl-based composition in the main chain and an imidazolium group or a quaternary ammonium group in the side chain. An example of a "membrane with high oxidation resistance" is a membrane containing a polysulfone-based or bromobutylstyrene-based composition.

[0040] (Ionomer Layer) The ionomer layer 53 is a layer for bonding the first ion exchange membrane 51 and the second ion exchange membrane 52. The ionomer layer 53 is a layer through which hydroxide ions can pass. The ionomer layer 53 is provided between the second surface 51b of the first ion exchange membrane 51 and the fourth surface 52b of the second ion exchange membrane 52. For example, the ionomer layer 53 is provided over the entire second surface 51b of the first ion exchange membrane 51 and the entire fourth surface 52b of the second ion exchange membrane 52. The thickness of the ionomer layer 53 is, for example, 10 nm or more and 10 μm or less. In this embodiment, the first ion exchange membrane 51 and the second ion exchange membrane 52 are integrated via the ionomer layer 53.

[0041] (Cathode and Anode) The cathode 47 and the anode 48 are in the form of films made of a stainless steel alloy. More specifically, an austenitic stainless steel alloy such as SUS is used for the cathode 47 and the anode 48. In the following description, the cathode 47 and the anode 48 may be collectively referred to as electrodes 60.

[0042] 4, the electrode 60 has an inner layer member 71 and an outer layer member 72. The inner layer member 71 is disposed so as to abut against the first ion exchange membrane 51 or the second ion exchange membrane 52. The outer layer member 72 is laminated on the outside of the inner layer member 71, i.e., on the side opposite to the ionomer layer 53.

[0043] Both the inner layer member 71 and the outer layer member 72 are formed of a porous film of a stainless steel alloy containing nickel. More specifically, a sintered body of stainless steel fiber or a sheet formed by weaving stainless steel fiber is preferably used. Examples of stainless steel materials that can be used include SUS316, SUS304, Fe-rich SUS, and SUS340. The porosity of the porous body differs between the inner layer member 71 and the outer layer member 72. More specifically, the porosity of the outer layer member 72 is relatively higher than that of the inner layer member 71. Furthermore, the porosity changes stepwise (discontinuously) from the inner layer member 71 to the outer layer member.

[0044] For example, the porosity of the inner layer member 71 is preferably 70% or less, and the porosity of the outer layer member 72 is preferably greater than 70%. The fiber diameter of the fibers constituting these electrodes 60 is preferably 50 μm or less. Furthermore, the air permeability is preferably 3 cm 3 / (cm 2 It is desirable that the airflow resistance is 0.04 kPa·s / m or less (based on measurement according to JIS L 1096A method).

[0045] No catalytic layer made of a noble metal is provided on these electrodes 60. In other words, the electrodes 60 function not only as electrodes themselves but also as power feeders.

[0046] 3 is an exploded perspective view showing the electrolytic cell 11. In addition to the components described above, the electrolytic cell 11 includes, for example, a first current collector 61, a second current collector 62, a first insulator 63, a second insulator 64, a first insulator 65, a second insulator 66, a first end plate 67, and a second end plate 68.

[0047] (First current collector) The first current collector 61 is an electrical connection part 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 (e.g., a copper plate). The first current collector 61 contacts the first separator 41 from the side opposite to the internal space S of the electrolysis cell 11, for example, and is electrically connected to the first separator 41. A negative voltage required for electrolysis in the electrolysis cell 11 is applied to the first current collector 61 from the power supply unit 30. The first current collector 61 may be shared by two adjacent electrolysis cells 11 in the electrolysis cell stack 10.

[0048] (Second current collector) The second current collector 62 is an electrical connection part 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 contacts the second separator 42 from the side opposite to the internal space S of the electrolysis cell 11, for example, and is electrically connected to the second separator 42. A positive voltage required for electrolysis in the electrolysis cell 11 is applied to the second current collector 62 from the power supply unit 30. The second current collector 62 may be shared by two adjacent electrolysis cells 11 in the electrolysis cell stack 10.

[0049] (First insulator) The first insulator 63 is a member that provides insulation between the outer periphery of the first separator 41 and the outer periphery of the second separator 42. The first insulator 63 is attached to the first inner surface 41 a of the first separator 41 and covers the end of the first inner surface 41 a. 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-like resin such as PTFE (polytetrafluoroethylene).

[0050] (Second Insulator) Similar to the first insulator 63, the second insulator 64 is a member that provides insulation between the outer periphery of the first separator 41 and the outer periphery of the second separator 42. The second insulator 64 is attached to the second inner surface 42a of the second separator 42 and covers the end of the second inner surface 42a. 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. The first insulator 63 and the second insulator 64 may also be used as an integrated insulator.

[0051] (First Insulating Material) The first insulating material 65 is located between the first current collector 61 and the first end plate 67. The outer size of the first insulating material 65 is, for example, the same as or larger than the outer size of the first current collector 61.

[0052] (Second Insulating Material) The second insulating material 66 is located between the second current collector 62 and the second end plate 68. The outer size of the second insulating material 66 is, for example, the same as or larger than the outer size of the second current collector 62.

[0053] (First End Plate) The first end plate 67 is located on the opposite side of the first insulating material 65 with respect to the internal space S of the electrolysis cell 11. The outer size of the first end plate 67 is larger than the outer size of the first insulating material 65, for example.

[0054] (Second End Plate) The second end plate 68 is located on the opposite side of the second insulating material 66 with respect to the internal space S of the electrolysis cell 11. The outer size of the second end plate 68 is larger than the outer size of the second insulating material 66, for example.

[0055] The electrolytic cell 11 is not limited to the configuration described above. For example, when a plurality of electrolytic cells 11 are arranged side by side in the electrolytic cell stack 10, two adjacent electrolytic cells 11 among the plurality of electrolytic cells 11 may share a first separator 41 or a second separator 42, which is a bipolar plate. In this case, a current collector (first current collector 61 or second current collector 62), an insulator (first insulator 63 or second insulator 64), an insulating material (first insulator 65 or second insulator 66), or an end plate (first end plate 67 or second end plate 68) may not be present between the two adjacent electrolytic cells 11.

[0056] (Effects) Here, gas is generated inside the porous electrode from the surface side of the ion exchange membrane. This gas passes through the pores inside the electrode and is released into the electrolyte. However, if a porous electrode is simply used as described above, the resistance to gas passage increases toward the outside of the electrode, and the generated gas remains inside the electrode. In other words, the gas discharge efficiency decreases. As a result, there is a problem in that the desired gas recovery efficiency cannot be achieved. To solve this problem, the present embodiment employs the above-mentioned configurations.

[0057] According to the above configuration, the electrode 60 is composed of an inner layer member 71 and an outer layer member 72, with the outer layer member 72 having a relatively high porosity. This allows gas generated in the inner layer member 71 by electrolysis to be smoothly released to the outside through the relatively large pores in the outer layer member 72. In other words, the reduced gas flow resistance significantly improves the gas discharge efficiency. This significantly improves the gas recovery efficiency of the electrolytic cell 11. Furthermore, because a catalyst layer made of a precious metal, which has been conventionally used, is not used, the costs required for manufacturing and operating the electrolytic cell 11 can be significantly reduced. This allows for further reduction in the cost of the generated gas, which is the final product.

[0058] Furthermore, as shown by the dashed line or the two-dot chain line in Figure 5, the electrode 60 of this embodiment, shown by the solid line, can stably reduce the cell voltage (overvoltage) compared to when an electrode power supply supporting a precious metal catalyst is used. In other words, the disadvantages of not using a precious metal catalyst are eliminated, and electrolysis can proceed efficiently and stably.

[0059] According to the above configuration, the electrodes 60 can be configured without using a precious metal catalyst on either the anode or cathode side. This allows for a further significant reduction in the costs required for manufacturing and operating the electrolysis cell 11. This allows for even further reduction in the cost of the generated gas, which is the final product.

[0060] According to the above configuration, the porosity changes stepwise from the inner layer member 71 to the outer layer member 72. Therefore, electrodes can be easily and inexpensively constructed by bonding together multiple types of porous members having different porosities or by using a gradient material whose porosity changes intermittently. This allows for a further significant reduction in the costs required for manufacturing and operating the electrolytic cell 11. This allows for even further reduction in the cost of the generated gas, which is the final product.

[0061] (Other Embodiments) Although the embodiments of the present disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like within the scope that does not deviate from the gist of the present disclosure are also included.

[0062] For example, as a modified example, as shown in Fig. 6, it is possible to adopt a configuration in which the porosity changes continuously from the inner layer member 71 to the outer layer member 72. In this case, the boundary between the inner layer member 71 and the outer layer member 72 is defined as lying on the above-mentioned imaginary plane with a porosity of 70%.

[0063] Here, the amount of gas generated increases toward the inner layer member 71 and decreases toward the outer layer member 72. Therefore, a configuration is required that allows the gas inside to be efficiently released to the outside, i.e., to the outside of the electrode. According to the above configuration, the porosity continuously changes from the inner layer member 71 to the outer layer member 72. As a result, the gas generated inside moves toward the outside, which has a higher porosity, entraining gas generated along the way. This further reduces the apparent airflow resistance, further improving the gas discharge efficiency. Therefore, it is possible to significantly improve the gas recovery efficiency of the electrolytic cell 11. An electrode 60 with such a continuously changing porosity can be easily obtained, for example, by three-dimensional additive manufacturing.

[0064] In the above embodiment, an example has been described in which one inner layer member 71 and one outer layer member 72 are laminated. However, it is also possible to configure an electrode 60 having three or more layers overall by laminating a plurality of inner layer members 71 and a plurality of outer layer members 72. This configuration can also provide the same effects as those described above.

[0065] Furthermore, in the above embodiment, an example in which the electrode 60 is used on both the cathode side and the anode side has been described. However, the electrode 60 may be applied only to the anode side, and carbon carrying a metal catalyst may be used on the cathode side. In this case, the catalyst includes one or more of nickel, nickel alloy, cerium oxide, lanthanum oxide, and platinum. Platinum-carrying carbon is particularly preferred. Even in this case, the same effects as those described above can be obtained.

[0066] <Additional Notes> The electrolytic cell and electrolytic device described in each embodiment can be understood, for example, as follows.

[0067] (1) The electrolytic cell 11 according to the first aspect includes ion exchange membranes 51, 52 and a membrane-like electrode 60 made of a porous stainless steel alloy containing nickel, which is provided so as to abut on at least the anode side surface of the anode and cathode sides of the ion exchange membranes 51, 52. The electrode 60 has an inner layer member 71 provided on the surface side, and an outer layer member 72 provided outside the inner layer member 71 and having a higher porosity than the inner layer member 71.

[0068] According to the above configuration, the electrode 60 is composed of the inner layer member 71 and the outer layer member 72, and the porosity is relatively high in the outer layer member 72. This allows gas generated in the inner layer member 71 by electrolysis to be smoothly released to the outside through the relatively large voids in the outer layer member 72.

[0069] (2) The electrolytic cell 11 according to the second aspect is the electrolytic cell 11 of (1), in which the membrane-like electrodes 60 are provided on both the anode side and the cathode side of the ion exchange membranes 51, 52.

[0070] According to the above configuration, the electrode 60 can be configured without using a noble metal catalyst on either the anode side or the cathode side.

[0071] (3) The electrolytic cell 11 according to a third aspect is the electrolytic cell 11 according to (1) or (2), in which the porosity changes stepwise from the inner layer member 71 to the outer layer member 72.

[0072] According to the above configuration, the porosity changes stepwise from the inner layer member 71 to the outer layer member 72, so that an electrode can be easily and inexpensively constructed simply by bonding together multiple types of porous members having different porosities.

[0073] (4) The electrolytic cell 11 according to a fourth aspect is the electrolytic cell 11 according to (1) or (2), in which the porosity changes continuously from the inner layer member 71 to the outer layer member 72.

[0074] According to the above configuration, the porosity changes continuously from the inner layer member 71 to the outer layer member 72. As a result, gas generated on the inside moves toward the outside, where the porosity is higher, entraining gas generated along the way. This further reduces the apparent airflow resistance, thereby further improving the gas discharge efficiency.

[0075] (5) The electrolytic cell 11 according to a fifth aspect is the electrolytic cell 11 according to any one of aspects (1) to (4), wherein the porosity of the inner layer member 71 is 70% or less, and the porosity of the outer layer member 72 is greater than 70%.

[0076] According to the above-described configuration, the gas generated in the inner layer member 71 by electrolysis can be smoothly released to the outside through the relatively large voids in the outer layer member 72 .

[0077] (6) The electrolysis device 1 according to the sixth aspect includes an electrolysis cell 11 according to any one of the aspects (1) to (5), an electrolyte solution supply unit 20 that supplies an electrolyte solution to the electrolysis cell 11, and a power supply unit 30 that applies a voltage to the electrolysis cell 11.

[0078] According to the above configuration, it is possible to provide an electrolysis device 1 that can be manufactured and operated at low cost and has improved gas recovery efficiency.

[0079] According to the present disclosure, it is possible to provide an electrolytic cell and an electrolytic device that can be manufactured and operated inexpensively and have improved gas recovery efficiency.

[0080] DESCRIPTION OF SYMBOLS 1...Electrolysis device 10...Electrolytic cell stack 11, 11A, 11B...Electrolytic cell 20...Electrolyte solution supply section 30...Power supply section 40...Electrolytic cell 41...First separator 42...Second separator 47...Cathode 48...Anode 51...First ion exchange membrane 51a...First surface 51b...Second surface 52...Second ion exchange membrane 52a...Third surface 52b...Fourth surface 53...Ionomer layer 71...Inner layer member 72...Outer layer member

Claims

1. An electrolytic cell comprising: an ion exchange membrane; and a membrane electrode formed of a porous body of a stainless steel alloy containing nickel, which is provided so as to abut on at least the anode side surface of the ion exchange membrane between an anode side and a cathode side, wherein the electrode has an inner layer member provided on the surface side; and an outer layer member provided outside the inner layer member and having a higher porosity than the inner layer member.

2. The electrolytic cell according to claim 1, wherein the membrane electrodes are provided on both the anode side and the cathode side of the ion exchange membrane.

3. The electrolytic cell according to claim 1 or 2, wherein the porosity changes stepwise from the inner layer member to the outer layer member.

4. The electrolytic cell according to claim 1 or 2, wherein the porosity changes continuously from the inner layer member to the outer layer member.

5. An electrolytic cell according to claim 1 or 2, wherein the porosity of the inner layer member is 70% or less, and the porosity of the outer layer member is greater than 70%.

6. An electrolysis device comprising: the electrolysis cell according to claim 1 or 2; an electrolyte solution supply unit that supplies an electrolyte solution to the electrolysis cell; and a power supply unit that applies a voltage to the electrolysis cell.

Images