Differential pressure electrolysis cells and differential pressure electrolysis stacks

Abstract

To provide a better differential pressure electrolysis cell and differential pressure electrolysis stack. [Solution] A differential pressure electrolytic cell 22 includes a membrane electrode assembly 54, a first separator 48a, a second separator 48b, a first current feeder 56, a second current feeder 62, and a pressing portion 66. The pressing portion includes a sheet portion 86 formed of an electrically insulating polymer material so as to be elastically deformable, and disposed between the second current feeder and the second separator in a state in which it is compressed and deformed in the stacking direction of the membrane electrode assembly.

Description

[Technical Field]

[0001] The present disclosure relates to differential pressure electrolysis cells and differential pressure electrolysis stacks. [Background technology]

[0002] In recent years, research and development has been conducted on differential pressure electrolysis cells and stacks that contribute to energy efficiency, ensuring that more people have access to affordable, reliable, sustainable and advanced energy.

[0003] Japanese Patent Application Laid-Open Publication No. 2019-157213 discloses a differential pressure electrolysis cell, which includes a membrane electrode assembly (membrane electrode assembly), an anode power supply, a cathode power supply, an anode separator, and a cathode separator.

[0004] The membrane electrode assembly has an electrolyte membrane, a cathode electrode catalyst layer laminated on one side of the electrolyte membrane, and an anode electrode catalyst layer laminated on the other side of the electrolyte membrane. In a water electrolysis cell, by applying a voltage between the cathode power supply and the anode power supply, oxygen gas is generated in the anode electrode catalyst layer and hydrogen gas is generated in the anode catalyst layer. In a water electrolysis cell, the hydrogen gas generated in the anode catalyst layer can be made to have a higher pressure than the oxygen gas generated in the cathode catalyst layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-157213 Summary of the Invention [Problem to be solved by the invention]

[0006] There is a need for better differential pressure electrolysis cells and stacks.

[0007] The present disclosure aims to solve the above-mentioned problems. [Means for solving the problem]

[0008] A first aspect of the present disclosure provides a membrane electrode assembly having an electrolyte membrane, a first electrode catalyst layer laminated on one side of the electrolyte membrane, and a second electrode catalyst layer laminated on the other side of the electrolyte membrane, a first separator located on the opposite side of the electrolyte membrane from the second electrode catalyst layer, a second separator located on the opposite side of the electrolyte membrane from the first electrode catalyst layer, a first current feeder disposed between the first separator and the first electrode catalyst layer, a second current feeder disposed between the second separator and the second electrode catalyst layer, and a second current feeder disposed between the second separator and the second separator. a pressing portion sandwiched between the first power feeder and the second power feeder and configured to press the second power feeder toward the second electrode catalyst layer, and capable of generating gas in the second electrode catalyst layer and raising the pressure of the gas to a level higher than that of the fluid by applying a voltage between the first power feeder and the second power feeder to electrolyze a fluid supplied to the membrane electrode structure, wherein the pressing portion includes a sheet portion formed from an electrically insulating polymer material so as to be elastically deformable, and arranged between the second power feeder and the second separator in a state of being compressed and deformed in the stacking direction of the membrane electrode structure.

[0009] A second aspect of the present disclosure is a differential pressure electrolysis stack formed by stacking a plurality of differential pressure electrolysis cells, wherein the differential pressure electrolysis cells are the differential pressure electrolysis cells according to the first aspect. [Effects of the Invention]

[0010] According to the present disclosure, better differential pressure electrolysis cells and differential pressure electrolysis stacks can be provided. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view of an electrolysis device equipped with a differential pressure electrolysis stack. [Figure 2] FIG. 2 is a cross-sectional view of a differential pressure electrolysis cell. [Figure 3] FIG. 3 is a cross-sectional view of a differential pressure electrolytic cell according to a first modified example. [Figure 4] FIG. 4 is a cross-sectional view of a differential pressure electrolytic cell according to a second modified example. [Figure 5] FIG. 5 is a cross-sectional view of a differential pressure electrolytic cell according to a third modified example. [Figure 6] Fig. 6A is a cross-sectional view of the differential pressure electrolytic cell of Fig. 2. Fig. 6B is a cross-sectional view of the differential pressure electrolytic cell of Fig. 5. DETAILED DESCRIPTION OF THE INVENTION

[0012] In the water electrolysis cell described above, for example, a metal leaf spring (pressing portion) is disposed between the anode separator and the anode power supply. The leaf spring presses the anode power supply toward the membrane electrode assembly. In such a configuration, the pressure (electrolyte membrane surface pressure) acting from the leaf spring on the electrolyte membrane is prone to variation. Furthermore, power loss occurs due to excess current flowing through the metal leaf spring. When power loss occurs along with variation in the electrolyte membrane surface pressure, the electrolysis efficiency of the membrane electrode assembly decreases.

[0013] Furthermore, because the anode separator is made of metal, the portion of its surface that comes into contact with the leaf spring is coated with an electrically insulating material. This coating prevents metal ions (e.g., iron ions) from eluting from the anode separator. Because the leaf spring makes line contact with the anode separator coating, a relatively large load acts on the coating. This can cause the anode separator coating to peel off as the leaf spring repeatedly presses against it.

[0014] If the coating on the anode separator peels off, metal ions may leach out. If the leached metal ions reach the electrolyte membrane, the electrolyte membrane will deteriorate. This will reduce the durability of the differential pressure electrolytic cell. Furthermore, when voltage is applied between the cathode current feeder and the anode current feeder, current may flow locally between the leaf spring and the anode separator through the peeled coating, which may cause metal corrosion. This will reduce the durability of the differential pressure electrolytic cell.

[0015] The present disclosure can provide a differential pressure electrolysis cell and a differential pressure electrolysis stack that can improve electrolysis efficiency and durability.

[0016] Fig. 1 is a perspective explanatory diagram of an electrolysis device 11 including a differential pressure electrolysis stack 10. As shown in Fig. 1, the electrolysis device 11 includes a differential pressure electrolysis stack 10 and a power supply 12. The differential pressure electrolysis stack 10 includes a cell stack 14, a pair of terminal plates 16a, 16b, a pair of insulating plates 18a, 18b, and a pair of end plates 20a, 20b.

[0017] The cell stack 14 is formed by stacking a plurality of differential pressure electrolytic cells 22 on top of each other in the direction A. The plurality of differential pressure electrolytic cells 22 are stacked, for example, vertically. The plurality of differential pressure electrolytic cells 22 may also be stacked in a direction intersecting the vertical direction (for example, horizontally). The cell stack 14 is provided with a fluid inlet 24 and a fluid outlet 26. The fluid inlet 24 introduces a fluid used for electrolysis into the cell stack 14. The fluid outlet 26 discharges unreacted fluids that did not react in the electrolysis to the outside of the cell stack 14.

[0018] The terminal plate 16a is disposed at one end (end in the A1 direction) of the cell stack 14. The insulating plate 18a is adjacent to the terminal plate 16a in the A1 direction. The end plate 20a is adjacent to the insulating plate 18a in the A1 direction. The terminal plate 16b is disposed at the other end (end in the A2 direction) of the cell stack 14. The insulating plate 18b is adjacent to the terminal plate 16b in the A2 direction. The end plate 20b is adjacent to the insulating plate 18b in the A2 direction.

[0019] Terminal plate 16a is provided with a terminal portion 28a. Terminal portion 28a is electrically connected to power source 12 via wiring 30a. Terminal plate 16b is provided with a terminal portion 28b. Terminal portion 28b is electrically connected to power source 12 via wiring 30b.

[0020] The pair of end plates 20a, 20b are connected by a plurality of connecting members 32. The connecting members 32 include a stud bolt 34 and a nut 36. One end of the stud bolt 34 is fastened to the end plate 20a. The stud bolt 34 is passed through a hole (not shown) formed in the end plate 20b. A nut 36 is fastened to the other end of the stud bolt 34. As a result, the plurality of connecting members 32 tighten the pair of end plates 20a, 20b in a direction that brings them closer to each other, and a tightening load is applied to the cell stack 14.

[0021] 2 is a cross-sectional view of the differential pressure electrolytic cell 22. As shown in FIG. 2, a fluid supply passage 40, a fluid discharge passage 42, and a gas outlet passage 44 are formed through the differential pressure electrolytic cell 22 in the direction A. The fluid supply passage 40 is formed on the outer periphery (the radially outer end) of the differential pressure electrolytic cell 22. The fluid supply passages 40 of the multiple differential pressure electrolytic cells 22 are in communication with each other. The fluid supply passage 40 is in communication with the fluid inlet 24 (see FIG. 1). The fluid supply passage 40 is a flow path for supplying the fluid introduced through the fluid inlet 24 to the first electrode catalyst layer 76 of the differential pressure electrolytic cell 22.

[0022] The fluid discharge communication hole 42 is formed on the outer periphery (the radially outer end) of the differential pressure electrolytic cell 22. The fluid discharge communication holes 42 of the multiple differential pressure electrolytic cells 22 are in communication with one another. The fluid discharge communication hole 42 is in communication with the fluid outlet 26 (see FIG. 1 ). The fluid discharge communication hole 42 is a flow path for guiding unreacted fluids that did not react during electrolysis in each differential pressure electrolytic cell 22 to the fluid outlet 26.

[0023] The gas outlet manifold 44 is formed in the center of the differential pressure electrolytic cell 22. The fluid supply manifold 40 and the fluid discharge manifold 42 are positioned on either side of the gas outlet manifold 44. The gas outlet manifolds 44 of the multiple differential pressure electrolytic cells 22 communicate with each other. A gas outlet manifold 44 is also formed in the end plate 20b (see FIG. 1). Gas generated in the second electrode catalyst layer 78 of the differential pressure electrolytic cell 22 is discharged to the outside through the gas outlet manifold 44 of the differential pressure electrolytic cell 22 and the gas outlet manifold 44 of the end plate 20b.

[0024] The differential pressure electrolytic cell 22 includes a cell body 46, a pair of separators 48, and a frame member 50. The cell body 46 is sandwiched between the pair of separators 48. The frame member 50 is formed in an annular shape so as to surround the cell body 46. The frame member 50 is formed, for example, from an electrically insulating resin material. Seal members 52 are provided between each of the pair of separators 48 and the frame member 50 to prevent fluid from leaking to the outside.

[0025] The separator 48 is made of a metal material such as stainless steel. Hereinafter, in the differential pressure electrolytic cell 22 of Fig. 2, the separator 48 of the pair of separators 48 that is located in the A1 direction of the cell body 46 will be referred to as the "first separator 48a," and the separator 48 of the pair of separators 48 that is located in the A2 direction of the cell body 46 will be referred to as the "second separator 48b."

[0026] The cell body 46 has a membrane electrode assembly 54, a first current supply body 56, a protective sheet 58, a flow path member 60, a second current supply body 62, a conductive sheet 64, a pressing portion 66, a conductive member 68, a sealing member 70, and a pressure-resistant member 72.

[0027] The membrane electrode assembly 54 is disposed between the first power feeder 56 and the second power feeder 62. A gas outlet passage 44 is formed in the center of the membrane electrode assembly 54. The membrane electrode assembly 54 includes an electrolyte membrane 74, a first electrode catalyst layer 76, and a second electrode catalyst layer 78. The electrolyte membrane 74 is a membrane capable of exchanging ions. The electrolyte membrane 74 is, for example, a proton exchange membrane (PEM). The proton exchange membrane is, for example, a fluorine-based polymer membrane. The electrolyte membrane 74 may also be an anion exchange membrane (AEM).

[0028] The first electrode catalyst layer 76 is laminated on one surface (surface facing the A1 direction) of the electrolyte membrane 74. The first electrode catalyst layer 76 is formed in an annular (ring) shape. A fluid used for electrolysis is supplied to the first electrode catalyst layer 76. The outer diameter of the first electrode catalyst layer 76 is smaller than the outer diameter of the electrolyte membrane 74. The second electrode catalyst layer 78 is laminated on the other surface (surface facing the A2 direction) of the electrolyte membrane 74. Gas is produced in the second electrode catalyst layer 78 by electrolysis of the fluid. The second electrode catalyst layer 78 is formed in an annular shape. The outer diameter of the second electrode catalyst layer 78 is smaller than the outer diameter of the electrolyte membrane 74.

[0029] The first current feeder 56 is formed in an annular (circular ring) shape. The first current feeder 56 also serves as a diffusion layer for supplying the fluid used in electrolysis to the first electrode catalyst layer 76. The first current feeder 56 has a portion formed of a porous material. The protective sheet 58 is disposed between the first electrode catalyst layer 76 and the first current feeder 56. The protective sheet 58 prevents the membrane electrode structure 54 from being damaged by being pressed against the first current feeder 56 by gas generated in the second electrode catalyst layer 78. The protective sheet 58 has a plurality of through holes 80 formed therein to allow the fluid used in electrolysis to pass through.

[0030] The flow path member 60 is formed in an annular shape. The flow path member 60 is disposed between the first separator 48a and the first power feeder 56. The flow path member 60 supports the first power feeder 56. A communication passage 82 is formed in the flow path member 60. The communication passage 82 guides the fluid introduced from the fluid supply passage 40 to the first power feeder 56. The communication passage 82 also guides unreacted fluid that did not react during electrolysis to the fluid discharge passage 42.

[0031] The second current feeder 62 is formed in an annular (circular ring) shape. The second current feeder 62 also serves as a gas diffusion layer for discharging gas generated in the second electrode catalyst layer 78. The second current feeder 62 has a portion formed of a porous material. The outer diameter of the second current feeder 62 is smaller than the outer diameter of the membrane electrode assembly 54. In other words, the outer diameter of the second current feeder 62 is smaller than the outer diameter of the electrolyte membrane 74. The membrane electrode assembly 54 has an outer peripheral portion 84 that protrudes outward in the planar direction beyond the second current feeder 62.

[0032] The conductive sheet 64 is laminated on the surface of the second power feeder 62 facing the A2 direction. The conductive sheet 64 is made of a metal sheet such as titanium or stainless steel. A gas leading hole 44 is formed in the center of the conductive sheet 64. The outer diameter of the conductive sheet 64 is approximately the same as the outer diameter of the second power feeder 62.

[0033] The pressing portion 66 is sandwiched between the second separator 48b and the second power supply body 62. In other words, the pressing portion 66 is sandwiched between the second separator 48b and the conductive sheet 64. The pressing portion 66 presses the conductive sheet 64 and the second power supply body 62 toward the second electrode catalyst layer 78. In other words, the pressing portion 66 presses the conductive sheet 64 toward the second power supply body 62. The pressing portion 66 is formed in an annular (e.g., circular) shape, and is provided at a position corresponding to the electrolyte membrane 74 and the second power supply body 62.

[0034] The pressing portion 66 includes a sheet portion 86 and a metal plate 88. The sheet portion 86 is formed of an electrically insulating polymeric material so as to be elastically deformable. In other words, the sheet portion 86 is formed of a rubber material. The sheet portion 86 is disposed between the second current feeder 62 (conductive sheet 64) and the second separator 48b in a state in which it is compressed and deformed in the stacking direction (direction A) of the membrane electrode assembly 54. The sheet portion 86 is in surface contact with the second separator 48b and the conductive sheet 64. The sheet portion 86 is formed in an annular (e.g., circular) shape. The outer diameter of the sheet portion 86 is approximately the same as the outer diameter of the second current feeder 62.

[0035] The metal plate 88 extends along the sheet portion 86. The metal plate 88 is made of, for example, stainless steel or the like. The metal plate 88 is formed in an annular (for example, circular) shape. The metal plate 88 is provided inside the sheet portion 86. In other words, the metal plate 88 is embedded in the sheet portion 86. The metal plate 88 is located in the center of the sheet portion 86 in the A direction. In other words, the sheet portion 86 covers the metal plate 88 from both sides in the stacking direction of the membrane electrode assembly 54. The sheet portion 86 covers the entire surface of the metal plate 88.

[0036] The conductive member 68 is disposed in the central hole 90 of the pressing portion 66. The conductive member 68 is in contact with the inner surface of the sealing member 70. The conductive member 68 electrically connects the second separator 48b and the conductive sheet 64. The conductive member 68 is made of, for example, a metal material. The conductive member 68 may also be made of carbon or the like. The conductive member 68 is sandwiched between the second separator 48b and the conductive sheet 64. The gas leading hole 44 is formed in the center of the conductive member 68. The conductive member 68 and the conductive sheet 64 are formed with a gas flow path 92 for guiding gas generated in the second electrode catalyst layer 78 to the gas leading hole 44.

[0037] The seal member 70 is formed in an annular shape. The seal member 70 has a circular cross section. The seal member 70 seals the gap between the outer periphery 84 of the membrane electrode assembly 54 and the second separator 48b. That is, the seal member 70 is in airtight and liquidtight contact with the outer periphery 84 of the membrane electrode assembly 54 and is in airtight and liquidtight contact with the second separator 48b. The inner surface of the seal member 70 facing radially inward is in contact with the outer periphery end of the sheet portion 86. The seal member 70 prevents gas generated in the second electrode catalyst layer 78 from leaking to the outside. The second power supply body 62, the conductive sheet 64, and the pressing portion 66 are arranged inside the seal member 70. The gas generated in the second electrode catalyst layer 78 is sealed inside the seal member 70 (gas storage chamber 94).

[0038] In this embodiment, the space between the seal member 70 and the conductive member 68 is blocked by the pressing portion 66 (seat portion 86), so the volume of the gas containing chamber 94 can be made smaller than when a leaf spring is used for the pressing portion 66. The seal member 70 is made of a resin material such as rubber.

[0039] The pressure-resistant member 72 is formed in an annular shape. The pressure-resistant member 72 is made of, for example, a metal material. The pressure-resistant member 72 is disposed so as to surround the sealing member 70 from the radially outer side. The pressure-resistant member 72 is sandwiched between the outer peripheral portion 84 of the membrane electrode assembly 54 and the second separator 48b. The pressure-resistant member 72 contacts the radially outer end of the sealing member 70. The pressure-resistant member 72 prevents the sealing member 70 from expanding radially outward due to the gas (high-pressure gas) present in the gas storage chamber 94. Portions of the second separator 48b facing the pressing portion 66, the sealing member 70, and the pressure-resistant member 72 are coated with an electrically insulating material. This coating prevents metal ions (e.g., iron ions) from eluting from the second separator 48b.

[0040] Next, a brief description will be given of the basic operation of the differential pressure electrolytic stack 10 according to this embodiment. In this embodiment, as shown in Figures 1 and 2, a humidified fluid is supplied to the fluid inlet 24 of the differential pressure electrolytic stack 10, and a voltage is applied between the first power feeder 56 and the second power feeder 62 by the power supply 12. At this time, because the sheet member 86 is electrically insulating, no current flows through the pressing member 66. In other words, when current flows through the second power feeder 62, the conductive sheet 64, the conductive member 68, and the second separator 48b, no unnecessary current flows through the pressing member 66.

[0041] The fluid supplied to the fluid inlet 24 is guided to the first electrode catalyst layer 76 of each differential pressure electrolytic cell 22 via the fluid supply passage 40. In each differential pressure electrolytic cell 22, the fluid is electrolyzed, generating gas in the second electrode catalyst layer 78 (gas storage chamber 94). The gas generated in the second electrode catalyst layer 78 is guided to the gas outlet passage 44 via the gas flow path 92. The gas guided to the gas outlet passage 44 is discharged to an external flow path (not shown). A back pressure valve (not shown) is provided in the external flow path. The gas generated in the second electrode catalyst layer 78 is pressurized by being sealed by the back pressure valve. This allows the gas generated in the second electrode catalyst layer 78 to be pressurized higher than the fluid supplied to the first electrode catalyst layer 76. In this embodiment, the volume of the gas storage chamber 94 is smaller than when a leaf spring is used as the pressing portion 66, thereby increasing the gas pressure. In each differential pressure electrolytic cell 22, unreacted fluids that have not undergone electrolysis are guided to the fluid outlet 26 via the fluid discharge passage 42.

[0042] In this embodiment, the differential pressure electrolytic cell 22 may be a differential pressure water electrolysis cell or an electrochemical hydrogen boost cell. Below, an example where the differential pressure electrolytic cell 22 is a differential pressure water electrolysis cell and an example where the differential pressure electrolytic cell 22 is an electrochemical hydrogen boost cell will be described.

[0043] When the differential pressure electrolysis cell 22 is a differential pressure water electrolysis cell, for example, the electrolyte membrane 74 may be a proton exchange membrane, the first electrode catalyst layer 76 may be an anode electrode catalyst layer, and the second electrode catalyst layer 78 may be a cathode electrode catalyst layer. In this case, when water is supplied to the first electrode catalyst layer 76, the water is electrolyzed in the first electrode catalyst layer 76 to produce hydrogen ions and oxygen gas. The hydrogen ions, along with moisture, migrate through the electrolyte membrane 74 from the first electrode catalyst layer 76 to the second electrode catalyst layer 78. As a result, the hydrogen ions are supplied to the second electrode catalyst layer 78 and the electrolyte membrane 74 is humidified. In the second electrode catalyst layer 78, the hydrogen ions combine to produce hydrogen gas. The hydrogen gas produced in the second electrode catalyst layer 78 is guided to the gas outlet passage 44. Unreacted water supplied to the first electrode catalyst layer 76 and not reacted, and oxygen gas produced in the first electrode catalyst layer 76 are guided to the fluid discharge passage 42.

[0044] Furthermore, when the differential pressure electrolysis cell 22 is a differential pressure water electrolysis cell, for example, the electrolyte membrane 74 may be an anion exchange membrane, the first electrode catalyst layer 76 may be an anode electrode catalyst layer, and the second electrode catalyst layer 78 may be a cathode electrode catalyst layer. In this case, water supplied to the first electrode catalyst layer 76 moves from the first electrode catalyst layer 76 to the second electrode catalyst layer 78 within the electrolyte membrane 74. As a result, water is supplied to the second electrode catalyst layer 78 and the electrolyte membrane 74 is humidified. In the second electrode catalyst layer 78, water is electrolyzed to produce hydrogen gas and hydroxide ions. The hydrogen gas produced in the second electrode catalyst layer 78 is introduced into the gas outlet passage 44. The hydroxide ions produced in the second electrode catalyst layer 78 move from the second electrode catalyst layer 78 to the first electrode catalyst layer 76 within the electrolyte membrane 74. In the first electrode catalyst layer 76, oxygen gas and water are produced from the hydroxide ions. The water present in the first electrode catalyst layer 76 and the oxygen gas produced in the first electrode catalyst layer 76 are guided to the fluid discharge passage 42.

[0045] Furthermore, when the differential pressure electrolysis cell 22 is a differential pressure water electrolysis cell, for example, the electrolyte membrane 74 may be a proton exchange membrane, the first electrode catalyst layer 76 may be a cathode electrode catalyst layer, and the second electrode catalyst layer 78 may be an anode electrode catalyst layer. In this case, water supplied to the first electrode catalyst layer 76 moves from the first electrode catalyst layer 76 to the second electrode catalyst layer 78 within the electrolyte membrane 74. As a result, water is supplied to the second electrode catalyst layer 78 and the electrolyte membrane 74 is humidified. In the second electrode catalyst layer 78, water is electrolyzed to produce hydrogen ions and oxygen gas. The oxygen gas produced in the second electrode catalyst layer 78 is led to the gas leading passage 44. The hydrogen ions produced in the second electrode catalyst layer 78 move from the second electrode catalyst layer 78 to the first electrode catalyst layer 76 within the electrolyte membrane 74. In the first electrode catalyst layer 76, the hydrogen ions combine to produce hydrogen gas. The water and hydrogen gas that have been supplied to the first electrode catalyst layer 76 and have not reacted are guided to the fluid discharge passage 42.

[0046] Furthermore, when the differential pressure electrolysis cell 22 is a differential pressure water electrolysis cell, for example, the electrolyte membrane 74 may be an anion exchange membrane, the first electrode catalyst layer 76 may be a cathode electrode catalyst layer, and the second electrode catalyst layer 78 may be an anode electrode catalyst layer. In this case, when water is supplied to the first electrode catalyst layer 76, the water is electrolyzed in the first electrode catalyst layer 76 to produce hydrogen gas and hydroxide ions. The hydroxide ions migrate together with moisture through the electrolyte membrane 74 from the first electrode catalyst layer 76 to the second electrode catalyst layer 78. As a result, the hydroxide ions are supplied to the second electrode catalyst layer 78 and the electrolyte membrane 74 is humidified. In the second electrode catalyst layer 78, oxygen gas and water are produced from the hydroxide ions. The oxygen gas produced in the second electrode catalyst layer 78 is guided to the gas outlet passage 44. Unreacted water supplied to the first electrode catalyst layer 76 and not reacted, and hydrogen gas produced in the first electrode catalyst layer 76 are guided to the fluid discharge passage 42.

[0047] When the differential pressure electrolysis cell 22 is an electrochemical hydrogen boost cell, for example, the electrolyte membrane 74 may be a proton exchange membrane, the first electrode catalyst layer 76 may be an anode electrode catalyst layer, and the second electrode catalyst layer 78 may be a cathode electrode catalyst layer. In this case, when hydrogen gas containing moisture is supplied to the first electrode catalyst layer 76, the hydrogen gas is electrolyzed in the first electrode catalyst layer 76 to generate hydrogen ions. The hydrogen ions, along with the moisture, migrate through the electrolyte membrane 74 from the first electrode catalyst layer 76 to the second electrode catalyst layer 78. As a result, the hydrogen ions are supplied to the second electrode catalyst layer 78 and the electrolyte membrane 74 is humidified. In the second electrode catalyst layer 78, the hydrogen ions combine to generate hydrogen gas. The hydrogen gas generated in the second electrode catalyst layer 78 is guided to the gas outlet manifold 44. Unreacted hydrogen gas that is guided to the first electrode catalyst layer 76 is guided to the fluid discharge manifold 42.

[0048] According to this embodiment, the sheet portion 86 is made of an electrically insulating polymeric material and is elastically deformable, which reduces variations in the surface pressure on the electrolyte membrane 74 compared to when a leaf spring is used as the pressing portion 66. Furthermore, it is possible to avoid power loss due to excess current flowing through the sheet portion 86. This improves the electrolysis efficiency of the differential pressure electrolytic cell 22.

[0049] Furthermore, such a sheet portion 86 is in surface contact with the second separator 48b. That is, compared to when a leaf spring is used as the pressing portion 66, the pressure acting on the coating of the second separator 48b can be reduced. This prevents the pressing portion 66 from peeling off the coating. This prevents the generation of metal ions due to coating peeling, thereby preventing deterioration of the electrolyte membrane 74 due to metal ions. Furthermore, this prevents metal corrosion due to localized current flow. This improves the durability of the differential pressure electrolytic cell 22. This makes it possible to provide a better differential pressure electrolytic cell 22 and differential pressure electrolytic stack 10.

[0050] In the present embodiment, the pressing portion 66 has a metal plate 88 extending along the sheet portion 86. With this configuration, the amount of elastic deformation of the sheet portion 86 in the A direction can be reduced compared to when the sheet portion 86 does not have the metal plate 88 (a pressing portion 66a according to a first modified example, which will be described later). In other words, the amount of compressive deformation of the sheet portion 86 in the A direction when the electrolyte membrane 74 expands due to water absorption can be reduced. This makes it possible to suppress the expansion of the electrolyte membrane 74 due to water absorption. In other words, it is possible to suppress the electrolyte membrane 74 from spreading outward in the planar direction. In other words, it is possible to suppress the formation of blisters on the electrolyte membrane 74.

[0051] (First Modification) Next, a differential pressure electrolytic cell 22a according to a first modified example will be described. Fig. 3 is a cross-sectional view of the differential pressure electrolytic cell 22a according to the first modified example. Among the components of the differential pressure electrolytic cell 22a according to the first modified example, the same components as those of the differential pressure electrolytic cell 22 described above are designated by the same reference numerals, and detailed description thereof will be omitted. The same applies to a differential pressure electrolytic cell 22b according to a second modified example and a differential pressure electrolytic cell 22c according to a third modified example, which will be described later.

[0052] 3, in the differential pressure electrolytic cell 22a according to the first modified example, a pressing portion 66a is provided instead of the pressing portion 66 of the above-described differential pressure electrolytic cell 22. The pressing portion 66a is composed only of a sheet portion 86. In other words, the pressing portion 66a does not include the above-described metal plate 88.

[0053] This configuration provides a differential pressure electrolytic cell 22a that can improve electrolysis efficiency and durability. Furthermore, since there is no need to provide a metal plate 88 inside the seat portion 86, the configuration of the pressing portion 66a can be simplified.

[0054] (Second Modification) Next, a differential pressure electrolytic cell 22b according to a second modified example will be described. Fig. 4 is a cross-sectional view of the differential pressure electrolytic cell 22b according to the second modified example. As shown in Fig. 4, the differential pressure electrolytic cell 22b according to the second modified example is provided with a pressing unit 66b instead of the pressing unit 66 of the differential pressure electrolytic cell 22 described above.

[0055] The pressing portion 66b has a sheet portion 86a and a metal plate 88. The sheet portion 86a includes a first sheet element 100 and a second sheet element 102. The first sheet element 100 is sandwiched between the metal plate 88 and the conductive sheet 64. The second sheet element 102 is sandwiched between the metal plate 88 and the second separator 48b. The outer end surface of the metal plate 88 in the planar direction is not covered by the sheet portion 86a. The inner end surface of the metal plate 88 in the planar direction is not covered by the sheet portion 86a.

[0056] This configuration provides a differential pressure electrolytic cell 22b that can improve electrolysis efficiency and durability. Furthermore, since the pressing portion 66b has the metal plate 88, blisters on the electrolyte membrane 74 can be suppressed.

[0057] In the differential pressure electrolytic cell 22b according to the second modification, the inner peripheral end of the first sheet 100 and the inner peripheral end of the second sheet 102 may be connected to each other. In this case, the inner end face of the metal plate 88 in the planar direction is covered by the sheet portion 86a. This prevents electrical conduction between the conductive member 68 and the metal plate 88.

[0058] (Third Modification) Next, a differential pressure electrolytic cell 22c according to a third modified example will be described. Fig. 5 is a cross-sectional view of the differential pressure electrolytic cell 22c according to the third modified example. As shown in Fig. 5, the differential pressure electrolytic cell 22c according to the third modified example is provided with a pressing portion 66c instead of the pressing portion 66 of the differential pressure electrolytic cell 22 described above, and the sealing member 70 described above is omitted.

[0059] The pressing portion 66c has a sheet portion 86, a metal plate 88, a seal portion 104, and a reinforcing portion 106. The seal portion 104 is made of the same material as the sheet portion 86. That is, the seal portion 104 is made of an electrically insulating polymer material so as to be elastically deformable. In other words, the seal portion 104 is made of a rubber material.

[0060] The seal portion 104 extends in an annular (circular ring) shape. The seal portion 104 seals the gap between the second separator 48b and the outer peripheral portion 84 of the membrane electrode assembly 54, which protrudes outward in the planar direction beyond the second power supply body 62. The seal portion 104 is molded integrally with the sheet portion 86. In other words, the seal portion 104 is connected to the outer peripheral end of the sheet portion 86.

[0061] The seal portion 104 is adjacent to the second power feeder 62 on the outer side in the planar direction (outer side in the radial direction). That is, the seal portion 104 is in contact with or close to the second power feeder 62. The seal portion 104 presses a portion (adjacent portion 110) of the electrolyte membrane 74 that is adjacent to the outer side in the planar direction relative to a portion (pressed portion 108) of the electrolyte membrane 74 that is pressed by the second power feeder 62 in the A1 direction (see FIG. 6B). The pressure-resistant member 72 contacts the outer end of the seal portion 104 in the radial direction.

[0062] The reinforcing portion 106 is provided inside the seal portion 104. The reinforcing portion 106 is made of metal. The reinforcing portion 106 extends in an annular shape along the seal portion 104. The reinforcing portion 106 is connected to the outer periphery of the metal plate 88. That is, the reinforcing portion 106 and the metal plate 88 are integrally molded. The reinforcing portion 106 has an L-shaped cross section. The reinforcing portion 106 includes an annular extending portion 106a extending radially outward from the metal plate 88, and an annular protruding portion 106b protruding in the A1 direction from the extending portion 106a.

[0063] 6A is a cross-sectional view of the differential pressure electrolytic cell 22 shown in FIG. 2. As shown in FIG. 6A, in the differential pressure electrolytic cell 22, the sealing member 70 has a circular cross section. Therefore, the portion of the membrane electrode assembly 54 that is pressed by the sealing member 70 (sealed portion 112) is located farther outward in the planar direction than the pressed portion 108 of the membrane electrode assembly 54. In this case, the adjacent portion 110 of the electrolyte membrane 74 is not pressed by the sealing member 70. If the pressed portion 108 is pressed in the A1 direction by the second current feeder 62 in this state, the adjacent portion 110 may be deformed in the A2 direction, bulging toward the gap between the second current feeder 62 and the sealing member 70.

[0064] 6B is a cross-sectional view of the differential pressure electrolytic cell 22c shown in FIG. 5. As shown in FIG. 6B, in the differential pressure electrolytic cell 22c according to the third modification, the seal portion 104 is integrally formed with the sheet portion 86, allowing the seal portion 104 to press against the adjacent portion 110. That is, in the differential pressure electrolytic cell 22c, the seal portion 112 is adjacent to the pressing portion 108. As a result, the seal portion 104 prevents a gap from forming between the second power feed element 62 and the pressure-resistant member 72, thereby suppressing deformation of the adjacent portion 110.

[0065] Furthermore, in the differential pressure electrolytic cell 22c of the third modification, the seal portion 104 is molded integrally with the seat portion 86, allowing the outer diameter of the seal portion 104 to be smaller than in the case where the seal member 70 is provided separately from the seat portion 86 as in the above-described differential pressure electrolytic cell 22. This allows the outer diameter of the differential pressure electrolytic cell 22c to be smaller.

[0066] In the differential pressure electrolytic cell 22c, a metal reinforcing portion 106 is provided inside the seal portion 104. With this configuration, the seal portion 104 can effectively hold down the adjacent portion 110.

[0067] Furthermore, the reinforcing portion 106 extends in an annular shape along the sealing portion 104. With this configuration, the sealing portion 104 can effectively hold down the adjacent portion 110.

[0068] Furthermore, the reinforcing portion 106 is connected to the metal plate 88. With this configuration, the rigidity of the reinforcing portion 106 can be increased.

[0069] In the differential pressure electrolytic cell 22c, the seal portion 104 is in contact with or in close proximity to the second power supply element 62. This configuration allows the volume of the gas storage chamber 94 to be reduced, thereby increasing the rate at which the pressure of the gas generated in the second electrode catalyst layer 78 increases.

[0070] The differential pressure electrolytic cell 22c according to the third modified example is not limited to the above-described configuration. The reinforcing portion 106 may be separated from the metal plate 88.

[0071] The following additional notes are further disclosed regarding the above embodiment.

[0072] (Appendix 1) The differential pressure electrolytic cell of the present disclosure includes a membrane electrode assembly (54) having an electrolyte membrane (74), a first electrode catalyst layer (76) laminated on one side of the electrolyte membrane, and a second electrode catalyst layer (78) laminated on the other side of the electrolyte membrane, a first separator (48a) located on the opposite side of the electrolyte membrane from the second electrode catalyst layer, a second separator (48b) located on the opposite side of the electrolyte membrane from the first electrode catalyst layer, a first current feeder (56) arranged between the first separator and the first electrode catalyst layer, a second current feeder (62) arranged between the second separator and the second electrode catalyst layer, and a second current feeder (62) arranged between the second separator and the second separator. a pressing portion (66, 66a-66c) sandwiched between the first power supply and the second power supply for pressing the second power supply toward the second electrode catalyst layer, and capable of generating gas in the second electrode catalyst layer and raising the pressure of the gas to a level higher than that of the fluid by applying a voltage between the first power supply and the second power supply to electrolyze a fluid supplied to the membrane electrode structure, wherein the pressing portion includes a sheet portion (86, 86a) formed elastically deformable from an electrically insulating polymer material and arranged between the second power supply and the second separator in a state of being compressed and deformed in the stacking direction of the membrane electrode structure.

[0073] According to this configuration, the sheet portion is made of an electrically insulating polymer material and is elastically deformable, which reduces variations in the surface pressure of the electrolyte compared to when a leaf spring is used as the pressing portion. Furthermore, power loss due to excess current flowing through the sheet portion can be avoided. Therefore, the electrolysis efficiency of the differential pressure electrolysis cell can be improved.

[0074] Furthermore, such a sheet portion is in surface contact with the second separator. That is, the pressure acting on the coating of the second separator can be reduced compared to when a leaf spring is used as the pressing portion. This prevents the coating from peeling off due to the pressing portion. This prevents the generation of metal ions due to coating peeling, thereby preventing deterioration of the electrolyte membrane due to metal ions. Furthermore, metal corrosion due to localized current flow can be suppressed. This improves the durability of the differential pressure electrolytic cell. Therefore, a better differential pressure electrolytic cell and differential pressure electrolytic stack can be provided.

[0075] (Appendix 2) In the differential pressure electrolytic cell described in Supplementary Note 1, the pressing portion may have a metal plate (88) provided inside the seat portion.

[0076] With this configuration, the amount of elastic deformation of the sheet portion in the stacking direction of the membrane electrode assembly can be reduced compared to when a metal plate is not provided on the sheet portion. In other words, the amount of compressive deformation of the sheet portion in the stacking direction when the electrolyte membrane expands due to water absorption can be reduced. This makes it possible to suppress expansion of the electrolyte membrane due to water absorption. In other words, it is possible to suppress outward expansion of the electrolyte membrane in the planar direction. In other words, it is possible to suppress blisters (water blisters) on the electrolyte membrane. Furthermore, since the outer diameter of the sealing portion can be made smaller compared to when a sealing member is provided separately from the pressing portion, the outer diameter of the differential pressure electrolytic cell can be made smaller.

[0077] (Appendix 3) In the differential pressure electrolytic cell described in Appendix 1, the pressing portion may have a metal plate extending along a surface direction of the membrane electrode assembly, and the sheet portion may cover the metal plate from both sides in the stacking direction.

[0078] This configuration provides the same effects as the differential pressure electrolytic cell described in Supplementary Note 2.

[0079] (Appendix 4) The differential pressure electrolytic cell according to any one of Supplementary Notes 1 to 3, further comprising an annular seal portion (104) formed of an electrically insulating polymeric material so as to be elastically deformable, and which seals between the second separator and an outer peripheral portion (84) of the membrane electrode assembly that protrudes outward in a planar direction beyond the second current feeder, and the seal portion may be molded integrally with the sheet portion.

[0080] With this configuration, the seal portion is integrally molded with the sheet portion, so that the seal portion can press the portion of the membrane electrode assembly adjacent to the portion pressed by the second current feeder (pressed portion) on the outer side in the planar direction (adjacent portion), thereby suppressing deformation of the adjacent portion (deformation in which the adjacent portion bulges toward the second separator).

[0081] (Appendix 5) In the differential pressure electrolytic cell described in Supplementary Note 4, a metallic reinforcing part (106) may be provided inside the sealing part.

[0082] With this configuration, the adjacent area can be more effectively pressed by the sealing portion.

[0083] (Appendix 6) In the differential pressure electrolytic cell described in Supplementary Note 5, the reinforcing portion may extend in an annular shape along the sealing portion.

[0084] With this configuration, the adjacent area can be pressed more effectively by the sealing portion.

[0085] (Appendix 7) In the differential pressure electrolytic cell described in Supplementary Note 5, the pressing portion may have a metal plate provided inside the sealing portion, and the reinforcing portion may be connected to the metal plate.

[0086] With this configuration, the rigidity of the reinforcing portion can be increased.

[0087] (Appendix 8) The differential pressure electrolytic cell according to Supplementary Note 4 may further include an annular pressure-resistant member (72) that covers the seal portion from the outside in the planar direction, and the pressure-resistant member may be in contact with the seal portion.

[0088] According to this configuration, the pressure-resistant member can prevent the seal portion from expanding outward in the planar direction due to gas generated in the second electrode catalyst layer.

[0089] (Appendix 9) In the differential pressure electrolytic cell described in Supplementary Note 4, the seal portion may be in contact with or in close proximity to the second power supply element.

[0090] With this configuration, the volume of the gas storage chamber can be reduced, and the rate at which the pressure of the gas generated in the second electrode catalyst layer increases can be increased.

[0091] (Appendix 10) The differential pressure electrolytic stack of the present disclosure is a differential pressure electrolytic stack (10) formed by stacking a plurality of differential pressure electrolytic cells, and the differential pressure electrolytic cells are the differential pressure electrolytic cells described in any one of Appendices 1 to 9.

[0092] Although the present disclosure has been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the present disclosure or the spirit of the present disclosure derived from the content of the claims and their equivalents. These embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments. [Explanation of symbols]

[0093] 10... Differential pressure electrolysis stack 22, 22a to 22c... Differential pressure electrolysis cells 48a...First separator 48b...Second separator 54...Membrane electrode structure 56...First power feeder 62... Second power supply body 66, 66a to 66c... Pressing portion 72... Pressure-resistant member 74... Electrolyte membrane 76...First electrode catalyst layer 78...Second electrode catalyst layer 84...Outer periphery of membrane electrode assembly 86, 86a...Seat portion 88...metal plate 104...sealing portion 106...Reinforcement

Claims

1. a membrane electrode assembly including an electrolyte membrane, a first electrode catalyst layer laminated on one surface of the electrolyte membrane, and a second electrode catalyst layer laminated on the other surface of the electrolyte membrane; a first separator located on the opposite side of the electrolyte membrane from the second electrode catalyst layer; a second separator located on the opposite side of the electrolyte membrane from the first electrode catalyst layer; a first current feeder disposed between the first separator and the first electrode catalyst layer; a second current feeder disposed between the second separator and the second electrode catalyst layer; a pressing portion sandwiched between the second current feeder and the second separator, for pressing the second current feeder toward the second electrode catalyst layer; Equipped with a differential pressure electrolysis cell that applies a voltage between the first power feeder and the second power feeder to electrolyze a fluid supplied to the membrane electrode assembly, thereby generating a gas in the second electrode catalyst layer and raising the pressure of the gas to a higher pressure than the fluid, a differential pressure electrolytic cell, wherein the pressing portion includes a sheet portion that is formed from an electrically insulating polymeric material so as to be elastically deformable, and that is disposed between the second current feeder and the second separator in a state in which the sheet portion is compressed and deformed in the stacking direction of the membrane electrode assembly.

2. 2. The differential pressure electrolytic cell according to claim 1, A differential pressure electrolytic cell, wherein the pressing portion has a metal plate provided inside the seat portion.

3. 2. The differential pressure electrolytic cell according to claim 1, the pressing portion has a metal plate extending along a surface direction of the membrane electrode assembly, The sheet portion covers the metal plate from both sides in the stacking direction.

4. 2. The differential pressure electrolytic cell according to claim 1, the membrane electrode assembly further includes an annular seal portion that is elastically deformable and made of an electrically insulating polymer material, and that seals between the second separator and an outer peripheral portion of the membrane electrode assembly that protrudes outward in a planar direction beyond the second current feeder; The differential pressure electrolytic cell, wherein the seal portion is molded integrally with the seat portion.

5. 5. The differential pressure electrolytic cell according to claim 4, A differential pressure electrolytic cell, wherein a metal reinforcing part is provided inside the seal part.

6. 6. The differential pressure electrolytic cell according to claim 5, The reinforcing portion extends annularly along the sealing portion.

7. 6. The differential pressure electrolytic cell according to claim 5, the pressing portion has a metal plate provided inside the sealing portion, The reinforcing portion is connected to the metal plate.

8. 5. The differential pressure electrolytic cell according to claim 4, The pressure-resistant member further includes an annular pressure-resistant member that covers the seal portion from the outside in the surface direction. The pressure-resistant member is in contact with the seal portion.

9. 5. The differential pressure electrolytic cell according to claim 4, A differential pressure electrolytic cell, wherein the seal portion is in contact with or in close proximity to the second power supply.

10. A differential pressure electrolysis stack formed by stacking a plurality of differential pressure electrolysis cells, A differential pressure electrolysis stack, wherein the differential pressure electrolysis cell is the differential pressure electrolysis cell according to any one of claims 1 to 9.

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