Differential pressure electrolysis cell, differential pressure electrolysis stack, and method for manufacturing a differential pressure electrolysis cell

Abstract

SOLUTION: A differential pressure electrolysis cell 30 is capable of generating a gas having a higher pressure than a fluid at a second electrode by applying a voltage between a first electrode 48 and a second electrode 50 to electrolyze a fluid containing moisture supplied to the first electrode. An electrolyte membrane 46 has a first layer 82 facing the first electrode and a second layer 84 facing the second electrode. An ion exchange capacity per unit area of the first layer is a first ion exchange capacity, and an ion exchange capacity per unit area of the second layer is a second ion exchange capacity. The second ion exchange capacity is greater than the first ion exchange capacity.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a differential pressure electrolysis cell, a differential pressure electrolysis stack, and a method for manufacturing a differential pressure electrolysis cell. [Background technology]

[0002] In recent years, technological developments have been underway in differential pressure electrolysis stacks that contribute to energy efficiency, ensuring that more people have access to affordable, reliable, sustainable and advanced energy.

[0003] For example, Patent Document 1 discloses a differential pressure water electrolysis stack equipped with a polymer electrolyte membrane having excellent hydrogen barrier properties. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7031719 Summary of the Invention [Problem to be solved by the invention]

[0005] There is a need for better differential pressure electrolysis cells, differential pressure electrolysis stacks, and methods for manufacturing differential pressure electrolysis cells.

[0006] The present disclosure aims to solve the above-mentioned problems. [Means for solving the problem]

[0007] A first aspect of the present disclosure is a differential pressure electrolytic cell comprising a membrane electrode assembly formed by sandwiching an electrolyte membrane between a first electrode and a second electrode, and capable of electrolyzing a water-containing fluid supplied to the first electrode by applying a voltage between the first electrode and the second electrode, thereby causing the second electrode to produce a gas at a pressure higher than that of the fluid, wherein the electrolyte membrane has a first layer facing the first electrode and a second layer facing the second electrode, the first layer having a first ion exchange capacity per unit area, the second layer having a second ion exchange capacity per unit area, and the second ion exchange capacity being greater than the first ion exchange capacity.

[0008] A second aspect of the present disclosure is a differential pressure electrolysis stack including a cell stack in which a plurality of differential pressure electrolysis cells according to the first aspect are stacked.

[0009] A third aspect of the present disclosure is a method for manufacturing a differential pressure electrolytic cell comprising a membrane electrode assembly formed by sandwiching an electrolyte membrane between a first electrode and a second electrode, and capable of electrolyzing a fluid supplied to the first electrode by applying a voltage between the first electrode and the second electrode, thereby causing the second electrode to produce a gas having a higher pressure than the fluid, the method comprising: an electrolyte membrane forming step of forming the electrolyte membrane including a first layer having an ion exchange capacity per unit area of ​​a first ion exchange capacity and a second layer having an ion exchange capacity per unit area of ​​a second ion exchange capacity; and an arrangement step of arranging the electrolyte membrane between the first electrode and the second electrode such that the first layer faces the first electrode and the second layer faces the second electrode. [Effects of the Invention]

[0010] According to the present disclosure, a better differential pressure electrolysis cell, differential pressure electrolysis stack, and method for manufacturing a differential pressure electrolysis cell can be provided. [Brief explanation of the drawings]

[0011] [Figure 1]FIG. 1 is a schematic diagram of an electrolysis device including a differential pressure electrolysis stack according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view of a differential pressure electrolysis cell. [Figure 3] FIG. 3 is a cross-sectional view illustrating the electrolyte membrane. [Figure 4] FIG. 4 is a flowchart showing an example of a method for manufacturing a differential pressure electrolytic cell. [Figure 5] 5A to 5C are cross-sectional explanatory views showing an example of a method for manufacturing a differential pressure electrolytic cell. [Figure 6] FIG. 6 is a flowchart showing an example of the electrolyte membrane forming step. [Figure 7] 7A and 7B are cross-sectional explanatory views showing an example of the electrolyte membrane forming step. DETAILED DESCRIPTION OF THE INVENTION

[0012] The differential pressure electrolytic cell includes a membrane electrode assembly. The membrane electrode assembly is formed by sandwiching an electrolyte membrane between a first electrode and a second electrode. The differential pressure electrolytic cell applies a voltage between the first electrode and the second electrode to electrolyze a water-containing fluid supplied to the first electrode, thereby causing the second electrode to generate a gas at a higher pressure than the fluid supplied to the first electrode. In such a differential pressure electrolytic cell, the electrolyte membrane is humidified by the water-containing fluid supplied to the first electrode.

[0013] Specifically, moisture supplied to the first electrode migrates from the first electrode toward the second electrode within the electrolyte membrane. However, moisture migrating from the first electrode toward the second electrode within the electrolyte membrane is pushed back toward the first electrode by the pressure of the high-pressure gas generated at the second electrode, making the portion of the electrolyte membrane facing the second electrode more likely to dry than the portion facing the first electrode. In other words, the moisture content of the electrolyte membrane is more likely to vary across its thickness. When this drying occurs, the movement of ions within the electrolyte membrane is hindered, which can reduce the efficiency of electrolysis and accelerate deterioration of the electrolyte membrane due to increased electrical resistance. The present disclosure provides a differential pressure electrolytic cell, a differential pressure electrolytic stack, and a method for manufacturing a differential pressure electrolytic cell that can suppress a decrease in electrolysis efficiency and the progression of electrolyte membrane degradation by configuring an electrolyte membrane that suppresses drying of the portion of the electrolyte membrane facing the second electrode.

[0014] Fig. 1 is a schematic diagram of an electrolysis device 12 including a differential pressure electrolysis stack 10 according to an embodiment. As shown in Fig. 1, the electrolysis device 12 includes, for example, the differential pressure electrolysis stack 10, a gas outlet path 13, a back-pressure valve 14, a tank 16, and an electrolysis power supply 18.

[0015] The differential pressure electrolysis stack 10 is a differential pressure electrolysis stack capable of producing high-pressure gas by electrolyzing a fluid. The differential pressure electrolysis stack 10 includes a cell stack 20, a pair of end plates 22, a supply port 24, an outlet 26, and a produced gas outlet 28.

[0016] The cell stack 20 is formed by stacking a plurality of differential pressure electrolytic cells 30 on top of each other in the X direction. The plurality of differential pressure electrolytic cells 30 are stacked, for example, vertically. The plurality of differential pressure electrolytic cells 30 may also be stacked in a direction intersecting the vertical direction (for example, horizontally). A pair of end plates 22 sandwich the plurality of differential pressure electrolytic cells 30 from the X direction. The supply port 24 supplies fluid to the inside of the cell stack 20. The discharge port 26 discharges the discharged fluid to the outside of the cell stack 20. The produced gas discharge port 28 guides gas produced inside the cell stack 20 to the gas outlet path 13. The produced gas discharge port 28 is provided, for example, in the center of the end plate 22.

[0017] The gas outlet path 13 introduces the product gas generated in the cell stack 20 to the tank 16. The gas outlet path 13 is provided with a back pressure valve 14. The back pressure valve 14 opens when the pressure of the gas introduced from the differential pressure electrolysis stack 10 is equal to or higher than a predetermined threshold. The back pressure valve 14 closes when the pressure of the product gas introduced from the differential pressure electrolysis stack 10 is lower than the threshold. The tank 16 is a high-pressure gas tank that can store the gas produced in the differential pressure electrolysis stack 10.

[0018] FIG. 2 is a cross-sectional view of a differential pressure electrolytic cell 30. As shown in FIG. 2, the differential pressure electrolytic cell 30 is provided with a fluid supply passage 32, a fluid discharge passage 34, and a produced gas discharge passage 36 that penetrate the differential pressure electrolytic cell 30 in the X direction. The fluid supply passages 32 of the multiple differential pressure electrolytic cells 30 are connected to one another. The fluid supply passage 32 is connected to the supply port 24 (see FIG. 1). The fluid discharge passages 34 of the multiple differential pressure electrolytic cells 30 are connected to one another. The fluid discharge passage 34 is connected to the discharge port 26 (see FIG. 1). The produced gas discharge passages 36 of the multiple differential pressure electrolytic cells 30 are connected to one another. The produced gas discharge passage 36 is connected to the produced gas discharge port 28 (see FIG. 1).

[0019] The fluid supply passage 32 and the fluid discharge passage 34 are provided at positions spaced apart from each other on the outer periphery of the differential pressure electrolytic cell 30. The produced gas discharge passage 36 is provided in the center of the differential pressure electrolytic cell 30. The produced gas discharge passage 36 is located between the fluid supply passage 32 and the fluid discharge passage 34. The fluid supply passage 32 supplies a fluid to the first electrode 48. The fluid discharge passage 34 guides the fluid (discharge fluid) that has flowed through the first electrode 48. The produced gas discharge passage 36 guides the gas generated at the second electrode 50.

[0020] The differential pressure electrolytic cell 30 has a membrane electrode assembly 38, a pair of separators 40, and a frame member 42. The membrane electrode assembly 38 is sandwiched between the pair of separators 40. The frame member 42 is formed in an annular shape so as to surround the membrane electrode assembly 38. A seal member 44 is provided between the frame member 42 and the separator 40 to prevent the fluid and the discharged fluid from leaking to the outside. Hereinafter, in FIG. 2 , the separator 40 of the pair of separators 40 located in the X1 direction of the membrane electrode assembly 38 may be referred to as the "first separator 40a," and the separator 40 of the pair of separators 40 located in the X2 direction of the membrane electrode assembly 38 may be referred to as the "second separator 40b."

[0021] The membrane electrode assembly 38 is formed in an annular (e.g., circular) shape. The membrane electrode assembly 38 has an electrolyte membrane 46, a first electrode 48, and a second electrode 50. The electrolyte membrane 46 is sandwiched between the first electrode 48 and the second electrode 50. The electrolyte membrane 46 is an ion exchange membrane. Specifically, the electrolyte membrane 46 is, for example, a proton exchange membrane (PEM). The electrolyte membrane 46 may also be an anion exchange membrane (AEM). The electrolyte membrane 46 prevents the gas (produced gas) produced at the second electrode 50 from passing through to the first electrode 48. A specific configuration of the electrolyte membrane 46 will be described later.

[0022] The first electrode 48 has a first catalyst layer 52, a protective sheet 54, and a first current feeder 56. The first catalyst layer 52 is bonded to one surface 46a (the surface facing the X1 direction) of the electrolyte membrane 46. The first current feeder 56 also serves as a fluid diffusion layer for supplying fluid to the first catalyst layer 52. The first current feeder 56 has a portion formed of a porous material. The protective sheet 54 is disposed between the first catalyst layer 52 and the first current feeder 56. The protective sheet 54 prevents the electrolyte membrane 46 from being damaged by being pressed against the first current feeder 56 by the gas produced by the second electrode 50. The protective sheet 54 has a plurality of through-holes 58 formed therein.

[0023] The outer diameter of the second electrode 50 is smaller than the outer diameter of the first electrode 48. The second electrode 50 has a second catalyst layer 60 and a second power supply body 62. The second catalyst layer 60 is joined to the other surface 46b (the surface facing the X2 direction) of the electrolyte membrane 46. The second power supply body 62 also serves as a gas diffusion layer for guiding the product gas generated in the second catalyst layer 60. The second power supply body 62 has a portion formed of a porous material.

[0024] A support member 64 that supports the membrane electrode assembly 38 is provided between the first separator 40a and the first current feeder 56. A communication passage 66 is formed in the support member 64. The communication passage 66 guides the fluid introduced from the fluid supply passage 32 into the first current feeder 56. The communication passage 66 also guides the discharged fluid from the first current feeder 56 to the fluid discharge passage 34.

[0025] A load-applying mechanism 68 is provided between the second separator 40b and the second power feeder 62, biasing the second power feeder 62 in the X1 direction. The load-applying mechanism 68 includes, for example, a leaf spring 70, a leaf spring holder 72, and a conductive sheet 76. An annular member 78 is provided between the second separator 40b and the outer periphery of the electrolyte membrane 46. The annular member 78 is made of pressure-resistant copper. The annular member 78 is in liquid-tight and airtight contact with the other surface 46b of the electrolyte membrane 46. An annular seal member 80 is disposed between the annular member 78 and the load-applying mechanism 68. The seal member 80 is in contact with both the second separator 40b and the electrolyte membrane 46.

[0026] 1, the electrolysis power supply 18 is a DC power supply, and applies a voltage between the first power supply 56 and the second power supply 62 shown in FIG.

[0027] FIG. 3 is a cross-sectional view illustrating the electrolyte membrane 46. As shown in FIG. 3, the electrolyte membrane 46 has a laminated structure formed by stacking, for example, three layers. Specifically, the electrolyte membrane 46 has a first layer 82, a second layer 84, and an intermediate layer 86. The first layer 82 faces the first electrode 48. The second layer 84 faces the second electrode 50. The intermediate layer 86 is located between the first layer 82 and the second layer 84.

[0028] The first layer 82 is made of a first ionomer material having a first ion exchange capacity per unit area, the second layer 84 is made of a second ionomer material having a second ion exchange capacity per unit area, and the intermediate layer 86 is made of a third ionomer material having a third ion exchange capacity per unit area.

[0029] The second ion exchange capacity is greater than the first ion exchange capacity. That is, the maximum water content per unit area of ​​the second layer 84 is greater than the maximum water content per unit area of ​​the first layer 82. The third ion exchange capacity is greater than the first ion exchange capacity but less than the second ion exchange capacity. That is, the maximum water content per unit area of ​​the intermediate layer 86 is greater than the maximum water content per unit area of ​​the first layer 82 but less than the maximum water content per unit area of ​​the second layer 84.

[0030] The first layer 82, the second layer 84, and the intermediate layer 86 have the same thickness. The first layer 82, the second layer 84, and the intermediate layer 86 may have different thicknesses. In the present embodiment, the intermediate layer 86 may be omitted. In this case, the electrolyte membrane 46 is formed by only two layers (the first layer 82 and the second layer 84). The electrolyte membrane 46 may also be formed by stacking, for example, four or more layers. In other words, the electrolyte membrane 46 may have a plurality of intermediate layers 86. In this case, the ion exchange capacities per unit area of ​​the plurality of intermediate layers 86 may be the same or different from one another. When the ion exchange capacities per unit area of ​​the plurality of intermediate layers 86 are different from one another, it is preferable to arrange the plurality of intermediate layers 86 so that the ion exchange capacity per unit area increases in the X1 direction.

[0031] The electrolysis device 12 may include components in addition to those described above.

[0032] Next, a method for manufacturing the differential pressure electrolytic cell 30 will be described. Fig. 4 is a flowchart showing an example of a method for manufacturing the differential pressure electrolytic cell 30. Figs. 5A to 5C are cross-sectional explanatory views showing an example of a method for manufacturing the differential pressure electrolytic cell 30. As shown in Fig. 4, in step S1, an electrolyte membrane formation step is performed. That is, in the electrolyte membrane formation step, an electrolyte membrane 46 is formed.

[0033] Specifically, as shown in Fig. 5A, for example, a first ionomer material having a first ion exchange capacity per unit area is applied to a substrate 200 for film formation to form a first layer 82. Subsequently, as shown in Fig. 5B, a third ionomer material having a third ion exchange capacity per unit area is applied to the first layer 82 to form an intermediate layer 86. Thereafter, as shown in Fig. 5C, a second ionomer material having a second ion exchange capacity per unit area is applied to the intermediate layer 86 to form a second layer 84. This forms an electrolyte membrane 46 in which the first layer 82, intermediate layer 86, and second layer 84 are laminated. After this, the process proceeds to step S2.

[0034] In step S2, an arrangement step is performed. In the arrangement step, the electrolyte membrane 46 is arranged between the first electrode 48 and the second electrode 50 so that the first layer 82 faces the first electrode 48 and the second layer 84 faces the second electrode 50. In this way, the membrane electrode assembly 38 is manufactured. After this, the process proceeds to step S3.

[0035] In step S3, an assembly step is performed. In the assembly step, components of the differential pressure electrolytic cell 30, such as the membrane electrode assembly 38, the pair of separators 40, the frame member 42, the support member 64, the load-applying mechanism 68, and the annular member 78, are assembled. This results in the production of the differential pressure electrolytic cell 30. Note that the differential pressure electrolytic stack 10 is produced by producing a plurality of such differential pressure electrolytic cells 30 and sandwiching the plurality of differential pressure electrolytic cells 30 in a stacked state between a pair of end plates 22.

[0036] The method for manufacturing the differential pressure electrolytic cell 30 is not limited to the above-described example. Fig. 6 is a flowchart showing an example of the electrolyte membrane formation step. Figs. 7A and 7B are cross-sectional explanatory views showing an example of the electrolyte membrane formation step. As shown in Fig. 6, in step S11, a film formation step is performed.

[0037] Specifically, as shown in FIG. 7A, in the film formation step, for example, a first film 90 is formed by applying a first ionomer material having a first ion exchange capacity per unit area onto a film-forming substrate 200. A second film 92 is formed by applying a second ionomer material having a second ion exchange capacity per unit area onto the film-forming substrate 200. A third film 94 is formed by applying a third ionomer material having a third ion exchange capacity per unit area onto the film-forming substrate 200. Then, the first film 90, the third film 94, and the second film 92 are laminated in this order to form a film laminate 96 (see FIG. 7B). Then, the process proceeds to step S12.

[0038] In step S12, a thickness adjustment step is performed. Specifically, as shown in FIG. 7B, the film laminate 96 is pressed in the thickness direction to adjust the thickness to a predetermined value. In this embodiment, the film laminate 96 is hot-pressed using a hot press device 100. The hot press device 100 has a first die 102 and a second die 104, and the film laminate 96 is hot-pressed using the first die 102 and the second die 104. As a result, the first film 90, the third film 94, and the second film 92 are bonded to each other to form the electrolyte membrane 46.

[0039] Next, a brief description of the basic operation of the differential pressure electrolytic stack 10 according to this embodiment will be given. In this embodiment, when a fluid is electrolyzed, the fluid is supplied to the supply port 24 of the differential pressure electrolytic stack 10, and a voltage is applied between the first electrode 48 and the second electrode 50 by the electrolysis power supply 18. The fluid supplied to the supply port 24 is guided to the first electrode 48 of each differential pressure electrolytic cell 30 via the fluid supply passage 32. In each differential pressure electrolytic cell 30, the fluid is electrolyzed, generating gas at the second electrode 50. The gas generated at the second electrode 50 is discharged to the gas discharge passage 13 via the generated gas discharge passage 36. The pressure of the gas generated at the second electrode 50 increases because it is sealed by the back-pressure valve 14. This allows high-pressure gas to be generated at the second electrode 50. In each differential pressure electrolytic cell 30, the discharge fluid, including unreacted fluid that was not electrolyzed, flows through the fluid discharge passage 34 to the discharge port 26 and is discharged to the outside.

[0040] In this embodiment, the differential pressure electrolytic cell 30 may be a differential pressure water electrolysis cell or an electrochemical hydrogen boost cell. Below, an example in which the differential pressure electrolytic cell 30 is a differential pressure water electrolysis cell and an example in which the differential pressure electrolytic cell 30 is an electrochemical hydrogen boost cell will be described.

[0041] When the differential pressure electrolysis cell 30 is a differential pressure water electrolysis cell, for example, the electrolyte membrane 46 may be formed as a proton exchange membrane, the first electrode 48 as an anode electrode, and the second electrode 50 as a cathode electrode. In this case, when water is supplied to the first electrode 48, the water is electrolyzed at the first electrode 48 to generate hydrogen ions and oxygen gas. The hydrogen ions move together with moisture within the electrolyte membrane 46 from the first electrode 48 to the second electrode 50. As a result, the hydrogen ions are supplied to the second electrode 50 and the electrolyte membrane 46 is humidified. At the second electrode 50, the hydrogen ions combine to generate hydrogen gas. When the pressure of the hydrogen gas generated at the second electrode 50 reaches or exceeds a threshold value, it is stored in the tank 16 via the backpressure valve 14. Unreacted water supplied to the first electrode 48 and not reacted, and the oxygen gas generated at the first electrode 48 are discharged to the outside via the fluid discharge passage 34 as exhaust fluids.

[0042] Furthermore, when the differential pressure electrolysis cell 30 is a differential pressure water electrolysis cell, for example, the electrolyte membrane 46 may be an anion exchange membrane, the first electrode 48 may be an anode electrode, and the second electrode 50 may be a cathode electrode. In this case, water supplied to the first electrode 48 moves from the first electrode 48 to the second electrode 50 within the electrolyte membrane 46. As a result, water is supplied to the second electrode 50 and the electrolyte membrane 46 is humidified. At the second electrode 50, water is electrolyzed to produce hydrogen gas and hydroxide ions. When the pressure of the hydrogen gas produced at the second electrode 50 reaches or exceeds a threshold value, it is stored in the tank 16 via the backpressure valve 14. The hydroxide ions produced at the second electrode 50 move from the second electrode 50 to the first electrode 48 within the electrolyte membrane 46. At the first electrode 48, oxygen gas and water are produced from the hydroxide ions. The water present in the first electrode 48 and the oxygen gas produced at the first electrode 48 are discharged to the outside via the fluid discharge passage 34 as discharge fluid.

[0043] Furthermore, when the differential pressure electrolysis cell 30 is a differential pressure water electrolysis cell, for example, the electrolyte membrane 46 may be formed as a proton exchange membrane, the first electrode 48 as a cathode electrode, and the second electrode 50 as an anode electrode. In this case, water supplied to the first electrode 48 moves from the first electrode 48 to the second electrode 50 within the electrolyte membrane 46. This causes water to be supplied to the second electrode 50 and humidify the electrolyte membrane 46. At the second electrode 50, water is electrolyzed to produce hydrogen ions and oxygen gas. When the pressure of the oxygen gas produced at the second electrode 50 reaches or exceeds a threshold value, it is stored in the tank 16 via the backpressure valve 14. The hydrogen ions produced at the second electrode 50 move from the second electrode 50 to the first electrode 48 within the electrolyte membrane 46. At the first electrode 48, the hydrogen ions combine to produce hydrogen gas. The water and hydrogen gas that were supplied to the first electrode 48 and did not react are discharged to the outside via the fluid discharge passage 34 as an exhaust fluid.

[0044] Furthermore, when the differential pressure electrolysis cell 30 is a differential pressure water electrolysis cell, the electrolyte membrane 46 may be an anion exchange membrane, the first electrode 48 may be a cathode, and the second electrode 50 may be an anode. In this case, when water is supplied to the first electrode 48, the water is electrolyzed at the first electrode 48 to produce hydrogen gas and hydroxide ions. The hydroxide ions migrate together with moisture through the electrolyte membrane 46 from the first electrode 48 to the second electrode 50. As a result, the hydroxide ions are supplied to the second electrode 50 and the electrolyte membrane 46 is humidified. At the second electrode 50, oxygen gas and water are produced from the hydroxide ions. When the pressure of the oxygen gas produced at the second electrode 50 reaches or exceeds a threshold value, it is stored in the tank 16 via the backpressure valve 14. Unreacted water supplied to the first electrode 48 and not reacted, and hydrogen gas produced at the first electrode 48 are discharged to the outside via the fluid discharge passage 34 as discharge fluids.

[0045] When the differential pressure electrolysis cell 30 is an electrochemical hydrogen boosting cell, for example, the electrolyte membrane 46 may be formed as a proton exchange membrane, the first electrode 48 as an anode electrode, and the second electrode 50 as a cathode electrode. In this case, when hydrogen gas containing moisture is supplied to the first electrode 48, the hydrogen gas is electrolyzed at the first electrode 48 to generate hydrogen ions. The hydrogen ions, along with the moisture, move from the first electrode 48 to the second electrode 50 within the electrolyte membrane 46. As a result, the hydrogen ions are supplied to the second electrode 50 and the electrolyte membrane 46 is humidified. At the second electrode 50, the hydrogen ions combine to generate hydrogen gas. When the pressure of the hydrogen gas generated at the second electrode 50 reaches or exceeds a threshold value, it is stored in the tank 16 via the backpressure valve 14. Unreacted hydrogen gas that is introduced to the first electrode 48 is discharged to the outside as a discharge fluid via the fluid discharge passage 34.

[0046] In this differential pressure electrolytic cell 30, moisture that moves through the electrolyte membrane 46 from the first electrode 48 to the second electrode 50 is pushed back to the first electrode 48 by the pressure of the high-pressure gas generated at the second electrode 50. Therefore, the portion of the electrolyte membrane 46 facing the second electrode 50 is more likely to dry than the portion facing the first electrode 48.

[0047] In this embodiment, the second layer 84 facing the second electrode 50 has a second ion exchange capacity greater than the first ion exchange capacity of the first layer 82 facing the first electrode 48. In other words, the second layer 84, which has an ion exchange capacity per unit area greater than the first ion exchange capacity of the first layer 82 facing the first electrode 48, is disposed to face the second electrode 50, where high-pressure gas is generated. Furthermore, the first layer 82, which has an ion exchange capacity per unit area smaller than the second ion exchange capacity of the second layer 84 facing the second electrode 50, is disposed to face the first electrode 48, where a fluid containing moisture is supplied. In this case, the maximum moisture content of the second layer 84 can be greater than the maximum moisture content of the first layer 82. Therefore, even if moisture moving from the first electrode 48 to the second electrode 50 within the electrolyte membrane 46 is pushed back by the pressure of the high-pressure gas generated at the second electrode 50, excessive drying of the second layer 84 can be prevented. In other words, variation in the water content of the electrolyte membrane 46 in the thickness direction of the electrolyte membrane 46 can be reduced. This also reduces a decrease in the efficiency of electrolysis due to drying of the electrolyte membrane 46. That is, by preventing the portion of the electrolyte membrane 46 facing the second electrode 50 from drying out, a decrease in the efficiency of electrolysis can be reduced. Furthermore, the progression of deterioration of the electrolyte membrane 46 that accompanies an increase in electrical resistance due to drying of the electrolyte membrane 46 can be reduced. That is, by preventing the portion of the electrolyte membrane 46 facing the second electrode 50 from drying out, a progression of deterioration of the electrolyte membrane 46 can be reduced. Therefore, a better differential pressure electrolytic cell 30, differential pressure electrolytic stack 10, and method for manufacturing a differential pressure electrolytic cell 30 can be provided.

[0048] The following additional notes are further disclosed regarding the above embodiment.

[0049] (Appendix 1) The differential pressure electrolytic cell (30) of the present disclosure includes a membrane electrode assembly (38) formed by sandwiching an electrolyte membrane (46) between a first electrode (48) and a second electrode (50), and is capable of applying a voltage between the first electrode and the second electrode to electrolyze a water-containing fluid supplied to the first electrode, thereby causing the second electrode to produce a gas at a pressure higher than that of the fluid, wherein the electrolyte membrane has a first layer (82) facing the first electrode and a second layer (84) facing the second electrode, and the ion exchange capacity per unit area of ​​the first layer is a first ion exchange capacity, and the ion exchange capacity per unit area of ​​the second layer is a second ion exchange capacity, and the second ion exchange capacity is greater than the first ion exchange capacity.

[0050] According to this configuration, the second ion exchange capacity of the second layer facing the second electrode is greater than the first ion exchange capacity of the first layer facing the first electrode. In this case, the maximum water content of the second layer can be greater than the maximum water content of the first layer. Therefore, even if water moving from the first electrode to the second electrode within the electrolyte membrane is pushed back by the pressure of high-pressure gas generated at the second electrode, excessive drying of the second layer can be prevented. In other words, variation in the water content of the electrolyte membrane in the thickness direction of the electrolyte membrane can be reduced. This also prevents a decrease in the efficiency of electrolysis due to drying of the electrolyte membrane. That is, by preventing the portion of the electrolyte membrane facing the second electrode from drying, a decrease in the efficiency of electrolysis can be prevented. Furthermore, the progression of deterioration of the electrolyte membrane due to an increase in electrical resistance due to drying of the electrolyte membrane can be prevented. That is, by preventing the portion of the electrolyte membrane facing the second electrode from drying, the progression of deterioration of the electrolyte membrane can be prevented. Therefore, a better differential pressure electrolytic cell can be provided.

[0051] (Appendix 2) In the differential pressure electrolytic cell described in Appendix 1, the electrolyte membrane may have an intermediate layer (86) disposed between the first layer and the second layer, and the ion exchange capacity per unit area of ​​the intermediate layer may be a third ion exchange capacity, and the third ion exchange capacity may be greater than the first ion exchange capacity and less than the second ion exchange capacity.

[0052] With this configuration, the maximum water content of the intermediate layer can be made larger than the maximum water content of the first layer and smaller than the maximum water content of the second layer, thereby further reducing variations in the water content of the electrolyte membrane in the thickness direction of the electrolyte membrane.

[0053] (Appendix 3) In the differential pressure electrolytic cell according to Supplementary Note 1 or 2, the first layer and the second layer may have different thicknesses.

[0054] According to this configuration, by making the thickness of the first layer and the thickness of the second layer different, it is possible to adjust the moisture content of the first layer and the moisture content of the second layer.

[0055] (Appendix 4) In the differential pressure electrolytic cell described in Appendix 1, the first layer may be made of a first ionomer material having an ion exchange capacity per unit area equal to the first ion exchange capacity, and the second layer may be made of a second ionomer material having an ion exchange capacity per unit area equal to the second ion exchange capacity.

[0056] With this configuration, the ion exchange capacity of the first layer and the second layer can be easily changed.

[0057] (Appendix 5) The differential pressure electrolysis stack (10) of the present disclosure includes a cell stack (20) in which a plurality of differential pressure electrolysis cells according to any one of Supplementary Notes 1 to 4 are stacked.

[0058] According to this configuration, it is possible to obtain a differential pressure electrolysis stack that exhibits the effects described in Supplementary Notes 1 to 4. Therefore, it is possible to provide a better differential pressure electrolysis stack.

[0059] (Appendix 6) The method for manufacturing a differential pressure electrolytic cell disclosed herein comprises a membrane electrode assembly formed by sandwiching an electrolyte membrane between a first electrode and a second electrode, and is capable of electrolyzing a fluid supplied to the first electrode by applying a voltage between the first electrode and the second electrode, thereby causing the second electrode to produce a gas having a higher pressure than the fluid, the method comprising: an electrolyte membrane forming step of forming the electrolyte membrane including a first layer having an ion exchange capacity per unit area of ​​a first ion exchange capacity and a second layer having an ion exchange capacity per unit area of ​​a second ion exchange capacity; and an arrangement step of arranging the electrolyte membrane between the first electrode and the second electrode so that the first layer faces the first electrode and the second layer faces the second electrode.

[0060] According to this method, it is possible to manufacture the differential pressure electrolytic cell described in Supplementary Note 1. Therefore, it is possible to provide a better method for manufacturing a differential pressure electrolytic cell.

[0061] (Appendix 7) A method for manufacturing a differential pressure electrolytic cell according to Appendix 6, wherein the electrolyte membrane forming step comprises laminating a first film (90) made of a first ionomer material having the first ion exchange capacity and a second film (92) made of a second ionomer material having the second ion exchange capacity. Rif Film laminates (96) A film forming step and a thickness adjusting step of adjusting the film laminate to a predetermined thickness by pressing the film laminate in a thickness direction.

[0062] According to this method, a good electrolyte membrane having a first layer and a second layer can be easily produced.

[0063] The present disclosure is not limited to the above-described configuration. The intermediate layer disposed between the first layer and the second layer may be formed from multiple layers. In this case, the ion exchange capacity of each of the multiple layers forming the intermediate layer is greater than the first ion exchange capacity and less than the second ion exchange capacity.

[0064] 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]

[0065] 10... Differential pressure electrolysis stack 20... Cell stack 30... Differential pressure electrolysis cell 38... Membrane electrode assembly 46...Electrolyte membrane 48...First electrode 50...Second electrode 82...First layer 84...Second layer 86...Middle layer 90...1st film 92...2nd film 96...Film laminate

Claims

1. A differential pressure electrolytic cell comprising a membrane electrode assembly formed by sandwiching an electrolyte membrane between a first electrode and a second electrode, wherein a voltage is applied between the first electrode and the second electrode to electrolyze a fluid containing water supplied to the first electrode, thereby causing the second electrode to generate a gas having a higher pressure than the fluid, The electrolyte membrane is a first layer facing the first electrode; a second layer facing the second electrode; and the ion exchange capacity per unit area of ​​the first layer is a first ion exchange capacity; the ion exchange capacity per unit area of ​​the second layer is a second ion exchange capacity; The second ion exchange capacity is greater than the first ion exchange capacity.

2. 2. The differential pressure electrolytic cell according to claim 1, the electrolyte membrane has an intermediate layer disposed between the first layer and the second layer; the ion exchange capacity per unit area of ​​the intermediate layer is a third ion exchange capacity; a differential pressure electrolytic cell, wherein the third ion exchange capacity is greater than the first ion exchange capacity and less than the second ion exchange capacity;

3. 2. The differential pressure electrolytic cell according to claim 1, A differential pressure electrolytic cell, wherein the thickness of the first layer and the thickness of the second layer are different from each other.

4. 2. The differential pressure electrolytic cell according to claim 1, the first layer is composed of a first ionomer material having an ion exchange capacity per unit area equal to the first ion exchange capacity; a differential pressure electrolytic cell, wherein the second layer is composed of a second ionomer material having an ion exchange capacity per unit area equal to the second ion exchange capacity;

5. A differential pressure electrolysis stack comprising a cell stack in which a plurality of differential pressure electrolysis cells according to any one of claims 1 to 4 are stacked.

6. A method for manufacturing a differential pressure electrolytic cell, comprising: a membrane electrode assembly formed by sandwiching an electrolyte membrane between a first electrode and a second electrode; and applying a voltage between the first electrode and the second electrode to electrolyze a fluid supplied to the first electrode, thereby generating a gas at the second electrode having a higher pressure than the fluid, the method comprising: an electrolyte membrane forming step of forming the electrolyte membrane including a first layer having an ion exchange capacity per unit area of ​​a first ion exchange capacity and a second layer having an ion exchange capacity per unit area of ​​a second ion exchange capacity; a disposing step of disposing the electrolyte membrane between the first electrode and the second electrode such that the first layer faces the first electrode and the second layer faces the second electrode; A method for manufacturing a differential pressure electrolysis cell, comprising:

7. 7. A method for producing a differential pressure electrolytic cell according to claim 6, comprising the steps of: In the electrolyte membrane forming step, a film forming step of laminating a first film made of a first ionomer material having the first ion exchange capacity and a second film made of a second ionomer material having the second ion exchange capacity to form a film laminate; a thickness adjusting step of adjusting the film laminate to a predetermined thickness by pressing the film laminate in a thickness direction; A method for manufacturing a differential pressure electrolytic cell comprising:

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