Differential pressure type electrolytic cell, differential pressure type electrolytic stack, and method for manufacturing differential pressure type electrolytic cell

Abstract

The invention provides a differential pressure type electrolytic cell, a differential pressure type electrolytic stack, and a method for manufacturing the differential pressure type electrolytic cell. In a differential pressure type electrolytic cell (30) capable of generating a gas having a higher pressure than the fluid in a second electrode by applying a voltage between a first electrode (48) and the second electrode (50) to decompose the 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. The second layer faces the second electrode, 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, and the second ion exchange capacity is larger than the first ion exchange capacity. Therefore, a better differential pressure type electrolytic cell, a differential pressure type electrolytic stack and a method for manufacturing the differential pressure type electrolytic cell can be provided.

Description

Technical Field

[0001] The present invention relates to a pressure differential electrolytic cell, a pressure differential electrolytic stack and a method for manufacturing the pressure differential electrolytic cell. Background Art

[0002] In recent years, in order to ensure that more people have access to affordable, reliable, sustainable, and advanced energy, research and development of pressure differential electrolysis stacks that help improve energy efficiency are underway.

[0003] For example, Japanese Patent No. 7031719 discloses a pressure differential water electrolysis stack having a polymer electrolyte membrane having excellent hydrogen barrier properties. Summary of the Invention

[0004] A better pressure differential electrolysis cell, a pressure differential electrolysis stack, and a method for manufacturing a pressure differential electrolysis cell are desired.

[0005] The purpose of the present invention is to solve the above-mentioned technical problems.

[0006] The first embodiment of the present invention is a pressure differential electrolysis cell having a membrane electrode structure formed by clamping an electrolyte membrane by 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 generating a gas having a pressure higher than that of the fluid at the second electrode, wherein the electrolyte membrane has a first layer and a second layer, wherein the first layer faces the first electrode; and the second layer faces the second electrode, the ion exchange capacity per unit area of ​​the first layer is the first ion exchange capacity, and the ion exchange capacity per unit area of ​​the second layer is the second ion exchange capacity, and the second ion exchange capacity is larger than the first ion exchange capacity.

[0007] A second aspect of the present invention is a pressure differential electrolysis stack including a cell stack formed by stacking a plurality of the pressure differential electrolysis cells of the first aspect.

[0008] The third embodiment of the present invention is a method for manufacturing a pressure differential electrolysis cell, wherein the pressure differential electrolysis cell has a membrane electrode structure formed by clamping an electrolyte membrane between a first electrode and a second electrode, and a voltage is applied between the first electrode and the second electrode to electrolyze the fluid supplied to the first electrode, so that a gas with a pressure higher than that of the fluid can be generated at the second electrode. The method for manufacturing the pressure differential electrolysis cell has an electrolyte membrane forming step and a configuration step, wherein, in the electrolyte membrane forming step, the electrolyte membrane including a first layer and a second layer is formed, the ion exchange capacity per unit area of ​​the first layer is the first ion exchange capacity, and the ion exchange capacity per unit area of ​​the second layer is the second ion exchange capacity; in the configuration step, the electrolyte membrane is configured between the first electrode and the second electrode in such a manner that the first layer faces the first electrode and the second layer faces the second electrode.

[0009] According to the present invention, a better pressure differential electrolysis cell, a pressure differential electrolysis stack, and a method for manufacturing a pressure differential electrolysis cell can be provided.

[0010] The above-mentioned objects, features and advantages will be easily understood through the following description of the embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of an electrolysis device having a pressure differential electrolysis stack according to an embodiment.

[0012] Figure 2 It is a cross-sectional view of a pressure differential electrolysis cell.

[0013] Figure 3 It is a cross-sectional view illustrating the electrolyte membrane.

[0014] Figure 4 This is a flowchart showing an example of a method for manufacturing a pressure differential electrolytic cell.

[0015] Figures 5A to 5C This is a cross-sectional explanatory diagram showing an example of a method for manufacturing a pressure differential electrolytic cell.

[0016] Figure 6 This is a flowchart showing an example of the electrolyte membrane forming process.

[0017] Figure 7A and Figure 7B It is a cross-sectional explanatory diagram showing an example of the electrolyte membrane forming step. DETAILED DESCRIPTION

[0018] A differential pressure electrolysis cell has a membrane electrode assembly (MEA). The MEA is formed by sandwiching an electrolyte membrane between a first electrode and a second electrode. By applying a voltage between the first and second electrodes, the MEA electrolyzes a fluid containing water supplied to the first electrode, generating a gas at the second electrode at a higher pressure than the fluid supplied to the first electrode. In this MEA, the electrolyte membrane is humidified by the fluid containing water supplied to the first electrode.

[0019] Specifically, the moisture supplied to the first electrode moves from the first electrode to the second electrode within the electrolyte membrane. However, since the moisture moving from the first electrode to the second electrode within the electrolyte membrane is pushed back to the first electrode by the pressure of the high-pressure gas generated at the second electrode, the portion of the electrolyte membrane facing the second electrode is more likely to dry out than the portion facing the first electrode. In other words, the moisture content of the electrolyte membrane tends to vary in the thickness direction of the electrolyte membrane. When this drying of the electrolyte membrane occurs, the movement of ions within the electrolyte membrane is hindered, sometimes resulting in reduced electrolysis efficiency or degradation of the electrolyte membrane accompanied by increased resistance. The present invention can provide a pressure differential electrolysis cell, a pressure differential electrolysis stack, and a method for manufacturing a pressure differential electrolysis cell, which can suppress the reduction in electrolysis efficiency or the progression of electrolyte membrane degradation by configuring the electrolyte membrane to suppress drying of the portion of the electrolyte membrane facing the second electrode.

[0020] Figure 1 Schematic diagram of an electrolysis device 12 having a pressure differential electrolysis stack 10 according to an embodiment. Figure 1 As shown, the electrolysis device 12 includes, for example, a differential pressure electrolysis stack 10 , a gas discharge channel 13 , a back pressure valve 14 , a storage tank 16 , and an electrolysis power supply 18 .

[0021] The pressure differential electrolysis stack 10 is a pressure differential electrolysis stack capable of generating high-pressure gas by electrolyzing a fluid. The pressure differential electrolysis stack 10 includes a cell stack 20 , a pair of end plates 22 , a supply port 24 , a discharge port 26 , and a generated gas discharge port 28 .

[0022] The battery stack 20 is formed by stacking a plurality of pressure differential electrolytic cells 30 on each other along the X direction. The plurality of pressure differential electrolytic cells 30 are stacked, for example, in the vertical direction. The plurality of pressure differential electrolytic cells 30 can also be stacked in a direction intersecting the vertical direction (for example, the horizontal direction). A pair of end plates 22 clamp the plurality of pressure differential electrolytic cells 30 from the X direction. The supply port 24 supplies fluid to the interior of the battery stack 20. The exhaust port 26 discharges the exhaust fluid to the outside of the battery stack 20. The generated gas exhaust port 28 guides the gas generated inside the battery stack 20 to the gas outlet channel 13. The generated gas exhaust port 28 is, for example, provided in the central portion of the end plate 22.

[0023] The gas outlet passage 13 guides the generated gas from the battery stack 20 to the storage tank 16. A backpressure valve 14 is provided on the gas outlet passage 13. The backpressure valve 14 opens when the pressure of the gas extracted from the pressure-differential electrolysis stack 10 exceeds a predetermined threshold. The backpressure valve 14 closes when the pressure of the generated gas extracted from the pressure-differential electrolysis stack 10 falls below the threshold. The storage tank 16 is a high-pressure gas storage tank capable of storing the gas generated by the pressure-differential electrolysis stack 10.

[0024] Figure 2 30 is a cross-sectional view of a pressure differential electrolytic cell. Figure 2 As shown, in the pressure differential electrolysis cell 30, a fluid supply communication hole 32, a fluid discharge communication hole 34, and a generated gas discharge communication hole 36 are provided in a manner penetrating in the X direction. The fluid supply communication holes 32 of the plurality of pressure differential electrolysis cells 30 are connected to each other. The fluid supply communication hole 32 is connected to the supply port 24 (see Figure 1 ) are connected. The fluid discharge communication holes 34 of the plurality of pressure differential electrolytic cells 30 are connected to each other. The fluid discharge communication holes 34 are connected to the discharge port 26 (refer to Figure 1 ) are connected. The generated gas discharge passages 36 of the plurality of pressure differential electrolytic cells 30 are connected to each other. The generated gas discharge passages 36 are connected to the generated gas discharge port 28 (see Figure 1 ) connected.

[0025] The fluid supply manifold 32 and the fluid discharge manifold 34 are provided at positions separated from each other on the outer periphery of the pressure differential electrolysis cell 30. The generated gas discharge manifold 36 is provided in the center of the pressure differential electrolysis cell 30. The generated gas discharge manifold 36 is located between the fluid supply manifold 32 and the fluid discharge manifold 34. The fluid supply manifold 32 supplies fluid to the first electrode 48. The fluid (discharge fluid) flowing through the first electrode 48 is directed to the fluid discharge manifold 34. The gas generated at the second electrode 50 is directed to the generated gas discharge manifold 36.

[0026] The pressure differential electrolysis cell 30 includes a membrane electrode structure 38, a pair of separators 40, and a frame member 42. The membrane electrode structure 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 structure 38. A sealing member 44 is provided between the frame member 42 and the separator 40 to prevent the fluid and the exhaust fluid from flowing out. Figure 2 In the present invention, the separator 40 located in the X1 direction of the membrane electrode structure 38 in a pair of separators 40 is sometimes referred to as the "first separator 40a", and the separator 40 located in the X2 direction of the membrane electrode structure 38 in a pair of separators 40 is sometimes referred to as the "second separator 40b".

[0027] The membrane electrode assembly 38 is formed in a ring shape (for example, a torus shape). The membrane electrode assembly 38 includes 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). In addition, the electrolyte membrane 46 may also be an anion exchange membrane (AEM). The electrolyte membrane 46 prevents the gas (generated gas) generated by the second electrode 50 from passing toward the first electrode 48. The specific structure of the electrolyte membrane 46 will be described later.

[0028] The first electrode 48 includes a first catalyst layer 52, a protective sheet 54, and a first power supply 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 power supply 56 also serves as a fluid diffusion layer for supplying fluid to the first catalyst layer 52. The first power supply 56 includes a portion formed of a porous member. The protective sheet 54 is disposed between the first catalyst layer 52 and the first power supply 56. The protective sheet 54 prevents the electrolyte membrane 46 from being damaged by the generated gas of the second electrode 50 being pushed toward the first power supply 56. A plurality of through holes 58 are formed in the protective sheet 54.

[0029] The outer diameter of the second electrode 50 is smaller than that of the first electrode 48. The second electrode 50 includes a second catalyst layer 60 and a second power supply 62. The second catalyst layer 60 is bonded to the other surface 46b (the surface facing the X2 direction) of the electrolyte membrane 46. The second power supply 62 also functions as a gas diffusion layer for conducting the generated gas generated by the second catalyst layer 60. The second power supply 62 includes a portion formed of a porous member.

[0030] A support member 64 is provided between the first separator 40a and the first power supply element 56 to support the membrane electrode assembly 38. A communication channel 66 is formed in the support member 64. The communication channel 66 guides the fluid introduced from the fluid supply passage 32 into the first power supply element 56. Furthermore, the communication channel 66 guides the fluid discharged from the first power supply element 56 to the fluid discharge passage 34.

[0031] A load applying mechanism 68 for applying force to the second power supply 62 in the X1 direction is provided between the second separator 40b and the second power supply 62. The load applying mechanism 68 includes, for example, a leaf spring 70, a leaf spring support frame 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 sealing member 80 is disposed between the annular member 78 and the load applying mechanism 68. The sealing member 80 is in contact with each of the second separator 40b and the electrolyte membrane 46.

[0032] like Figure 1 As shown, the electrolysis power supply 18 is a DC power supply. Figure 2 A voltage is applied between the first power supply 56 and the second power supply 62 shown.

[0033] Figure 3 4 is a cross-sectional view illustrating the electrolyte membrane 46. Figure 3 As shown, the electrolyte membrane 46 has a laminated structure formed by laminating three layers. Specifically, the electrolyte membrane 46 includes 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.

[0034] The first layer 82 is composed of a first ionomer material having a first ion exchange capacity per unit area. The second layer 84 is composed of a second ionomer material having a second ion exchange capacity per unit area. The intermediate layer 86 is composed of a third ionomer material having a third ion exchange capacity per unit area.

[0035] 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 and smaller 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 and smaller than the maximum water content per unit area of ​​the second layer 84.

[0036] The first layer 82, the second layer 84 and the intermediate layer 86 have the same thickness as each other. In addition, the thickness of each of the first layer 82, the second layer 84 and the intermediate layer 86 may be different from each other. In this embodiment, the intermediate layer 86 can be omitted. In this case, the electrolyte membrane 46 is formed by only two layers (the first layer 82 and the second layer 84). In addition, the electrolyte membrane 46 can be formed by stacking four or more layers, for example. In other words, the electrolyte membrane 46 can have a plurality of intermediate layers 86. In this case, the ion exchange capacity per unit area of ​​the plurality of intermediate layers 86 may be the same as or different from each other. When the ion exchange capacity per unit area of ​​the plurality of intermediate layers 86 is different from each other, it is preferred to configure the plurality of intermediate layers 86 in a manner such that the ion exchange capacity per unit area becomes larger toward the X1 direction.

[0037] The electrolysis device 12 may have components other than the components described above.

[0038] Next, a method for manufacturing the pressure differential electrolytic cell 30 will be described. Figure 4 This is a flowchart showing an example of a method for manufacturing the pressure differential electrolytic cell 30 . Figures 5A to 5C 1 is a cross-sectional view illustrating an example of a method for manufacturing a pressure differential electrolytic cell 30. Figure 4 As shown, an electrolyte membrane forming step is performed in step S1. That is, the electrolyte membrane 46 is formed in the electrolyte membrane forming step.

[0039] Specifically, if Figure 5A As shown, for example, a first ionomer material having an ion exchange capacity per unit area of ​​a first ion exchange capacity is applied to a substrate 200 for film formation to form the first layer 82. Figure 5B As shown in FIG. 1 , the membrane intermediate layer 86 is formed by coating the first layer 82 with a third ion exchange capacity per unit area of ​​a third ion exchange capacity. Figure 5C As shown, the second layer 84 is formed by coating the intermediate layer 86 with a second ionomer material having a second ion exchange capacity per unit area. Thus, the electrolyte membrane 46 is formed by laminating the first layer 82, the intermediate layer 86, and the second layer 84. The process then proceeds to step S2.

[0040] In step S2, the placement step is performed. In this placement step, the electrolyte membrane 46 is placed 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. Thus, the membrane electrode assembly 38 is manufactured. The process then proceeds to step S3.

[0041] In step S3, an assembly step is performed. In this assembly step, the components of the pressure differential electrolysis 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. Thus, the pressure differential electrolysis cell 30 is manufactured. Furthermore, by manufacturing a plurality of such pressure differential electrolysis cells 30 and sandwiching them between the pair of end plates 22 in a stacked state, the pressure differential electrolysis stack 10 is manufactured.

[0042] The method for manufacturing the pressure differential electrolytic cell 30 is not limited to the above-mentioned example. Figure 6 This is a flowchart showing an example of the electrolyte membrane forming process. Figure 7A and Figure 7B 1 is a cross-sectional view illustrating an example of the steps for forming an electrolyte membrane. Figure 6 As shown, a film forming step is performed in step S11.

[0043] Specifically, if Figure 7A As shown, in the film forming step, for example, a first film 90 is formed by coating a first ionomer material having an ion exchange capacity of a first ion exchange capacity per unit area on a film forming substrate 200. Furthermore, a second film 92 is formed by coating a second ionomer material having an ion exchange capacity of a second ion exchange capacity per unit area on the film forming substrate 200. Furthermore, a third film 94 is formed by coating a third ionomer material having an ion exchange capacity of a third ion exchange capacity per unit area on the film forming substrate 200. Thereafter, a film stack 96 is formed by sequentially stacking the first film 90, the third film 94, and the second film 92 (see FIG. 1 ). Figure 7B ). Then, transfer to step S12.

[0044] In step S12, a thickness adjustment step is performed. Specifically, Figure 7B As shown, the membrane stack 96 is pressed in the thickness direction to adjust to a predetermined thickness. In this embodiment, the membrane stack 96 is hot-pressed by a hot press apparatus 100. The hot press apparatus 100 includes a first die 102 and a second die 104, and the membrane stack 96 is hot-pressed by the first die 102 and the second die 104. In this manner, the first membrane 90, the third membrane 94, and the second membrane 92 are bonded to each other to form the electrolyte membrane 46.

[0045] Next, the basic operation of the differential pressure electrolysis stack 10 according to this embodiment will be briefly described. In this embodiment, when electrolyzing a fluid, the fluid is supplied to the supply port 24 of the differential pressure electrolysis 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 directed to the first electrode 48 of each differential pressure electrolysis cell 30 through the fluid supply manifold 32. In each differential pressure electrolysis 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 channel 13 through the generated gas discharge manifold 36. The gas generated at the second electrode 50 is sealed by the back pressure valve 14, causing the pressure to rise. This allows high-pressure gas to be generated at the second electrode 50. In each differential pressure electrolysis cell 30, the discharged fluid, including unreacted fluid that has not been electrolyzed, flows through the fluid discharge manifold 34 to the discharge port 26 and is discharged to the outside.

[0046] In this embodiment, the pressure differential electrolysis cell 30 can be a pressure differential water electrolysis cell or an electrochemical hydrogen boost cell. The following describes examples of the pressure differential electrolysis cell 30 being a pressure differential water electrolysis cell and an electrochemical hydrogen boost cell.

[0047] If the differential pressure electrolysis cell 30 is a differential pressure water electrolysis cell, for example, the electrolyte membrane 46 can be formed as a proton exchange membrane, the first electrode 48 can be formed as an anode electrode, and the second electrode 50 can be formed as a cathode electrode. In this case, when water is supplied to the first electrode 48, it is electrolyzed at the first electrode 48, generating hydrogen ions and oxygen gas. The hydrogen ions, along with the water, migrate within the electrolyte membrane 46 from the first electrode 48 to the second electrode 50. This causes the hydrogen ions to be supplied to the second electrode 50, humidifying the electrolyte membrane 46. At the second electrode 50, the hydrogen ions combine to generate hydrogen gas. When the hydrogen gas generated by the second electrode 50 reaches a pressure above a threshold, it is stored in the storage tank 16 via the back pressure valve 14. Unreacted water supplied to the first electrode 48 and oxygen gas generated by the first electrode 48 are discharged to the outside through the fluid discharge passage 34 as exhaust fluid.

[0048] If the differential pressure electrolysis cell 30 is a differential pressure water electrolysis cell, for example, the electrolyte membrane 46 can be formed as an anion exchange membrane, the first electrode 48 can be formed as an anode electrode, and the second electrode 50 can be formed as 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. This causes water to be supplied to the second electrode 50 and humidifies the electrolyte membrane 46. At the second electrode 50, the water is electrolyzed to produce hydrogen gas and hydroxide ions. When the hydrogen gas produced by the second electrode 50 reaches a pressure above a threshold, it is stored in the storage tank 16 via the back pressure valve 14. The hydroxide ions produced by 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 generated from the hydroxide ions. The water present in the first electrode 48 and the oxygen gas produced by the first electrode 48 are discharged to the outside as exhaust fluid through the fluid discharge passage 34.

[0049] Furthermore, if the differential pressure electrolysis cell 30 is a differential pressure water electrolysis cell, for example, the electrolyte membrane 46 can be formed as a proton exchange membrane, the first electrode 48 can be formed as a cathode electrode, and the second electrode 50 can be formed 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 humidifies the electrolyte membrane 46. At the second electrode 50, the water is electrolyzed to produce hydrogen ions and oxygen gas. When the oxygen gas produced by the second electrode 50 reaches a pressure above a threshold, it is stored in the storage tank 16 via the back pressure valve 14. The hydrogen ions produced by 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. Unreacted water and hydrogen gas supplied to the first electrode 48 are discharged to the outside as exhaust fluid through the fluid discharge passage 34.

[0050] If the pressure differential electrolysis cell 30 is a pressure differential water electrolysis cell, for example, the electrolyte membrane 46 can be formed as an anion exchange membrane, the first electrode 48 can be formed as a cathode electrode, and the second electrode 50 can be formed as an anode electrode. In this case, when water is supplied to the first electrode 48, the water is electrolyzed at the first electrode 48, generating hydrogen gas and hydroxide ions. The hydroxide ions, along with the water, migrate within the electrolyte membrane 46 from the first electrode 48 to the second electrode 50. This causes the hydroxide ions to be supplied to the second electrode 50, humidifying the electrolyte membrane 46. At the second electrode 50, oxygen gas and water are generated from the hydroxide ions. When the oxygen gas generated by the second electrode 50 reaches a pressure above a threshold, it is stored in the storage tank 16 via the back pressure valve 14. Unreacted water supplied to the first electrode 48 and hydrogen gas generated by the first electrode 48 are discharged to the outside as exhaust fluid through the fluid discharge passage 34.

[0051] If the differential pressure electrolysis cell 30 is an electrochemical hydrogen boost cell, for example, the electrolyte membrane 46 can be formed as a proton exchange membrane, the first electrode 48 can be formed as an anode electrode, and the second electrode 50 can be formed as a cathode electrode. In this case, when hydrogen gas containing water 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 water, migrate within the electrolyte membrane 46 from the first electrode 48 to the second electrode 50. This causes the hydrogen ions to be supplied to the second electrode 50, humidifying the electrolyte membrane 46. At the second electrode 50, the hydrogen ions combine to generate hydrogen gas. When the hydrogen gas generated by the second electrode 50 reaches a pressure above a threshold, it is stored in the storage tank 16 via the back pressure valve 14. Unreacted hydrogen gas that was directed to the first electrode 48 but did not react is discharged to the outside through the fluid discharge passage 34 as exhaust fluid.

[0052] In this differential pressure electrolysis cell 30, moisture that has migrated from the first electrode 48 to the second electrode 50 in the electrolyte membrane 46 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 out than the portion facing the first electrode 48.

[0053] In this embodiment, the second ion exchange capacity of the second layer 84 facing the second electrode 50 is 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 a greater ion exchange capacity per unit area than the first ion exchange capacity of the first layer 82 facing the first electrode 48, is positioned facing the second electrode 50, where high-pressure gas is generated. Furthermore, the first layer 82, which has a smaller ion exchange capacity per unit area than the second ion exchange capacity of the second layer 84 facing the second electrode 50, is positioned facing the first electrode 48, where a fluid containing water is supplied. In this case, the maximum water content of the second layer 84 can be made greater than the maximum water content of the first layer 82. Therefore, even if water that migrates 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 by the second electrode 50, excessive drying of the second layer 84 can be prevented. In other words, variations in the water content of the electrolyte membrane 46 can be suppressed across its thickness. This also suppresses the reduction in electrolysis efficiency due to drying of the electrolyte membrane 46. Specifically, by suppressing the drying of the portion of the electrolyte membrane 46 facing the second electrode 50, the reduction in electrolysis efficiency can be suppressed. Furthermore, the degradation of the electrolyte membrane 46, which is accompanied by an increase in resistance due to drying of the electrolyte membrane 46, can be suppressed. Specifically, by suppressing the drying of the portion of the electrolyte membrane 46 facing the second electrode 50, the progression of degradation of the electrolyte membrane 46 can be suppressed. Consequently, a more favorable differential pressure electrolysis cell 30, a differential pressure electrolysis stack 10, and a method for manufacturing the differential pressure electrolysis cell 30 can be provided.

[0054] The following supplementary notes are further disclosed regarding the above-mentioned embodiment.

[0055] (Note 1) The pressure differential electrolysis cell (30) of the present invention has a membrane electrode structure (38) formed by clamping an electrolyte membrane (46) by a first electrode (48) and a second electrode (50). By applying a voltage between the first electrode and the second electrode, a fluid containing water supplied to the first electrode is electrolyzed, thereby generating a gas with a pressure higher than that of the fluid at the second electrode. The electrolyte membrane has a first layer (82) and a second layer (84), wherein the first layer faces the first electrode; and the second layer faces the second electrode. The ion exchange capacity per unit area of ​​the first layer is the first ion exchange capacity, and the ion exchange capacity per unit area of ​​the second layer is the second ion exchange capacity, and the second ion exchange capacity is larger than the first ion exchange capacity.

[0056] With this structure, 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 moisture content of the second layer can be made greater than the maximum moisture content of the first layer. Therefore, even if moisture migrating from the first electrode to the second electrode within the electrolyte membrane is pushed back by the pressure of the high-pressure gas generated at the second electrode, excessive drying of the second layer can be prevented. In other words, variations in the moisture content of the electrolyte membrane across its thickness can be suppressed. This also prevents a decrease in electrolysis efficiency due to drying of the electrolyte membrane. Specifically, by suppressing drying of the portion of the electrolyte membrane facing the second electrode, a decrease in electrolysis efficiency can be suppressed. Furthermore, degradation of the electrolyte membrane, which is accompanied by an increase in resistance, due to drying of the electrolyte membrane can be suppressed. Specifically, by suppressing drying of the portion of the electrolyte membrane facing the second electrode, the progression of electrolyte membrane degradation can be suppressed. Consequently, a more optimal pressure-differential electrolysis cell can be provided.

[0057] (Note 2) In the pressure differential electrolytic cell described in Note 1, the electrolyte membrane may have an intermediate layer (86) arranged between the first layer and the second layer, and the ion exchange capacity per unit area of ​​the intermediate layer is a third ion exchange capacity, and the third ion exchange capacity is larger than the first ion exchange capacity and smaller than the second ion exchange capacity.

[0058] With this structure, the maximum moisture content of the intermediate layer can be made larger than the maximum moisture content of the first layer and smaller than the maximum moisture content of the second layer. This further reduces the variation in moisture content of the electrolyte membrane in the thickness direction of the electrolyte membrane.

[0059] (Note 3) In the pressure differential electrolytic cell according to Supplementary Note 1 or 2, the thickness of the first layer and the thickness of the second layer may be different from each other.

[0060] According to such a configuration, by making the thickness of the first layer and the thickness of the second layer different from each other, the moisture content of the first layer and the moisture content of the second layer can be adjusted.

[0061] (Note 4) In the pressure differential electrolytic cell described in Supplementary Note 1, the first layer may be composed of a first ionomer material having an ion exchange capacity per unit area of ​​the first ion exchange capacity, and the second layer may be composed of a second ionomer material having an ion exchange capacity per unit area of ​​the second ion exchange capacity.

[0062] According to such a structure, the ion exchange capacity of the first layer and the ion exchange capacity of the second layer can be easily changed.

[0063] (Note 5) The pressure differential electrolysis stack (10) of the present invention comprises a cell stack (20) formed by stacking a plurality of pressure differential electrolysis cells according to any one of Supplementary Notes 1 to 4.

[0064] According to such a configuration, it is possible to obtain a pressure differential electrolysis stack that achieves the effects described in Supplementary Notes 1 to 4. Thus, it is possible to provide a better pressure differential electrolysis stack.

[0065] (Note 6) In the manufacturing method of the pressure differential electrolysis cell of the present invention, the pressure differential electrolysis cell has a membrane electrode structure formed by clamping an electrolyte membrane by a first electrode and a second electrode, and a voltage is applied between the first electrode and the second electrode to electrolyze the fluid supplied to the first electrode, so that a gas with a pressure higher than that of the fluid can be generated at the second electrode. The manufacturing method of the pressure differential electrolysis cell has an electrolyte membrane forming step and a configuration step, wherein, in the electrolyte membrane forming step, the electrolyte membrane including a first layer and a second layer is formed, the ion exchange capacity per unit area of ​​the first layer is the first ion exchange capacity, and the ion exchange capacity per unit area of ​​the second layer is the second ion exchange capacity; in the configuration step, the electrolyte membrane is configured between the first electrode and the second electrode in such a manner that the first layer faces the first electrode and the second layer faces the second electrode.

[0066] According to such a method, it is possible to manufacture the pressure differential electrolytic cell described in Supplementary Note 1. Thus, it is possible to provide a more favorable method for manufacturing a pressure differential electrolytic cell.

[0067] (Note 7) In the method for manufacturing a differential pressure electrolytic cell described in Appendix 6, the electrolyte membrane forming step may include a membrane forming step and a thickness adjusting step, wherein, in the membrane forming step, a membrane stack (96) is formed by stacking a first membrane (90) made of a first ionomer material having the first ion exchange capacity and a second membrane (92) made of a second ionomer material having the second ion exchange capacity; and in the thickness adjusting step, the membrane stack is adjusted to a predetermined thickness by punching it in the thickness direction.

[0068] According to such a method, a good electrolyte membrane having the first layer and the second layer can be easily manufactured.

[0069] The present invention is not limited to the above-described structure. The intermediate layer disposed between the first layer and the second layer may be formed of a plurality of layers. In this case, the ion exchange capacity of each of the plurality of layers forming the intermediate layer is greater than the first ion exchange capacity and smaller than the second ion exchange capacity.

[0070] The present invention has been described in detail, but the present invention is not limited to the above-mentioned embodiments. These embodiments can be supplemented, replaced, changed, partially deleted, etc. in a variety of ways without departing from the scope of the present invention or the scope of the present invention derived from the contents recorded in the technical solution and its equivalents. In addition, these embodiments can also be implemented in combination. For example, in the above-mentioned embodiment, the order of each action or the order of each processing is shown as an example and is not limited to these. In addition, the same applies to the case where numerical values ​​or formulas are used in the description of the above-mentioned embodiment.

Claims

1. A pressure-differential electrolysis cell comprising a membrane electrode structure 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 generating a gas having a higher pressure than that of the fluid at the second electrode, characterized in that: The electrolyte membrane comprises a first layer and a second layer, wherein: The first layer faces the first electrode; The second layer faces the second electrode, 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. The pressure differential electrolytic cell according to claim 1, characterized in that The electrolyte membrane includes an intermediate layer disposed between the first layer and the second layer. The ion exchange capacity per unit area of ​​the intermediate layer is the third ion exchange capacity, The third ion exchange capacity is larger than the first ion exchange capacity and smaller than the second ion exchange capacity.

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

4. The pressure differential electrolytic cell according to claim 1, characterized in that 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. 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 pressure differential electrolysis stack, characterized in that: A cell stack is provided in which a plurality of the pressure differential electrolytic cells according to any one of claims 1 to 4 are stacked.

6. A method for manufacturing a pressure-differential electrolysis cell, wherein the pressure-differential electrolysis cell comprises a membrane electrode structure 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 supplied to the first electrode, thereby generating a gas having a higher pressure than that of the fluid at the second electrode, wherein: There are an electrolyte membrane forming step and a disposing step, wherein, In the electrolyte membrane forming step, the electrolyte membrane is formed to include a first layer and a second layer, wherein 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; In the arranging step, the electrolyte membrane is arranged between the first electrode and the second electrode in such a manner that the first layer faces the first electrode and the second layer faces the second electrode.

7. The method for manufacturing a pressure differential electrolytic cell according to claim 6, wherein: The electrolyte membrane forming step includes a membrane forming step and a thickness adjusting step, wherein: In the membrane forming step, a membrane stack is formed by laminating a first membrane formed of a first ionomer material having the first ion exchange capacity and a second membrane formed of a second ionomer material having the second ion exchange capacity; In the thickness adjustment step, the film stack is adjusted to a predetermined thickness by punching the film stack in a thickness direction.

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