Differential pressure electrolytic cells and differential pressure electrolytic stacks

Abstract

The present invention provides a differential pressure electrolytic cell and a differential pressure electrolytic stack that can suppress the elution of metal ions from exposed metal portions where the coating has peeled off, thereby preventing the deterioration of the electrolyte membrane. [Solution] The differential pressure electrolytic cell 10 comprises a metal separator 44 positioned above the second electrode catalyst layer, a conductive sheet 78 positioned on a power supply unit located between the metal separator 44 and the second electrode catalyst layer, and a metal spring member 80 that contacts the metal separator 44 and the conductive sheet 78 and presses the conductive sheet downward. A capturing member 124 capable of capturing cations is provided on the outer periphery of the conductive sheet 78.

Description

Technical Field

[0001] The present disclosure relates to a differential pressure electrolysis cell and a differential pressure electrolysis stack. Background Art

[0002] In recent years, technological development related to differential pressure electrolysis stacks that contribute to energy efficiency has been carried out to enable more people to secure access to affordable, reliable, sustainable and advanced energy.

[0003] Japanese Patent No. 7037965 discloses a configuration of a differential pressure electrolysis cell in a differential pressure electrolysis stack. Prior Art Documents Patent Documents

[0004] Patent Document 1 Japanese Patent No. 7037965 Summary of the Invention Problem to be Solved by the Invention

[0005] There is a long-felt need for improved differential pressure electrolysis cells and differential pressure electrolysis stacks.

[0006] An object of the present disclosure is 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 having an electrolyte membrane and a first electrode catalyst layer and a second electrode catalyst layer bonded to both sides of the electrolyte membrane, wherein the electrolytic cell is capable of generating a product gas at a pressure higher than that of the electrolytic fluid in the second electrode catalyst layer by electrolysis of an electrolytic fluid supplied to the first electrode catalyst layer, the differential pressure electrolytic cell comprising a metal separator disposed above the second electrode catalyst layer, a conductive sheet disposed on a power supply located between the metal separator and the second electrode catalyst layer, and a metal spring member that contacts the metal separator and the conductive sheet and presses the conductive sheet downward, wherein a capture member capable of capturing cations is provided on the outer periphery of the conductive sheet.

[0008] A second aspect of this disclosure is a differential pressure electrolytic stack in which a plurality of the differential pressure electrolytic cells described above are stacked. [Effects of the Invention]

[0009] This disclosure may provide better differential pressure electrolytic cells and differential pressure electrolytic stacks. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram of an electrolytic apparatus equipped with a differential pressure type electrolytic stack according to one embodiment. [Figure 2] Figure 2 is a cross-sectional view of a differential pressure electrolytic cell. [Figure 3] Figure 3 is a top view of the spring member shown in Figure 2, viewed from the direction of arrow III. [Figure 4] Figure 4 is a plan view of the conductive sheet. [Figure 5] Figure 5 is a partially abbreviated cross-sectional view along the VV line in Figure 3. [Figure 6] Figure 6 is a partially abbreviated cross-sectional view showing a modified example of a radial groove. [Modes for carrying out the invention]

[0011] A differential-pressure electrolytic cell can generate a product gas at a higher pressure than the electrolytic fluid in the second electrode catalyst layer of a membrane electrode assembly by electrolyzing the electrolytic fluid supplied to the first electrode catalyst layer of the membrane electrode assembly. In this type of differential-pressure electrolytic cell, a metal separator is placed above the second electrode catalyst layer. Between the metal separator and the second electrode catalyst layer, a metal spring member is placed to press the power supply toward the second electrode catalyst layer. The metal separator and spring member are coated, for example, to prevent the elution of metal ions (cations).

[0012] However, the coating may peel off at the contact point between the metal separator and the spring member. Furthermore, the coating may peel off due to aging. If water droplets adhere to the exposed metal portion where the coating has peeled off, metal ions may leach out. If water containing metal ions flows down from the spring member and comes into contact with the electrolyte membrane, the electrolyte membrane may deteriorate due to the metal ions. The following embodiment can suppress the deterioration of the electrolyte membrane due to metal ions.

[0013] Figure 1 is a schematic diagram of an electrolytic apparatus 12 equipped with a differential pressure electrolytic stack 14 according to one embodiment. As shown in Figure 1, the electrolytic apparatus 12 includes, for example, a differential pressure electrolytic stack 14, a generated gas outlet passage 16, a back pressure valve 18, a tank 20, and an electrolytic power supply 22.

[0014] The differential pressure electrolytic stack 14 includes a cell stack 24, a pair of end plates 26a and 26b, a supply port 28, an outlet 30, and a generated gas outlet 32. The cell stack 24 is formed by stacking a plurality of differential pressure electrolytic cells 10 on top of each other in the vertical direction.

[0015] A differential pressure electrolytic cell 10 can generate a product gas at a higher pressure than the electrolytic fluid by electrolyzing the electrolytic fluid. For example, the differential pressure electrolytic cell 10 is a water electrolytic cell that can generate oxygen gas (product gas) at a higher pressure than the electrolytic fluid by electrolyzing water (electrolytic fluid). The differential pressure electrolytic cell 10 may also be a hydrogen electrolytic cell (membrane pump) that can generate hydrogen gas (product gas) at a higher pressure than the electrolytic fluid by electrolyzing hydrogen gas (electrolytic fluid).

[0016] A pair of end plates 26a and 26b clamp a plurality of differential-pressure electrolytic cells 10 from above and below. A supply port 28 supplies electrolytic fluid into the cell stack 24. A discharge port 30 discharges the discharge fluid to the outside of the cell stack 24. The discharge fluid includes the fluid from the electrolytic fluid that was not electrolyzed in the differential-pressure electrolytic cells 10. A generated gas outlet 32 ​​guides the generated gas from the differential-pressure electrolytic stack 14 to a generated gas outlet 16. The generated gas outlet 32 ​​is located, for example, in the center of the end plate 26b.

[0017] The generated gas outlet 16 leads the generated gas to the tank 20. The generated gas outlet 16 is equipped with a back pressure valve 18. The back pressure valve 18 opens when the pressure of the generated gas led from the differential pressure electrolytic stack 14 is above a predetermined threshold. The back pressure valve 18 closes when the pressure of the generated gas led from the differential pressure electrolytic stack 14 is below the threshold. The tank 20 is a high-pressure gas tank capable of storing the generated gas. The electrolytic power supply 22 is a DC power supply. The electrolytic power supply 22 is electrically connected to the cell stack 24.

[0018] Figure 2 is a cross-sectional view of the differential pressure electrolytic cell 10. As shown in Figure 2, the differential pressure electrolytic cell 10 is provided with a fluid supply communication hole 34, a fluid discharge communication hole 36, and a generated gas discharge communication hole 38 that penetrate the differential pressure electrolytic cell 10 in the vertical direction. Electrolytic fluid, introduced from the supply port 28 (see Figure 1), flows through the fluid supply communication hole 34. The fluid discharge communication hole 36 guides the discharged fluid to the discharge port 30 (see Figure 1). The generated gas discharge communication hole 38 guides the generated gas to the generated gas outlet 32 ​​(see Figure 1).

[0019] The fluid supply communication hole 34 and the fluid discharge communication hole 36 are provided on the outer periphery of the differential pressure type electrolysis cell 10. The generated gas discharge communication hole 38 is provided in the central portion of the differential pressure type electrolysis cell 10. The generated gas discharge communication hole 38 is located between the fluid supply communication hole 34 and the fluid discharge communication hole 36.

[0020] The differential pressure type electrolysis cell 10 includes a membrane electrode assembly 40, a pair of metal separators 42 and 44, and a frame member 46. The membrane electrode assembly 40 is also referred to as a catalyst-coated membrane (CCM).

[0021] The membrane electrode assembly 40 includes an electrolyte membrane 48, a first electrode catalyst layer 50, and a second electrode catalyst layer 52. The electrolyte membrane 48 is an ion-exchange membrane capable of exchanging ions. For example, the electrolyte membrane 48 is a Proton Exchange Membrane (PEM). The electrolyte membrane 48 may also be an Anion Exchange Membrane (AEM). The first electrode catalyst layer 50 is joined to the lower surface 48a of the electrolyte membrane 48. The second electrode catalyst layer 52 is joined to the upper surface 48b of the electrolyte membrane 48.

[0022] The pair of metal separators 42 and 44 are disposed on both sides of the membrane electrode assembly 40. Each of the metal separators 42 and 44 is made of a metal material such as, for example, stainless steel. The metal material constituting the metal separators 42 and 44 is not limited to stainless steel. Hereinafter, the metal separator 42 positioned below the membrane electrode assembly 40 may be referred to as the "first metal separator 42", and the metal separator 44 positioned above the membrane electrode assembly 40 may be referred to as the "second metal separator 44".

[0023] The frame member 46 surrounds the membrane electrode assembly 40 from the radially outer side. An annular (circular) seal member (rubber seal) 56 for preventing electrolysis fluid and discharged fluid from leaking out to the outside is provided between each of the metal separators 42, 44 and the frame member 46.

[0024] Between the first metal separator 42 and the film electrode assembly 40, a support member 58, a power supply unit 60 (hereinafter sometimes referred to as "first power supply unit 60"), a protective sheet 62, and a first inner circumference member 64 are provided.

[0025] The support member 58 is positioned on the first metal separator 42. The support member 58 is an annular (for example, circular) plate member. The support member 58 has a supply channel 66 that communicates with the fluid supply communication hole 34 and a discharge channel 68 that communicates with the fluid discharge communication hole 36.

[0026] The first power supply unit 60 is formed in an annular shape (for example, a ring shape). The first power supply unit 60 is stacked on top of the support member 58. In other words, the first power supply unit 60 is supported by the support member 58. The first power supply unit 60 has a first fluid flow section 70. The first fluid flow section 70 is made of a porous material. The first fluid flow section 70 guides the electrolytic fluid flowing through the supply channel 66 to the first electrode catalyst layer 50. The first fluid flow section 70 guides the discharge fluid, including fluid not used in the first electrode catalyst layer 50, to the discharge channel 68.

[0027] The protective sheet 62 is formed in an annular shape (for example, a circular shape). The protective sheet 62 is placed on top of the first power supply body 60. The protective sheet 62 is located between the membrane electrode assembly 40 and the first power supply body 60. The protective sheet 62 prevents the membrane electrode assembly 40 from being pressed and damaged by the first power supply body 60. The protective sheet 62 has a plurality of through holes 72 formed therein to allow electrolytic fluid and discharge fluid to flow between the first fluid flow section 70 and the first electrode catalyst layer 50.

[0028] The first inner circumferential member 64 is formed in an annular (ring-shaped) form. The first inner circumferential member 64 extends vertically so as to pass through the inner hole of the support member 58, the inner hole of the first power supply unit 60, and the inner hole of the protective sheet 62. A generated gas discharge communication hole 38 is provided inside the first inner circumferential member 64.

[0029] Between the film electrode assembly 40 and the second metal separator 44, there is a power supply member 74 (hereinafter sometimes referred to as "second power supply member 74"), a resin sheet 76, a conductive sheet 78, a spring member (biasing member) 80, a second inner circumference member 82, a pressure-resistant member 84, and a sealing member 86.

[0030] The second power supply unit 74 is formed in an annular shape (for example, a ring shape). The second power supply unit 74 is superimposed on the membrane electrode assembly 40. When current is supplied (voltage is applied) between the first power supply unit 60 and the second power supply unit 74, the electrolytic fluid supplied to the first electrode catalyst layer 50 is electrolyzed and a product gas is generated in the second electrode catalyst layer 52. The second power supply unit 74 has a second fluid flow section 88. The second fluid flow section 88 is formed of a porous material. The product gas generated in the second electrode catalyst layer 52 flows through the second fluid flow section 88. The outer diameter of the second power supply unit 74 is smaller than the outer diameter of the electrolyte membrane 48.

[0031] The resin sheet 76 is formed in an annular shape (for example, a ring shape). The resin sheet 76 is made of an insulating material. The resin sheet 76 is placed in the inner hole of the second power supply body 74.

[0032] The conductive sheet 78 is formed in an annular shape (for example, a ring shape). The conductive sheet 78 is placed on top of the second power supply 74. The conductive sheet 78 is made of a metal sheet such as titanium or stainless steel. The outer diameter of the conductive sheet 78 is smaller than the outer diameter of the electrolyte membrane 48. In this embodiment, the outer diameter of the conductive sheet 78 is larger than the outer diameter of the second power supply 74, but it may be approximately the same size as the outer diameter of the second power supply 74.

[0033] The spring member 80 is formed in an annular shape (for example, a circular shape). The spring member 80 is placed on top of the conductive sheet 78. The spring member 80 is interposed between the conductive sheet 78 and the second metal separator 44. The spring member 80 presses the conductive sheet 78 toward (downward) the film electrode assembly 40. This allows the second power supply 74 to be brought into close contact with the second electrode catalyst layer 52. A detailed explanation of the configuration of the conductive sheet 78 and the spring member 80 will be given later.

[0034] The second inner circumferential member 82 is formed in an annular (ring-shaped) form. The second inner circumferential member 82 is positioned in the inner hole of the spring member 80. The second inner circumferential member 82 is interposed between the conductive sheet 78 and the second metal separator 44. The second power supply unit 74, the conductive sheet 78, the second inner circumferential member 82, and the second metal separator 44 are electrically connected. The second inner circumferential member 82 has a groove (flow channel) (not shown) formed therein that guides the generated gas to the generated gas discharge communication hole 38.

[0035] The sealing member 86 is a rubber seal (O-ring) positioned between the electrolyte membrane 48 and the second metal separator 44. The sealing member 86 is formed in an annular (circular) shape. The sealing member 86 prevents the generated gas produced in the second electrode catalyst layer 52 from leaking to the outside. Inside the sealing member 86 are the second power supply 74, the conductive sheet 78, and the spring member 80.

[0036] The pressure-resistant member 84 is formed in an annular (circular) shape. The pressure-resistant member 84 is positioned on the outside of the sealing member 86. The inner circumferential surface of the pressure-resistant member 84 is in contact with the sealing member 86. The pressure-resistant member 84 suppresses the radially outward elastic deformation of the sealing member 86. The pressure-resistant member 84 is in contact with the electrolyte membrane 48 and the second metal separator 44.

[0037] Next, the configuration of the spring member 80 and the conductive sheet 78 will be described. Figure 3 is a top view of the spring member 80 in Figure 2, viewed from the direction of arrow III. Figure 4 is a plan view of the conductive sheet 78. Figure 5 is a partially omitted cross-sectional view along line VV in Figure 3. As shown in Figures 2 and 5, in this embodiment, the spring member 80 is a leaf spring, but is not limited to this, and may be a disc spring or the like.

[0038] The spring member 80 is made of a metal material such as stainless steel. The spring member 80 is in contact (line contact) with the lower surface 44a of the second metal separator 44. The spring member 80 and the second metal separator 44 are coated (not shown) to prevent the elution of metal ions (cations).

[0039] As shown in Figures 3 and 5, the spring member 80 has a flat plate portion 92 and a plurality of claw portions 94. The flat plate portion 92 is formed in an annular (circular) shape. The outer diameter of the flat plate portion 92 is smaller than the outer diameter of the electrolyte membrane 48. The outer diameter of the flat plate portion 92 is approximately the same as the outer diameter of the second power supply body 74. The second inner circumferential member 82 is positioned in the inner hole of the flat plate portion 92 (hereinafter sometimes referred to as the "central hole 96").

[0040] As shown in Figure 3, the flat plate portion 92 has a plurality of openings 98 formed therein. The openings 98 are holes that penetrate the flat plate portion 92 in the thickness direction. A claw portion 94 is located in each of the plurality of openings 98. The plurality of openings 98 are spaced apart in the circumferential direction of the flat plate portion 92. The plurality of openings 98 may be spaced apart in the radial direction of the flat plate portion 92.

[0041] The multiple openings 98 have an inner opening group 100 and an outer opening group 102. The inner opening group 100 is formed by arranging the multiple openings 98 at intervals in the circumferential direction of the flat plate portion 92 so as to surround the central hole 96. The inner opening group 100 includes a first inner opening 104 and a second inner opening 106. Each of the first inner opening 104 and the second inner opening 106 is formed in a trapezoidal shape when viewed from above.

[0042] The first inner opening 104 is formed such that its opening width narrows towards the radially outward direction. The second inner opening 106 is formed such that its opening width narrows towards the radially inward direction. The opening width refers to the length of the flat plate portion 92 in the opening 98 in the direction along the circumferential direction. In the inner opening group 100, the first inner opening 104 and the second inner opening 106 are arranged alternately in the circumferential direction of the flat plate portion 92.

[0043] The outer opening group 102 is formed by arranging a plurality of openings 98 at intervals in the circumferential direction of the flat plate portion 92 so as to surround the inner opening group 100. The outer opening group 102 is located radially outward of the flat plate portion 92 than the inner opening group 100. The outer opening group 102 includes a first outer opening 108 and a second outer opening 110. The first outer opening 108 is formed in the same way as the first inner opening 104. The second outer opening 110 is formed in the same way as the second inner opening 106. Therefore, a detailed description of the first outer opening 108 and the second outer opening 110 is omitted. In the outer opening group 102, the first outer opening 108 and the second outer opening 110 are arranged alternately in the circumferential direction of the flat plate portion 92.

[0044] The multiple claw portions 94 have an inner claw portion group 112 and an outer claw portion group 114. The inner claw portion group 112 is formed by claw portions 94 located in the openings 98 that form the inner opening group 100. The inner claw portion group 112 includes a first inner claw portion 116 and a second inner claw portion 118. Each of the first inner claw portion 116 and the second inner claw portion 118 is formed in a trapezoidal shape when viewed from above.

[0045] The first inner claw portion 116 is positioned in the first inner opening 104. The first inner claw portion 116 is formed such that its width (the dimension along the circumferential direction of the flat plate portion 92) narrows towards the radially outward direction of the flat plate portion 92. When viewed from above, the first inner claw portion 116 is formed in a shape that corresponds to the shape of the first inner opening 104. The size of the first inner claw portion 116 is smaller than the size of the first inner opening 104.

[0046] As shown in Figures 3 and 5, the first inner claw portion 116 protrudes from the portion of the flat plate portion 92 that forms the radially inward end of the first inner opening 104, inclined upward radially outward. In other words, the first inner claw portion 116 protrudes from the flat plate portion 92 inclined upward. That is, the root portion 116a of the first inner claw portion 116 is located at the radially inward end of the first inner opening 104. The end of the first inner claw portion 116 in the protruding direction (hereinafter referred to as the "protruding end 116b") is in contact (line contact) with the lower surface 44a of the second metal separator 44. The first inner claw portion 116 extends linearly from the root portion 116a to the protruding end 116b. The first inner claw portion 116 may be curved from the root portion 116a to the protruding end 116b.

[0047] As shown in Figure 3, the second inner claw portion 118 is positioned in the second inner opening 106. The second inner claw portion 118 is formed such that its width narrows towards the radially inward direction of the flat plate portion 92. The second inner claw portion 118 is formed in a shape (trapezoidal) that corresponds to the shape of the second inner opening 106. The size of the second inner claw portion 118 is smaller than the size of the second inner opening 106.

[0048] The second inner claw portion 118 protrudes from the portion of the flat plate portion 92 that forms the radially outward end of the second inner opening 106, inclined upward radially inward. In other words, the second inner claw portion 118 protrudes from the flat plate portion 92 inclined upward. That is, the base portion 118a of the second inner claw portion 118 is located at the radially outward end of the second inner opening 106. The end of the second inner claw portion 118 in the protruding direction (hereinafter referred to as the "protruding end 118b") is in contact (line contact) with the lower surface 44a of the second metal separator 44. The second inner claw portion 118 extends linearly from the base portion 118a to the protruding end 118b. The second inner claw portion 118 may be curved from the base portion 118a to the protruding end 118b. The first inner claw portion 116 and the second inner claw portion 118 are arranged alternately in the circumferential direction of the flat plate portion 92.

[0049] The outer claw group 114 is formed by arranging a plurality of claws 94 at intervals in the circumferential direction of the flat plate portion 92 so as to surround the inner claw group 112. The outer claw group 114 is located radially outward of the flat plate portion 92 than the inner claw group 112. The outer claw group 114 includes a first outer claw portion 120 and a second outer claw portion 122. The first outer claw portion 120 is formed in the same manner as the first inner claw portion 116. The second outer claw portion 122 is formed in the same manner as the second inner claw portion 118.

[0050] The base portion 120a of the first outer claw portion 120 is located at the radially inward end of the first outer opening 108. The protruding end of the first outer claw portion 120 (hereinafter referred to as the "protruding end 120b") is in contact (line contact) with the lower surface 44a of the second metal separator 44. The base portion 122a of the second outer claw portion 122 is located at the radially outward end of the second outer opening 110. The protruding end of the second outer claw portion 122 (hereinafter referred to as the "protruding end 122b") is in contact (line contact) with the lower surface 44a of the second metal separator 44. The first outer claw portion 120 and the second outer claw portion 122 are arranged alternately in the circumferential direction of the flat plate portion 92.

[0051] As shown in Figures 2 and 5, the conductive sheet 78 is located below the spring member 80. The outer diameter of the conductive sheet 78 is larger than the outer diameter of the spring member 80 (flat plate portion 92).

[0052] As shown in Figures 3 to 5, a capturing member 124 capable of capturing cations (metal ions) is provided on the outer periphery of the conductive sheet 78. An annular (circular) outer recess 126 for accommodating the capturing member 124 is formed on the upper surface 78a of the conductive sheet 78. This allows water (water containing metal ions) that flows down from the spring member 80 to be stored in the outer recess 126, making it easier for the water containing metal ions to come into contact with the capturing member 124. The outer recess 126 is located radially outward from the spring member 80 (see Figure 3).

[0053] The capture member 124 is, for example, an ion exchange resin (cation exchange resin). The capture member 124 is not limited to an ion exchange resin, but may be an adsorption member (for example, activated carbon) capable of adsorbing cations (metal ions). The capture member 124 is formed in an annular (circular) shape. This ensures that water containing metal ions can be reliably brought into contact with the capture member 124.

[0054] The capture member 124 is attached to a detachable holder 128 on the outer circumference of the conductive sheet 78. With this configuration, a deteriorated capture member 124 can be easily replaced. This makes it easy to maintain the differential pressure electrolytic cell 10.

[0055] The holder 128 is formed in an annular (circular) shape. The holder 128 may be divided into multiple parts in the circumferential direction, for example. In this case, it is preferable that the capturing member 124 is also divided in accordance with the division structure of the holder 128. This makes it easier to attach and detach the holder 128 to the conductive sheet 78 compared to when the holder 128 is formed as a single annular piece. The structure for attaching and detaching the holder 128 to the outer circumference of the conductive sheet 78 can be, for example, a fitting structure, but can be set as appropriate.

[0056] As shown in Figure 5, a lubricating member 129 is interposed between the capturing member 124 and the conductive sheet 78. This makes it easier to remove the capturing member 124 from the conductive sheet 78, thus simplifying the replacement of the capturing member 124. The lubricating member 129 is formed in an annular (circular) shape. The lubricating member 129 is made of a fluororesin with relatively good sliding properties, such as polytetrafluoroethylene (PTFE). The lubricating member 129 is attached to the holder 128. The holder 128 and the lubricating member 129 may be integrally molded from, for example, a resin material.

[0057] As shown in Figures 3 to 5, guide grooves 130 are formed on the upper surface 78a of the conductive sheet 78 to guide the water that flows from the spring member 80 onto the conductive sheet 78 to the outer peripheral recess 126. This allows the water that flows from the spring member 80 onto the conductive sheet 78 to flow smoothly to the outer peripheral recess 126 via the guide grooves 130.

[0058] The guide groove 130 includes a plurality of annular grooves 132 and a plurality of radial grooves 134. Each annular groove 132 is formed in an annular shape. The plurality of annular grooves 132 are located below the plurality of claw portions 94. This allows the water flowing down from the plurality of claw portions 94 to be received by the annular grooves 132.

[0059] The groove width of each annular groove 132 can be set as appropriate. In this embodiment, the multiple annular grooves 132 include a first annular groove 136, a second annular groove 138, a third annular groove 140, and a fourth annular groove 142.

[0060] As shown in Figure 3, the first annular groove 136 and the second annular groove 138 are located below the inner claw group 112. The first annular groove 136 is located below the root portion 116a of the multiple first inner claw portions 116. The second annular groove 138 is located below the root portion 118a of the multiple second inner claw portions 118. The third annular groove 140 and the fourth annular groove 142 are located below the outer claw group 114. The third annular groove 140 is located below the root portion 120a of the multiple first outer claw portions 120. The fourth annular groove 142 is located below the root portion 122a of the multiple second outer claw portions 122. The number, position, size, shape, etc. of the annular grooves 132 can be set as appropriate.

[0061] As shown in Figure 4, the multiple radial grooves 134 are arranged at intervals in the circumferential direction of the conductive sheet 78. In this embodiment, eight radial grooves 134 are formed on the upper surface 78a of the conductive sheet 78. Each radial groove 134 extends along the radial direction of the conductive sheet 78. This allows the radial grooves 134 to quickly guide water that has flowed from the spring member 80 onto the conductive sheet 78 to the outer peripheral recess 126.

[0062] As shown in Figure 5, the radial grooves 134 are formed such that their depth increases towards the radially outward direction of the conductive sheet 78. In this case, water in the radial grooves 134 flows more easily into the outer peripheral recesses 126. Each radial groove 134 is connected to a plurality of annular grooves 132 (see Figure 4). This allows water received in the annular grooves 132 to flow into the radial grooves 134.

[0063] Specifically, the radial groove 134 includes a first groove 134a, a second groove 134b, a third groove 134c, and a fourth groove 134d. The first groove 134a extends to connect the first annular groove 136 and the second annular groove 138. The second groove 134b extends to connect the second annular groove 138 and the third annular groove 140. The groove depth of the second groove 134b is deeper than that of the first groove 134a. The third groove 134c extends to connect the third annular groove 140 and the fourth annular groove 142. The groove depth of the third groove 134c is deeper than that of the second groove 134b. The fourth groove 134d extends to connect the fourth groove 134d and the outer peripheral recess 126. The groove depth of the fourth groove 134d is deeper than the groove depth of the third groove 134c. Furthermore, the depth of the outer peripheral recess 126 is deeper than the groove depth of the fourth groove 134d.

[0064] The bottom surfaces of the first groove 134a, second groove 134b, third groove 134c, and fourth groove 134d are horizontal, but may also be inclined surfaces that slope downward toward the radially outward direction. By adopting such inclined surfaces, water (liquid water) in the radial groove 134 can be guided more smoothly to the outer peripheral recess 126. Furthermore, the bottom surfaces of the radial grooves 134 are not limited to examples where they are formed in a stepped shape, but may also be inclined surfaces that slope downward continuously from the first annular groove 136 to the outer peripheral recess 126. The number, position, size, shape, etc. of the radial grooves 134 can be set as appropriate.

[0065] Next, we will briefly explain the basic operation of the differential pressure electrolytic stack 14. Here, we will explain using a differential pressure electrolytic stack 14 that generates oxygen gas and hydrogen gas by electrolyzing water as an example.

[0066] As shown in Figures 1 and 2, a water pump (not shown) supplies water (electrolytic fluid) to the supply port 28 of the differential pressure electrolytic stack 14, and an electrolytic power supply 22 supplies current to the first power supply 60 and the second power supply 74 of each differential pressure electrolytic cell 10. The water supplied to the supply port 28 is guided to the first electrode catalyst layer 50 via the fluid supply communication hole 34 and the supply channel 66.

[0067] In this case, water is electrolyzed in the membrane electrode assembly 40 to generate hydrogen gas in the first electrode catalyst layer 50 and oxygen gas in the second electrode catalyst layer 52. The discharge fluid, which includes the hydrogen gas generated in the first electrode catalyst layer 50 and the water that was not electrolyzed, is discharged to the outside of the differential pressure electrolytic stack 14 through the discharge channel 68, the fluid discharge communication hole 36, and the discharge port 30. The oxygen gas generated in the second electrode catalyst layer 52 is guided to the generated gas discharge communication hole 38 through the space between the membrane electrode assembly 40 and the second metal separator 44 (hereinafter sometimes referred to as the "generated gas containment chamber 144") and a groove (not shown) in the second inner circumferential member 82. The oxygen gas guided to the generated gas discharge communication hole 38 is led out to the generated gas outlet 16 from the generated gas outlet 32.

[0068] A back pressure valve 18 is provided in the generated gas outlet passage 16. Therefore, the oxygen gas generated in the second electrode catalyst layer 52 is sealed by the back pressure valve 18. This makes it possible to raise the pressure of the oxygen gas (generated gas) generated in the second electrode catalyst layer 52 to a higher pressure than the water (electrolytic fluid) supplied to the first electrode catalyst layer 50. In other words, the pressure of the oxygen gas in the generated gas containment chamber 144 becomes higher than the pressure of the water supplied to the first electrode catalyst layer 50. Subsequently, the back pressure valve 18 opens, and the tank 20 is filled with high-pressure oxygen gas.

[0069] In this embodiment, the spring member 80 is in line contact with the lower surface 44a of the second metal separator 44. Therefore, the coating is prone to peeling off at the contact point between the second metal separator 44 and the spring member 80. Furthermore, when oxygen gas is generated in the second electrode catalyst layer 52, the exposed metal portion is prone to corrosion, and metal ions are easily eluted from the exposed metal portion. Metal ions can also be eluted from the exposed metal portion when hydrogen gas is generated in the second electrode catalyst layer 52. Moreover, when water supplied to the first electrode catalyst layer 50 permeates the electrolyte membrane 48 and is guided to the second electrode catalyst layer 52, the humidity inside the generated gas containment chamber 144 tends to increase, making it easier for the water to condense on the second metal separator 44 and the spring member 80, etc.

[0070] Water droplets containing metal ions flow downward along the claw portion 94 of the spring member 80. Specifically, water droplets adhering to the protruding end 116b of the first inner claw portion 116 flow along the first inner claw portion 116 to the base portion 116a of the first inner claw portion 116, and then are guided into the first annular groove 136. Water droplets adhering to the protruding end 120b of the first outer claw portion 120 flow along the first outer claw portion 120 to the base portion 120a of the first outer claw portion 120, and then are guided into the third annular groove 140. Water droplets adhering to the protruding end 118b of the second inner claw portion 118 flow along the second inner claw portion 118 to the base portion 118a of the second inner claw portion 118, and then are guided into the second annular groove 138. Water droplets adhering to the protruding end 122b of the second outer claw portion 122 flow along the second outer claw portion 122 to the base portion 122a of the second outer claw portion 122, and then are guided into the fourth annular groove 142.

[0071] Water guided into the first annular groove 136, the second annular groove 138, the third annular groove 140, and the fourth annular groove 142 flows through a plurality of radial grooves 134 to the outer peripheral recess 126. The water that flows into the outer peripheral recess 126 comes into contact with the capture member 124, thereby capturing (removing) the metal ions (cations) contained in the water. Therefore, even if the water from which the metal ions have been removed flows downward and comes into contact with the electrolyte membrane 48, deterioration of the electrolyte membrane 48 can be suppressed.

[0072] In other words, according to this embodiment, water (water containing metal ions) that flows down from the exposed metal portion of the second metal separator 44 and the spring member 80 onto the upper surface 78a of the conductive sheet 78 can be brought into contact with the capture member 124 at the outer periphery of the conductive sheet 78. This allows the metal ions to be captured (removed) by the capture member 124 before the water containing metal ions flows down onto the electrolyte membrane 48. Therefore, deterioration of the electrolyte membrane 48 due to metal ions can be suppressed. In short, such a configuration can provide a better differential pressure electrolytic cell 10 and differential pressure electrolytic stack 14.

[0073] This embodiment is not limited to the configuration described above. For example, as shown in Figure 6, the radial groove 134 may be formed with a constant groove depth extending radially outward from the conductive sheet 78. That is, the radial groove 134 may extend along a horizontal plane.

[0074] The following additional information is disclosed regarding the above embodiments.

[0075] (Note 1) The differential pressure electrolytic cell (10) of the present disclosure comprises a membrane electrode assembly (40) having an electrolyte membrane (48) and a first electrode catalyst layer (50) and a second electrode catalyst layer (52) joined to both sides of the electrolyte membrane, and is capable of generating a product gas at a pressure higher than the electrolytic fluid in the second electrode catalyst layer by electrolysis of an electrolytic fluid supplied to the first electrode catalyst layer, and comprises a metal separator (44) disposed above the second electrode catalyst layer, a conductive sheet (78) disposed on a power supply (74) located between the metal separator and the second electrode catalyst layer, and a metal spring member (80) that contacts the metal separator and the conductive sheet and presses the conductive sheet downward, and a capture member (124) capable of capturing cations is provided on the outer periphery of the conductive sheet.

[0076] With this configuration, water (water containing metal ions) that flows from the exposed metal portions of the metal separator and spring member onto the upper surface of the conductive sheet can be brought into contact with the capture member at the outer periphery of the conductive sheet. This allows the metal ions to be captured (removed) by the capture member before the water containing metal ions flows onto the electrolyte membrane. Therefore, degradation of the electrolyte membrane due to metal ions can be suppressed. In other words, this configuration can provide a better differential pressure electrolytic cell.

[0077] (Note 2) The differential pressure electrolytic cell described in Appendix 1 may have an annular outer peripheral recess (126) formed on the upper surface (78a) of the conductive sheet for accommodating the capture member.

[0078] With this configuration, water containing metal ions can be stored in the recesses on the outer periphery, making it easier to bring the water containing metal ions into contact with the capturing member.

[0079] (Note 3) In the differential pressure electrolytic cell described in Appendix 2, the capture member may be formed in an annular shape.

[0080] With this configuration, water containing metal ions can be reliably brought into contact with the capturing member.

[0081] (Note 4) A differential pressure electrolytic cell as described in Appendix 2 or 3, wherein a guide groove (130) is formed on the upper surface of the conductive sheet to guide the water that flows from the spring member onto the conductive sheet into the outer peripheral recess.

[0082] With this configuration, the guide groove allows water that has flowed from the spring member onto the conductive sheet to flow smoothly into the outer recess.

[0083] (Note 5) The differential pressure electrolytic cell described in Appendix 4 may include a radial groove (134) extending along the radial direction of the conductive sheet.

[0084] With this configuration, the radial grooves allow water that has flowed from the spring member onto the conductive sheet to be quickly guided to the outer recess.

[0085] (Note 6) In the differential pressure electrolytic cell described in Appendix 5, the radial groove may be formed such that the groove depth of the radial groove increases toward the radially outward direction of the conductive sheet.

[0086] With this configuration, water in the radial grooves flows more easily into the outer recesses.

[0087] (Note 7) A differential pressure electrolytic cell as described in Appendix 5 or 6, wherein the spring member has a flat plate portion (92) and a claw portion (94) that protrudes from the flat plate portion so as to be inclined upward and contacts the metal separator, and the guide groove may be located below the claw portion.

[0088] With this configuration, water flowing down the claw portion can be received by the guide groove.

[0089] (Note 8) The differential pressure electrolytic cell described in Appendix 7, wherein the claw portions are arranged in a plurality at intervals along the circumferential direction of the flat plate portion, and the guide groove may include an annular groove (132) located below the plurality of claw portions arranged along the circumferential direction of the flat plate portion and communicating with the radial groove.

[0090] With this configuration, water flowing down from multiple claw sections can be received by the annular groove. Furthermore, the water received by the annular groove can be directed into the radial groove.

[0091] (Note 9) A differential pressure electrolytic cell as described in any one of appendices 1 to 8, wherein the conductive sheet has a detachable holder (128) on its outer circumference, and the capturing member may be attached to the holder.

[0092] This configuration allows for easy replacement of deteriorated capture components. This facilitates maintenance of differential pressure electrolytic cells.

[0093] (Note 10) In the differential pressure electrolytic cell described in Appendix 9, a lubricating member (129) may be interposed between the capturing member and the conductive sheet.

[0094] With this configuration, the capturing member can be easily removed from the conductive sheet, making it even easier to replace the capturing member.

[0095] (Note 11) The differential pressure electrolytic stack (14) of this disclosure is a differential pressure electrolytic stack in which multiple differential pressure electrolytic cells described in any one of appendices 1 to 10 are stacked.

[0096] With this configuration, a differential pressure electrolytic stack that exhibits the effects described in any one of the appendices 1 to 10 can be obtained. In other words, a better differential pressure electrolytic stack can be obtained.

[0097] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the spirit of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above. [Explanation of Symbols]

[0098] 10... Differential pressure electrolytic cell 14... Differential pressure electrolytic stack 40…Membrane electrode assembly 42…First metal separator 44…Second metal separator (metal separator) 48... Electrolyte membrane 50... First electrode catalyst layer 52...Second electrode catalyst layer 60...First power supply body 74...Second power supply unit (power supply unit) 78...Conductive sheet 78a...Top surface of conductive sheet 80...Spring member 92...Flat plate part 94...Claw part 124...Capture member 126...Peripheral recess 128...Holder 129...Lubricant 130... Guide groove 132... Ring groove 134...Radial groove

Claims

1. A differential pressure electrolytic cell comprising a membrane electrode assembly having an electrolyte membrane and a first electrode catalyst layer and a second electrode catalyst layer bonded to both sides of the electrolyte membrane, wherein the electrolytic fluid supplied to the first electrode catalyst layer is electrolyzed to generate a product gas at a pressure higher than that of the electrolytic fluid in the second electrode catalyst layer, A metal separator positioned above the second electrode catalyst layer, A conductive sheet is placed on the power supply unit located between the metal separator and the second electrode catalyst layer, A metal spring member that contacts the metal separator and the conductive sheet and presses the conductive sheet downwards, Equipped with, A differential pressure electrolytic cell is provided on the outer periphery of the conductive sheet, wherein a capturing member capable of capturing cations is provided.

2. A differential pressure electrolytic cell according to claim 1, A differential pressure electrolytic cell, wherein an annular outer recess for accommodating the capture member is formed on the upper surface of the conductive sheet.

3. A differential pressure electrolytic cell according to claim 2, The aforementioned capture member is a differential pressure electrolytic cell formed in an annular shape.

4. A differential pressure electrolytic cell according to claim 2, A differential pressure electrolytic cell, wherein a guide groove is formed on the upper surface of the conductive sheet to guide water that flows from the spring member onto the conductive sheet into the outer peripheral recess.

5. A differential pressure electrolytic cell according to claim 4, A differential pressure electrolytic cell, wherein the guide groove includes a radial groove extending along the radial direction of the conductive sheet.

6. A differential pressure electrolytic cell according to claim 5, A differential pressure electrolytic cell, wherein the radial groove is formed such that the groove depth of the radial groove increases toward the radially outward direction of the conductive sheet.

7. A differential pressure electrolytic cell according to claim 5, The aforementioned spring member is Flat section and A claw portion that protrudes from the flat plate portion so as to be inclined upward and contacts the metal separator, It has, The guide groove is located below the claw portion, and is a differential pressure electrolytic cell.

8. A differential pressure electrolytic cell according to claim 7, Multiple claw portions are arranged at intervals along the circumferential direction of the flat plate portion. A differential pressure electrolytic cell, wherein the guide groove is located below a plurality of claw portions arranged along the circumferential direction of the flat plate portion and includes an annular groove that communicates with the radial groove.

9. A differential pressure electrolytic cell according to claim 1, The conductive sheet has a detachable holder on its outer periphery, The capture member is a differential pressure electrolytic cell attached to the holder.

10. A differential pressure electrolytic cell according to claim 9, A differential pressure electrolytic cell in which a lubricating member is interposed between the capturing member and the conductive sheet.

11. A differential pressure electrolytic stack comprising a plurality of differential pressure electrolytic cells according to any one of claims 1 to 10.

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