Differential pressure electrolysis cell and differential pressure electrolysis stack

Abstract

A differential pressure electrolysis cell includes: a metal separator disposed above a second electrode catalyst layer, a conductive sheet disposed on a current collector arranged between the metal separator and the second electrode catalyst layer; a metal spring member in contact with the metal separator and the conductive sheet to press the conductive sheet downward; and a capturing member provided on an outer circumferential portion of the conductive sheet to capture cations.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2025-027922 filed on Feb. 25, 2025, the contents of which are incorporated herein by reference.BACKGROUND OF THE INVENTIONField of the Invention

[0002] The present disclosure relates to a differential pressure electrolysis cell and a differential pressure electrolysis stack.Description of the Related Art

[0003] In recent years, research and development have been conducted on differential pressure electrolysis stacks that contribute to energy efficiency in order to ensure that more people have access to affordable, reliable, sustainable and modern energy.

[0004] JP 7037965 B2 discloses a configuration of a differential pressure electrolysis cell of a differential pressure electrolysis stack.SUMMARY OF THE INVENTION

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

[0006] The present disclosure has the object of solving the aforementioned problem.

[0007] A first aspect of the present disclosure is characterized by a differential pressure electrolysis cell configured to electrolyze an electrolysis fluid supplied to a first electrode catalyst layer to generate a product gas in a second electrode catalyst layer, the product gas having a higher pressure than the electrolysis fluid, the differential pressure electrolysis cell including: a membrane electrode assembly including an electrolyte membrane, the first electrode catalyst layer and the second electrode catalyst layer, the first electrode catalyst layer and the second electrode catalyst layer being joined to opposite sides of the electrolyte membrane; a metal separator arranged above the second electrode catalyst layer; a conductive sheet disposed on a current collector positioned between the metal separator and the second electrode catalyst layer; a spring member made of metal, in contact with the metal separator and the conductive sheet, and configured to press the conductive sheet downward; and a capturing member provided on an outer circumferential portion of the conductive sheet and configured to capture cations.

[0008] A second aspect of the present disclosure is characterized by a differential pressure electrolysis stack in which a plurality of the differential pressure electrolysis cells described above are stacked.

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

[0010] The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a schematic view of an electrolysis apparatus including a differential pressure electrolysis stack according to an embodiment;

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

[0013] FIG. 3 is a top view of a spring member shown in FIG. 2 as viewed from the arrow III direction;

[0014] FIG. 4 is a plan view of a conductive sheet;

[0015] FIG. 5 is a partially omitted cross-sectional view taken along line V-V of FIG. 3; and

[0016] FIG. 6 is a partially omitted cross-sectional view illustrating a modification of a radial groove.DETAILED DESCRIPTION OF THE INVENTION

[0017] A differential pressure electrolysis cell can electrolyze an electrolysis fluid supplied to a first electrode catalyst layer of a membrane electrode assembly to generate a product gas at a pressure higher than the electrolysis fluid in a second electrode catalyst layer of the membrane electrode assembly. In this type of differential pressure electrolysis cell, a metal separator is disposed above the second electrode catalyst layer. A spring member made of metal is arranged between the metal separator and the second electrode catalyst layer, for pressing a current collector toward the second electrode catalyst layer. The metal separator and the spring member are coated, for example, to prevent elution of metal ions (cations).

[0018] However, the coating may peel off from a position at which the spring member contacts the metal separator. In addition, the coating may peel off due to aging deterioration. When water droplets adhere to a portion at which the coating has been peeled off and metal is exposed, metal ions may be eluted. When the water containing the metal ions flows downward from the spring member and contacts the electrolyte membrane, the electrolyte membrane may be deteriorated by the metal ions. According to the aspects described below, the deterioration of the electrolyte membrane due to metal ions can be suppressed.

[0019] FIG. 1 is a schematic view of an electrolysis apparatus 12 including a differential pressure electrolysis stack 14 according to an embodiment. As shown in FIG. 1, the electrolysis apparatus 12 includes, for example, a differential pressure electrolysis stack 14, a product gas lead-out path 16, a back pressure valve 18, a tank 20, and an electrolytic power supply 22.

[0020] The differential pressure electrolysis stack 14 includes a cell stack body 24, a pair of end plates 26a, 26b, a fluid inlet 28, a fluid outlet 30, and a product gas outlet 32. The cell stack body 24 is formed by stacking a plurality of differential pressure electrolysis cells 10 in the up-down direction.

[0021] A differential pressure electrolysis cell 10 can electrolyze an electrolysis fluid to generate a product gas at a pressure higher than the electrolysis fluid. A differential pressure electrolysis cell 10 is a water electrolysis cell capable of electrolyzing water (electrolysis fluid) to generate an oxygen gas (product gas) at a pressure higher than the electrolysis fluid. A differential pressure electrolysis cell 10 may be a hydrogen electrolysis cell (electrochemical hydrogen compressor) capable of electrolyzing a hydrogen gas (electrolysis fluid) to generate a hydrogen gas (product gas) at a pressure higher than the electrolysis fluid.

[0022] The pair of end plates 26a, 26b sandwich the plurality of differential pressure electrolysis cells 10 in the up-down direction. An electrolysis fluid is supplied to the inside of the cell stack body 24 through the fluid inlet 28. A fluid is discharged to the outside of the cell stack body 24 through the fluid outlet 30. The fluid to be discharged includes a remainder of the electrolysis fluid that is not electrolyzed in the differential pressure electrolysis cell 10. The product gas outlet 32 guides the product gas from the differential pressure electrolysis stack 14 to the product gas lead-out path 16. The product gas outlet 32 is provided, for example, in the central portion of the end plate 26b.

[0023] The product gas lead-out path 16 guides the product gas to the tank 20. The product gas lead-out path 16 is provided with the back pressure valve 18. The back pressure valve 18 opens in the case where the pressure of the product gas guided from the differential pressure electrolysis stack 14 is equal to or higher than a predetermined threshold. The back pressure valve 18 closes in the case where the pressure of the product gas guided from the differential pressure electrolysis stack 14 is less than the threshold. The tank 20 is a high pressure gas tank that can store the product gas. The electrolytic power supply 22 is a direct-current power source. The electrolytic power supply 22 is electrically connected to the cell stack 24.

[0024] FIG. 2 is a cross-sectional view of the differential pressure electrolysis cell 10. As shown in FIG. 2, the differential pressure electrolysis cell 10 is provided with a fluid supply passage 34, a fluid discharge passage 36, and a product gas discharge passage 38 that extend through the differential pressure electrolysis cell 10 in the up-down direction. The electrolysis fluid guided from the fluid inlet 28 (see FIG. 1) flows through the fluid supply passage 34. The fluid discharge passage 36 guides the fluid to be discharged from the fluid outlet 30 (see FIG. 1). The product gas discharge passage 38 guides the product gas to the product gas outlet 32 (see FIG. 1).

[0025] The fluid supply passage 34 and the fluid discharge passage 36 are provided in the outer peripheral portion of the differential pressure electrolysis cell 10. The product gas discharge passage 38 is provided in the central portion of the differential pressure electrolysis cell 10. The product gas discharge passage 38 is positioned between the fluid supply passage 34 and the fluid discharge passage 36.

[0026] The differential pressure electrolysis cell 10 includes a membrane electrode assembly 40, a pair of metal separators 42, 44, and a frame member 46. The membrane electrode assembly 40 is also referred to as an electrolyte membrane with catalyst layers (CCM: Catalyst-Coated Membrane).

[0027] 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 that is capable of exchanging ions. The electrolyte membrane 48, for example, is a proton exchange membrane (PEM). The electrolyte membrane 48 may be an anion exchange membrane (AEM). The first electrode catalyst layer 50 is bonded to a lower surface 48a of the electrolyte membrane 48. The second electrode catalyst layer 52 is bonded to an upper surface 48b of the electrolyte membrane 48.

[0028] The pair of metal separators 42, 44 are disposed on opposite sides of the membrane electrode assembly 40. The metal separators 42, 44 are made of a metal material such as stainless steel. The metal material constituting the metal separators 42, 44 is not limited to stainless steel. Hereinafter, the metal separator 42 arranged below the membrane electrode assembly 40 may be referred to as a “first metal separator 42”, and the metal separator 44 arranged above the membrane electrode assembly 40 may be referred to as a “second metal separator 44”.

[0029] The frame member 46 surrounds the membrane electrode assembly 40 from the radially outer side. Surrounding (annular) seal members (rubber seals) 56 are provided between the frame member 46 and each of the metal separators 42, 44 to prevent the electrolysis fluid from flowing to the outside before or after electrolysis.

[0030] Between the first metal separator 42 and the membrane electrode assembly 40, a support member 58, a current collector 60 (hereinafter referred to also as the first current collector 60), a protective sheet 62, and a first inner peripheral member 64 are provided.

[0031] The support member 58 is disposed on the first metal separator 42. The support member 58 is a plate member having a closed-loop perimeter (for example, an annular shape). A supply flow path 66 in communication with the fluid supply passage 34 and a discharge flow path 68 in communication with the fluid discharge passage 36 are formed in the support member 58.

[0032] The first current collector 60 has a closed-loop perimeter (for example, an annular shape). The first current collector 60 is stacked on the support member 58. In other words, the first current collector 60 is supported by the support member 58. The first current collector 60 includes a first fluid distribution section 70. The first fluid distribution section 70 is formed of a porous material. The first fluid distribution section 70 guides the electrolysis fluid flowing through the supply flow path 66 to the first electrode catalyst layer 50. The fluid to be discharged, containing the remainder of the electrolysis fluid that has not been consumed in the first electrode catalyst layer 50, is guided to the discharge flow path 68 through the first fluid distribution section 70.

[0033] The protective sheet 62 has a closed-loop perimeter (for example, an annular shape). The protective sheet 62 is stacked on the first current collector 60. The protective sheet 62 is positioned between the membrane electrode assembly 40 and the first current collector 60. The protective sheet 62 prevents the membrane electrode assembly 40 from being damaged by being pressed by the first current collector 60. The protective sheet 62 has a plurality of through holes 72 for allowing the electrolysis fluid and the fluid to be discharged to flow between the first fluid distribution section 70 and the first electrode catalyst layer 50.

[0034] The first inner peripheral member 64 has a closed-loop perimeter (for example, an annular shape). The first inner peripheral member 64 extends in the up-down direction so as to be inserted through the inner hole of the support member 58, the inner hole of the first current collector 60, and the inner hole of the protective sheet 62. The product gas discharge passage 38 is provided inside the first inner peripheral member 64.

[0035] Between the membrane electrode assembly 40 and the second metal separator 44, a current collector 74 (hereinafter, may be referred to as “second current collector 74”), a resin sheet 76, a conductive sheet 78, a spring member (biasing member) 80, a second inner peripheral member 82, a pressure-resistant member 84, and a seal member 86 are provided.

[0036] The second current collector 74 has a closed-loop perimeter (for example, an annular shape). The second current collector 74 is stacked on the membrane electrode assembly 40. When a current is supplied (a voltage is applied) between the first current collector 60 and the second current collector 74, the electrolysis 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 current collector 74 includes a second fluid distribution section 88. The second fluid distribution section 88 is formed of a porous material. The product gas generated in the second electrode catalyst layer 52 flows through the second fluid distribution section 88. The outer diameter of the second current collector 74 is smaller than the outer diameter of the electrolyte membrane 48.

[0037] The resin sheet 76 has a closed-loop perimeter (for example, an annular shape). The resin sheet 76 is made of an insulating material. The resin sheet 76 is disposed in the inner hole of the second current collector 74.

[0038] The conductive sheet 78 has a closed-loop perimeter (for example, an annular shape). The conductive sheet 78 is stacked on the second current collector 74. The conductive sheet 78 is made of metal 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 the present embodiment, the outer diameter of the conductive sheet 78 is larger than the outer diameter of the second current collector 74, but may be substantially the same as the outer diameter of the second current collector 74.

[0039] The spring member 80 has a closed-loop perimeter (for example, an annular shape). The spring member 80 is stacked on 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 the membrane electrode assembly 40 (downward). This allows the second current collector 74 to be in close contact with the second electrode catalyst layer 52. The details of the conductive sheet 78 and the spring member 80 will be described later.

[0040] The second inner peripheral member 82 has a closed-loop perimeter (for example, an annular shape). The second inner peripheral member 82 is disposed in the inner hole of the spring member 80. The second inner peripheral member 82 is interposed between the conductive sheet 78 and the second metal separator 44. The second current collector 74, the conductive sheet 78, the second inner peripheral member 82, and the second metal separator 44 are electrically connected to each other. The second inner peripheral member 82 has grooves (flow channels) (not shown) for guiding the product gas to the product gas discharge passage 38.

[0041] The seal member 86 is a rubber seal (O-ring) disposed between the electrolyte membrane 48 and the second metal separator 44. The seal member 86 has a closed-loop perimeter (for example, an annular shape). The seal member 86 prevents the product gas produced in the second electrode catalyst layer 52 from leaking to the outside. The seal member 86 surrounds the second current collector 74, the conductive sheet 78, and the spring member 80.

[0042] The pressure-resistant member 84 has a closed-loop perimeter (for example, an annular shape). The pressure-resistant member 84 is disposed on the outer side of the seal member 86. The inner circumferential surface of the pressure-resistant member 84 is in contact with the seal member 86. The pressure-resistant member 84 suppresses radially outward elastic deformation of the seal member 86. The pressure-resistant member 84 is in contact with the electrolyte membrane 48 and the second metal separator 44.

[0043] Next, a description will be made concerning the configurations of the spring member 80 and the conductive sheet 78. FIG. 3 is a top view of the spring member 80 shown in FIG. 2 as viewed from the arrow III direction. FIG. 4 is a plan view of the conductive sheet 78. FIG. 5 is a partially omitted cross-sectional view taken along line V-V of FIG. 3. As shown in FIGS. 2 and 5, in the present embodiment, the spring member 80 is a plate spring, but is not limited thereto, and may be, for example, a disc spring or the like.

[0044] The spring member 80 is made of metal 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 with a coating (not shown) to prevent elution of metal ions (cations).

[0045] As shown in FIGS. 3 and 5, the spring member 80 has a flat plate portion 92 and a plurality of claws 94. The flat plate portion 92 has a closed-loop perimeter (for example, an annular 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 substantially the same as the outer diameter of the second current collector 74. The second inner peripheral member 82 is disposed in the inner hole of the flat plate portion 92 (hereinafter may be referred to as “center hole 96”).

[0046] As shown in FIG. 3, a plurality of openings 98 are formed in the flat plate portion 92. The openings 98 are holes penetrating the flat plate portion 92 in the thickness direction. The claws 94 are respectively located at each of the plurality of openings 98. The plurality of openings 98 are arranged at intervals in the circumferential direction of the flat plate portion 92. The plurality of openings 98 may be arranged at intervals in the radial direction of the flat plate portion 92.

[0047] The plurality of openings 98 includes an inner opening group 100 and an outer opening group 102. The inner opening group 100 is formed by arranging the plurality of openings 98 at intervals in the circumferential direction of the flat plate portion 92 so as to surround the center hole 96. The inner opening group 100 includes first inner openings 104 and second inner openings 106. Each of first inner openings 104 and second inner openings 106 is formed in a trapezoidal shape when viewed from above.

[0048] The first inner opening 104 is formed such that the width between ends thereof in the circumferential direction becomes narrower radially outward. The second inner opening 106 is formed such that the width between ends thereof in the circumferential direction becomes narrower radially inward. The width refers to the length between the ends of the opening 98 in the direction along the circumferential direction of the flat plate portion 92. In the inner opening group 100, the first inner openings 104 and the second inner openings 106 are alternately arranged in the circumferential direction of the flat plate portion 92.

[0049] The outer opening group 102 is formed by arranging the 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 positioned radially outward of the inner opening group 100 in the flat plate portion 92. The outer opening group 102 includes first outer openings 108 and second outer openings 110. The first outer opening 108 is formed in the same manner as the first inner opening 104. The second outer opening 110 is formed in the same manner as the second inner opening 106. Therefore, the detailed descriptions of the first outer opening 108 and the second outer opening 110 are omitted. In the outer opening group 102, the first outer openings 108 and the second outer openings 110 are alternately arranged in the circumferential direction of the flat plate portion 92.

[0050] The plurality of claws 94 include an inner claw group 112 and an outer claw group 114. The inner claw group 112 is formed by the claws 94 located at the openings 98 forming the inner opening group 100. The inner claw group 112 includes first inner claws 116 and second inner claws 118. Each of first inner claws 116 and second inner claws 118 is formed in a trapezoidal shape when viewed from above.

[0051] The first inner claws 116 are arranged at the first inner openings 104. The first inner claw 116 is formed such that the lateral width (the dimension along the circumferential direction of the flat plate portion 92) becomes narrower radially outward in the flat plate portion 92. The first inner claw 116 is formed in a shape corresponding to the shape of the first inner opening 104 when viewed from above. The size of the first inner claw 116 is smaller than the size of the contour of the first inner opening 104.

[0052] As shown in FIGS. 3 and 5, the first inner claw 116 protrudes upward from the flat plate portion 92 and is inclined radially outward from the inner ends of the first inner opening 104. In other words, the first inner claw 116 is inclined upward from the flat plate portion 92. That is, a root 116a of the first inner claw 116 is positioned between the radially inner ends of the first inner opening 104. The end of the first inner claw 116 in the protruding direction (hereinafter referred to as “protruding end 116b”) is in (line) contact with the lower surface 44a of the second metal separator 44. The first inner claw 116 extends straight from the root 116a to the protruding end 116b. The first inner claw 116 may be curved from the root 116a to the protruding end 116b.

[0053] As shown in FIG. 3, the second inner claws 118 are arranged at the second inner openings 106. The second inner claw 118 is formed such that the lateral width becomes narrower radially inward in the flat plate portion 92. The second inner claw 118 is formed in a shape (trapezoidal shape) corresponding to the shape of the second inner opening 106. The size of the second inner claw 118 is smaller than the size of the contour of the second inner opening 106.

[0054] The second inner claw 118 protrudes upward from the flat plate portion 92 and is inclined radially inward from the outer ends of the second inner opening 106. In other words, the second inner claw 118 is inclined upward from the flat plate portion 92. That is, a root 118a of the second inner claw 118 is positioned between the radially outer ends of the second inner opening 106. The end of the second inner claw 118 in the protruding direction (hereinafter referred to as “protruding end 118b”) is in (line) contact with the lower surface 44a of the second metal separator 44. The second inner claw 118 extends straight from the root 118a to the protruding end 118b. The second inner claw 118 may be curved from the root 118a to the protruding end 118b. The first inner claws 116 and the second inner claws 118 are alternately arranged in the circumferential direction of the flat plate portion 92.

[0055] The outer claw group 114 is formed by arranging the 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 positioned radially outward of the inner claw group 112 in the flat plate portion 92. The outer claw group 114 includes first outer claws 120 and second outer claws 122. The first outer claw 120 is formed in the same manner as the first inner claw 116. The second outer claw 122 is formed in the same manner as the second inner claw 118.

[0056] A root 120a of the first outer claw 120 is positioned between the radially inner ends of the first outer opening 108. The end of the first outer claw 120 in the protruding direction (hereinafter referred to as “protruding end 120b”) is in (line) contact with the lower surface 44a of the second metal separator 44. A root 122a of the second outer claw 122 is positioned between the radially outer ends of the second outer opening 110. The end of the second outer claw 122 in the protruding direction (hereinafter referred to as “protruding end 122b”) is in (line) contact with the lower surface 44a of the second metal separator 44. The first outer claws 120 and the second outer claws 122 are alternately arranged in the circumferential direction of the flat plate portion 92.

[0057] As shown in FIGS. 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).

[0058] As shown in FIGS. 3 to 5, a capturing member 124 capable of capturing cations (metal ions) is provided on the outer circumferential portion of the conductive sheet 78. A surrounding (annular) outer circumferential recess 126 for accommodating the capturing member 124 is formed in an upper surface 78a of the conductive sheet 78. Accordingly, the water (containing metal ions) flowing down from the spring member 80 can be stored in the outer circumferential recess 126, and thus the water containing metal ions can be easily brought into contact with the capturing member 124. The outer circumferential recess 126 is located radially outward of the spring member 80 (see FIG. 3).

[0059] The capturing member 124 is, for example, an ion exchange resin (cation exchange resin). The capturing member 124 is not limited to the ion exchange resin, and may be an adsorption member (for example, activated carbon) capable of adsorbing cations (metal ions). The capturing member 124 has a closed-loop shape (for example, an annular shape). This makes it possible to bring the water containing metal ions into contact with the capturing member 124 more reliably.

[0060] The capturing member 124 is attached to a holder 128 that is attachable to and detachable from the outer circumferential portion of the conductive sheet 78. In accordance with such a configuration, the capturing member 124 can be easily replaced when deteriorated. In accordance with this feature, it is possible to easily perform maintenance of the differential pressure electrolysis cell 10.

[0061] The holder 128 has a closed-loop perimeter (for example, an annular shape). The holder 128 may be divided into a plurality of pieces in the circumferential direction, for example. In this case, it is preferable that the capturing member 124 is also dividable in accordance with the divided structure of the holder 128. Such a holder 128 can be easily attached to and detached from the conductive sheet 78 as compared to the case where the holder 128 is integrally formed in an annular shape. The structure for attaching and detaching the holder 128 to and from the outer circumferential portion of the conductive sheet 78 may be, for example, a fitting structure, but any measure may be adopted as appropriate.

[0062] As shown in FIG. 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, and thus the capturing member 124 can be replaced more easily. The lubricating member 129 has a closed-loop perimeter (for example, an annular shape). The lubricating member 129 is made of, for example, a fluoro resin having a relatively excellent sliding ability, 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 with a resin material, for example.

[0063] As shown in FIGS. 3 to 5, a guide groove 130 is formed in the upper surface 78a of the conductive sheet 78 to guide water flowing down on the conductive sheet 78 from the spring member 80 to the outer circumferential recess 126. Thus, the guide groove 130 allows water flowing down from the spring member 80 to the conductive sheet 78 to smoothly flow out to the outer circumferential recess 126.

[0064] The guide groove 130 includes a plurality of closed-loop grooves 132 and a plurality of radial grooves 134. Each of the closed-loop grooves 132 has an annular shape. The plurality of closed-loop grooves 132 are arranged under the plurality of claws 94. In this arrangement, water flowing down from the plurality of claws 94 can be received by the closed-loop grooves 132.

[0065] The width of each of the closed-loop grooves 132 can be set as appropriate. In the present embodiment, the plurality of closed-loop grooves 132 include a first closed-loop groove 136, a second closed-loop groove 138, a third closed-loop groove 140, and a fourth closed-loop groove 142.

[0066] As shown in FIG. 3, the first closed-loop groove 136 and the second closed-loop groove 138 are arranged under the inner claw group 112. The first closed-loop groove 136 is arranged under the roots 116a of the plurality of first inner claws 116. The second closed-loop groove 138 is arranged under the roots 118a of the plurality of second inner claws 118. The third closed-loop groove 140 and the fourth closed-loop groove 142 are arranged under the outer claw group 114. The third closed-loop groove 140 is arranged under the roots 120a of the plurality of first outer claws 120. The fourth closed-loop groove 142 is arranged under the roots 122a of the plurality of second outer claws 122. The number, position, size, shape, and the like of the closed-loop grooves 132 may be adopted as appropriate.

[0067] As shown in FIG. 4, the plurality of radial grooves 134 are arranged at intervals in the circumferential direction of the conductive sheet 78. In the present embodiment, eight radial grooves 134 are formed in the upper surface 78a of the conductive sheet 78. Each of the radial grooves 134 extends along the radial direction of the conductive sheet 78. In this arrangement, water flowing down from the spring member 80 to the conductive sheet 78 can be quickly guided to the outer circumferential recess 126 through the radial grooves 134.

[0068] As shown in FIG. 5, the radial grooves 134 are formed such that the groove depth increases radially outward in the conductive sheet 78. In this case, water in the radial grooves 134 easily flows to the outer circumferential recess 126. Each of the radial grooves 134 communicates with the plurality of closed-loop grooves 132 (see FIG. 4). This allows the water received by the closed-loop grooves 132 to flow into the radial grooves 134.

[0069] To be more specific, each of the radial grooves 134 includes a first groove section 134a, a second groove section 134b, a third groove section 134c, and a fourth groove section 134d. The first groove section 134a extends so as to connect the first closed-loop groove 136 and the second closed-loop groove 138. The second groove section 134b extends so as to connect the second closed-loop groove 138 and the third closed-loop groove 140. The groove depth of the second groove section 134b is greater than the groove depth of the first groove section 134a. The third groove section 134c extends so as to connect the third closed-loop groove 140 and the fourth closed-loop groove 142. The groove depth of the third groove section 134c is greater than the groove depth of the second groove section 134b. The fourth groove section 134d extends so as to connect the fourth closed-loop groove 142 and the outer circumferential recess 126. The groove depth of the fourth groove section 134d is greater than the groove depth of the third groove section 134c. The depth of the outer circumferential recess 126 is greater than the groove depth of the fourth groove section 134d.

[0070] The groove bottom surface of each of the first groove section 134a, the second groove section 134b, the third groove section 134c, and the fourth groove section 134d is a horizontal surface, but may be a surface inclined downward radially outward. When such an inclined surface is adopted, water (liquid water) in the radial grooves 134 can be more smoothly guided to the outer circumferential recess 126. The groove bottom surface of the radial groove 134 is not limited to the example formed in a stepped shape, and may be a surface continuously inclined downward from the first closed-loop groove 136 to the outer circumferential recess 126. The number, position, size, shape, and the like of the radial grooves 134 may be adopted as appropriate.

[0071] Next, basic operations of the differential pressure electrolysis stack 14 according to the present embodiment will be briefly described. Here, the differential pressure electrolysis stack 14 that generates oxygen gas and hydrogen gas by electrolyzing water will be described as an example.

[0072] As shown in FIGS. 1 and 2, water (electrolysis fluid) is supplied to the fluid inlet 28 of the differential pressure electrolysis stack 14 by a water pump (not shown), and electrical currents are supplied to the first current collector 60 and the second current collector 74 of each differential pressure electrolysis cell 10 from the electrolysis power supply 22. The water supplied to the fluid inlet 28 is guided to the first electrode catalyst layer 50 through the fluid supply passage 34 and the supply flow path 66.

[0073] In this case, water is electrolyzed in the membrane electrode assembly 40, and hydrogen gas is generated in the first electrode catalyst layer 50 and oxygen gas is generated in the second electrode catalyst layer 52. The fluid containing the hydrogen gas generated in the first electrode catalyst layer 50 and the water that has not been electrolyzed is discharged to the outside of the differential pressure electrolysis stack 14 through the discharge flow path 68, the fluid discharge passage 36, and the fluid outlet 30. The oxygen gas generated in the second electrode catalyst layer 52 is guided to the product gas discharge passage 38 through a space between the membrane electrode assembly 40 and the second metal separator 44 (hereinafter, may be referred to as a “product gas accommodation chamber 144”) and grooves (not shown) of the second inner peripheral member 82. The oxygen gas guided to the product gas discharge passage 38 is discharged from the product gas outlet 32 to the product gas lead-out path 16.

[0074] The product gas lead-out path 16 is provided with the back pressure valve 18. Therefore, the oxygen gas generated in the second electrode catalyst layer 52 is held back by the back pressure valve 18. In accordance with this manner, it is possible to make the pressure of the oxygen gas (product gas) generated at the second electrode catalyst layer 52 higher than the pressure of the water (electrolysis fluid) supplied to the first electrode catalyst layer 50. That is, the pressure of the oxygen gas in the product gas accommodation chamber 144 becomes higher than the pressure of the water supplied to the first electrode catalyst layer 50. Thereafter, the back pressure valve 18 is opened, and the tank 20 is filled with the high-pressure oxygen gas.

[0075] In the present embodiment, the spring member 80 is in line contact with the lower surface 44a of the second metal separator 44. Therefore, the coating is likely to peel off from the position at which the spring member 80 contacts the second metal separator 44. In addition, when oxygen gas is generated in the second electrode catalyst layer 52, the portion at which metal is exposed is likely to corrode, and thus metal ions are likely to be eluted from the metal exposed portion. Even when hydrogen gas is generated in the second electrode catalyst layer 52, metal ions may be eluted from the metal exposed portion. Further, in the case where the 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 in the product gas accommodation chamber 144 is likely to increase, and thus the water is likely to condense on the second metal separator 44, the spring member 80, and the like.

[0076] The water droplets containing the metal ions flow downward along the claws 94 of the spring member 80. To be specific, the water droplets on the protruding ends 116b of the first inner claws 116 flow down along the first inner claws 116 to the roots 116a of the first inner claws 116, and then are guided into the first closed-loop groove 136. The water droplets on the protruding ends 120b of the first outer claw 120 flow down along the first outer claws 120 to the roots 120a of the first outer claws 120, and then are guided into the third closed-loop groove 140. The water droplets on the protruding ends 118b of the second inner claws 118 flow down along the second inner claws 118 to the roots 118a of the second inner claws 118, and then are guided into the second closed-loop groove 138. The water droplets on the protruding ends 122b of the second outer claws 122 flow down along the second outer claws 122 to the roots 122a of the second outer claws 122, and then are guided into the fourth closed-loop groove 142.

[0077] The water guided to the first closed-loop groove 136, the second closed-loop groove 138, the third closed-loop groove 140, and the fourth closed-loop groove 142 flows to the outer circumferential recess 126 via the plurality of radial grooves 134. The water flowing into the outer circumferential recess 126 comes into contact with the capturing member 124, and thereby metal ions (cations) contained in the water are captured (removed). Therefore, even if the water from which the metal ions have been removed flows downward and contacts the electrolyte membrane 48, the electrolyte membrane 48 can be prevented from deteriorating.

[0078] That is, according to the present embodiment, water (water containing metal ions) flowing down to the upper surface 78a of the conductive sheet 78 from metal exposed portions of the second metal separator 44 and the spring member 80 can be brought into contact with the capturing member 124 at the outer circumference of the conductive sheet 78. Thus, the metal ions can be captured (removed) by the capturing member 124 before the water containing the metal ions flows down to the electrolyte membrane 48. Therefore, it is possible to suppress deterioration of the electrolyte membrane 48 due to metal ions. According to such a configuration, it is possible to provide a more favorable differential pressure electrolysis cell 10, differential pressure electrolysis stack 14.

[0079] The present embodiment is not limited to the configuration described above. For example, as shown in FIG. 6, the radial grooves 134 may be formed such that the groove depth is constant radially outward in the conductive sheet 78. That is, the radial grooves 134 may extend along a horizontal plane.

[0080] In relation to the above-described embodiment, the following supplementary notes are further disclosed.Supplementary Note 1

[0081] The differential pressure electrolysis cell (10) according to the present disclosure is configured to electrolyze an electrolysis fluid supplied to the first electrode catalyst layer (50) to generate a product gas in the second electrode catalyst layer (52), the product gas having a higher pressure than the electrolysis fluid, the differential pressure electrolysis cell including: the membrane electrode assembly (40) including the electrolyte membrane (48), the first electrode catalyst layer and the second electrode catalyst layer, the first electrode catalyst layer and the second electrode catalyst layer being joined to opposite sides of the electrolyte membrane; the metal separator (44) arranged above the second electrode catalyst layer; the conductive sheet (78) disposed on the current collector (74) positioned between the metal separator and the second electrode catalyst layer; the spring member (80) made of metal, in contact with the metal separator and the conductive sheet, and configured to press the conductive sheet downward; and the capturing member (124) provided on an outer circumferential portion of the conductive sheet and configured to capture cations.

[0082] In this manner, water (water containing metal ions) flowing down on the upper surface of the conductive sheet from metal exposed portions of the metal separator and the spring member can be brought into contact with the capturing member at the outer circumference of the conductive sheet. This allows metal ions to be captured (removed) by the capturing member before the water containing metal ions further flows down to the electrolyte membrane. Therefore, deterioration of the electrolyte membrane due to metal ions can be suppressed. That is, according to such a configuration, a more favorable differential pressure electrolysis cell can be provided.Supplementary Note 2

[0083] In the differential pressure electrolysis cell according to Supplementary Note 1, the outer circumferential recess (126) having a closed-loop shape may be formed in an upper surface (78a) of the conductive sheet, for accommodating the capturing member.

[0084] According to such a configuration, since water containing metal ions can be stored in the recess, the water containing metal ions can be easily brought into contact with the capturing member.Supplementary Note 3

[0085] In the differential pressure electrolysis cell according to Supplementary Note 2, the capturing member may be formed to have a closed-loop shape.

[0086] According to such a configuration, water containing metal ions can be more reliably brought into contact with the capturing member.Supplementary Note 4

[0087] In the differential pressure electrolysis cell according to Supplementary Note 2 or 3, the guide groove (130) may be formed on the upper surface of the conductive sheet, the guide groove being configured to guide, to the outer circumferential recess, water fallen on the conductive sheet from the spring member.

[0088] According to such a configuration, the water flowing down from the spring member to the conductive sheet can be smoothly flowed to the outer circumferential recess by the guide groove.Supplementary Note 5

[0089] In the differential pressure electrolysis cell according to Supplementary Note 4, the guide groove may include the radial groove (134) extending along a radial direction of the conductive sheet.

[0090] In this arrangement, water falling from the spring member to the conductive sheet can be quickly guided to the outer circumferential recess through the radial groove.Supplementary Note 6

[0091] In the differential pressure electrolysis cell according to Supplementary Note 5, the radial groove may be formed to increase a groove depth radially outward in the conductive sheet.

[0092] In this manner, water in the radial groove easily flows to the outer circumferential recess.Supplementary Note 7

[0093] In the differential pressure electrolysis cell according to Supplementary Note 5 or 6, the spring member may include the flat plate portion (92) and the claw (94) that protrudes from the flat plate portion so as to be inclined upward and comes into contact with the metal separator, and the guide groove may be arranged under the claw.

[0094] In accordance with such a configuration, water flowing down along the claw can be received by the guide groove.Supplementary Note 8

[0095] In the differential pressure electrolysis cell according to Supplementary Note 7, a plurality of the claws may be arranged at intervals along a circumferential direction of the flat plate portion, and the guide groove may include the closed-loop groove (132) that is arranged under the plurality of claws arranged along the circumferential direction of the flat plate portion and is in communication with the radial groove.

[0096] In accordance with such a configuration, water flowing down from the plurality of claws can be received by the closed-loop groove. In addition, the water received by the closed-loop groove can be flowed to the radial groove.Supplementary Note 9

[0097] The differential pressure electrolysis cell according to any one of Supplementary Notes 1 to 8 may further include the holder (128) that is attachable to and detachable from the outer circumferential portion of the conductive sheet, and the capturing member may be attached to the holder.

[0098] In accordance with such a configuration, the capturing member can be easily replaced when deteriorated. In accordance with this feature, it is possible to easily perform maintenance of the differential pressure electrolysis cell.Supplementary Note 10

[0099] In the differential pressure electrolysis cell according to Supplementary Note 9, the lubricating member (129) may be interposed between the capturing member and the conductive sheet.

[0100] In accordance with such a configuration, the capturing member can be easily removed from the conductive sheet, and thus the capturing member can be more easily replaced.Supplementary Note 11

[0101] The differential pressure electrolysis stack (14) of the present disclosure is formed of a plurality of the differential pressure electrolysis cells according to any one of Supplementary Note 1 to 10 that are stacked.

[0102] According to such a configuration, it is possible to obtain a differential pressure electrolysis stack that exhibits the effects described in Supplementary Notes 1 to 10. Thus, a more satisfactory differential pressure water electrolysis stack can be obtained.

[0103] Although concerning the present disclosure, a detailed description thereof has been presented above, the present disclosure is not necessarily limited to the individual embodiments described above. These embodiments can be subjected to various additions, substitutions, modifications, partial deletions and the like, within a range that does not depart from the essence and gist of the present disclosure, or alternatively, the spirit and gist of the present disclosure as derived from the contents described in the claims and their equivalents. Further, these embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each of the operations and the order of each of the processes are shown merely as examples, and the present invention is not necessarily limited to these examples. The same applies also in the case that numerical values or mathematical expressions are used in the description of the aforementioned embodiments.

Examples

Embodiment Construction

[0017]A differential pressure electrolysis cell can electrolyze an electrolysis fluid supplied to a first electrode catalyst layer of a membrane electrode assembly to generate a product gas at a pressure higher than the electrolysis fluid in a second electrode catalyst layer of the membrane electrode assembly. In this type of differential pressure electrolysis cell, a metal separator is disposed above the second electrode catalyst layer. A spring member made of metal is arranged between the metal separator and the second electrode catalyst layer, for pressing a current collector toward the second electrode catalyst layer. The metal separator and the spring member are coated, for example, to prevent elution of metal ions (cations).

[0018]However, the coating may peel off from a position at which the spring member contacts the metal separator. In addition, the coating may peel off due to aging deterioration. When water droplets adhere to a portion at which the coating has been peeled o...

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2025-027922 filed on Feb. 25, 2025, the contents of which are incorporated herein by reference.BACKGROUND OF THE INVENTIONField of the Invention

[0002] The present disclosure relates to a differential pressure electrolysis cell and a differential pressure electrolysis stack.Description of the Related Art

[0003] In recent years, research and development have been conducted on differential pressure electrolysis stacks that contribute to energy efficiency in order to ensure that more people have access to affordable, reliable, sustainable and modern energy.

[0004] JP 7037965 B2 discloses a configuration of a differential pressure electrolysis cell of a differential pressure electrolysis stack.SUMMARY OF THE INVENTION

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

[0006] The present disclosure has the object of solving the aforementioned problem.

[0007] A first aspect of the present disclosure is characterized by a differential pressure electrolysis cell configured to electrolyze an electrolysis fluid supplied to a first electrode catalyst layer to generate a product gas in a second electrode catalyst layer, the product gas having a higher pressure than the electrolysis fluid, the differential pressure electrolysis cell including: a membrane electrode assembly including an electrolyte membrane, the first electrode catalyst layer and the second electrode catalyst layer, the first electrode catalyst layer and the second electrode catalyst layer being joined to opposite sides of the electrolyte membrane; a metal separator arranged above the second electrode catalyst layer; a conductive sheet disposed on a current collector positioned between the metal separator and the second electrode catalyst layer; a spring member made of metal, in contact with the metal separator and the conductive sheet, and configured to press the conductive sheet downward; and a capturing member provided on an outer circumferential portion of the conductive sheet and configured to capture cations.

[0008] A second aspect of the present disclosure is characterized by a differential pressure electrolysis stack in which a plurality of the differential pressure electrolysis cells described above are stacked.

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

[0010] The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a schematic view of an electrolysis apparatus including a differential pressure electrolysis stack according to an embodiment;

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

[0013] FIG. 3 is a top view of a spring member shown in FIG. 2 as viewed from the arrow III direction;

[0014] FIG. 4 is a plan view of a conductive sheet;

[0015] FIG. 5 is a partially omitted cross-sectional view taken along line V-V of FIG. 3; and

[0016] FIG. 6 is a partially omitted cross-sectional view illustrating a modification of a radial groove.DETAILED DESCRIPTION OF THE INVENTION

[0017] A differential pressure electrolysis cell can electrolyze an electrolysis fluid supplied to a first electrode catalyst layer of a membrane electrode assembly to generate a product gas at a pressure higher than the electrolysis fluid in a second electrode catalyst layer of the membrane electrode assembly. In this type of differential pressure electrolysis cell, a metal separator is disposed above the second electrode catalyst layer. A spring member made of metal is arranged between the metal separator and the second electrode catalyst layer, for pressing a current collector toward the second electrode catalyst layer. The metal separator and the spring member are coated, for example, to prevent elution of metal ions (cations).

[0018] However, the coating may peel off from a position at which the spring member contacts the metal separator. In addition, the coating may peel off due to aging deterioration. When water droplets adhere to a portion at which the coating has been peeled off and metal is exposed, metal ions may be eluted. When the water containing the metal ions flows downward from the spring member and contacts the electrolyte membrane, the electrolyte membrane may be deteriorated by the metal ions. According to the aspects described below, the deterioration of the electrolyte membrane due to metal ions can be suppressed.

[0019] FIG. 1 is a schematic view of an electrolysis apparatus 12 including a differential pressure electrolysis stack 14 according to an embodiment. As shown in FIG. 1, the electrolysis apparatus 12 includes, for example, a differential pressure electrolysis stack 14, a product gas lead-out path 16, a back pressure valve 18, a tank 20, and an electrolytic power supply 22.

[0020] The differential pressure electrolysis stack 14 includes a cell stack body 24, a pair of end plates 26a, 26b, a fluid inlet 28, a fluid outlet 30, and a product gas outlet 32. The cell stack body 24 is formed by stacking a plurality of differential pressure electrolysis cells 10 in the up-down direction.

[0021] A differential pressure electrolysis cell 10 can electrolyze an electrolysis fluid to generate a product gas at a pressure higher than the electrolysis fluid. A differential pressure electrolysis cell 10 is a water electrolysis cell capable of electrolyzing water (electrolysis fluid) to generate an oxygen gas (product gas) at a pressure higher than the electrolysis fluid. A differential pressure electrolysis cell 10 may be a hydrogen electrolysis cell (electrochemical hydrogen compressor) capable of electrolyzing a hydrogen gas (electrolysis fluid) to generate a hydrogen gas (product gas) at a pressure higher than the electrolysis fluid.

[0022] The pair of end plates 26a, 26b sandwich the plurality of differential pressure electrolysis cells 10 in the up-down direction. An electrolysis fluid is supplied to the inside of the cell stack body 24 through the fluid inlet 28. A fluid is discharged to the outside of the cell stack body 24 through the fluid outlet 30. The fluid to be discharged includes a remainder of the electrolysis fluid that is not electrolyzed in the differential pressure electrolysis cell 10. The product gas outlet 32 guides the product gas from the differential pressure electrolysis stack 14 to the product gas lead-out path 16. The product gas outlet 32 is provided, for example, in the central portion of the end plate 26b.

[0023] The product gas lead-out path 16 guides the product gas to the tank 20. The product gas lead-out path 16 is provided with the back pressure valve 18. The back pressure valve 18 opens in the case where the pressure of the product gas guided from the differential pressure electrolysis stack 14 is equal to or higher than a predetermined threshold. The back pressure valve 18 closes in the case where the pressure of the product gas guided from the differential pressure electrolysis stack 14 is less than the threshold. The tank 20 is a high pressure gas tank that can store the product gas. The electrolytic power supply 22 is a direct-current power source. The electrolytic power supply 22 is electrically connected to the cell stack 24.

[0024] FIG. 2 is a cross-sectional view of the differential pressure electrolysis cell 10. As shown in FIG. 2, the differential pressure electrolysis cell 10 is provided with a fluid supply passage 34, a fluid discharge passage 36, and a product gas discharge passage 38 that extend through the differential pressure electrolysis cell 10 in the up-down direction. The electrolysis fluid guided from the fluid inlet 28 (see FIG. 1) flows through the fluid supply passage 34. The fluid discharge passage 36 guides the fluid to be discharged from the fluid outlet 30 (see FIG. 1). The product gas discharge passage 38 guides the product gas to the product gas outlet 32 (see FIG. 1).

[0025] The fluid supply passage 34 and the fluid discharge passage 36 are provided in the outer peripheral portion of the differential pressure electrolysis cell 10. The product gas discharge passage 38 is provided in the central portion of the differential pressure electrolysis cell 10. The product gas discharge passage 38 is positioned between the fluid supply passage 34 and the fluid discharge passage 36.

[0026] The differential pressure electrolysis cell 10 includes a membrane electrode assembly 40, a pair of metal separators 42, 44, and a frame member 46. The membrane electrode assembly 40 is also referred to as an electrolyte membrane with catalyst layers (CCM: Catalyst-Coated Membrane).

[0027] 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 that is capable of exchanging ions. The electrolyte membrane 48, for example, is a proton exchange membrane (PEM). The electrolyte membrane 48 may be an anion exchange membrane (AEM). The first electrode catalyst layer 50 is bonded to a lower surface 48a of the electrolyte membrane 48. The second electrode catalyst layer 52 is bonded to an upper surface 48b of the electrolyte membrane 48.

[0028] The pair of metal separators 42, 44 are disposed on opposite sides of the membrane electrode assembly 40. The metal separators 42, 44 are made of a metal material such as stainless steel. The metal material constituting the metal separators 42, 44 is not limited to stainless steel. Hereinafter, the metal separator 42 arranged below the membrane electrode assembly 40 may be referred to as a “first metal separator 42”, and the metal separator 44 arranged above the membrane electrode assembly 40 may be referred to as a “second metal separator 44”.

[0029] The frame member 46 surrounds the membrane electrode assembly 40 from the radially outer side. Surrounding (annular) seal members (rubber seals) 56 are provided between the frame member 46 and each of the metal separators 42, 44 to prevent the electrolysis fluid from flowing to the outside before or after electrolysis.

[0030] Between the first metal separator 42 and the membrane electrode assembly 40, a support member 58, a current collector 60 (hereinafter referred to also as the first current collector 60), a protective sheet 62, and a first inner peripheral member 64 are provided.

[0031] The support member 58 is disposed on the first metal separator 42. The support member 58 is a plate member having a closed-loop perimeter (for example, an annular shape). A supply flow path 66 in communication with the fluid supply passage 34 and a discharge flow path 68 in communication with the fluid discharge passage 36 are formed in the support member 58.

[0032] The first current collector 60 has a closed-loop perimeter (for example, an annular shape). The first current collector 60 is stacked on the support member 58. In other words, the first current collector 60 is supported by the support member 58. The first current collector 60 includes a first fluid distribution section 70. The first fluid distribution section 70 is formed of a porous material. The first fluid distribution section 70 guides the electrolysis fluid flowing through the supply flow path 66 to the first electrode catalyst layer 50. The fluid to be discharged, containing the remainder of the electrolysis fluid that has not been consumed in the first electrode catalyst layer 50, is guided to the discharge flow path 68 through the first fluid distribution section 70.

[0033] The protective sheet 62 has a closed-loop perimeter (for example, an annular shape). The protective sheet 62 is stacked on the first current collector 60. The protective sheet 62 is positioned between the membrane electrode assembly 40 and the first current collector 60. The protective sheet 62 prevents the membrane electrode assembly 40 from being damaged by being pressed by the first current collector 60. The protective sheet 62 has a plurality of through holes 72 for allowing the electrolysis fluid and the fluid to be discharged to flow between the first fluid distribution section 70 and the first electrode catalyst layer 50.

[0034] The first inner peripheral member 64 has a closed-loop perimeter (for example, an annular shape). The first inner peripheral member 64 extends in the up-down direction so as to be inserted through the inner hole of the support member 58, the inner hole of the first current collector 60, and the inner hole of the protective sheet 62. The product gas discharge passage 38 is provided inside the first inner peripheral member 64.

[0035] Between the membrane electrode assembly 40 and the second metal separator 44, a current collector 74 (hereinafter, may be referred to as “second current collector 74”), a resin sheet 76, a conductive sheet 78, a spring member (biasing member) 80, a second inner peripheral member 82, a pressure-resistant member 84, and a seal member 86 are provided.

[0036] The second current collector 74 has a closed-loop perimeter (for example, an annular shape). The second current collector 74 is stacked on the membrane electrode assembly 40. When a current is supplied (a voltage is applied) between the first current collector 60 and the second current collector 74, the electrolysis 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 current collector 74 includes a second fluid distribution section 88. The second fluid distribution section 88 is formed of a porous material. The product gas generated in the second electrode catalyst layer 52 flows through the second fluid distribution section 88. The outer diameter of the second current collector 74 is smaller than the outer diameter of the electrolyte membrane 48.

[0037] The resin sheet 76 has a closed-loop perimeter (for example, an annular shape). The resin sheet 76 is made of an insulating material. The resin sheet 76 is disposed in the inner hole of the second current collector 74.

[0038] The conductive sheet 78 has a closed-loop perimeter (for example, an annular shape). The conductive sheet 78 is stacked on the second current collector 74. The conductive sheet 78 is made of metal 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 the present embodiment, the outer diameter of the conductive sheet 78 is larger than the outer diameter of the second current collector 74, but may be substantially the same as the outer diameter of the second current collector 74.

[0039] The spring member 80 has a closed-loop perimeter (for example, an annular shape). The spring member 80 is stacked on 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 the membrane electrode assembly 40 (downward). This allows the second current collector 74 to be in close contact with the second electrode catalyst layer 52. The details of the conductive sheet 78 and the spring member 80 will be described later.

[0040] The second inner peripheral member 82 has a closed-loop perimeter (for example, an annular shape). The second inner peripheral member 82 is disposed in the inner hole of the spring member 80. The second inner peripheral member 82 is interposed between the conductive sheet 78 and the second metal separator 44. The second current collector 74, the conductive sheet 78, the second inner peripheral member 82, and the second metal separator 44 are electrically connected to each other. The second inner peripheral member 82 has grooves (flow channels) (not shown) for guiding the product gas to the product gas discharge passage 38.

[0041] The seal member 86 is a rubber seal (O-ring) disposed between the electrolyte membrane 48 and the second metal separator 44. The seal member 86 has a closed-loop perimeter (for example, an annular shape). The seal member 86 prevents the product gas produced in the second electrode catalyst layer 52 from leaking to the outside. The seal member 86 surrounds the second current collector 74, the conductive sheet 78, and the spring member 80.

[0042] The pressure-resistant member 84 has a closed-loop perimeter (for example, an annular shape). The pressure-resistant member 84 is disposed on the outer side of the seal member 86. The inner circumferential surface of the pressure-resistant member 84 is in contact with the seal member 86. The pressure-resistant member 84 suppresses radially outward elastic deformation of the seal member 86. The pressure-resistant member 84 is in contact with the electrolyte membrane 48 and the second metal separator 44.

[0043] Next, a description will be made concerning the configurations of the spring member 80 and the conductive sheet 78. FIG. 3 is a top view of the spring member 80 shown in FIG. 2 as viewed from the arrow III direction. FIG. 4 is a plan view of the conductive sheet 78. FIG. 5 is a partially omitted cross-sectional view taken along line V-V of FIG. 3. As shown in FIGS. 2 and 5, in the present embodiment, the spring member 80 is a plate spring, but is not limited thereto, and may be, for example, a disc spring or the like.

[0044] The spring member 80 is made of metal 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 with a coating (not shown) to prevent elution of metal ions (cations).

[0045] As shown in FIGS. 3 and 5, the spring member 80 has a flat plate portion 92 and a plurality of claws 94. The flat plate portion 92 has a closed-loop perimeter (for example, an annular 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 substantially the same as the outer diameter of the second current collector 74. The second inner peripheral member 82 is disposed in the inner hole of the flat plate portion 92 (hereinafter may be referred to as “center hole 96”).

[0046] As shown in FIG. 3, a plurality of openings 98 are formed in the flat plate portion 92. The openings 98 are holes penetrating the flat plate portion 92 in the thickness direction. The claws 94 are respectively located at each of the plurality of openings 98. The plurality of openings 98 are arranged at intervals in the circumferential direction of the flat plate portion 92. The plurality of openings 98 may be arranged at intervals in the radial direction of the flat plate portion 92.

[0047] The plurality of openings 98 includes an inner opening group 100 and an outer opening group 102. The inner opening group 100 is formed by arranging the plurality of openings 98 at intervals in the circumferential direction of the flat plate portion 92 so as to surround the center hole 96. The inner opening group 100 includes first inner openings 104 and second inner openings 106. Each of first inner openings 104 and second inner openings 106 is formed in a trapezoidal shape when viewed from above.

[0048] The first inner opening 104 is formed such that the width between ends thereof in the circumferential direction becomes narrower radially outward. The second inner opening 106 is formed such that the width between ends thereof in the circumferential direction becomes narrower radially inward. The width refers to the length between the ends of the opening 98 in the direction along the circumferential direction of the flat plate portion 92. In the inner opening group 100, the first inner openings 104 and the second inner openings 106 are alternately arranged in the circumferential direction of the flat plate portion 92.

[0049] The outer opening group 102 is formed by arranging the 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 positioned radially outward of the inner opening group 100 in the flat plate portion 92. The outer opening group 102 includes first outer openings 108 and second outer openings 110. The first outer opening 108 is formed in the same manner as the first inner opening 104. The second outer opening 110 is formed in the same manner as the second inner opening 106. Therefore, the detailed descriptions of the first outer opening 108 and the second outer opening 110 are omitted. In the outer opening group 102, the first outer openings 108 and the second outer openings 110 are alternately arranged in the circumferential direction of the flat plate portion 92.

[0050] The plurality of claws 94 include an inner claw group 112 and an outer claw group 114. The inner claw group 112 is formed by the claws 94 located at the openings 98 forming the inner opening group 100. The inner claw group 112 includes first inner claws 116 and second inner claws 118. Each of first inner claws 116 and second inner claws 118 is formed in a trapezoidal shape when viewed from above.

[0051] The first inner claws 116 are arranged at the first inner openings 104. The first inner claw 116 is formed such that the lateral width (the dimension along the circumferential direction of the flat plate portion 92) becomes narrower radially outward in the flat plate portion 92. The first inner claw 116 is formed in a shape corresponding to the shape of the first inner opening 104 when viewed from above. The size of the first inner claw 116 is smaller than the size of the contour of the first inner opening 104.

[0052] As shown in FIGS. 3 and 5, the first inner claw 116 protrudes upward from the flat plate portion 92 and is inclined radially outward from the inner ends of the first inner opening 104. In other words, the first inner claw 116 is inclined upward from the flat plate portion 92. That is, a root 116a of the first inner claw 116 is positioned between the radially inner ends of the first inner opening 104. The end of the first inner claw 116 in the protruding direction (hereinafter referred to as “protruding end 116b”) is in (line) contact with the lower surface 44a of the second metal separator 44. The first inner claw 116 extends straight from the root 116a to the protruding end 116b. The first inner claw 116 may be curved from the root 116a to the protruding end 116b.

[0053] As shown in FIG. 3, the second inner claws 118 are arranged at the second inner openings 106. The second inner claw 118 is formed such that the lateral width becomes narrower radially inward in the flat plate portion 92. The second inner claw 118 is formed in a shape (trapezoidal shape) corresponding to the shape of the second inner opening 106. The size of the second inner claw 118 is smaller than the size of the contour of the second inner opening 106.

[0054] The second inner claw 118 protrudes upward from the flat plate portion 92 and is inclined radially inward from the outer ends of the second inner opening 106. In other words, the second inner claw 118 is inclined upward from the flat plate portion 92. That is, a root 118a of the second inner claw 118 is positioned between the radially outer ends of the second inner opening 106. The end of the second inner claw 118 in the protruding direction (hereinafter referred to as “protruding end 118b”) is in (line) contact with the lower surface 44a of the second metal separator 44. The second inner claw 118 extends straight from the root 118a to the protruding end 118b. The second inner claw 118 may be curved from the root 118a to the protruding end 118b. The first inner claws 116 and the second inner claws 118 are alternately arranged in the circumferential direction of the flat plate portion 92.

[0055] The outer claw group 114 is formed by arranging the 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 positioned radially outward of the inner claw group 112 in the flat plate portion 92. The outer claw group 114 includes first outer claws 120 and second outer claws 122. The first outer claw 120 is formed in the same manner as the first inner claw 116. The second outer claw 122 is formed in the same manner as the second inner claw 118.

[0056] A root 120a of the first outer claw 120 is positioned between the radially inner ends of the first outer opening 108. The end of the first outer claw 120 in the protruding direction (hereinafter referred to as “protruding end 120b”) is in (line) contact with the lower surface 44a of the second metal separator 44. A root 122a of the second outer claw 122 is positioned between the radially outer ends of the second outer opening 110. The end of the second outer claw 122 in the protruding direction (hereinafter referred to as “protruding end 122b”) is in (line) contact with the lower surface 44a of the second metal separator 44. The first outer claws 120 and the second outer claws 122 are alternately arranged in the circumferential direction of the flat plate portion 92.

[0057] As shown in FIGS. 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).

[0058] As shown in FIGS. 3 to 5, a capturing member 124 capable of capturing cations (metal ions) is provided on the outer circumferential portion of the conductive sheet 78. A surrounding (annular) outer circumferential recess 126 for accommodating the capturing member 124 is formed in an upper surface 78a of the conductive sheet 78. Accordingly, the water (containing metal ions) flowing down from the spring member 80 can be stored in the outer circumferential recess 126, and thus the water containing metal ions can be easily brought into contact with the capturing member 124. The outer circumferential recess 126 is located radially outward of the spring member 80 (see FIG. 3).

[0059] The capturing member 124 is, for example, an ion exchange resin (cation exchange resin). The capturing member 124 is not limited to the ion exchange resin, and may be an adsorption member (for example, activated carbon) capable of adsorbing cations (metal ions). The capturing member 124 has a closed-loop shape (for example, an annular shape). This makes it possible to bring the water containing metal ions into contact with the capturing member 124 more reliably.

[0060] The capturing member 124 is attached to a holder 128 that is attachable to and detachable from the outer circumferential portion of the conductive sheet 78. In accordance with such a configuration, the capturing member 124 can be easily replaced when deteriorated. In accordance with this feature, it is possible to easily perform maintenance of the differential pressure electrolysis cell 10.

[0061] The holder 128 has a closed-loop perimeter (for example, an annular shape). The holder 128 may be divided into a plurality of pieces in the circumferential direction, for example. In this case, it is preferable that the capturing member 124 is also dividable in accordance with the divided structure of the holder 128. Such a holder 128 can be easily attached to and detached from the conductive sheet 78 as compared to the case where the holder 128 is integrally formed in an annular shape. The structure for attaching and detaching the holder 128 to and from the outer circumferential portion of the conductive sheet 78 may be, for example, a fitting structure, but any measure may be adopted as appropriate.

[0062] As shown in FIG. 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, and thus the capturing member 124 can be replaced more easily. The lubricating member 129 has a closed-loop perimeter (for example, an annular shape). The lubricating member 129 is made of, for example, a fluoro resin having a relatively excellent sliding ability, 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 with a resin material, for example.

[0063] As shown in FIGS. 3 to 5, a guide groove 130 is formed in the upper surface 78a of the conductive sheet 78 to guide water flowing down on the conductive sheet 78 from the spring member 80 to the outer circumferential recess 126. Thus, the guide groove 130 allows water flowing down from the spring member 80 to the conductive sheet 78 to smoothly flow out to the outer circumferential recess 126.

[0064] The guide groove 130 includes a plurality of closed-loop grooves 132 and a plurality of radial grooves 134. Each of the closed-loop grooves 132 has an annular shape. The plurality of closed-loop grooves 132 are arranged under the plurality of claws 94. In this arrangement, water flowing down from the plurality of claws 94 can be received by the closed-loop grooves 132.

[0065] The width of each of the closed-loop grooves 132 can be set as appropriate. In the present embodiment, the plurality of closed-loop grooves 132 include a first closed-loop groove 136, a second closed-loop groove 138, a third closed-loop groove 140, and a fourth closed-loop groove 142.

[0066] As shown in FIG. 3, the first closed-loop groove 136 and the second closed-loop groove 138 are arranged under the inner claw group 112. The first closed-loop groove 136 is arranged under the roots 116a of the plurality of first inner claws 116. The second closed-loop groove 138 is arranged under the roots 118a of the plurality of second inner claws 118. The third closed-loop groove 140 and the fourth closed-loop groove 142 are arranged under the outer claw group 114. The third closed-loop groove 140 is arranged under the roots 120a of the plurality of first outer claws 120. The fourth closed-loop groove 142 is arranged under the roots 122a of the plurality of second outer claws 122. The number, position, size, shape, and the like of the closed-loop grooves 132 may be adopted as appropriate.

[0067] As shown in FIG. 4, the plurality of radial grooves 134 are arranged at intervals in the circumferential direction of the conductive sheet 78. In the present embodiment, eight radial grooves 134 are formed in the upper surface 78a of the conductive sheet 78. Each of the radial grooves 134 extends along the radial direction of the conductive sheet 78. In this arrangement, water flowing down from the spring member 80 to the conductive sheet 78 can be quickly guided to the outer circumferential recess 126 through the radial grooves 134.

[0068] As shown in FIG. 5, the radial grooves 134 are formed such that the groove depth increases radially outward in the conductive sheet 78. In this case, water in the radial grooves 134 easily flows to the outer circumferential recess 126. Each of the radial grooves 134 communicates with the plurality of closed-loop grooves 132 (see FIG. 4). This allows the water received by the closed-loop grooves 132 to flow into the radial grooves 134.

[0069] To be more specific, each of the radial grooves 134 includes a first groove section 134a, a second groove section 134b, a third groove section 134c, and a fourth groove section 134d. The first groove section 134a extends so as to connect the first closed-loop groove 136 and the second closed-loop groove 138. The second groove section 134b extends so as to connect the second closed-loop groove 138 and the third closed-loop groove 140. The groove depth of the second groove section 134b is greater than the groove depth of the first groove section 134a. The third groove section 134c extends so as to connect the third closed-loop groove 140 and the fourth closed-loop groove 142. The groove depth of the third groove section 134c is greater than the groove depth of the second groove section 134b. The fourth groove section 134d extends so as to connect the fourth closed-loop groove 142 and the outer circumferential recess 126. The groove depth of the fourth groove section 134d is greater than the groove depth of the third groove section 134c. The depth of the outer circumferential recess 126 is greater than the groove depth of the fourth groove section 134d.

[0070] The groove bottom surface of each of the first groove section 134a, the second groove section 134b, the third groove section 134c, and the fourth groove section 134d is a horizontal surface, but may be a surface inclined downward radially outward. When such an inclined surface is adopted, water (liquid water) in the radial grooves 134 can be more smoothly guided to the outer circumferential recess 126. The groove bottom surface of the radial groove 134 is not limited to the example formed in a stepped shape, and may be a surface continuously inclined downward from the first closed-loop groove 136 to the outer circumferential recess 126. The number, position, size, shape, and the like of the radial grooves 134 may be adopted as appropriate.

[0071] Next, basic operations of the differential pressure electrolysis stack 14 according to the present embodiment will be briefly described. Here, the differential pressure electrolysis stack 14 that generates oxygen gas and hydrogen gas by electrolyzing water will be described as an example.

[0072] As shown in FIGS. 1 and 2, water (electrolysis fluid) is supplied to the fluid inlet 28 of the differential pressure electrolysis stack 14 by a water pump (not shown), and electrical currents are supplied to the first current collector 60 and the second current collector 74 of each differential pressure electrolysis cell 10 from the electrolysis power supply 22. The water supplied to the fluid inlet 28 is guided to the first electrode catalyst layer 50 through the fluid supply passage 34 and the supply flow path 66.

[0073] In this case, water is electrolyzed in the membrane electrode assembly 40, and hydrogen gas is generated in the first electrode catalyst layer 50 and oxygen gas is generated in the second electrode catalyst layer 52. The fluid containing the hydrogen gas generated in the first electrode catalyst layer 50 and the water that has not been electrolyzed is discharged to the outside of the differential pressure electrolysis stack 14 through the discharge flow path 68, the fluid discharge passage 36, and the fluid outlet 30. The oxygen gas generated in the second electrode catalyst layer 52 is guided to the product gas discharge passage 38 through a space between the membrane electrode assembly 40 and the second metal separator 44 (hereinafter, may be referred to as a “product gas accommodation chamber 144”) and grooves (not shown) of the second inner peripheral member 82. The oxygen gas guided to the product gas discharge passage 38 is discharged from the product gas outlet 32 to the product gas lead-out path 16.

[0074] The product gas lead-out path 16 is provided with the back pressure valve 18. Therefore, the oxygen gas generated in the second electrode catalyst layer 52 is held back by the back pressure valve 18. In accordance with this manner, it is possible to make the pressure of the oxygen gas (product gas) generated at the second electrode catalyst layer 52 higher than the pressure of the water (electrolysis fluid) supplied to the first electrode catalyst layer 50. That is, the pressure of the oxygen gas in the product gas accommodation chamber 144 becomes higher than the pressure of the water supplied to the first electrode catalyst layer 50. Thereafter, the back pressure valve 18 is opened, and the tank 20 is filled with the high-pressure oxygen gas.

[0075] In the present embodiment, the spring member 80 is in line contact with the lower surface 44a of the second metal separator 44. Therefore, the coating is likely to peel off from the position at which the spring member 80 contacts the second metal separator 44. In addition, when oxygen gas is generated in the second electrode catalyst layer 52, the portion at which metal is exposed is likely to corrode, and thus metal ions are likely to be eluted from the metal exposed portion. Even when hydrogen gas is generated in the second electrode catalyst layer 52, metal ions may be eluted from the metal exposed portion. Further, in the case where the 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 in the product gas accommodation chamber 144 is likely to increase, and thus the water is likely to condense on the second metal separator 44, the spring member 80, and the like.

[0076] The water droplets containing the metal ions flow downward along the claws 94 of the spring member 80. To be specific, the water droplets on the protruding ends 116b of the first inner claws 116 flow down along the first inner claws 116 to the roots 116a of the first inner claws 116, and then are guided into the first closed-loop groove 136. The water droplets on the protruding ends 120b of the first outer claw 120 flow down along the first outer claws 120 to the roots 120a of the first outer claws 120, and then are guided into the third closed-loop groove 140. The water droplets on the protruding ends 118b of the second inner claws 118 flow down along the second inner claws 118 to the roots 118a of the second inner claws 118, and then are guided into the second closed-loop groove 138. The water droplets on the protruding ends 122b of the second outer claws 122 flow down along the second outer claws 122 to the roots 122a of the second outer claws 122, and then are guided into the fourth closed-loop groove 142.

[0077] The water guided to the first closed-loop groove 136, the second closed-loop groove 138, the third closed-loop groove 140, and the fourth closed-loop groove 142 flows to the outer circumferential recess 126 via the plurality of radial grooves 134. The water flowing into the outer circumferential recess 126 comes into contact with the capturing member 124, and thereby metal ions (cations) contained in the water are captured (removed). Therefore, even if the water from which the metal ions have been removed flows downward and contacts the electrolyte membrane 48, the electrolyte membrane 48 can be prevented from deteriorating.

[0078] That is, according to the present embodiment, water (water containing metal ions) flowing down to the upper surface 78a of the conductive sheet 78 from metal exposed portions of the second metal separator 44 and the spring member 80 can be brought into contact with the capturing member 124 at the outer circumference of the conductive sheet 78. Thus, the metal ions can be captured (removed) by the capturing member 124 before the water containing the metal ions flows down to the electrolyte membrane 48. Therefore, it is possible to suppress deterioration of the electrolyte membrane 48 due to metal ions. According to such a configuration, it is possible to provide a more favorable differential pressure electrolysis cell 10, differential pressure electrolysis stack 14.

[0079] The present embodiment is not limited to the configuration described above. For example, as shown in FIG. 6, the radial grooves 134 may be formed such that the groove depth is constant radially outward in the conductive sheet 78. That is, the radial grooves 134 may extend along a horizontal plane.

[0080] In relation to the above-described embodiment, the following supplementary notes are further disclosed.Supplementary Note 1

[0081] The differential pressure electrolysis cell (10) according to the present disclosure is configured to electrolyze an electrolysis fluid supplied to the first electrode catalyst layer (50) to generate a product gas in the second electrode catalyst layer (52), the product gas having a higher pressure than the electrolysis fluid, the differential pressure electrolysis cell including: the membrane electrode assembly (40) including the electrolyte membrane (48), the first electrode catalyst layer and the second electrode catalyst layer, the first electrode catalyst layer and the second electrode catalyst layer being joined to opposite sides of the electrolyte membrane; the metal separator (44) arranged above the second electrode catalyst layer; the conductive sheet (78) disposed on the current collector (74) positioned between the metal separator and the second electrode catalyst layer; the spring member (80) made of metal, in contact with the metal separator and the conductive sheet, and configured to press the conductive sheet downward; and the capturing member (124) provided on an outer circumferential portion of the conductive sheet and configured to capture cations.

[0082] In this manner, water (water containing metal ions) flowing down on the upper surface of the conductive sheet from metal exposed portions of the metal separator and the spring member can be brought into contact with the capturing member at the outer circumference of the conductive sheet. This allows metal ions to be captured (removed) by the capturing member before the water containing metal ions further flows down to the electrolyte membrane. Therefore, deterioration of the electrolyte membrane due to metal ions can be suppressed. That is, according to such a configuration, a more favorable differential pressure electrolysis cell can be provided.Supplementary Note 2

[0083] In the differential pressure electrolysis cell according to Supplementary Note 1, the outer circumferential recess (126) having a closed-loop shape may be formed in an upper surface (78a) of the conductive sheet, for accommodating the capturing member.

[0084] According to such a configuration, since water containing metal ions can be stored in the recess, the water containing metal ions can be easily brought into contact with the capturing member.Supplementary Note 3

[0085] In the differential pressure electrolysis cell according to Supplementary Note 2, the capturing member may be formed to have a closed-loop shape.

[0086] According to such a configuration, water containing metal ions can be more reliably brought into contact with the capturing member.Supplementary Note 4

[0087] In the differential pressure electrolysis cell according to Supplementary Note 2 or 3, the guide groove (130) may be formed on the upper surface of the conductive sheet, the guide groove being configured to guide, to the outer circumferential recess, water fallen on the conductive sheet from the spring member.

[0088] According to such a configuration, the water flowing down from the spring member to the conductive sheet can be smoothly flowed to the outer circumferential recess by the guide groove.Supplementary Note 5

[0089] In the differential pressure electrolysis cell according to Supplementary Note 4, the guide groove may include the radial groove (134) extending along a radial direction of the conductive sheet.

[0090] In this arrangement, water falling from the spring member to the conductive sheet can be quickly guided to the outer circumferential recess through the radial groove.Supplementary Note 6

[0091] In the differential pressure electrolysis cell according to Supplementary Note 5, the radial groove may be formed to increase a groove depth radially outward in the conductive sheet.

[0092] In this manner, water in the radial groove easily flows to the outer circumferential recess.Supplementary Note 7

[0093] In the differential pressure electrolysis cell according to Supplementary Note 5 or 6, the spring member may include the flat plate portion (92) and the claw (94) that protrudes from the flat plate portion so as to be inclined upward and comes into contact with the metal separator, and the guide groove may be arranged under the claw.

[0094] In accordance with such a configuration, water flowing down along the claw can be received by the guide groove.Supplementary Note 8

[0095] In the differential pressure electrolysis cell according to Supplementary Note 7, a plurality of the claws may be arranged at intervals along a circumferential direction of the flat plate portion, and the guide groove may include the closed-loop groove (132) that is arranged under the plurality of claws arranged along the circumferential direction of the flat plate portion and is in communication with the radial groove.

[0096] In accordance with such a configuration, water flowing down from the plurality of claws can be received by the closed-loop groove. In addition, the water received by the closed-loop groove can be flowed to the radial groove.Supplementary Note 9

[0097] The differential pressure electrolysis cell according to any one of Supplementary Notes 1 to 8 may further include the holder (128) that is attachable to and detachable from the outer circumferential portion of the conductive sheet, and the capturing member may be attached to the holder.

[0098] In accordance with such a configuration, the capturing member can be easily replaced when deteriorated. In accordance with this feature, it is possible to easily perform maintenance of the differential pressure electrolysis cell.Supplementary Note 10

[0099] In the differential pressure electrolysis cell according to Supplementary Note 9, the lubricating member (129) may be interposed between the capturing member and the conductive sheet.

[0100] In accordance with such a configuration, the capturing member can be easily removed from the conductive sheet, and thus the capturing member can be more easily replaced.Supplementary Note 11

[0101] The differential pressure electrolysis stack (14) of the present disclosure is formed of a plurality of the differential pressure electrolysis cells according to any one of Supplementary Note 1 to 10 that are stacked.

[0102] According to such a configuration, it is possible to obtain a differential pressure electrolysis stack that exhibits the effects described in Supplementary Notes 1 to 10. Thus, a more satisfactory differential pressure water electrolysis stack can be obtained.

[0103] Although concerning the present disclosure, a detailed description thereof has been presented above, the present disclosure is not necessarily limited to the individual embodiments described above. These embodiments can be subjected to various additions, substitutions, modifications, partial deletions and the like, within a range that does not depart from the essence and gist of the present disclosure, or alternatively, the spirit and gist of the present disclosure as derived from the contents described in the claims and their equivalents. Further, these embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each of the operations and the order of each of the processes are shown merely as examples, and the present invention is not necessarily limited to these examples. The same applies also in the case that numerical values or mathematical expressions are used in the description of the aforementioned embodiments.

Examples

Embodiment Construction

[0017]A differential pressure electrolysis cell can electrolyze an electrolysis fluid supplied to a first electrode catalyst layer of a membrane electrode assembly to generate a product gas at a pressure higher than the electrolysis fluid in a second electrode catalyst layer of the membrane electrode assembly. In this type of differential pressure electrolysis cell, a metal separator is disposed above the second electrode catalyst layer. A spring member made of metal is arranged between the metal separator and the second electrode catalyst layer, for pressing a current collector toward the second electrode catalyst layer. The metal separator and the spring member are coated, for example, to prevent elution of metal ions (cations).

[0018]However, the coating may peel off from a position at which the spring member contacts the metal separator. In addition, the coating may peel off due to aging deterioration. When water droplets adhere to a portion at which the coating has been peeled o...

Claims

1. A differential pressure electrolysis cell configured to electrolyze an electrolysis fluid supplied to a first electrode catalyst layer to generate a product gas in a second electrode catalyst layer, the product gas having a higher pressure than the electrolysis fluid,the differential pressure electrolysis cell comprising:a membrane electrode assembly including an electrolyte membrane, the first electrode catalyst layer and the second electrode catalyst layer, the first electrode catalyst layer and the second electrode catalyst layer being joined to opposite sides of the electrolyte membrane;a metal separator arranged above the second electrode catalyst layer;a conductive sheet disposed on a current collector positioned between the metal separator and the second electrode catalyst layer;a spring member made of metal, in contact with the metal separator and the conductive sheet, and configured to press the conductive sheet downward; anda capturing member provided on an outer circumferential portion of the conductive sheet and configured to capture cations.

2. The differential pressure electrolysis cell according to claim 1, wherein an outer circumferential recess having a closed-loop shape is formed in an upper surface of the conductive sheet, for accommodating the capturing member.

3. The differential pressure electrolysis cell according to claim 2, wherein the capturing member is formed to have a closed-loop shape.

4. The differential pressure electrolysis cell according to claim 2, wherein a guide groove is formed on the upper surface of the conductive sheet, the guide groove being configured to guide, to the outer circumferential recess, water fallen on the conductive sheet from the spring member.

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

6. The differential pressure electrolysis cell according to claim 5, wherein the radial groove is formed to increase a groove depth radially outward in the conductive sheet.

7. The differential pressure electrolysis cell according to claim 5, whereinthe spring member includes:a flat plate portion; anda claw that protrudes from the flat plate portion so as to be inclined upward and comes into contact with the metal separator, andwherein the guide groove is arranged under the claw.

8. The differential pressure electrolysis cell according to claim 7, whereinthe claw includes a plurality of claws arranged at intervals along a circumferential direction of the flat plate portion, andthe guide groove includes a closed-loop groove that is arranged under the plurality of claws arranged along the circumferential direction of the flat plate portion and is in communication with the radial groove.

9. The differential pressure electrolysis cell according to claim 1, further comprising:a holder that is attachable to and detachable from the outer circumferential portion of the conductive sheet, whereinthe capturing member is attached to the holder.

10. The differential pressure electrolysis cell according to claim 9, further comprising:a lubricating member interposed between the capturing member and the conductive sheet.

11. A differential pressure electrolysis stack, formed of a plurality of the differential pressure electrolysis cells according to claim 1 that are stacked.

Images