Gas diffusion layer and electrolytic bath for electrolyzing water

Abstract

The utility model is applied to the field of hydrogen production by electrolyzing water, and particularly relates to a gas diffusion layer and an electrolytic bath for electrolyzing water. The gas diffusion layer comprises an annular porous structure (1) and a gas transmission channel (2) located in the middle of the annular porous structure. In the prior art, a near-membrane-side silk screen structure is used as a common gas diffusion layer, the near-membrane-side silk screen structure only exists as a catalyst-loaded substrate, and the problem of generated bubble transmission is not considered. Bubbles generated around the catalyst alternately cover the catalyst layer and cannot be quickly diffused and discharged. The annular porous structure can induce bubbles to be transmitted in the gas transmission channel (2), so that a catalyst layer is prevented from being covered, the resistance caused by the bubbles is greatly reduced, and the condition that the bubbles cover the catalyst layer is reduced.

Description

Technical Field

[0001] The utility model is applied to the field of hydrogen production by electrolyzing water, and specifically relates to a gas diffusion layer and an electrolytic cell for electrolyzing water. Background Art

[0002] When the water electrolysis hydrogen production equipment is in working condition, a large number of bubbles are produced by the anode and cathode and remain in the catalyst layer, resulting in the bubbles covering the catalyst layer and shielding the catalytic sites of the catalyst layer during the water electrolysis process; in addition, the bubble resistance is much larger than the solution resistance and the metal resistance. The above two points lead to an increase in the overall cell pressure of the water electrolysis hydrogen production equipment, which in turn leads to an increase in the energy consumption of the water electrolysis equipment during the hydrogen production process.

[0003] In order to solve the above problems, this application is proposed. Summary of the invention

[0004] The present application provides a gas diffusion layer, which includes: an annular porous structure 1 and a gas transmission channel 2 located in the middle of the annular porous structure.

[0005] Preferably, the annular porous structure 1 comprises: a spiral spring-like structure or a plurality of annular structures arranged side by side. Of course, the annular porous structure 1 can also be a multi-layer annular porous structure, or a columnar structure formed by a mesh structure surrounding it.

[0006] A plurality of spiral spring-like structures can be arranged side by side and connected and fixed to each other.

[0007] A plurality of annular structures arranged side by side can also be connected and fixed to each other. The direction of the side by side arrangement is the direction of the gas transmission channel 2.

[0008] A plurality of annular structures arranged side by side may form a row. The gas diffusion layer may comprise a plurality of rows of the above structures.

[0009] The helical spring-like structures may be arranged in one row. The gas diffusion layer may include a plurality of rows of the above structures.

[0010] Preferably, the gas diffusion layer further comprises: a mesh structure 3 located on one side or both sides of the annular porous structure 1 and connected to the annular porous structure 1 .

[0011] Preferably, the connection method is weaving or welding.

[0012] Preferably, the inner diameter of the spiral spring-shaped structure is a constant diameter or variable diameter structure;

[0013] The plurality of annular structures arranged side by side are equal-diameter or variable-diameter structures.

[0014] Preferably, the network structure 3 includes: a first network structure located at one side of the gas transmission channel 2 and a second network structure located at the other side of the gas transmission channel 2, and the porosities of the first network structure and the second network structure are different from each other.

[0015] Preferably, a catalyst layer is provided on the gas diffusion layer.

[0016] The second aspect of the present application provides an electrolytic cell for electrolyzing water, the electrolytic cell comprising: an anode plate, the gas diffusion layer described in the first aspect on the anode side, an ion exchange membrane, the gas diffusion layer described in the first aspect on the cathode side, and a cathode plate.

[0017] The gas diffusion layer of the first aspect on the anode side and the gas diffusion layer of the first aspect on the cathode side are the same as or different from each other.

[0018] Preferably, a catalyst layer is provided on the gas diffusion layer, and / or a catalyst layer is provided on the ion exchange membrane.

[0019] The gas diffusion layer comprises: a mesh structure 3 located on both sides of the annular porous structure 1 and connected to the annular porous structure 1, wherein the side with lower porosity is close to the ion exchange membrane, and the side with higher porosity is close to the electrode plate.

[0020] The gas diffusion layer comprises: a mesh structure 3 located on one side of the annular porous structure 1 and connected to the annular porous structure 1, and one side of the mesh structure 3 is close to the ion exchange membrane.

[0021] The core design idea of ​​the gas diffusion layer of the present application is that there is a hollow part of an annular porous structure that acts as a passage for bubble transmission. Furthermore, the annular porous structure can be woven into a form similar to a woven cloth by longitudinal tiling and cross-linking with transverse metal wires, and the series connection can be multiple. That is, simple weaving on one side, twill weaving on one side, and weaving on both sides with different porosities. In addition, the annular porous structure can be used as one of the structures of the gas diffusion layer, and its two sides can be directly sintered and connected with nickel meshes of different porosities, and the structure does not need to be woven. The cross weaving and nickel mesh on both sides are to improve the contact with the membrane and the electrode plate. The annular porous structure can induce bubbles to be transmitted in the gas transmission channel 2 therein, thereby avoiding covering the catalyst layer, greatly reducing the resistance caused by the bubbles and reducing the situation where the bubbles cover the catalyst layer.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The prior art uses a general gas diffusion layer such as a wire mesh structure near the membrane side. The wire mesh structure near the membrane side only exists as a substrate for catalyst loading, and does not take into account the problem of bubble transmission. The bubbles generated around the catalyst are interspersed and covered on the catalyst layer and cannot be quickly diffused and discharged. The annular porous structure of the present application can induce bubbles to be transmitted in the gas transmission channel 2, thereby avoiding covering the catalyst layer, greatly reducing the resistance caused by bubbles and reducing the situation where bubbles cover the catalyst layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the gas diffusion layer structure of the first embodiment.

[0025] Figure 2 Schematic diagram of the gas diffusion layer structure of the second embodiment.

[0026] Figure 3 Schematic diagram of the gas diffusion layer structure of the third embodiment.

[0027] Figure 4 Schematic diagram of the gas diffusion layer structure of the fourth embodiment.

[0028] Figure 5 Schematic diagram of the gas diffusion layer structure of the fifth embodiment.

[0029] Figure 6 Schematic diagram of the gas diffusion layer structure of the sixth embodiment.

[0030] Figure 7 Schematic diagram of the gas diffusion layer structure of the seventh embodiment.

[0031] Figure 8 Shown is Figure 7 The schematic diagram of bubble generation and bubble flow direction in the gas diffusion layer under actual working conditions is shown.

[0032] Fig. 9 This is a schematic diagram of the structure of an electrolytic cell for electrolyzing water in the present application.

[0033] Fig.10 The figure is a structural diagram of an electrolytic cell containing a general gas diffusion layer in the prior art.

[0034] List of reference numerals:

[0035] 1. Annular porous structure, 2. Gas transmission channel, 3. Net structure. 01. Anode plate, 02. Anode side gas diffusion layer, 03. Ion exchange membrane, 04. Cathode catalyst layer, 05. Cathode side gas diffusion layer, 06. Cathode plate, 12. Anode side general gas diffusion layer, 14. Anode catalyst layer, 15. Cathode side general gas diffusion layer. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below in conjunction with embodiments.

[0037] Those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the art or the product specifications are used. If the manufacturer of the materials or equipment used is not specified, they are all conventional products that can be purchased.

[0038] Those skilled in the art will appreciate that, unless expressly stated otherwise, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when we refer to an element as being "connected" to another element, it may be directly connected to the other element, or there may be intermediate elements. In addition, the "connection" used herein may include wireless connections.

[0039] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two. The terms "inside", "upper", "lower", etc., indicating positions or state relationships, are based on the positions or state relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operate in a specific position, and therefore cannot be understood as limiting the present invention.

[0040] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "provided with" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention will be understood according to specific circumstances.

[0041] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0042] A gas diffusion layer with directional transmission function, the gas diffusion layer comprises: an annular porous structure 1 and a gas transmission channel 2 located in the middle of the annular porous structure 1.

[0043] The annular porous structure 1 can be an annular structure similar to a spring, or multiple annular structures arranged side by side. The annular structure can be a circular ring or other types of rings. The spacing between the annular structures can be equal or unequal.

[0044] Preferably, the gas diffusion layer further comprises: a mesh structure 3 located on one side or both sides of the annular porous structure 1 and connected to the annular porous structure 1 .

[0045] The mesh structure 3 may be a single-layer or double-layer woven mesh.

[0046] The metal wire used for the woven mesh can be directly combined with the annular porous structure 1 by weaving, or can be connected together by sintering.

[0047] When weaving or sintering is performed, it can be performed on one side or on both sides, or it can be connected by weaving and sintering on both sides respectively.

[0048] When weaving, there are warps and wefts. A warp is generally arranged in the axial direction where the annular porous structure 1 is located, and the metal wire woven with it is used as the weft to combine the warp, the weft and the annular porous structure together. The metal wire used as the weft can be woven with the warp at a certain angle, wherein the angle formed by the warp and the weft is less than or equal to 90° and greater than 0°.

[0049] When weaving, considering the contact between the annular porous structure 1, the gas transmission channel 2 and the electrode and the ion exchange membrane, only single-side weaving or different weaving densities on both sides can be used, that is, more / fewer metal wires as warp and weft are added per unit area for weaving.

[0050] During sintering connection, considering the contact between the annular porous structure 1, the gas transmission channel 2, the electrode plate and the ion exchange membrane, single-side sintering or sintering on both sides using metal meshes of different mesh sizes can be performed.

[0051] When selecting a mesh structure 3 in which one side is sintered and the other side is woven for connection, considering gas transmission and contact with the electrode plate and the membrane, a structure in which the woven side is denser and the sintered side is sparser or a structure in which the sintered side is denser and the woven side is sparser can be adopted.

[0052] Figure 1The schematic diagram of the gas diffusion layer structure of the first embodiment. The gas diffusion layer includes: an annular porous structure 1 and a gas transmission channel 2 located in the middle of the annular porous structure 1. The annular porous structure 1 is a plurality of spring-like annular structures. When in use, the two sides of the gas diffusion layer contact the diaphragm and the electrode plate respectively, and the gas transmission channel 2 in the middle of the spring-like annular structure serves as a bubble passage, which plays a role in directional transmission of bubbles.

[0053] Figure 2 Schematic diagram of the gas diffusion layer structure of the second embodiment. Figure 2 In order to make the gas diffusion layer and the catalyst layer (or the diaphragm, which depends on whether it is the assembly method of CCS or CCM) contact more closely, a single-sided mesh structure 3 is formed by simple weaving of metal wires (nickel wires, stainless steel wires, etc.). When in use, the single-sided mesh structure 3 is in contact with the diaphragm side to ensure good contact between the gas diffusion layer and the diaphragm. The weaving small angle of the warp and weft of the mesh structure 3 is ≤90°. When the weaving small angle is equal to 90°, it is a grid mesh weaving form (described as simple weaving in the previous text); when the weaving small angle is less than 90°, the original grid mesh structure becomes a parallelogram mesh structure (described as twill weaving in the previous text).

[0054] Figure 3 Schematic diagram of the gas diffusion layer structure of the third embodiment. The gas diffusion layer further includes: a mesh structure 3 located on both sides of the annular porous structure 1 and connected to the annular porous structure 1. Specifically, the mesh structure 3 includes: a first mesh structure located on one side of the gas transmission channel 2 and a second mesh structure located on the other side of the gas transmission channel 2, and the porosity of the first mesh structure and the second mesh structure are different from each other. In other words, Figure 2 On the basis of single-side weaving, in order to ensure that the gas diffusion layer is further well connected with the electrode base, ensure the electron transmission efficiency, reduce the overall resistance, and thus reduce the cell pressure of the electrolytic cell, a simple weaving or twill weaving is also performed on the other side of the annular porous structure 1, but the weaving density is relatively low compared to the diaphragm side. Figure 3 , so that it forms a porosity difference with the woven mesh on the side of the diaphragm, that is, the porosity of the woven mesh of the diaphragm is less than that of the woven mesh on the plate side. This makes the bubbles more inclined to break away from the woven mesh with smaller porosity on the diaphragm layer and enter the gas transmission channel 2. The reason is that the hydroxyl concentration on the diaphragm side is higher, which is the efficient reaction area. By reducing the porosity, the specific surface area is increased, the reactive area is increased, and the efficient reaction area is fully utilized. At the same time, the difference between high and low porosity will form an asymmetric additional pressure on the bubbles, prompting the bubbles to move to the high porosity space.

[0055] In addition, Figure 1 The annular porous structure 1 and the nickel mesh structure as the mesh structure 3 are sintered together to form a similar Figure 2 , Figure 3 (like Figure 4 , 5 ) structure. The spring-like structure can be replaced by a side-by-side ring structure, such as Figure 6 . Figure 4 Schematic diagram of the gas diffusion layer structure of the fourth embodiment. Figure 5 Schematic diagram of the gas diffusion layer structure of the fifth embodiment. Figure 6 Schematic diagram of the gas diffusion layer structure of the sixth embodiment.

[0056] During the above weaving or sintering process, the annular porous structure 1 is reinforced.

[0057] The woven type gas diffusion layer between the mesh structure 3 and the annular porous structure 1 has a certain elasticity due to the deformation margin of its woven structure. The sintered type gas diffusion layer loses a certain elasticity due to the point-to-point sintering of the mesh structure 3 and the annular porous structure 1, but has a higher structural strength.

[0058] In addition, the advantages of weaving and sintering can be combined to ensure a high structural strength while making it elastic. This structure can be selected according to the needs to select the combination method of the two sides of the gas transmission channel 2 (one side is woven and the other side is sintered, such as Figure 7 ) to be applicable to more application scenarios. Figure 7 Schematic diagram of the gas diffusion layer structure of the seventh embodiment.

[0059] Figure 8 Shown is Figure 7 The schematic diagram of the gas diffusion layer in actual working conditions and the flow direction of bubbles is shown. The catalyst is attached to the gas diffusion layer, and bubbles are generated and grown on the gas diffusion layer. After fusion, they enter the gas transmission channel 2 and accelerate the overflow. The arrow points upward.

[0060] like Fig. 9 , an electrolytic cell for electrolyzing water, the electrolytic cell comprising:

[0061] Anode plate 01,

[0062] The anode-side gas diffusion layer 02 described in any one of the above items comprises an anode catalyst layer;

[0063] The ion exchange membrane 03 contains a cathode catalyst layer 04 on the side adjacent to the cathode plate;

[0064] The cathode side gas diffusion layer 05 as described in any one of the above items;

[0065] Cathode plate 06.

[0066] The above electrolyzer has an anode end assembly method of CCS and a cathode end assembly method of CCM.

[0067] like Fig.10 The structure diagram of an electrolytic cell containing a general gas diffusion layer in the prior art, wherein the electrolytic cell comprises:

[0068] Anode plate 01;

[0069] A general gas diffusion layer 12 on the anode side, such as nickel foam or nickel mesh;

[0070] An ion exchange membrane 03, which contains an anode catalyst layer 14 adjacent to the anode side;

[0071] The cathode side generally has a gas diffusion layer 15, which is nickel foam or nickel mesh, and contains a cathode catalyst layer;

[0072] Cathode plate 06.

[0073] The above electrolyzer has a positive terminal assembly method of CCM and a negative terminal assembly method of CCS.

[0074] Fig. 9 and Fig.10 It can be seen that the prior art uses a general gas diffusion layer such as a near-membrane wire mesh structure, which only exists as a substrate for catalyst loading and does not take into account the problem of bubble transmission. The bubbles generated around the catalyst are interspersed and covered on the catalyst layer and cannot be quickly diffused and discharged.

[0075] In the gas diffusion layer of the present application, the bubbles generated around the catalyst can be desorbed into the gas transmission channel 2 in the middle of the gas diffusion layer and quickly diffused and discharged, avoiding the risk of covering the catalytic layer and shielding the catalytic sites of the catalyst layer. After the bubbles are quickly diffused and discharged, the excessive mass transfer resistance caused by the bubbles is reduced, effectively reducing the risk of increased cell pressure due to increasing the size of the water electrolysis equipment.

[0076] Example 1: Alkaline tank electrolysis of water

[0077] Microporous membranes are generally used in alkaline electrolytic cells. Such membranes are relatively thick and have relatively high strength. Therefore, based on this property, a gas diffusion layer with relatively high strength can be selected as the current collector of the alkaline electrolytic cell.

[0078] According to the gas production characteristics of the anode and cathode and the different contacts between the electrolytic cell plates and the membrane, different gas diffusion layers can be selected as current collectors. Figure 4 or Figure 5 The current collector shown serves as its gas diffusion layer, which has certain advantages. Figure 4 and Figure 5 Both are gas diffusion layers formed by sintering.

[0079] Preferably, in order to ensure effective gas transmission, when installing the gas diffusion layer, a spring-like structure (such as Figure 1 It should be placed vertically.

[0080] Preferably, in order to ensure good contact with the membrane end in the electrolyzer to reduce resistance, it is necessary to Figure 4 The mesh structure 3 side of the structure is placed close to the membrane side, and the side without the mesh structure 3 is placed close to the electrode plate.

[0081] Preferably, in order to ensure good contact with the membrane end in the electrolyzer to reduce resistance and to establish gas transmission differences, it is necessary to Figure 5 In the structure, the side with a higher metal mesh number is placed close to the membrane side, and the side with a lower metal mesh number is placed close to the electrode plate.

[0082] Because the annular structure of the middle spring is the main structure of the gas transmission channel 2, the structure can be directly simplified to use the annular structure and nickel meshes of different meshes for sintering connection, such as Figure 6 .

[0083] Preferably, in order to ensure good contact with the membrane end in the electrolyzer to reduce resistance and to establish gas transmission differences, it is necessary to Figure 6 The side with a higher metal mesh number of the structure is placed close to the membrane side, and the side with a lower metal mesh number is placed close to the electrode plate.

[0084] Example 2 Proton (anion) exchange membrane water electrolysis

[0085] Proton (anion) exchange membranes are generally used in proton (anion) exchange membranes (the above two membranes are collectively referred to as ion exchange membranes below). These two ion exchange membranes are relatively thin and have relatively low strength. Therefore, based on this property, a gas diffusion layer with relatively high strength and certain elasticity can be selected as the current collector of the ion exchange membrane electrolysis water electrolyzer.

[0086] According to the gas production characteristics of the anode and cathode and the different contacts between the electrolytic cell plates and the membrane, different gas diffusion layers can be selected as current collectors. Figure 2 or Figure 3 The current collector shown as the gas diffusion layer has certain advantages because its woven structure has certain elasticity. Figure 2 and Figure 3 Both are gas diffusion layers formed by weaving.

[0087] Preferably, in order to ensure effective gas transmission, when installing the gas diffusion layer, a spring-like structure (such as Figure 1 It should be placed vertically.

[0088] Preferably, in order to ensure good contact with the membrane end in the electrolyzer to reduce resistance, it is necessary to Figure 2 Two sides of the structure are placed close to the membrane side, and one side is placed close to the electrode plate.

[0089] Preferably, in order to ensure good contact with the membrane end in the electrolyzer to reduce resistance and to establish gas transmission differences, it is necessary to Figure 3 The side with a higher metal mesh number of the structure is placed close to the membrane side, and the side with a lower metal mesh number is placed close to the electrode plate.

[0090] In order to simplify production and reduce costs, and to improve strength and elasticity to a certain extent, the advantages of nickel mesh sintering and wire weaving are combined and the following is proposed: Figure 7 The gas diffusion layer shown. A gas diffusion layer with gas passages woven on one side and sintered on the other side. Here, the woven side is relatively sparse, while the nickel mesh on the sintered side is relatively dense. The density can be adjusted according to the needs.

[0091] Preferably, Figure 7 The side shown uses a denser metal wire weave close to the ion exchange membrane side, while the other side uses a nickel mesh sintered side. A relatively sparse nickel mesh can be used close to the electrode side to ensure effective gas transmission and good contact between the gas diffusion layer and the electrode plate and the membrane.

Claims

1. A gas diffusion layer, characterized in that: The gas diffusion layer comprises: an annular porous structure (1) and a gas transmission channel (2) located in the middle of the annular porous structure.

2. The gas diffusion layer according to claim 1, characterized in that The annular porous structure (1) comprises: a helical spring-like structure or a plurality of annular structures arranged side by side.

3. The gas diffusion layer according to claim 2, characterized in that: The gas diffusion layer further comprises: a mesh structure (3) located on one side or both sides of the annular porous structure (1) and connected to the annular porous structure (1).

4. The gas diffusion layer according to claim 3, characterized in that: The connection method is weaving or welding.

5. The gas diffusion layer according to claim 2, characterized in that: The inner diameter of the spiral spring-shaped structure is a constant diameter or variable diameter structure; The plurality of annular structures arranged side by side are equal-diameter or variable-diameter structures.

6. The gas diffusion layer according to claim 3, characterized in that: The mesh structure (3) comprises: a first mesh structure located on one side of the gas transmission channel (2) and a second mesh structure located on the other side of the gas transmission channel (2), and the porosities of the first mesh structure and the second mesh structure are different from each other.

7. The gas diffusion layer according to claim 3, characterized in that: The gas diffusion layer has a catalyst layer thereon.

8. An electrolytic cell for electrolyzing water, characterized in that: The electrolytic cell comprises: an anode plate, the gas diffusion layer as claimed in claim 1 on the anode side, an ion exchange membrane, and the gas diffusion layer as claimed in claim 1 on the cathode side, and a cathode plate.

9. The electrolytic cell for electrolyzing water according to claim 8, characterized in that: The gas diffusion layer has a catalyst layer thereon, and / or the ion exchange membrane has a catalyst layer thereon.

10. The electrolytic cell for electrolyzing water according to claim 8, characterized in that: The gas diffusion layer described in claim 1 comprises: a mesh structure (3) located on both sides of the annular porous structure (1) and connected to the annular porous structure (1), wherein the side of the mesh structure (3) with a lower porosity is close to the ion exchange membrane, and the side of the mesh structure (3) with a higher porosity is close to the electrode plate.

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