Bipolar plate assembly of PEM electrolytic bath

Abstract

The invention belongs to the technical field of PEM electrolytic baths, and relates to a bipolar plate assembly of a PEM electrolytic bath. A flow channel area (3) is arranged in the middle of the bipolar plate (1), each side surface of the flow channel area (3) comprises a plurality of concave flow channel concave parts (9) and a plurality of convex flow channel convex parts (10), a plurality of bent structures (14) are arranged on the inner walls of the flow channel concave parts (9), and a pure water inlet (4), a water oxygen outlet (5), a first hydrogen outlet (6) and a second hydrogen outlet (7) are formed in the positions, close to the flow channel area (3), of the bipolar plate (1). The pure water inlet (4) is located at one end of the multi-channel concave part (9) of the channel area (3), and the water oxygen outlet (5) is located at the other end of the multi-channel concave part (9). According to the bipolar plate assembly of the PEM electrolytic bath, the cost of early-stage processing and later-stage surface treatment of the bipolar plate can be greatly reduced, convenience is provided for installation of the bipolar plate, the contact resistance between the bipolar plate and a composite diffusion layer is reduced, and the service life of the bipolar plate is prolonged. And the hydrogen production performance of the PEM electrolytic cell is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of PEM electrolyzers, and more specifically, relates to a bipolar plate assembly of a PEM electrolyzer. Background Art

[0002] The PEM water electrolyzer uses PEM as electrolyte and pure water as reactant. In addition, the hydrogen permeability of PEM is low, and the hydrogen produced is of high purity, and only water vapor needs to be removed; the electrolyzer adopts a zero-spacing structure, with low ohmic resistance, which significantly improves the overall efficiency of the electrolysis process, and is more compact; the pressure control range is large, and the hydrogen output pressure can reach several megapascals, which can adapt to the rapidly changing renewable energy power input. Therefore, PEM water electrolysis hydrogen production is a green hydrogen production technology path with great development prospects. The disadvantages of the existing technology are: PEM water electrolysis hydrogen production technology has the advantages of high current density, high hydrogen purity, and fast response speed. PEM water electrolysis hydrogen production technology is also more efficient, but because the PEM electrolyzer needs to operate in a strongly acidic and highly oxidizing working environment, the equipment is more dependent on expensive metal materials such as iridium, platinum, titanium, etc., resulting in excessive costs. Among them, bipolar plates account for about 53% of the cost of the electrolyzer. Therefore, the development of low-cost and high-performance bipolar plates is crucial to the commercial success of PEM water electrolysis hydrogen production technology. At present, the industry's manufacturing of bipolar plates mainly revolves around the etching technology route. The biggest advantage of the etching process is the timely delivery and high cost-effectiveness during small-batch customization. It plays an obvious role in the research and development stage of PEM hydrogen production equipment. However, the bipolar plate of the PEM electrolyzer has a "one plate, two fields" structure. The plate required for the etching process is relatively thick, and the delivery timeliness is lacking during large-scale customization.

[0003] In the prior art, there is a technology named "a proton exchange membrane water electrolyzer structure and anode plate" and the publication (announcement) number is "CN113463107A", which discloses a proton exchange membrane water electrolyzer structure and anode plate, wherein the proton exchange membrane water electrolyzer structure includes an anode plate, an anode diffusion layer, a CCM membrane electrode, a cathode diffusion layer and a cathode plate. The anode plate includes a fluid distribution area, an arc flow channel reaction area and a point flow field reaction area; the anode plate fluid distribution area is an arc-shaped stepped flow field area with both sides gradually shrinking toward the center of the circle, and an elliptical distribution structure is arranged in the middle of the area, the anode plate near the water inlet is an arc flow channel reaction area, and the end area of ​​the flow field is a point flow field reaction area. The present invention ensures uniform diffusion of reaction water in each flow channel after entering the flow field by setting a quasi-elliptical distribution structure in the fluid distribution area; reduces the flow resistance of reaction water and improves the transmission efficiency of reaction water by using the arc-shaped flow channel of the arc-shaped flow field; reduces the formation of bubble embolism by using the lattice structure of the point-shaped flow field, enhances the mass transfer capacity of reaction water, and thus improves the performance of the electrolytic cell.

[0004] However, this technology does not involve the technical problems and technical solutions of the present application. Summary of the invention

[0005] The technical problem to be solved by the present invention is: in view of the shortcomings of the prior art, a PEM electrolyzer bipolar plate assembly is provided which has a simple structure and can significantly reduce the cost of the early processing and later surface treatment of the bipolar plate, which not only facilitates the installation of the bipolar plate, but also reduces the contact resistance between the bipolar plate and the composite diffusion layer, thereby improving the hydrogen production performance of the PEM electrolyzer.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is:

[0007] The present invention discloses a bipolar plate assembly for a PEM electrolyzer. The bipolar plate is a structure made by stamping. A flow channel area is arranged in the middle of the bipolar plate. The surface of each side of the flow channel area includes a plurality of recessed flow channel recesses and a plurality of protruding flow channel protrusions. The inner wall of the flow channel recess is provided with a plurality of bending structures. A pure water inlet, a water-oxygen outlet, a first hydrogen outlet and a second hydrogen outlet are arranged near the flow channel area on the bipolar plate. The pure water inlet is located at one end of the plurality of flow channel recesses in the flow channel area, the water-oxygen outlet is located at the other end of the plurality of flow channel recesses in the flow channel area, the first hydrogen outlet is located at one side of the flow channel area, and the second hydrogen outlet is located at the other side of the flow channel area. A first composite diffusion layer is arranged on the surface of one end of the flow channel area, and a second composite diffusion layer is arranged on the surface of the other side of the flow channel area.

[0008] A membrane electrode is arranged on the outer surface of the first composite diffusion layer, and a membrane electrode is arranged on the outer surface of the second composite diffusion layer.

[0009] Positioning holes are arranged on the bipolar plate.

[0010] The first composite diffusion layer comprises a porous mesh and titanium felt, and the porous mesh on the inner surface of the first composite diffusion layer is bonded to the surface of one end of the flow channel area of ​​the bipolar plate; the second composite diffusion layer comprises a porous mesh and titanium felt, and the porous mesh on the inner surface of the second composite diffusion layer is bonded to the surface of one end of the flow channel area of ​​the bipolar plate.

[0011] Positioning pin holes are arranged on the bipolar plate.

[0012] Adjacent bipolar plates are positioned by bolts passing through the positioning holes.

[0013] The porous mesh plate of the first composite diffusion layer is connected to the bipolar plate by pressure welding; the porous mesh plate of the second composite diffusion layer is connected to the bipolar plate by pressure welding.

[0014] The pure water inlet and the water-oxygen outlet on the bipolar plate span the flow channel area. Pure water enters the flow channel recess on the surface of one side of the flow channel area through the pure water inlet to perform a hydrogen production reaction. The unreacted pure water and the generated oxygen in the hydrogen production process are discharged from the flow channel recess through the water-oxygen outlet.

[0015] The first hydrogen outlet and the second hydrogen outlet on the bipolar plate span the flow channel area, and the hydrogen generated by the hydrogen production reaction is discharged from the first hydrogen outlet and the second hydrogen outlet through the flow channel recess on the other side surface of the flow channel area.

[0016] The bipolar plate and the composite diffusion layer are connected together through a pressure welding process.

[0017] The bipolar plate is a titanium thin plate with a thickness of 0.3 mm to 0.5 mm.

[0018] The technical solution of the present invention is adopted, and the working principle and beneficial effects are as follows:

[0019] The bipolar plate assembly of the PEM electrolyzer described in the present invention is structured such that the bipolar plate is made by a stamping process, and then the bipolar plate and the composite diffusion layer are integrated by a pressure welding process. The central area of ​​the bipolar plate is a stamped flow channel area, and the flow channel area includes a plurality of parallel flow channel recesses. The flow channel area on one side of the bipolar plate is provided with a plurality of parallel flow channel recesses, and the flow channel area on the other side of the bipolar plate is provided with a plurality of parallel flow channel recesses, forming a dual flow channel structure. Different flow channels are used to connect different ports and to flow different media. Each flow channel recess adopts a multi-segment twill structure, that is, a plurality of bending structures are provided on the inner wall of the flow channel recess, and the inclination angle of each flow segment of each flow channel recess is set at 5 to 10 degrees. In this way, more contact area with the composite titanium felt and more uniform flow field distribution can be achieved. Multiple flow channel concave parts and multiple flow channel convex parts are arranged on each side surface of the flow channel area. The flow channel concave part on one side surface and the adjacent flow channel concave part on the other side surface are structures where the concave and convex surfaces are connected. The flow channel concave part is a conveying channel, which conveys pure water and oxygen generated by electrochemical reaction on the anode side of the flow channel concave part, and conveys hydrogen generated by electrochemical reaction on the cathode side. The flow channel convex part is the support surface of the central area of ​​the stamped bipolar plate, and is also the welding surface of the composite diffusion layer. The bipolar plate is provided with a pure water inlet and a water oxygen outlet, both of which span the entire flow channel area. Pure water is evenly distributed to one end of the conveying channel on one side surface of the bipolar plate through the pure water inlet. The water oxygen outlet is located on the opposite side of the conveying channel. Unreacted pure water and generated oxygen are evenly discharged through the water oxygen outlet. The bipolar plate is provided with a first hydrogen outlet and a second hydrogen outlet across the delivery channel on the other side of the bipolar plate and perpendicular to the flow direction of the channel. The generated hydrogen is transported to the flow channel recess through the composite diffusion layer and then discharged evenly through the first hydrogen outlet and the second hydrogen outlet, thereby reliably realizing hydrogen production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The following is a brief description of the contents and symbols in the drawings of this specification:

[0021] Figure 1A schematic diagram of the structure of the bipolar plate of the bipolar plate assembly of the PEM electrolyzer according to the present invention;

[0022] Figure 2 A schematic cross-sectional view of the bipolar plate of the bipolar plate assembly of the PEM electrolyzer according to the present invention;

[0023] Figure 3 It is a schematic structural diagram of the composite diffusion layer of the bipolar plate assembly of the PEM electrolyzer according to the present invention;

[0024] Figure 4 A schematic diagram of the top view of the flow channel region of the bipolar plate of the bipolar plate assembly of the PEM electrolyzer according to the present invention;

[0025] Figure 5 It is a cross-sectional structural schematic diagram of the bipolar plate assembly of the PEM electrolyzer according to the present invention;

[0026] The markings in the accompanying drawings are respectively: 1. bipolar plate; 2. connecting hole; 3. flow channel area; 4. pure water inlet; 5. water oxygen outlet; 6. first hydrogen outlet; 7. second hydrogen outlet; 8. positioning pin hole; 9. flow channel recess; 10. flow channel protrusion; 11. porous mesh plate; 12. titanium felt; 13. first composite diffusion layer; 14. bending structure; 15. second composite diffusion layer. DETAILED DESCRIPTION

[0027] The following is a further detailed description of the specific implementation of the present invention, such as the shape, structure, mutual position and connection relationship between the various components involved, the function and working principle of each part, etc., through the description of the embodiments with reference to the accompanying drawings:

[0028] As attached Figure 1 -Attached Figure 5 As shown, the present invention is a bipolar plate assembly for a PEM electrolyzer, the bipolar plate 1 is a stamped structure, a flow channel region 3 is arranged in the middle of the bipolar plate 1, each side surface of the flow channel region 3 includes multiple concave flow channel recesses 9 and multiple convex flow channel protrusions 10, and multiple bending structures 14 are arranged on the inner wall of the flow channel recess 9. A pure water inlet 4, a water oxygen outlet 5, a first hydrogen outlet 6 and a second hydrogen outlet 7 are arranged near the flow channel region 3 on the bipolar plate 1. The pure water inlet 4 is located at one end of the multiple flow channel recesses 9 of the flow channel region 3, the water oxygen outlet 5 is located at the other end of the multiple flow channel recesses 9 of the flow channel region 3, the first hydrogen outlet 6 is located at one side of the flow channel region 3, and the second hydrogen outlet 7 is located at the other side of the flow channel region 3. A first composite diffusion layer 13 is arranged on the surface of one end of the flow channel region 3, and a second composite diffusion layer 15 is arranged on the surface of the other side of the flow channel region 3. The above structure proposes an improved technical solution to address the deficiencies in the prior art. When the structure is set, the bipolar plate is made by a stamping process, and then the bipolar plate and the composite diffusion layer are integrated by a pressure welding process. The central area of ​​the bipolar plate is a stamped flow channel area 3, such as Figure 1 As shown, the flow channel area includes multiple parallel flow channel recesses 9. The flow channel area on one side of the bipolar plate is provided with multiple parallel flow channel recesses 9, and the flow channel area on the other side of the bipolar plate is provided with multiple parallel flow channel recesses 9, forming a double flow channel structure. Different flow channels are used to connect different ports and to flow different media. Each flow channel recess 9 adopts a multi-segment twill structure, that is, multiple bending structures 14 are provided on the inner wall of the flow channel recess 9, and the inclination angle of each flow segment of each flow channel recess 9 is set at 5 to 10 degrees. In this way, more contact area with the composite titanium felt and more uniform flow field distribution can be achieved. Multiple flow channel concave portions 9 and multiple flow channel convex portions 10 are arranged on each side surface of the flow channel region 3. The flow channel concave portion 9 on one side surface and the adjacent flow channel concave portion 9 on the other side surface are structures where the concave and convex surfaces are connected. The flow channel concave portion 9 is a conveying channel, which conveys pure water and oxygen generated by electrochemical reaction on the anode side of the flow channel concave portion 9, and conveys hydrogen generated by electrochemical reaction on the cathode side. The flow channel convex portion 10 is the support surface of the central area of ​​the stamped bipolar plate and is also the welding surface of the composite diffusion layer. The bipolar plate is provided with a pure water inlet 4 and a water oxygen outlet 5, which both span the entire flow channel region. Pure water is evenly distributed to one end of the conveying channel on one side surface of the bipolar plate through the pure water inlet 4. The water oxygen outlet 5 is located on the opposite side of the conveying channel. Unreacted pure water and generated oxygen are evenly discharged through the water oxygen outlet 5. The bipolar plate is provided with a first hydrogen outlet 6 and a second hydrogen outlet 7 across the conveying channel on the other side of the bipolar plate, and perpendicular to the flow direction of the channel. The generated hydrogen is conveyed to the flow channel recess 9 (conveying channel) through the composite diffusion layer, and then discharged evenly through the first hydrogen outlet 6 and the second hydrogen outlet 7, so as to reliably realize hydrogen production. The PEM electrolyzer bipolar plate assembly of the present invention has a simple structure, can greatly reduce the cost of the early processing and later surface treatment of the bipolar plate, not only provides convenience for the installation of the bipolar plate, but also reduces the contact resistance between the bipolar plate and the composite diffusion layer, and improves the hydrogen production performance of the PEM electrolyzer.

[0029] The membrane electrode is arranged on the outer surface of the first composite diffusion layer 13, and the membrane electrode is arranged on the outer surface of the second composite diffusion layer 5. In the above structure, the membrane electrode is used for the whole structure to realize the hydrogen production reaction.

[0030] The bipolar plate 1 is provided with positioning holes 2. In the above structure, a plurality of positioning holes 2 are provided at the four ends of the bipolar plate, and adjacent bipolar plates are positioned with each other through the positioning holes 2 to prevent horizontal movement and facilitate installation. The first composite diffusion layer 13 includes a porous mesh plate 11 and a titanium felt 12, and the porous mesh plate 11 on the inner surface of the first composite diffusion layer 13 is attached to the surface of one end of the flow channel region 3 of the bipolar plate 1; the second composite diffusion layer 15 includes a porous mesh plate 11 and a titanium felt 12, and the porous mesh plate 11 on the inner surface of the second composite diffusion layer 15 is attached to the surface of one end of the flow channel region 3 of the bipolar plate 1. The composite diffusion layer includes a porous mesh plate 11 and a titanium felt 12. The porous mesh plate 1 is press-welded to the concave flow channel surface 9 on the surface of the bipolar plate, so that the concave flow channel surface 9 is pressed toward the titanium felt 12 through the porous mesh plate 11, thereby preventing the titanium felt 12 from blocking the conveying channel due to deformation and reducing the contact area between the titanium felt 12 and the membrane electrode, thereby increasing the contact resistance between the stamped bipolar plate and the membrane electrode and avoiding affecting the performance of the PEM electrolyzer.

[0031] The bipolar plate 1 is provided with positioning pin holes 8. In the above structure, the four corners of the flow channel area of ​​the bipolar plate are respectively provided with positioning pin holes 8 for positioning pins to pass through and fix the membrane electrode to prevent the membrane electrode from horizontally moving during the assembly process and the hydrogen production process of the PEM hydrogen production equipment.

[0032] Adjacent bipolar plates 1 are positioned by bolts passing through positioning holes 2. The porous mesh plate 11 of the first composite diffusion layer 13 is press-welded to the bipolar plate 1; the porous mesh plate 11 of the second composite diffusion layer 13 is press-welded to the bipolar plate 1. The above structure, through press-welding connection, allows the concave surface 9 of the flow channel to be pressed against the titanium felt 12 through the porous mesh plate 11, preventing the titanium felt 12 from blocking the conveying channel due to deformation and reducing the contact area between the titanium felt 12 and the membrane electrode, thereby increasing the contact resistance between the bipolar plate (stamped bipolar plate) and the membrane electrode, and avoiding affecting the performance of the PEM electrolyzer.

[0033] The pure water inlet 4 and the water-oxygen outlet 5 on the bipolar plate 1 span the flow channel area 3, and the pure water enters the flow channel concave portion 9 on the surface of one side of the flow channel area 3 through the pure water inlet 4 to perform a hydrogen production reaction, and the unreacted pure water and the generated oxygen in the hydrogen production process are discharged from the flow channel concave portion 9 through the water-oxygen outlet 5. The above structure facilitates the distribution of the pure water for the hydrogen production reaction to the conveying channel for the hydrogen production reaction, and the unreacted pure water and the generated oxygen are uniformly discharged through the water-oxygen outlet 5.

[0034] The first hydrogen outlet 6 and the second hydrogen outlet 7 on the bipolar plate 1 cross the flow channel region 3, and the hydrogen generated by the hydrogen production reaction is discharged from the first hydrogen outlet 6 and the second hydrogen outlet 7 through the flow channel recess 9 on the other side of the flow channel region 3. The above structure facilitates the hydrogen generated by hydrogen production to be transported to the transport channel through the composite diffusion layer and then uniformly discharged through the hydrogen outlet.

[0035] The bipolar plate 1 and the composite diffusion layer 13 are connected together by a pressure welding process.

[0036] The bipolar plate 1 is a titanium thin plate with a thickness of 0.3 mm to 0.5 mm. The angle of the bending structure 14 of each flow segment of each flow channel concave portion relative to the direction of the flow channel concave portion is 5 to 10 degrees.

[0037] The bipolar plate assembly of the PEM electrolyzer described in the present invention is made by a stamping process, and then the bipolar plate and the composite diffusion layer are formed into one piece by a pressure welding process. The central area of ​​the bipolar plate is a stamped flow channel area 3, such as Figure 1 As shown, the flow channel area includes multiple parallel flow channel recesses 9. The flow channel area on one side of the bipolar plate is provided with multiple parallel flow channel recesses 9, and the flow channel area on the other side of the bipolar plate is provided with multiple parallel flow channel recesses 9, forming a double flow channel structure. Different flow channels are used to connect different ports and to flow different media. Each flow channel recess 9 adopts a multi-segment twill structure, that is, multiple bending structures 14 are provided on the inner wall of the flow channel recess 9, and the inclination angle of each flow segment of each flow channel recess 9 is set at 5 to 10 degrees. In this way, more contact area with the composite titanium felt and more uniform flow field distribution can be achieved. Multiple flow channel concave portions 9 and multiple flow channel convex portions 10 are arranged on each side surface of the flow channel region 3. The flow channel concave portion 9 on one side surface and the adjacent flow channel concave portion 9 on the other side surface are structures where the concave and convex surfaces are connected. The flow channel concave portion 9 is a conveying channel, which conveys pure water and oxygen generated by electrochemical reaction on the anode side of the flow channel concave portion 9, and conveys hydrogen generated by electrochemical reaction on the cathode side. The flow channel convex portion 10 is the support surface of the central area of ​​the stamped bipolar plate and is also the welding surface of the composite diffusion layer. The bipolar plate is provided with a pure water inlet 4 and a water oxygen outlet 5, which both span the entire flow channel region. Pure water is evenly distributed to one end of the conveying channel on one side surface of the bipolar plate through the pure water inlet 4. The water oxygen outlet 5 is located on the opposite side of the conveying channel. Unreacted pure water and generated oxygen are evenly discharged through the water oxygen outlet 5. The bipolar plate is provided with a first hydrogen outlet 6 and a second hydrogen outlet 7 across the delivery channel on the other side of the bipolar plate and perpendicular to the flow direction of the channel. The generated hydrogen is transported to the flow channel recess 9 through the composite diffusion layer, and then discharged evenly through the first hydrogen outlet 6 and the second hydrogen outlet 7, thereby reliably realizing hydrogen production.

[0038] The PEM electrolyzer bipolar plate assembly described in the present invention has flow channel openings across the entire flow channel area at the four ends of the flow channel area, including a pure water inlet, a pure water inlet 4 and a water oxygen outlet 5 along the flow channel direction, and a hydrogen outlet perpendicular to the flow channel direction. The flow channel area starts from one side to the other side with a flow channel convex portion 10 and ends with a flow channel concave portion 9. The flow channel area is square. In the flow channel of the stamped bipolar plate, each flow channel concave portion 9 adopts a multi-segment twill structure, and the inclination angle of each flow segment is 5 to 10 degrees. Each flow channel concave portion 9 on the surface of one side of the bipolar plate is a structure in which the concave and convex surfaces are connected to the flow channel concave portion 9 adjacent to the other side of the bipolar plate. The composite diffusion layer includes a porous mesh plate and a titanium felt, and one side of the porous mesh plate is connected to the flow channel concave surface of the stamped bipolar plate by welding. The structure of the present invention reduces the cost of the PEM electrolyzer body and improves the ability to subsequently form large-scale and standardized manufacturing of the bipolar plates of the PEM electrolyzer. At the same time, the pressure welding connection between the bipolar plate 1 and the composite diffusion layer not only facilitates installation and positioning, but also reduces contact resistance, thereby improving the performance of the PEM electrolysis of water to produce hydrogen.

[0039] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A PEM electrolyzer bipolar plate assembly, characterized in that: The bipolar plate (1) is a stamped structure, a flow channel region (3) is arranged in the middle of the bipolar plate (1), each side surface of the flow channel region (3) includes a plurality of concave flow channel recesses (9) and a plurality of convex flow channel protrusions (10), a plurality of bending structures (14) are arranged on the inner wall of the flow channel recess (9), a pure water inlet (4), a water oxygen outlet (5), a first hydrogen outlet (6) and a second hydrogen outlet (7) are arranged near the flow channel region (3) on the bipolar plate (1), The pure water inlet (4) is located at one end of the multi-channel concave portion (9) of the flow channel region (3), the water oxygen outlet (5) is located at the other end of the multi-channel concave portion (9) of the flow channel region (3), the first hydrogen outlet (6) is located at one side of the flow channel region (3), the second hydrogen outlet (7) is located at the other side of the flow channel region (3), a first composite diffusion layer (13) is arranged on the surface of one end of the flow channel region (3), and a second composite diffusion layer (15) is arranged on the surface of the other side of the flow channel region (3).

2. The PEM electrolyzer bipolar plate assembly according to claim 1, characterized in that: A membrane electrode is arranged on the outer surface of the first composite diffusion layer (13), and a membrane electrode is arranged on the outer surface of the second composite diffusion layer (15).

3. The PEM electrolyzer bipolar plate assembly according to claim 1 or 2, characterized in that: A positioning hole (2) is provided on the bipolar plate (1).

4. The PEM electrolyzer bipolar plate assembly according to claim 2, characterized in that: The first composite diffusion layer (13) comprises a porous mesh plate (11) and a titanium felt (12), and the porous mesh plate (11) on the inner surface of the first composite diffusion layer (13) is bonded to one end surface of the flow channel region (3) of the bipolar plate (1); the second composite diffusion layer (15) comprises a porous mesh plate (11) and a titanium felt (12), and the porous mesh plate (11) on the inner surface of the second composite diffusion layer (15) is bonded to one end surface of the flow channel region (3) of the bipolar plate (1).

5. The PEM electrolyzer bipolar plate assembly according to claim 1 or 2, characterized in that: A positioning pin hole (8) is provided on the bipolar plate (1).

6. The PEM electrolyzer bipolar plate assembly according to claim 3, characterized in that: Adjacent bipolar plates (1) are positioned by bolts passing through the positioning holes (2).

7. The PEM electrolyzer bipolar plate assembly according to claim 4, characterized in that: The porous mesh plate (11) of the first composite diffusion layer (13) is connected to the bipolar plate (1) by pressure welding; and the porous mesh plate (11) of the second composite diffusion layer (13) is connected to the bipolar plate (1) by pressure welding.

8. The PEM electrolyzer bipolar plate assembly according to claim 1 or 2, characterized in that: The pure water inlet (4) and the water-oxygen outlet (5) on the bipolar plate (1) span the flow channel region (3); pure water enters the flow channel recess (9) on one side of the flow channel region (3) through the pure water inlet (4) to perform a hydrogen production reaction; pure water that does not react during the hydrogen production process and the generated oxygen are discharged from the flow channel recess (9) through the water-oxygen outlet (5).

9. The PEM electrolyzer bipolar plate assembly according to claim 8, characterized in that: The first hydrogen outlet (6) and the second hydrogen outlet (7) on the bipolar plate (1) span the flow channel area (3), and the hydrogen generated by the hydrogen production reaction is discharged from the first hydrogen outlet (6) and the second hydrogen outlet (7) through the flow channel recess (9) on the other side surface of the flow channel area (3).

10. The PEM electrolyzer bipolar plate assembly according to claim 2, characterized in that: The bipolar plate (1) and the composite diffusion layer (13) are connected together by a pressure welding process.

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