Bipolar plate, application thereof and electrolytic bath adopting bipolar plate

Abstract

The invention provides a bipolar plate flow channel design, by optimizing the flow field structure of the cathode plate, CO2 raw material gas used for electrocatalytic reduction can be uniformly distributed on the cathode flow field plate, gas-liquid distribution and reaction zone uniformity in an electrolytic cell reactor are effectively improved, pressure loss is small, reaction dead zones are reduced, reaction current is uniformly distributed, and the reaction efficiency is improved. Meanwhile, the phenomenon of local heating concentration is reduced, so that the uniformity and stability of electrochemical reaction are improved, and the performance of the electrolytic bath is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy, energy conservation and environmental protection, and in particular to a bipolar plate structure suitable for a carbon dioxide reduction electrolytic cell and an electrolytic cell comprising the bipolar plate. Background Art

[0002] As global climate change intensifies, the continued rise in carbon dioxide (CO2) concentrations has become one of the main factors causing environmental disasters. How to effectively capture and convert CO2 has become an important research direction in academia and industry. Through the electrocatalytic reduction reaction of carbon dioxide in the electrolyzer (CO2 Reduction Reaction, hereinafter referred to as CO2RR), CO2 can be converted into high-value-added carbon-based fuels and chemicals such as formic acid, ethanol, carbon monoxide, etc., which can not only realize the resource utilization of CO2, but also provide energy storage solutions for new energy power generation systems (such as solar energy and wind energy). This technology provides an important practical path to achieve the goal.

[0003] In the CO2 reduction electrolyzer, the membrane electrode assembly (MEA) and bipolar plate are the core components of the electrolyzer, and their performance directly determines the CO2 reduction efficiency and product selectivity. As one of the important components of the electrolyzer, the bipolar plate not only undertakes the distribution and transportation of gas and liquid, provides mechanical support for the electrolyzer, but also undertakes the functions of conducting current, hydrothermal management and discharge of reaction products. However, for carbon dioxide electrolyzers, the currently widely used bipolar plates lack targeted flow channel design. Traditional flow channel structures mostly adopt the design of hydrogen energy or fuel cells. However, the electrocatalytic reactions of hydrogen energy and fuel cells are relatively simple and it is difficult to meet the complex reaction requirements in the CO2RR process. Especially in the large-scale CO2RR electrolyzer industrial application, due to the complexity of the reaction, the traditional flow channel structure that has not been specifically designed will cause the electrolyzer pressure difference to be too high and the uneven gas-liquid distribution will seriously reduce the performance and service life of the electrolyzer. In addition, the optimized design of the flow channel structure is also of vital importance to reduce the energy loss of the electrolyzer and improve the Faraday efficiency and reaction stability. Therefore, developing a bipolar plate flow field design specifically for the CO2RR system that takes into account gas-liquid distribution uniformity, fluid transport efficiency and thermal management performance has become a key direction for improving the performance of CO2RR electrolyzers. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a bipolar plate flow channel design for the electrocatalytic reduction of carbon dioxide. By optimizing the flow field structure of the cathode plate, the CO2 raw gas used for the electrocatalytic reduction can be evenly distributed on the cathode flow field plate, effectively improving the gas-liquid distribution and the uniformity of the reaction zone in the electrolyzer reactor, with less pressure loss, reducing the reaction dead zone, making the reaction current evenly distributed, and reducing the phenomenon of local heat concentration, thereby improving the uniformity and stability of the electrochemical reaction and improving the performance of the electrolyzer.

[0005] To achieve the purpose of the present invention, the present invention provides a bipolar plate, which is composed of an anode flow field plate and a cathode flow field plate, the cathode flow field plate is provided with a flow channel area, the flow channel area further includes a distribution area, a reaction area and a confluence area, the distribution area and the confluence area are both provided with parallel multi-level boss-shaped flow channels, and the number of bosses on different levels of flow channels is different.

[0006] In a preferred technical solution, the number of bosses in the primary flow channel of the distribution zone adjacent to the reaction zone is more than twice the number of bosses in the primary flow channel adjacent to the gas inlet of the cathode flow field plate.

[0007] In a preferred technical solution, the sides of the distribution area and the confluence area parallel to the flow direction of the reaction area are designed to be non-right angles.

[0008] According to a preferred technical solution, the height of the bosses on the distribution area and the confluence area ranges from 2 to 3 mm.

[0009] A preferred technical solution is that the bosses of the distribution area and the confluence area are designed to be oblique, and are inclined by 30°-60° to the flow channel direction of the cathode flow field plate reaction area.

[0010] According to a preferred technical solution, the anode flow field plate is provided with a flow channel area, and the flow channel area further includes a distribution area, a reaction area and a confluence area, and a plurality of elliptical flow channels are arranged in parallel in the distribution area and the confluence area.

[0011] A preferred technical solution is that the elliptical flow channel of the anode flow field plate is inclined at 45°-75° to the direction of the flow channel in the reaction zone of the anode flow field plate.

[0012] In a preferred technical solution, the straight flow channel of the reaction zone of the anode flow field plate extends to the inner side of the distribution zone and forms a transition fillet with a certain bending radius at the junction with the distribution zone.

[0013] The present invention also provides a carbon dioxide electrocatalytic reduction electrolyzer, which comprises at least two bipolar plates of the above technical solution.

[0014] In a preferred technical solution, the electrolytic cell further comprises an anode end plate, a cathode end plate, an anode insulating plate, a cathode insulating plate, an anode current collecting field plate, a cathode current collecting field plate, and a membrane electrode (an anode porous diffusion electrode, a cathode gas diffusion electrode, and an anion exchange membrane).

[0015] Beneficial effects of the present invention: The present invention provides a bipolar plate flow channel design for electrocatalytic reduction of carbon dioxide. By optimizing the flow field structure of the cathode plate, the CO2 raw gas used for electrocatalytic reduction can be evenly distributed on the cathode flow field plate, effectively improving the gas-liquid distribution and reaction zone uniformity in the electrolyzer reactor, with less pressure loss, reducing the reaction dead zone, making the reaction current evenly distributed, and reducing the phenomenon of local heat concentration, thereby improving the uniformity and stability of the electrochemical reaction and improving the performance of the electrolyzer. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic structural diagram of the cathode flow field plate of the bipolar plate of Example 1 of the present invention; Figure 2 This is a schematic structural diagram of the anode flow field plate of the bipolar plate of Example 1 of the present invention; Figure 3 for Figure 1 A magnified view of the cathode flow field plate distribution area; Figure 4 for Figure 2 A magnified view of the anode flow field plate distribution area; Figure 5 It is a schematic diagram of the structure of the flow channel cathode flow field plate without a boss structure; Figure 6 It is a schematic diagram of the structure of a flow channel cathode flow field plate with a boss structure; Figure 7 A cathode plate for the distribution area and the busbar area including a structure with the right angle area removed; Figure 8 The simulation results of gas flow distribution in the cathode plate flow channel without boss and with optimized boss height; Fig. 9 The simulation results of gas flow distribution in the cathode plate flow channel of the distribution area and confluence area with different designs; Fig.10 This is a schematic diagram of the overall structure of the fuel cell stack according to Example 6 of the present invention.

[0017] Description of reference numerals: 10 - cathode flow field plate; 11 - gas inlet of cathode flow field plate, 12 - distribution area of ​​cathode flow field plate, 13 - gas outlet of cathode flow field plate, 14 - reaction area of ​​cathode flow field plate, 15 - confluence area of ​​cathode flow field plate.

[0018] 20-anode flow field plate; 21-liquid inlet of anode flow field plate, 22-distribution area of ​​anode flow field plate, 23-liquid outlet of anode flow field plate, 24-reaction area of ​​anode flow field plate, 25-confluence area of ​​anode flow field plate. 3-inlet flow channel, 4-inlet distribution flow channel, 5-primary boss-shaped flow channel, 6-secondary boss-shaped flow channel, 7-third-level boss-shaped flow channel, 8-fourth-level boss-shaped flow channel, 9-sealing groove.

[0019] 30 - cathode flow field plate without boss structure; 31 - gas inlet of cathode flow field plate, 32 - distribution area of ​​cathode flow field plate, 33 - gas outlet of cathode flow field plate, 34 - reaction area of ​​cathode flow field plate, 35 - confluence area of ​​cathode flow field plate.

[0020] 40 - cathode full boss structure flow field plate; 41 - gas inlet of cathode flow field plate, 42 - distribution area of ​​cathode flow field plate, 43 - gas outlet of cathode flow field plate, 44 - reaction area of ​​cathode flow field plate, 45 - confluence area of ​​cathode flow field plate.

[0021] 50 - cathode flow field plate with right-angle area boss structure removed; 51 - gas inlet of cathode flow field plate, 52 - distribution area of ​​cathode flow field plate, 53 - gas outlet of cathode flow field plate, 54 - reaction area of ​​cathode flow field plate, 55 - confluence area of ​​cathode flow field plate.

[0022] 60-anode end plate, 61-cathode end plate, 62-anode insulating plate, 63-cathode insulating plate, 64-current collecting plate, 65-bipolar plate, 66-cathode gas diffusion electrode, 67-ion exchange membrane, 68-anode porous diffusion electrode. DETAILED DESCRIPTION

[0023] The key to bipolar plate design lies in the flow channel design. Minimizing flow resistance and pressure loss as much as possible while ensuring that the reaction gas and liquid are evenly distributed in each flow channel is a key indicator to measure the excellence of the flow channel design. Uniform distribution of bipolar plate flow channels and minimization of flow resistance are important guidelines to ensure the adaptability and reliability of the stack and system. In the current conventional bipolar plate design, the reaction gas and liquid are unevenly distributed, mainly in the direction perpendicular to the flow channel. Although some improved bipolar plates are equipped with distribution areas, the flow channel density, height, and geometric configuration in the distribution area are unreasonable, resulting in uneven distribution of the fluid in the distribution area.

[0024] Based on this, the present invention provides a new bipolar plate structure, the shape of the bipolar plate is preferably rectangular, square or circular, and more preferably rectangular. The bipolar plate is composed of an anode flow field plate and a cathode flow field plate, and the cathode flow field plate and the anode flow field plate are sealed by a sealing ring. The cathode flow field plate is evenly provided with no less than 2 gas ports, preferably 2, respectively, gas inlet and gas outlet, and the gas ports are centrally symmetrically arranged at the diagonal of the flow field plate along the direction of the edge of the cathode flow field plate perpendicular to the flow channel. The anode flow field plate is evenly provided with no less than 2 liquid ports, respectively, liquid inlet and liquid outlet, preferably more than 6 liquid ports. Compared with gas, the number of liquid ports is more because the liquid viscosity is large, resulting in excessive liquid flow resistance; and a single port area is too large, which will cause the plate inlet edge structure to be unstable under stress, so by increasing the number of ports, the support for the edge of the plate is strengthened and the liquid flow resistance is reduced. The liquid ports are centrally symmetrically arranged at the diagonal of the flow field plate along the direction of the edge of the anode flow field plate perpendicular to the flow channel.

[0025] The fluid field structures (i.e., flow channel areas) of the anode flow field plate and the cathode flow field plate each include a distribution area, a reaction area, and a confluence area. Gas and liquid enter from the inlet in sequence, flow through the distribution area, the reaction area, and the confluence area, and are discharged through the outlet.

[0026] On the path from the gas fluid port to the reaction zone on the cathode flow field plate, boss-shaped flow channels are arranged in the distribution area and the confluence area. Each boss is inclined at a certain angle to the flow channel direction of the reaction zone of the cathode flow field plate, preferably 30°-60°, and further preferably 45°. The number of bosses is arranged and increased layer by layer, and the number of bosses close to the reaction zone is at least twice the number of bosses close to the fluid port.

[0027] The distribution part on the anode flow field plate is composed of a plurality of parallel elliptical flow channels, which are inclined at a certain angle to the flow direction of the reaction zone of the anode flow field plate, preferably 45°-75°, and further preferably 60°. Each liquid fluid outlet is allocated at least 8 elliptical flow channels.

[0028] In order to guide and optimize the fluid distribution so that the fluid enters the reaction zone evenly, the cathode flow field plate is designed with a multi-stage diversion boss-shaped flow channel. The gas enters the distribution area through the inlet flow channel. With the assistance and guidance of the inlet distribution flow channel, the gas is first evenly distributed to the first-stage boss-shaped flow channel containing at least 15 bosses for preliminary diversion; after the first-stage diversion, the fluid enters the second-stage flow channel with an increased number of bosses, and the number of bosses in the second-stage flow channel increases by at least 8 compared with the first stage. After diversion again, when the gas enters the third-stage flow channel, the number of bosses increases by at least 8 compared with the second stage, and the total number of diversion stages is no more than five. The number of bosses in the diversion flow channel increases step by step to ensure uniform distribution of the gas and effective mass transfer. If the number of diversion stages is more than 5, the flow velocity at the end of the gas classification decreases, the flow resistance increases, and the fluid pressure drop increases. In addition, the flow velocity at the end is reduced, and local vortices may form in the boss flow channel, further increasing the gas pressure drop. If the number of bosses is too small, on the one hand, the contact area between this part and the membrane electrode will be reduced, making the support unstable, and on the other hand, the gas flow speed will be too slow, which is not conducive to gas distribution.

[0029] The reaction zone is a straight-line flow channel; the reaction zone flow channels are distributed at intervals; the cathode reaction zone and the distribution zone are preferably connected by a circular arc transition structure. Unlike the cathode reaction zone, the anode reaction zone and the distribution zone are connected by a composite curve transition region. Specifically, the straight-line flow channel of the anode reaction zone extends to the inner side of the distribution zone, and forms a transition fillet with a certain bending radius at the junction with the distribution zone to guide the liquid into the reaction zone. The reaction zone flow channel adopts serpentine flow channels, cross-type flow channels, wavy flow channels and parallel flow channels. Considering the working conditions of CO2RR, parallel flow channels are preferably used.

[0030] The cathode flow field plate distribution part of the bipolar plate is provided with a boss structure of the same height. The shape of the boss is preferably cylindrical, elliptical or circular. The area ratio of the boss and the groove is preferably 2:1 to 1:2, and more preferably 1:1. The height range of the boss is simulated and calculated, and the height range of the boss is 2-3 mm, and more preferably 2-2.5 mm. By optimizing the design of different boss heights, the flow guidance of the fluid in the distribution part is achieved, the local resistance and pressure loss of the fluid flow are reduced, and the uniformity of the flow distribution when the fluid enters the active part is optimized. According to simulation verification, the 2 mm height boss design can significantly improve the flow distribution of each flow channel in the active part, making it more uniform, thereby improving the reaction efficiency and electrochemical performance.

[0031] The present invention redesigns the flow channel of the traditional cathode flow field plate, and in particular optimizes the flow channel design in the distribution area as follows: the cathode flow field plate preferably adopts a full boss structure design of the inlet distribution area and the outlet confluence area, and the uniformity of fluid distribution is enhanced by evenly arranging the bosses; the inlet distribution area and the outlet confluence area remove the right-angle area along the edge parallel to the direction of the cathode flow field plate flow channel, and removing the right-angle area reduces the flow resistance of the fluid at the turn of the flow channel; the inlet distribution area and the outlet confluence area are distributed obliquely, optimizing the guidance of the fluid and the pressure gradient distribution. According to simulation verification, the bipolar plate structure with oblique distribution flow design has a more uniform flow distribution in each flow channel in the reaction area, and the pressure difference diagram shows a significantly reduced pressure loss in the distribution area, thereby improving the overall performance and reaction efficiency of the bipolar plate.

[0032] It can be seen from the above technical solution that by adjusting the flow channel arrangement in the distribution area and / or confluence area, the number of flow channels close to the fluid port is reduced, so that the flow channels are designed in a more compact area, ensuring that the fluid can efficiently enter the flow channel from the fluid port; and as the fluid flows to the reaction area, the number of flow channels gradually increases, which promotes a more uniform distribution of the reaction gas / liquid in the reaction area and improves the reaction efficiency. Furthermore, more flow channel arrangements increase the contact area between the fluid and the surface of the bipolar plate, thereby improving the heat conduction and heat dissipation performance, making the system operation more stable and efficient.

[0033] In addition, the substrate of the bipolar plate is a conductor. The CO2RR reaction process often involves strong alkalinity, strong acidity, and high-potential electrochemical oxidation environments. Therefore, the bipolar plate substrate is generally made of corrosion-resistant titanium metal. In low-voltage alkaline environments, nickel-based substrates can also be used, and graphite-based substrates or stainless steel substrates with special coatings or anti-etching treatments can also be used as bipolar plates.

[0034] Based on this inventive concept, the present invention provides a corresponding electric stack suitable for carbon dioxide electroreduction, including at least one bipolar plate with the above-mentioned characteristics, the carbon dioxide electrolysis electric stack includes an anode end plate, a cathode end plate, an anode insulating plate, a cathode insulating plate, an anode current collecting field plate, a cathode current collecting field plate, a bipolar plate, an anode porous diffusion electrode, a cathode gas diffusion electrode and an anion exchange membrane, an anion exchange membrane is arranged between the anode porous diffusion electrode and the cathode gas diffusion electrode, and the three constitute a membrane electrode, a bipolar plate is arranged on each side of the membrane electrode, the cathode side of the membrane electrode is in contact with the cathode flow field plate of the bipolar plate, and the anode side of the membrane electrode is in contact with the anode flow plate of the bipolar plate, and no less than 2 bipolar plates are used in a electric stack, and the arrangement order is anode end plate, anode insulating plate, anode current collecting field plate, bipolar plate, membrane electrode, bipolar plate, cathode current collecting field plate, cathode insulating plate, and cathode end plate.

[0035] Based on this, in order to enable those skilled in the art to understand the content of the present application more intuitively, the present invention will hereinafter describe in detail the technical solution of the present application through specific embodiments in conjunction with the accompanying drawings.

[0036] To this end, the embodiments of the present invention provide a bipolar plate and a fuel cell stack suitable for CO2RR, which solve the problems of uneven fluid distribution and large pressure loss in the bipolar plates of the prior art, improve the uniformity of the electrochemical reaction, and improve the performance of the fuel cell stack. Example 1

[0037] The present invention provides a bipolar plate structure used in CO2RR, including an anode flow field plate and a cathode flow field plate. The anode and cathode flow field plates are tightly attached and sealed to form a "two plates and two fields" structure: one side of the anode flow field plate is a liquid field for electrolyte circulation; one side of the cathode flow field plate is a gas field for gas circulation. Since the bipolar plate needs to output current / voltage, its substrate is a conductor. Common bipolar plate materials include graphite, nickel, titanium, stainless steel, etc. Considering the strong acid and strong alkali environment in the CO2RR process, in this example, the substrate of the bipolar plate is a titanium plate, and the thickness of the substrate is preferably 1-1.5 mm.

[0038] refer to Figure 1 and Figure 2 The cathode flow field plate 10 is provided with two gas fluid ports, which are centrally symmetrically distributed at the two corners of the cathode flow field plate 10. The anode flow field plate 20 is provided with eight liquid fluid ports, and all the fluid ports are centrally symmetrically distributed at both ends of the anode flow field plate 20 in the direction perpendicular to the flow channel. The fluid fields of the cathode flow field plate 10 and the anode flow field plate 20 include a distribution area, a reaction area and a confluence area. These three areas are arranged in sequence along the flow field direction of the reaction area of ​​the bipolar plate, that is, the reaction gas CO2 and the electrolyte flow into their respective flow field plates from the gas fluid port at one end of the cathode flow field plate and the liquid fluid port at one end of the anode flow field plate respectively, and are expanded and distributed through their respective distribution areas and evenly distributed to the reaction area. The distribution area of ​​the reaction area is large, and the CO2 gas and the electrolyte contact in the reaction area to produce an electrochemical reaction. The reacted gas and liquid (including unreacted gas, liquid and reaction products) converge through the confluence areas of the cathode flow field plate and the anode flow field plate respectively, and the gas flows out of the bipolar plate through the gas fluid port at the other end of the cathode flow field plate and the liquid flows out of the bipolar plate through the liquid fluid port at the other end of the anode flow field plate.

[0039] In the above-mentioned fluid flow process, the pressure loss is mainly concentrated in the distribution area and the confluence area. This is because the fluid ports are usually only set at local positions of the cathode flow field plate 10 and the anode flow field plate 20, and the reaction area needs to cover the middle area of ​​the cathode flow field plate 10 and the anode flow field plate 20 as much as possible. This causes the fluid to diffuse from the smaller fluid ports to the larger reaction zone, and from the larger reaction zone to the smaller fluid ports. This process is prone to cause pressure loss. Since the confluence area is located on the outlet side, its pressure loss change has little effect on the battery stack, while the distribution area, as the inlet side, is limited by the limited port area, resulting in an increase in the flow channel density and a smaller flow channel period, which significantly increases the local pressure loss in the distribution area and has a greater impact on the performance of the battery stack.

[0040] In order to reduce the pressure loss in the distribution area, in the bipolar plate of the present invention, the distribution area and the confluence area adopt a boss-shaped flow channel, and the shape of the boss is preferably cylindrical, elliptical or circular. The area ratio of the boss and the groove is preferably 2:1 to 1:2, and more preferably 1:1. The height of the boss is preferably 2-3 mm, and more preferably 2-2.5 mm. By introducing a boss in the fluid path, a dispersed local disturbance is formed, thereby breaking the laminar boundary effect in the linear flow channel, and this conclusion is verified by simulation experiments. When the fluid passes through the boss-shaped flow channel, it will flow with lower resistance, rather than generating significant velocity gradients and shear stresses along the narrow channel of the linear flow channel. This distributed design reduces the pressure difference in the fluid channel and helps to reduce the pressure loss of the overall system.

[0041] In the cathode flow field plate, from the gas fluid port to the reaction zone, the number of bosses in the flow channel in the distribution zone increases step by step from the gas fluid port to the reaction zone, and the closer to the reaction zone, the more the flow channel. For example, along the direction of the flow channel in the reaction zone of the bipolar plate, the number of bosses in the flow channel increases at a rate of 8-10 per level, from 15 near the fluid port to 50 near the reaction zone. The above-mentioned design of changing the number of bosses is also applied to the confluence area. By adjusting the number distribution of bosses, the number of bosses in the area close to the fluid port is relatively small, so that the flow channel can be concentrated in a smaller space and directly connected to the fluid port for gas circulation; while the number of bosses in the flow channel in the area close to the reaction zone is increased to ensure that the reaction gas is evenly distributed in the reaction zone, so as to fully react.

[0042] Specifically, Figure 1 As shown, the cathode flow field plate 10 is provided with two gas fluid ports, and the anode flow field plate is provided with eight liquid fluid ports. The fluid ports on the cathode flow field plate are respectively a gas inlet 11 and a gas outlet 13. The gas inlet 11 and the gas outlet 13 are diagonally and symmetrically distributed on both sides of the cathode flow field plate. The gas inlet 11 is located on one side of the flow channel area, and the gas outlet 13 is located on the other side of the flow channel area. Figure 2As shown, the fluid openings on the anode flow field plate 20 are respectively a liquid inlet 21 and a liquid outlet 23, which are distributed on both sides of the flow channel area of ​​the anode flow field plate. The liquid inlet 21 and the liquid outlet 23 are diagonally symmetrically distributed on both sides of the anode flow field plate. The liquid inlet 21 is located on one side of the flow channel area, and the liquid outlet 23 is located on the other side of the flow channel area. The liquid inlet 21 and the liquid outlet 23 are also centrally symmetrically distributed. The gas inlet 11, the gas outlet 13, the liquid inlet 21, and the liquid outlet 23 are symmetrically designed, and the above openings are centrally symmetrically distributed, which is convenient for improving the utilization rate of the plate area.

[0043] The cathode flow field plate 10 and the anode flow field plate 20 both include flow channel areas, specifically including a distribution area, a reaction area and a confluence area, and the distribution area, the reaction area and the confluence area are sequentially distributed along the parallel direction of the flow channel in the flow field plate. Specifically, the cathode flow field plate 10 has a gas distribution area 12, a gas reaction area 14 and a gas confluence area 15, and the anode flow field plate 20 has a liquid distribution area 22, a liquid reaction area 24 and a liquid confluence area 25. The gas distribution area 12 of the cathode flow field plate 10 is used to evenly distribute the reaction gas from the gas inlet 11 to the gas reaction area, the gas confluence area 15 is used to converge the unreacted CO2 and the product gas after the reaction and output them to the gas outlet 13, the liquid distribution area 22 is used to evenly distribute the electrolyte to the liquid reaction area 24, and the liquid confluence area 25 is used to converge the product liquid of the electrocatalytic reaction to the liquid outlet 23 for discharge; the distribution area of ​​the gas reaction area 14 and the liquid reaction area 24 is the largest, generally exceeding half of the area of ​​the single-sided cathode flow field plate 10 and the anode flow field plate 20, and the electrochemical reduction reaction mainly occurs in the gas reaction area 14 and the liquid reaction area 24.

[0044] In order to separate the gas flow field and the liquid flow field, the bipolar plates are made by welding process to ensure the sealing between the bipolar plates. The bipolar plates and the membrane electrode are sealed by sealing rings. The fluid field side surfaces of the cathode flow field plate 10 and the anode flow field plate 20 are provided with sealing grooves 9 for installing sealing rings. The width of the sealing grooves 9 is preferably 2-4 mm. Through the welding wire and the sealing ring, the CO2 input from the gas inlet 11 and the electrolyte input from the liquid inlet 21 flow to the corresponding gas flow channel area and liquid flow channel area respectively, and the two flow fields are well sealed and will not be connected.

[0045] For details, see the partial enlargement of the structure of the flow channel area. Figure 3 and Figure 4 , taking the distribution area side of the flow channel area as an example. The gas distribution area 12 on the cathode flow field plate 10 is provided with a plurality of parallel bosses, each of which is inclined at a 45° angle to the long side direction of the cathode flow field plate 10 (i.e., the flow channel direction of the reaction area). The number of bosses increases gradually, and the number distributed near the reaction area is at least twice the number distributed near the gas inlet position, and uniform gas distribution is achieved through three changes. Figure 3As shown, the gas enters the distribution area through the inlet flow channel 3. With the assistance and guidance of the inlet distribution flow channel 4, the fluid is first evenly distributed to the first-level convex channel 15 containing 15 convex platforms for preliminary diversion. After the first-level diversion, the gas enters the second-level flow channel 6 with an increased number, and the number of the second-level flow channel 6 increases by at least 8 convex platforms compared with the first level. After diversion again, when the gas enters the third-level flow channel 7, the number of convex platforms increases by at least 8 more than the second level, and the increase of 8 convex platforms is one level. After flowing through the third-level flow channel 7, the gas enters the fourth-level flow channel 8. The number of convex flow channels in the fourth-level flow channel 8 is more than twice that of the inlet flow channel 5.

[0046] like Figure 4 As shown, the liquid distribution area 22 of the anode flow field plate 20 is configured as a plurality of parallel elliptical flow channels, which are inclined at a 60° angle to the long side direction of the bipolar plate (i.e., the reaction zone flow channel direction), and each liquid fluid passage is allocated at least 8 elliptical flow channels.

[0047] The gas fluid and the liquid fluid have been evenly distributed through the gas distribution area 12 and the liquid distribution area 22 of the cathode flow field plate before entering the reaction area, thereby ensuring that the flow rate and pressure of the fluid in the gas reaction area 14 and the liquid reaction area 24 are equal, and the reaction efficiency is improved. The reaction area can use serpentine flow channels, cross-type flow channels, wavy flow channels and parallel flow channels. Considering the working conditions of CO2RR, it is preferred to use parallel flow channels, that is, the gas reaction area 14 and the liquid reaction area 24 are straight flow channels, and the active part 12 is evenly and spacedly distributed along the short side direction of the bipolar plate.

[0048] In order to further reduce the flow resistance, in this embodiment, the liquid distribution area 22 and the liquid reaction area 24 of the anode flow field plate 20 are transitioned by an arc. Specifically, the straight flow channel of the liquid reaction area 24 extends to the inner side of the liquid distribution area 22, and forms a transition fillet with a certain bending radius at the junction with the liquid distribution area 22. The radius of the transition fillet is determined according to the size of the space where the flow channel is located, and this application does not impose any restrictions.

[0049] The design of the catchment area is the same as that of the distribution area and will not be described in detail here. Comparative Example 1

[0050] The cathode flow field plate design of the flow distribution area and the confluence area adopts a boss-free structure, see Figure 5 The gas inlet 31 and the gas outlet 33 have the same area and form a central symmetrical structure on the cathode flow field plate, located at two corners of the cathode flow field plate. The flow channel in the reaction zone of the fluid field is designed to be parallel to the Figure 1 The reaction zone area is consistent with that in Example 1. Figure 1The reaction zones have the same area, the difference is that the gas distribution zone 32 and the gas confluence zone 35 are large grooves with a depth of 2.5 mm without any protruding structure, the lowest part of the groove is consistent with the groove depth of the gas reaction zone flow channel structure 34, and there is no transition drainage structure design. Example 2

[0051] The cathode flow field plate design of the flow channel distribution area and the confluence area adopts a full-platform structure to enhance the disturbance and drainage of the raw gas, so as to achieve the purpose of uniform distribution of the raw gas in the flow channel. Figure 6 , the gas inlet 41 and the gas outlet 43, both of which have the same area, form a centrally symmetrical structure on the cathode flow field plate, and are located at the two corners of the cathode flow field plate. The reaction zone flow channel in the fluid field is designed as a parallel structure. Unlike the large groove without a protrusion structure in Comparative Example 1, the gas distribution area 42 and the gas confluence area 45 of the cathode flow field plate in Example 2 are parallel to the flow channel. 25-40 circular protrusions are gradually added in the direction parallel to the flow channel. The height of the circular protrusions is 2.5 mm, and a total of 4 columns are added. The width of the distribution area and the confluence area is consistent with the overall width of the flow channel reaction zone, and the lowest part is parallel to the lowest part of the groove of the reaction zone flow channel structure 44. The distribution area and the confluence area are designed at right angles near the edges of the long sides of the cathode flow field plate. The area of ​​the reaction zone is similar to that in Example 1. Figure 1 The reaction zone area is the same, and the difference from Example 1 is that the bosses in the distribution area 42 and the confluence area 25 are evenly distributed along the direction perpendicular to the reaction zone flow channel, while in Example 1, the cathode flow field plate distribution area and the confluence area have fewer bosses near the fluid outlet and more bosses near the reaction zone.

[0052] In order to clarify the influence of the boss structure in the distribution area and the confluence area on the disturbance of the raw gas on the gas distribution in the flow channel, a simulation analysis was carried out on the cathode flow fields of the two structures of Example 2 and Comparative Example 1. The inlet flow rate was set to 0.03 g / s, the outlet pressure was set to atmospheric pressure, and the flow distribution data of the raw gas in the flow channel was recorded.

[0053] The analysis results are as follows Figure 8 It shows that the flow distribution of the raw gas in the flow channel is different in both the cathode flow field plate with a boss structure and the flow field plate without a boss structure, and the overall trend is consistent. If the flow channel close to the gas inlet is numbered as the first flow channel, and the numbering is sequentially, the flow channel close to the reaction gas outlet is numbered as the 220th flow channel, such as Figure 5As shown. The flow distribution in the 1st and 220th flow channels is the largest, and the distribution in the 110th flow channel is the smallest; in the 1st to 110th flow channels, the flow distribution gradually decreases, and in the 110th to 220th flow channels, the flow distribution gradually increases. However, there are differences in the deviation values ​​of the flow in the two flow field structures. The maximum deviation value of the flow in the flow channel with no boss structure is 0.0039 L / min, and the maximum deviation value of the flow in the flow field plate with full boss structure is 0.0029 L / min. The raw gas in the cathode flow field plate with no boss structure has flow concentration and uneven flow distribution in the 1st and 220th flow channels. Compared with the flow channel distribution area of ​​the full boss structure, the gas flow distribution is more uniform and the flow deviation is reduced. Example 3

[0054] About the influence of boss height in distribution area or confluence area on flow distribution of raw gas.

[0055] In order to further optimize the boss structure of the distribution area and the confluence area and strengthen the disturbance of the raw gas, in this embodiment, the distribution area and the confluence area of ​​the full boss structure in Example 2 are optimized, and the height of the circular protrusions of the distribution area 43 and the confluence area 45 is preferably 2 mm. The width of the distribution area and the confluence area is consistent with the overall width of the flow channel reaction area, the lowest part is parallel to the groove height of the reaction zone flow channel structure 44, and the edge is designed at a right angle. The area of ​​the reaction zone is the same as that in Example 1. Figure 1 The reaction zones have the same area.

[0056] In order to clarify the influence of the boss height in the distribution area and the confluence area on the disturbance of the raw gas on the gas distribution in the flow channel, a simulation analysis was carried out on the cathode flow field of the full boss structure with two boss heights in Example 3. The inlet flow rate was set to 0.03 g / s, the outlet pressure was set to atmospheric pressure, and the flow distribution data of the raw gas in the flow channel was recorded.

[0057] The analysis results are as follows Figure 8 It is shown that among the 220 flow channels, the change trend of the flow distribution is consistent with the result of Example 2, but the flow distribution deviation value of each flow channel is reduced by optimizing the boss height. Compared with Example 2, the maximum deviation value is further reduced to 0.0027 L / min. Example 4

[0058] Regarding the influence of removing the right-angle area structure and the oblique structure distribution area or confluence area on the raw gas flow distribution.

[0059] In order to further enhance the disturbance of the gas by the cathode plate distribution area and the confluence area structure and make the flow distribution in the flow channel more uniform, based on the optimization of Example 3, as follows Figure 7 As shown, in this embodiment, a cathode plate of a distribution area and a confluence area including a structure with a right-angle area removed is constructed. Figure 6 The difference between the cathode flow field plates of the embodiment 2 and the embodiment 3 shown is that the right angles of the distribution area and the confluence area parallel to the flow channel direction along the cathode plate p are removed, the area of ​​the distribution area and the confluence area at both ends is reduced, and the number of elliptical bosses is reduced by 5-10, so as to achieve the purpose of reducing the flow distribution of the flow channel near the inlet and outlet ends and strengthening the flow distribution in the flow channel in the middle area. The height of the elliptical boss is the height optimized in embodiment 3, the width of the distribution area and the confluence area is consistent with the overall width of the flow channel reaction zone, the lowest part is parallel to the groove bottom part of the reaction zone flow channel structure 54, and the reaction zone area is the same as that in embodiment 1. Figure 1 The reaction zones have the same area. Example 5

[0060] The cathode plate structure design of Example 1 is adopted, such as Figure 1 , which is different from Example 4 in that, on the basis of removing the right angles of the distribution area and the confluence area, the boss structure connecting the outer edge of the gas inlet (gas outlet) of the distribution area (confluence area) to the 220th flow channel (the first flow channel) is further removed, the area of ​​the distribution area and the confluence area is reduced, and the oblique structure distribution area and confluence area are formed, and the number of elliptical bosses is reduced by 10-20, so as to achieve the purpose of reducing the flow distribution of the flow channels near the inlet and outlet ends and strengthening the flow distribution in the flow channels in the middle area. The height of the elliptical boss is the height optimized in Example 3, the width of the distribution area and the confluence area is consistent with the overall width of the flow channel reaction area, and the lowest part is parallel to the lowest part of the groove of the reaction zone flow channel structure 14. In order to clarify the influence of the structure and area in the distribution area and confluence area on the disturbance of the raw gas on the gas distribution in the flow channel, simulation analysis was carried out on the distribution area and confluence area of ​​the boss structure without the right-angle area and the distribution area and confluence area of ​​the oblique boss structure in Example 4 and Example 5. The inlet flow rate was set to 0.03 g / s, the outlet pressure was set to atmospheric pressure, and the flow distribution data of the raw gas in the flow channel was recorded.

[0061] The analysis results are as follows Fig. 9It is shown that among the 220 flow channels, the change trend of the flow distribution of the cathode plate in the distribution area and the confluence area of ​​the boss structure in Example 4, which includes removing the right-angle area, is consistent with the result of Example 2, but the flow distribution deviation value of each flow channel is reduced by optimizing the boss height. Compared with Example 3, the maximum deviation value is further reduced to 0.0026 L / min. The uniformity of the flow distribution of each flow channel in the cathode plate with the distribution area and the confluence area of ​​the oblique boss structure in Example 5 is greatly improved, and the maximum deviation value is reduced to 0.0008 L / min. The theoretical average flow rate of the entire flow channel is 0.0043 L / min. By calculating the deviation amplitude of the simulated flow rate and the theoretical average flow rate in each flow channel, it can be seen that by changing the structure and area of ​​the distribution area and the confluence area, the deviation amplitude is reduced from more than 35% to less than 10%. This proves that the distribution area and confluence area with the oblique boss structure in Example 1 can enhance fluid disturbance and uniformly distribute the flow in the reaction zone flow channel. Example 6

[0062] like Fig.10 As shown, this embodiment proposes a stack for carbon dioxide reduction reaction, the stack is composed of a plurality of repeating units, each repeating unit includes a bipolar plate and a membrane electrode. In these repeating units, at least one bipolar plate adopts the bipolar plate in the above-mentioned embodiment 1, and its specific structure is not repeated here. The carbon dioxide electrolysis stack is as follows Fig.10 As shown, it includes an anode end plate 60, a cathode end plate 61, an anode insulating plate 62, a cathode insulating plate 63, a current collecting plate 64, a bipolar plate 65, and a membrane electrode (cathode gas diffusion electrode 66, ion exchange membrane 67, anode porous diffusion electrode 68).

[0063] The anode end plate and the cathode end plate serve to fasten the battery stack structure and distribute the gas and liquid inlet and outlet. The cathode insulating plate and the anode insulating plate serve to insulate the battery stack from the outside world to ensure safe operation. The current collecting plate serves to collect current. The bipolar plate serves to distribute gas and liquid and conduct heat and electricity. The membrane electrode is the main area where electrical reaction catalysis occurs.

[0064] Due to the provision of the bipolar plate of the above-mentioned embodiment 1, the fuel cell stack has the advantages of uniform fluid distribution and small pressure loss, thereby improving the uniformity of the electrochemical reaction and ensuring that the fuel cell stack is stable, reliable and suitable for the carbon dioxide reduction system.

[0065] All of the above are primary implementations of this intellectual property and do not set limitations on other forms of implementation of this new product and / or new method. Those skilled in the art will use this important information and modify the above content to achieve similar implementations. However, all modifications or transformations based on the new product of this invention belong to the reserved rights.

[0066] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A bipolar plate, characterized in that: It is composed of an anode flow field plate and a cathode flow field plate. The cathode flow field plate is provided with a flow channel area. The flow channel area further includes a distribution area, a reaction area and a confluence area. The distribution area and the confluence area are both provided with parallel multi-stage boss-shaped flow channels, and the number of bosses on different levels of flow channels is different.

2. The bipolar plate according to claim 1, characterized in that: The number of bosses in the primary flow channel of the distribution zone adjacent to the reaction zone is more than twice the number of bosses in the primary flow channel adjacent to the gas inlet of the cathode flow field plate.

3. The bipolar plate according to claim 1 or 2, characterized in that: The sides of the distribution area and the confluence area parallel to the flow channel direction of the reaction area are designed to be non-right angles.

4. The bipolar plate according to claim 1 or 2, characterized in that: The height of the bosses on the distribution area and the confluence area ranges from 2 to 3 mm.

5. The bipolar plate according to claim 1 or 2, characterized in that: The bosses of the distribution area and the confluence area are designed to be oblique, and are inclined by 30°-60° to the flow channel direction of the cathode flow field plate reaction area.

6. The bipolar plate according to claim 1 or 2, characterized in that: The anode flow field plate is provided with a flow channel area, and the flow channel area further includes a distribution area, a reaction area and a confluence area. A plurality of elliptical flow channels are arranged in parallel in the distribution area and the confluence area.

7. The bipolar plate according to claim 1 or 2, characterized in that: The elliptical flow channel of the anode flow field plate is inclined at 45°-75° to the flow channel direction of the reaction zone of the anode flow field plate.

8. The bipolar plate according to claim 1 or 2, characterized in that: The straight flow channel of the reaction zone of the anode flow field plate extends to the inner side of the distribution zone, and forms a transition fillet with a certain bending radius at the junction with the distribution zone.

9. Use of the bipolar plate according to any one of claims 1 to 8 in a fuel cell, a hydrogen electrolyzer or a carbon dioxide electrocatalytic reduction electrolyzer.

10. An electrolytic cell, characterized in that: Comprising at least two bipolar plates according to any one of claims 1 to 8.

Images