Membrane electrode assembly and fuel cell

Abstract

The invention relates to a membrane electrode assembly and a fuel cell, the membrane electrode assembly comprises a catalyst layer (10), a gas diffusion layer (20) and a bipolar plate (30), the gas diffusion layer (20) comprises a porous layer (21) and a carbon paper layer (22), the bipolar plate (30) is provided with ridge parts (31) distributed at intervals, the top surfaces of the ridge parts (31) are in contact with the carbon paper layer (22), the carbon paper layer (22) is provided with carbon paper hydrophilic areas (221) distributed at intervals, and the carbon paper hydrophilic areas (221) are in contact with the porous layer (21). The porous layer (21) is provided with porous hydrophilic areas (211) which are distributed at intervals, the porous hydrophilic areas (211) correspond to the carbon paper hydrophilic areas (221), a part of each carbon paper hydrophilic area (221) is overlapped with a local area of the corresponding ridge part (31), and another part of each carbon paper hydrophilic area (221) is located in a runner area (32). The membrane electrode assembly can improve the electric pile performance under high current density, improve the electric pile power generation efficiency, and improve the whole system efficiency from the system level.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and particularly to a membrane electrode assembly of a fuel cell. The present invention also relates to a fuel cell provided with the membrane electrode assembly. Background Art

[0002] A proton exchange membrane fuel cell is a clean and efficient power generation device and is considered to be widely applicable to fields such as transportation and energy.

[0003] A bipolar plate is a key component for uniformly dispersing the reaction gases hydrogen and oxygen entering the fuel cell stack onto the surface of the membrane electrode and for discharging the reaction product liquid water. Therefore, there is a contradiction that gas supply and liquid water removal simultaneously occupy the reaction space of the membrane electrode.

[0004] To solve this problem, design changes are often required in the bipolar plate, gas diffusion layer, and operating conditions. Among them, in the methods of solving this problem by focusing on the gas diffusion layer, there are mainly two types: the design of the hydrophilic-hydrophobic gradient of the diffusion layer, and the design of the special-shaped structure or the partitioned hydrophilic-hydrophobic design of the diffusion layer.

[0005] For example, by combining different materials, hydrophobic agents, and preparation parameters, a microporous layer with a hydrophobic gradient structure in the vertical direction can be designed to form the characteristic of rapid outward discharge of liquid water. Although this technical solution solves the problem of the vertical discharge of liquid water in the microporous layer, it still cannot solve the influence of the water film formed on the outer surface of the microporous layer on the reverse diffusion of gas.

[0006] A gas diffusion layer structure with a similar flow channel structure can also be designed. By cooperating with the flow channels of the bipolar plate, the gas can fully contact the diffusion layer, increasing the drainage area on the surface of the gas diffusion layer and effectively reducing the gas flow resistance in the flow channels. This technical solution cannot solve the problem that the reverse diffusion of gas is blocked due to the removal of liquid water in the gas diffusion layer.

[0007] Another solution is to combine the design of the gas diffusion layer with the design of the flow channels, and design a region with higher hydrophilic characteristics at the corresponding position in the flow channels, in order to form a liquid water aggregation region and reduce the liquid water content at other sites. The problem with this technical solution is that it can only solve the accumulation of liquid water for a short time and cannot form the collection and management of liquid water in the long term. Summary of the Invention

[0008] The purpose of the present invention is to provide a membrane electrode assembly to solve the above technical problems.

[0009] Another purpose of the present invention is to provide a fuel cell provided with the membrane electrode assembly.

[0010] To achieve the above object, the membrane electrode assembly provided by the present invention includes a catalytic layer, a gas diffusion layer, and a bipolar plate. The gas diffusion layer includes a porous layer and a carbon paper layer. The porous layer is disposed adjacent to the catalytic layer, and the carbon paper layer is disposed adjacent to the bipolar plate. The bipolar plate has ridges distributed at intervals, and the top surface of the ridge is in contact with the carbon paper layer. The carbon paper layer has carbon paper hydrophilic regions distributed at intervals, and the porous layer has porous hydrophilic regions distributed at intervals. The porous hydrophilic regions correspond to the carbon paper hydrophilic regions. Part of each carbon paper hydrophilic region overlaps with a partial region of the corresponding ridge, and another part of the carbon paper hydrophilic region is located in the flow channel region of the bipolar plate.

[0011] Optionally, the hydrophilic property of the carbon paper hydrophilic region is equal to or higher than that of the porous hydrophilic region.

[0012] Optionally, the hydrophilic property of the ridge of the bipolar plate is higher than that of the carbon paper hydrophilic region.

[0013] Optionally, the hydrophilic property of the carbon paper hydrophilic region is higher than that of the region between the carbon paper hydrophilic regions, and the hydrophilic property of the porous hydrophilic region is higher than that of the region between the porous hydrophilic regions.

[0014] Optionally, the region between the carbon paper hydrophilic regions is a carbon paper hydrophobic region, and the region between the porous hydrophilic regions is a porous hydrophobic region.

[0015] Optionally, the width of the porous hydrophilic region is less than or equal to the width of the carbon paper hydrophilic region, and the projection of the porous hydrophilic region is within the range of the carbon paper hydrophilic region.

[0016] Optionally, the side of the porous hydrophilic region away from the ridge is aligned with the side of the carbon paper hydrophilic region away from the ridge, and the side of the porous hydrophilic region close to the ridge has an inward indentation distance relative to the side of the carbon paper hydrophilic region close to the ridge.

[0017] Optionally, the width of the porous hydrophilic region is less than the width of the carbon paper hydrophilic region, and the porous hydrophilic region is in a centered position relative to the carbon paper hydrophilic region.

[0018] Optionally, the width of the overlapping region between the carbon paper hydrophilic region and the ridge is greater than or equal to one half of the width of the ridge, and / or, the width of the carbon paper hydrophilic region above the flow channel region is less than the width of the flow channel region.

[0019] To achieve the above another object, the present invention provides a fuel cell, including a membrane electrode assembly, and the membrane electrode assembly is the membrane electrode assembly described in any one of the above.

[0020] By redesigning the hydrophilic regions in the gas diffusion layer, the present invention forms a channel for liquid water to flow from the catalyst layer to the surface of the flow channel, enabling the water management in the fuel cell to get rid of the previous disordered and random characteristics, achieving orderly liquid water management, and also leaving a relatively stable area for the reverse diffusion of air. Through the orderly water management in the gas diffusion layer, the ability to discharge liquid water in the fuel cell can be greatly improved, avoiding the power consumption of auxiliary devices caused by the high stoichiometric gas flow rate required to achieve the drainage ability, and improving the overall system efficiency at the system level; moreover, through the orderly water management in the gas diffusion layer, a better gas diffusion channel can be formed, thereby enhancing the performance of the stack at high current densities and improving the power generation efficiency of the stack.

[0021] The fuel cell provided by the present invention is provided with the membrane electrode assembly. Since the membrane electrode assembly has the above technical effects, the fuel cell provided with this membrane electrode assembly should also have corresponding technical effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic structural diagram of the membrane electrode assembly provided by the first embodiment of the present invention;

[0023] Figure 2 is Figure 1 a partial enlarged view of

[0024] Figure 3 is a schematic diagram comparing the widths of the porous hydrophilic region, the carbon paper hydrophilic region, and the top surface of the ridge from a top-down perspective;

[0025] Figure 4 is a partial enlarged view of the membrane electrode assembly provided by the second embodiment of the present invention.

[0026] In the figure:

[0027] 10 - catalyst layer; 20 - gas diffusion layer; 30 - bipolar plate; 31 - ridge; 32 - flow channel region; 21 - porous layer; 211 - porous hydrophilic region; 212 - porous hydrophobic region; 22 - carbon paper layer; 221 - carbon paper hydrophilic region; 222 - carbon paper hydrophobic region. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] In order to enable those skilled in the art to better understand the solution of the present invention, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0029] In this text, terms such as "upper, lower, inner, outer" are established based on the positional relationships shown in the drawings. Depending on the different drawings, the corresponding positional relationships may also change accordingly. Therefore, they should not be understood as absolute limitations on the protection scope. Moreover, relational terms such as "first" and "second" are only used to distinguish one component with the same name from another, and do not necessarily require or imply any such actual relationship or order between these components.

[0030] Please refer to Figure 1 、 Figure 2 , Figure 1 which is a schematic structural diagram of the membrane electrode assembly provided by the first embodiment of the present invention; Figure 2 is Figure 1 a partial enlarged view of

[0031] As shown in the figure, in a specific embodiment, in order to solve the contradiction between the occupation of the liquid water drainage space in the gas diffusion layer of the proton exchange membrane fuel cell and the reverse gas diffusion entry, the present invention provides a gas diffusion layer design that matches the bipolar plate flow channel structure, forms the collection of liquid water in the gas diffusion layer and the orderly drainage to the bipolar plate, and realizes the purpose of orderly water management in the gas diffusion layer.

[0032] Specifically, the membrane electrode assembly mainly consists of a catalyst layer 10, a gas diffusion layer 20, a bipolar plate 30, etc. Among them, the gas diffusion layer 20 is further divided into a porous layer 21 and a carbon paper layer 22. The porous layer 21 is arranged adjacent to the catalyst layer 10, and the carbon paper layer 22 is arranged adjacent to the bipolar plate 30. One side of the bipolar plate 30 facing the carbon paper layer has a plurality of spaced-apart ridges 31, and contacts the carbon paper layer 22 through the top surface of the ridges 31. The carbon paper layer 22 has spaced-apart carbon paper hydrophilic regions 221, and the porous layer 21 has spaced-apart porous hydrophilic regions 211. The porous hydrophilic regions 211 correspond to the carbon paper hydrophilic regions 221, and the carbon paper hydrophilic regions 221 correspond to the ridges 31 of the bipolar plate 30.

[0033] The carbon paper hydrophilic region 221 does not completely cover the area where the carbon paper contacts the ridge 31, but overlaps with a partial area of the ridge 31. At the same time, the area where the carbon paper hydrophilic region 221 does not overlap with the ridge 31 is located in the flow channel region 32 of the bipolar plate 30.

[0034] The hydrophilic property of the carbon paper hydrophilic region 221 is equal to or higher than that of the porous hydrophilic region 211. That is to say, the carbon paper layer 22 and the porous layer 21 in the gas diffusion layer 20 respectively have regions with higher hydrophilic properties and regions with lower hydrophilic degrees, and may have different regional distributions. In this embodiment, the area between adjacent carbon paper hydrophilic regions 221 can be designed as a carbon paper hydrophobic region 222, and the area between adjacent porous hydrophilic regions 211 can be designed as a porous hydrophobic region 212.

[0035] Please also refer to Figure 3 , Figure 3 which is a schematic diagram showing the width comparison of the porous hydrophilic region, the carbon paper hydrophilic region, and the top surface of the ridge from a top-down perspective.

[0036] As shown in the figure, the width L3 of the porous hydrophilic region 211 is smaller than the width L2 of the carbon paper hydrophilic region 221, and the projection of the porous hydrophilic region 211 is within the range of the carbon paper hydrophilic region 221. That is to say, the area of the porous hydrophilic region 211 can be different from the area of the carbon paper hydrophilic region 221, but the two regions overlap, and the edge of the porous hydrophilic region 211 is within the edge of the carbon paper hydrophilic region 221, so that the two can jointly form a channel for liquid water drainage by means of hydrophilic attraction.

[0037] In this embodiment, the side of the porous hydrophilic region 211 away from the ridge 31 is aligned with the side of the carbon paper hydrophilic region 221 away from the ridge 31. The side of the porous hydrophilic region 211 close to the ridge 31 is indented inward relative to the side of the carbon paper hydrophilic region 221 close to the ridge 31 by a distance ΔL = L2 - L3. Moreover, the width of the overlapping region between the carbon paper hydrophilic region 221 and the ridge 31 is greater than or equal to half of the width L1 of the ridge 31 to achieve a better balance between drainage and gas expansion.

[0038] Moreover, the width of the carbon paper hydrophilic region 221 above the flow channel region 32 is smaller than the width of the flow channel region 32. Thus, a state of "wet" on one side and "dry" on the other side can be formed on both sides of the ridge 31 of the bipolar plate 30. The "wet" state on one side can lead the liquid water out of the membrane electrode, and the "dry" state on the other side is conducive to the reverse diffusion of gas into the gas diffusion layer.

[0039] Since the hydrophilic property of the carbon paper hydrophilic region 221 is equal to or higher than that of the porous hydrophilic region 211, and at the same time, the hydrophilic property of the ridge 31 of the bipolar plate 30 is higher than that of the carbon paper hydrophilic region 221. Thus, a tendency for liquid water to automatically seep from the catalytic layer 10 to the porous layer 21 and further flow to the carbon paper layer 22 is formed. In the porous layer 21 or the carbon paper layer 22, liquid water also forms a tendency to flow from the porous hydrophobic region 212 and the carbon paper hydrophobic region 222 to the hydrophilic region (as shown by the arrows in the figure), and is discharged relatively concentratedly from the porous hydrophilic region 211 and the carbon paper hydrophilic region 221, thereby leaving enough channels for the gas to diffuse from the flow channel through the porous hydrophobic region 212 and the carbon paper hydrophobic region 222 of the gas diffusion layer 20 in the vertical direction into the catalytic layer 10.

[0040] After improvement, the orderly management of liquid water in the fuel cell is realized, and a relatively stable area is reserved for the reverse diffusion of air to enter. As a result, the ability to discharge liquid water in the fuel cell can be greatly improved, avoiding the power consumption of auxiliary devices caused by the high stoichiometric gas flow rate required to achieve the drainage ability, enhancing the performance of the fuel cell stack at high current density, improving the power generation efficiency of the fuel cell stack, and being able to improve the overall system efficiency at the system level.

[0041] Please continue to refer to Figure 4 , Figure 4 which is a partial enlarged view of the membrane electrode assembly provided in the second embodiment of the present invention.

[0042] As shown in the figure, compared with the first embodiment, the difference in this embodiment is that:

[0043] The width of the porous hydrophilic region 211 is smaller than the width of the carbon paper hydrophilic region 221, and the porous hydrophilic region 211 is in a centered position relative to the carbon paper hydrophilic region 221. That is to say, both sides of the porous hydrophilic region 211 are indented inward by a certain distance relative to both sides of the carbon paper hydrophilic region 221, and the object of the present invention can also be achieved.

[0044] In this embodiment, the same parts as those in the first embodiment are given the same reference numerals and the same textual descriptions are omitted.

[0045] The above embodiments are only the preferred solutions of the present invention, and are not specifically limited thereto. On this basis, targeted adjustments can be made according to actual needs to obtain different implementation manners. For example, the width of the porous hydrophilic region 211 is equal to the width of the carbon paper hydrophilic region 221, and so on. Since there are many possible implementation manners, they will not be enumerated one by one here.

[0046] In addition to the above membrane electrode assembly, the present invention also provides a fuel cell, including a membrane electrode assembly, and the membrane electrode assembly is the membrane electrode assembly described above. Specifically, the membrane electrode may have the above structural features on the cathode side gas diffusion layer, or the anode side has the above structural features, or both the cathode side and the anode side have the above structural features. For the remaining structures of the fuel cell, please refer to the prior art and will not be elaborated herein.

[0047] The above has introduced the membrane electrode assembly and fuel cell provided by the present invention in detail. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. Membrane electrode assembly, including a catalyst layer (10), a gas diffusion layer (20) and a bipolar plate (30), the gas diffusion layer (20) includes a porous layer (21) and a carbon paper layer (22), the porous layer (21) is disposed adjacent to the catalyst layer (10), the carbon paper layer (22) is disposed adjacent to the bipolar plate (30), the bipolar plate (30) has ridges (31) distributed at intervals, the top surface of the ridge (31) is in contact with the carbon paper layer (22), characterized in that, The carbon paper layer (22) has carbon paper hydrophilic regions (221) distributed at intervals, the porous layer (21) has porous hydrophilic regions (211) distributed at intervals, the porous hydrophilic regions (211) correspond to the carbon paper hydrophilic regions (221), and partial regions of each of the carbon paper hydrophilic regions (221) overlap with partial regions of the corresponding ridge portions (31), and another partial region of the carbon paper hydrophilic regions (221) is located in the flow channel region (32) of the bipolar plate (30).

2. The membrane electrode assembly according to claim 1, characterized in that, The hydrophilic property of the carbon paper hydrophilic regions (221) is equal to or higher than that of the porous hydrophilic regions (211), and the hydrophilic property of the porous hydrophilic regions (211) is higher than that of the catalyst layer (10).

3. The membrane electrode assembly according to claim 2, wherein, The hydrophilic property of the ridge portions (31) of the bipolar plate (30) is higher than that of the carbon paper hydrophilic regions (221).

4. The membrane electrode assembly according to claim 3, wherein The hydrophilic property of the carbon paper hydrophilic regions (221) is higher than that of the regions between the carbon paper hydrophilic regions (221), and the hydrophilic property of the porous hydrophilic regions (211) is higher than that of the regions between the porous hydrophilic regions (211).

5. The membrane electrode assembly according to claim 4, wherein, The regions between the carbon paper hydrophilic regions (221) are carbon paper hydrophobic regions (222), and the regions between the porous hydrophilic regions (211) are porous hydrophobic regions (212).

6. The membrane electrode assembly according to claim 1, wherein, The width of the porous hydrophilic regions (211) is less than or equal to the width of the carbon paper hydrophilic regions (221), and the projection of the porous hydrophilic regions (211) is within the range of the carbon paper hydrophilic regions (221).

7. The membrane electrode assembly according to claim 6, wherein, One side of the porous hydrophilic regions (211) away from the ridge portions (31) is aligned with one side of the carbon paper hydrophilic regions (221) away from the ridge portions (31), and one side of the porous hydrophilic regions (211) close to the ridge portions (31) has an inward indentation distance relative to one side of the carbon paper hydrophilic regions (221) close to the ridge portions (31).

8. The membrane electrode assembly according to claim 7, wherein, The width of the porous hydrophilic regions (211) is less than the width of the carbon paper hydrophilic regions (221), and the porous hydrophilic regions (211) are in a centered position relative to the carbon paper hydrophilic regions (221).

9. The membrane electrode assembly according to claim 1, wherein, The width of the overlapping region between the carbon paper hydrophilic regions (221) and the ridge portions (31) is greater than or equal to one half of the width of the ridge portions (31), and / or, the width of the carbon paper hydrophilic regions (221) above the flow channel region (32) is less than the width of the flow channel region (32).

10. A fuel cell, comprising a membrane electrode assembly, characterized in that, The membrane electrode assembly is the membrane electrode assembly according to any one of claims 1 to 9 above.

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