Lotus-leaf-like bipolar plate and self-draining method and fuel cell thereof

Abstract

The present application relates to a lotus leaf-like biomimetic bipolar plate, a self-draining method thereof and a fuel cell, the lotus leaf-like biomimetic bipolar plate comprising a bipolar plate body, a flow channel ridge, a flow channel, a branch flow channel, a confluence flow channel, a gas inlet and a gas outlet; the flow channel is provided with uniformly distributed micro flow fields; the micro flow field comprises uniformly distributed lotus leaf-like papilla structures. The lotus leaf-like biomimetic bipolar plate is provided with micro flow fields in the flow field and lotus leaf-like papilla structures in the micro flow field, so that the water generated by the reaction cannot be infiltrated in the flow field, but is separated by the lotus leaf-like papilla structures into the form of water droplets and slid out of the bipolar plate, the draining efficiency is improved, and the phenomenon of water flooding of the fuel cell is reduced.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen fuel cell manufacturing technology, and relates to a lotus leaf-like biomimetic bipolar plate, and more particularly to a lotus leaf-like biomimetic bipolar plate, its self-draining method, and a fuel cell. Background Technology

[0002] A proton exchange membrane fuel cell (PEMFC) is a green power generation device that directly converts the chemical energy stored in fuel and oxidant into electrical energy through an electrochemical reaction, producing only electrical energy, heat energy, and water as byproducts. It is not limited by the Carnot cycle and can achieve a power generation efficiency of around 60%. It features high power density, rapid start-up at room temperature, and flexibility, and has broad application prospects in electric vehicles, home power stations, and space stations.

[0003] The structure of a proton exchange membrane fuel cell mainly includes bipolar plates, a gas diffusion layer, a catalyst layer, and a proton exchange membrane. The bipolar plate, also known as the flow field plate, is a crucial component of the fuel cell, primarily functioning to uniformly distribute reactant gases, promptly remove generated water, facilitate heat conduction, and transfer electrons. The flow field is fabricated on the bipolar plate, and its design aims to ensure uniform reaction participation of the reactant gases throughout the plate while simultaneously removing generated water. Currently, parallel flow fields are commonly used for drainage. While parallel flow fields have numerous short channels and low flow resistance, during continuous operation, the gas velocity is low, and generated water tends to accumulate at the edges of the channels, leading to flooding and localized swelling of the membrane electrode assembly. This severely impacts the stability, durability, and efficiency of the fuel cell.

[0004] CN 109524684A discloses a fuel cell bipolar plate with biomimetic self-draining function and a self-draining method. This invention employs a method of forming primary ridges on the bipolar plate body, with microflow fields positioned between these ridges. Each microflow field has a partially frustum-shaped base, on which secondary and tertiary ridges and microchannels are formed. The tertiary ridges and microchannels constitute a bottom channel, and the microflow field possesses a self-draining mechanism. When water generated by the electrochemical reaction accumulates in the bottom channel of the microflow field, a thin film of liquid water forms on the bottom channel, and the water generated by the reaction is discharged through the bottom channel. When more water accumulates on the bottom channel, it gathers on the liquid water film without solid-liquid contact, and the water is discharged from the microflow field by sliding. This self-draining mechanism reduces the retention of liquid water between the channels, improves drainage efficiency, and thus makes the distribution of reactant gases more uniform between the channels, further improving gas mass transfer efficiency and enhancing the performance and stability of the fuel cell.

[0005] CN 213401255U relates to a biomimetic self-transporting drainage flow field for a proton exchange membrane fuel cell bipolar plate. Multiple flow channels are provided between the reactant gas inlet and outlet, and multiple transport blocks are sequentially spaced within each flow channel. Along the reactant gas flow direction, each transport block has a front transport block and a rear transport block, with a gap between them. A recess is formed between the front and rear transport blocks. The cross-section of the rear transport block gradually decreases from top to bottom. The rear transport block has corresponding first and second sidewalls. The first sidewall is located between the front and second sidewalls. A first recess is located in the middle of the first sidewall, and a first protrusion is located in the middle of the second sidewall. The orientation of both the first protrusion and the first recess is the same as the reactant gas flow direction. The second sidewall is perpendicular to the surface of the flow field body. This design improves the performance and stability of the proton exchange membrane fuel cell, laying the foundation for its further widespread application in fuel cell vehicles.

[0006] The above technical solutions all improve the structure of the bipolar plate. However, the secondary and tertiary ridge structures of the microflow field described in CN 109524684A are rectangular, which easily causes local accumulation of liquid water. Secondly, the rectangular structure of the tertiary ridge makes it unable to provide good support for liquid water droplets, thus making it difficult to effectively form the so-called liquid water film. In practical applications, the timely drainage of liquid water is not ideal. CN 213401255U has a large number of transport block structures, which is not conducive to processing and affects the battery current density. Secondly, the transport blocks mainly rely on capillary transport to achieve self-drainage, and the actual effect is not ideal.

[0007] Therefore, there is an urgent need to provide a bipolar plate structure to improve the above-mentioned technical problems. Summary of the Invention

[0008] In view of the problems existing in the prior art, the present invention provides a lotus leaf-like biomimetic bipolar plate, its self-draining method, and a fuel cell. By setting a micro-flow field and a lotus leaf-like papillary structure in the flow field, the water generated by the reaction cannot wet the interior of the flow field. Instead, it is separated into water droplets by the lotus leaf-like papillary structure and slid out of the bipolar plate, thereby improving drainage efficiency and reducing the phenomenon of water flooding in the fuel cell.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a lotus leaf-like biomimetic bipolar plate, the lotus leaf-like biomimetic bipolar plate comprising a bipolar plate body, a flow channel ridge, a flow channel, a branch flow channel, a confluence flow channel, an air inlet, and an air outlet; the flow channel is provided with a uniformly distributed microflow field; the microflow field includes a uniformly distributed lotus leaf-like papillary structure.

[0011] The lotus leaf-like biomimetic bipolar plate provided by this invention, through the establishment of micro-flow fields within the flow field, ensures that the water generated after the reaction is uniformly dispersed within each micro-flow field. Due to the lotus leaf-like papillary structures within the micro-flow fields, the water generated by the reaction cannot wet the flow field; instead, it is separated into droplets by the lotus leaf-like papillary structures and slides out of the bipolar plate. The bipolar plate structure provided by this invention improves drainage efficiency, reduces the flooding phenomenon in fuel cells, and further enhances gas mass transfer efficiency, which is beneficial for improving the gas utilization rate and stability of fuel cells.

[0012] Preferably, the surface of the microfluidic field has equally spaced lotus leaf-like papillae structures.

[0013] Preferably, the spacing between adjacent lotus leaf-like papillae is 20–30 μm, for example, it can be 20 μm, 22 μm, 24 μm, 26 μm, 28 μm or 30 μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0014] The spacing between the lotus leaf-like papillae structures provided by this invention is much smaller than the diameter of the water droplets formed. This ensures that the water droplets can only contact the lotus leaf-like papillae structures through the extremely thin air layer between them, and cannot contact the bottom of the microchannels, thus preventing them from wetting the channels and improving drainage efficiency.

[0015] Preferably, the diameter of the lotus leaf-like papillary structure is 10 to 20 μm, for example, it can be 10 μm, 12 μm, 14 μm, 16 μm, 18 μm or 20 μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0016] Preferably, the height of the lotus leaf-like papillary structure is 20-30 μm, for example, it can be 20 μm, 22 μm, 24 μm, 26 μm, 28 μm or 30 μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0017] Preferably, nanocrystal pillars are distributed at the apex of the lotus leaf-like papilla structure.

[0018] Preferably, the diameter of the nanocrystal pillar is 100 to 1000 nm, for example, it can be 100 nm, 300 nm, 500 nm, 700 nm, 900 nm or 1000 nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Preferably, the nanocrystal pillars are evenly spaced.

[0020] Preferably, the spacing between adjacent nanocrystal pillars is 200 to 500 nm, for example, it can be 200 nm, 250 nm, 300 nm, 400 nm, 450 nm or 500 nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] The water droplets generated by the reaction come into contact with the nanocrystal pillars to form a solid-liquid film. As the reaction proceeds, the continuously generated water slides out along the solid-liquid film. The formation of the solid-liquid film greatly reduces the resistance during sliding and further improves the drainage efficiency.

[0022] Preferably, the branching channel and the merging channel are parallel channels in space, with the two ends of the channels connected to the branching channel and the merging channel, respectively.

[0023] Preferably, the surfaces of the branching channel and the merging channel are each distributed with lotus leaf-like papillae structures at equal intervals.

[0024] Preferably, the microfluidic field further includes periodically arranged microchannels and microchannel ridges, with the microchannels located between two adjacent microchannel ridges.

[0025] Preferably, the number of microchannel ridges in the microfluidic field is 4 to 8, for example, 4, 5, 6, 7 or 8, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, the cross-section of the microchannel ridge is wavy.

[0027] The wavy surface of the microfluidic channel ridge is continuous and smooth, which greatly reduces the accumulation of water on the surface of the microfluidic field.

[0028] Preferably, the width of the microchannel ridge is 0.05 to 0.1 mm, for example, it can be 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm or 0.1 mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the height of the microchannel ridge is 0.2 to 0.5 mm, for example, it can be 0.2 mm, 0.25 mm, 0.3 mm, 0.4 mm, 0.45 mm or 0.5 mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, there is an inclination angle between the microflow field and the branching channel and / or between the microflow field and the merging channel.

[0031] Preferably, the tilt angle is 3 to 8°, for example, it can be 3°, 4°, 5°, 6°, 7° or 8°, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] The purpose of the tilt angle described in this invention is to facilitate the flow of the water generated by the reaction along the tilt angle to the confluence channel and the outlet, so as to facilitate its discharge from the lotus leaf-like bionic bipolar plate and further increase the drainage efficiency.

[0033] Preferably, the air inlet is located at the end of the diversion channel.

[0034] Preferably, the air outlet is located at the end of the confluence channel.

[0035] Preferably, the bipolar plate body comprises a planar plate.

[0036] Preferably, the material of the planar plate includes at least one of graphite, titanium, stainless steel, or composite material.

[0037] Preferably, the flow channel has a rectangular shape.

[0038] Preferably, the width of the flow channel is 0.5 to 1 mm, for example, it can be 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm or 1 mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Preferably, the shape of the flow channel ridge includes a rectangle.

[0040] Preferably, the width of the flow channel ridge is 0.5 to 1 mm, for example, it can be 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm or 1 mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] Preferably, the height of the flow channel ridge includes 0.5 to 2 mm, for example, it can be 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm or 2 mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] Secondly, a self-draining method for a lotus leaf-like biomimetic bipolar plate according to the first aspect, the self-draining method comprising the following steps:

[0043] (1) The reactant gas enters the split flow channel from the inlet and is split into the flow field;

[0044] (2) The reacting gases react within the flow field to produce water;

[0045] (3) After the generated water gathers into water droplets in the flow field, it flows into the confluence channel in a sliding manner and is discharged from the air outlet, thus completing the self-drainage.

[0046] Preferably, the sliding method in step (3) is as follows: the water droplet forms a solid-liquid film with the top of the lotus leaf-like papilla structure, and the water droplet slides on the solid-liquid film and flows into the confluence channel.

[0047] The self-drainage method provided by this invention reduces the phenomenon of liquid water stagnation in the flow field.

[0048] Thirdly, the present invention provides a fuel cell containing a lotus leaf-like biomimetic bipolar plate as described in the first aspect.

[0049] Based on the above technical solutions, the beneficial effects of the present invention are as follows:

[0050] (1) The lotus leaf-like biomimetic bipolar plate provided by the present invention, by setting micro-flow fields within the flow field, allows the water generated after the reaction to be uniformly dispersed within each micro-flow field. Due to the lotus leaf-like papilla structure set within the micro-flow field, the water generated by the reaction cannot wet the flow field, but is separated into droplets by the lotus leaf-like papilla structure and slides out of the bipolar plate. The structure of the bipolar plate improves drainage efficiency, reduces the phenomenon of water flooding in the fuel cell, and further improves the gas mass transfer efficiency, which is beneficial to improving the gas utilization rate and stability of the fuel cell.

[0051] (2) The spacing between the lotus leaf-like papillae structures provided by the present invention is much smaller than the diameter of the water droplets formed, so that the water droplets formed can only contact the lotus leaf-like papillae structures through the very thin air layer between the lotus leaf-like papillae structures, and cannot contact the bottom of the microchannel, thus failing to wet the channel and improving the drainage efficiency.

[0052] (3) The water droplets generated by the reaction come into contact with the nanocrystal pillars to form a solid-liquid film. As the reaction proceeds, the continuously generated water slides out along the solid-liquid film. The formation of the solid-liquid film greatly reduces the resistance during sliding and further improves the drainage efficiency.

[0053] (4) The present invention provides a continuous and smooth surface of the wavy microchannel ridge, which greatly reduces the accumulation of water on the surface of the microfluidic field.

[0054] (5) The purpose of the tilt angle mentioned in this invention is to facilitate the water generated by the reaction to flow along the tilt angle to the confluence channel to the outlet, so as to discharge it from the lotus leaf-like bionic bipolar plate and further increase the drainage efficiency.

[0055] (6) The self-drainage method provided by the present invention reduces the phenomenon of liquid water stagnation in the flow field. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the structure of the lotus leaf-like biomimetic bipolar plate provided by the present invention.

[0057] Figure 2 This is a schematic diagram of the microflow field structure provided by the present invention.

[0058] Figure 3 This is a schematic diagram of the lotus leaf-like papillary structure provided by the present invention.

[0059] Among them, 1-bipolar plate body, 2-flow channel ridge, 3-flow channel, 4-microflow field, 5-splitting flow channel, 6-merging flow channel, 7-air inlet, 8-air outlet, 9-microflow channel ridge, 10-microflow channel, 11-lotus leaf-like papillary structure, 12-nanocrystalline pillar. Detailed Implementation

[0060] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0061] Example 1

[0062] This embodiment provides a lotus leaf-inspired bionic bipolar plate ( Figure 1 The lotus leaf-like biomimetic bipolar plate includes a bipolar plate body 1 and a flow channel ridge 2. Figure 1 (white part in the middle), flow channel 3 ( Figure 1 (The black part in the middle), 5. Diverting flow channel, 6. Merging flow channel, 7. Inlet and 8.

[0063] The air inlet 7 is located at the end of the split channel 5, and the air outlet 8 is located at the end of the merging channel 6. The bipolar plate body 1 is a planar plate made of graphite. The split channel 5 and the merging channel 6 are parallel channels in space, and the two ends of the channel 3 are respectively connected to the split channel 5 and the merging channel 6.

[0064] The flow channel 3 is rectangular in shape and has a width of 0.75 mm. The flow channel ridge 2 is rectangular in shape and has a width of 0.75 mm. The height of the flow channel ridge 2 is 1 mm. The flow channel 3 and the flow channel ridge 2 are arranged periodically, and the flow channel 3 is located between adjacent flow channel ridges 2.

[0065] A uniformly distributed microflow field 4 is provided on the flow channel 3. Figure 2The microfluidic field further includes periodically arranged microchannel ridges 9 and microchannels 10, with a microchannel 10 between two adjacent microchannel ridges 9. The microfluidic field 4 has five microchannel ridges 9; the cross-section of each microchannel ridge 9 is wavy; the width of each microchannel ridge 9 is 0.08 mm; the height of each microchannel ridge 9 is 0.4 mm; and there is an inclination angle between the microfluidic field 4 and the branching channel 5 or the microfluidic field 4 and the merging channel 6; the inclination angle is 5°.

[0066] The surfaces of the microfluidic field 4, the diversion channel 5, and the merging channel 6 are equally spaced with lotus leaf-like papillae structures 11. Figure 3 The spacing between adjacent lotus leaf-like papillae 11 is 25 μm; the diameter of each lotus leaf-like papillae 11 is 15 μm; and the height is 25 μm. Nanocrystalline pillars 12 are distributed at the apex of each lotus leaf-like papillae structure; the diameter of each nanocrystalline pillar 12 is 500 nm; and the nanocrystalline pillars 12 are evenly spaced with a spacing of 300 nm.

[0067] The self-drainage method of the lotus leaf-inspired bionic bipolar plate includes the following steps:

[0068] (1) The reactant gas enters the split flow channel from the inlet and is split into the flow field;

[0069] (2) The reacting gases react within the flow field to produce water;

[0070] (3) After the generated water gathers into water droplets in the flow field, the water droplets form a solid-liquid film with the top of the lotus leaf-like papilla structure. The water droplets slide on the solid-liquid film and flow into the confluence channel, and are discharged from the air outlet, thus completing the self-drainage.

[0071] Example 2

[0072] This embodiment provides a lotus leaf-inspired bionic bipolar plate ( Figure 1 The lotus leaf-like biomimetic bipolar plate includes a bipolar plate body 1, a flow channel ridge 2, a flow channel 3, a branch flow channel 5, a confluence flow channel 6, an air inlet 7, and an air outlet 8.

[0073] The air inlet 7 is located at the end of the split channel 5, and the air outlet 8 is located at the end of the merging channel 6. The bipolar plate body 1 is a planar plate made of titanium. The split channel 5 and the merging channel 6 are parallel channels in space, and the two ends of the channel 3 are respectively connected to the split channel 5 and the merging channel 6.

[0074] The flow channel 3 is rectangular in shape and has a width of 0.5 mm. The flow channel ridge 2 is rectangular in shape and has a width of 0.5 mm. The flow channel ridge 2 has a height of 0.5 mm. The flow channel 3 and the flow channel ridge 2 are arranged periodically, and the flow channel 3 is located between adjacent flow channel ridges 2.

[0075] A uniformly distributed microflow field 4 is provided on the flow channel 3. Figure 2 The microfluidic field further includes periodically arranged microchannel ridges 9 and microchannels 10, with a microchannel 10 between two adjacent microchannel ridges 9. The microfluidic field 4 has four microchannel ridges 9; the cross-section of each microchannel ridge 9 is wavy; the width of each microchannel ridge 9 is 0.05 mm; the height of each microchannel ridge 9 is 0.2 mm; the microfluidic field 4 has an inclination angle with the branching channel 5 or the merging channel 6; the inclination angle is 3°.

[0076] The surfaces of the microfluidic field 4, the diversion channel 5, and the merging channel 6 are equally spaced with lotus leaf-like papillae structures 11. Figure 3 The spacing between adjacent lotus leaf-like papillae 11 is 20 μm; the diameter of each lotus leaf-like papillae 11 is 10 μm; and the height is 20 μm. Nanocrystalline pillars 12 are distributed at the apex of each lotus leaf-like papillae structure; the diameter of each nanocrystalline pillar 12 is 100 nm; and the nanocrystalline pillars 12 are evenly spaced with a spacing of 200 nm.

[0077] The self-drainage method of the lotus leaf-inspired bionic bipolar plate includes the following steps:

[0078] (1) The reactant gas enters the split flow channel from the inlet and is split into the flow field;

[0079] (2) The reacting gases react within the flow field to produce water;

[0080] (3) After the generated water gathers into water droplets in the flow field, the water droplets form a solid-liquid film with the top of the lotus leaf-like papilla structure. The water droplets slide on the solid-liquid film and flow into the confluence channel, and are discharged from the air outlet, thus completing the self-drainage.

[0081] Example 3

[0082] This embodiment provides a lotus leaf-inspired bionic bipolar plate ( Figure 1 The lotus leaf-like biomimetic bipolar plate includes a bipolar plate body 1, a flow channel ridge 2, a flow channel 3, a branch flow channel 5, a confluence flow channel 6, an air inlet 7, and an air outlet 8.

[0083] The air inlet 7 is located at the end of the split channel 5, and the air outlet 8 is located at the end of the merging channel 6. The bipolar plate body 1 is a flat plate made of stainless steel. The split channel 5 and the merging channel 6 are parallel channels in space, and the two ends of the channel 3 are respectively connected to the split channel 5 and the merging channel 6.

[0084] The flow channel 3 is rectangular in shape and has a width of 1 mm. The flow channel ridge 2 is rectangular in shape and has a width of 1 mm and a height of 2 mm. The flow channel 3 and the flow channel ridge 2 are arranged periodically, and the flow channel 3 is located between adjacent flow channel ridges 2.

[0085] A uniformly distributed microflow field 4 is provided on the flow channel 3. Figure 2 The microfluidic field further includes periodically arranged microchannel ridges 9 and microchannels 10, with a microchannel 10 between two adjacent microchannel ridges 9. The microfluidic field 4 has eight microchannel ridges 9; the cross-section of each microchannel ridge 9 is wavy; the width of each microchannel ridge 9 is 0.1 mm, and the height is 0.5 mm; the microfluidic field 4 has an inclination angle of 8° with the branching channel 5 or the merging channel 6.

[0086] The surfaces of the microfluidic field 4, the diversion channel 5, and the merging channel 6 are equally spaced with lotus leaf-like papillae structures 11. Figure 3 The spacing between adjacent lotus leaf-like papillae 11 is 30 μm; the diameter of each lotus leaf-like papillae 11 is 20 μm and its height is 30 μm. Nanocrystalline pillars 12 are distributed at the apex of each lotus leaf-like papillae structure; the diameter of each nanocrystalline pillar 12 is 1000 nm; the nanocrystalline pillars 12 are evenly spaced with a spacing of 500 nm.

[0087] The self-drainage method of the lotus leaf-inspired bionic bipolar plate includes the following steps:

[0088] (1) The reactant gas enters the split flow channel from the inlet and is split into the flow field;

[0089] (2) The reacting gases react within the flow field to produce water;

[0090] (3) After the generated water gathers into water droplets in the flow field, the water droplets form a solid-liquid film with the top of the lotus leaf-like papilla structure. The water droplets slide on the solid-liquid film and flow into the confluence channel, and are discharged from the air outlet, thus completing the self-drainage.

[0091] Example 4

[0092] This embodiment provides a lotus leaf-like biomimetic bipolar plate, which is the same as that in Embodiment 1 except that the top of the lotus leaf-like papillary structure does not have nanocrystal pillars.

[0093] Example 5

[0094] This embodiment provides a lotus leaf-like biomimetic bipolar plate, which is the same as that in Embodiment 1 except that the distribution of the lotus leaf-like papillary structures is uneven and irregular.

[0095] Example 6

[0096] This embodiment provides a lotus leaf-like biomimetic bipolar plate, which is the same as that in Embodiment 1 except that the microchannel ridge is rectangular.

[0097] Comparative Example 1

[0098] This comparative example provides a bipolar plate, which is obtained according to CN 109524684A.

[0099] Comparative Example 2

[0100] This comparative example provides a bipolar plate, which is the same as in Example 1 except that the surface of the microchannel does not have a lotus leaf-like papillary structure.

[0101] The above bipolar plates were assembled into a fuel cell according to GB / T 38954-2020, and power generation experiments were conducted. The results are as follows.

[0102] The bipolar plate structure provided in Examples 1-3 improves drainage efficiency, prevents flooding, and eliminates the accumulation of reaction-generated water within the bipolar plate during use, thereby improving gas mass transfer efficiency and enhancing the gas utilization rate and stability of the fuel cell.

[0103] In Example 4, since there are no nanocrystalline pillars at the top of the papillary structure, the water generated by the reaction only has a small contact area with the top of the papillary structure. This makes it difficult for the water generated by the reaction to be supported by the top of the papillary structure in the flow state to form a solid-liquid film. Consequently, the water generated by the reaction accumulates inside the flow channel, which can easily cause flooding.

[0104] In Example 5, the uneven distribution of the papillary structure leads to uneven contact forces between the reaction-generated water and the papillary structure, which is not conducive to the formation of a stable solid-liquid film and easily causes the solid-liquid film to rupture. Consequently, the reaction water cannot be discharged from the flow field in time, thus causing flooding.

[0105] In Example 6, the ridge of the microchannel is rectangular, which leads to an increase in the corner area of ​​the microchannel. Water is easily generated in the corner area, which can easily cause local water flooding of the membrane electrode.

[0106] In Comparative Example 1, the secondary and tertiary ridges of the microflow field are rectangular, which easily causes liquid water to accumulate locally. Secondly, the rectangular structure of the tertiary ridge makes it unable to provide good support for liquid water droplets, thus making it difficult to effectively form the so-called liquid water film. In practical applications, its timely drainage effect on liquid water is not ideal.

[0107] In Comparative Example 2, the absence of a papillary structure allows the water generated in the reaction to come into direct contact with the surface of the microchannel. This makes it easier for the water droplets to adhere to the surface of the microchannel, which also increases the resistance to liquid flow and reduces the flow velocity of the water generated in the reaction.

[0108] In summary, the lotus leaf-like biomimetic bipolar plate provided by this invention, by setting up micro-flow fields within the flow field, ensures that the water generated after the reaction is uniformly dispersed within each micro-flow field. Due to the lotus leaf-like papillary structures set within the micro-flow fields, the water generated by the reaction cannot wet the flow field; instead, it is separated into droplets by the lotus leaf-like papillary structures and slides out of the bipolar plate. The bipolar plate structure provided by this invention improves drainage efficiency, reduces the phenomenon of flooding in fuel cells, and further improves gas mass transfer efficiency, which is beneficial to improving the gas utilization rate and stability of fuel cells.

[0109] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A lotus leaf-inspired biomimetic bipolar plate, characterized in that, The lotus leaf-like biomimetic bipolar plate includes a bipolar plate body, a flow channel ridge, a flow channel, a branch flow channel, a confluence flow channel, an air inlet, and an air outlet; a uniformly distributed microflow field is provided on the flow channel; the microflow field includes a uniformly distributed lotus leaf-like papillary structure; The flow channel has a rectangular shape and a width of 0.5-1 mm; the flow channel ridge has a rectangular shape and a width of 0.5-1 mm and a height of 0.5-2 mm. There is an inclination angle between the microflow field and the branch channel and / or between the microflow field and the confluence channel; The microfluidic field also includes periodically arranged microchannels and microchannel ridges, with the microchannels located between two adjacent microchannel ridges. The cross-section of the microchannel ridge is wavy; the width of the microchannel ridge is 0.05~0.1mm, and the height is 0.2~0.5mm; The lotus leaf-like papillae structure has nanocrystalline pillars distributed at its apex; The surface of the microfluidic field has equally spaced lotus leaf-like papillae structures; The surfaces of the split flow channel and the merging flow channel are respectively distributed with lotus leaf-like papillae structures at equal intervals; The spacing between adjacent lotus leaf-like papillae is 20~30μm.

2. The lotus leaf-like biomimetic bipolar plate according to claim 1, characterized in that, The diameter of the lotus leaf-like papillary structure is 10~20μm.

3. The lotus leaf-like biomimetic bipolar plate according to claim 1, characterized in that, The height of the lotus leaf-like papillary structure is 20~30μm.

4. The lotus leaf-like biomimetic bipolar plate according to claim 1, characterized in that, The diameter of the nanocrystal pillar is 100~1000nm.

5. The lotus leaf-like biomimetic bipolar plate according to claim 1, characterized in that, The nanocrystal pillars are distributed at equal intervals.

6. The lotus leaf-like biomimetic bipolar plate according to claim 1, characterized in that, The spacing between adjacent nanocrystal pillars is 200~500nm.

7. The lotus leaf-like biomimetic bipolar plate according to claim 1, characterized in that, The branching channel and the merging channel are parallel channels in space, with the two ends of the channels connected to the branching channel and the merging channel, respectively.

8. The lotus leaf-like biomimetic bipolar plate according to claim 1, characterized in that, The number of microchannel ridges in the microfluidic field is 4 to 8.

9. The lotus leaf-like biomimetic bipolar plate according to claim 1, characterized in that, The tilt angle is 3~8°.

10. The lotus leaf-like biomimetic bipolar plate according to claim 1, characterized in that, The air inlet is located at the end of the diversion channel.

11. The lotus leaf-like biomimetic bipolar plate according to claim 1, characterized in that, The air outlet is located at the end of the confluence channel.

12. The lotus leaf-like biomimetic bipolar plate according to claim 1, characterized in that, The bipolar plate body includes a planar plate.

13. The lotus leaf-like biomimetic bipolar plate according to claim 12, characterized in that, The material of the flat plate includes at least one of graphite, titanium, stainless steel, or composite material.

14. A self-draining method for a lotus leaf-like biomimetic bipolar plate according to any one of claims 1-13, characterized in that, The self-drainage method includes the following steps: (1) The reactant gas enters the split flow channel from the inlet and is split into the flow field; (2) The reacting gases react within the flow field to produce water; (3) After the generated water gathers into water droplets in the flow field, it flows into the confluence channel in a sliding manner and is discharged from the air outlet, thus completing the self-drainage.

15. The self-drainage method of the lotus leaf-like biomimetic bipolar plate according to claim 14, characterized in that, The sliding method in step (3) is as follows: the water droplet forms a solid-liquid film with the top of the lotus leaf-like papilla structure, and the water droplet slides on the solid-liquid film and flows into the confluence channel.

16. A fuel cell, characterized in that, The fuel cell contains a lotus leaf-like biomimetic bipolar plate as described in any one of claims 1-13.

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