CN114068948A - Fuel cell bipolar plate with bionic active water collection and drainage function and water collection and drainage method - Google Patents
Fuel cell bipolar plate with bionic active water collection and drainage function and water collection and drainage method Download PDFInfo
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Abstract
The invention discloses a fuel cell bipolar plate with a bionic active water collection and drainage function and a water collection and drainage method. According to the invention, a low surface energy film with a hydrophobic characteristic of a low adhesion effect imitating the lotus leaf surface is formed on the wall surface of a flow field, the low surface energy film is etched to form a periodically arranged hydrophilic pattern imitating the hydrophilicity of cactus thorns, and the wall surface after hydrophobic treatment is etched with the hydrophilic pattern to form a bionic surface imitating the coupling of the hydrophilicity and the hydrophobicity of the back of the desert beetle; when the water yield of the fuel cell is less than the water demand, the product water can be effectively captured and collected and uniformly distributed, so that the proton conductivity of the proton exchange membrane is enhanced; when the water yield of the fuel cell is greater than the water demand, liquid drops accumulated on the surface of the gas diffusion layer can be sucked out and trapped on the bionic surface of the wall surface of the flow field, and the water drainage speed of the flow field is accelerated through the synergistic effect of active water drainage of the bionic surface and air flow dragging, so that the mass transfer efficiency is enhanced, and the performance and the stability of the fuel cell are improved.
Description
Technical Field
The invention relates to a fuel cell technology, in particular to a fuel cell bipolar plate with a bionic active water collection and drainage function and a water collection and drainage method.
Background
The fuel cell is a power generation device which directly converts chemical energy of fuel into electric energy, the process is not limited by Carnot cycle, and the fuel cell has the advantages of high energy conversion efficiency, zero emission and no pollution, and is regarded as the most promising power generation technology. Fuel cells represented by Proton Exchange Membrane Fuel Cells (PEMFCs) have the outstanding advantages of modular structural units, simple and convenient assembly, high specific power and reliability, and the like, and are applied to the fields of transportation, energy, military, aerospace, and the like. However, water management issues for pem fuel cells have been one of the key issues limiting their lifetime and performance. During normal operation of a pem fuel cell, the internal electrochemical reactions continue to produce product water on the cathode side of the fuel cell. On the one hand, proton exchange membranes require a certain amount of water to increase their proton conductivity; on the other hand, excessive product water accumulates in the channels of the cathode bipolar plate of the fuel cell, causing flooding. Therefore, a stable and balanced water environment needs to be maintained inside the fuel cell, which is related to whether the fuel cell can be operated smoothly and efficiently.
The bipolar plate is one of important components of mass transfer drainage of the fuel cell and plays an important role in maintaining the water balance inside the fuel cell. Currently, there are three main areas of improvement in bipolar plates for fuel cell water management issues: 1. the bipolar plate has the structural design, such as a 3D flow field, a composite flow field and the like, so that the air flow speed in the flow field is enhanced, the air flow flowing state is changed, and the drainage capacity is enhanced. The defects are obvious, the processing difficulty and the cost of the bipolar plate are undoubtedly increased by the design of a complex flow field, and the bipolar plate is not beneficial to large-scale popularization and use; 2. the bipolar plate surface modification treatment is to process hydrophilic and hydrophobic coatings on the bipolar plate surface based on physical vapor deposition, chemical vapor deposition, electroplating and other technologies, and to improve the water management problem of the fuel cell by utilizing the wetting state of product water in different flow channels. The defects of the treatment mode are not negligible, no matter which coating processing technology is adopted, the treatment mode is still a runner with single wettability, passive drainage is carried out by relying on the purging effect of high-speed airflow in the runner, and extreme phenomena of flooding (hydrophilic coating) and drying (hydrophobic coating) of the battery are easily caused, so that the treatment mode becomes the hidden troubles of performance reduction and unstable operation of the battery.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a fuel cell bipolar plate with a bionic active water collection and drainage function and a water collection and drainage method, which are inspired by organisms in the nature, and the functional surface with the characteristics of ultra-hydrophobic low adhesion on the lotus leaf surface, directional water transportation of prickly pear thorns and high-efficiency water collection on the back of desert beetles is processed in the flow field of the fuel cell bipolar plate, so that the fuel cell bipolar plate has the functions of active capture and water drainage, the mass transfer capacity of the fuel cell bipolar plate is improved, the drainage efficiency of the fuel cell bipolar plate is enhanced, the smooth progress of the electrochemical reaction of the fuel cell is ensured, and the performance of the cell is improved.
The invention aims to provide a fuel cell bipolar plate with a bionic active water collection and drainage function.
The fuel cell includes: bipolar plate, gas diffusion layer and catalyst layer and proton exchange membrane; the proton exchange membrane is positioned in the center, and the two sides of the proton exchange membrane are respectively provided with a cathode catalyst layer, an anode catalyst layer, a cathode gas diffusion layer, an anode gas diffusion layer and a cathode bipolar plate and an anode bipolar plate which are symmetrically distributed from inside to outside.
The fuel cell bipolar plate with bionic active water collection and drainage functions comprises: the bipolar plate comprises a bipolar plate main body, a main flow channel, an upper flow distribution channel, a lower flow combination channel, a gas inlet and a gas outlet; wherein, the main body of the bipolar plate is a flat plate; a plurality of main flow channels which are periodically distributed are engraved on the front surface of the bipolar plate main body; an upper flow distribution channel and a lower flow combination channel which are communicated with each main channel are respectively engraved on the front surface of the bipolar plate main body and at the upper end and the lower end of each main channel, and each main channel, each upper flow distribution channel and each lower flow combination channel jointly form a flow field; each main flow channel, the upper flow distribution channel and the lower flow combination channel is provided with a first side wall, a second side wall and a bottom wall, the first side wall and the second side wall are vertical to the surface of the bipolar plate main body, and the bottom wall is parallel to the surface of the bipolar plate main body; an air inlet is arranged at one end of the upper flow distribution channel, and an air outlet is arranged at the other end of the lower flow combination channel opposite to the upper flow distribution channel; performing hydrophobic treatment on the first and second side walls and a bottom wall of each main flow channel, the upper flow distribution channel and the lower flow combination channel to form a low-surface-energy film which has the hydrophobic characteristic of low adhesion effect of the lotus leaf-like surface, so that the first and second side walls and the bottom wall form a hydrophobic surface with the hydrophobic characteristic; performing partial laser etching on the low surface energy film on the first side wall, etching off part of the low surface energy film, exposing part of the surface of the bipolar plate main body, forming a micro-scale and nano-scale concave-convex structure on the surface, enabling the etched area to have a hydrophilic characteristic, and forming a plurality of vertical hydrophilic patterns which are periodically arranged along the airflow transmission direction, so that a hydrophobic surface and the vertical hydrophilic patterns are formed on the surface of the first side wall and are alternately arranged, and each vertical hydrophilic pattern is in a vertical trapezoid shape; the upper bottom and the lower bottom of the vertical trapezoid are along the airflow transmission direction, the height is in the horizontal direction and is consistent with the depth of the first side wall, the upper bottom is aligned with the front edge of the first side wall, the lower bottom is aligned with the bottom edge of the first side wall, the upper side waist is not larger than the lower side waist, so that the vertical trapezoid is an isosceles trapezoid or has downward inclination along the airflow transmission direction, and the arrangement period of the plurality of vertical hydrophilic patterns is larger than that of the lower bottom of the vertical trapezoid; performing partial laser etching on the low surface energy film of the second side wall, etching off part of the low surface energy film, exposing part of the surface of the bipolar plate main body, forming a micro-scale and nano-scale concave-convex structure on the surface, enabling the etched area to have hydrophilic characteristics, and forming a plurality of vertical hydrophilic patterns which are periodically arranged along the airflow transmission direction, so that a hydrophobic surface and the vertical hydrophilic patterns are formed on the surface of the second side wall and are alternately arranged, the vertical hydrophilic pattern of each second side wall is the same as the vertical hydrophilic pattern of the first side wall, the arrangement period of the vertical hydrophilic patterns of the second side wall is the same as that of the vertical hydrophilic patterns of the first side wall, and the vertical hydrophilic patterns corresponding to the first and second side walls are aligned or arranged in a staggered manner; performing partial laser etching on the low surface energy film of the bottom wall, etching off partial low surface energy film, exposing partial surface of the bipolar plate main body, and forming a micro-scale and nano-scale concave-convex structure on the surface, so that the etched area has a hydrophilic characteristic, thereby forming a plurality of horizontal hydrophilic patterns which are periodically arranged along the airflow transmission direction, thereby forming a hydrophobic surface and horizontal hydrophilic patterns which are alternately arranged on the surface of the bottom wall, wherein the shape of each horizontal hydrophilic pattern is a horizontal trapezoid; the upper bottom and the lower bottom of the horizontal trapezoid are perpendicular to the airflow transmission direction, the height is along the airflow transmission direction, the period of a horizontal hydrophilic pattern of the bottom wall is consistent with the height of the horizontal trapezoid, the horizontal hydrophilic pattern is communicated, so that water is drained smoothly, and product water is uniformly distributed on the bottom wall of the flow field; the etched vertical hydrophilic patterns and horizontal hydrophilic patterns are in a trapezoid shape imitating cactus spines, liquid drops can generate unbalanced Laplace pressure on the two sides of the upper bottom and the lower bottom of the trapezoid, one side of the upper bottom is higher than one side of the lower bottom, the liquid drops can spontaneously move from the upper bottom to the lower bottom of the trapezoid, and the water transport function is achieved in an oriented mode; furthermore, periodic vertical hydrophilic patterns and horizontal hydrophilic patterns are etched on the side wall and the bottom wall of the flow field after hydrophobic treatment, so that the hydrophobic property and the hydrophilic property are combined, hydrophilic and hydrophobic coupled bionic surfaces on the back of the desert beetle are formed on the surfaces of the side wall and the bottom wall of the flow field, liquid drops are swept and rolled to the hydrophilic surface by airflow in a flow channel on the lotus leaf-like low-adhesion hydrophobic surface to be trapped, and the high-efficiency water collection function is achieved;
when the fuel cell works, reaction gas enters a flow field through the gas inlet and is distributed in each main flow channel through the upper flow dividing channels, and the transmission direction of the reaction gas in the flow field is the gas flow transmission direction; the reaction gas further passes through the gas diffusion layer to reach the catalyst layer to start electrochemical reaction, then product water enters the gas diffusion layer and is accumulated on the surface of the gas diffusion layer on one side facing the flow field, the product water comprises liquid drops and also small fog drops, and then the liquid drops on the surface of the gas diffusion layer and the small fog drops carried by the gas flow in the flow field are trapped by the vertical hydrophilic patterns on the first side wall and the second side wall and the horizontal hydrophilic pattern on the bottom wall; when the water demand of the fuel cell is greater than the water yield, the trapped product water adheres to the vertical and horizontal hydrophilic patterns and is uniformly distributed and stored on the surfaces of the first and second side walls and the bottom wall of the flow field in the form of water films, so that the water content of the fuel cell is kept, and the phenomenon of drying of a proton exchange membrane of the fuel cell is prevented; when the water demand of the fuel cell is less than the water production, the trapped water accumulates on the vertical and horizontal hydrophilic patterns, which are asymmetric with respect to the gas flow transport direction causing uneven surface tension of the water itself, and the upper bottoms of the vertical and horizontal hydrophilic patterns are smaller than the lower bottoms, so that the laplace pressure of the liquid droplets at the front sides of the vertical and horizontal hydrophilic patterns is greater than the laplace pressure at the bottom sides, thereby causing a laplace pressure difference; under the action of self-uneven surface tension, Laplace pressure difference and surface low slip resistance of the water film, the product water starts to actively move directionally along the airflow transmission direction; the product water captured on the vertical and horizontal hydrophilic patterns in the flow field is actively and directionally moved to the air outlet and is dragged by the airflow shearing force in the same direction in the flow field, so that the speed of discharging the excessive product water from the flow field is further accelerated, the problem of water flooding of the fuel cell is greatly solved, the mass transfer efficiency of the fuel cell is enhanced, and the performance and the stability of the fuel cell are improved.
The upper bottom of the trapezoid is smaller than the lower bottom.
Performing hydrophobic treatment on the first side wall, the second side wall and the bottom wall of the main runner by adopting a laser etching and chemical reagent soaking modification method to form a low-surface-energy film; firstly, performing laser etching to form a micro-scale and nano-scale concave-convex structure, wherein the working parameters of the laser etching are that the scanning speed is 100-1000 mm/s, the spot diameter is 10-50 mu m, the scanning interval is 10-50 mu m, and the processing power is 10-30 w; then carrying out chemical reagent soaking modification to form a low surface energy film on the concave-convex structure; the chemical agent is soaked in 0.5-2 wt.% ethanol solution of fluorosilane or stearic acid, and the low surface energy film is a fluorosilane or stearic acid film. Through hydrophobic treatment, the static contact angles of the two side walls and the bottom wall of the main runner are more than 135 degrees, and the rolling angle is less than 5 degrees.
The bipolar plate main body is made of one of graphite, aluminum, nickel, titanium and stainless steel.
The flow field is one of a parallel flow field, a snake-shaped smooth flow field, an interdigital flow field, a composite flow field and a bionic flow field.
The cross sections of the main flow channel, the upper flow distribution channel and the lower flow combination channel are rectangular, the width of the main flow channel is 0.5 mm-3.0 mm, and the depth of the main flow channel is 0.5 mm-3.0 mm.
Processing vertical hydrophilic patterns and horizontal hydrophilic patterns on two side walls and a bottom wall of the flow channel after the hydrophobic treatment by using a laser etching method again, and controlling a laser scanning area and laser working parameters according to a set pattern: the scanning speed is 100mm/s-1000mm/s, the spot diameter is 10 μm-50 μm, the scanning interval is 10 μm-50 μm, and the processing power is 10w-30 w;
the static contact angle of the vertical hydrophilic pattern formed by etching is below 5 degrees; the horizontal hydrophilic pattern static contact angle is below 5 degrees; the length of the upper bottom of the vertical hydrophilic pattern is 0 mm-3 mm, the length of the lower bottom is 1 mu m-3 mm, the period is 1 mm-5 mm, and the wedge angle is 1-30 degrees; the length of the upper bottom of the horizontal hydrophilic pattern is 0 mm-3 mm, the lower bottom is 1 μm-3 mm, the height is 1 mm-10 mm, and the wedge angle is 1-30 degrees.
The invention also aims to provide a water collecting and draining method of the fuel cell bipolar plate with the bionic active water collecting and draining function.
The invention relates to a water collecting and draining method of a fuel cell bipolar plate with a bionic active water collecting and draining function, which comprises the following steps:
1) preparing a fuel cell bipolar plate:
a) providing a flat bipolar plate main body;
b) a plurality of main flow channels which are periodically distributed are engraved on the front surface of the bipolar plate main body; an upper flow distribution channel and a lower flow combination channel which are communicated with each main channel are respectively engraved on the front surface of the bipolar plate main body and at the upper end and the lower end of each main channel, and each main channel, each upper flow distribution channel and each lower flow combination channel jointly form a flow field; each main flow channel, the upper flow distribution channel and the lower flow combination channel is provided with a first side wall, a second side wall and a bottom wall, the first side wall and the second side wall are vertical to the surface of the bipolar plate main body, and the bottom wall is parallel to the surface of the bipolar plate main body;
c) an air inlet is arranged at one end of the upper flow distribution channel, and an air outlet is arranged at the other end of the lower flow combination channel opposite to the upper flow distribution channel;
d) performing hydrophobic treatment on the first and second side walls and a bottom wall of each main flow channel, the upper flow distribution channel and the lower flow combination channel to form a low-surface-energy film which has the hydrophobic characteristic of low adhesion effect of the lotus leaf-like surface, so that the first and second side walls and the bottom wall form a hydrophobic surface with the hydrophobic characteristic;
e) performing partial laser etching on the low surface energy films on the first side walls of the main flow channels, the upper shunt flow channels and the lower confluence flow channels, etching off partial low surface energy films, exposing partial surfaces of the bipolar plate main body, and forming a micro-scale and nano-scale concave-convex structure on the surfaces, so that the etched areas have hydrophilic characteristics, and a plurality of vertical hydrophilic patterns which are periodically arranged along the airflow transmission direction are formed, so that a hydrophobic surface and the vertical hydrophilic patterns are alternately arranged on the surface of the first side wall, and each vertical hydrophilic pattern is in a vertical trapezoid shape; the upper bottom and the lower bottom of the vertical trapezoid are along the airflow transmission direction, the height is in the horizontal direction and is consistent with the depth of the first side wall, the upper bottom is aligned with the front edge of the first side wall, the lower bottom is aligned with the bottom edge of the first side wall, the upper side waist is not larger than the lower side waist, so that the vertical trapezoid is an isosceles trapezoid or has downward inclination along the airflow transmission direction, and the arrangement period of the plurality of vertical hydrophilic patterns is larger than that of the lower bottom of the vertical trapezoid; performing partial laser etching on the low surface energy film of the second side wall, etching off part of the low surface energy film, exposing part of the surface of the bipolar plate main body, forming a micro-scale and nano-scale concave-convex structure on the surface, enabling the etched area to have hydrophilic characteristics, and forming a plurality of vertical hydrophilic patterns which are periodically arranged along the airflow transmission direction, so that a hydrophobic surface and the vertical hydrophilic patterns are formed on the surface of the second side wall and are alternately arranged, the vertical hydrophilic pattern of each second side wall is the same as the vertical hydrophilic pattern of the first side wall, the arrangement period of the vertical hydrophilic patterns of the second side wall is the same as that of the vertical hydrophilic patterns of the first side wall, and the vertical hydrophilic patterns corresponding to the first and second side walls are aligned or arranged in a staggered manner; performing partial laser etching on the low surface energy film of the bottom wall, etching off partial low surface energy film, exposing partial surface of the bipolar plate main body, and forming a micro-scale and nano-scale concave-convex structure on the surface, so that the etched area has a hydrophilic characteristic, thereby forming a plurality of horizontal hydrophilic patterns which are periodically arranged along the airflow transmission direction, thereby forming a hydrophobic surface and horizontal hydrophilic patterns which are alternately arranged on the surface of the bottom wall, wherein the shape of each horizontal hydrophilic pattern is a horizontal trapezoid; the upper bottom and the lower bottom of the horizontal trapezoid are perpendicular to the airflow transmission direction, the height is along the airflow transmission direction, the period of a horizontal hydrophilic pattern of the bottom wall is consistent with the height of the horizontal trapezoid, the horizontal hydrophilic pattern is communicated, so that water is drained smoothly, and product water is uniformly distributed on the bottom wall of the flow field; the etched vertical hydrophilic patterns and horizontal hydrophilic patterns are in a trapezoid shape imitating cactus spines, liquid drops can generate unbalanced Laplace pressure on the two sides of the upper bottom and the lower bottom of the trapezoid, one side of the upper bottom is higher than one side of the lower bottom, the liquid drops can spontaneously move from the upper bottom to the lower bottom of the trapezoid, and the water transport function is achieved in an oriented mode;
f) etching periodic vertical hydrophilic patterns and horizontal hydrophilic patterns on the side wall and the bottom wall of the flow field after hydrophobic treatment to combine the hydrophobic characteristic and the hydrophilic characteristic, so that hydrophilic and hydrophobic coupled bionic surfaces on the back of the desert-imitating beetle are formed on the surfaces of the side wall and the bottom wall of the flow field, liquid drops are swept and rolled on the lotus leaf-imitated low-adhesion hydrophobic surface by airflow in a flow channel until the hydrophilic surface is trapped, and the high-efficiency water collection function is achieved;
2) when the fuel cell works, reaction gas enters a flow field through the gas inlet and is distributed in each main flow channel through the upper flow dividing channels, and the transmission direction of the reaction gas in the flow field is the gas flow transmission direction;
3) the reaction gas further passes through the gas diffusion layer to reach the catalyst layer to start electrochemical reaction, then product water enters the gas diffusion layer and is accumulated on the surface of the gas diffusion layer on one side facing the flow field, the product water comprises liquid drops and also small fog drops, and then the liquid drops on the surface of the gas diffusion layer and the small fog drops carried by the gas flow in the flow field are trapped by the vertical hydrophilic patterns on the first side wall and the second side wall and the horizontal hydrophilic pattern on the bottom wall;
4) when the water demand of the fuel cell is greater than the water yield, the trapped product water adheres to the vertical and horizontal hydrophilic patterns and is uniformly distributed and stored on the surfaces of the first and second side walls and the bottom wall of the flow field in the form of water films, so that the water content of the fuel cell is kept, and the phenomenon of drying of a proton exchange membrane of the fuel cell is prevented;
5) when the water demand of the fuel cell is less than the water production, the trapped water accumulates on the vertical and horizontal hydrophilic patterns, which are asymmetric with respect to the gas flow transport direction causing uneven surface tension of the water itself, and the upper bottoms of the vertical and horizontal hydrophilic patterns are smaller than the lower bottoms, so that the laplace pressure of the liquid droplets at the front sides of the vertical and horizontal hydrophilic patterns is greater than the laplace pressure at the bottom sides, thereby causing a laplace pressure difference; under the action of self-uneven surface tension, Laplace pressure difference and surface low slip resistance of the water film, the product water starts to actively move directionally along the airflow transmission direction; the product water captured on the vertical and horizontal hydrophilic patterns in the flow field is actively and directionally moved to the air outlet and is dragged by the airflow shearing force in the same direction in the flow field, so that the speed of discharging the excessive product water from the flow field is further accelerated, the problem of water flooding of the fuel cell is greatly solved, the mass transfer efficiency of the fuel cell is enhanced, and the performance and the stability of the fuel cell are improved.
In the step 1) d), performing hydrophobic treatment on the first and second side walls and the bottom wall of each main flow channel, the upper flow distribution channel and the lower flow combination channel by using a laser etching and chemical reagent soaking modification method to form the low surface energy film, and the method comprises the following steps: firstly, performing laser etching to form a micro-scale and nano-scale concave-convex structure, wherein the working parameters of the laser etching are that the scanning speed is 100-1000 mm/s, the spot diameter is 10-50 mu m, the scanning interval is 10-50 mu m, and the processing power is 10-30 w; then carrying out chemical reagent soaking modification to form a low surface energy film on the concave-convex structure; the chemical agent is soaked in 0.5-2 wt.% ethanol solution of fluorosilane or stearic acid, and the low surface energy film is fluorosilane or stearic acid. Through hydrophobic treatment, the static contact angles of the two side walls and the bottom wall of the main runner are more than 135 degrees, and the rolling angle is less than 5 degrees.
In step e), performing partial laser etching on the low surface energy films on the first and second side walls and the bottom wall of each main flow channel, the upper shunt flow channel and the lower confluence flow channel, and etching off part of the low surface energy films by laser so as to expose part of the surface of the bipolar plate main body and form a micro-scale and nano-scale concave-convex structure on the surface, so that the etched region has a hydrophilic characteristic, and the method comprises the following steps: the facula focus on the low surface energy film surface of first and second lateral wall and diapire respectively with the laser, later according to the vertical hydrophilic pattern and the hydrophilic pattern demarcation of level that set for well for the scope of laser etching, carries out laser etching to the scope of ruling at last, the operating parameter of laser etching: the scanning speed is 100mm/s-1000mm/s, the spot diameter is 10 μm-50 μm, the scanning interval is 10 μm-50 μm, and the processing power is 10w-30 w; through laser etching treatment, the static contact angle of the vertical hydrophilic pattern and the horizontal hydrophilic pattern is below 10 degrees.
The invention has the advantages that:
the invention has the capability of actively trapping and removing water; when the water yield of the fuel cell is less than the water demand, the bionic surface on the wall surface of the flow field can effectively collect and uniformly distribute the product water by utilizing the high adhesion effect of the hydrophilic surface and the product water, so that the phenomenon that the proton exchange membrane lacks water in the initial working stage of the fuel cell is relieved, the proton conductivity of the proton exchange membrane is enhanced, and the performance of the fuel cell is improved; when the water yield of the fuel cell is greater than the water demand, liquid drops accumulated on the surface of the gas diffusion layer can be sucked out and trapped on the bionic surface of the wall surface of the flow field, and the drainage speed of the flow field is accelerated through the synergistic effect of active drainage of the bionic surface and dragging of air flow, so that the transmission resistance of reaction gas in the flow field is reduced, the mass transfer efficiency of the bipolar plate is enhanced, and the performance and the stability of the fuel cell are further improved.
Drawings
FIG. 1 is a schematic diagram of one embodiment of a bipolar plate of a fuel cell with bionic active water collection and drainage function according to the present invention;
FIG. 2 is a schematic diagram of a first sidewall of a fuel cell bipolar plate with bionic active water collection and drainage function according to an embodiment of the present invention, wherein (a) is a schematic diagram in which an upper side waist is equal to a lower side waist, and (b) is a schematic diagram in which the upper side waist is smaller than the lower side waist;
fig. 3 is a schematic view of the bottom wall of one embodiment of the bipolar plate of the fuel cell with bionic active water collection and drainage function of the invention.
Detailed Description
The invention will be further elucidated by means of specific embodiments in the following with reference to the drawing.
As shown in fig. 1, the bipolar plate of a fuel cell with bionic active water collection and drainage function and the water collection and drainage method of the present embodiment include: the bipolar plate comprises a bipolar plate main body 1, a main flow channel 2, an upper flow distribution channel 3, a lower flow combination channel 4, an air inlet 5 and an air outlet 6; wherein, the bipolar plate main body 1 is a flat plate; a plurality of main flow channels 2 which are periodically and vertically arranged are engraved on the front surface of the bipolar plate main body 1; an upper flow distribution channel 3 and a lower flow combination channel 4 which are communicated with each main channel 2 and are vertical to the main channel 2 are respectively engraved on the front surface of the bipolar plate main body 1 and at the upper end and the lower end of the main channel 2, each upper flow distribution channel 3 and each lower flow combination channel 4 jointly form a flow field, and the type of the flow field is a parallel flow field; each of the main flow channels 2, the upper shunt flow channels 3 and the lower confluence flow channels 4 has first and second side walls perpendicular to the surface of the bipolar plate body 1 and a bottom wall parallel to the surface of the bipolar plate body 1; an air inlet 5 is arranged at one end of the upper flow distribution channel 3, and an air outlet 6 is arranged at the other end of the lower flow combination channel 4 opposite to the upper flow distribution channel; performing hydrophobic treatment on the first and second side walls and a bottom wall of each main flow channel 2, the upper flow dividing flow channel 3 and the lower flow combining flow channel 4 to form a low surface energy film which has hydrophobic characteristics simulating the low adhesion effect of the lotus leaf surface, so that the first and second side walls and the bottom wall form hydrophobic surfaces with hydrophobic characteristics; performing partial laser etching on the low surface energy film of the first side wall, etching off part of the low surface energy film, exposing out part of the surface of the high surface energy film of the bipolar plate main body 1, forming a micro-scale and nano-scale concave-convex structure on the surface, enabling the etched area to have a hydrophilic characteristic, and forming a plurality of vertical hydrophilic patterns which are periodically arranged along the airflow transmission direction, so that a hydrophobic surface and the vertical hydrophilic patterns are alternately arranged on the surface of the first side wall, wherein each vertical hydrophilic pattern is in a vertical trapezoid shape; the upper bottom and the lower bottom of the vertical trapezoid are along the airflow transmission direction, the height is in the horizontal direction, the height is consistent with the depth of the first side wall, the upper bottom is aligned with the front edge of the first side wall, the lower bottom is aligned with the bottom edge of the first side wall, the upper side waist is equal to the lower side waist which is in an isosceles trapezoid shape, namely, two bottom angles are equal, as shown in fig. 2(a), or the upper side waist is smaller than the lower side waist so as to have downward inclination along the airflow transmission direction, as shown in fig. 2(b), the upper bottom angle is larger than the lower bottom angle by 0-90 degrees, and the arrangement period of the plurality of vertical hydrophilic patterns is larger than the lower bottom of the vertical trapezoid; performing partial laser etching on the low surface energy film of the second side wall, etching off part of the low surface energy film, exposing part of the surface of the high surface energy film of the bipolar plate main body 1, forming a micro-scale and nano-scale concave-convex structure on the surface, enabling the etched area to have hydrophilic characteristics, and forming a plurality of vertical hydrophilic patterns which are periodically arranged along the airflow transmission direction, so that a hydrophobic surface and the vertical hydrophilic patterns are formed on the surface of the second side wall and are alternately arranged, the vertical hydrophilic pattern of each second side wall is the same as the vertical hydrophilic pattern of the first side wall, the arrangement period of the vertical hydrophilic patterns of the second side wall is the same as that of the vertical hydrophilic patterns of the first side wall, and the vertical hydrophilic patterns corresponding to the first and second side walls are aligned or arranged in a staggered manner; performing partial laser etching on the low surface energy film of the bottom wall, etching off part of the low surface energy film, exposing part of the surface of the high surface energy film of the bipolar plate main body 1, and forming a micro-scale and nano-scale concave-convex structure on the surface, so that the etched area has a hydrophilic characteristic, thereby forming a plurality of horizontal hydrophilic patterns which are periodically arranged along the airflow transmission direction, thereby forming a hydrophobic surface and horizontal hydrophilic patterns which are alternately arranged on the surface of the bottom wall, wherein the shape of each horizontal hydrophilic pattern is a horizontal trapezoid, as shown in fig. 3; the upper bottom and the lower bottom of the horizontal trapezoid are perpendicular to the airflow transmission direction, the height is along the airflow transmission direction, the period of a horizontal hydrophilic pattern of the bottom wall is consistent with the height of the horizontal trapezoid, the horizontal hydrophilic pattern is communicated, so that water is drained smoothly, and product water is uniformly distributed on the bottom wall of the flow field; the etched vertical hydrophilic patterns and horizontal hydrophilic patterns are in a trapezoid shape imitating cactus spines, liquid drops can generate unbalanced Laplace pressure on the two sides of the upper bottom and the lower bottom of the trapezoid, one side of the upper bottom is higher than one side of the lower bottom, the liquid drops can spontaneously move from the upper bottom to the lower bottom of the trapezoid, and the water transport function is achieved in an oriented mode; periodic vertical hydrophilic patterns and horizontal hydrophilic patterns are etched on the side wall and the bottom wall of the flow field after hydrophobic treatment, so that the hydrophobic property and the hydrophilic property are combined, hydrophilic and hydrophobic coupled bionic surfaces on the back of the desert-imitating beetle are formed on the surfaces of the side wall and the bottom wall of the flow field, liquid drops are swept and rolled to the hydrophilic surface by airflow in a flow channel on the lotus leaf-imitating low-adhesion hydrophobic surface to be trapped, and the high-efficiency water collection function is achieved.
In the present embodiment, the material of the bipolar plate body is graphite; the type of the flow field is a parallel flow field; the cross-sectional shapes of the main runner, the upper flow distribution runner and the lower flow combination runner are rectangular, the width of the main runner is 2.0mm, and the depth of the main runner is 2.0 mm. The length of the upper bottom of the vertical hydrophilic pattern is 2mm, the length of the lower bottom is 2.4mm, and the wedge angle alpha is 5 degrees or 15 degrees; the length of the upper base of the horizontal hydrophilic pattern is 0.5mm, the length of the lower base is 1.9mm, the height is 8mm, and the wedge angle alpha is 5 degrees or 15 degrees.
The water collecting and draining method of the fuel cell bipolar plate with the bionic active water collecting and draining function comprises the following steps of:
1) preparing a fuel cell bipolar plate:
a) providing a flat bipolar plate main body, wherein the material is graphite;
b) a plurality of main flow channels which are periodically and vertically arranged are engraved on the front surface of the bipolar plate main body; an upper flow distribution channel and a lower flow combination channel which are communicated with each main channel and are vertical to the main channels are respectively engraved on the front surface of the bipolar plate main body and at the upper end and the lower end of each main channel, and each main channel, each upper flow distribution channel and each lower flow combination channel jointly form a flow field;
each main flow channel, the upper flow distribution channel and the lower flow combination channel is provided with a first side wall, a second side wall and a bottom wall, the first side wall and the second side wall are vertical to the surface of the bipolar plate main body, and the bottom wall is parallel to the surface of the bipolar plate main body;
c) an air inlet is arranged at one end of the upper flow dividing flow passage, and an outlet is arranged at the other end of the lower flow combining flow passage opposite to the upper flow dividing flow passage
A gas port;
d) the first side wall, the second side wall and the bottom wall of each main flow channel, the upper flow distribution channel and the lower flow combination channel are subjected to hydrophobic treatment to form a low-surface-energy film which has the hydrophobic characteristic of lotus leaf surface-imitated low adhesion effect, so that the first side wall, the second side wall and the bottom wall form a hydrophobic surface with the hydrophobic characteristic:
firstly, performing laser etching to form a micro-scale and nano-scale concave-convex structure, wherein the working parameters of the laser etching are that the scanning speed is 500mm/s, the spot diameter is 10 mu m, the scanning interval is 10 mu m, and the processing power is 10 w; then carrying out chemical reagent soaking modification to form a low surface energy film on the concave-convex structure; 1 wt.% of chemical agent soaking
The low surface energy film is fluorosilane or stearic acid, and the static contact angles of two side walls and the bottom wall of the main runner are 159 degrees and the rolling angles are 2 degrees after hydrophobic treatment;
e) performing partial laser etching on the low surface energy films of the first and second side walls and the bottom wall, etching off partial low surface energy films, exposing the surface of partial high surface energy film of the bipolar plate main body, and forming a micro-scale and nano-scale concave-convex structure on the surface, so that the etched area has a hydrophilic characteristic, and a plurality of vertical hydrophilic patterns and horizontal hydrophilic patterns which are periodically arranged along the air flow transmission direction are formed: focusing laser spots on the hydrophobic surfaces of the first side wall, the second side wall and the bottom wall respectively, then taking the designed vertical hydrophilic pattern and the horizontal hydrophilic pattern to define a laser etching range, and finally etching the defined range, wherein the working parameters of the laser etching are that the scanning speed is 500mm/s, the diameter of the laser spot is 10 mu m, the scanning distance is 10 mu m, and the processing power is 10 w;
after laser etching treatment, the static contact angle of the vertical hydrophilic pattern and the horizontal hydrophilic pattern is 5 degrees;
2) when the fuel cell works, reaction gas enters a flow field through the gas inlet and is distributed in each main flow channel through the upper flow dividing channels, and the transmission direction of the reaction gas in the flow field is the gas flow transmission direction;
3) the reaction gas further passes through the gas diffusion layer to reach the catalyst layer to start electrochemical reaction, then product water enters the gas diffusion layer and is accumulated on the surface of the gas diffusion layer on one side facing the flow field, the product water comprises liquid drops and also small fog drops, and then the liquid drops on the surface of the gas diffusion layer and the small fog drops carried by the gas flow in the flow field are trapped by the vertical hydrophilic patterns on the first side wall and the second side wall and the horizontal hydrophilic pattern on the bottom wall;
4) when the water demand of the fuel cell is greater than the water yield, the trapped product water adheres to the vertical and horizontal hydrophilic patterns and is uniformly distributed and stored on the surfaces of the first and second side walls and the bottom wall of the flow field in the form of water films, so that the fuel cell maintains certain water content and the proton exchange membrane of the fuel cell is prevented from drying;
5) when the water demand of the fuel cell is less than the water production, the trapped water accumulates on the vertical and horizontal hydrophilic patterns, which are asymmetric with respect to the gas flow transport direction causing uneven surface tension of the water itself, and the upper bottoms of the vertical and horizontal hydrophilic patterns are smaller than the lower bottoms, so that the laplace pressure of the liquid droplets at the front sides of the vertical and horizontal hydrophilic patterns is greater than the laplace pressure at the bottom sides, thereby causing a laplace pressure difference; under the action of self-uneven surface tension, Laplace pressure difference and surface low slip resistance of the water film, the product water starts to actively move directionally along the airflow transmission direction; the product water trapped on the vertical and horizontal hydrophilic patterns in the flow field is actively and directionally moved to the air outlet and is dragged by the shearing force of the airflow in the same direction in the flow field, so that the speed of discharging the excessive product water from the flow field is further accelerated, the problem of flooding of the fuel cell is greatly relieved, the mass transfer efficiency of the fuel cell is enhanced,
the performance and stability of the fuel cell are improved.
Finally, it is noted that the disclosed embodiments are intended to aid in further understanding of the invention, but those skilled in the art will appreciate that: various substitutions and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the invention should not be limited to the embodiments disclosed, but the scope of the invention is defined by the appended claims.
Claims (10)
1. A fuel cell bipolar plate with bionic active water collection and drainage functions is characterized by comprising: the bipolar plate comprises a bipolar plate main body, a main flow channel, an upper flow distribution channel, a lower flow combination channel, a gas inlet and a gas outlet; wherein, the main body of the bipolar plate is a flat plate; a plurality of main flow channels which are periodically distributed are engraved on the front surface of the bipolar plate main body; an upper flow distribution channel and a lower flow combination channel which are communicated with each main channel are respectively engraved on the front surface of the bipolar plate main body and at the upper end and the lower end of each main channel, and each main channel, each upper flow distribution channel and each lower flow combination channel jointly form a flow field; each main flow channel, the upper flow distribution channel and the lower flow combination channel is provided with a first side wall, a second side wall and a bottom wall, the first side wall and the second side wall are vertical to the surface of the bipolar plate main body, and the bottom wall is parallel to the surface of the bipolar plate main body; an air inlet is arranged at one end of the upper flow distribution channel, and an air outlet is arranged at the other end of the lower flow combination channel opposite to the upper flow distribution channel; performing hydrophobic treatment on the surfaces of the first and second side walls and the bottom wall of each main flow channel, the upper flow distribution channel and the lower flow combination channel to form a low-surface-energy film which has the hydrophobic characteristic of low adhesion effect of the lotus leaf-like surface, so that the first and second side walls and the bottom wall form a hydrophobic surface with the hydrophobic characteristic; performing partial laser etching on the low surface energy film on the first side wall, etching off part of the low surface energy film, exposing part of the surface of the bipolar plate main body, forming a micro-scale and nano-scale concave-convex structure on the surface, enabling the etched area to have a hydrophilic characteristic, and forming a plurality of vertical hydrophilic patterns which are periodically arranged along the airflow transmission direction, so that a hydrophobic surface and the vertical hydrophilic patterns are formed on the surface of the first side wall and are alternately arranged, and each vertical hydrophilic pattern is in a vertical trapezoid shape; the upper bottom and the lower bottom of the vertical trapezoid are along the airflow transmission direction, the height of the vertical trapezoid is perpendicular to the airflow transmission direction, the height of the vertical trapezoid is consistent with the depth of the first side wall, the upper bottom is aligned with the front edge of the first side wall, the lower bottom is aligned with the bottom edge of the first side wall, the upper side waist is not larger than the lower side waist, so that the vertical trapezoid is an isosceles trapezoid or has downward inclination along the airflow transmission direction, and the arrangement period of the plurality of vertical hydrophilic patterns is larger than that of the lower bottom of the vertical trapezoid; performing partial laser etching on the low surface energy film of the second side wall, etching off part of the low surface energy film, exposing part of the surface of the bipolar plate main body, forming a micro-scale and nano-scale concave-convex structure on the surface, enabling the etched area to have hydrophilic characteristics, and forming a plurality of vertical hydrophilic patterns which are periodically arranged along the airflow transmission direction, so that a hydrophobic surface and the vertical hydrophilic patterns are formed on the surface of the second side wall and are alternately arranged, the vertical hydrophilic pattern of each second side wall is the same as the vertical hydrophilic pattern of the first side wall, the arrangement period of the vertical hydrophilic patterns of the second side wall is the same as that of the vertical hydrophilic patterns of the first side wall, and the vertical hydrophilic patterns corresponding to the first and second side walls are aligned or arranged in a staggered manner; performing partial laser etching on the low surface energy film of the bottom wall, etching off partial low surface energy film, exposing partial surface of the bipolar plate main body, and forming a micro-scale and nano-scale concave-convex structure on the surface, so that the etched area has a hydrophilic characteristic, thereby forming a plurality of horizontal hydrophilic patterns which are periodically arranged along the airflow transmission direction, thereby forming a hydrophobic surface and horizontal hydrophilic patterns which are alternately arranged on the surface of the bottom wall, wherein the shape of each horizontal hydrophilic pattern is a horizontal trapezoid; the upper bottom and the lower bottom of the horizontal trapezoid are perpendicular to the airflow transmission direction, the height is along the airflow transmission direction, the period of a horizontal hydrophilic pattern of the bottom wall is consistent with the height of the horizontal trapezoid, the horizontal hydrophilic pattern is communicated, so that water is drained smoothly, and product water is uniformly distributed on the bottom wall of the flow field; the etched vertical hydrophilic patterns and horizontal hydrophilic patterns are in a trapezoid shape imitating cactus spines, liquid drops can generate unbalanced Laplace pressure on the two sides of the upper bottom and the lower bottom of the trapezoid, one side of the upper bottom is higher than one side of the lower bottom, the liquid drops can spontaneously move from the upper bottom to the lower bottom of the trapezoid, and the water transport function is achieved in an oriented mode; furthermore, periodic vertical hydrophilic patterns and horizontal hydrophilic patterns are etched on the side wall and the bottom wall of the flow field after hydrophobic treatment, so that the hydrophobic property and the hydrophilic property are combined, hydrophilic and hydrophobic coupled bionic surfaces on the back of the desert beetle are formed on the surfaces of the side wall and the bottom wall of the flow field, liquid drops are swept and rolled to the hydrophilic surface by airflow in a flow channel on the lotus leaf-like low-adhesion hydrophobic surface to be trapped, and the high-efficiency water collection function is achieved;
when the fuel cell works, reaction gas enters a flow field through the gas inlet and is distributed in each main flow channel through the upper flow dividing channels, and the transmission direction of the reaction gas in the flow field is the gas flow transmission direction; the reaction gas further passes through the gas diffusion layer to reach the catalyst layer to start electrochemical reaction, then product water enters the gas diffusion layer and is accumulated on the surface of the gas diffusion layer on one side facing the flow field, the product water comprises liquid drops and also small fog drops, and then the liquid drops on the surface of the gas diffusion layer and the small fog drops carried by the gas flow in the flow field are trapped by the vertical hydrophilic patterns on the first side wall and the second side wall and the horizontal hydrophilic pattern on the bottom wall; when the water demand of the fuel cell is greater than the water yield, the trapped product water adheres to the vertical and horizontal hydrophilic patterns and is uniformly distributed and stored on the surfaces of the first and second side walls and the bottom wall of the flow field in the form of water films, so that the water content of the fuel cell is kept, and the phenomenon of drying of a proton exchange membrane of the fuel cell is prevented; when the water demand of the fuel cell is less than the water production, the trapped water accumulates on the vertical and horizontal hydrophilic patterns, which are asymmetric with respect to the gas flow transport direction causing uneven surface tension of the water itself, and the upper bottoms of the vertical and horizontal hydrophilic patterns are smaller than the lower bottoms, so that the laplace pressure of the liquid droplets at the front sides of the vertical and horizontal hydrophilic patterns is greater than the laplace pressure at the bottom sides, thereby causing a laplace pressure difference; under the action of self-uneven surface tension, Laplace pressure difference and surface low slip resistance of the water film, the product water starts to actively move directionally along the airflow transmission direction; the product water captured on the vertical and horizontal hydrophilic patterns in the flow field is actively and directionally moved to the air outlet and is dragged by the airflow shearing force in the same direction in the flow field, so that the speed of discharging the excessive product water from the flow field is further accelerated, the problem of water flooding of the fuel cell is greatly solved, the mass transfer efficiency of the fuel cell is enhanced, and the performance and the stability of the fuel cell are improved.
2. The fuel cell bipolar plate of claim 1, wherein the material of the bipolar plate body is one of graphite, aluminum, nickel, titanium, and stainless steel.
3. The fuel cell bipolar plate of claim 1, wherein said flow field is of one of a parallel flow field, a serpentine flow field, an interdigitated flow field, a composite flow field, and a biomimetic flow field.
4. The fuel cell bipolar plate of claim 1, wherein the vertical hydrophilic pattern has a length of an upper base of 0mm to 3mm, a length of a lower base of 1 μm to 3mm, a period of 1mm to 5mm, and a wedge angle of 1 ° to 30 °; the length of the upper bottom of the horizontal hydrophilic pattern is 0 mm-3 mm, the lower bottom is 1 μm-3 mm, the height is 1 mm-10 mm, and the wedge angle is 1-30 degrees.
5. The water collecting and draining method for the fuel cell bipolar plate with bionic active water collecting and draining function according to claim 1, characterized by comprising the following steps:
1) preparing a fuel cell bipolar plate:
a) providing a flat bipolar plate main body;
b) a plurality of main flow channels which are periodically distributed are engraved on the front surface of the bipolar plate main body; an upper flow distribution channel and a lower flow combination channel which are communicated with each main channel are respectively engraved on the front surface of the bipolar plate main body and at the upper end and the lower end of each main channel, and each main channel, each upper flow distribution channel and each lower flow combination channel jointly form a flow field; each main flow channel, the upper flow distribution channel and the lower flow combination channel is provided with a first side wall, a second side wall and a bottom wall, the first side wall and the second side wall are vertical to the surface of the bipolar plate main body, and the bottom wall is parallel to the surface of the bipolar plate main body;
c) an air inlet is arranged at one end of the upper flow distribution channel, and an air outlet is arranged at the other end of the lower flow combination channel opposite to the upper flow distribution channel;
d) performing hydrophobic treatment on the surfaces of the first and second side walls and the bottom wall of each main flow channel, the upper flow distribution channel and the lower flow combination channel to form a low-surface-energy film which has the hydrophobic characteristic of low adhesion effect of the lotus leaf-like surface, so that the first and second side walls and the bottom wall form a hydrophobic surface with the hydrophobic characteristic;
e) performing partial laser etching on the low surface energy films on the first side walls of the main flow channels, the upper shunt flow channels and the lower confluence flow channels, etching off partial low surface energy films, exposing partial surfaces of the bipolar plate main body, and forming a micro-scale and nano-scale concave-convex structure on the surfaces, so that the etched areas have hydrophilic characteristics, and a plurality of vertical hydrophilic patterns which are periodically arranged along the airflow transmission direction are formed, so that a hydrophobic surface and the vertical hydrophilic patterns are alternately arranged on the surface of the first side wall, and each vertical hydrophilic pattern is in a vertical trapezoid shape; the upper bottom and the lower bottom of the vertical trapezoid are along the airflow transmission direction, the height of the vertical trapezoid is perpendicular to the airflow transmission direction, the height of the vertical trapezoid is consistent with the depth of the first side wall, the upper bottom is aligned with the front edge of the first side wall, the lower bottom is aligned with the bottom edge of the first side wall, the upper side waist is not larger than the lower side waist, so that the vertical trapezoid is an isosceles trapezoid or has downward inclination along the airflow transmission direction, and the arrangement period of the plurality of vertical hydrophilic patterns is larger than that of the lower bottom of the vertical trapezoid; performing partial laser etching on the low surface energy film of the second side wall, etching off part of the low surface energy film, exposing part of the surface of the bipolar plate main body, forming a micro-scale and nano-scale concave-convex structure on the surface, enabling the etched area to have hydrophilic characteristics, and forming a plurality of vertical hydrophilic patterns which are periodically arranged along the airflow transmission direction, so that a hydrophobic surface and the vertical hydrophilic patterns are formed on the surface of the second side wall and are alternately arranged, the vertical hydrophilic pattern of each second side wall is the same as the vertical hydrophilic pattern of the first side wall, the arrangement period of the vertical hydrophilic patterns of the second side wall is the same as that of the vertical hydrophilic patterns of the first side wall, and the vertical hydrophilic patterns corresponding to the first and second side walls are aligned or arranged in a staggered manner; performing partial laser etching on the low surface energy film of the bottom wall, etching off partial low surface energy film, exposing partial surface of the bipolar plate main body, and forming a micro-scale and nano-scale concave-convex structure on the surface, so that the etched area has a hydrophilic characteristic, thereby forming a plurality of horizontal hydrophilic patterns which are periodically arranged along the airflow transmission direction, thereby forming a hydrophobic surface and horizontal hydrophilic patterns which are alternately arranged on the surface of the bottom wall, wherein the shape of each horizontal hydrophilic pattern is a horizontal trapezoid; the upper bottom and the lower bottom of the horizontal trapezoid are perpendicular to the airflow transmission direction, the height is along the airflow transmission direction, the period of a horizontal hydrophilic pattern of the bottom wall is consistent with the height of the horizontal trapezoid, the horizontal hydrophilic pattern is communicated, so that water is drained smoothly, and product water is uniformly distributed on the bottom wall of the flow field; the etched vertical hydrophilic patterns and horizontal hydrophilic patterns are in a trapezoid shape imitating cactus spines, liquid drops can generate unbalanced Laplace pressure on the two sides of the upper bottom and the lower bottom of the trapezoid, one side of the upper bottom is higher than one side of the lower bottom, the liquid drops can spontaneously move from the upper bottom to the lower bottom of the trapezoid, and the water transport function is achieved in an oriented mode;
f) etching periodic vertical hydrophilic patterns and horizontal hydrophilic patterns on the side wall and the bottom wall of the flow field after hydrophobic treatment to combine the hydrophobic characteristic and the hydrophilic characteristic, so that hydrophilic and hydrophobic coupled bionic surfaces on the back of the desert-imitating beetle are formed on the surfaces of the side wall and the bottom wall of the flow field, liquid drops are swept and rolled on the lotus leaf-imitated low-adhesion hydrophobic surface by airflow in a flow channel until the hydrophilic surface is trapped, and the high-efficiency water collection function is achieved;
2) when the fuel cell works, reaction gas enters a flow field through the gas inlet and is distributed in each main flow channel through the upper flow dividing channels, and the transmission direction of the reaction gas in the flow field is the gas flow transmission direction;
3) the reaction gas further passes through the gas diffusion layer to reach the catalyst layer to start electrochemical reaction, then product water enters the gas diffusion layer and is accumulated on the surface of the gas diffusion layer on one side facing the flow field, the product water comprises liquid drops and also small fog drops, and then the liquid drops on the surface of the gas diffusion layer and the small fog drops carried by the gas flow in the flow field are trapped by the vertical hydrophilic patterns on the first side wall and the second side wall and the horizontal hydrophilic pattern on the bottom wall;
4) when the water demand of the fuel cell is greater than the water yield, the trapped product water adheres to the vertical and horizontal hydrophilic patterns and is uniformly distributed and stored on the surfaces of the first and second side walls and the bottom wall of the flow field in the form of water films, so that the water content of the fuel cell is kept, and the phenomenon of drying of a proton exchange membrane of the fuel cell is prevented;
5) when the water demand of the fuel cell is less than the water production, the trapped water accumulates on the vertical and horizontal hydrophilic patterns, which are asymmetric with respect to the gas flow transport direction causing uneven surface tension of the water itself, and the upper bottoms of the vertical and horizontal hydrophilic patterns are smaller than the lower bottoms, so that the laplace pressure of the liquid droplets at the front sides of the vertical and horizontal hydrophilic patterns is greater than the laplace pressure at the bottom sides, thereby causing a laplace pressure difference; under the action of self-uneven surface tension, Laplace pressure difference and surface low slip resistance of the water film, the product water starts to actively move directionally along the airflow transmission direction; the product water captured on the vertical and horizontal hydrophilic patterns in the flow field is actively and directionally moved to the air outlet and is dragged by the airflow shearing force in the same direction in the flow field, so that the speed of discharging the excessive product water from the flow field is further accelerated, the problem of water flooding of the fuel cell is greatly solved, the mass transfer efficiency of the fuel cell is enhanced, and the performance and the stability of the fuel cell are improved.
6. The water collecting and draining method according to claim 5, wherein in step 1) d), the surfaces of the first and second sidewalls and the bottom wall of each of the main flow passage, the upper flow-dividing flow passage and the lower flow-merging flow passage are subjected to hydrophobic treatment to form the low surface energy film by using laser etching and chemical agent soaking modification, comprising the steps of: firstly, carrying out laser etching to form a micro-scale and nano-scale concave-convex structure; and then carrying out chemical reagent soaking modification to form a low-surface-energy film on the concave-convex structure.
7. A water collecting and draining method according to claim 6, wherein the laser etching has the working parameters of a scanning speed of 100mm/s-1000mm/s, a spot diameter of 10 μm-50 μm, a scanning pitch of 10 μm-50 μm and a processing power of 10w-30 w.
8. A method according to claim 6, wherein the chemical agent is soaked in 0.5-2 wt.% ethanol solution of fluorosilane or stearic acid.
9. The collective drainage method as set forth in claim 5, wherein in e) of the step 1), the low surface energy films of the first and second sidewalls and the bottom wall of each of the main flow channel, the upper diverging flow channel and the lower converging flow channel are partially laser-etched, the laser-etched portions of the low surface energy films are partially laser-etched so that a portion of the surface of the bipolar plate body is exposed, and micro-scale and nano-scale asperities are formed on the surface so that the etched regions have hydrophilic characteristics, comprising the steps of: respectively focusing laser spots on the surfaces of the low-surface-energy thin films of the first side wall, the second side wall and the bottom wall, then defining a laser etching range according to the set vertical hydrophilic pattern and the set horizontal hydrophilic pattern, and finally etching the defined range.
10. The water collection and drainage method according to claim 9, wherein the operating parameters of the laser etching are as follows: the scanning speed is 100mm/s-1000mm/s, the spot diameter is 10 μm-50 μm, the scanning interval is 10 μm-50 μm, and the processing power is 10w-30 w.
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| CN115995574A (en) * | 2023-01-10 | 2023-04-21 | 吉林大学 | Bionic bipolar plate with active drainage surface and implementation method thereof |
| CN115995574B (en) * | 2023-01-10 | 2024-04-12 | 吉林大学 | Bionic bipolar plate with active drainage surface and implementation method thereof |
| CN117650255A (en) * | 2024-01-29 | 2024-03-05 | 南昌大学 | Fuel cell with flow channel of local bidirectional converging and diverging structure |
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