A static drain fuel cell plate flow field

Abstract

The application relates to a static drainage fuel cell polar plate flow field, which is formed by arranging a plurality of bionic microstructures (2) to form an island array; each bionic microstructure (2) comprises a top plane, a slope and a bottom plane, one side of the top plane is provided with an opening plane perpendicular to the bottom plane, and the slope connects the remaining sides of the top plane and the bottom plane; the slope has gradient hydrophilicity, liquid water is driven to move along the slope to the opening plane by using non-equilibrium surface tension to form a liquid water transmission path (5); and a polar plate plane area between adjacent bionic microstructures (2) has hydrophobicity to form a gas transmission path (6). Compared with the prior art, the application can prevent liquid water from accumulating, realize rapid drainage to a porous layer, avoid interference with a gas path at the same time, improve static drainage efficiency, and is suitable for long-time operation of a static drainage mode fuel cell.

Description

Technical Field

[0001] This invention belongs to the field of proton exchange membrane fuel cell technology and relates to a fuel cell electrode flow field that includes static drainage function. Background Technology

[0002] With hydrogen energy gaining widespread attention as a clean energy source, fuel cells, as a power generation device that directly converts the chemical energy of hydrogen and oxygen into electrical energy, have advantages such as high efficiency, high specific volumetric power density, high quality energy density, and rapid start-up. They have broad application prospects in fields such as automotive power, underwater vehicles, and aerospace.

[0003] The electrode plates are one of the core components of a proton exchange membrane fuel cell (PEMFC). Their flow field structure primarily guides water vapor transport, conducts electricity, and provides support. Depending on the application scenario, the required drainage method for the fuel cell varies, thus determining the structural design direction of the stack. Drainage methods are mainly divided into two categories: dynamic drainage and static drainage. Static drainage refers to a method that does not rely on external gas thrust to expel liquid water, but rather relies on the electrode plate's own structure to guide the liquid water out directionally and rapidly. It has advantages such as simple structure and no additional gas consumption, making it suitable for enclosed or special scenarios such as underwater vehicles and aerospace.

[0004] In static drainage structures, the electrode plates differ from conventional ridge structures, requiring a through-groove planar design to guide liquid water in the membrane electrode to flow towards the porous plate, pass through the porous plate into the cooling water chamber, and then be discharged. Simultaneously, it is necessary to guide the reactant gas to the liquid surface inside the micropores of the porous plate to achieve dynamic gas-liquid pressure balance and complete gas sealing. However, under long-term operating conditions, the interface between the carbon paper and the electrode plates is prone to liquid water accumulation due to insufficient drainage, hindering gas from entering the catalyst layer and causing a sharp decline in battery performance. The root cause lies in the unreasonable design of the electrode plate flow field structure, resulting in reduced water-gas transport efficiency.

[0005] To address the above issues, some research has already been conducted in the existing technology: Chinese patent CN109509897A discloses a water flow field for a bipolar plate in a statically draining fuel cell. The water flow field is placed within the bipolar plate's water cavity to increase the actual water-conducting area of ​​the plate and improve the fuel cell's operational stability. However, this solution still carries the risk of liquid water accumulating at the flow field interface and insufficient drainage efficiency.

[0006] Chinese patent CN106654316A discloses a cathode flow channel suitable for static drainage in aerospace applications. Static drainage is achieved by installing a static drainage valve within the cathode flow channel, which can improve membrane flooding. However, this solution introduces an additional circuit control system, increasing system complexity and negatively impacting equipment reliability.

[0007] Chinese patent CN109524684A discloses a fuel cell bipolar plate with biomimetic self-draining function and a self-draining method, which improves water management by setting microstructures on the surface of the plate. However, the discharge of liquid water in this solution still depends on the thrust generated by the external gas flow rate, which falls under the category of dynamic drainage. The microstructure of the plate itself does not have the ability to actively drive water, and the gas and liquid water share the same flow channel space, resulting in mass transfer interference.

[0008] Chinese patent CN110492127A discloses a gradient-varying directional water delivery and diversion method for fuel cells, which promotes liquid water diffusion and transport by introducing a hydrophilic design. However, its hydrophilic treatment is a uniform or regional static coating, relying on capillary action or gas assistance for passive drainage. Coupling interference still exists between the liquid water transport path and the mass transfer path of the reactant gas, making it impossible to effectively achieve gas-liquid separation.

[0009] In summary, existing technologies struggle to simultaneously meet the following requirements: achieving effective separation of liquid water and reactant gas transport paths without relying on external driving forces, ensuring rapid and directional discharge of liquid water into the porous layer, and avoiding interference with the gas mass transfer path. Therefore, it is necessary to further optimize the flow field structure of fuel cell electrode plates with static drainage capabilities to improve static drainage efficiency and meet the stable operation requirements under high current density conditions. Summary of the Invention

[0010] The purpose of this invention is to overcome the defects of the prior art and provide a static drainage flow field for fuel cell plates to improve static drainage efficiency and make it suitable for high current density operation of fuel cells.

[0011] To achieve the above objectives, the present invention is implemented through the following technical solution: a flow field plate with static drainage function, wherein the flow field is formed by an island array of multiple biomimetic microstructures; Each biomimetic microstructure includes a top plane, a slope, and a bottom surface. One side of the top plane has an opening plane perpendicular to the bottom surface, and the slope connects the other sides of the top plane to the bottom surface. The slope has a gradient hydrophilicity, and the non-equilibrium surface tension drives liquid water to move directionally along the slope to the opening plane, forming a liquid water transport channel. The planar regions of the electrodes between adjacent biomimetic microstructures are hydrophobic, forming gas transport pathways.

[0012] Furthermore, the hydrophilicity of the slope gradually decreases along the direction from the bottom surface to the top plane; The liquid water transport path and the gas transport path are separate and do not interfere with each other.

[0013] Furthermore, in the island array, the opening plane of each biomimetic microstructure faces the slope of the next adjacent biomimetic microstructure, so that liquid water forms a continuous directional transport path along the array direction; Each column of biomimetic microstructures is parallel to each other and is arranged at equal intervals within the column; the biomimetic microstructures in adjacent columns are arranged in parallel or staggered arrangements, forming parallel island arrays or staggered island arrays respectively; the spacing between adjacent biomimetic microstructures is 0.5 to 1.5 times the feature dimension of the bottom surface of the biomimetic microstructure.

[0014] Furthermore, by adjusting the cell size parameters of the biomimetic microstructure and the arrangement direction of the island array, the direction of liquid water transport can be controlled and adjusted.

[0015] Furthermore, the top plane can be one of the following: a closed surface, a round hole, a square hole, or a diamond-shaped hole.

[0016] Furthermore, the shape of the biomimetic microstructure is either biomimetic fish scale or trumpet-shaped; the slope between the slope and the bottom surface is 30° to 90°; the area of ​​the opening plane accounts for 30% to 100% of the total side area of ​​the biomimetic microstructure; and the shape of the top plane is either circular, elliptical, or rectangular.

[0017] Furthermore, the distribution direction of the hydrophilic regions on the slope is parallel or perpendicular to the opening plane; the gradient hydrophilicity of the slope is set according to contact angle partitioning, and the partitioning method is one of the following: The two sections have contact angle ranges of less than 45° and 45° to 90°, respectively. The three zones have contact angle ranges of less than 30°, 30° to 60°, and 60° to 90°, respectively. Or, multiple extensions of the above partitioning method.

[0018] Furthermore, the gradient hydrophilicity of the slope is achieved through one of the following methods: Laser engraving technology is used to form gradient micro-nano structures on the slope surface in order to regulate the hydrophilic gradient distribution of the slope surface; Alternatively, at least one of ultrasonic spraying or magnetron sputtering can be used to coat the slope surface with a hydrophilic material along the gradient direction. The hydrophilic material is one or more of silicon-based materials, titanium nitride, and hydrophilic polymethyl methacrylate.

[0019] Furthermore, the hydrophobicity of the plate planar region between adjacent biomimetic microstructures is achieved using one of the following methods: Gradient hydrophobic scheme: The contact angle of the hydrophobic region gradually decreases along the direction from the bottom surface to the top plane, and is divided into sections according to the contact angle. The sectioning method is two-segment: contact angle intervals of 90°~135° and 135°~180° respectively; or three-segment: contact angle intervals of 90°~120°, 120°~150° and 150°~180° respectively; or multiple segments. Constant hydrophobic scheme: The contact angle of the hydrophobic region is uniformly distributed between 120° and 150°.

[0020] Furthermore, the hydrophobicity of the hydrophobic region is achieved through one of the following methods: Laser engraving technology is used to form gradient micro / nano structures in the hydrophobic region to control the hydrophobic gradient distribution; Alternatively, at least one of ultrasonic spraying or magnetron sputtering may be used to coat the hydrophobic region with a hydrophobic material, wherein the hydrophobic material is one or more of polytetrafluoroethylene (PTFE), titanium carbide (TiC), and polyethylene (PE).

[0021] This invention relates to a statically drained fuel cell electrode plate. The electrode plate comprises an island array composed of biomimetic "fish scale" microstructures. The surface around the slope is controlled by hydrophilicity and hydrophobicity to form pathways for gas and liquid respectively, without interference between them. A gradient hydrophilicity is formed between the slope and the bottom surface, and the non-equilibrium surface tension drives droplets to move directionally to the opening, forming a water pathway. The two sides of the slope with gradient hydrophilicity of microstructures are hydrophobic surfaces, forming a gas pathway. Through structural design, this invention achieves rapid drainage to the porous layer, preventing liquid water from accumulating at the interface between the electrode plate and the membrane electrode assembly (MEA), thus preventing gas from flowing into the MEA, improving the static drainage functionality, and increasing the reliability of the fuel cell operating under static drainage conditions for extended periods.

[0022] The aforementioned fuel cell plate features can be applied to proton exchange membrane electrolyzers and proton exchange membrane regenerable fuel cells.

[0023] Compared with the prior art, the present invention has the following advantages: (1) It realizes true active static drainage. This invention combines the three-dimensional slope geometry of a simulated fish-scale island array with a slope gradient hydrophilic design to establish a continuous non-equilibrium surface tension between the bottom and top of the slope, generating a net pressure difference that drives liquid water to spontaneously and directionally migrate along the slope to the opening for discharge without any external gas thrust. Compared to existing passive drainage methods that rely on gas flow thrust or capillary action, this invention achieves a fundamental breakthrough at the driving mechanism level, completely eliminating dependence on external driving forces and enabling stable drainage even in special working conditions without gas assistance, such as in a sealed or weightless environment.

[0024] (2) Physical separation is achieved through a dual-pathway system for water and gas, eliminating mass transfer coupling interference. The gradient hydrophilic, fish-scale-like slope and the hydrophobic electrode planes on both sides form spatially isolated liquid and gas transport pathways on the same electrode surface, without interference between them. This physical separation mechanism effectively blocks the path of liquid water diffusion and accumulation into the gas region, eliminating the fundamental defect of gas-liquid mass transfer path coupling interference in existing technologies, and ensuring smooth transport of reactant gases to the catalyst layer, especially under high current density and long-term operation conditions with significant advantages.

[0025] (3) The slope geometry and gradient hydrophilic height work together to form an indispensable complete driving system. The slope geometry, mimicking fish scale microstructures, determines the effective contact area of ​​the droplets and the direction of the driving force. The gradient hydrophilicity of the slope continuously creates an asymmetric surface energy difference on this geometric surface, generating a directional net driving force. These two elements form a highly synergistic driving system: without gradient hydrophilic distribution, the droplets lack directional driving force; without specific slope geometry, an effective directional transport path cannot be formed. This synergistic mechanism is the core foundation for the active static drainage achieved in this invention, and it also reflects the essential innovation of this invention compared to existing hydrophilic coating designs.

[0026] (4) The drainage direction is flexible and controllable, adapting to diverse engineering needs. By adjusting the cell size parameters of the biomimetic microstructure and the arrangement direction of the island array, the directional transport direction of liquid water can be flexibly changed, enabling active design of the drainage path. This feature allows the electrode structure to adapt to different installation directions and gravity orientations (including special working conditions such as weightlessness in aerospace and changes in direction), significantly improving the engineering flexibility and scenario adaptability of the electrode design.

[0027] (5) Effectively prevents liquid water accumulation and greatly improves long-term operational reliability. The synergistic effect of these mechanisms enables the rapid and continuous extraction of liquid water generated at the interface between the electrode plate and the membrane electrode assembly into the porous layer, fundamentally eliminating the risk of failure caused by liquid water accumulation hindering gas transport. The electrode plate structure of this invention requires no additional control components, is simple and reliable, and is particularly suitable for enclosed environments with extremely high requirements for equipment reliability and operational stability, such as underwater vehicles and aerospace applications, significantly extending the effective service life of statically drained fuel cells.

[0028] (6) The technical solution has good application extensibility. The water-gas separation and active drainage mechanism of the electrode flow field of this invention is also applicable to electrochemical devices such as proton exchange membrane electrolyzers and proton exchange membrane regenerative fuel cells. It provides a versatile and simple solution to the water management problem in such devices and has broad engineering application value. Attached Figure Description

[0029] Figure 1 This refers to the electrode flow field structure in Embodiment 1 of the present invention; Figure 2 The biomimetic "fish scale" microstructure in Embodiment 1 of the present invention; Figure 3 This is the static drainage water and air flow path in Embodiment 1 of the present invention; Figure 4 This is a schematic cross-sectional view of the overall static drainage structure in Embodiment 1 of the present invention; Figure 5 This is a schematic cross-sectional view of the overall static drainage structure in Embodiment 2 of the present invention; Explanation of markings in the diagram: 1-Flow field, 2-Bionic microstructure, 3-Slope, 4-Bottom, 5-Liquid water transport path, 6-Gas transport path, 7-Proton exchange membrane, 8-Gas diffusion layer, 9-Porous layer. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0031] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0032] Example 1 A static drainage fuel cell electrode flow field, such as Figure 1 As shown, the electrode material is titanium, and a surface processing technique is used to form a shape resembling... Figure 1 The flow field shown.

[0033] The flow field 1 is composed of multiple biomimetic microstructures 2, such as Figure 2 As shown, in this embodiment, the biomimetic microstructure is shaped like "fish scales". The top of the biomimetic microstructure 2 is a semi-circular plane with a diameter of 2 mm; one side has an opening plane perpendicular to the bottom surface, the opening area of ​​which accounts for 90% of the total side area of ​​the biomimetic microstructure, the height a of the opening plane is 30°, and the slope length b is 3 mm; the other sides are arc-shaped slopes, which are smoothly connected to the top semi-circular plane through arc-shaped chamfers; the height e of the biomimetic microstructure (from the bottom surface to the top plane) is 1.5 mm, and the wall thickness of the biomimetic microstructure is 0.5 mm; the spacing c between adjacent biomimetic microstructures is 1.5 mm (set according to 1 times the characteristic size of the bottom surface); the diameter d of the arc semi-circle at the bottom of the slope is 3.5 mm. The opening plane of each biomimetic microstructure in the array faces the slope of the next adjacent microstructure, forming a liquid water transport path 5 for continuous directional transport of liquid water along the array direction.

[0034] Laser engraving technology was used to process microstructures into micro-nano structures on a micro-slope surface. By adjusting laser parameters (power, scanning speed, and line spacing), the shape and spacing of the pyramid-shaped micro-nano structures were controlled, creating three gradient hydrophilic regions on the slope surface with gradually decreasing hydrophilicity from the bottom to the top plane: the first region (near the bottom) has a contact angle of less than 30°, the second region (middle of the slope) has a contact angle of 30°–60°, and the third region (near the top) has a contact angle of 60°–90°. Laser processing was performed under a vacuum anti-oxidation protective atmosphere to maintain the hydrophilic activity of the titanium surface oxide layer. The gradient hydrophilic slope surface creates a continuous non-equilibrium surface tension at both ends of the droplet, driving liquid water to spontaneously migrate directionally along the slope to the opening plane for discharge, forming a liquid water transport pathway.

[0035] The same laser engraving technology was used to fabricate hydrophobic micro / nano structures on the flat bottom surface area between adjacent microstructures. After processing, the contact angle of this area was approximately 140°, providing an independent pathway for gas transport, forming gas transport pathway 6, which is physically separated from liquid water transport pathway 5. Figure 3 As shown.

[0036] like Figure 4 As shown, after the electrode plate is assembled with the gas diffusion layer 8 (GDL) and the proton exchange membrane 7 (PEM), the top plane of the biomimetic microstructure 2 contacts the surface of the gas diffusion layer 8, serving as a support and current collector for conductivity. Liquid water generated by the membrane electrode is transported to the electrode plate surface via the gas diffusion layer 8, and then migrates directionally along the hydrophilic slope under the drive of non-equilibrium surface tension to the opening of the biomimetic microstructure 2. It is then discharged through the porous layer 9 to the cooling water chamber, achieving rapid drainage to the porous layer 9. This prevents liquid water from accumulating at the interface between the electrode plate and the membrane electrode (proton exchange membrane 7, gas diffusion layer 8), hindering gas flow into the membrane electrode, improving static drainage functionality, and increasing the reliability of the fuel cell operating under static drainage conditions for extended periods. The reactant gas is mass-transferred to the gas diffusion layer 8 through the gas transport pathway 6 formed by the hydrophobic surface regions between the biomimetic microstructures 2, and enters the catalyst layer to participate in the reaction. The gas and liquid pathways are physically isolated and do not interfere with each other throughout the entire process.

[0037] Example 2 The electrode substrate is made of 316L austenitic stainless steel with a thickness of 0.4mm; the biomimetic microstructure is shaped like a "trumpet," as... Figure 5As shown. The top of the microstructure is an elliptical plane with a major axis of 1.2 mm and a minor axis of 0.8 mm. The top and bottom surfaces are connected by a slope of 45°. The height e of the microstructure is 2.0 mm, and the wall thickness is 0.2 mm. The spacing c between adjacent microstructure columns is 1.5 mm (1.2 times the characteristic dimension of the bottom surface). Adjacent columns are staggered, with a staggered amount of 1 / 2 of the column spacing, forming a staggered island array. Each microstructure in the array has an opening at the center of its top surface with a diameter of 0.4 mm. There is an opening between two island arrays, which is a rectangle with a length of 0.6 mm and a width of 0.3 mm.

[0038] Using ultrasonic spraying technology, a hydrophilic polymethyl methacrylate (PMMA) solution is applied to the microstructured slope in two gradient spraying stages. The first spraying covers the entire slope, forming a hydrophilic layer with a contact angle of 45° to 90° (second stage). The second spraying is applied to the lower half of the slope near the bottom, adjusting the contact angle in this area to less than 45° (first stage), thus creating a two-stage gradient hydrophilic distribution.

[0039] Using ultrasonic spraying technology, polytetrafluoroethylene (PTFE) dispersion is sprayed onto the flat bottom area between adjacent microstructures, forming a gradient hydrophobic distribution: the hydrophobicity is stronger near the bottom side (contact angle about 150° to 160°) than near the top side (contact angle about 120° to 135°), so that the gas transport pathway's ability to repel liquid water is matched with the direction of liquid water transport, further reducing gas-liquid interference.

[0040] The staggered island array arrangement creates an interlaced distribution of gas-liquid pathways between adjacent columns, improving the uniformity of water-air transport across the effective cross section of the flow field; the trumpet-shaped microstructure has better contact than the fish-scale-shaped structure, reducing contact resistance and making it suitable for low drainage flux conditions.

Claims

1. A statically drained fuel cell electrode flow field, characterized in that, The flow field (1) is formed by an island array of multiple biomimetic microstructures (2); Each biomimetic microstructure (2) includes a top plane, a slope and a bottom surface, wherein one side of the top plane has an opening plane perpendicular to the bottom surface, and the slope connects the other sides of the top plane to the bottom surface; The slope has a gradient hydrophilicity, and the non-equilibrium surface tension drives the liquid water to move directionally along the slope to the opening plane, forming a liquid water transport channel (5). The plate planar region between adjacent biomimetic microstructures (2) is hydrophobic, forming a gas transport pathway (6).

2. The flow field of the fuel cell electrode plates with static drainage according to claim 1, characterized in that, The hydrophilicity of the slope gradually decreases from the bottom surface to the top plane. The liquid water transport path (5) and the gas transport path (6) are separate from each other and do not interfere with each other.

3. The flow field of the fuel cell electrode plates with static drainage according to claim 1, characterized in that, In the island array, the opening plane of each biomimetic microstructure (2) faces the slope of the next adjacent biomimetic microstructure, so that liquid water forms a continuous directional transport path along the array direction; Each column of biomimetic microstructures is parallel to each other and is arranged at equal intervals within the column; the biomimetic microstructures in adjacent columns are arranged in parallel or staggered arrangements, forming parallel island arrays or staggered island arrays respectively; the spacing between adjacent biomimetic microstructures is 0.5 to 1.5 times the feature dimension of the bottom surface of the biomimetic microstructure.

4. The flow field of the fuel cell electrode plates with static drainage according to claim 1, characterized in that, By adjusting the cell size parameters of the biomimetic microstructure and the arrangement direction of the island array, the direction of liquid water transport can be controlled and adjusted.

5. The flow field of the fuel cell electrode plates with static drainage according to claim 1, characterized in that, The top plane can be one of the following: a closed surface, a round hole, a square hole, or a diamond-shaped hole.

6. The static drainage fuel cell electrode flow field according to claim 1, characterized in that, The shape of the biomimetic microstructure (2) is either a biomimetic fish scale or a trumpet shape; the slope between the slope and the bottom surface is 30° to 90°; the area of ​​the opening plane accounts for 30% to 100% of the total area of ​​the side surface of the biomimetic microstructure; the shape of the top plane is either a circle, an ellipse or a rectangle.

7. The static drainage fuel cell electrode flow field according to claim 1, characterized in that, The distribution direction of the hydrophilic regions on the slope is parallel or perpendicular to the opening plane; the gradient hydrophilicity of the slope is set according to the contact angle, and the zoning method is one of the following: The two sections have contact angle ranges of less than 45° and 45° to 90°, respectively. The three zones have contact angle ranges of less than 30°, 30° to 60°, and 60° to 90°, respectively. Or, multiple extensions of the above partitioning method.

8. The static drainage fuel cell electrode flow field according to claim 7, characterized in that, The gradient hydrophilicity of the slope is achieved through one of the following methods: Laser engraving technology is used to form gradient micro-nano structures on the slope surface in order to regulate the hydrophilic gradient distribution of the slope surface; Alternatively, at least one of ultrasonic spraying or magnetron sputtering can be used to coat the slope surface with a hydrophilic material along the gradient direction. The hydrophilic material is one or more of silicon-based materials, titanium nitride, and hydrophilic polymethyl methacrylate.

9. The static drainage fuel cell electrode flow field according to claim 1, characterized in that, The hydrophobicity of the electrode planar region between adjacent biomimetic microstructures is achieved using one of the following methods: Gradient hydrophobic scheme: The contact angle of the hydrophobic region gradually decreases along the direction from the bottom surface to the top plane, and is divided into sections according to the contact angle. The sectioning method is two-segment: contact angle intervals of 90°~135° and 135°~180° respectively; or three-segment: contact angle intervals of 90°~120°, 120°~150° and 150°~180° respectively; or multiple segments. Constant hydrophobic scheme: The contact angle of the hydrophobic region is uniformly distributed between 120° and 150°.

10. The statically drained fuel cell electrode flow field according to claim 9, characterized in that, The hydrophobicity of the hydrophobic region is achieved through one of the following methods: Laser engraving technology is used to form gradient micro / nano structures in the hydrophobic region to control the hydrophobic gradient distribution; Alternatively, at least one of ultrasonic spraying or magnetron sputtering may be used to coat the hydrophobic region with a hydrophobic material, wherein the hydrophobic material is one or more of polytetrafluoroethylene (PTFE), titanium carbide (TiC), and polyethylene (PE).

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