Methanol fuel cell anode gas diffusion layer suitable for microgravity environment and preparation method thereof

Abstract

The invention relates to a methanol fuel cell anode gas diffusion layer suitable for a microgravity environment and a preparation method thereof, and the method comprises the following steps: 1, cutting a carbon fiber material into a required size, and carrying out high temperature carbonization to form a substrate layer; step 2, carrying out hydrophilic treatment on the substrate layer in the step 1, immersing the substrate layer in a polyacrylic acid solution, and carrying out thermocuring; 3, slurry is prepared, raw materials of the slurry comprise a conductive carbon material, a water repellent agent and a film-forming agent, the surface of the substrate layer is evenly coated with the slurry, and then sintering is conducted to form a micropore layer; 4, depositing a ZnO nanocone array on the surface of the microporous layer; step 5, filling the ZnO nanocone array with a mixture of a flexible conductive material and a fluorine-containing polymer; and step 6, carrying out heat treatment for 2h to 3h at the temperature of 400 DEG C to 500 DEG C under the protection of inert gas. According to the gas diffusion layer prepared by adopting the method, uniform distribution of methanol in the gas diffusion layer can be effectively improved, the conductivity of the gas diffusion layer is remarkably improved, the internal resistance of the fuel cell is reduced, and the performance of the methanol fuel cell under microgravity is favorably improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of anode of methanol fuel cell, in particular, relates to a gas diffusion layer (GDL) for anode of methanol fuel cell in microgravity environment (such as space station, satellite or deep space probe) and a preparation method thereof. BACKGROUND

[0002] Methanol fuel cell (DMFC) is an ideal candidate power source for international space station and deep space probe due to high energy density (6100 Wh / kg) of methanol fuel, safety of storage at room temperature and simplicity of system. Microgravity environment has a fundamental influence on gas-liquid two-phase flow mechanism of methanol fuel cell. In space mission, the disappearance of buoyancy leads to the inability of reaction gas (such as CO2) and liquid water to be naturally discharged by gravity, which is easy to accumulate in flow channel to form large bubbles and block mass transfer channels. Existing data shows that when the current density exceeds 80 mA / cm 2 , the performance of the cell in microgravity environment decreases by 20%-30% compared with that in normal gravity environment.

[0003] As the core component of membrane electrode, gas diffusion layer (GDL) bears multiple functions such as reactant transport, product discharge, electron conduction and mechanical support, and its design directly determines the efficiency and stability of the cell in microgravity working condition. However, the traditional GDL relies on gravity-driven fluid management mode, and the fluid behavior changes dramatically in space due to the lack of gravity, and the generated CO2 bubbles (anode) and water (cathode) cannot be naturally separated by gravity. The bubbles gather in the pores of GDL to form large bubbles, blocking the mass transfer channels, while the accumulated liquid water forms a water film, hindering the diffusion of oxygen, resulting in the performance degradation of methanol fuel cell, so it is urgent to develop a new GDL structure suitable for microgravity. SUMMARY

[0004] The present application solves the problems of CO2 bubble accumulation blocking flow channel of traditional gas diffusion layer in microgravity environment, and failure of traditional PTFE hydrophobic coating due to methanol infiltration, and provides a gas diffusion layer for anode of methanol fuel cell in microgravity environment and a preparation method thereof, so as to improve the mass transfer efficiency and overall performance of the fuel cell. The present application provides an efficient and stable solution for space energy system. The gas diffusion layer of the present application can effectively improve the uniform distribution of methanol in the gas diffusion layer, and inhibit the retention of methanol solution on the surface of microporous layer, avoid CO2 bubble accumulation blocking flow channel in microgravity, significantly improve the electrical conductivity of the gas diffusion layer, reduce the internal resistance of the fuel cell, and help to improve the performance of methanol fuel cell in microgravity.

[0005] To achieve the above technical problems, the present application adopts the following technical solutions: The present application aims to provide a preparation method of a gas diffusion layer for an anode of a methanol fuel cell suitable for a microgravity environment, comprising the following steps: Step 1, cutting a carbon fiber material to a desired size, high-temperature carbonization to form a base layer; Step 2, hydrophilic treatment of the base layer of Step 1, then immersion in a polyacrylic acid solution, heat curing; Step 3, preparation of a slurry, the slurry raw materials including conductive carbon material, hydrophobic agent and film-forming agent, uniform coating on the surface of the base layer, followed by sintering to form a microporous layer; Step 4, deposition of a ZnO nanocone array on the surface of the microporous layer; Step 5, filling of a flexible conductive material and a fluorine-containing polymer mixture in the ZnO nanocone array; Step 6, then placed under inert gas protection, heat treatment at a temperature of 400-500℃ for 2-3h; to enhance the stability and adhesion of the material.

[0006] Further limitation, in Step 1, high-temperature carbonization at 1000-2000℃.

[0007] Further limitation, in Step 2, the hydrophilic treatment is strong acid oxidation, plasma treatment, electrochemical oxidation, ozone oxidation or hydrophilic polymer grafting.

[0008] Further limitation, in Step 2, the mass concentration of the polyacrylic acid solution is 5%.

[0009] Further limitation, in Step 2, heat curing at 120℃ for 1h.

[0010] Further limitation, in Step 3, the mass ratio of the conductive carbon material, hydrophobic agent and film-forming agent is (70-90):(5-30):(0-5).

[0011] Further limitation, in Step 3, the hydrophobic agent includes one or any combination of several of polytetrafluoroethylene, polyolefin, silicone resin or fluorocarbon polymer.

[0012] Further limitation, in Step 3, the conductive carbon material includes one or any combination of several of carbon black, carbon nanotube, Ketjen black, graphene or graphite powder.

[0013] Further limitation, in Step 3, the film-forming agent includes one or any combination of several of polyvinylidene fluoride, polydimethylsiloxane or perfluorosulfonic acid resin.

[0014] Further limitation, in Step 3, the coating method is blade coating, ultrasonic spraying, pneumatic spraying or vapor deposition. Further limitation, in step 3, sintering at 250-300℃.

[0015] Further limitation, in step 3, the carbon microporous layer deposition thickness is 20μm, porosity is 60%-80%, and pore size is 0.1-1μm.

[0016] Further limitation, in step 4, the surface deposition of ZnO nano-array method includes any one of chemical vapor deposition, electrochemical deposition, 3D printing technology, etching, and laser processing, with a height of 1μm and a pitch of 100nm.

[0017] Further limitation, in step 5, the mass ratio of flexible conductive material to fluorine-containing polymer is (70-95):(5-30).

[0018] Further limitation, in step 5, the method of filling flexible conductive material includes any one of chemical vapor deposition or spraying, wherein the flexible conductive material is one or any combination of PEDOT:PSS, polypyrrole (PPy), carbon nanotube / polymer composite, PVA / PAA double network ionic gel, or graphene / elastomer composite.

[0019] Further limitation, in step 5, the fluorine-containing polymer is one or any combination of perfluoroalkyl acrylate copolymer, polyvinylidene fluoride, perfluoropolyether, fluorinated silane, or PTFE / silica nanoparticles.

[0020] Further limitation, in step 6, the inert gas is one or more of N2, He, or Ar.

[0021] The present application provides a gas diffusion layer for anode of a methanol fuel cell under microgravity prepared by any of the above methods, having the following characteristics: 1. Anode-side heterostructure: Primary layer: made of conductive hydrophilic carbon fiber material, providing mechanical support and electrical conductivity, and guiding the diffusion of liquid methanol.

[0022] Microporous layer (MPL): a layer of carbon is first coated on the surface of the primary layer, and then ZnO nano-cone arrays are deposited, forming a super-gasophobic surface (contact angle with CO2 gas bubbles >160°), which is beneficial for CO2 detachment.

[0023] 2. Flexible conductive material filling: flexible conductive polymer is filled between ZnO nano-cones to enhance electron conductivity and buffer stress, preventing structural collapse.

[0024] 3. Hydrophobic treatment of microporous layer: Surface hydrophobic modification of microporous layer by fluorinated polymer coating to make it highly hydrophobic (contact angle ≥ 150°) to prevent methanol solution from stagnating on the surface.

[0025] Compared with the prior art, the present application has the following beneficial effects: 1. Uniform methanol feeding: The prepared hydrophilic carbon fiber substrate can significantly improve the capillary penetration efficiency of methanol under microgravity. 2. Prevent liquid accumulation: The surface of the microporous layer is designed to be hydrophobically modified to have high hydrophobicity (contact angle ≥ 150°), effectively inhibiting the stagnation of methanol solution on the surface.

[0026] 3. Improve gas mass transfer efficiency: The super-gas-repellent surface state design effectively avoids CO2 bubble accumulation and blockage of the flow channel under microgravity.

[0027] 4. Enhanced conductivity: The incorporation of flexible conductive material improves the conductivity of the gas diffusion layer, significantly reduces the internal resistance of the fuel cell, and supports the nano-cone structure to prevent its collapse.

[0028] In order to further understand the features and technical contents of the present application, please refer to the following detailed description of the present application and the accompanying drawings, however, the accompanying drawings are provided for reference and illustration only, and are not used to limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 Schematic diagram of the cross-section structure of a conventional fuel cell; Figure 2 Schematic diagram of the cross-section structure of a fuel cell of the present application; Figure 3 Partial enlarged view of the anode gas diffusion layer and the catalytic layer of the present application; Figure 4 Schematic diagram of the anode gas diffusion layer structure of the present application; 1 - fuel cell, 2 - current collector plate, 3 - bipolar plate, 4 - gas diffusion layer base layer, 5 - catalytic layer, 6 - proton exchange membrane, 7 - gas diffusion layer microporous layer, 8 - gas / liquid flow channel, 9 - ZnO / C, 10 - CO2 flow direction, 11 - methanol flow direction, 12 - ZnO nano-cone, 13 - CO2 bubble. DETAILED DESCRIPTION

[0030] The present application will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made. These all belong to the protection scope of the present application.

[0031] Example 1: The preparation method of the gas diffusion layer for the anode of a methanol fuel cell suitable for use in a microgravity environment in this embodiment is carried out according to the following steps: Step 1: Cut the carbon fiber material into the required size 5cm 2 , high temperature carbonization at 2000℃ for 8h to form a base layer; Step 2: The substrate layer prepared in step 1 is subjected to a hydrophilic treatment (the substrate layer is placed in a plasma chamber, in a water vapor atmosphere, at a power of 200 W, for 10 minutes, and at a pressure of 100 Pa), and then immersed in a 5% polyacrylic acid solution, and thermally cured at 120° C. for 1 hour. Step 3. Weigh 1 g of Vulcan XC-72R and add it to a mixed solution of 20 mL of isopropanol and water (the volume ratio of isopropanol to water is 7:3). Stir magnetically at 500 rpm for 30 minutes, then ultrasonically break it at 300 W power until there is no agglomeration (taking 15 minutes), slowly add 0.33 g of hydrophobic agent PTFE emulsion (60%), continue magnetic stirring for 1 hour to obtain a slurry, and evenly coat it (scraper coating, speed 5 mm / s, scraper gap 30 μm) on the surface of the substrate layer. Place it on a 120°C hot plate to cure the PTFE and remove the solvent. Then sinter it at 300°C for 2.5 hours to form a microporous layer. The thickness of the microporous layer is about 20 μm, the porosity is about 80%, and the pore size is 0.2 μm. Step 4: Deposit on the surface of the microporous layer (using vapor deposition method: zinc nitrate ( ), citric acid (chelating agent), ethylene glycol (solvent) were mixed in a molar ratio of 1:1:5, stirred for 2h to a transparent sol (concentration 0.1 mol / L), the sol was spin-coated on the substrate (3000 rpm, 30 s), annealed at 300°C for 10 min in a muffle furnace (remove organic matter, form ZnO crystal grains), repeat 1 time, get a seed layer with a thickness of 10-20 nm, control the grain size by annealing temperature (about 80 nm), the distance between adjacent grains is about 100 nm, which provides uniform nucleation sites for subsequent nano-array. The precursor (ZnO mixed with graphite powder at a molar ratio of 1:1, ground in a mortar for 30 min) boat was placed upstream of the quartz tube (low temperature zone, 8-10 cm away from the center heating zone), GDL was placed in the quartz boat in the center heating zone (high temperature growth zone) of the tube furnace, the two ends of the quartz tube were connected with sealing flanges, Ar gas (flow rate 100 sccm) was introduced for 30 min to exclude air in the tube (to avoid Zn being oxidized to ZnO2 impurities). The temperature was raised at a rate of 10°C / min: the precursor zone (upstream) temperature was 850°C (to ensure that ZnO reacts with C to generate Zn vapor), the substrate zone (center) temperature was 950°C (Zn vapor reacts efficiently on the substrate surface). O2 gas (flow rate 20 sccm) was introduced, Ar gas was kept at 100 sccm, and the growth was carried out for 2h, then O2 was turned off and Ar gas (100 sccm) was kept, and the system was naturally cooled to room temperature (about 2h) to avoid cracking of the nano-array due to sudden cooling. After cooling, the Ar gas was turned off and the GDL was taken out, and a white ZnO nano-cone array (height 1μm, spacing 100nm) was obtained on the surface of the nano-array; Step 5, fill the flexible conductive material and fluorine-containing polymer mixture (PEDOT:PSS solution needs to add 1% DMSO and 5% ethylene glycol (volume ratio) to improve conductivity, stir for 2h and filter with 0.45μm filter membrane; polyvinylidene fluoride (PVDF) is dissolved in N,N-dimethylformamide to prepare a 10wt% solution, stir at 60°C for 4h, add 6mL PVDF solution dropwise to 14mL PEDOT:PSS solution, stir for 30min with a magnetic stirrer, and ultrasonic spray on the ZnO nano-cone array, and evaporate the solvent on an 80°C hot plate; Step 6, then heat treat at 500°C for 2h under nitrogen gas protection.

[0032] Example 2: In this embodiment, the preparation method of the gas diffusion layer for the anode of the methanol fuel cell suitable for microgravity environment is carried out according to the following steps: Step 1, cut the carbon fiber material to the required size of 5cm 2 , high temperature carbonization at 1500°C for 8h to form a base layer; Step 2: The substrate layer prepared in step 1 is subjected to a hydrophilic treatment (the substrate layer is placed in a plasma chamber, in a water vapor atmosphere, at a power of 200 W, for 10 minutes, and at a pressure of 100 Pa), and then immersed in a 5% polyacrylic acid solution, and thermally cured at 120° C. for 1 hour. Step 3, prepare a slurry (weigh 1g Vulcan XC-72R and add it to 20mL of a mixed solution of isopropanol and water (volume ratio 6:4), magnetically stir at 500rpm for 30 minutes, then ultrasonically break it (power 300W, 15 minutes) until there is no agglomeration, slowly add 0.33g PTFE emulsion (60%) to the solution, and continue magnetic stirring for 1 hour). The slurry raw materials include conductive carbon material Vulcan XC-72R, hydrophobic agent PTFE and film-forming agent isopropanol / water mixed solvent, and evenly coat (scraper coating, speed 5mm / s, scraper gap 30μm, place on a 120℃ hot plate to cure PTFE and remove solvent) on the surface of the substrate layer, and then sinter at 300℃ for 3h to form a microporous layer (thickness about 20μm, porosity about 80%, pore size 0.3μm); Step 4: Deposit on the surface of the microporous layer (using vapor deposition method: zinc nitrate ( A mixture of citric acid (chelating agent), citric acid (chelating agent), and ethylene glycol (solvent) in a molar ratio of 1:1:5 was stirred for 2 hours to form a transparent sol (concentration 0.1 mol / L). The sol was then spin-coated onto a substrate (3000 rpm, 30 seconds) and annealed in a muffle furnace at 300°C for 10 minutes (to remove organic matter and form ZnO grains). This process was repeated once to produce a seed layer with a thickness of 10-20 nm. The grain size (approximately 80 nm) was controlled by the annealing temperature, with a spacing of approximately 100 nm between adjacent grains, providing uniform nucleation sites for subsequent nanoarray formation. A precursor boat (ZnO and graphite powder mixed in a 1:1 molar ratio and ground in a mortar for 30 minutes) was placed upstream of a quartz tube (in the low-temperature zone, 8-10 cm from the central heating zone). The GDL was placed in the quartz boat and placed in the central heating zone (high-temperature growth zone) of the tube furnace. Seal flanges were connected at both ends of the quartz tube, and Ar gas (100 sccm) was passed through the tube for 30 minutes to expel air from the tube to prevent oxidation of the Zn to ZnO2 impurities. The temperature was raised at a rate of 10°C / min: the precursor zone (upstream) reached 850°C (to ensure ZnO reacts with carbon to form Zn vapor), and the substrate zone (center) reached 950°C (to ensure efficient Zn vapor reaction on the substrate surface). O₂ gas (20 sccm) was introduced, while Ar gas was maintained at 100 sccm. After 2 hours of growth, the O₂ gas was turned off, and Ar gas was maintained at 100 sccm. The nanostructured product was then naturally cooled to room temperature (approximately 2 hours) to avoid cracking of the nanostructured product due to sudden cooling. After cooling, the Ar gas was turned off, and the GDL was removed, resulting in a ZnO nanocone array (1 μm in height, 100 nm in pitch) with a white nanostructured surface. Step 5, fill the flexible conductive material and fluorine-containing polymer mixture (PEDOT:PSS solution needs to add 1% DMSO and 5% glycol (volume ratio) to improve conductivity, stir for 2h and filter with 0.45μm filter membrane; polyvinylidene fluoride (PVDF) is dissolved in N,N-dimethylformamide to prepare a 10wt% solution, stir for 4h at 60℃, take 9mL PVDF solution and add it dropwise into 21mL PEDOT:PSS solution, magnetically stir for 30min, ultrasonic treatment for 15min, and then spray it on the ZnO nanotaper array by ultrasonic spraying, and evaporate the solvent on the 80℃ hot plate); Step 6, then heat treatment at 500℃ for 3h under nitrogen gas protection.

[0033] Example 3: In this embodiment, the preparation method of the gas diffusion layer for the anode of the methanol fuel cell suitable for microgravity environment is as follows: Step 1, cut the carbon fiber material to the required size of 5cm 2 , high temperature carbonization at 1000℃ for 8h to form a base layer; Step 2, hydrophilic treatment of the base layer in step 1 (place the base layer in a plasma chamber in a water vapor atmosphere, power 200W, treatment for 10min, gas pressure 100Pa), then immerse it in a 5% polyacrylic acid solution, and heat cure at 120℃ for 1h; Step 3, prepare the slurry (weigh 1g Vulcan XC-72R and add it into 20mL mixed solution of isopropyl alcohol and water (volume ratio of isopropyl alcohol to water is 6:4), magnetically stir at 500rpm for 30min, then ultrasonic crushing (power 300W, 15min) until no agglomeration, slowly add 0.33g PTFE emulsion (60%) dropwise to the solution, continue to magnetically stir for 1h), the slurry raw materials include conductive carbon material Vulcan XC-72R, hydrophobic agent PTFE and film-forming agent isopropyl alcohol / water mixed solvent, uniformly coat (knife coating, speed 5mm / s, knife gap 30μm, place on a 120℃ hot plate to cure PTFE and remove the solvent) on the surface of the base layer, and then sinter at 300℃ for 3h to form a microporous layer (thickness about 20μm, porosity about 80%, pore size 0.3μm); Step 4, deposit on the surface of the microporous layer (use vapor deposition method: take zinc nitrate ), citric acid (chelating agent), ethylene glycol (solvent) were mixed in a molar ratio of 1:1:5, stirred for 2h to a transparent sol (concentration 0.1 mol / L), the sol was spin-coated on the substrate (3000 rpm, 30 s), annealed at 300°C for 10 min in a muffle furnace (remove organic matter, form ZnO crystal grains), repeat 1 time, get a seed layer with a thickness of 10-20 nm, control the grain size (about 80 nm) by annealing temperature, the distance between adjacent grains is about 100 nm, which provides uniform nucleation sites for subsequent nano-array. The precursor (ZnO mixed with graphite powder at a molar ratio of 1:1, ground in a mortar for 30 min) boat was placed upstream of the quartz tube (low temperature zone, 8-10 cm away from the center heating zone), GDL was placed in the quartz boat in the center heating zone (high temperature growth zone) of the tube furnace, the two ends of the quartz tube were connected with sealing flanges, Ar gas (flow rate 100 sccm) was introduced for 30 min to exclude air in the tube (to avoid Zn being oxidized to ZnO2 impurities). The temperature was raised at a rate of 10°C / min: the precursor zone (upstream) temperature was 850°C (to ensure that ZnO reacts with C to generate Zn vapor), the substrate zone (center) temperature was 950°C (Zn vapor reacts efficiently on the substrate surface). O2 gas (flow rate 20 sccm) was introduced, Ar gas was kept at 100 sccm, and the growth was carried out for 2h, then O2 was turned off and Ar gas (100 sccm) was kept, and the system was naturally cooled to room temperature (about 2h) to avoid cracking of the nano-array due to sudden cooling. After cooling, the Ar gas was turned off and the GDL was taken out, and a white ZnO nano-cone array (height 1μm, spacing 100nm) was obtained on the surface of the nano-array; Step 5, fill the flexible conductive material and fluorine-containing polymer mixture (PEDOT:PSS solution needs to add 1% DMSO and 5% ethylene glycol (volume ratio) to improve conductivity, stir for 2h and filter with 0.45μm filter membrane; polyvinylidene fluoride (PVDF) is dissolved in N,N-dimethylformamide to prepare a 10wt% solution, stir at 60°C for 4h, add 4mL PVDF solution dropwise to 16mL PEDOT:PSS solution, magnetically stir for 30min, and ultrasonic spray on the ZnO nano-cone array, and evaporate the solvent on the 80°C hot plate); Step 6, then heat treatment at 400°C for 3h under nitrogen gas protection.

[0034] Example 4: In this embodiment, the preparation method of the gas diffusion layer for the anode of the methanol fuel cell suitable for microgravity environment is carried out according to the following steps: Step 1, cut the carbon fiber material into the required size of 5cm 2 , carbonize at 2000°C for 8h to form a base layer; Step 2: The substrate layer prepared in step 1 is subjected to a hydrophilic treatment (the substrate layer is placed in a plasma chamber, in a water vapor atmosphere, at a power of 200 W, for 10 minutes, and at a pressure of 100 Pa), and then immersed in a 5% polyacrylic acid solution, and thermally cured at 120° C. for 1 hour. Step 3, prepare a slurry (weigh 1g of Vulcan XC-72R and add it to a mixed solution of 20mL of isopropanol and water (the volume ratio of isopropanol to water is 6:4), magnetically stir at 500rpm for 30 minutes, then ultrasonically break it (power 300W, 15 minutes) until there is no agglomeration, slowly add 0.33g of PTFE emulsion (60%) to the solution, and continue magnetic stirring for 1 hour). The slurry raw materials include conductive carbon material Vulcan XC-72R, hydrophobic agent PTFE and film-forming agent isopropanol / water mixed solvent, and evenly coat (scraper coating, speed 5mm / s, scraper gap 30μm, place on a 120℃ hot plate to cure PTFE and remove solvent) on the surface of the substrate layer, and then sinter at 300℃ for 3 hours to form a microporous layer (thickness of about 20μm, porosity of about 80%, pore size 0.3μm); Step 4: Deposit on the surface of the microporous layer (using vapor deposition method: zinc nitrate ( A mixture of citric acid (chelating agent), citric acid (chelating agent), and ethylene glycol (solvent) in a molar ratio of 1:1:5 was stirred for 2 hours to form a transparent sol (concentration 0.1 mol / L). The sol was then spin-coated onto a substrate (3000 rpm, 30 seconds) and annealed in a muffle furnace at 300°C for 10 minutes (to remove organic matter and form ZnO grains). This process was repeated once to produce a seed layer with a thickness of 10-20 nm. The grain size (approximately 80 nm) was controlled by the annealing temperature, with a spacing of approximately 100 nm between adjacent grains, providing uniform nucleation sites for subsequent nanoarray formation. A precursor boat (ZnO and graphite powder mixed in a 1:1 molar ratio and ground in a mortar for 30 minutes) was placed upstream of a quartz tube (in the low-temperature zone, 8-10 cm from the central heating zone). The GDL was placed in the quartz boat and placed in the central heating zone (high-temperature growth zone) of the tube furnace. Seal flanges were connected at both ends of the quartz tube, and Ar gas (100 sccm) was passed through the tube for 30 minutes to expel air from the tube to prevent oxidation of the Zn to ZnO2 impurities. The temperature was raised at a rate of 10°C / min: the precursor zone (upstream) reached 850°C (to ensure ZnO reacts with carbon to form Zn vapor), and the substrate zone (center) reached 950°C (to ensure efficient Zn vapor reaction on the substrate surface). O₂ gas (20 sccm) was introduced, while Ar gas was maintained at 100 sccm. After 2 hours of growth, the O₂ gas was turned off, and Ar gas was maintained at 100 sccm. The nanostructured product was then naturally cooled to room temperature (approximately 2 hours) to avoid cracking of the nanostructured product due to sudden cooling. After cooling, the Ar gas was turned off, and the GDL was removed, resulting in a ZnO nanocone array (1 μm in height, 100 nm in pitch) with a white nanostructured surface. Step 5: Fill the ZnO nanocone array with a mixture of a flexible conductive material and a fluoropolymer (PEDOT:PSS solution needs to be added with 1% DMSO and 5% ethylene glycol (volume ratio) to improve conductivity, stirred for 2 hours, and filtered through a 0.45 μm filter membrane; polyvinylidene fluoride (PVDF) is dissolved in N,N-dimethylformamide to prepare a 10 wt% solution, stirred at 60°C for 4 hours, 2 mL of PVDF solution is added dropwise to 18 mL of PEDOT:PSS solution, magnetically stirred for 30 minutes, ultrasonically treated for 15 minutes, and then ultrasonically sprayed onto the ZnO nanocone array and placed on an 80°C hot plate to evaporate the solvent); Step 6: Then place it under nitrogen gas protection and heat treat it at 500° C. for 3 hours.

[0035] like Figure 1 The figure shows a cross-sectional structure diagram of a traditional methanol fuel cell. The fuel cell comprises a current collecting plate, a bipolar plate, a gas diffusion layer, a catalyst layer, and a proton exchange membrane. The gas diffusion layer comprises a base layer and a microporous layer. The base layer is usually treated to be hydrophobic to facilitate the formation of a gas transmission channel. The microporous layer is conventionally treated on the surface of the substrate to form a conductive and gas-transfer-friendly leveling layer, thereby reducing the contact resistance between the diffusion layer and the catalyst layer and improving the distribution of gas and water. However, conventional gas diffusion layers rely on a gravity-driven fluid management mode, and methanol is not easily immersed in them, causing "starvation" of the anode and a "vacuum effect," which accelerates battery aging. Therefore, the traditional methanol fuel cell is not suitable for microgravity environments.

[0036] like Figure 2 The figure shows a cross-sectional view of the methanol fuel cell structure of the present invention. The fuel cell comprises a current collector plate, a bipolar plate, a gas diffusion layer, a catalyst layer, and a proton exchange membrane. The gas diffusion layer comprises a base layer and a microporous layer. The base layer is hydrophilic to promote uniform distribution of liquid methanol. The microporous layer comprises a conventional carbon layer and a ZnO nanocone || flexible conductive material layer. The conventional carbon layer is a conductive, gas-transfer-facilitating flattening layer prepared by hydrophobizing the substrate surface. This reduces the contact resistance between the diffusion layer and the catalyst layer and improves gas-water distribution. The ZnO nanocone || flexible conductive material layer comprises a ZnO nanocone surface coated with a flexible conductive material and hydrophobically treated to create a super-aerophobic surface state, effectively preventing CO2 bubble accumulation and blockage in microgravity. Furthermore, the flexible conductive material filling significantly reduces contact resistance. The structural design of the anode gas diffusion layer of the present invention facilitates uniform methanol distribution, prevents CO2 bubble accumulation and blockage, and is suitable for use in microgravity environments.

[0037] like Figure 3As shown, the application provides a partial sectional enlarged view of a gas diffusion layer and a catalytic layer for a methanol fuel cell in a microgravity environment. The transmission path of the methanol fuel is uniformly distributed into the microporous layer through the hydrophilic substrate layer, the microporous layer has hydrophobicity which can effectively prevent the methanol solution from stagnating on its surface, flows into the ZnO nanotaper || flexible conductive material, and finally enters the catalytic layer through the capillary driving force of the nanopore to react: CH3OH + H2O → CO2 + 6H + +6e - . The CO2 gas is generated on the surface of the catalyst, forms micro-bubbles, reaches the ZnO nanotaper || flexible conductive material layer, and due to the design of the super-gas-repellent surface, promotes the bubbles to separate from the catalytic layer, and effectively prevents CO2 bubbles from accumulating and blocking the flow channel, enters the hydrophobic microporous layer, and drives the bubbles to flow in the flow field.

[0038] The application provides a gas diffusion layer structure for an anode of a methanol fuel cell in a microgravity environment and a preparation method thereof, which is designed through a hydrophilic-hydrophobic gradient structure and a super-gas-repellent surface state, is beneficial to uniform methanol feeding, prevents liquid accumulation, improves gas mass transfer efficiency, and effectively improves the mass transfer efficiency and overall performance of the fuel cell.

[0039] The application optimizes the structure and preparation method of the anode gas diffusion layer, solves the problem of performance degradation of the methanol fuel cell in a microgravity environment, and provides an efficient and stable solution for a space energy system.

[0040] Although the content of the application has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the application. After reading the above content, various modifications and alternatives of the application will be obvious to those skilled in the art. Therefore, the protection scope of the application should be defined by the appended claims.

Claims

1. A method for preparing a gas diffusion layer for a methanol fuel cell anode suitable for a microgravity environment, characterized in that: The following steps are involved: Step 1: Cut the carbon fiber material into the required size and carbonize it at high temperature to form a base layer; Step 2: hydrophilizing the base layer prepared in step 1, immersing the base layer in a polyacrylic acid solution, and thermally curing the base layer; Step 3: preparing a slurry, wherein the slurry raw materials include a conductive carbon material, a hydrophobic agent, and a film-forming agent, and uniformly coating the surface of the base layer, and then sintering to form a microporous layer; Step 4: depositing a ZnO nanocone array on the surface of the microporous layer; Step 5, filling the ZnO nanocone array with a mixture of a flexible conductive material and a fluorine-containing polymer; Step 6: Then place it under inert gas protection and heat treat it at 400°C~500°C for 2h-3h.

2. The method according to claim 1, characterized in that Carbonize at high temperature of 1000~2000℃.

3. The method according to claim 1, characterized in that The hydrophilic treatment is strong acid oxidation, plasma treatment, electrochemical oxidation, ozone oxidation or hydrophilic polymer grafting; the mass concentration of the polyacrylic acid solution is 5%; and thermal curing is performed at 120° C. for 1 hour.

4. The method according to claim 1, characterized in that The mass ratio of the electro-carbon material, the hydrophobic agent and the film-forming agent is (70-90): (5-30): (0-5); the hydrophobic agent includes one or more of polytetrafluoroethylene, polyolefin, silicone resin or fluorocarbon polymer; the electro-conductive carbon material includes one or more of carbon black, carbon nanotubes, Ketjen black, graphene or graphite powder; and the film-forming agent includes one or more of polyvinylidene fluoride, polydimethylsiloxane or perfluorosulfonic acid resin.

5. The method according to claim 1, characterized in that: The coating method includes scraping, ultrasonic spraying, pneumatic spraying and vapor deposition; and sintering at 250-300°C.

6. The method according to claim 1, characterized in that The carbon microporous layer has a deposition thickness of 20 μm, a porosity of 60%-80%, and a pore size of 0.1 μm-1 μm.

7. The method according to claim 1, characterized in that: The surface deposition method of ZnO nanoarray includes any one of chemical vapor deposition, electrochemical deposition, 3D printing technology, etching, and laser processing, with a height of 1 μm and a spacing of 100 nm.

8. The method according to claim 1, characterized in that: The mass ratio of the flexible conductive material to the fluoropolymer is (70-95):(5-30); the method for filling the flexible conductive material includes any one of a chemical vapor deposition method or a spraying method, wherein the flexible conductive material is one or more of PEDOT:PSS, polypyrrole (PPy), a carbon nanotube / polymer composite material, a PVA / PAA double network ion gel, or a graphene / elastomer composite material; the fluoropolymer is one or more of a perfluoroalkyl acrylate copolymer, polyvinylidene fluoride, perfluoropolyether, a fluorinated silane, or PTFE / silica nanoparticles.

9. The method according to claim 1, characterized in that: The inert gas is one or more of N2, He, or Ar gas.

10. A gas diffusion layer for anode of a methanol fuel cell under microgravity prepared by the method according to any one of claims 1 to 9.

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