A fuel cell gas diffusion layer and its preparation method and application

Abstract

The present invention relates to a fuel cell gas diffusion layer and its preparation method and application. The method comprises the following steps: dissolving carbon materials including carbon black, carbon nanotubes, graphene oxide, a hydrophobic agent and a binder in an organic solvent and water according to a predetermined ratio, and ultrasonically dispersing the mixture to form a uniform mixed slurry; depositing a predetermined amount of slurry on one side of a support base layer that has been hydrophobically treated by a low-temperature spraying technique to obtain a support base layer containing the slurry in a frozen state, and freeze-drying the layer; and finally, undergoing an annealing process to obtain a novel gas diffusion layer with controllable radially arranged pore channels. The method is simple in process, has common raw materials, good repeatability, and is suitable for mass production. The composition and structure of the microporous layer of the prepared gas diffusion layer at the micro and nano scales are precisely controllable, and the pore size, porosity and layer thickness can be arbitrarily designed to meet the functional requirements of gas-liquid transmission in the gas diffusion layer, alleviate the problem of water flooding during fuel cell operation, and achieve the effect of optimizing fuel cell performance and stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and in particular relates to a fuel cell gas diffusion layer and a preparation method and application thereof. Background Art

[0002] Fuel cells are a new type of power generation device that converts the chemical energy of fuel directly into electrical energy through electrochemical means. They boast high energy conversion efficiency, are environmentally friendly, and have a wide range of fuel applications, making them considered one of the most promising new automotive energy sources. The membrane electrode (MEA) in a proton exchange membrane fuel cell is a crucial core component, consisting of a proton exchange membrane, a catalyst layer, and a gas diffusion layer (GDL), from the center to the sides. The GDL plays multiple roles, significantly impacting fuel cell electrode performance, including withstanding the compressive stress of the bipolar plates, connecting to the catalyst layer, providing a uniform gas diffusion channel, enabling the timely removal of water vapor, and rapidly conducting electrons.

[0003] A gas diffusion layer typically consists of a base layer and a microporous layer. The base layer provides support and current collection, while the microporous layer ensures gas transport to the catalyst layer, reduces contact resistance between the gas diffusion layer and the catalyst layer, and maintains good water management. Currently, the development of fuel cells requires adaptability to more complex operating environments, placing increasingly stringent demands on the preparation process for the microporous layer.

[0004] Chinese patent CN112724724A discloses a method for preparing a gas diffusion layer (GMDL) and its microporous layer in a fuel cell membrane electrode. Using UV curing technology, an organosiloxane, a reactive monomer, a photoinitiator, a coupling agent, and a carbon material are uniformly mixed and cured to form the GMDL microporous layer. However, this preparation process involves complex materials, demanding reaction conditions, and high process costs.

[0005] Chinese patent CN110492124A discloses a highly conductive hydrophobic gas diffusion layer and its preparation method. The gas diffusion layer is composed of a porous conductive substrate treated with hydrophobic modified graphene and a microporous layer constructed of modified graphene / carbon material. The microporous layer is evenly coated on one side of the porous conductive substrate layer to obtain a highly conductive hydrophobic gas diffusion layer. However, the gas-liquid transmission pores of the gas diffusion layer obtained by the single process of mixed slurry coating are tortuous, and the connection depth is insufficient, which will cause local flooding and affect the service life of the fuel cell. Therefore, it is very necessary to accurately control the radial pore arrangement and distribution in the microporous layer of the gas diffusion layer in the preparation process to form regular and independent gas-liquid transmission channels. Summary of the Invention

[0006] The purpose of the present invention is to address the problems of complex process methods and lack of precise control methods for microscopic pores in the design of fuel cell gas diffusion layers in the prior art, and to propose a fuel cell gas diffusion layer and its preparation method and application. The gas diffusion layer, while maintaining good hydrophobicity and stability, enhances the gas-liquid transmission function and effectively alleviates the flooding phenomenon, which is beneficial to improving the power and stability of proton exchange membrane fuel cells, reducing manufacturing costs and extending service life.

[0007] The present invention adopts a simple low-temperature atomization spray-freeze sublimation method to prepare the fuel cell gas diffusion layer, which is a simple, effective and precise preparation technology for regulating the microscopic pores of the gas diffusion layer.

[0008] The purpose of the present invention is achieved by at least one of the following technical solutions.

[0009] The present invention provides a method for preparing a fuel cell gas diffusion layer, wherein the gas diffusion layer is constructed by a low-temperature atomization-freeze sublimation method, specifically comprising the following steps:

[0010] (1) impregnating the carbon fiber substrate in a hydrophobic agent for hydrophobic pretreatment;

[0011] (2) adding the carbon material and the hydrophobic agent emulsion into an organic solvent and deionized water, and ultrasonically dispersing the mixture to obtain a uniform carbon material slurry;

[0012] (3) using a spray gun to evenly spray the carbon material slurry described in step (2) on one side of the surface of the hydrophobic pretreated support base in step 1 under low temperature conditions to obtain a support base containing the slurry in a frozen state;

[0013] (4) freeze-drying the support base containing the slurry in the frozen state described in step (3) to obtain a support base with a microporous layer;

[0014] (5) Annealing, sintering and reducing the support base layer with the microporous layer described in step (4) to obtain a gas diffusion layer.

[0015] Furthermore, in step (1), the carbon fiber substrate includes any one of carbon paper, carbon cloth, and carbon felt.

[0016] Preferably, in step (1), the carbon fiber substrate is carbon paper.

[0017] Furthermore, in step (1), the hydrophobic pretreatment includes: immersing the carbon fiber substrate in a hydrophobic agent emulsion, the immersion time is 5-15 minutes, the hydrophobic agent emulsion concentration is 1-11wt%, and then transferring it to an oven for drying at a drying temperature of 60-100°C, and finally annealing and sintering multiple times in a muffle furnace, the first sintering temperature is 200-300°C, the sintering time is 10-60 minutes, the heating rate is 1-10°C / min, the last sintering temperature is 300-400°C, the sintering time is 10-60 minutes, and the heating rate is 1-10°C / min.

[0018] Preferably, in step (1), in the pretreatment, the immersion time is 5 minutes, the hydrophobic agent emulsion concentration is 5.5 wt%, and then it is transferred to an oven for drying at a drying temperature of 80°C, and finally annealed and sintered multiple times in a muffle furnace, with the first sintering temperature being 250°C, the sintering time being 30 minutes, the heating rate being 5°C / min, and the last sintering temperature being 350°C, the sintering time being 30 minutes, and the heating rate being 5°C / min.

[0019] Furthermore, in step (2), the carbon material includes one or more of carbon black, carbon nanotubes, and graphene oxide; and the hydrophobic agent emulsion includes one of polytetrafluoroethylene emulsion, polyvinylidene fluoride emulsion, and tetrafluoroethylene emulsion.

[0020] Preferably, in step (2), the carbon material is carbon black, carbon nanotubes, and graphene oxide; and the hydrophobic agent emulsion in step (2) is polytetrafluoroethylene emulsion.

[0021] Furthermore, in step (2), the organic solvent includes one of ethanol, isopropanol, and n-propanol; the ratio of the organic solvent to deionized water in step 2 is 1:0.1-10; the ultrasonic dispersion time in step 2 is 1-4h, and the ultrasonic dispersion frequency is 20-40kHz.

[0022] Preferably, in step (2), the organic solvent is ethanol; the ratio of the organic solvent to deionized water in step 2 is 1:1; the ultrasonic dispersion time in step 2 is 3 hours, and the ultrasonic dispersion frequency is 20 kHz.

[0023] Furthermore, the concentration of the carbon material slurry in step (3) is 3.5-5.5 mg / ml; the low temperature condition in step 3 is -150 to -10°C; the spraying rate in step 3 is 50-100 μl / min; the carbon material loading in the support base containing the slurry in step 3 is 0.5-3.0 mg / cm 2 .

[0024] Preferably, in step (3), the carbon material slurry concentration is 5.2 mg / ml; the low temperature condition temperature in step 3 is -147°C; the spraying rate in step 3 is 75 μl / min; the carbon material loading in the slurry-containing support base in step 3 is 1.0 mg / cm 2 .

[0025] Furthermore, in step (4), the freeze-drying temperature is -198 to 0°C, and the drying time is 24 to 48 hours.

[0026] Preferably, in step (4), the freeze-drying temperature is -80°C and the drying time is 48 hours.

[0027] Furthermore, in step (5), the annealing sintering temperature is 300-400°C, the sintering time is 10-60min, and the heating rate is 1-10°C / min.

[0028] Preferably, in step (5), the annealing sintering temperature is 250°C, the sintering time is 30 minutes, and the heating rate is 5°C / min.

[0029] Furthermore, in step (5), the reduction temperature is 200-300°C, the sintering time is 60-120min, the heating rate is 1-10°C / min, and the reducing atmosphere is one of Ar / H2, N2 / H2, CH4 / H2, and H2.

[0030] Preferably, in step (5), the reduction temperature is 200°C, the sintering time is 90 min, the heating rate is 5°C / min, and the reducing atmosphere is Ar / H2.

[0031] The present invention provides a fuel cell gas diffusion layer prepared by the preparation method.

[0032] The present invention also provides an application of a fuel cell gas diffusion layer, wherein the gas diffusion layer is used for a hydrogen-oxygen proton exchange membrane fuel cell. Under the reaction conditions of a reaction temperature of 65°C and a reaction humidity of 80 RH%, the fuel cell polarization curve limit power density reaches 1.15 W / cm 2 , and maintain stable operation for more than 15 hours under 0.6V voltage conditions.

[0033] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0034] (1) The present invention provides a method for preparing a fuel cell gas diffusion layer, which is a low-temperature atomization spray-freeze sublimation method. The method has the characteristics of simple process and universal materials. The microporous layer of the obtained gas diffusion layer has the effect of precise control of microscopic channels, and vertically radially arranged channels with uniform depth are obtained. It has good repeatability and is suitable for batch preparation.

[0035] (2) The present invention provides a fuel cell gas diffusion layer having good hydrophobicity, electrical conductivity and structural stability. When the gas diffusion layer is assembled into a fuel cell, it exhibits good electrode performance and stability. The gas diffusion layer is used in a hydrogen-oxygen proton exchange membrane fuel cell. Under the reaction conditions of a reaction temperature of 65°C and a reaction humidity of 80RH%, the fuel cell polarization curve limit power density reaches 1.15W / cm 2 , and maintained stable operation for more than 15 hours at a voltage of 0.6 V. This shows that the fuel cell gas diffusion layer of the present invention can improve gas-liquid transmission efficiency and avoid water flooding problems, effectively extending the service life of the fuel cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a SEM plan view of the fuel cell gas diffusion layer prepared in Example 1;

[0037] Figure 2 This is a SEM cross-sectional view of the fuel cell gas diffusion layer prepared in Example 1;

[0038] Figure 3 This is a contact angle diagram of the fuel cell gas diffusion layer prepared in Example 1;

[0039] Figure 4 This is a polarization curve diagram of the fuel cell gas diffusion layer prepared in Example 1 in a hydrogen-oxygen fuel cell;

[0040] Figure 5 This is a stability curve diagram of the fuel cell gas diffusion layer prepared in Example 1 in a hydrogen-oxygen fuel cell. DETAILED DESCRIPTION

[0041] The following examples further illustrate the specific implementation of the present invention, but the implementation and protection of the present invention are not limited thereto. It should be noted that if there are any processes not specifically described below, they can be implemented or understood by those skilled in the art with reference to the prior art. If the manufacturer of the reagents or instruments used is not indicated, they are deemed to be conventional products that can be purchased commercially.

[0042] Example 1

[0043] A method for preparing a fuel cell gas diffusion layer

[0044] (1) Carbon paper cut to a size of 2.5 cm*2.5 cm was impregnated in a polytetrafluoroethylene emulsion with a concentration of 5.5 wt% for 5 min; then it was transferred to an oven for drying at 80 °C, and finally annealed and sintered twice in a muffle furnace. The first sintering temperature was 250 °C, the sintering time was 30 min, and the heating rate was 5 °C / min. The last sintering temperature was 350 °C, the sintering time was 30 min, and the heating rate was 5 °C / min, to obtain a hydrophobic pretreated support base.

[0045] (2) 18.75 mg of carbon black, 6.25 mg of carbon nanotubes, 6.25 mg of graphene oxide and 13 mg (60 wt%) of polytetrafluoroethylene emulsion were added to 6 ml of a mixed solution of ethanol and deionized water (ethanol: deionized water = 1:1), and ultrasonically dispersed for 3 h at an ultrasonic frequency of 20 kHz to obtain a uniformly dispersed carbon material slurry.

[0046] (3) Take 2 ml of the carbon material dispersion obtained in step (2) and use a spray gun to evenly spray it on one side of the surface of the hydrophobic pretreated support base obtained in step (1) under low temperature conditions. The carbon material slurry concentration is 5.2 mg / ml, the low temperature condition temperature is -147°C, and the spraying rate is 75 μl / min to obtain a support base containing slurry in a frozen state.

[0047] (4) freeze-drying the support base containing the slurry in the frozen state obtained in step (3) at a freezing temperature of -80°C and a drying time of 48 hours to obtain a support base with a microporous layer.

[0048] (5) The support substrate containing the microporous layer obtained in step (4) was placed in a muffle furnace for annealing and sintering at a temperature of 350°C, a sintering time of 30 minutes, and a heating rate of 5°C / min. The support substrate containing the microporous layer obtained by annealing and sintering was then placed in a tubular furnace for reduction at a temperature of 200°C, a sintering time of 90 minutes, a heating rate of 5°C / min, and an Ar / H2 reducing atmosphere to obtain a gas diffusion layer, which was labeled as CB-CNTs / GO. LT .

[0049] The SEM plan view and cross-sectional view of the fuel cell gas diffusion layer prepared in Example 1 are shown in FIG. Figure 1 and Figure 2 As shown in the figure, the preparation of the uniformly distributed porous structure and the pore structure with uniform depth can be confirmed; the contact angle diagram of the fuel cell gas diffusion layer prepared in Example 1 is shown in FIG. Figure 3 As shown, it can be observed that the contact angle of the gas diffusion layer surface is 153.3°, showing a superhydrophobic effect.

[0050] Example 2

[0051] A method for preparing a fuel cell gas diffusion layer

[0052] (1) Carbon paper cut to a size of 2.5 cm*2.5 cm was impregnated in a polytetrafluoroethylene emulsion with a concentration of 5.5 wt% for 5 min; then it was transferred to an oven for drying at 80 °C, and finally annealed and sintered three times in a muffle furnace. The first sintering temperature was 250 °C, the sintering time was 30 min, and the heating rate was 5 °C / min. The last sintering temperature was 350 °C, the sintering time was 30 min, and the heating rate was 5 °C / min, to obtain a hydrophobic pretreated support base.

[0053] (2) 18.75 mg of carbon black, 6.25 mg of carbon nanotubes, 6.25 mg of graphene oxide and 13 mg (60 wt%) of polytetrafluoroethylene emulsion were added to 6 ml of a mixed solution of ethanol and deionized water (ethanol: deionized water = 1:1), and ultrasonically dispersed for 3 h at an ultrasonic frequency of 20 kHz to obtain a uniformly dispersed carbon material slurry.

[0054] (3) Take 2 ml of the carbon material dispersion obtained in step (2) and use a spray gun to evenly spray it on one side of the surface of the hydrophobic pretreated support base obtained in step (1) under high temperature conditions. The carbon material slurry concentration is 5.2 mg / ml, the low temperature condition temperature is 80°C, and the spraying rate is 75 μl / min to obtain a support base containing slurry under high temperature conditions.

[0055] (4) The support base containing the slurry obtained in the high temperature state in step (3) is not freeze-dried, but transferred to an oven for drying at a drying temperature of 80° C. and a drying time of 2 h to obtain a support base with a microporous layer.

[0056] (5) The support substrate containing the microporous layer obtained in step (4) was placed in a muffle furnace for annealing and sintering at a temperature of 350°C, a sintering time of 30 minutes, and a heating rate of 5°C / min. The support substrate containing the microporous layer obtained by annealing and sintering was then placed in a tubular furnace for reduction at a temperature of 200°C, a sintering time of 90 minutes, a heating rate of 5°C / min, and an Ar / H2 reducing atmosphere to obtain a gas diffusion layer, which was labeled as CB-CNTs / GO. HT .

[0057] Example 3

[0058] A method for preparing a fuel cell gas diffusion layer

[0059] (1) Carbon paper cut into a size of 2.5 cm*2.5 cm was impregnated in a polytetrafluoroethylene emulsion with a concentration of 5.5 wt% for 5 min; then it was transferred to an oven for drying at 80 °C, and finally annealed and sintered five times in a muffle furnace, with the first sintering temperature at 250 °C, the sintering time at 30 min, and the heating rate at 5 °C / min; the last sintering temperature at 350 °C, the sintering time at 30 min, and the heating rate at 5 °C / min to obtain a hydrophobic pretreated support base.

[0060] (2) 18.75 mg of carbon black, 6.25 mg of carbon nanotubes and 13 mg (60 wt%) of polytetrafluoroethylene emulsion were added to 6 ml of a mixed solution of ethanol and deionized water (ethanol: deionized water = 1:1), and ultrasonically dispersed for 3 h at an ultrasonic frequency of 20 kHz to obtain a uniformly dispersed carbon material slurry.

[0061] (3) Take 2 ml of the carbon material dispersion obtained in step (2) and use a spray gun to evenly spray it on one side of the surface of the hydrophobic pretreated support base obtained in step (1) under low temperature conditions. The carbon material slurry concentration is 5.2 mg / ml, the low temperature condition temperature is -147°C, and the spraying rate is 75 μl / min to obtain a support base containing slurry in a frozen state.

[0062] (4) freeze-drying the support base containing the slurry in the frozen state obtained in step (3) at a freezing temperature of -80°C and a drying time of 48 hours to obtain a support base with a microporous layer.

[0063] (5) The support substrate containing the microporous layer obtained in step (4) is placed in a muffle furnace for annealing and sintering at a temperature of 350°C, a sintering time of 30 minutes, and a heating rate of 5°C / min. The support substrate containing the microporous layer obtained by annealing and sintering is then placed in a tubular furnace for reduction at a temperature of 200°C, a sintering time of 90 minutes, a heating rate of 5°C / min, and an Ar / H2 reducing atmosphere to obtain a gas diffusion layer, which is labeled as CB-CNTs. LT .

[0064] Example 4

[0065] A method for preparing a fuel cell gas diffusion layer

[0066] (1) Carbon paper cut to a size of 2.5 cm*2.5 cm was impregnated in a polytetrafluoroethylene emulsion with a concentration of 5.5 wt% for 5 min; then it was transferred to an oven for drying at 80 °C, and finally annealed and sintered three times in a muffle furnace. The first sintering temperature was 250 °C, the sintering time was 30 min, and the heating rate was 5 °C / min. The last sintering temperature was 350 °C, the sintering time was 30 min, and the heating rate was 5 °C / min, to obtain a hydrophobic pretreated support base.

[0067] (2) 18.75 mg of carbon black, 6.25 mg of graphene oxide and 13 mg (60 wt%) of polytetrafluoroethylene emulsion were added to 6 ml of a mixed solution of ethanol and deionized water (ethanol: deionized water = 1:1), and ultrasonically dispersed for 3 h at an ultrasonic frequency of 20 kHz to obtain a uniformly dispersed carbon material slurry.

[0068] (3) Take 2 ml of the carbon material dispersion obtained in step (2) and use a spray gun to evenly spray it on one side of the surface of the hydrophobic pretreated support base obtained in step (1) under low temperature conditions. The carbon material slurry concentration is 5.2 mg / ml, the low temperature condition temperature is -147°C, and the spraying rate is 75 μl / min to obtain a support base containing slurry in a frozen state.

[0069] (4) freeze-drying the support base containing the slurry in the frozen state obtained in step (3) at a freezing temperature of -80°C and a drying time of 48 hours to obtain a support base with a microporous layer.

[0070] (5) The support substrate containing the microporous layer obtained in step (4) is placed in a muffle furnace for annealing and sintering at a temperature of 350°C, a sintering time of 30 minutes, and a heating rate of 5°C / min. The support substrate containing the microporous layer obtained by annealing and sintering is then placed in a tubular furnace for reduction at a temperature of 200°C, a sintering time of 90 minutes, a heating rate of 5°C / min, and an Ar / H2 reducing atmosphere to obtain a gas diffusion layer, which is labeled as CB-GO. LT .

[0071] Example 5

[0072] A method for preparing a fuel cell gas diffusion layer

[0073] (1) Carbon paper cut to a size of 2.5 cm*2.5 cm was impregnated in a polytetrafluoroethylene emulsion with a concentration of 5.5 wt% for 5 min; then it was transferred to an oven for drying at 80 °C, and finally annealed and sintered twice in a muffle furnace. The first sintering temperature was 250 °C, the sintering time was 30 min, and the heating rate was 5 °C / min. The last sintering temperature was 350 °C, the sintering time was 30 min, and the heating rate was 5 °C / min, to obtain a hydrophobic pretreated support base.

[0074] (2) 18.75 mg of carbon black and 13 mg (60 wt%) of polytetrafluoroethylene emulsion were added to 6 ml of a mixed solution of ethanol and deionized water (ethanol: deionized water = 1:1), and ultrasonic dispersion was performed. The ultrasonic time was 3 h and the ultrasonic frequency was 20 kHz to obtain a uniformly dispersed carbon material slurry.

[0075] (3) Take 2 ml of the carbon material dispersion obtained in step (2) and use a spray gun to evenly spray it on one side of the surface of the hydrophobic pretreated support base obtained in step (1) under low temperature conditions. The carbon material slurry concentration is 5.2 mg / ml, the low temperature condition temperature is -147°C, and the spraying rate is 75 μl / min to obtain a support base containing slurry in a frozen state.

[0076] (4) freeze-drying the support base containing the slurry in the frozen state obtained in step (3) at a freezing temperature of -80°C and a drying time of 48 hours to obtain a support base with a microporous layer.

[0077] (5) The support substrate containing the microporous layer obtained in step (4) is placed in a muffle furnace for annealing and sintering at a temperature of 350°C, a sintering time of 30 minutes, and a heating rate of 5°C / min. The support substrate containing the microporous layer obtained by annealing and sintering is then placed in a tubular furnace for reduction at a temperature of 200°C, a sintering time of 90 minutes, a heating rate of 5°C / min, and an Ar / H2 reducing atmosphere to obtain a gas diffusion layer, which is labeled as CB. LT .

[0078] Example 6

[0079] In order to explore the polarization curve performance of the fuel cell of the gas diffusion layer prepared in Example 1, the gas diffusion layer CB-CNTs / GO LTA stability experiment was conducted in a hydrogen-oxygen proton exchange membrane fuel cell. The reaction conditions were as follows: after assembling the fuel cell, saturated nitrogen was introduced into the fuel cell test system for 30 seconds, and then hydrogen and oxygen were introduced into the anode side and cathode side, respectively, with a hydrogen to oxygen ratio of 1:3. At the same time, the fuel cell was heated to 65°C. The fuel gas was introduced until the open circuit voltage of the fuel cell was stable. First, the reaction constant voltage was set to 0.6V and activated for 4 hours. During the reaction, the fuel gas pipeline pressure was kept less than or equal to 0.4MPa. After the activation was completed, the potential step method was used to set the voltage from 0.9V to 0.25V, the voltage interval was 0.2V, the single voltage point reaction time was 10s, the gas line pressure and temperature were maintained, the fuel cell polarization curve of the fuel cell at the set voltage was observed and the relevant data was recorded to obtain the gas diffusion layer CB-CNTs / GO prepared in Example 1 above. LT Polarization curves in a hydrogen-oxygen proton exchange membrane fuel cell.

[0080] Figure 4 The fuel cell gas diffusion layer CB-CNTs / GO described in Example 6 LT Polarization curve diagram in hydrogen-oxygen fuel cell. Figure 4 It can be seen that the prepared gas diffusion layer assembled fuel cell polarization curve limit power density reaches 1.15W / cm2, showing a gentle ohmic polarization and concentration polarization process.

[0081] Example 7

[0082] In order to verify the stability of the fuel cell of the gas diffusion layer prepared, the gas diffusion layer CB-CNTs / GO prepared in Example 1 was used. LT A stability experiment was conducted in a hydrogen-oxygen proton exchange membrane fuel cell. The reaction conditions were as follows: After assembling the fuel cell, saturated nitrogen was introduced into the fuel cell test system for 30 seconds, and then hydrogen and oxygen were introduced into the anode and cathode sides, respectively, with a hydrogen to oxygen ratio of 1:3. At the same time, the fuel cell was heated to 65°C. The fuel gas was introduced until the open circuit voltage of the fuel cell was stable. First, the reaction constant voltage was set to 0.6V and activated for 4 hours. During the reaction, the fuel gas pipeline pressure was kept less than or equal to 0.4MPa. After the activation was completed, the reaction constant voltage was set to 0.6V again, and the gas line pressure and temperature were maintained. The current density curve of the fuel cell at the set voltage was observed and the relevant data was recorded to obtain the gas diffusion layer CB-CNTs / GO prepared in Example 1 above. LT Stability experimental curve in hydrogen-oxygen proton exchange membrane fuel cell.

[0083] Figure 5 The gas diffusion layer CB-CNTs / GO described in Example 7 LT Stability curve in hydrogen-oxygen fuel cell. Figure 5It can be seen that the fuel cell assembled with the prepared gas diffusion layer maintains stable operation for more than 15 hours under rated conditions, showing an optimized service life.

[0084] The above embodiments are only preferred implementation modes of the present invention and are only used to explain the present invention rather than to limit the present invention. Any changes, substitutions, modifications, etc. made by those skilled in the art without departing from the spirit of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for preparing a fuel cell gas diffusion layer, characterized in that: The gas diffusion layer is constructed by a low-temperature atomization-freeze sublimation method, which specifically includes the following steps: (1) Perform hydrophobic pretreatment on the carbon fiber substrate; (2) adding the carbon material and the hydrophobic agent emulsion into an organic solvent and deionized water, and ultrasonically dispersing the mixture to obtain a uniform carbon material slurry; (3) spraying the uniform carbon material slurry obtained in step (2) uniformly on one side of the surface of the hydrophobic pretreated support base obtained in step (1) using a spray gun under low temperature conditions to obtain a support base containing the slurry in a frozen state; the low temperature condition is -150 to -10°C; (4) freeze-drying the support base containing the slurry in the frozen state obtained in step (3) to obtain a support base with a microporous layer; (5) Annealing, sintering and reducing the support base layer with the microporous layer obtained in step (4) to obtain a gas diffusion layer.

2. The method for preparing a fuel cell gas diffusion layer according to claim 1, characterized in that: In step (1), the carbon fiber substrate includes any one of carbon paper, carbon cloth, and carbon felt.

3. The method for preparing a fuel cell gas diffusion layer according to claim 1, characterized in that: In step (1), the hydrophobic pretreatment includes: dipping the carbon fiber substrate in a hydrophobic agent emulsion for 5-15 minutes, the hydrophobic agent emulsion concentration is 1 wt%-11wt%, and then transferring it to an oven for drying at a drying temperature of 60-100°C, and finally annealing and sintering in a muffle furnace 2-5 times, the first sintering temperature is 200-300°C, the sintering time is 10-60 minutes, the heating rate is 1-10°C / min, and the last sintering temperature is 300-400°C, the sintering time is 10-60 minutes, and the heating rate is 1-10°C / min.

4. The method for preparing a fuel cell gas diffusion layer according to claim 1, characterized in that: In step (2), the carbon material includes one or more of carbon black, carbon nanotubes, and graphene oxide; and the hydrophobic agent emulsion includes one of polytetrafluoroethylene emulsion, polyvinylidene fluoride emulsion, and tetrafluoroethylene emulsion.

5. The method for preparing a fuel cell gas diffusion layer according to claim 1, characterized in that: In step (2), the organic solvent includes one of ethanol, isopropanol, and n-propanol; the volume ratio of the organic solvent to deionized water is 1:0.1-10; the ultrasonic dispersion time is 1-4 hours, and the ultrasonic dispersion frequency is 20-40 kHz.

6. The method for preparing a fuel cell gas diffusion layer according to claim 1, characterized in that: In step (3), the carbon material slurry concentration is 3.5-5.5 mg / ml; the spraying rate is 50-100 μl / min; the carbon material loading in the slurry-containing support base is 0.5-3.0 mg / cm 2 .

7. The method for preparing a fuel cell gas diffusion layer according to claim 1, characterized in that: In step (4), the freezing temperature is -198~0°C and the drying time is 24-48h.

8. The method for preparing a fuel cell gas diffusion layer according to claim 1, characterized in that: In step (5), the annealing sintering temperature is 200-300°C, the sintering time is 10-60min, and the heating rate is 1-10°C / min; the reduction temperature is 200-300°C, the reduction time is 60-120min, the heating rate is 1-10°C / min, and the reducing atmosphere is one of Ar / H2, N2 / H2, CH4 / H2, and H2.

9. A fuel cell gas diffusion layer prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The gas diffusion layer comprises a supporting base layer and a microporous layer, which has a porous structure and a pore structure with uniform depth, and the surface of the gas diffusion layer exhibits a hydrophobic effect.

10. Use of the fuel cell gas diffusion layer according to claim 9 in a hydrogen-oxygen proton exchange membrane fuel cell.

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