Preparation method of fuel cell membrane electrode

Abstract

The invention discloses a preparation method of a fuel cell membrane electrode, which comprises the following steps: mixing and dispersing a spinnable polymer, a carbon carrier and a pore-forming agent to prepare spinning slurry, and then carrying out processes of spinning by an electrostatic spinning machine, magnetron sputtering and the like to construct a fiber skeleton of a proton, electron and reactant three-phase interface so as to obtain a high-stability electrostatic spinning electrode with low Pt content. And the stability and durability of the electrode are improved.

Description

Technical Field

[0001] This invention belongs to the field of proton exchange membrane fuel cell technology, specifically relating to a method for preparing a fuel cell membrane electrode. Background Technology

[0002] A fuel cell is a power generation device that directly converts chemical energy into electrical energy. Because its energy conversion efficiency is not limited by the Carnot cycle, it boasts advantages such as high energy conversion efficiency and high specific energy. Furthermore, the fuel cell emits no pollutants during operation, making it environmentally friendly; it only generates water during operation. Due to these outstanding advantages, proton exchange membrane fuel cell technology is considered the preferred clean and efficient power generation technology of the 21st century and has received significant attention from governments worldwide.

[0003] Membrane electrode assembly (MEA) is a core component of fuel cells, and its material, structure, and other physical properties directly determine the cost and performance of the fuel cell. Based on the location of the catalyst layer attachment, MEAs can be divided into two types: gas-displacement (GDE) with the catalyst layer coated on the gas diffusion layer and electrolyte membrane (CCM) with the catalyst layer coated on the electrolyte membrane. However, both types of MEAs suffer from drawbacks such as low catalyst utilization, large catalyst consumption, and a lack of ordered proton / electron transport channels, becoming a significant bottleneck in the development of MEAs. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a fuel cell membrane electrode, which can obtain a high-stability electrospun electrode with low Pt content, thereby improving the stability and durability of the electrode.

[0005] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a method for preparing a fuel cell membrane electrode, comprising the following steps: 1) Preparation of spinning slurry 1: The perfluorosulfonic acid resin solution, carbon carrier, polymer binder, pore-forming agent and solvent are ultrasonically mixed to obtain spinning slurry 1; 2) Preparation of spinning slurry 2: Carbon nanotubes, polymer binder, dispersant and solvent are ultrasonically mixed to obtain spinning slurry 2; 3) Inject spinning slurry 1 and spinning slurry 2 into the two syringes of the electrospinning equipment, and install them onto the micro-injector of the spinning machine to spin the slurry. Collect the spun layer with aluminum foil. 4) Remove the spinning layer, calcine it to obtain a catalyst layer with a microporous structure, and then use a hot pressing method to transfer the catalyst layer onto a perfluorosulfonic acid resin membrane. 5) Place the perfluorosulfonic acid resin film with the transferred catalyst layer into a magnetron sputtering instrument. The sputtering target is a Pt target. After sputtering, the membrane electrode is obtained.

[0006] The present invention is further configured such that: the electrospinning equipment in step 3) includes a metal roller covered with aluminum foil, the injection direction of the two syringes is directed toward the outer circumferential wall of the metal roller, and the injection direction of the two syringes is spatially perpendicular in the XZ direction; the spinning slurry 1 is started 3-5 seconds before the spinning slurry 2 process is performed.

[0007] The present invention is further configured such that the polymer binders in spinning slurry 1 and spinning slurry 2 are both mixtures of one or more of polyacrylonitrile, polyaniline, and polyvinylpyrrolidone; The carbon support in the spinning slurry 1 is XC-72 or graphene; the pore-forming agent is a mixture of one or more of sodium bicarbonate, sodium citrate, sucrose, and glucose; and the solvent is a mixture of isopropanol and water. The dispersant in the spinning slurry 2 includes one of Triton X-100, PVPK30, and Pluronic F127, and the solvent is a mixture of ethanol, water, and glycerol.

[0008] The present invention is further configured such that: the mass ratio of perfluorosulfonic acid resin to polymer binder in the spinning slurry 1 is 1:1-5:1, the particle size of the pore-forming agent is 10-50μm, and the mass ratio of the pore-forming agent to the carbon carrier is 1:5-1:10; the total solid content of the spinning slurry 1 is 12-20%; the volume ratio of water to isopropanol in the solvent is 1:1-1:3; and the viscosity of the spinning slurry 1 at 25°C is 500-2000cp. The mass ratio of carbon nanotubes to polymer binder in the spinning slurry 2 is 1:0.4-1:0.6, the mass ratio of carbon nanotubes to dispersant is 1:0.2-1:0.5, the volume ratio of ethanol to water in the solvent of the spinning slurry 2 is 1:0.3-1:1.5, the volume ratio of glycerol to ethanol is 1:3-1:12, the total solid content of the spinning slurry 2 is 12-20%, and the viscosity of the spinning slurry 2 at 25°C is 500-2000 cp.

[0009] The present invention is further configured such that: the technical parameters of the electrospinning process of the spinning slurry 1 in step 3) are: liquid flow rate of 0.5-1 ml / h, needle tip distance from receiving plate of 15-20 cm, voltage of 12-15 kV, and receiving time of 2-4 h; the technical parameters of the electrospinning process of the spinning slurry 2 are: liquid flow rate of 1-1.5 ml / h, needle tip distance from receiving plate of 18-25 cm, voltage of 8-15 kV, and receiving time of 1.5-3.5 h.

[0010] The present invention is further configured such that: in step 4), the calcination temperature is 600-800℃ and the calcination time is 2-6h.

[0011] The present invention is further configured such that: in step 5, the sputtering power of magnetron sputtering is 200-500W, the sputtering time is 8-20min, and the corresponding Pt loading is 0.05-0.2mg / cm².

[0012] The present invention is further configured such that the thickness of the catalyst layer prepared in step 4) is 5-20 μm.

[0013] The present invention is further configured such that: in step 4), the hot pressing temperature is 110-140℃, the pressure is 0.5-2MPa, and the hot pressing time is 2-10min.

[0014] The present invention is further configured such that: the power density of the membrane electrode is ≥1.5W / cm² at a voltage of 0.6V, and the Pt loading is ≤0.2mg / cm².

[0015] In summary, the present invention has the following beneficial effects: 1. This application prepares a spinning slurry by mixing and dispersing a spinnable polymer, a carbon carrier, and a pore-forming agent. Then, through electrospinning, calcination, magnetron sputtering, and other processes, a nanofiber framework with a proton, electron, and reactant three-phase interface is constructed. This effectively reduces the Pt content while also providing a highly stable electrospinning electrode, thus improving the stability and durability of the electrode.

[0016] 2. Electrospinning has advantages such as simple equipment, low spinning cost, wide variety of spinnable materials, and controllable process, and can effectively prepare high specific surface area fibers. However, the dense surface of the fibers limits the further increase of their specific surface area and restricts the utilization rate of active components. Therefore, this invention increases the specific surface area of ​​the fibers by adding an easily removable pore-forming agent, and uses magnetron sputtering technology to construct a Pt atomic layer on the increased fiber surface. Thus, without requiring too much Pt, the utilization rate of Pt can be effectively and significantly improved, thereby improving the performance of the membrane electrode.

[0017] 3. To address the disadvantage of low mechanical strength in fibrous catalysts obtained through electrospinning, this invention further incorporates a slurry 2, which is deposited using a second syringe in mutually perpendicular directions. This creates a cross-linked network structure in both the longitudinal and transverse directions. This interlaced structure allows the fibers of slurry 2 to act as a "skeleton" supporting the catalyst layer of slurry 1, distributing mechanical stress and resulting in a more balanced mechanical property of the overall layer structure. Furthermore, carbon nanotubes enhance conductivity and mechanical strength, while the polymer binder improves toughness. Additionally, because slurry 1 contains a pore-forming agent, its fiber diameter is typically larger, while the carbon nanotube fibers in slurry 2 are finer. The interlacing of these two types of fibers forms a reinforced structure similar to "reinforced concrete," further strengthening the mechanical strength of the catalyst layer. Finally, during hot pressing, the perfluorosulfonic acid resin in slurry 1 softens and fuses with the PTFE binder in slurry 2, further enhancing interfacial bonding.

[0018] 4. In this invention, when two syringes are set up for electrospinning, the spinning slurry 1 is designed to start 3-5 seconds before the spinning slurry 2 process is carried out. That is, slurry 1 first forms a catalytically active substrate layer mainly composed of perfluorosulfonic acid resin / carbon support to ensure proton conduction and catalytic site enrichment. Then, slurry 2 is superimposed, and CNT reinforcing fibers are embedded in the substrate layer in a vertical direction to form a three-dimensional conductive skeleton, which greatly improves the in-plane conductivity. In addition, after the substrate layer is pre-cured in this process, the fibers of slurry 2 are injected vertically to achieve mechanical interlocking and bonding with slurry 1, which greatly strengthens the interlayer bonding force. Attached Figure Description

[0019] Figure 1 The image is a SEM image of Embodiment 1 of the present invention. Figure 2 This is a schematic diagram of the syringe injection positions of spinning slurry 1 and spinning slurry 2 in Examples 1-3; Figure 3 This is a schematic diagram showing the injection positions of the syringes for spinning sizing agent 1 and spinning sizing agent 2 in Comparative Example 3; In the diagram: 1. Injector for spinning slurry 1; 2. Injector for spinning slurry 2; 3. Metal roller. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the accompanying drawings.

[0021] The following examples are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0022] Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained commercially or prepared according to conventional methods known to those skilled in the art.

[0023] Example 1: (1) Preparation of spinning slurry 1: Weigh 5g of polyacrylonitrile and 10g of sodium bicarbonate with a particle size of 50μm, dissolve them in 270ml of isopropanol and 90ml of water, stir until a homogeneous solution is obtained, then add 25g of perfluorosulfonic acid resin and 50g of XC-72 and mix evenly. Ultrasonicate for 3h to obtain spinning slurry 1 with a viscosity of 2000cp; (2) Preparation of spinning slurry 2: Weigh 10g carbon nanotubes, 6g polyaniline and 5g Triton X-100 and mix them. Then add 17ml glycerol, 52ml ethanol and 16ml water and ultrasonically disperse for 3h to obtain spinning slurry 2 with a viscosity of 2000cp. (3) An electrospinning device is used. The electrospinning device provided by this invention includes two syringes and a metal roller covered with aluminum foil. Spinning slurry 1 and spinning slurry 2 are injected into the two syringes of the electrospinning device, respectively, and installed on the micro-injector of the spinning machine, i.e., syringe 1 for spinning slurry 1 and syringe 2 for spinning slurry 2. The injection directions of the two syringes are spatially perpendicular in the XZ direction, such as... Figure 2 As shown, spinning slurry 1 is in the X direction and spinning slurry 2 is in the Y direction. The equipment power is then turned on for spinning. Spinning slurry 1 starts for 5 seconds before spinning slurry 2 is applied. The metal roller 3, covered with aluminum foil, rotates clockwise to collect the spun yarn. The parameters for spinning slurry 1 are set as follows: slurry 1 feed rate is 1 ml / h, needle tip distance to receiving plate is 20 cm, voltage is 15 kV, and receiving time is 4 h. The parameters for spinning slurry 2 are set as follows: slurry 2 feed rate is 1.5 ml / h, needle tip distance to receiving plate is 25 cm, voltage is 15 kV, and receiving time is 3.5 h. (4) The spinning layer obtained in step (3) is placed in a tube furnace and calcined at 800°C for 6 hours in a gas atmosphere of N2 to obtain a spinning layer with a porous structure with a thickness of 19.6 μm. (5) The porous spinning layer in (4) is hot-pressed and transferred to both sides of the perfluorosulfonic acid resin film. The hot-pressing temperature is 140℃, the hot-pressing pressure is 2MPa, and the hot-pressing time is 10min. (6) The perfluorosulfonic acid resin membrane with the catalyst layer transferred in (5) is placed in a magnetron sputtering instrument. The sputtering target is a Pt target, the sputtering power is 500W, the sputtering time is 20min, and a membrane electrode with a Pt loading of 0.18mg / cm² is obtained after sputtering.

[0024] Example 2: (1) Preparation of spinning slurry 1: Weigh 5g of polyvinylpyrrolidone and 5g of sodium citrate with a particle size of 20μm, dissolve them in 200ml of isopropanol and 100ml of water, stir until a homogeneous solution is obtained, then add 15g of perfluorosulfonic acid resin and 35g of graphene and mix evenly, and sonicate for 2.5h to obtain spinning slurry 1 with a viscosity of 1250cp; (2) Preparation of spinning slurry 2: Weigh 10g carbon nanotubes, 5g polyacrylonitrile, and 3.5g PVPK30 and mix them. Then add 8ml glycerol, 40ml ethanol, and 36ml water and ultrasonically disperse for 2.5h to obtain spinning slurry 2 with a viscosity of 1250cp. (3) Inject spinning slurry 1 and spinning slurry 2 into the two syringes of the electrospinning equipment, respectively, and install them onto the micro-injector of the spinning machine. The injection directions of the two syringes are perpendicular to the XZ direction in space, as shown below. Figure 2As shown, spinning slurry 1 is in the X direction and spinning slurry 2 is in the Y direction. The equipment power is then turned on for spinning. Spinning slurry 1 starts for 4 seconds before spinning slurry 2 is processed. The metal roller covered with aluminum foil rotates clockwise to collect the spun layer. The parameters for spinning slurry 1 are set as follows: slurry 1 feed rate is 0.8 ml / h, needle tip distance from receiving plate is 18 cm, voltage is 13 kV, and receiving time is 3 h. The parameters for spinning slurry 2 are set as follows: slurry 2 feed rate is 1.3 ml / h, needle tip distance from receiving plate is 20 cm, voltage is 12 kV, and receiving time is 2.5 h. (4) The spinning layer obtained in step (3) is placed in a tube furnace and calcined at 700°C for 4 hours in a gas atmosphere of N2 to obtain a spinning layer with a porous structure with a thickness of 14.3 μm. (5) The porous spinning layer in (4) is hot-pressed and transferred to both sides of the perfluorosulfonic acid resin film. The hot-pressing temperature is 130℃, the hot-pressing pressure is 1MPa, and the hot-pressing time is 5min. (6) The perfluorosulfonic acid resin membrane with the catalyst layer transferred in (5) is placed in a magnetron sputtering instrument. The sputtering target is a Pt target, the sputtering power is 350W, the sputtering time is 14min, and a membrane electrode with a Pt loading of 0.14mg / cm² is obtained after sputtering.

[0025] Example 3: (1) Preparation of spinning slurry 1: Weigh 5g of polyvinylpyrrolidone and 5g of glucose with a particle size of 10μm, dissolve them in 180ml of isopropanol and 60ml of water, stir until a homogeneous solution is obtained, then add 5g of perfluorosulfonic acid resin and 25g of XC-72 carbon powder and mix evenly. Ultrasonically for 2h to obtain spinning slurry 1 with a viscosity of 500cp; (2) Preparation of spinning slurry 2: Weigh 10g carbon nanotubes, 6g polyacrylonitrile and 5g Pluronic F127 and mix them. Then add 4ml glycerol, 40ml ethanol and 60ml water and ultrasonically disperse for 2h to obtain spinning slurry 2 with a viscosity of 500cp. (3) Inject spinning slurry 1 and spinning slurry 2 into the two syringes of the electrospinning equipment, respectively, and install them onto the micro-injector of the spinning machine. The injection directions of the two syringes are perpendicular to the XZ direction in space, as shown below. Figure 2As shown, spinning slurry 1 is in the X direction and spinning slurry 2 is in the Y direction. The equipment power is then turned on for spinning. Spinning slurry 1 starts for 3 seconds before spinning slurry 2 is processed. The metal roller covered with aluminum foil rotates clockwise to collect the spun layer. The parameters for spinning slurry 1 are set as follows: slurry 1 feed rate is 0.5 ml / h, needle tip distance from receiving plate is 15 cm, voltage is 12 kV, and receiving time is 2 h. The parameters for spinning slurry 2 are set as follows: slurry 2 feed rate is 1 ml / h, needle tip distance from receiving plate is 18 cm, voltage is 8 kV, and receiving time is 1.5 h. (4) The spinning layer obtained in step (3) is placed in a tube furnace and calcined at 600°C for 2 hours in a gas atmosphere of N2 to obtain a spinning layer with a porous structure and a thickness of 6.5 μm. (5) The porous spinning layer in (4) is hot-pressed onto both sides of the perfluorosulfonic acid resin film. The hot-pressing temperature is 110℃, the hot-pressing pressure is 0.5MPa, and the hot-pressing time is 2min. (6) The perfluorosulfonic acid resin membrane with the catalytic layer transferred in (5) was placed in a magnetron sputtering instrument. The sputtering target was a Pt target, the sputtering power was 200W, and the sputtering time was 8min. After sputtering, a membrane electrode with a Pt loading of 0.08mg / cm² was obtained.

[0026] Comparative Example 1 uses the same preparation method as Example 1, except that the spinning slurry 1 does not contain a pore-forming agent. The preparation method is as follows: (1) Prepare spinning slurry 1: Weigh 5g of polyacrylonitrile and dissolve it in 270ml of isopropanol and 90ml of water, stir until a homogeneous solution is obtained, then add 25g of perfluorosulfonic acid resin and 50g of XC-72 carbon powder and mix evenly. Ultrasonically for 3h to obtain spinning slurry 1 with a viscosity of 2000cp. (2) Preparation of spinning slurry 2: Weigh 10g carbon nanotubes, 6g polyaniline and 5g Triton X-100 and mix them. Then add 17ml glycerol, 52ml ethanol and 16ml water and ultrasonically disperse for 3h to obtain spinning slurry 2 with a viscosity of 2000cp. (3) Inject spinning slurry 1 and spinning slurry 2 into the two syringes of the electrospinning equipment, respectively, and install them onto the micro-injector of the spinning machine. The injection directions of the two syringes are perpendicular to the XZ direction in space, as shown below. Figure 2As shown, the equipment power is then turned on for spinning. Spinning slurry 1 is started for 5 seconds, followed by the spinning slurry 2 process. The spinning layer is collected using aluminum foil. The parameters for spinning slurry 1 are set as follows: slurry 1 feed rate is 1 ml / h, needle tip distance from receiving plate is 20 cm, voltage is 15 kV, and receiving time is 4 h. The parameters for spinning slurry 2 are set as follows: slurry 2 feed rate is 1.5 ml / h, needle tip distance from receiving plate is 25 cm, voltage is 15 kV, and receiving time is 3.5 h. (4) The spinning layer in (3) is hot-pressed and transferred to both sides of the perfluorosulfonic acid resin film. The hot-pressing temperature is 140℃, the hot-pressing pressure is 3MPa, and the hot-pressing time is 10min. (5) Place the perfluorosulfonic acid resin film with the catalytic layer transferred in (4) into a magnetron sputtering instrument. The sputtering target is a Pt target, the sputtering power is 500W, and the sputtering time is 20min. The final membrane electrode is obtained after sputtering.

[0027] Comparative Example 2: The same preparation method as in Example 1 was used, except that it did not contain spinning slurry 2. The preparation method was as follows: (1) Preparation of spinning slurry 1: Weigh 5g of polyacrylonitrile and 10g of sodium bicarbonate with a particle size of 50μm, dissolve them in 270ml of isopropanol and 90ml of water, stir until a homogeneous solution is obtained, then add 25g of perfluorosulfonic acid resin and 50g of XC-72 carbon powder and mix evenly. Ultrasonic for 3h to obtain spinning slurry 1 with a viscosity of 2000cp; (3) Inject the spinning slurry 1 into the syringe of the electrospinning equipment and install it on the micro-injector of the spinning machine. Then turn on the power of the equipment to spin the yarn and collect the spinning layer with aluminum foil. The parameters of the spinning slurry 1 are set as follows: the propulsion flow rate of slurry 1 is 1 ml / h, the distance between the needle tip and the receiving plate is 20 cm, the voltage is 15 kV, and the receiving time is 4 h. (4) The spinning layer obtained in step (3) is placed in a tube furnace and calcined at 800°C for 6 hours in a gas atmosphere of N2 to obtain a spinning layer with a porous structure. (5) The porous spinning layer in (4) is hot-pressed and transferred to both sides of the perfluorosulfonic acid resin film. The hot-pressing temperature is 140℃, the hot-pressing pressure is 3MPa, and the hot-pressing time is 10min. (6) The perfluorosulfonic acid resin membrane with the catalytic layer transferred in (5) was placed in a magnetron sputtering instrument. The sputtering target was a Pt target, the sputtering power was 500W, and the sputtering time was 20min. After sputtering, a membrane electrode with a Pt loading of 0.24mg / cm² was obtained.

[0028] Comparative Example 3: The same preparation method as in Example 1 was used, except that the spinning direction of the spinning sizing agent 2 was spatially parallel to that of the spinning sizing agent 1, such as... Figure 3 As shown.

[0029] Comparative Example 4: The same preparation method as in Example 1 was used, except that spinning slurry 1 and spinning slurry 2 were spun simultaneously. That is, in step (3), spinning slurry 1 and spinning slurry 2 were injected into two syringes of the electrospinning equipment, respectively, and installed on the micro-injector of the spinning machine. The injection directions of the two syringes were perpendicular to each other in the XZ direction. Figure 2 As shown, the equipment power is then turned on for spinning. Spinning slurry 1 and spinning slurry 2 are turned on simultaneously for spinning. The spinning layer is collected using aluminum foil. The parameters of spinning slurry 1 are set as follows: the feed rate of slurry 1 is 1 ml / h, the distance between the needle tip and the receiving plate is 20 cm, the voltage is 15 kV, and the receiving time is 4 h. The parameters of spinning slurry 2 are set as follows: the feed rate of slurry 1 is 1.5 ml / h, the distance between the needle tip and the receiving plate is 25 cm, the voltage is 15 kV, and the receiving time is 3.5 h.

[0030] Test Example: The conductivity of the membrane electrodes of Examples 1-3 and Comparative Examples 1-4 was tested using a four-probe conductivity meter, and the data were recorded in Table 1. The membrane electrodes of Examples 1-3 and Comparative Examples 1-4 were placed in a universal testing machine and stretched at a rate of 1 mm / min. The tensile strength and elongation at break were tested and recorded as shown in Table 1. The membrane electrodes of Examples 1-3 and Comparative Examples 1-4 were placed in a single-cell fixture and subjected to constant voltage testing. The electronic load was set to a constant voltage of 0.6 V, and the current value after stabilization was recorded. The calculated data were recorded in Table 1.

[0031] Table 1 sample Electrical conductivity (S / cm) Tensile strength (MPa) Elongation at break (%) Power density (W / cm²) Example 1 0.52 26.9 13.9 1.91 Example 2 0.51 27.2 14.3 1.89 Example 3 0.53 27.5 13.3 1.88 Comparative Example 1 (without pore-forming agent and not calcined) 0.36 18.6 10.9 0.68 Comparative Example 2 (Spinning slurry 2 without added carbon nanotubes) 0.31 14.5 6.9 0.64 Comparative Example 3 (Two sizing agents are used for parallel injection spinning) 0.47 22.3 11.1 0.71 Comparative Example 4 (Spinning with two different sizing agents simultaneously) 0.45 23.6 11.3 0.78 .

[0032] In Comparative Example 1, no pore-forming agent or calcination process was added, resulting in a decrease in specific surface area and insufficient porosity of the catalyst layer. Consequently, the proton transport path was blocked, the electrical conductivity was low, the ohmic polarization increased, and the current density was significantly reduced, leading to a significant decrease in power density. In addition, the absence of a calcination process in Comparative Example 1 resulted in incomplete pyrolysis of the binder, and the residual organic matter weakened the cross-linking structure of the carbon skeleton, leading to a decrease in interlayer bonding force and thus affecting mechanical strength.

[0033] In Comparative Example 2, the electrical conductivity of spinning sizing agent 2 without added carbon nanotubes was significantly reduced. Furthermore, the electrode fibers lose their "steel reinforcement" effect, resulting in a significant reduction in tensile strength, poor structural integrity, and reduced utilization of sputtered Pt catalyst, thus leading to poor power density.

[0034] In Comparative Example 3, the parallel spraying of the two slurries resulted in the two fibers forming a stacked structure in the same direction, rather than the perpendicular interweaving in the XZ direction as in Example 1. Therefore, the mechanical interlocking effect between the fibers was weakened, and interlayer delamination was more likely to occur, thus reducing the mechanical properties. In addition, the uneven distribution of the fiber layers also led to uneven pore distribution, resulting in a reduction in mass transfer channels. Therefore, the local current density was uneven, and the power density of the membrane electrode was also reduced.

[0035] In Comparative Example 4, the two sizing agents have no time difference and are spun simultaneously. That is, the spinning sizing agent 1 cannot form a solid substrate first. At this time, the two sizing agents may experience solvent miscibility during deposition, and the disordered stacking cannot achieve mechanical interlocking of the fibers in sizing agent 2. The interlayer bonding force is weakened, and thus the mechanical properties are reduced.

[0036] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for preparing a fuel cell membrane electrode, characterized by, The method comprises the following steps: 1) preparing a spinning slurry 1: ultrasonic mixing of a perfluorosulfonic acid resin solution, a carbon carrier, a polymer binder, a pore-forming agent, and a solvent to obtain the spinning slurry 1; 2) preparing a spinning slurry 2: ultrasonic mixing of carbon nanotubes, a polymer binder, a dispersing agent, and a solvent to obtain the spinning slurry 2; 3) injecting the spinning slurry 1 and the spinning slurry 2 into two injectors of an electrospinning device respectively, spinning the slurries, and collecting the spinning layers with aluminum foil; 4) removing the spinning layers, calcining to obtain a catalytic layer with a microporous structure, and then transferring the catalytic layer to a perfluorosulfonic acid resin film by a hot-pressing method; 5) placing the perfluorosulfonic acid resin film with the transferred catalytic layer into a magnetron sputtering instrument, using a Pt target for sputtering, and obtaining a membrane electrode after sputtering.

2. The method of claim 1, wherein: The electrospinning device in step 3) comprises a metal roller coated with aluminum foil, the spraying directions of the two injectors are both towards the outer circumferential wall of the metal roller, and the spraying directions of the two injectors are vertically in the X-Z direction; the spinning slurry 1 is started for 3-5 seconds first, and then the spinning slurry 2 process is performed.

3. The method of claim 1, wherein: The polymer binder in the spinning slurry 1 and the spinning slurry 2 is a mixture of one or more of polyacrylonitrile, polyaniline, and polyvinylpyrrolidone; The carbon carrier in the spinning slurry 1 is XC-72 or graphene, the pore-forming agent is a mixture of one or more of sodium bicarbonate, sodium citrate, sucrose, and glucose, and the solvent is a mixture of isopropyl alcohol and water; The dispersing agent in the spinning slurry 2 comprises one of Triton X-100, PVP K30, and Pluronic F127, and the solvent is a mixture of ethanol, water, and glycerol.

4. The method of claim 1, wherein: The mass ratio of the perfluorosulfonic acid resin to the polymer binder in the spinning slurry 1 is 1:1-5:1, the particle size of the pore-forming agent is 10-50 μm, the mass ratio of the pore-forming agent to the carbon carrier is 1:5-1:10, the total solid content of the spinning slurry 1 is 12-20%, the volume ratio of water to isopropyl alcohol in the solvent is 1:1-1:3, and the 25°C viscosity of the spinning slurry 1 is 500-2000 cp; The mass ratio of the carbon nanotubes to the polymer binder in the spinning slurry 2 is 1:0.4-1:0.6, the mass ratio of the carbon nanotubes to the dispersing agent is 1:0.2-1:0.5, the volume ratio of ethanol to water in the solvent of the spinning slurry 2 is 1:0.3-1:1.5, the volume ratio of glycerol to ethanol is 1:3-1:12, the total solid content of the spinning slurry 2 is 12-20%, and the 25°C viscosity of the spinning slurry 2 is 500-2000 cp.

5. The method of claim 1, wherein: The technical parameters in the electrospinning process of the spinning slurry 1 in step 3) are as follows: liquid flow rate is 0.5-1 ml / h, the distance between the needle tip and the receiving plate is 15-20 cm, the voltage is 12-15 kV, and the receiving time is 2-4 h; the technical parameters in the electrospinning process of the spinning slurry 2 are as follows: liquid flow rate is 1-1.5 ml / h, the distance between the needle tip and the receiving plate is 18-25 cm, the voltage is 8-15 kV, and the receiving time is 1.5-3.5 h.

6. The method of claim 1, wherein: The calcination temperature in step 4) is 600-800 ℃, and the calcination time is 2-6 h.

7. The method of claim 1, wherein: The sputtering power of the magnetron sputtering in step 5 is 200-500 W, the sputtering time is 8-20 min, and the corresponding Pt loading amount is 0.05-0.2 mg / cm².

8. The method of claim 1, wherein: The thickness of the catalytic layer prepared in step 4) is 5-20 μm.

9. The method of claim 1, wherein: The hot-pressing temperature in step 4) is 110-140 ℃, the pressure is 0.5-2 MPa, and the hot-pressing time is 2-10 min.

10. A membrane electrode prepared according to the method of any one of claims 1 to 9, characterized by: The power density is ≥1.5 W / cm² at a voltage of 0.6 V, and the Pt loading amount is ≤0.2 mg / cm².

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