Membrane electrode and preparation method thereof, fuel cell and water electrolysis device

Abstract

The invention provides a membrane electrode and a preparation method thereof, a fuel cell and a water electrolysis device. The membrane electrode comprises an anode gas diffusion layer, a microporous layer and an anode catalyst layer which are sequentially stacked, the microporous layer is formed by interweaving titanium nitride fibers, and the average pore diameter of the microporous layer is larger than that of the anode catalyst layer and smaller than that of the anode gas diffusion layer. By utilizing the membrane electrode, the stability of the membrane electrode can be improved while the interface contact resistance of the anode catalyst layer and the anode gas diffusion layer of the membrane electrode is reduced.

Description

Technical Field

[0001] The present application relates to the field of batteries, and particularly to a membrane electrode, a preparation method thereof, a fuel cell, and a water electrolysis device. Background Art

[0002] Hydrogen energy will play a crucial role in the fields of transportation, power generation, chemical industry, and building heating. Among many water electrolysis hydrogen production technologies, the proton exchange membrane water electrolyzer (PEMWE) has attracted wide attention from the scientific and industrial communities due to its advantages such as strong variable load capacity, high hydrogen production purity, and fast response speed. The membrane electrode is an important component of PEMWE, and the anode gas diffusion layer (porous transport layers, PTL) and the anode catalyst layer are indispensable important components in the membrane electrode. Among them, the anode gas diffusion layer plays a role in conducting electrons, transporting water molecules to the anode, and transporting oxygen outwards. The titanium-based porous material is the best anode gas diffusion layer material confirmed by screening. Due to the limitation of the processing technology of the Ti-based porous material, the surface roughness is relatively high (up to 400 μm), resulting in a relatively high interfacial contact resistance between the anode catalyst layer (catalyst layer, CL) and the anode gas diffusion layer, thereby limiting the improvement of the electrolysis efficiency of PEMWE. By setting a microporous layer between the anode catalyst layer and the anode gas diffusion layer, the contact resistance between the anode catalyst layer and the anode gas diffusion layer can be reduced to a certain extent. However, in view of the high potential and highly acidic environment of the anode of the proton exchange membrane water electrolyzer, the current microporous layer materials are prone to decomposition or side reactions under the above conditions, thereby reducing the stability of the membrane electrode and the electrolysis efficiency. Summary of the Invention

[0003] The present application provides a membrane electrode, a preparation method thereof, a fuel cell, and a water electrolysis device, so as to reduce the interfacial contact resistance between the anode catalyst layer and the anode gas diffusion layer of the membrane electrode while improving the stability of the membrane electrode.

[0004] In a first aspect, the present application provides a membrane electrode, which includes an anode gas diffusion layer, a microporous layer, and an anode catalyst layer that are sequentially stacked. The microporous layer is a microporous layer formed by the interweaving of titanium nitride fibers. The average pore diameter of the microporous layer is larger than the average pore diameter of the anode catalyst layer and smaller than the average pore diameter of the anode gas diffusion layer.

[0005] The membrane electrode of the present application, the microporous layer arranged between the anode gas diffusion layer and the anode catalyst layer is a microporous layer formed by titanium nitride fibers. The average pore size of the microporous layer is between the average pore size of the anode catalyst layer and the average pore size of the anode gas diffusion layer. Compared with the structure in which the anode catalyst layer is in direct contact with the anode gas diffusion layer, the interface bonding degree between the microporous layer and the anode gas diffusion layer and the interface bonding degree between the microporous layer and the anode catalyst layer are higher, thereby, the interface contact resistance between the anode gas diffusion layer, the microporous layer and the anode catalyst layer will be reduced. Compared with the traditional anode catalyst layer and the anode gas diffusion layer in direct contact structure, the interface contact resistance between the layers can be reduced, thereby, the microporous layer can be used as a connecting bridge between the anode gas diffusion layer and the anode catalyst layer, reducing the contact resistance between the anode catalyst layer and the anode gas diffusion layer, thereby improving the reaction efficiency of the fuel cell and the electrolysis efficiency of the water electrolysis device. At the same time, the microporous layer is formed by titanium nitride fibers. Since titanium nitride fibers have excellent electrical conductivity, rapid conduction of electrons can be achieved and electron transmission impedance can be reduced. In addition, since titanium nitride nanofibers can still maintain high stability under high potential and high acid conditions, they can improve the stability of membrane electrodes when used in membrane electrodes.

[0006] In one implementation, the average pore size of the microporous layer is 2 to 6 times the average pore size of the anode catalyst layer. When the average pore size of the microporous layer is 2 to 6 times the average pore size of the anode catalyst layer, the interface bonding between the microporous layer and the anode catalyst layer will be higher, which is more conducive to reducing the interface resistance between the anode catalyst layer and the microporous layer.

[0007] In one implementation, the average pore size of the anode gas diffusion layer is 500 to 1000 times the average pore size of the microporous layer. When the average pore size of the anode gas diffusion layer is 500 to 1000 times the average pore size of the microporous layer, a better interface contact can be formed between the anode gas diffusion layer and the microporous layer, further reducing the interface resistance between the anode gas diffusion layer and the microporous layer.

[0008] In one implementation, the average pore size of the microporous layer gradually decreases or decreases in steps from the anode gas diffusion layer to the anode catalyst layer. The microporous layer has a larger average pore size on the side facing the anode gas diffusion layer, which is conducive to forming a good contact interface with the anode gas diffusion layer. The microporous layer has a smaller average pore size on the side facing the anode catalyst layer, which is conducive to forming a better interface contact with the anode catalyst layer.

[0009] In one implementation, the porosity of the microporous layer is 40% - 50%. In addition to having good electrical conductivity, the microporous layer also needs to have good air permeability so that gas can freely shuttle on both sides of the membrane electrode. The porosity of the microporous layer of the present application is greater than 40%, which can help improve the gas permeability of the membrane electrode, and thus help improve the reaction efficiency of the fuel cell or the electrolysis efficiency of the water electrolysis device. The porosity of the microporous layer is less than or equal to 50%, which is beneficial to balance the porosity and electrical conductivity of the microporous layer, so that the microporous layer has high electron conductivity while having a high porosity.

[0010] In one implementation, the electron conductivity of the microporous layer is 1000 ± 300 S / cm. The microporous membrane with this electron conductivity can help improve the electron conduction rate, and thus improve the reaction efficiency of the fuel cell or the electrolysis efficiency of the water electrolysis device.

[0011] In one implementation, in the microporous layer, the diameter of the titanium nitride fiber is 100 - 1500 nm. The titanium nitride fiber with this diameter can help improve the electron conductivity. In one implementation, the thickness of the microporous layer is 10 - 1000 μm. If the thickness of the microporous membrane is too high, it will affect the transmission of gas and electrons.

[0012] In a second aspect, the present application provides a method for preparing a membrane electrode. The preparation method includes: providing a precursor solution, the precursor solution includes a titanium-containing organic compound, and using an electrospinning process to spin the precursor solution to obtain a fiber spinning film, and the fiber spinning film is obtained through decarbonization and nitridation treatments to obtain the microporous layer; using the microporous membrane as the microporous layer and assembling it with the anode gas diffusion layer and the anode catalyst layer to obtain the membrane electrode.

[0013] The membrane electrode with the same performance as the first aspect of the present application can be obtained by using the preparation method of the present application. Among them, the microporous layer prepared by the electrospinning process can obtain titanium nitride fibers with uniform and consistent diameters, and the continuity of the titanium nitride fibers is high, so that the obtained microporous layer can be flatter, and the strength can meet the requirements of individual assembly.

[0014] In one implementation, the decarbonization treatment includes at least one cycle treatment process. One cycle treatment process includes: placing the fiber spinning film in a tube furnace, under an oxygen atmosphere, heating to 550 - 650 °C and holding for 10 - 14 h, then evacuating and maintaining under vacuum for 3 - 8 min, and then introducing ammonia gas and holding for 1 - 5 min. The above process can be repeated 3 - 5 times. Through the decarbonization treatment, the stability of the microporous layer can be improved, preventing it from decomposing in the process of use due to a high potential and highly acidic environment.

[0015] In one implementation, the nitridation treatment includes: placing the fiber spinning film in a nitrogen environment and calcining it.

[0016] In one implementation, in the nitridation treatment, the fiber spinning film is fixed with a quartz splint having a porous structure and then calcined. Fixing the fiber spinning film with a quartz splint having a porous structure can improve the flatness of the microporous layer, and further improve the bonding degree between the microporous layer and the anode gas diffusion layer and the anode catalyst layer.

[0017] In a third aspect, the present application provides a fuel cell, which includes a bipolar plate and the membrane electrode of the first aspect of the present application, and the membrane electrode is disposed between the two bipolar plates.

[0018] In a fourth aspect, the present application provides a water electrolysis device, which includes the membrane electrode of the first aspect of the present application.

[0019] The technical effects that can be achieved in the above third aspect to the fourth aspect can be referred to the corresponding effect descriptions in the above first aspect, and will not be repeated here.

[0020] Among them, for the data in the above various possible implementation manners of the present application, such as the diameter of the nanofibers, the pore diameter of the pores, and the thickness of the microporous membrane, etc., when measuring, the values within the range of engineering measurement errors should be understood as being within the scope defined by the present application. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of the membrane electrode provided by the embodiment of the present application;

[0022] Figure 2 It is a SEM image of the microporous membrane of Example 1;

[0023] Figure 3 It is an XRD diagram of the microporous membrane of Example 1;

[0024] Figure 4 It is a SEM image of the microporous membrane of Example 3;

[0025] Figure 5 It is a schematic structural diagram of a quartz splint;

[0026] Figure 6 It is a change comparison diagram of the total resistance of membrane electrodes with different structural compositions;

[0027] Figure 7 It is an electrolysis voltage comparison diagram of the membrane electrodes of Example 6 and Comparative Example 9 assembled into a PEMWE test system;

[0028] Figure 8 It is a schematic diagram of the application scenarios of a water electrolysis device and a fuel cell.

[0029] Reference numerals:

[0030] 11 - Proton exchange membrane; 12 - Anode catalyst layer; 13 - Microporous layer; 14 - Anode gas diffusion layer; 15 - Cathode catalyst layer; 16 - Cathode gas diffusion layer; 21 - Quartz splint; 211 - First plate body; 212 - Second plate body. Detailed implementation manners

[0031] In order to make the objectives, technical solutions and advantages of this application clearer, the following will further describe this application in detail with reference to the accompanying drawings.

[0032] The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to limit this application. As used in the specification and appended claims of this application, the singular forms "a", "an", "above-mentioned", "the" and "this" are also intended to include expressions such as "one or more", unless clearly indicated to the contrary in the context.

[0033] Reference to "one embodiment" or "some embodiments" etc. described in this specification means that specific features, structures or characteristics described in connection with that embodiment are included in one or more embodiments of this application. Thus, statements such as "in one embodiment", "in some embodiments", "in other some embodiments", "in still other embodiments" etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "include", "comprise", "have" and their variants all mean "include but not limited to", unless otherwise specifically emphasized in other ways.

[0034] In hydrogen production technology, proton exchange membrane water electrolyzers are widely used due to advantages such as strong variable load capacity, high hydrogen production purity, and fast response speed. In a water electrolyzer, the membrane electrode is a core component. The membrane electrode usually includes a proton exchange membrane, with an anode catalyst layer and an anode gas diffusion layer provided on one side of the proton exchange membrane, and a cathode catalyst layer and a cathode gas diffusion layer provided on the other side.

[0035] Figure 1 It is a schematic structural diagram of a membrane electrode. As Figure 1As shown in the figure, the membrane electrode of the embodiment of the present application includes a proton exchange membrane 11. On one side of the proton exchange membrane 11, an anode catalyst layer 12, a microporous layer 13, and an anode gas diffusion layer 14 are sequentially provided. The proton exchange membrane 11, the anode catalyst layer 12, the microporous layer 13, and the anode gas diffusion layer 14 are sequentially stacked. The microporous layer 13 is placed between the anode gas diffusion layer 14 and the anode catalyst layer 12. Among them, on the other side of the proton exchange membrane 11, a cathode catalyst layer 15 and a cathode gas diffusion layer 16 are also provided. During the process of electrolyzing water, the proton exchange membrane 11 enables the current to directly act on water molecules and decomposes the water molecules into hydrogen ions and oxygen ions. The oxygen ions are oxidized on the anode side to produce oxygen. The generated oxygen is exported from the gas flow field of the anode end plate after passing through the anode catalyst layer 12, the microporous layer 13, and the anode gas diffusion layer 14. The hydrogen ions are reduced to generate hydrogen, which is exported from the gas flow field of the cathode end plate after passing through the cathode catalyst layer 15 and the cathode gas diffusion layer 16. Among them, a microporous layer can also be provided between the cathode catalyst layer 15 and the cathode gas diffusion layer 16.

[0036] In the membrane electrode of the present application, by arranging the microporous layer 13 between the anode catalyst layer 12 and the anode gas diffusion layer 14, the contact resistance can be reduced and the electrolysis efficiency can be improved. The following will focus on the structures of the anode catalyst layer 12, the microporous layer 13, and the anode gas diffusion layer 14 in combination with Figure 1 make a key description.

[0037] As Figure 1 shown, the anode catalyst in the anode catalyst layer 12 is IrO 2 , with a perfluorosulfonic acid resin layer as the matrix layer. The catalyst loading is 0.25 - 0.45 mg / cm 2 . The anode catalyst layer 12 can promote the oxidation reaction on the anode side. The anode catalyst layer 12 is a porous structure, and gas can shuttle through the anode catalyst layer. The porosity of the anode catalyst layer 12 is 30 - 40%, the pore diameter is 40 - 80 nm, and the thickness is 1 - 15 μm.

[0038] The anode gas diffusion layer 14 is a titanium felt, which is a porous structure layer. The thickness of the anode gas diffusion layer 14 is 1 - 2 mm, the porosity is 30 - 35%, and the pore diameter is 16 - 144 μm. The anode gas diffusion layer can be a titanium felt, and the particle size of the titanium particles in the titanium felt is 30 - 200 μm.

[0039] Continue to refer to Figure 1, the microporous layer 13 is a microporous layer formed by the interweaving of titanium nitride fibers. Among them, the microporous layer 13 is a porous structure layer. The thickness of the microporous layer 13 can be 10 - 1000 μm, for example, 10 - 500 μm, or for another example, it can be 100 - 300 μm. Exemplarily, the thickness of the microporous layer 13 can be, for example, 10 μm, 30 μm, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm or 1000 μm or any value between any two of the above values.

[0040] The porosity of the microporous layer 13 is 40% - 50%. Exemplarily, the porosity of the microporous layer 13 can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49% or 50% or any value between any two of the above values.

[0041] The electronic conductivity of the microporous layer 13 is 1000 ± 300 S / cm. Exemplarily, the electronic conductivity of the microporous layer 13 can be 700 S / cm, 750 S / cm, 800 S / cm, 850 S / cm, 900 S / cm, 950 S / cm, 1000 S / cm, 1050 S / cm, 1100 S / cm, 1150 S / cm, 1200 S / cm, 1300 S / cm or any value between any two of the above values.

[0042] In the microporous layer 13, the diameter of the titanium nitride fibers can be 100 - 1500 nm, for example, 100 - 1000 nm, or for another example, it can be 300 - 1000 nm. Exemplarily, the minimum diameter of the titanium nitride fibers in the microporous layer can be 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm or 500 nm, etc., and the maximum value of the titanium nitride fibers can be 1500 nm, 1400 nm, 1300 nm, 1200 nm, 1100 nm or 1000 nm, etc.

[0043] In the membrane electrode of the embodiment of the present application, the average pore size of the microporous layer 13 is larger than the average pore size of the anode catalyst layer 12 and smaller than the average pore size of the anode gas diffusion layer 14. Exemplarily, the pore size of the microporous layer 13 can be 80 - 500 nm, such as 80 nm, 100 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 300 nm, 350 nm, 400 nm or 500 nm, etc. Among them, the average pore size of the microporous layer 13 can be 2 - 6 times the average pore size of the anode catalyst layer 12. At the same time, the average pore size of the anode gas diffusion layer 14 can be 500 - 1000 times the average pore size of the microporous layer 13. In an alternative embodiment, from the anode gas diffusion layer 14 to the anode catalyst layer 12 direction, the average pore size of the microporous layer 13 gradually decreases or decreases step by step. The average pore size of the microporous layer 13 is between the anode gas diffusion layer 14 and the anode catalyst layer 12, which can serve as a connecting bridge between the two, increasing the interface area of the connection and reducing the interface resistance.

[0044] The above explains the structure of the membrane electrode. The following will explain the preparation method of the membrane electrode. The preparation method of the membrane electrode of the embodiment of the present application includes the following steps:

[0045] S1. Provide a precursor solution, the precursor solution includes a titanium-containing organic compound, and use the electrospinning process to spin the precursor solution to obtain a fiber spinning film, and the fiber spinning film is obtained through decarbonization and nitridation treatments to obtain the microporous membrane;

[0046] S2. Use the microporous membrane as the microporous layer, and assemble it with the anode gas diffusion layer and the anode catalyst layer to obtain the membrane electrode.

[0047] Among them, the decarbonization treatment in step S1 includes at least one cycle treatment process. One cycle treatment process can include the following steps: Place the fiber spinning film in a tubular furnace, under an oxygen atmosphere, heat it to 550 - 650 °C and keep it warm for 10 - 14 h, then evacuate and keep it under vacuum for 3 - 8 min, and then introduce ammonia gas and keep it for 1 - 5 min. It can be repeated 3 to 5 times. Through the above decarbonization treatment, the carbon in the fiber spinning film can be effectively removed, so as to obtain a high-purity titanium nitride fiber film subsequently.

[0048] In step S1, the nitridation treatment includes: placing the fiber spinning film in a nitrogen environment and performing calcination. The calcination treatment process of an embodiment includes: keeping the ammonia flow rate into the tubular furnace unchanged (60 - 150 mL / min), setting the heating rate of the tubular furnace to 0.5 - 2 °C / min, heating to 850 - 950 °C and maintaining for 8 - 12 h, and then cooling at a rate of 0.5 - 2 °C / min to room temperature to obtain a microporous membrane. The fiber spinning film obtained by electrospinning is a titanium organic compound fiber film, and through nitridation treatment, a titanium nitride fiber film can be obtained.

[0049] To improve the flatness of the surface of the microporous membrane, during the nitridation treatment, the fiber spinning film can be fixed with a quartz splint with a porous structure before calcination. Fixing the fiber spinning film with a quartz splint with a porous structure can prevent it from deforming such as warping during the calcination process, thereby improving the flatness of its surface.

[0050] Hereinafter, the structure and performance of the membrane electrode of the present application will be explained based on examples and comparative examples.

[0051] Example 1

[0052] This example is a microporous membrane, which is prepared by an electrospinning process. It specifically includes the following steps:

[0053] Step S11: Add 3 g of tetrabutyl titanate, 4.2 g of acetic acid, 0.9 g of PVP, and 9.5 g of ethanol into a 20 mL container, and stir until completely dissolved to obtain a precursor solution;

[0054] Step S12: Cover a layer of aluminum foil on the electrospinning roller to receive the precursor fiber carrier, use a polytetrafluoroethylene syringe to suck 5 mL of the precursor solution and place it in the pusher of the electrospinning machine to perform electrospinning to form a precursor nanofiber mat, and collect the precursor nanofiber mat on the aluminum foil. The electric field strength during the electrospinning process is 12 kV, the slurry propulsion speed is 0.45 mL / h, the roller receiving speed is 100 rpm, and the needle translation speed is 300 mm / min.

[0055] Step S13: After the spinning is completed, remove the precursor nanofiber mat from the aluminum foil, place it in a quartz clamping plate with a porous structure, and transfer it to a tube furnace connected to a vacuum pump and ammonia gas. First, introduce oxygen into the tube furnace and maintain the oxygen flow rate at 100 mL / min. Set the heating rate of the tube furnace to 3 °C / min, heat it to 600 °C and hold for 12 hours. Then, vacuum-treat the tube furnace with the vacuum pump for 5 minutes, then turn off the vacuum pump, and then introduce ammonia gas for 2 minutes. Repeat this three times. Keep the ammonia gas flow rate into the tube furnace unchanged (100 mL / min), set the heating rate of the tube furnace to 1 °C / min, heat it to 900 °C and maintain for 10 h, and then cool it down to room temperature at a rate of 1 °C / min to obtain a microporous membrane. Figure 2 It is a schematic structural diagram of a quartz clamping plate. As Figure 2 shown, the quartz clamping plate 21 includes a first plate body 211 and a second plate body 212, and the fiber mat is placed between the first plate body 211 and the second plate body 212. The gap after the first plate body 211 and the second plate body 212 are covered is 50 - 300 μm, which is used to control the flatness of the microporous membrane. Among them, grooves can be provided on the surface of the first plate body 211, and protrusions cooperating with the grooves can be provided on the surface of the second plate body 212. The fiber mat after electrospinning can be placed in the grooves of the first plate body.

[0056] The thickness of the microporous membrane is 110 ± 5 μm. The electronic conductivity of the microporous membrane is measured by the four-terminal method, and the electronic conductivity of the microporous membrane is 736.2 S / cm.

[0057] Figure 3 It is an SEM image of the microporous membrane of this embodiment. After measurement, in the microporous membrane, the diameter range of titanium nitride fibers is 150 - 250 nm, and the pore diameter between titanium nitride fibers is 300 - 800 nm. Figure 4 It is an XRD diagram of the microporous membrane of this embodiment. As Figure 4 shown, by comparing with the standard picture of TiN, it can be known that the diffraction characteristics of the microporous membrane in the embodiment of the present application are the same as the characteristic diffraction peaks of TiN, and there are no other obvious characteristic peaks in the XRD diagram. It shows that the main component in the microporous membrane of the embodiment of the present application is TiN.

[0058] Test the stability of the microporous membrane. Test the stability of the microporous membrane in high-temperature, highly acidic environments, and high-voltage environments. The standard test system consists of a platinum sheet as the working electrode, with a titanium nitride powder layer placed on the surface of the platinum sheet. The titanium nitride powder layer and the platinum sheet are pre-compacted with a pressing plate, and a porous PTFE layer is provided on the surface of the titanium nitride powder layer to ensure that the electrolyte infiltrates the titanium nitride powder while preventing the powder from entering the sulfuric acid solution on the right side; the counter electrode is a platinum sheet electrode; the reference electrode is a silver-silver chloride electrode. The test system composition of the test example: Compared with the standard test system, the microporous membrane implemented in this application is used to replace the titanium nitride powder layer in the standard test system, and the others are the same as the standard test system composition.

[0059] The test method is to apply a voltage of 2V to the working electrodes of the standard test system and the test example test system respectively at 90 °C and pH values of 0, 4, and 7. RHE After two hours, the titanium ion content in the electrolyte is characterized by ICP, and the results are shown in Table 1.

[0060] Table 1

[0061]

[0062] As shown in Table 1, titanium nitride exhibits extremely high stability at a voltage of 2V RHE, especially with basically no degradation under the conditions of pH 4 - 7.

[0063] Example 2

[0064] This example is a microporous membrane. Compared with Example 1, the difference in the preparation method of the microporous membrane in this example is:

[0065] 1) The components of the precursor solution are different. The composition of the precursor solution in Example 2 is: 1 g of tetrabutyl titanate, 0.6 g of PVP, and 5.5 g of isopropanol.

[0066] 2) The electrospinning parameters are different. The electric field strength of electrospinning in Example 2 is 23 kV, and the slurry feeding speed is 1 mL / h.

[0067] The rest of the preparation process is the same as that in Example 1.

[0068] Figure 5 This is the SEM image of the microporous membrane of this example. After testing, the fiber diameter ranges from 900 - 1100 nm, and the pore diameter between fibers is 300 - 1000 nm.

[0069] The microporous membrane of Example 1 was disposed between the anode catalyst layer and the anode gas diffusion layer, and the total resistance of the anode catalyst layer was measured. Among them, R1 is the total resistance of the anode catalyst layer and the anode gas diffusion layer. R2 is the total resistance of the anode catalyst layer, the microporous membrane and the anode gas diffusion layer. Among them, the thickness of the anode catalyst layer is 10 μm, the thickness of the microporous membrane is 185 μm, and the thickness of the anode gas diffusion layer is 250 μm.

[0070] Figure 6 It is a comparison chart of the change in the total resistance. As Figure 6 shown, the total resistance R1 of the anode catalyst layer and the anode gas diffusion layer is 11.3 mΩ·cm 2 The total resistance R2 of the anode catalyst layer, the microporous membrane and the anode gas diffusion layer is 2.2 mΩ·cm 2 . By introducing a microporous membrane between the anode catalyst layer and the anode gas diffusion layer, the total resistance can be significantly reduced. This shows that the microporous membrane can significantly reduce the contact resistance between the anode catalyst layer and the anode gas diffusion layer.

[0071] Comparative Example 1

[0072] The microporous membrane of this comparative example was prepared by electrospinning, and specifically included the following steps: commercially available TiN nanoparticles with an average particle diameter of 20 nm were selected, and they were added to a mixed solvent of isopropanol and water with a volume ratio of 1:1 at a mass ratio of 2:1 with the polymer polyvinylpyrrolidone (PVP) to form a slurry, and it was ensured that the mass fraction of PVP in the slurry was always 8 wt%. Subsequently, the conductive binder poly(3,4-ethylenedioxythiophene) (PEDOT) was added to the above slurry, and it was ensured that the volume ratio of PEDOT to TiN was 3:7. Subsequently, fibers were obtained by electrospinning. Then the fibers were soaked in deionized water for 24 hours to remove all PVP, thereby obtaining TiN / PEDOT fibers. The average diameter of the TiN / PEDOT fibers is 0.5 - 1.0 μm, and the particle distribution of TiN is uneven, so the contact resistance between particles is relatively high. The conductivity of the obtained TiN / PEDOT fibers is 1.7 S / cm.

[0073] Comparative Example 2

[0074] This comparative example is a microporous membrane, which was prepared by an electrospinning process. Specifically, it includes the following steps:

[0075] Step S11: Add 3 g of tetrabutyl titanate, 4.2 g of acetic acid, 0.9 g of PVP and 9.5 g of ethanol to a 20 mL container, and stir until completely dissolved to obtain a precursor solution;

[0076] Step S12: Cover a layer of aluminum foil on the electrospinning roller to receive the precursor fiber carrier. Use a polytetrafluoroethylene syringe to suck 5 mL of the precursor solution and place it in the pusher of the electrospinning machine to perform electrospinning to form a precursor nanofiber mat, and collect the precursor nanofiber mat on the aluminum foil. The electric field strength during electrospinning is 12 kV / cm, the slurry propulsion speed is 0.45 mL / h, the roller receiving speed is 100 rpm, and the needle translation speed is 300 mm / min.

[0077] Step S13: After spinning is completed, peel off the precursor nanofiber mat from the aluminum foil, put it into a quartz splint and transfer it to a tubular furnace connected to a vacuum pump and ammonia gas. Keep the ammonia gas flow rate into the tubular furnace unchanged (100 mL / min), set the heating rate of the tubular furnace to 1 °C / min, heat up to 900 °C and maintain for 10 h, and then cool down at a rate of 1 °C / min to room temperature to obtain a microporous membrane.

[0078] Comparative Example 3

[0079] This comparative example is a kind of porous membrane, and this microporous membrane uses a titanium mesh as a substrate and is obtained by physical vapor deposition technology. The specific steps are as follows:

[0080] Insert a titanium mesh with a pore size distribution of 2 - 3 mm and a thickness of 1 mm into the vacuum chamber of the physical vapor deposition equipment. Use a vacuum pump to reduce the pressure to 1×10 -4 Pa. Use 99.995% Ti target as the sputtering source, and keep the target-substrate distance at about 60 mm. Argon gas and nitrogen gas (99.99% purity) are introduced as sputtering and reaction gases. During the deposition process, the argon gas flow rate, nitrogen gas flow rate and sputtering current are 30 sccm, 2 sccm and 0.4 A respectively. Keep the sputtering chamber pressure at 1.1 Pa, the sputtering temperature at 350 °C, and the sputtering time at 15 min. Thus, a microporous membrane with an inner layer of Ti and an outer layer of TiN is obtained. The pore size of the microporous membrane is 2 - 3 mm.

[0081] Comparative Example 4

[0082] This comparative example is a kind of microporous membrane, and this microporous membrane uses the microporous membrane prepared in Example 3 as a substrate and is obtained by physical vapor deposition technology. Its vapor deposition operation is the same as that of Comparative Example 3, except that the sputtering time is 60 min. The inner layer and outer layer of this microporous membrane are both TiN. The pore size of this microporous membrane is 20 - 50 nm.

[0083] Example 3

[0084] Use the microporous membrane of Example 1 to assemble a membrane electrode. The specific assembly method is as follows:

[0085] S21. Cut a 20×20 mm DuPont Nafion 115 proton exchange membrane, and soak it successively in 5% H 2 O 2 solution, 0.5 M H 2 SO 4 solution, and deionized water at 80 °C for 1 hour. Then soak the membrane in deionized water for standby. Before use, dry the proton exchange membrane and it can be used. The active area is 5×5 mm;

[0086] S22. Uniformly disperse the dispersion of 60% Pt / C and 5% Nafion cathode catalyst in isopropanol. Spray the cathode catalyst slurry onto one side of the membrane (within the effective area corresponding to the 5×5 mm cathode effective area) by ultrasonic spraying equipment, so that the Pt loading is 0.17 mg / cm2, and the dry Nafion mass is 25% of the mass of the 60% Pt / C catalyst;

[0087] S23. Uniformly disperse the dispersion of IrO 2 and 5% Nafion in isopropanol to form an anode catalyst slurry. Spray the anode catalyst slurry onto the other side of the membrane (the position overlapping with the cathode effective area) by ultrasonic spraying equipment, so that the IrO 2 loading is 0.35 mg / cm 2 , and the dry Nafion mass is 25% of the mass of the IrO 2 catalyst;

[0088] S24. Cut 1 piece of 5×5 mm microporous membrane of Example 1 as the microporous layer, place it within the effective area of the anode catalyst layer, and stack the sintered titanium felt of the same area on the outside of the microporous layer; stack the carbon paper in the same way within the cathode effective area; obtain the membrane electrode.

[0089] Example 4

[0090] Assemble the membrane electrode using the microporous membrane of Example 2. The specific assembly method is the same as that of Example 4.

[0091] Comparative Example 5

[0092] Assemble the membrane electrode using the microporous membrane of Comparative Example 1. The specific assembly method is the same as that of Example 4.

[0093] Comparative Example 6

[0094] Assemble the membrane electrode using the microporous membrane of Comparative Example 2. The specific assembly method is the same as that of Example 4.

[0095] Comparative Example 7

[0096] Assemble the membrane electrode using the microporous membrane of Comparative Example 3. The specific assembly method is the same as that of Example 4.

[0097] Comparative Example 8

[0098] A membrane electrode was assembled using the microporous membrane of Comparative Example 4, and the specific assembly method was the same as that of Example 4.

[0099] Comparative Example 9

[0100] This comparative example is a membrane electrode, which is different from that of Example 4 in that the microporous layer is not included in the membrane electrode, and only the anode catalyst layer and the anode gas diffusion layer are included.

[0101] The membrane electrodes of different examples and Comparative Example 1 were respectively assembled into a PEMWE test system for polarization performance testing, keeping the water flow rate at 100 ml / min and the temperature at 80 °C. At a current density of 1.0 A / cm 2 , the electrolysis voltages corresponding to each example and comparative example were tested. And the change value of the voltage per unit time at this current density was tested to evaluate the stability of the membrane electrodes of each example and comparative example. The test results are listed in Table 2.

[0102] Table 2

[0103]

[0104]

[0105] From the test data in Table 2, it can be seen that the electrolysis voltages corresponding to the membrane electrodes of Examples 3-4 of this application are all lower than those of Comparative Examples 5 and 7-9, indicating that the membrane electrodes of this application can effectively improve the electrolysis efficiency of the water electrolysis device. According to the data of Example 3 and Comparative Example 5, when titanium nitride is in particulate form, the purpose of effectively improving the conductivity of the microporous membrane cannot be achieved. According to the comparison data of Example 3 and Comparative Example 6, when the titanium nitride fiber contains carbon elements, during the electrolysis process, carbon will undergo a decomposition reaction at high potentials. Therefore, the stability of the membrane electrode is poor, the voltage increase per unit time is high, and the service life of the membrane electrode is shortened. According to the comparison data of Example 3 and Comparative Example 7, when the pore size of the microporous layer is too large and does not match the anode gas diffusion layer and the anode catalyst layer, the role of the microporous layer is not obvious, and due to the additional increase in the interfacial resistance and the bulk resistance, the electrolysis efficiency decreases. According to the comparison data of Example 3 and Comparative Example 8, when the pore size of the microporous layer is too small, the electrolysis voltage is high. The possible reason is that the microporous layer is too dense, which affects the diffusion of reactants and products to both sides of the electrode, causing mass transfer polarization to appear earlier. Figure 7 It is a comparison diagram of the electrolysis voltages of the membrane electrodes of Example 3 and Comparative Example 9 assembled into a PEMWE test system. As Figure 7 shown, at 1.0 A / cm 2Under the current density, the electrolysis voltage of the membrane electrode of Example 3 is more than 60 mV lower than that of the membrane electrode of Comparative Example 9. This shows that under the same conditions, introducing a microporous layer into the membrane electrode is beneficial to improving the electrolysis efficiency.

[0106] The membrane electrode of the present application can be used in water electrolysis devices and fuel cells. When the membrane electrode of the embodiment of the present application is used in a water electrolysis device, the electrolysis efficiency of the water electrolysis device can be improved. When the membrane electrode of the embodiment of the present application is used in a fuel cell, the reaction efficiency of the fuel cell can be improved. Therefore, for the same inventive purpose, the embodiment of the present application also provides a water electrolysis device. The water electrolysis device includes the membrane electrode of the embodiment of the present application. Similarly, the embodiment of the present application also provides a fuel cell, and the fuel cell includes the membrane electrode of the embodiment of the present application.

[0107] Figure 8 It is a schematic diagram of the application scenarios of a water electrolysis device and a fuel cell. As Figure 8 shown, the water electrolysis device and the fuel cell can be used in 5G base stations and data center systems. The energy consumption of 5G base stations and data centers is increasing year by year, which has a very large impact on the power system, and high energy consumption may also be one of the constraints for their popularization. The water electrolysis device of the present application can greatly improve the hydrogen production efficiency. The hydrogen energy prepared by the water electrolysis device can be transported to an energy storage power station to provide raw materials for the fuel cells of the energy storage power station. This method can reduce the cost of large-scale energy storage and improve the safety of energy storage. As a key material of the fuel cell, it can generate electricity on-site in combination with hydrogen production technology. By efficiently utilizing renewable resources, the operation and maintenance costs of 5G base stations and data centers can be reduced.

[0108] The above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present application, and all should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A membrane electrode, characterized in that, it comprises an anode gas diffusion layer, a microporous layer and an anode catalyst layer which are sequentially stacked, the microporous layer is a microporous layer formed by the interweaving of titanium nitride fibers, and the average pore diameter of the microporous layer is larger than the average pore diameter of the anode catalyst layer and smaller than the average pore diameter of the anode gas diffusion layer.

2. The membrane electrode according to claim 1, characterized in that, the average pore diameter of the microporous layer is 2 to 6 times the average pore diameter of the anode catalyst layer.

3. The membrane electrode according to claim 1 or 2, characterized in that, the average pore diameter of the anode gas diffusion layer is 500 to 1000 times the average pore diameter of the microporous layer.

4. The membrane electrode according to any one of claims 1-3, characterized in that, from the anode gas diffusion layer to the anode catalyst layer direction, the average pore diameter of the microporous layer gradually decreases or decreases step by step.

5. The membrane electrode according to any one of claims 1-4, characterized in that, the porosity of the microporous layer is 40% to 50%.

6. The membrane electrode according to any one of claims 1-5, characterized in that, in the microporous layer, the diameter of the titanium nitride fibers is 100 to 1500 nm.

7. The membrane electrode according to any one of claims 1-6, characterized in that, the electronic conductivity of the microporous layer is 1000 ± 300 S / cm.

8. The membrane electrode according to any one of claims 1-7, characterized in that, the thickness of the microporous layer is 10 to 1000 μm.

9. A method for preparing the membrane electrode according to any one of claims 1-8, characterized in that, it includes: providing a precursor solution, the precursor solution includes a titanium-containing organic compound, and using the electrospinning process to spin the precursor solution to obtain a fiber spinning film, and the fiber spinning film is obtained by carbon removal and nitridation treatment to obtain the microporous membrane; using the microporous membrane as the microporous layer and assembling it with the anode gas diffusion layer and the anode catalyst layer to obtain the membrane electrode.

10. The preparation method according to claim 9, characterized in that, the carbon removal treatment includes at least one cycle treatment process, and the one cycle treatment process includes: placing the fiber spinning film in a tube furnace, under an oxygen atmosphere, heating to 550-650 °C and holding for 10-14 h, then evacuating and maintaining under vacuum for 3-8 min, and then introducing ammonia gas and holding for 1-5 min.

11. The preparation method according to claim 9 or 10, characterized in that, the nitridation treatment includes: placing the fiber spinning film in a nitrogen environment and calcining it.

12. The preparation method according to any one of claims 9-11, characterized in that, in the nitridation treatment, the fiber spinning film is fixed by a quartz splint with a porous structure and then calcined.

13. A fuel cell, characterized in that, it includes a bipolar plate and the membrane electrode according to any one of claims 1-8, and the membrane electrode is arranged between the two bipolar plates.

14. A water electrolysis device, characterized in that, it includes the membrane electrode according to any one of claims 1-8.

Images