A PEM water electrolysis anode diffusion layer and preparation method thereof

Abstract

The invention provides a PEM water electrolysis anode diffusion layer and a preparation method thereof, and relates to the technical field of PEM water electrolysis. The anode diffusion layer comprises a porous layer and a microporous layer. The porous layer is a titanium dioxide nanofiber support layer, which is prepared by hot pressing and calcining at least two layers of titanium nanofiber layers. The surface of the titanium dioxide nanofiber support layer is prepared with a microporous layer, and the microporous layer comprises platinum black, spherical dehydrogenated titanium powder and a binder. The titanium nanofibers are placed on a hot press in batches for hot pressing, and the mass of the titanium nanofibers added each time gradually increases. The anode diffusion layer of the invention has strong support and toughness, high porosity and uniform pore distribution, and improves the water-gas transmission capacity during water electrolysis operation. PTFE is added to the porous layer, which improves hydrophobicity and is conducive to the conduction of water and gas. The dehydrogenated titanium powder is added to the microporous layer to improve the conductivity of the diffusion layer. The addition of platinum black promotes the progress of the water electrolysis reaction, so that the electrochemical performance of the membrane electrode is significantly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of PEM water electrolysis, and in particular relates to a PEM water electrolysis anode diffusion layer and a preparation method thereof. Background Art

[0002] As the domestic work on green environmental protection continues to deepen, hydrogen energy has great potential as an ideal clean energy in the future, and the demand for hydrogen will continue to increase. PEM water electrolysis technology can use the excess electricity of renewable energy such as wind and light to electrolyze hydrogen, while alleviating the pressure on the power grid. PEM water electrolysis hydrogen production has many advantages. In the hydrogen production process, only water is required as a raw material, the product hydrogen and oxygen are of high purity, and the hydrogen and oxygen interpenetration is slight. The electrolysis process is efficient, safe, non-toxic and harmless, and the equipment structure is compact, which can realize on-site hydrogen production.

[0003] At present, due to the characteristics of PEM water electrolysis itself, the anode diffusion layer is usually used independently as one of the components of the electrolytic cell. It plays the role of conducting electricity, separating water flow and bubbles, and supporting in the PEM water electrolytic cell. Therefore, the mechanical properties, conductivity, chemical stability, and cost of the anode diffusion layer material are very high. Its cost accounts for a large part of the various components of the PEM stack. Research on low-cost, high chemical stability, and high conductivity anode diffusion layers is crucial. However, the material selection of the anode porous diffusion layer is limited, mainly due to the high oxidation potential and acidic environment during the electrochemical reaction process, which makes most materials unable to be used efficiently for a long time.

[0004] The pore size and pore structure of the anode diffusion layer will significantly affect the gas-liquid two-phase transmission. The study found that as the average pore size of the titanium felt decreases, the PEM water electrolysis performance gradually increases, and the bubbles generated on the electrode will lead to a decrease in water supply. When the average pore size is less than 50μm, the effect of reduced water supply on impedance will be limited, thereby increasing the uniform contact between the electrode and the titanium felt, reducing the contact resistance and activation overpotential. When the electrolysis reaction is carried out in the PEM electrolyzer, the anode of the electrolyzer is an acidic environment, and the electrolysis voltage is usually higher than 1.6V, so titanium materials with good stability must be selected. The pore structure of the porous sintered titanium plate and titanium fiber felt commonly used in the anode diffusion layer can meet the mass transfer needs of the PEM electrolytic cell and achieve higher electrolysis performance. Among them, the thickness of the titanium fiber felt is as low as 0.25mm, and the porosity is as high as 70%. Its structure is more conducive to gas-liquid mass transfer. However, untreated titanium metal will form a layer of titanium dioxide film on the surface in an oxidizing environment, resulting in a significant decrease in conductivity. In addition, the mechanical properties of titanium fiber felt can meet the needs of the electrolytic cell, and the price is relatively expensive. Titanium mesh is cheap, has high porosity but large pores, and is thicker than 1mm, which basically cannot meet the mass transfer requirements and has the worst actual performance when used in electrolytic cells. Considering the performance of the electrolytic cell, titanium fiber felt is the most suitable choice as the diffusion layer.

[0005] There are now a series of studies on the anode diffusion layer of PEM water electrolysis. The traditional preparation method uses concentrated hydrochloric acid etching, roasting and reduction to prepare a noble metal mixed oxide coating on the surface of titanium fiber felt, and the modified titanium fiber felt is used as the anode diffusion layer of the PEM water electrolysis cell. This method optimizes the thickness of the titanium fiber felt and the preparation method of the membrane electrode assembly. The optimized anode diffusion layer has good conductivity, chemical and mechanical stability and corrosion resistance, but the acid etching method has a low acid concentration and a long etching time. Long-term low-concentration acid etching will cause the mechanical strength of the titanium fiber felt to drop significantly, or the surface roughness is too low, and the fine structure of the titanium fiber felt is destroyed. When assembling the electrolytic cell, the proton exchange membrane may be cut, causing the membrane electrode to fail.

[0006] In summary, the traditional anode diffusion layer has the following problems: First, the internal pore structure is relatively complex and the pores are disordered, resulting in greater resistance to gas and water inside it, and poor fluid permeability, which in turn affects the efficiency of the entire electrolysis reaction; second, the pore shape on the surface of the porous material is irregular, the contact efficiency is low and the active sites are few, which reduces the rate of oxygen evolution reaction, and also causes a large contact resistance between the interfaces, further increasing the energy consumption of the electrolytic cell; third, the pores on the surface of the porous material are large and the pore sizes are different. In order to prevent the proton exchange membrane from being damaged by shear force generated by the high pressure difference between the cathode and the anode, a proton exchange membrane with a larger pore size is usually required, thereby increasing the internal resistance and system energy consumption. Therefore, problems such as poor conductivity, easy oxidation, easy detachment of the coating, and high cost have greatly restricted the development of the anode diffusion layer of PEM water electrolysis. Summary of the invention

[0007] In view of the deficiencies in the prior art, the object of the present invention is to provide a PEM water electrolysis anode diffusion layer and a preparation method thereof to solve the problems raised in the above background technology.

[0008] To achieve the above-mentioned purpose, the present invention provides a PEM water electrolysis anode diffusion layer, comprising a porous layer and a microporous layer, wherein the porous layer is a titanium dioxide nanofiber support layer, and the titanium dioxide nanofiber support layer is prepared by hot pressing and calcining at least two layers of titanium nanofiber layers, and a microporous layer is prepared on the surface of the titanium dioxide nanofiber support layer, and the microporous layer comprises platinum black, spherical dehydrogenated titanium powder and a binder.

[0009] Furthermore, the thickness of at least two titanium nanofiber layers after hot pressing is 60-120 μm, the thickness of the microporous layer is 100-200 μm, and the mass ratio of platinum black, spherical dehydrogenated titanium powder and binder in the microporous layer is 1:5-10:3-7.

[0010] Furthermore, the diameter of the titanium nanofibers in the titanium nanofiber layer is 50-200 nm.

[0011] A method for preparing the above-mentioned PEM water electrolysis anode diffusion layer comprises the following steps:

[0012] Step 1: Weigh tetrabutyl titanate, polyvinylrolidone (PVP), polytetrafluoroethylene (PTFE) and alcohol solvent, stir and mix them evenly to prepare electrospinning slurry;

[0013] Step 2: Controlling the electrospinning voltage to prepare the electrospinning slurry prepared in step 1 into titanium nanofibers;

[0014] Step 3: placing the titanium nanofibers prepared in step 2 in batches on a hot press for hot pressing, controlling the hot pressing temperature and pressure to obtain a multi-layer titanium nanofiber layer, wherein each added titanium nanofiber is formed into a titanium nanofiber layer after hot pressing, the number of titanium nanofiber layers is at least two, and the mass of the titanium nanofiber added each time gradually increases, that is, the mass of the titanium nanofiber added in the latter time is greater than the mass of the titanium nanofiber added in the previous time;

[0015] Step 4: calcining the multi-layer titanium nanofiber layer prepared in step 3 to obtain a titanium dioxide nanofiber support layer;

[0016] Step 5: Weigh spherical dehydrogenated titanium powder, platinum black, pore-forming agent, binder and alcohol solvent, mix and disperse them evenly to prepare a microporous layer slurry;

[0017] Step six: the microporous layer slurry prepared in step five is evenly coated on the surface of the titanium dioxide nanofiber support layer prepared in step four by a coating process, and calcined to obtain an anode diffusion layer.

[0018] Furthermore, in step 1, the mass ratio of tetrabutyl titanate, polyvinylrolidone (PVP), polytetrafluoroethylene (PTFE) and alcohol solvent is 1:0.05-0.2:0.1-0.3:5-10; and the viscosity of the electrospinning slurry is 300-700cp.

[0019] Furthermore, in step 2, the voltage of electrospinning is 1-10KV.

[0020] Furthermore, in step three, the hot pressing temperature is 100-160° C., and the pressure is 5-12 MPa. The pressure gradually increases with the increase in the amount of titanium nanofibers, that is, the pressure of the latter time is greater than the pressure of the previous time.

[0021] Furthermore, in step 4, the calcination temperature is 280-460°C; in step 6, the calcination temperature is 600-800°C.

[0022] Furthermore, in step five, the mass ratio of platinum black, spherical dehydrogenated titanium powder, binder, pore-forming agent and alcohol solvent is 1:5-10:3-7:0.02-0.05:20-50; the viscosity of the microporous layer slurry is 200-400cp; the particle size of platinum black is 3-8nm, and the particle size of the spherical dehydrogenated titanium powder is 10-50nm.

[0023] On the one hand, the spherical dehydrogenated titanium powder has a conductive effect, and on the other hand, its structure is relatively uniform and its shape is relatively regular, so the pore size distribution of the prepared microporous layer is uniform.

[0024] Furthermore, the alcohol solvent in the electrospinning slurry and the microporous layer slurry is one or more combinations of ethanol, methanol, isopropanol, and n-propanol; the binder in the microporous layer slurry is PTFE emulsion, and the pore-forming agent is one or more combinations of starch, maltose, sodium bicarbonate, ammonium bicarbonate, and ammonium carbonate.

[0025] Beneficial effects:

[0026] 1. The present invention uses tetrabutyl titanate and the like to prepare electrospinning slurry, and titanium nanofibers are subjected to multiple batches of hot pressing and calcination to generate a titanium dioxide nanofiber support layer. As a porous layer of a water electrolysis diffusion layer, the titanium nanofiber material has the characteristics of strong toughness and not easy to break. In addition, because the voltage and temperature are controllable during the electrospinning process, the size (thickness) of the prepared titanium nanofibers is controllable. Therefore, the water electrolysis anode diffusion layer prepared by the present invention has strong support and toughness, and its support and toughness can be further controlled by controlling the fiber size, so as to be applied in a complex environment; at the same time, after being made into a porous layer, it also has a higher porosity, which improves the water and gas management capabilities during the water electrolysis operation. In addition, in the process of preparing the microporous layer, the microporous layer is coated on the porous layer. Due to the strength and toughness of the porous layer and the uniform pore structure, the microporous layer can be uniformly attached to the surface of the porous layer and is not easy to fall off;

[0027] 2. In the process of preparing titanium nanofibers, polytetrafluoroethylene (PTFE) is added to the electrospinning slurry while adding butyl titanate. Since polytetrafluoroethylene has strong hydrophobicity and will be dissolved and redistributed after electrospinning and calcining, PTFE can be more evenly attached to each nanofiber in the electrospinning process of the electrospinning slurry, further enhancing the strength and support of the fiber, and at the same time making each titanium nanofiber have strong hydrophobicity. The prepared titanium nanofiber has improved hydrophobicity after calcination, which is beneficial to the conduction of water and gas in the anode diffusion layer during actual use, and will not affect the water electrolysis performance due to the water flooding the active sites of the reaction; in addition, in the preparation process using the electrospinning process, since the electrospinning preparation parameters are controllable, it is convenient to control the degree of adhesion of PTFE on the titanium nanofiber, and combined with the amount of PTFE controlled, it is possible to achieve proper distribution of PTFE on the titanium nanofiber, and PTFE will not completely wrap the titanium nanofiber and affect its conductive performance;

[0028] 3. The present invention utilizes electrospinning to prepare titanium nanofibers, and controls the parameters of the fibers by setting temperature and voltage parameters. When preparing the porous support layer, the titanium nanofibers are prepared by hot pressing in batches layer by layer, and a small amount of titanium nanofibers are selected each time for hot pressing. By controlling the pressure and temperature, the thickness of the porous layer and the amount of titanium nanofibers required in each hot pressing process are accurately controlled. The amount of titanium nanofiber material used can be controlled to avoid waste, and the thickness and porosity of the final porous layer can be regulated through each control. If the mass of the titanium nanofibers added each time is the same, the porosity will be too large, thereby solving the defect of disordered pores in the porous layer.

[0029] 4. In the process of preparing the microporous layer, the present invention adds spherical dehydrogenated titanium powder. On the one hand, the titanium powder on the market has irregular shapes and poor fluidity, which is not conducive to forming and improving product performance, so the performance of the manufactured product is poor. The spherical dehydrogenated titanium powder itself has high stability and conductivity. After the microporous layer is prepared with it, the catalyst layer can directly contact the titanium powder when preparing the integral electrode, which effectively enhances the conductivity and stability of the microporous layer, replacing the mainstream titanium felt in the prior art that directly coats iridium or platinum and other precious metal materials to improve the conductivity and stability of the diffusion layer, greatly reducing the cost; on the other hand, the dehydrogenated titanium powder is difficult to be oxidized, which solves the problem that the existing metal titanium is easily oxidized and leads to a decrease in conductivity;

[0030] 5. The pore-forming agent of the present invention is added to help the microporous layer form more water channels and gas channels when the gas escapes after calcination and decomposition, further improving the porosity of the microporous layer, which is beneficial to the water and gas management during the operation of water electrolysis;

[0031] 6. In the process of preparing the microporous layer, the present invention adds nano-sized platinum black. On the one hand, the stability of platinum black is good, which can avoid the corrosion of the microporous layer prepared by traditional carbon powder under the high potential of water electrolysis. On the other hand, the addition of a small amount of platinum black can promote the water electrolysis reaction and improve the efficiency of the electrochemical reaction.

[0032] 7. The overall solution of the present invention solves the problems of the traditional titanium felt diffusion layer, such as the large amount of materials used, high price and short service life. The preparation method of the microporous layer of the present invention is a coating method, which has a simple manufacturing process and high manufacturing efficiency. In summary, the anode diffusion layer prepared by the present invention has good chemical stability, high conductivity, catalytic activity, and is very suitable for application in PEM electrolytic cells. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0034] Embodiment 1:

[0035] Step 1: Weigh 100 g of tetrabutyl titanate, 5 g of polyvinylrolidone (PVP), 10 g of polytetrafluoroethylene (PTFE) and 500 g of ethanol, mix and stir evenly to prepare an electrospinning slurry with a viscosity of 300 cp for standby use;

[0036] Step 2: setting the electrospinning voltage to 1 KV, and making the electrospinning slurry prepared in step 1 into titanium nanofibers with a diameter of 50 nm;

[0037] Step 3: placing the titanium nanofibers prepared in step 2 in 6 batches under a hot press, wherein the masses of the titanium nanofibers are: 0.1g, 0.2g, 0.3g, 0.4g, 0.5g and 0.6g, respectively, setting the hot pressing temperature to 100°C and the pressures to 7MPa, 8MPa, 9MPa, 10MPa, 11MPa and 12MPa, respectively, and performing hot pressing to obtain a 60μm thick titanium nanofiber layer with a six-layer structure;

[0038] Step 4: calcining the titanium nanofiber layer with a six-layer structure prepared in step 3 at 280° C. to obtain a titanium dioxide nanofiber support layer with hydrophobic properties;

[0039] Step 5: Weigh 2 g of platinum black particles with a particle size of 3 nm, 10 g of spherical dehydrogenated titanium powder with a particle size of 10 nm, 24 g of 25 wt.% PTFE emulsion, 0.04 g of starch and 40 g of ethanol, stir and mix evenly to obtain a microporous layer slurry with a viscosity of 200 cp;

[0040] Step 6: The microporous layer slurry prepared in step 5 is uniformly coated on the surface of the titanium dioxide nanofiber support layer prepared in step 4 by a coating process, and calcined at a high temperature of 600° C. to obtain an anode diffusion layer with a microporous layer thickness of 100 μm and a uniform and ordered porous structure.

[0041] Embodiment 2:

[0042] Step 1: Weigh 100 g of tetrabutyl titanate, 20 g of polyvinylrolidone (PVP), 30 g of polytetrafluoroethylene (PTFE) and 1000 g of isopropanol, mix and stir evenly to prepare an electrospinning slurry with a viscosity of 700 cp for later use;

[0043] Step 2: setting the electrospinning voltage to 10 KV, and making the electrospinning slurry prepared in step 1 into titanium nanofibers with a diameter of 200 nm;

[0044] Step 3: placing the titanium nanofibers prepared in step 2 in 6 batches under a hot press, wherein the masses of the titanium nanofibers are: 0.1g, 0.2g, 0.3g, 0.4g, 0.5g and 0.6g, respectively; setting the hot pressing temperature to 160°C and the pressures to 5MPa, 6MPa, 7MPa, 8MPa, 9MPa and 10MPa, respectively, and performing hot pressing to obtain a 120μm thick titanium nanofiber layer with a six-layer structure;

[0045] Step 4: calcining the titanium nanofiber layer with a six-layer structure prepared in step 3 at 460° C. to obtain a titanium dioxide nanofiber support layer with hydrophobic properties;

[0046] Step 5: Weigh 2 g of 8 nm platinum black particles, 20 g of 50 nm spherical dehydrogenated titanium powder, 56 g of 25 wt.% PTFE emulsion, 0.1 g of maltose and 100 g of isopropanol, stir and mix them evenly to obtain a microporous layer slurry with a viscosity of 400 cp;

[0047] Step 6: The microporous layer slurry prepared in step 5 is uniformly coated on the surface of the titanium dioxide nanofiber support layer prepared in step 4 by a coating process, and calcined at a high temperature of 800°C to obtain an anode diffusion layer with a microporous layer thickness of 200 μm and a uniform and ordered porous structure.

[0048] Embodiment 3:

[0049] Step 1: Weigh 100 g of tetrabutyl titanate, 15 g of polyvinylrolidone (PVP), 20 g of polytetrafluoroethylene (PTFE) and 800 g of methanol, mix and stir evenly to prepare an electrospinning slurry with a viscosity of 500 cp for later use;

[0050] Step 2: Setting the electrospinning voltage to 6 KV, the electrospinning slurry prepared in step 1 was made into titanium nanofibers with a diameter of 100 nm;

[0051] Step 3: placing the titanium nanofibers prepared in step 2 under a hot press in 6 batches, wherein the masses of the titanium dioxide nanofibers are 0.1 g, 0.2 g, 0.3 g, 0.4 g, 0.5 g and 0.6 g, respectively; setting the hot pressing temperature to 140°C and the pressures to 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa and 11 MPa, respectively, and performing hot pressing to obtain a titanium nanofiber layer with a thickness of 90 μm and a six-layer structure;

[0052] Step 4: calcining the titanium nanofiber layer with a six-layer structure prepared in step 3 at 360° C. to obtain a titanium dioxide nanofiber support layer with hydrophobic properties;

[0053] Step 5: Weigh 2 g of platinum black particles with a particle size of 5 nm, 16 g of spherical dehydrogenated titanium powder with a particle size of 30 nm, 40 g of 25 wt.% PTFE emulsion, 0.08 g of starch and 80 g of methanol, stir and mix them evenly to obtain a microporous layer slurry with a viscosity of 300 cp;

[0054] Step 6: Use a coating process to evenly coat the microporous layer slurry prepared in step 5 on the surface of the titanium dioxide nanofiber support layer prepared in step 4, and calcine it at a high temperature of 800°C to obtain an anode diffusion layer with a microporous layer thickness of 150 μm and a uniform and ordered porous structure.

[0055] Comparative Example 1: (without platinum black)

[0056] Step 1: Weigh 100 g of tetrabutyl titanate, 5 g of polyvinylrolidone (PVP), 10 g of polytetrafluoroethylene (PTFE) and 500 g of ethanol, mix and stir evenly to prepare an electrospinning slurry with a viscosity of 300 cp for standby use;

[0057] Step 2: setting the electrospinning voltage to 1 KV, and making the electrospinning slurry prepared in step 1 into titanium nanofibers with a diameter of 50 nm;

[0058] Step 3: placing the titanium nanofibers prepared in step 2 in 6 batches under a hot press, wherein the masses of the titanium nanofibers are: 0.1g, 0.2g, 0.3g, 0.4g, 0.5g and 0.6g, respectively, setting the hot pressing temperature to 100°C and the pressures to 7MPa, 8MPa, 9MPa, 10MPa, 11MPa and 12MPa, respectively, and performing hot pressing to obtain a 60μm thick titanium nanofiber layer with a six-layer structure;

[0059] Step 4: calcining the titanium nanofiber layer with a six-layer structure prepared in step 3 at 280° C. to obtain a titanium dioxide nanofiber support layer with hydrophobic properties;

[0060] Step 5: Weigh 10 g of spherical dehydrogenated titanium powder with a particle size of 10 nm, 24 g of 25 wt.% PTFE emulsion, 0.04 g of starch and 40 g of ethanol, stir and mix them evenly to obtain a microporous layer slurry with a viscosity of 180 cp;

[0061] Step 6: The microporous layer slurry prepared in step 5 is uniformly coated on the surface of the titanium dioxide nanofiber support layer prepared in step 4 by a coating process, and calcined at a high temperature of 600° C. to obtain an anode diffusion layer with a microporous layer thickness of 100 μm and a uniform and ordered porous structure.

[0062] Comparative Example 2: (PTFE is not added to the porous layer)

[0063] Step 1: Weigh 100 g of tetrabutyl titanate, 5 g of polyvinylrolidone (PVP) and 500 g of ethanol, mix and stir evenly to prepare an electrospinning slurry with a viscosity of 300 cp for later use;

[0064] Step 2: setting the electrospinning voltage to 1 KV, and making the electrospinning slurry prepared in step 1 into titanium nanofibers with a diameter of 50 nm;

[0065] Step 3: placing the titanium nanofibers prepared in step 2 in 6 batches under a hot press, wherein the masses of the titanium nanofibers are: 0.1g, 0.2g, 0.3g, 0.4g, 0.5g and 0.6g, respectively, setting the hot pressing temperature to 100°C and the pressures to 7MPa, 8MPa, 9MPa, 10MPa, 11MPa and 12MPa, respectively, and performing hot pressing to obtain a 60μm thick titanium nanofiber layer with a six-layer structure;

[0066] Step 4: calcining the titanium nanofiber layer with a six-layer structure prepared in step 3 at 280° C. to obtain a titanium dioxide nanofiber support layer with hydrophobic properties;

[0067] Step 5: Weigh 2 g of platinum black particles with a particle size of 3 nm, 10 g of spherical dehydrogenated titanium powder with a particle size of 10 nm, 24 g of 25 wt.% PTFE emulsion, 0.04 g of starch and 40 g of ethanol, stir and mix evenly to obtain a microporous layer slurry with a viscosity of 200 cp;

[0068] Step 6: The microporous layer slurry prepared in step 5 is uniformly coated on the surface of the titanium dioxide nanofiber support layer prepared in step 4 by a coating process, and calcined at a high temperature of 600° C. to obtain an anode diffusion layer with a microporous layer thickness of 100 μm and a uniform and ordered porous structure.

[0069] Comparative Example 3: (Use ordinary titanium powder instead of spherical dehydrogenated titanium powder)

[0070] Step 1: Weigh 100 g of tetrabutyl titanate, 5 g of polyvinylrolidone (PVP), 10 g of polytetrafluoroethylene (PTFE) and 500 g of ethanol, mix and stir evenly to prepare an electrospinning slurry with a viscosity of 300 cp for standby use;

[0071] Step 2: setting the electrospinning voltage to 1 KV, and making the electrospinning slurry prepared in step 1 into titanium nanofibers with a diameter of 50 nm;

[0072] Step 3: placing the titanium nanofibers prepared in step 2 in 6 batches under a hot press, wherein the masses of the titanium nanofibers are: 0.1g, 0.2g, 0.3g, 0.4g, 0.5g and 0.6g, respectively, setting the hot pressing temperature to 100°C and the pressures to 7MPa, 8MPa, 9MPa, 10MPa, 11MPa and 12MPa, respectively, and performing hot pressing to obtain a 60μm thick titanium nanofiber layer with a six-layer structure;

[0073] Step 4: calcining the titanium nanofiber layer with a six-layer structure prepared in step 3 at 280° C. to obtain a titanium dioxide nanofiber support layer with hydrophobic properties;

[0074] Step 5: Weigh 2 g of platinum black particles with a particle size of 3 nm, 10 g of ordinary titanium powder with a particle size of 10 nm, 24 g of 25 wt.% PTFE emulsion, 0.04 g of starch and 40 g of ethanol, stir and mix evenly to obtain a microporous layer slurry with a viscosity of 210 cp;

[0075] Step 6: The microporous layer slurry prepared in step 5 is uniformly coated on the surface of the titanium dioxide nanofiber support layer prepared in step 4 by a coating process, and calcined at a high temperature of 600° C. to obtain an anode diffusion layer with a microporous layer thickness of 100 μm and a uniform and ordered porous structure.

[0076] Comparative Example 4: (without adding pore forming agent)

[0077] Step 1: Weigh 100 g of tetrabutyl titanate, 5 g of polyvinylrolidone (PVP), 10 g of polytetrafluoroethylene (PTFE) and 500 g of ethanol, mix and stir evenly to prepare an electrospinning slurry with a viscosity of 300 cp for standby use;

[0078] Step 2: setting the electrospinning voltage to 1 KV, and making the electrospinning slurry prepared in step 1 into titanium nanofibers with a diameter of 50 nm;

[0079] Step 3: placing the titanium nanofibers prepared in step 2 in 6 batches under a hot press, wherein the masses of the titanium nanofibers are: 0.1g, 0.2g, 0.3g, 0.4g, 0.5g and 0.6g, respectively, setting the hot pressing temperature to 100°C and the pressures to 7MPa, 8MPa, 9MPa, 10MPa, 11MPa and 12MPa, respectively, and performing hot pressing to obtain a 60μm thick titanium nanofiber layer with a six-layer structure;

[0080] Step 4: calcining the titanium nanofiber layer with a six-layer structure prepared in step 3 at 280° C. to obtain a titanium dioxide nanofiber support layer with hydrophobic properties;

[0081] Step 5: Weigh 2 g of platinum black particles with a particle size of 3 nm, 10 g of spherical dehydrogenated titanium powder with a particle size of 10 nm, 24 g of 25 wt.% PTFE emulsion and 40 g of ethanol, stir and mix evenly to obtain a microporous layer slurry with a viscosity of 190 cp;

[0082] Step 6: The microporous layer slurry prepared in step 5 is uniformly coated on the surface of the titanium dioxide nanofiber support layer prepared in step 4 by a coating process, and calcined at a high temperature of 600° C. to obtain an anode diffusion layer with a microporous layer thickness of 100 μm and a uniform and ordered porous structure.

[0083] Comparative Example 5: (Titanium nanofibers are hot pressed in one go)

[0084] Step 1: Weigh 100 g of tetrabutyl titanate, 5 g of polyvinylrolidone (PVP), 10 g of polytetrafluoroethylene (PTFE) and 500 g of ethanol, mix and stir evenly to prepare an electrospinning slurry with a viscosity of 300 cp for standby use;

[0085] Step 2: setting the electrospinning voltage to 1 KV, and making the electrospinning slurry prepared in step 1 into titanium nanofibers with a diameter of 50 nm;

[0086] Step 3: 2.1 g of titanium nanofibers prepared in step 2 are placed in a hot press at one time, and the hot pressing temperature is set to 100° C. and the pressure is set to 12 MPa, and hot pressing is performed to obtain a 60 μm thick titanium nanofiber layer;

[0087] Step 4: calcining the titanium nanofiber layer prepared in step 3 at 280° C. to obtain a titanium dioxide nanofiber support layer having hydrophobic properties;

[0088] Step 5: Weigh 2 g of platinum black particles with a particle size of 3 nm, 10 g of spherical dehydrogenated titanium powder with a particle size of 10 nm, 24 g of 25 wt.% PTFE emulsion, 0.04 g of starch and 40 g of ethanol, stir and mix evenly to obtain a microporous layer slurry with a viscosity of 200 cp;

[0089] Step 6: Use a coating process to evenly coat the microporous layer slurry prepared in step 5 on the surface of the single-layer titanium dioxide nanofiber support layer prepared in step 4, and calcine it at a high temperature of 600°C to obtain an anode diffusion layer with a microporous layer thickness of 100 μm and a uniform and ordered porous structure.

[0090] Test conditions: Anode catalyst is 2 mg / cm 2 kO2, cathode catalyst is 0.4mg Pt / cm 2 70% Pt / C, the proton exchange membrane is Nation 115 membrane, and the test temperature is 80°C.

[0091] The electrochemical performance results of the membrane electrodes prepared using the anode diffusion layers in the examples and comparative examples are shown in Table 1.

[0092] Table 1 Membrane electrode electrolysis current density table

[0093]

[0094] As shown in Table 1, the anode diffusion layer for water electrolysis prepared by the present invention has excellent electrochemical activity of the membrane electrode. At an electrolysis voltage of 2.0 V, the current density is 1900 mA / cm 2 nearby.

[0095] In the comparative examples, in comparative example 1, platinum black was not added during the preparation of the microporous layer, so its catalytic performance was lower than that of the embodiment; in comparative example 2, PTFE was not added during the preparation of the porous layer, and the water-gas separation effect of the prepared porous layer was poor, resulting in low efficiency of the prepared membrane electrode reaction; in comparative example 3, ordinary titanium powder was added during the preparation of the microporous layer. Due to the irregular shape of the ordinary titanium powder, the pore size distribution of the prepared microporous layer was uneven, the liquid transmission pressure in some places with smaller pore sizes increased, gas transmission could not be carried out, the mass transfer of gas and liquid was affected, the resistance increased, and the electrocatalytic efficiency was reduced. activity, so the electrochemical performance is poor; in Comparative Example 4, no pore-forming agent was added during the preparation of the microporous layer, the porosity of the prepared microporous layer was low, the gas transmission was hindered, the catalytic efficiency of water was affected, and the electrochemical performance was poor; in Comparative Example 5, during the preparation of the porous layer, one-time hot pressing was adopted, and the fiber material could not be evenly distributed through the process, resulting in the prepared porous layer having dense pore distribution in some places and sparse distribution in some places. The prepared porous layer has poor controllability, so the uneven pore distribution finally causes uneven gas-liquid transmission, resulting in poor performance.

[0096] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A method for preparing a PEM water electrolysis anode diffusion layer, characterized in that: The following steps are involved: Step 1: Weigh tetrabutyl titanate, polyvinylrolidone, polytetrafluoroethylene and alcohol solvent, stir and mix them evenly to prepare electrospinning slurry; Step 2: Controlling the electrospinning voltage to prepare the electrospinning slurry prepared in step 1 into titanium nanofibers; Step 3: placing the titanium nanofibers prepared in step 2 in batches on a hot press for hot pressing, controlling the hot pressing temperature and pressure to obtain a multi-layer titanium nanofiber layer, wherein each added titanium nanofiber is formed into a titanium nanofiber layer after hot pressing, the number of titanium nanofiber layers is at least two, and the mass of each added titanium nanofiber gradually increases; Step 4: calcining the multi-layer titanium nanofiber layer prepared in step 3 to obtain a titanium dioxide nanofiber support layer; Step 5: Weigh spherical dehydrogenated titanium powder, platinum black, pore-forming agent, binder and alcohol solvent, mix and disperse them evenly to prepare a microporous layer slurry; Step six: the microporous layer slurry prepared in step five is evenly coated on the surface of the titanium dioxide nanofiber support layer prepared in step four by a coating process, and calcined to obtain an anode diffusion layer.

2. The method for preparing the PEM water electrolysis anode diffusion layer according to claim 1, characterized in that: In step 1, the mass ratio of tetrabutyl titanate, polyvinylrolidone, polytetrafluoroethylene and alcohol solvent is 1:0.05-0.2:0.1-0.3:5-10; the viscosity of the electrospinning slurry is 300-700cp.

3. The method for preparing the PEM water electrolysis anode diffusion layer according to claim 1, characterized in that: In step 2, the voltage of electrospinning is 1-10KV.

4. The method for preparing a PEM water electrolysis anode diffusion layer according to claim 1, characterized in that: In step three, the hot pressing temperature is 100-160° C. and the pressure is 5-12 MPa, and the pressure gradually increases with the increase in the amount of titanium nanofibers.

5. The method for preparing a PEM water electrolysis anode diffusion layer according to claim 1, characterized in that: In step 4, the calcination temperature is 280-460°C; in step 6, the calcination temperature is 600-800°C.

6. The method for preparing a PEM water electrolysis anode diffusion layer according to claim 1, characterized in that: In step five, the mass ratio of platinum black, spherical dehydrogenated titanium powder, binder, pore former and alcohol solvent is 1:5-10:3-7:0.02-0.05:20-50; the viscosity of the microporous layer slurry is 200-400cp; the particle size of platinum black is 3-8nm, and the particle size of the spherical dehydrogenated titanium powder is 10-50nm.

7. The method for preparing a PEM water electrolysis anode diffusion layer according to claim 1, characterized in that: The alcohol solvent in the electrospinning slurry and the microporous layer slurry is one or more combinations of ethanol, methanol, isopropanol, and n-propanol; the binder in the microporous layer slurry is PTFE emulsion, and the pore-forming agent is one or more combinations of starch, maltose, sodium bicarbonate, ammonium bicarbonate, and ammonium carbonate.

8. A PEM water electrolysis anode diffusion layer prepared by the method for preparing a PEM water electrolysis anode diffusion layer according to any one of claims 1 to 7, characterized in that: It comprises a porous layer and a microporous layer, wherein the porous layer is a titanium dioxide nanofiber support layer, and the titanium dioxide nanofiber support layer is prepared by hot pressing and calcining at least two layers of titanium nanofiber layers, and a microporous layer is prepared on the surface of the titanium dioxide nanofiber support layer, and the microporous layer comprises platinum black, spherical dehydrogenated titanium powder and a binder.

9. The PEM water electrolysis anode diffusion layer according to claim 8, characterized in that: The thickness of at least two titanium nanofiber layers after hot pressing is 60-120 μm, the thickness of the microporous layer is 100-200 μm, and the mass ratio of platinum black, spherical dehydrogenated titanium powder and binder in the microporous layer is 1:5-10:3-7.

10. The PEM water electrolysis anode diffusion layer according to claim 8, characterized in that: The diameter of the titanium nanofibers in the titanium nanofiber layer is 50-200 nm.

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