Membrane electrode for producing hydrogen by alkaline water electrolysis, preparation method thereof and electrolyzer

Abstract

The present invention provides a membrane electrode for hydrogen production by alkaline water electrolysis, a preparation method thereof and an electrolyzer. The preparation method provided by the present invention can obtain a membrane electrode with a catalyst layer uniformly and firmly attached to the surface of a diaphragm by direct coating and hot pressing, and can give the membrane electrode good stability, and the obtained membrane electrode has a significantly reduced water electrolysis overpotential. The preparation method comprises the following steps: directly coating the catalyst slurry on both sides of the diaphragm, and forming a catalyst layer on both sides of the diaphragm after drying and hot pressing to obtain the membrane electrode; the diaphragm is selected from a porous diaphragm or an alkaline anion exchange membrane; the catalyst slurry includes a binder solution and a catalyst, wherein the binder solution is one or more of a perfluorosulfonic acid resin solution and a perfluorosulfonic acid ionomer dispersion, and the mass concentration of the binder solution is 5-30%; the mass ratio of the binder solution to the catalyst is 1:1-4:1.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen production by alkaline water electrolysis, and in particular to a membrane electrode used for hydrogen production by alkaline water electrolysis, a preparation method thereof and an electrolytic cell. Background Art

[0002] Hydrogen production by water electrolysis is the most effective way to develop clean and pollution-free hydrogen energy. Hydrogen production technologies by water electrolysis include proton exchange membrane water electrolysis, alkaline water electrolysis, solid oxide water electrolysis, and anion exchange membrane water electrolysis. At present, alkaline water electrolysis dominates the water electrolysis industry. The technology is relatively mature and the equipment cost is low. It is an important means to achieve large-scale production of hydrogen, but one of the current problems is the high energy consumption. In the hydrogen production process, the diaphragm and electrode are the core components of the alkaline water electrolysis hydrogen production electrolyzer; in traditional electrolyzers, a separated "diaphragm-electrode" structure is used. This structure will produce a large overpotential during the application process, resulting in high energy consumption. Therefore, the development of a new membrane electrode is one of the main breakthroughs in reducing the unit energy consumption of hydrogen production.

[0003] However, how to develop membrane electrodes suitable for alkaline water electrolysis technology still faces many technical difficulties that need to be overcome. Although an integrated membrane electrode has been proposed in the field of proton exchange membrane water electrolysis hydrogen production, due to the essential differences between proton exchange membranes and non-proton exchange membranes in alkaline water electrolysis technology (such as porous diaphragms and alkaline ion exchange membranes), the membrane electrode preparation technology suitable for proton exchange membrane water electrolysis technology is difficult to be directly applied to membrane electrodes for alkaline water electrolysis. There are significant differences in the properties of these two types of base membranes, among which the proton exchange membrane is a polymer electrolyte film with cation exchange groups (sulfonic acid groups, carboxylic acid groups, phosphoric acid groups, etc.), while the porous diaphragm and alkaline ion exchange membrane are a kind of membrane that can conduct anions in an aqueous environment and prevent cations and other neutral molecules from passing through. The preparation of membrane electrodes must consider the compatibility of the slurry and the base membrane. The type of solvent or the strength of polarity in the slurry will affect the base membrane. The preparation of membrane electrodes for proton exchange membranes usually adopts the transfer method. Since the solvent used will cause swelling problems on the base membrane, the slurry cannot be directly coated on the base membrane. Therefore, the membrane electrode preparation technology in the proton exchange membrane water electrolysis technology is difficult to be directly applied to the membrane electrode for alkaline water electrolysis.

[0004] Patent application CN115074775A discloses an integrated composite membrane, including a diaphragm layer, an anode catalyst layer, a hydrogen evolution cathode catalyst layer, and an anode conductive mesh and a cathode conductive mesh, wherein the two catalyst layers are prepared by attaching slurry to both sides of the diaphragm layer and then hot pressing, and can form an integrated structure that is tightly integrated with the diaphragm layer to reduce contact resistance; the pore size of the anode catalyst layer and the hydrogen evolution cathode catalyst layer are both larger than the pore size of the diaphragm layer, and the pore size of the anode catalyst layer and the hydrogen evolution cathode catalyst layer gradually increases from the inside to the outside, which helps to guide the gas to diffuse to the outside of the membrane and reduce the phenomenon of gas crossing the membrane and gas lodging. The application mentions that the composite membrane provided by it has the functions and structures of integrated electronic conduction, electrocatalytic cathode hydrogen evolution and anode oxidation, and ion conduction, which can improve the working performance at high current density, help to improve the hydrogen production rate of electrolysis equipment, and reduce costs. This patent application facilitates the diffusion of gas to the outside of the integrated membrane by gradually increasing the pore size in the hydrogen evolution cathode catalyst layer from the inside to the outside; and the hydrogen evolution cathode catalyst layer is prepared layer by layer by cathode slurry, and when preparing layer by layer, it is necessary to increase the mass ratio of the pore former and the catalyst in the slurry used in sequence, so that the pore size gradually increases. Summary of the invention

[0005] Based on this, the present invention provides a different solution to provide a membrane electrode for alkaline water electrolysis to produce hydrogen, a preparation method thereof and an electrolyzer. Based on a porous diaphragm and an alkaline anion exchange membrane, a simple and easy-to-operate preparation process for a membrane electrode for alkaline water electrolysis to produce hydrogen is proposed. A membrane electrode with a catalyst layer uniformly and firmly attached to the surface of the diaphragm can be obtained by direct coating and hot pressing, and the membrane electrode can be given good stability, and the resulting membrane electrode has a lower water electrolysis voltage.

[0006] To achieve the purpose, the present invention provides the following technical solutions:

[0007] In one aspect, the present invention provides a method for preparing a membrane electrode for producing hydrogen by alkaline water electrolysis, the preparation method comprising the following steps:

[0008] Directly coating the catalyst slurry on both sides of the diaphragm, and forming catalyst layers on both sides of the diaphragm after drying and hot pressing to obtain the membrane electrode;

[0009] The diaphragm is selected from a porous diaphragm or an alkaline anion exchange membrane;

[0010] The catalyst slurry comprises a binder solution and a catalyst, wherein the binder solution is one or more of a perfluorosulfonic acid resin solution and a perfluorosulfonic acid ionomer dispersion, and the mass concentration of the binder solution is 5-30%, preferably 5-20%; the mass ratio of the binder solution to the catalyst is 1:1-4:1.

[0011] Through the above technical scheme of the present invention, a perfluorosulfonic acid resin solution and / or a perfluorosulfonic acid ionomer dispersion with a mass concentration of 5-30% (preferably 5-20%) is used as a binder solution, and the mass ratio of the binder solution to the catalyst is controlled at 1:1-4:1. The slurry can be well applied to the surface of a porous diaphragm or an alkaline anion exchange membrane by direct coating, and can form a uniform and firm catalyst layer after drying and hot pressing. The obtained membrane electrode has good stability and a lower water electrolysis voltage.

[0012] In some preferred embodiments, the thickness of the diaphragm is 100-500 μm. When the preparation method of the present invention is used to prepare a membrane electrode for hydrogen production by alkaline water electrolysis, it is not necessary to use a thicker diaphragm (for example, a thickness exceeding 500 μm). In the process of preparing the membrane electrode, a membrane electrode with good stability can be obtained by direct coating and hot pressing, and the problem of easy penetration of the diaphragm in the prior art that is too thin will not occur.

[0013] In some preferred embodiments, the porous membrane is selected from polysulfone, polyethersulfone, polyvinyl chloride or polyphenylene sulfide porous membrane; in some preferred embodiments, the alkaline anion exchange membrane is selected from quaternary ammonium salt anion exchange membrane, polyethersulfone anion exchange membrane or polyphenylene ether anion exchange membrane. In some embodiments, the membrane used is, for example, Zirfon UTP 500, Zirfon UTP 500+, Zirfon UTP 220 membrane, etc.

[0014] In some embodiments, the solvent in the binder solution is a mixed solvent of water and an organic solvent. The binder solution can be directly purchased from a commercial source, or can be self-made, or the commercially available binder solution can be diluted with the above solvent to obtain a binder solution of desired concentration. The organic solvent is, for example, one or more selected from methanol, ethanol, n-propanol, isopropanol, and polyethylene glycol; in some embodiments, the mass ratio of water to the organic solvent is 0.5:1 to 1:1.

[0015] In some preferred embodiments, the particle size of the catalyst is less than 100 μm, and more preferably less than 40 μm. The inventors have found that if the particle size is controlled within the preferred range, it is beneficial to improve the dispersibility of the catalyst in the binder solution and to improve the uniformity of the catalyst slurry coated on the diaphragm surface.

[0016] In some preferred embodiments, the mass concentration of the binder solution is controlled to 5-20%, which is conducive to further reducing the water electrolysis voltage of the membrane electrode in alkaline electrolyzed water. If the binder concentration is higher, it may cause the water electrolysis voltage to increase. The mass ratio of the binder solution and the catalyst is controlled at 1:1-4:1, which is conducive to taking into account good catalyst layer firmness and making the membrane electrode take into account a lower water electrolysis voltage. In some better embodiments, on the basis of controlling the mass fraction of the binder solution at 5-20%, the mass ratio of the binder solution and the catalyst is 1:1-4:1, which is conducive to obtaining a membrane electrode with better performance, which not only has better catalyst layer firmness, but also has a significantly lower water electrolysis voltage. In some further better embodiments, the mass fraction of the binder solution is 5-10%; the mass ratio of the binder solution and the catalyst is 1:1-2:1, which can obtain further improved membrane electrode performance, not only the catalyst layer firmness is good, but also a significantly lower water electrolysis voltage can be obtained.

[0017] The amount of catalyst slurry coated on the surface of the diaphragm can be determined according to the required catalyst layer thickness. In some embodiments, the thickness of the catalyst layer is 2-50 μm; preferably, the thickness is ≥3 μm and <10 μm. Controlling the catalyst layer thickness within the preferred range can improve the utilization rate of the catalyst and help further reduce the water electrolysis voltage.

[0018] In some embodiments, the catalyst is selected from materials having hydrogen evolution catalytic activity or oxygen evolution catalytic activity. The catalyst having hydrogen evolution catalytic activity and the catalyst having oxygen evolution catalytic activity can be corresponding catalyst materials conventional in the art, without particular limitation, such as metal elements, alloys, metal or non-metal compounds having corresponding activity, etc.; for example, the above catalyst can be one or more of Pt, Ru, Pd, Ir elements and alloys thereof, and Ni, Co, Mo, Cr, Cu elements, alloys, phosphides and nitrides; specifically, the catalyst can be, for example, but not limited to, Raney nickel catalyst, nickel ferrite catalyst, FeCoNi catalyst, NiFe 2 O 4 Catalyst, ZnNi(Fe 2 O 4 ) 2 One or more of catalysts, etc.; these catalysts can be obtained commercially. Specifically, the catalyst layers formed on the two sides of the diaphragm are respectively a cathode catalyst layer and an anode catalyst layer, the catalyst in the anode catalyst layer uses a catalyst having at least oxygen evolution catalytic activity, and the catalyst in the cathode catalyst layer uses a catalyst having at least hydrogen evolution catalytic activity; and some catalysts themselves have good hydrogen evolution and oxygen evolution activities, so the same catalyst can be used in the anode catalyst layer and the cathode catalyst layer.

[0019] In some preferred embodiments, the following operation is further included: after the drying is completed, a hydrophobic protective film is applied on the surface of the coating formed by the catalyst slurry, and then the hot pressing is performed, and the hydrophobic protective film is peeled off after the hot pressing is completed; preferably, the hydrophobic protective film is selected from aluminum foil, copper foil, tin foil, polytetrafluoroethylene (PTFE) film, polyethylene terephthalate (PET) film, PET film with silicone coating on the surface, and PTFE film with PET or polypropylene (PP) support. The inventors have found that after the catalyst slurry is coated on the surface of the porous diaphragm or alkaline anion exchange membrane and dried, a layer of hydrophobic protective film is provided on the surface during the hot pressing process, and no adhesion will be caused when peeling after hot pressing.

[0020] In some preferred embodiments, the hot pressing conditions include: hot pressing temperature 80-180°C, pressure 3-10MPa, hot pressing time 1-10min, and hot pressing can be carried out in a flat hot press; hot pressing after drying to form a catalyst layer is beneficial to enhance the wetting and fluidity of the binder in the catalyst slurry, increase the bonding contact area, and enhance the firmness of the formed catalyst layer on the surface of the diaphragm. In some preferred embodiments, the drying conditions include: drying temperature 60-150°C, drying time 10-240min; the coating conditions include: coating speed 20-100mm / s; the use of preferred process conditions for the preparation of membrane electrodes is beneficial to further improve the uniformity and adhesion firmness of the catalyst coating on the surface of the diaphragm. In the coating process, the catalyst slurry can be coated by a scraper method, a roll-to-roll coating method, a slit coating method, or a roll-to-roll coating method.

[0021] In a preferred embodiment, the hot pressing conditions are: hot pressing temperature 120-160°C, pressure 5-8MPa, hot pressing time 3-5min; the drying conditions include: drying temperature 80-120°C, drying time 30-60min; the coating conditions include: coating speed 20-60mm / s; the use of the preferred process conditions for the preparation of the membrane electrode is conducive to further improving the uniformity and adhesion of the catalyst coating on the surface of the diaphragm. In the preparation method of the present invention, when preparing the catalyst slurry, the catalyst can be dispersed in the binder solution by mechanical stirring or ultrasonic dispersion. In a preferred embodiment, the preparation step of the catalyst slurry includes: after mixing the binder solution and the catalyst, first disperse them at high speed through a homogenizer for 5-30 minutes, with a rotation speed of 5000-20000 rpm, preferably 8000-15000 rpm; then ultrasonically disperse them for 1-10 minutes, and the dispersion is carried out at a temperature of 0-10°C; the catalyst slurry prepared in this way has better stability, and the instability index is between 0.01-0.03.

[0022] A second aspect of the present invention provides a membrane electrode for producing hydrogen by alkaline water electrolysis, wherein the membrane electrode is prepared by the preparation method described above.

[0023] The present invention also provides an electrolyzer for producing hydrogen by alkaline water electrolysis, wherein the membrane electrode is the membrane electrode described above. Other structures of the electrolyzer can adopt conventional structures in the art, which will not be described in detail here.

[0024] The technical solution provided by the present invention has the following beneficial effects:

[0025] The present invention provides a method for preparing a membrane electrode based on a porous diaphragm or an alkaline ion exchange membrane for hydrogen production technology by alkaline water electrolysis, which can form a uniform and firm catalyst layer on the surface of the above-mentioned diaphragm by a simple direct coating-hot pressing method; the method has a simple process and is convenient and quick to operate; moreover, the membrane electrode prepared by the method has a lower water electrolysis voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a photo of the membrane electrode after testing in Example 1;

[0027] Figure 2 This is a photo of the membrane electrode after testing in Comparative Example 1;

[0028] Figure 3 This is a summary diagram of the test results of water electrolysis voltage;

[0029] Figure 4 This is a photo of the heat pressing effect in Comparative Example 4;

[0030] Figure 5 This is a polarizing microscope photograph of the catalyst layer formed by the membrane electrode catalyst slurry II in Example 2;

[0031] Figure 6 This is a photo of the membrane electrode after the firmness test in Example 3;

[0032] Figure 7 This is a diagram showing the stability test results of the membrane electrode in Example 1;

[0033] Figure 8 This is a photograph of the catalyst layer surface before hot pressing of the membrane electrode prepared in Example 1;

[0034] Fig. 9 This is a polarizing microscope photograph of the catalyst layer on the membrane electrode surface in Comparative Example 5;

[0035] Fig.10 This is a photo of the membrane electrode in Comparative Example 1 after the firmness test;

[0036] Fig.11 This is a diagram showing the stability test results of the membrane electrode in Comparative Example 1. DETAILED DESCRIPTION

[0037] In order to facilitate the understanding of the present invention, the present invention will be further described below in conjunction with examples. It should be understood that the following examples are only for a better understanding of the present invention and do not mean that the present invention is limited to the following examples.

[0038] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in the art can be used. The reagents or instruments used without specifying the manufacturer are all conventional products that can be purchased commercially.

[0039] Ingredients Description:

[0040] Raney nickel catalyst and nickel ferrite catalyst were purchased from Jiangsu Raney Metal Technology Co., Ltd. and Beijing Dekedaojin Technology Co., Ltd., respectively;

[0041] Nafion solution: purchased from DuPont, USA, wherein the solvent is a mixed solvent of water and volatile organic matter (mainly isopropanol) in a mass ratio of 34%:46%, and the Nafion concentration is 20wt%; the Nafion solutions with lower concentrations used in the subsequent examples are all obtained by diluting the 20wt% Nafion solution with a mixed solvent of water and isopropanol in a mass ratio of 34:46;

[0042] Zirfon UTP 500 membrane and Zirfon UTP 220 membrane: purchased from AGFA, Germany.

[0043] Test method description:

[0044] In the following examples and comparative examples, the water electrolysis voltage test was carried out under the following conditions: Membrane electrode performance test: The performance test was carried out on an IT6162B DC power supply, the electrolyte was a 30% KOH solution by mass, the reaction temperature was 80±2°C, and the reaction temperature was monitored by a temperature controller. The reaction current density was 0.4 and 0.8 A / cm 2 , the test time is 2h respectively.

[0045] Embodiment 1:

[0046] Weighing a Raney nickel catalyst having a particle size greater than 10 μm and less than 40 μm, adding a Nafion solution having a mass fraction of 10 wt%, wherein the mass ratio of the Nafion solution to the catalyst is 2:1, dispersing the resulting mixture in a homogenizer at high speed (speed of 10,000 rpm) for 10 min, and then ultrasonically dispersing for 5 min, and dispersing at a temperature range of 0-10° C., to obtain a catalyst slurry;

[0047] The catalyst slurry was then scraped onto both sides of the Zirfon220 membrane (thickness 220μm) at a speed of 20mm / s, and then vacuum dried at 80°C for 60min. After that, a PTFE membrane (a hydrophobic membrane) was selected as a protective membrane, and the protective membrane was laid between the hot pressing plate and the catalyst slurry layer of the flat hot press, and hot pressed at 130°C and 5MPa pressure for 5min. After cooling, the protective membrane was removed to obtain a membrane electrode for alkaline water electrolysis. The catalyst layer thickness of the obtained membrane electrode is about 5μm, which can be confirmed by SEM observation.

[0048] The membrane electrode was assembled into an electrolytic cell and tested at 0.4 A / cm 2 and 0.8A / cm 2 Water electrolysis voltage under current density, test results are shown in Figure 3 . Observe and take photos of the surface of the membrane electrode after the test, such as Figure 1 shown; from Figure 1 It can be seen that after the test, the membrane electrode surface coating is intact and the catalyst has not fallen off, indicating that the coating has good firmness.

[0049] Embodiment 2:

[0050] A nickel ferrite catalyst having a particle size greater than 10 μm and less than 40 μm was weighed, and a Nafion solution having a mass fraction of 8 wt% was added, wherein the mass ratio of the Nafion solution to the catalyst was 3:1. The resulting mixture was dispersed in a homogenizer at high speed (speed of 8000 rpm) for 10 min, and then ultrasonically dispersed for 5 min, and the dispersion was carried out in a temperature range of 0-10°C to obtain catalyst slurry I; a Raney nickel catalyst having a particle size greater than 10 μm and less than 40 μm was weighed, and a Nafion solution having a mass fraction of 8 wt% was added, wherein the mass ratio of the Nafion solution to the catalyst was 3:1, and ultrasonically dispersed for 3 h to obtain catalyst slurry II.

[0051] Then, the two catalyst slurries I and II were respectively scraped onto the two sides of the Zirfon500 film (thickness 500μm) at a speed of 20mm / s, and then vacuum dried at 120℃ for 30min. After that, a PET film was selected as a protective film, and the protective film was laid between the hot pressing plate and the catalyst slurry layer of the flat hot press, and hot pressed at 150℃ and 8MPa pressure for 3min. After cooling, the protective film was removed to obtain a membrane electrode for alkaline water electrolysis. The catalyst layer thickness of the obtained membrane electrode was about 5μm.

[0052] The membrane electrode was assembled into an electrolytic cell and tested at 0.4 A / cm 2 and 0.8A / cm 2 Water electrolysis voltage under current density, test results are shown in Figure 3. The surface of the membrane electrode was observed after the test. The coating on the membrane electrode surface was intact and the catalyst did not fall off, indicating that the coating had good firmness.

[0053] Embodiment 3:

[0054] Weighing a Raney nickel catalyst having a particle size greater than 10 μm and less than 40 μm, adding a Nafion solution having a mass fraction of 15 wt%, wherein the mass ratio of the Nafion solution to the catalyst is 1.5:1, dispersing the resulting mixture in a homogenizer at high speed (speed of 15000 rpm) for 10 min, and then ultrasonically dispersing for 5 min, and dispersing at a temperature range of 0-10° C., to obtain a catalyst slurry;

[0055] The catalyst slurry was then scraped onto both sides of the Zirfon220 membrane (thickness 220 μm) at a speed of 60 mm / s, and then vacuum dried at 80°C for 30 min. After that, a PTFE membrane was selected as a protective membrane, and the protective membrane was laid between the hot pressing plate and the catalyst slurry layer of the flat hot press, and hot pressed at 120°C and 5 MPa for 3 min. After cooling, the protective membrane was removed to obtain a membrane electrode for alkaline water electrolysis. The catalyst layer thickness of the obtained membrane electrode was about 5 μm.

[0056] The membrane electrode was assembled into an electrolytic cell and tested at 0.4 A / cm 2 and 0.8A / cm 2 Water electrolysis voltage under current density, test results are shown in Figure 3 . The surface of the membrane electrode was observed after the test. The coating on the membrane electrode surface was intact and the catalyst did not fall off, indicating that the coating had good firmness.

[0057] Embodiment 4:

[0058] The process is carried out in accordance with Example 1, except that the Nafion solution used has a mass fraction of 5 wt %.

[0059] The membrane electrode obtained in this example was assembled into an electrolytic cell and tested at 0.4 A / cm 2 and 0.8A / cm 2 Water electrolysis voltage under current density, test results are shown in Figure 3 . The surface of the membrane electrode was observed after the test. The coating on the membrane electrode surface was intact and the catalyst did not fall off, indicating that the coating had good firmness.

[0060] Embodiment 5:

[0061] The process is carried out in accordance with Example 1, except that the mass ratio of the binder solution to the catalyst is 1:1.

[0062] The membrane electrode obtained in this example was assembled into an electrolytic cell and tested at 0.4 A / cm 2 and 0.8A / cm 2 Water electrolysis voltage under current density, test results are shown in Figure 3 . The surface of the membrane electrode was observed after the test. The membrane electrode surface coating was intact and the catalyst did not fall off, indicating that the coating had good firmness.

[0063] Embodiment 6:

[0064] The same method as in Example 2 was used, except that the mass ratio of the binder solution to the catalyst was 4:1. The membrane electrode obtained in this example was assembled into an electrolytic cell and tested for its 2 and 0.8A / cm 2 Water electrolysis voltage under current density, test results are shown in Figure 3 . The surface of the membrane electrode was observed after the test. The coating on the membrane electrode surface was intact and the catalyst did not fall off, indicating that the coating had good firmness.

[0065] Comparative Example 1:

[0066] The process is carried out in accordance with Example 1, except that a Nafion solution having a mass fraction of 2.5 wt % is used.

[0067] The membrane electrode obtained in this comparative example was assembled into an electrolytic cell and tested at 0.4 A / cm 2 and 0.8A / cm 2 Water electrolysis voltage under current density. Test results are shown in Figure 3 . Observe and take photos of the surface of the membrane electrode after the test, such as Figure 2 As shown, from Figure 2 It can be seen that the catalyst on the membrane electrode surface has fallen off severely, indicating that the catalyst layer has poor firmness.

[0068] Comparative Example 2:

[0069] The process is carried out in accordance with Example 1, except that the mass ratio of the binder solution to the catalyst is 0.5:1.

[0070] The membrane electrode obtained in this comparative example was assembled into an electrolytic cell and tested at 0.4 A / cm 2 and 0.8A / cm 2 Water electrolysis voltage under current density. Test results are shown in Figure 3 . The surface of the membrane electrode after the test was observed, and it was found that the catalyst layer on the surface of the membrane electrode had fallen off, and the firmness of the catalyst layer was poor.

[0071] Comparative Example 3:

[0072] The process is carried out in accordance with Example 2, except that the mass ratio of the binder solution to the catalyst is 4.5:1.

[0073] The membrane electrode obtained in this comparative example was assembled into an electrolytic cell and tested at 0.4 A / cm 2 and 0.8A / cm 2 Water electrolysis voltage under current density. Test results are shown in Figure 3 .

[0074] Comparative Example 4:

[0075] The same method as in Example 1 was used, except that hydrophilic PTFE was used as the protective film during the hot pressing process. After hot pressing and cooling, the protective film was removed. It was found that the protective film was not completely peeled off. After peeling off the protective film, the membrane electrode obtained had a large amount of protective film on its surface. Figure 4 .

[0076] Comparative Example 5

[0077] The method was carried out in accordance with Example 2, except that, during the preparation of the catalyst slurry, the dispersion temperature was not controlled within the range of 0-10° C., but was 40° C. Under this condition, the slurry was severely solidified, and the solvent would evaporate rapidly due to the high temperature, resulting in uneven dispersion of the slurry.

[0078] The present invention performs hot pressing during the preparation of the membrane electrode, which can improve the firmness of the catalyst layer. Example 1 is used as a representative example. Figure 8 The photo is a photo of the catalyst layer surface before hot pressing during the membrane electrode preparation process in Example 1, and the photo is a photo of the catalyst layer surface after hot pressing. Figure 1 Similarly, it can be seen that the uniformity and firmness of the catalyst layer can be significantly improved after hot pressing.

[0079] The catalyst layers on both sides of the membrane electrode obtained in Examples 1-6 were photographed under a polarizing microscope. Taking the photograph obtained in Example 2 as an example, the catalyst layer formed by the catalyst slurry II is as follows: Figure 5 As shown, it can be seen that the catalyst layer is evenly distributed. The catalyst layer formed by catalyst slurry I is similar to that of catalyst slurry II, which will not be repeated here. The catalyst layers of the membrane electrodes of other embodiments of the present invention were photographed under a polarizing microscope. The results are similar to those of Example 2. The catalyst layers are evenly distributed. In Comparative Examples 2, 3, and 5, the catalyst layers are unevenly distributed. Comparative Example 5 is used as an example to show the results. The results of the catalyst layer formed by catalyst slurry II are shown in FIG. Fig. 9 As shown, it can be seen that the catalyst layer is unevenly distributed.

[0080] The membrane electrode obtained in Examples 1-6 of the present invention was subjected to a firmness test in an adhesive strength analyzer. The test method was as follows: a double-sided adhesive was used to stick the sample to the test base so that the detector could record the critical force / strength at the moment of separation of the coating. The photos after the test were as follows: Figure 6 As shown, it is a diagram of the firmness test results of Example 3. Figure 6 It can be seen that the black catalyst coating was not peeled off separately, but the surface layer of the diaphragm loaded with the catalyst coating (i.e., the exposed white part in the figure) was peeled off, which shows that the catalyst coating has a high adhesion to the base diaphragm, indicating that the catalyst coating has good firmness; the test results of the other embodiments are similar to those of Example 3, and will not be repeated. However, the catalyst coating on the membrane electrode surface of the membrane electrode of Comparative Examples 1-2, 4-5 is very easy to fall off after being applied by hand, indicating that the coating has poor firmness. Taking Comparative Example 1 as an example, the results are as follows Fig.10 As shown, the membrane electrode prepared in the embodiment of the present invention has no peeling phenomenon when smeared by hand.

[0081] The membrane electrode obtained in Examples 1-6 of the present invention is subjected to 0.4A / cm 2 The stability test was carried out under the reaction current density of , the test method was: the electrolyte was a 30% KOH solution by mass, the reaction temperature was 80±3℃. The reaction current was 10A, and the test time was 1000h. After the test, it was found that: the membrane electrode surface coating remained intact, and the voltage decay rate was low; Figure 7 The stability test result of Example 1 is shown in the figure, and its voltage decay rate is 2.4μV / h. The other examples are similar to Example 1, and have basically the same voltage decay rate level (all within the level of 1-10μV / h). Comparative Examples 1-3 were tested for stability. The test method was based on the test method of the previous Examples 1-6. The difference was that due to the poor stability of the comparative examples, the test time only lasted for 320 hours. The results showed that: the voltage decay rate was relatively high, reaching the level of 1-10mV / h. Taking Comparative Example 1 as an example, the results are as follows: Fig.11 As shown, its voltage decay rate is 0.35mV / h.

[0082] It is easy to understand that the above embodiments are only examples for clear explanation and do not mean that the present invention is limited thereto. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the protection scope of the present invention.

Claims

1. A method for preparing a membrane electrode for producing hydrogen by alkaline water electrolysis, It is characterized in that The preparation method comprises the following steps: Directly coating the catalyst slurry on both sides of the diaphragm, and forming catalyst layers on both sides of the diaphragm after drying and hot pressing to obtain the membrane electrode; the hot pressing conditions include: hot pressing temperature of 80-180° C. and pressure of 3-10 MPa; The diaphragm is selected from a porous diaphragm or an alkaline anion exchange membrane; The catalyst slurry is composed of a binder solution and a catalyst, wherein the binder solution is one or more of a perfluorosulfonic acid resin solution and a perfluorosulfonic acid ionomer dispersion, and the mass concentration of the binder solution is 5-30%; the mass ratio of the binder solution to the catalyst is 1:1-4:1; The solvent in the binder solution is a mixed solvent of water and an organic solvent, wherein the organic solvent is selected from one or more of methanol, ethanol, n-propanol, isopropanol, and polyethylene glycol; the mass ratio of the water to the organic solvent is 0.5:1 to 1:

1.

2. The preparation method according to claim 1, It is characterized in that The thickness of the separator is 100-500 μm.

3. The preparation method according to claim 1, It is characterized in that The mass concentration of the binder solution is 5-20%.

4. The preparation method according to claim 1, It is characterized in that The porous membrane is selected from polysulfone, polyethersulfone, polyvinyl chloride or polyphenylene sulfide porous membrane; And / or, the alkaline anion exchange membrane is selected from a quaternary ammonium salt anion exchange membrane, a polyethersulfone anion exchange membrane or a polyphenylene ether anion exchange membrane; And / or, the particle size of the catalyst is 100 μm or less.

5. The preparation method according to claim 4, It is characterized in that The particle size of the catalyst is less than 40 μm.

6. The preparation method according to any one of claims 1 to 5, It is characterized in that The mass fraction of the binder solution is 5-20%; the mass ratio of the binder solution to the catalyst is 1:1-4:

1.

7. The preparation method according to claim 6, It is characterized in that The mass fraction of the binder solution is 5-10%; the mass ratio of the binder solution to the catalyst is 1:1-2:

1.

8. The preparation method according to any one of claims 1 to 5, It is characterized in that The thickness of the catalyst layer is 2-50 μm.

9. The preparation method according to claim 8, It is characterized in that The thickness of the catalyst layer is ≥3 μm and <10 μm.

10. The preparation method according to any one of claims 1 to 5, It is characterized in that The catalyst is selected from materials having hydrogen evolution catalytic activity or oxygen evolution catalytic activity.

11. The preparation method according to any one of claims 1 to 5, It is characterized in that The method further comprises the following operations: after the drying is completed, applying a hydrophobic protective film on the surface of the coating layer formed by the catalyst slurry, then performing the hot pressing, and peeling off the hydrophobic protective film after the hot pressing is completed.

12. The preparation method according to claim 11, It is characterized in that The hydrophobic protective film is selected from aluminum foil, copper foil, tin foil, polytetrafluoroethylene film, polyethylene terephthalate film, PET film with organic silicon coating on the surface, and PTFE film with PET or polypropylene support.

13. The preparation method according to any one of claims 1 to 5, It is characterized in that The conditions of the hot pressing include: hot pressing time 1-10min; The drying conditions include: drying temperature 60-150°C, drying time 10-240min; The coating conditions include: a coating speed of 20-100 mm / s.

14. The preparation method according to claim 13, It is characterized in that The hot pressing temperature is 120-160° C., the pressure is 5-8 MP, and the hot pressing time is 3-5 min; the drying temperature is 80-120° C., and the drying time is 30-60 min; and the coating speed is 20-60 mm / s.

15. The preparation method according to any one of claims 1 to 5, It is characterized in that The steps of preparing the catalyst slurry include: After the binder solution and the catalyst are mixed, they are first dispersed by a homogenizer for 5-30 minutes, and then ultrasonically dispersed for 1-10 minutes. The dispersion is carried out at a temperature of 0-10°C.

16. A membrane electrode for producing hydrogen by alkaline water electrolysis, It is characterized in that The membrane electrode is prepared by the preparation method described in any one of claims 1 to 15.

17. An electrolyzer for producing hydrogen by alkaline electrolysis of water, It is characterized in that The membrane electrode is the membrane electrode as claimed in claim 16.

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