Composite diaphragm electrode for alkaline water electrolysis and preparation method and application thereof

Abstract

The present invention provides a composite diaphragm electrode for alkaline water electrolysis, and its preparation method and application. The composite diaphragm electrode comprises a catalyst layer A, a skin layer, a finger-shaped porous layer, a three-dimensional porous layer, and a catalyst layer B, which are sequentially connected; wherein the three-dimensional porous layer contains a support. The present invention first adopts a unique heterogeneous structure design of the skin layer, the finger-shaped porous layer, and the three-dimensional porous layer to obtain an alkaline water electrolysis diaphragm with an ultra-high bubble point, and the diaphragm has extremely low surface resistance, hydrophilicity, and ultra-fast wettability. The water electrolysis catalyst and the diaphragm are then directly coupled together to prepare a diaphragm electrode for use in the alkaline water electrolysis process. This electrode effectively reduces the interfacial resistance generated by the separation of the catalyst layer and the diaphragm in traditional alkaline water electrolysis processes, thereby effectively increasing the current density of the water electrolysis process.

Description

Technical Field

[0001] The present invention relates to the technical field of alkaline water electrolysis, and in particular to a composite diaphragm electrode for alkaline water electrolysis, a preparation method thereof, and applications thereof. Background Art

[0002] With the continuous development of the global economy and the increase in population, humanity's demand for energy is increasing. At the same time, environmental protection cannot be neglected. Therefore, people are urgently seeking a new energy system that is not dependent on chemical fuels, has abundant reserves, and is clean. As one of the important energy carriers of the future, clean hydrogen energy has broad application prospects. Among them, alkaline water electrolysis is a key means of achieving large-scale hydrogen production due to its relatively mature technology, simple operation, low corrosion to equipment, and high-purity hydrogen produced.

[0003] Two electrodes (anode and cathode) with direct current are immersed in an electrolyte. Water is decomposed, producing H₂ and O₂ at the cathode and anode, respectively. A separator is placed between the cathode and anode to prevent the H₂ and O₂ from mixing. This process is called water electrolysis, and such a device is called an electrolyzer. The electrolyte is generally a 25%-30% potassium hydroxide or sodium hydroxide solution.

[0004] An ideal diaphragm for alkaline water electrolysis should have good ion permeability, mechanical strength, air tightness, electrical insulation, and suitable electrolyte permeability. Among them, ion permeability directly affects the electrolysis efficiency of the alkaline water electrolyzer of the diaphragm used. Improving the ion permeability of the diaphragm can reduce the surface resistance of the diaphragm, thereby improving the electrolysis efficiency of the alkaline water electrolyzer. Mechanical strength requires the diaphragm to have good mechanical strength so that it can withstand the friction between the electrodes and the diaphragm of the electrolyzer. Air tightness requires the diaphragm to have the ability to block gas, and the gas generated by electrolysis cannot pass through the diaphragm, that is, the diaphragm only allows ions to pass through. Electrical insulation means that the diaphragm cannot conduct electricity and needs to be in an insulating state. However, there are almost no diaphragms for alkaline water electrolysis in the prior art that can take into account all of the above-mentioned properties.

[0005] In addition, in order to improve the efficiency of hydrogen production, catalysts are set at the cathode and anode respectively in actual production, distributed on both sides of the diaphragm. However, there is no close contact between the catalyst and the diaphragm, and there are certain pores, which increases the resistance to ion transmission, resulting in a decrease in the current density of the water electrolysis process, and the speed-up effect is not ideal. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention provides a composite diaphragm electrode for alkaline water electrolysis, and a preparation method and application thereof.

[0007] In a first aspect, the present invention provides a composite diaphragm electrode for alkaline water electrolysis, comprising a catalyst layer A, a skin layer, a finger-shaped porous layer, a three-dimensional porous layer and a catalyst layer B connected in sequence; wherein the three-dimensional porous layer contains a support.

[0008] According to the composite diaphragm electrode for alkaline water electrolysis provided by the present invention, one of the catalyst layer A and the catalyst layer B is NiFe-LDH and the other is Co2MnO4, and the thicknesses thereof are both controlled to be 5 to 10 μm.

[0009] According to the composite diaphragm electrode for alkaline water electrolysis provided by the present invention, the average pore diameters of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer are 30-50 nm, 300-500 nm and 100-200 nm respectively.

[0010] According to the composite diaphragm electrode for alkaline water electrolysis provided by the present invention, the width of the finger-shaped pores of the finger-shaped porous layer is 2 to 10 μm.

[0011] According to the composite diaphragm electrode for alkaline water electrolysis provided by the present invention, the thicknesses of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer are 1-5 μm, 200-250 μm and 100-150 μm respectively.

[0012] According to the composite diaphragm electrode for alkaline water electrolysis provided by the present invention, the skin layer comprises 3 to 9 parts by mass of inorganic nanoparticles, 80 to 90 parts by mass of organic high molecular polymer and 0.1 to 0.5 parts by mass of a binder.

[0013] According to the composite diaphragm electrode for alkaline water electrolysis provided by the present invention, the finger-shaped porous layer and the three-dimensional porous layer both contain 40 to 60 parts of inorganic nanoparticles, 40 to 60 parts of organic high molecular polymers and 0.1 to 0.5 parts of a binder.

[0014] According to the composite diaphragm electrode for alkaline water electrolysis provided by the present invention, the inorganic nanoparticles are one or a combination of strontium titanate and barium titanate; and the size is 10 to 200 nm.

[0015] According to the composite diaphragm electrode for alkaline water electrolysis provided by the present invention, the organic high molecular polymer is one or more of polyethersulfone, polysulfone, polyetheretherketone, and chitosan.

[0016] According to the composite diaphragm electrode for alkaline water electrolysis provided by the present invention, the support body is one or more of PP net, PPS net, PP non-woven fabric, and PPS non-woven fabric.

[0017] According to the composite diaphragm electrode for alkaline water electrolysis provided by the present invention, the fiber diameter of the support body is 50 to 150 μm, and the pore diameter of the support body is 100 to 400 μm.

[0018] In a second aspect, the present invention further provides a method for preparing the composite diaphragm electrode for alkaline water electrolysis, comprising:

[0019] Mixing inorganic nanoparticles, organic high molecular polymer, binder and solvent to prepare a casting solution;

[0020] The support is completely immersed in the casting liquid, and the casting liquid on one side of the support is scraped flat to prepare a wet membrane; the membrane is pre-evaporated, and then the membrane is immersed in a mixed solution of water and an organic solvent. Through a phase inversion process, a rapid phase inversion occurs on the surface to form a dense cortical structure, and delayed phase separation occurs inside, gradually forming a finger-shaped porous layer and a three-dimensional porous layer from the surface to the inside, forming a membrane with a porous structure;

[0021] After the diaphragm is prepared, the catalyst is coupled to the diaphragm.

[0022] According to the preparation method provided by the present invention, the catalyst and the diaphragm are coupled by spraying, ion sputtering or electrodeposition.

[0023] In a third aspect, the present invention further provides an alkaline water electrolysis device, comprising any of the above-mentioned composite diaphragm electrodes for alkaline water electrolysis.

[0024] The present invention provides a composite diaphragm electrode for alkaline water electrolysis, and a preparation method and application thereof. First, by adopting a special heterogeneous structure design such as a skin layer, a finger-shaped porous layer, and a three-dimensional porous layer, a diaphragm for alkaline water electrolysis with an ultra-high bubble point is obtained. The diaphragm also has extremely low surface resistance, hydrophilicity, and ultra-fast wettability. Then, a water electrolysis catalyst is directly coupled with the diaphragm to prepare a diaphragm electrode for the alkaline water electrolysis process. This can effectively reduce the resistance generated by the separation of the catalyst layer and the diaphragm in the traditional alkaline water electrolysis process, thereby effectively improving the current density of the water electrolysis process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the structure of the diaphragm prepared in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0028] In a first aspect, the present invention provides a composite diaphragm electrode for alkaline water electrolysis, comprising a catalyst layer A, a skin layer, a finger-shaped porous layer, a three-dimensional porous layer and a catalyst layer B connected in sequence; wherein the three-dimensional porous layer contains a support.

[0029] The present invention adopts a special heterogeneous structure design of a cortex, a finger-shaped porous layer, and a three-dimensional porous layer, which not only produces an alkaline water electrolysis membrane with an ultra-high bubble point, but also has extremely low surface resistance, hydrophilicity, and ultra-fast wettability. The provision of a support body in the three-dimensional porous layer can effectively enhance the mechanical strength of the alkaline water electrolysis membrane. At the same time, the present invention directly couples the electrolysis catalyst to the membrane, effectively reducing the interfacial resistance generated by the separation of the catalyst layer and the membrane during traditional alkaline water electrolysis, thereby effectively improving the current density of the water electrolysis process.

[0030] In some embodiments of the present invention, one of the catalyst layer A and the catalyst layer B is NiFe-LDH and the other is Co2MnO4, and the thicknesses of both are controlled to be 5-10 μm.

[0031] The catalyst NiFe-LDH can effectively promote hydrogen production, and the catalyst Co2MnO4 can effectively promote oxygen production. In an embodiment of the present invention, the catalyst layer A can be set to NiFe-LDH, and the catalyst layer B can be set to Co2MnO4. The catalyst layer A can also be set to Co2MnO4, and the catalyst layer B can be set to NiFe-LDH. At that time, it is ensured that the catalyst Co2MnO4 is connected to the positive pole of the power supply, and the catalyst NiFe-LDH is connected to the negative pole of the power supply.

[0032] In some embodiments of the present invention, the support body is distributed in the three-dimensional porous layer in a manner of being horizontally embedded in the three-dimensional porous layer, and its area is equal to the horizontal cross-sectional area of ​​the three-dimensional porous layer.

[0033] In some embodiments of the present invention, the average pore diameters of the skin layer, the finger-shaped porous layer, and the three-dimensional porous layer are 30-50 nm, 300-500 nm, and 100-200 nm, respectively.

[0034] In some embodiments of the present invention, the width of the finger-shaped pores of the finger-shaped porous layer is 2-10 μm.

[0035] The present invention has found that by setting the average pore diameter of the skin layer, the finger-like porous layer and the three-dimensional porous layer and the finger-like pore width of the finger-like porous layer within the above range, gas barrier properties can be achieved without hindering ion transmission.

[0036] In some embodiments of the present invention, the thicknesses of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer are 1-5 μm, 200-250 μm and 100-150 μm respectively.

[0037] The present invention controls the thickness of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer within the above range, thereby controlling the overall thickness of the composite diaphragm within the range of about 400 μm, which is beneficial to reducing the diaphragm resistance.

[0038] In some embodiments of the present invention, the skin layer comprises, by weight, 3 to 9 parts of inorganic nanoparticles, 80 to 90 parts of organic high molecular polymer, and 0.1 to 0.5 parts of a binder.

[0039] In some embodiments of the present invention, the finger-shaped porous layer and the three-dimensional porous layer each contain 40 to 60 parts of inorganic nanoparticles, 40 to 60 parts of organic high molecular polymers, and 0.1 to 0.5 parts of a binder.

[0040] It should be noted that, in a specific embodiment, the compositions of the finger-shaped porous layer and the three-dimensional porous layer do not have to be completely the same, and can be within the above ranges.

[0041] In some embodiments of the present invention, the inorganic nanoparticles are one or a combination of strontium titanate and barium titanate, and have a size of 10 to 200 nm.

[0042] In the prior art, inorganic nanoparticles are generally selected from one or more of aluminum oxide, zirconium oxide, silicon oxide, and zinc oxide. The present invention selects one or a combination of strontium titanate and barium titanate, which has the advantage of longer-term stability.

[0043] In some embodiments of the present invention, the organic high molecular polymer is one or more of polyethersulfone, polysulfone, polyetheretherketone, and chitosan.

[0044] In some embodiments of the present invention, the binder is one or more of polyvinyl pyrrolidone (PVP) and polyvinyl alcohol (PVA).

[0045] In some embodiments of the present invention, the support body is one or more of PP net, PPS net, PP non-woven fabric, and PPS non-woven fabric.

[0046] The PP mesh described herein is a mesh woven from polypropylene fibers. Polypropylene fibers are synthetic fibers spun from isotactic polypropylene obtained by propylene polymerization. Polypropylene fibers are characterized by light weight, high strength, good elasticity, corrosion resistance, and electrical insulation.

[0047] The PPS mesh described in this invention is woven from polyphenylene sulfide fibers. Polyphenylene sulfide fibers are produced by melt spinning polyphenylene sulfide. They are amber in color, have a strength of 0.18-0.26 N / tex, an elongation of 25-35%, and an initial modulus of 2.65-3.53 N / tex. They exhibit excellent heat resistance and are primarily used as high-temperature filter fabrics, with a temperature tolerance of up to 190°C. The fibers also exhibit excellent resistance to chemicals and hydrolysis, as well as flame retardancy.

[0048] In some embodiments of the present invention, the fiber diameter of the support body is 50-150 μm, and the pore size of the support body is 100-400 μm.

[0049] Furthermore, in some embodiments of the present invention, the support body is in a mesh shape, the fiber diameter thereof is 150 μm, and the pore size of the support body is 400 μm.

[0050] In a second aspect, the present invention provides a method for preparing the composite diaphragm electrode for alkaline water electrolysis.

[0051] The preparation method provided by the present invention comprises: mixing inorganic nanoparticles, organic high molecular polymer, binder and solvent to prepare a casting solution;

[0052] The support is completely immersed in the casting liquid, and the casting liquid on one side of the support is scraped flat to prepare a wet membrane; the membrane is pre-evaporated, and then the membrane is immersed in a mixed solution of water and an organic solvent. Through a phase inversion process, a rapid phase inversion occurs on the surface to form a dense cortical structure, and delayed phase separation occurs inside, gradually forming a finger-shaped porous layer and a three-dimensional porous layer from the surface to the inside, forming a membrane with a porous structure;

[0053] After the diaphragm is prepared, the catalyst is coupled to the diaphragm.

[0054] Wherein, the solvent is selected from one or more of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, and acetonitrile.

[0055] Furthermore, the catalyst is coupled to the membrane by spraying, ion sputtering or electrodeposition.

[0056] In a third aspect, the present invention provides the use of the composite diaphragm electrode for alkaline water electrolysis in electrolyzing water.

[0057] For example, the present invention provides an alkaline water electrolysis device, comprising any of the above-mentioned composite diaphragm electrodes for alkaline water electrolysis.

[0058] Specifically, the alkaline water electrolysis device of the present invention includes, in addition to the above-mentioned composite diaphragm electrode, an electrode plate with an electrolyte flow channel engraved on the electrode plate, and a gasket. The composite diaphragm electrode is pressed tightly by the electrode plates on both sides through the gasket. When power is applied, hydrogen is generated on the cathode side and oxygen is generated on the anode side.

[0059] The alkaline water electrolysis device of the present invention adopts the above-mentioned composite diaphragm electrode, which can improve the electrolysis efficiency of the alkaline water electrolysis device and has high safety. At the same time, it can effectively reduce the interfacial resistance generated by the separation of the catalyst layer and the diaphragm in the traditional alkaline water electrolysis process, thereby effectively improving the current density of the water electrolysis process.

[0060] The following are specific examples. Unless otherwise specified, all raw materials used were obtained through regular commercial channels.

[0061] Example 1

[0062] This embodiment provides a composite diaphragm electrode for alkaline water electrolysis, which is composed of a catalyst layer A, a skin layer, a finger-shaped porous layer, a three-dimensional porous layer, and a catalyst layer B connected in sequence; wherein the three-dimensional porous layer contains a support.

[0063] Specifically, catalyst layer A is NiFe-LDH with a thickness of 5 μm; catalyst layer B is Co2MnO4 with a thickness of 5 μm;

[0064] The average pore sizes of the skin layer, finger-shaped porous layer and three-dimensional porous layer are 30 nm, 300 nm and 100 nm respectively; the width of the finger-shaped pores in the finger-shaped porous layer is 2 μm;

[0065] The thicknesses of the skin layer, finger-like porous layer, and three-dimensional porous layer are 3 μm, 200 μm, and 100 μm, respectively;

[0066] The support is a PP mesh, the diameter of the PP fiber is 150 μm, the pore size of the PP mesh is 400 μm, and the support is embedded in the three-dimensional porous layer, with an area equal to the horizontal cross-sectional area of ​​the three-dimensional porous layer.

[0067] The skin layer contains 3 parts by mass of inorganic nanoparticles (strontium titanate, particle size 100 nm), 90 parts of organic polymer (polyethersulfone) and 0.5 parts of binder (polyvinyl alcohol);

[0068] The finger-shaped porous layer and the three-dimensional porous layer each contain 50 parts of inorganic nanoparticles (strontium titanate, particle size 100 nm), 50 parts of organic high molecular polymer (polyethersulfone) and 0.5 parts of binder (polyvinyl alcohol).

[0069] The preparation method is as follows:

[0070] S1. Prepare the casting solution components: polyethersulfone (5% by mass), strontium titanate (43% by mass), polyvinyl alcohol (2% by mass), and solvent (NMP, 50% by mass);

[0071] S2: The components of the casting solution in S1 were mixed and stirred for 10 h, and then the support was completely immersed in the casting solution. Then, a membrane manufacturing device (MSK-AFA-L1000 doctor blade, the same below) was used to scrape the casting solution on one side of the support flat with a flat blade to prepare a wet composite membrane; the gap between the blades was set to 400 μm;

[0072] S3. The wet composite membrane was evaporated for 10 minutes and then placed in a phase inversion solution for phase inversion at 20°C; the phase inversion solution was composed of a mixture of water and NMP (1:1 volume ratio) and the phase inversion time was 10 seconds. During the phase inversion process, rapid phase inversion occurred on the surface, forming a dense cortical structure, while delayed phase separation occurred within the membrane, gradually forming a finger-like porous layer and a three-dimensional porous layer from the surface to the interior, thereby forming a porous structure.

[0073] S4, after the phase inversion, the membrane is dried, cut and stored to obtain a diaphragm;

[0074] S5. Use a spraying method to spray the catalyst layer A onto the surface of the skin layer, and spray the catalyst layer B onto the surface of the three-dimensional porous layer.

[0075] The structural diagram of the composite diaphragm electrode obtained in this embodiment is shown in FIG. Figure 1 shown.

[0076] Example 2

[0077] This embodiment provides a composite diaphragm electrode for alkaline water electrolysis, which is composed of a catalyst layer A, a skin layer, a finger-shaped porous layer, a three-dimensional porous layer, and a catalyst layer B connected in sequence; wherein the three-dimensional porous layer contains a support.

[0078] Specifically, catalyst layer A is NiFe-LDH with a thickness of 5 μm; catalyst layer B is Co2MnO4 with a thickness of 8 μm;

[0079] The average pore sizes of the skin layer, finger-shaped porous layer, and three-dimensional porous layer are 35 nm, 357 nm, and 140 nm, respectively; the width of the finger-shaped pores in the finger-shaped porous layer is 2 μm;

[0080] The thicknesses of the skin layer, finger-like porous layer, and three-dimensional porous layer are 3 μm, 200 μm, and 100 μm, respectively;

[0081] The support body is a PP mesh, the diameter of the PP fiber is 150 μm, the pore size of the PP mesh is 400 μm, and the support body is embedded in the three-dimensional porous layer.

[0082] The skin layer contains 9 parts by mass of inorganic nanoparticles (barium titanate, particle size 200 nm), 80 parts by mass of organic polymer (polysulfone), and 0.3 parts by mass of binder (polyvinyl alcohol).

[0083] The finger-shaped porous layer and the three-dimensional porous layer each contain 60 parts of inorganic nanoparticles (barium titanate, particle size 200 nm), 40 parts of organic high molecular polymer (polysulfone) and 0.5 parts of binder (polyvinyl alcohol).

[0084] The preparation method is as follows:

[0085] S1. Prepare the casting solution components: polysulfone (5% by mass), barium titanate (43% by mass), polyvinyl alcohol (2% by mass), and solvent (NMP, 50% by mass);

[0086] S2: The components of the casting solution in S1 were mixed and stirred for 10 h, and then the support was completely immersed in the casting solution. Then, a membrane manufacturing device (MSK-AFA-L1000 doctor blade, the same below) was used to scrape the casting solution on one side of the support flat with a flat blade to prepare a wet composite membrane; the gap between the blades was set to 400 μm;

[0087] S3. The wet composite membrane was evaporated for 10 minutes and then placed in a phase inversion solution for phase inversion at 20°C; the phase inversion solution was composed of a mixture of water and NMP (1:1 volume ratio) and the phase inversion time was 10 seconds. During the phase inversion process, rapid phase inversion occurred on the surface, forming a dense cortical structure, while delayed phase separation occurred within the membrane, gradually forming a finger-like porous layer and a three-dimensional porous layer from the surface to the interior, thereby forming a porous structure.

[0088] S4, after the phase inversion, the membrane is dried, cut and stored to obtain a diaphragm;

[0089] S5. Using an electrodeposition method, a catalyst layer A is formed on the surface of the skin layer, and a catalyst layer B is formed on the surface of the three-dimensional porous layer.

[0090] Example 3

[0091] This embodiment provides a composite diaphragm electrode for alkaline water electrolysis, which is composed of a catalyst layer A, a skin layer, a finger-shaped porous layer, a three-dimensional porous layer, and a catalyst layer B connected in sequence; wherein the three-dimensional porous layer contains a support.

[0092] Specifically, catalyst layer A is Co2MnO4 with a thickness of 8 μm; catalyst layer B is NiFe-LDH with a thickness of 5 μm;

[0093] The average pore sizes of the skin layer, finger-shaped porous layer, and three-dimensional porous layer are 40 nm, 300 nm, and 134 nm, respectively; the width of the finger-shaped pores in the finger-shaped porous layer is 2 μm;

[0094] The thicknesses of the skin layer, finger-like porous layer, and three-dimensional porous layer are 3 μm, 200 μm, and 100 μm, respectively;

[0095] The support body is a PP mesh, the diameter of the PP fiber is 150 μm, the pore size of the PP mesh is 400 μm, and the support body is embedded in the three-dimensional porous layer.

[0096] The skin layer contains 6 parts by mass of inorganic nanoparticles (strontium titanate, particle size 10 nm), 85 parts of organic polymer (polyetheretherketone), and 0.5 parts of binder (polyvinylpyrrolidone);

[0097] The finger-shaped porous layer and the three-dimensional porous layer both contain 40 parts of inorganic nanoparticles (strontium titanate, particle size 10 nm), 60 parts of organic high molecular polymer (polyetheretherketone) and 0.5 parts of binder (polyvinylpyrrolidone).

[0098] The preparation method is as follows:

[0099] S1. Prepare the casting solution components: polyetheretherketone (5% by mass), strontium titanate (43% by mass), polyvinylpyrrolidone (2% by mass) and solvent (NMP, 50% by mass);

[0100] S2: The components of the casting solution in S1 were mixed and stirred for 10 h, and then the support was completely immersed in the casting solution. Then, a membrane manufacturing device (MSK-AFA-L1000 doctor blade, the same below) was used to scrape the casting solution on one side of the support flat with a flat blade to prepare a wet composite membrane; the gap between the blades was set to 400 μm;

[0101] S3. The wet composite membrane was evaporated for 10 minutes and then placed in a phase inversion solution for phase inversion at 20°C; the phase inversion solution was composed of a mixture of water and NMP (1:1 volume ratio) and the phase inversion time was 10 seconds. During the phase inversion process, rapid phase inversion occurred on the surface, forming a dense cortical structure, while delayed phase separation occurred within the membrane, gradually forming a finger-like porous layer and a three-dimensional porous layer from the surface to the interior, thereby forming a porous structure.

[0102] S4, after the phase inversion, the membrane is dried, cut and stored to obtain a diaphragm;

[0103] S5. Using an ion sputtering method, a catalyst layer A is formed on the surface of the skin layer, and a catalyst layer B is formed on the surface of the three-dimensional porous layer.

[0104] Comparative Example 1

[0105] This comparative example provides a composite diaphragm for alkaline water electrolysis, PPS was purchased from TORAY.

[0106] Comparative Example 2

[0107] This comparative example provides a composite diaphragm for alkaline water electrolysis, which is ZIRFON PERL UTP 500, purchased from Agfa-Gevaert.

[0108] Comparative Example 3

[0109] This comparative example provides a composite diaphragm for alkaline water electrolysis, and its preparation method is as follows:

[0110] S1. Prepare the casting solution components: polyarylethersulfone (mass fraction 2%), nanozirconia (particle size 20 nm, mass fraction 90%), and N-methylpyrrolidone (NMP, mass fraction 8%);

[0111] S2, first mixing and stirring the casting solution components in S1 for 40 hours, then completely immersing the support in the casting solution, and then using a membrane manufacturing device to scrape the casting solution on one side of the support using a flat scraper to prepare a wet composite membrane; the gap between the scrapers is set to 500 microns;

[0112] In this embodiment, the support body is made of a polypropylene fiber mesh with a fiber diameter of 30 microns and a mesh width of 800 microns. The area of ​​the support body is consistent with the area of ​​the diaphragm.

[0113] S3. Place the wet composite membrane in a phase inversion solution at 40°C for phase inversion, consisting of a mixture of water and NMP (1:1 volume ratio) for 20 seconds. During this process, the organic polymer resin in the casting solution solidifies, the solvent dissolves in the water, and the polymer resin and solvent undergo phase separation, forming a porous structure.

[0114] S4. After the phase inversion, the membrane is dried, cut and preserved to obtain a diaphragm.

[0115] Performance Testing

[0116] (1) The performance of the composite membrane electrode of the embodiment and the composite membrane of the comparative example were tested, and the results are shown in Table 1.

[0117] Among them, the test method of surface resistance is as follows:

[0118] The separator was cut into small pieces and soaked in 30 wt% KOH solution for 1 day, and then the resistance was tested using an electrochemical workstation.

[0119] The bubble point test method is as follows:

[0120] Cut the membrane into small pieces, soak them with high-purity water, and place them in a bubble pressure membrane pore size analyzer (BSD-PB) for testing. Apply gas pressure to one side of the membrane. When a 1 mL / min airflow is detected on the other side of the membrane, this pressure is considered the bubble point of the membrane. The bubble point is calculated as follows:

[0121]

[0122] Where D = pore diameter, unit: μm; γ = surface tension of liquid, unit: dny / cm; θ = contact angle, unit: degree; △P = pressure difference, unit: KPa.

[0123] The breaking strength is tested using conventional testing methods in this field.

[0124] Table 1

[0125]

[0126] (2) The diaphragm was evaluated for pore size, tested for thickness, and calculated for porosity. The results are shown in Table 2.

[0127] Pore ​​size evaluation: The average pore size of the membrane is tested using the bubble point method, and high-purity water is used as the infiltration liquid;

[0128] Porosity calculation:

[0129] Porosity (%) = (weight of wet film - weight of dry film) / density of water / volume of wet film × 100.

[0130] Table 2

[0131]

[0132]

[0133] (3) The composite diaphragm electrode of Example 1 of the present invention was assembled into an alkaline water electrolysis device, and compared with the case where no catalyst coupling was performed (i.e., step S5 was not performed in Example 1, and the diaphragm was obtained and then assembled into an alkaline water electrolysis device in a conventional manner).

[0134] As a result, under the conditions of Example 1 of the present invention, the current density during the alkaline water electrolysis process was 1000 mA / cm 2 In the case of electrolysis, the electrolysis voltage is 1.7V, the purity of hydrogen produced by electrolysis is 99.98%, and the purity of oxygen is 99.91%.

[0135] Without catalyst coupling, during alkaline water electrolysis, at a current density of 1000 mA / cm 2 In this case, the electrolysis voltage is 1.93V, the purity of hydrogen produced by electrolysis is 99.94%, and the purity of oxygen is 99.83%.

[0136] It can be seen that under the same current density, the electrolysis voltage of the alkaline water electrolysis device of the present invention is lower, which means that the energy consumption is lower and the electrolysis efficiency is higher.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A composite diaphragm electrode for alkaline water electrolysis, characterized in that: It comprises a catalyst layer A, a skin layer, a finger-shaped porous layer, a three-dimensional porous layer and a catalyst layer B connected in sequence; wherein the three-dimensional porous layer contains a support; The catalyst layer A and the catalyst layer B are each made of NiFe-LDH and Co2MnO4, and their thicknesses are both controlled within a range of 5 to 10 μm. The average pore diameters of the skin layer, finger-shaped porous layer and three-dimensional porous layer are 30-50 nm, 300-500 nm and 100-200 nm respectively; The width of the finger-shaped pores of the finger-shaped porous layer is 2 to 10 μm; The thicknesses of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer are 1-5 μm, 200-250 μm and 100-150 μm respectively; The skin layer comprises, by weight, 3 to 9 parts of inorganic nanoparticles, 80 to 90 parts of organic high molecular polymer, and 0.1 to 0.5 parts of a binder; The finger-shaped porous layer and the three-dimensional porous layer each contain 40 to 60 parts of inorganic nanoparticles, 40 to 60 parts of organic high molecular polymers and 0.1 to 0.5 parts of a binder; The inorganic nanoparticles are one or a combination of strontium titanate and barium titanate; the size is 10 to 200 nm; The fiber diameter of the support body is 50 to 150 μm, and the pore diameter of the support body is 100 to 400 μm.

2. The composite diaphragm electrode for alkaline water electrolysis according to claim 1, characterized in that The organic high molecular polymer is one or more of polyethersulfone, polysulfone, polyetheretherketone and chitosan.

3. The composite diaphragm electrode for alkaline water electrolysis according to claim 1 or 2, characterized in that: The support body is one or more of PP net, PPS net, PP non-woven fabric, and PPS non-woven fabric.

4. The method for preparing the composite diaphragm electrode for alkaline water electrolysis according to any one of claims 1 to 3, characterized in that: include: Mixing inorganic nanoparticles, organic high molecular polymer, binder and solvent to prepare a casting solution; The support is completely immersed in the casting liquid, and the casting liquid on one side of the support is scraped flat to prepare a wet membrane; the membrane is pre-evaporated, and then the membrane is immersed in a mixed solution of water and an organic solvent. Through a phase inversion process, a rapid phase inversion occurs on the surface to form a dense cortical structure, and delayed phase separation occurs inside, gradually forming a finger-shaped porous layer and a three-dimensional porous layer from the surface to the inside, forming a membrane with a porous structure; After the diaphragm is prepared, the catalyst is coupled to the diaphragm.

5. The method for preparing a composite diaphragm electrode for alkaline water electrolysis according to claim 4, wherein: The catalyst is coupled to the membrane by spraying, ion sputtering or electrodeposition.

6. An alkaline water electrolysis device, characterized in that: The invention comprises the composite diaphragm electrode for alkaline water electrolysis according to any one of claims 1 to 3.

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