Composite electrode for electrolysis of water, preparation method and use thereof

Abstract

The application provides a composite electrode for electrolysis of water, the electrode comprising a titanium base body, an intermediate coating layer and a surface coating layer, raw materials for preparing the intermediate coating layer comprising: titanium oxide, nickel oxide, transition metal selenide and molybdenum carbide, and the surface coating layer being a noble metal coating layer; through optimization of the types and amounts of raw materials for the intermediate coating layer and the coating process, not only the catalytic performance of the electrode on water is improved, but also the amount of noble metal substances in the noble metal coating layer is effectively reduced; after the composite electrode prepared is used for electrolysis of water, the water has a high hydrogen content and selenium content, and can be used in preparation of electrolysis of water products.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrode water splitting, C09D5 / 44, and in particular to a composite electrode for water splitting, a preparation method and applications thereof. BACKGROUND

[0002] The existing electrodes mainly include lead electrodes, platinum electrodes, titanium electrodes, and coated titanium electrodes, among which the coated titanium electrodes have been widely studied due to their advantages. However, the existing coated titanium electrodes still have many defects, such as: (1) the electrodes are generally composed of a titanium base and a noble metal coating, and the noble metal coating is applied for more than 25 times, which requires a large amount of noble metal and results in high cost; (2) the catalytic performance is low, the amount of hydrogen produced is small, and the hydrogen production is uneven; (3) the electrodes are prone to failure and have a short service life; (4) the electrodes cannot meet the increasing demand for water quality, and the content of trace elements in water is low, and the water quality characteristics are not perfect, etc.

[0003] Chinese Patent CN102268688A discloses a ruthenium-palladium-cobalt coated titanium electrode with a tin-antimony intermediate layer, which has several layers of tin-antimony oxide coating as an intermediate layer on the surface of the titanium plate body. The components of the intermediate layer include ruthenium dioxide, palladium oxide, cobalt oxide, and cobalt oxide. Although the electrode of this technology has a long service life, the conductivity of the electrode is poor. SUMMARY

[0004] To solve the above technical problems, the present application first provides a composite electrode for water splitting, which comprises a titanium base, an intermediate coating, and a surface coating.

[0005] Further, the preparation raw materials of the intermediate coating include titanium oxide, nickel oxide, and transition metal selenide.

[0006] Further, the preparation raw materials of the intermediate coating include 100 parts of titanium oxide, 5-30 parts of nickel oxide, and 1-8 parts of transition metal selenide, by weight.

[0007] Further, the transition metal selenide includes, but is not limited to, at least one of Fe3Se4, FeSe, CoSe2, NiSe, NiSe2, CuSe, and ZrSe2.

[0008] Preferably, the transition metal selenide includes Fe3Se4 and / or FeSe.

[0009] Further preferably, the preparation raw materials of the intermediate coating further include molybdenum carbide.

[0010] Further, the addition amount of the molybdenum carbide is 1-15 parts.

[0011] Further, in the preparation raw material of the intermediate coating, the weight ratio of the titanium oxide, the nickel oxide, the transition metal selenide and the molybdenum carbide is 100:(10-20):(1-5):(1-10). The titanium oxide has a large oxygen defect and a band bending, and is mostly used as a photocatalyst for hydrogen production, but the titanium oxide itself has a good catalytic activity for the reduction reaction of hydrogen on the cathode, can promote the redox overpotential of hydrogen evolution, and in addition, the surface thereof has a large number of adsorption sites, which can promote the directional transfer of hydrogen ions in water to the cathode, but the titanium oxide is a semiconductor material, and has a relatively poor conductivity, which has a certain influence on the charge transfer; the nickel oxide can also provide more catalytically active sites to promote the breaking of water molecule bonds, according to the DFT theoretical calculation, the nickel oxide also has a quite suitable hydrogen adsorption free energy, which is beneficial to the attachment of hydrogen atoms on the electrode and the exchange of electrons, but too much content can produce too strong adsorption of hydrogen, which cannot well balance the hydrogen adsorption and desorption process, and affects the generation of negative ion hydrogen in water; the addition of the transition metal selenide and the molybdenum carbide can further catalyze the hydrogen production reaction of the cathode, the sheet structure of the molybdenum carbide not only has a larger specific surface area of electrical activity, but also can promote the transfer of electric charges, and the molybdenum carbide has a lower adsorption free energy for hydrogen ions, which can reduce the water decomposition energy barrier, and more importantly, the molybdenum carbide has a wider adaptability to pH, and the hydrogen production activity can still be maintained under alkaline water quality; the transition metal selenide not only improves the conductivity of the coating, but also effectively increases the content of selenium in water; by compounding the above components and utilizing the synergistic effect of each substance, the hydrogen catalytic effect of the electrode coating is increased under a specific amount of substance, the hydrogen content of water is increased, the water overpotential is effectively reduced, and the amount of noble metal substance used on the electrode surface is reduced.

[0012] In a preferred embodiment, in the preparation raw material of the intermediate coating, the weight ratio of the titanium oxide, the nickel oxide, the transition metal selenide and the molybdenum carbide is 100:13:4:8.

[0013] Further, the transition metal selenide is a carbon material loaded transition metal selenide, and the carbon material includes, but is not limited to, at least one of graphene, carbon nanotube, carbon nanofiber. Although a relatively abundant catalytic hydrogen production active substance is used in the electrode coating, the conductivity of the substance is still poor, and the most obvious performance is that a higher voltage needs to be added to the electrode and a longer time is needed to achieve the best hydrogen production, and another problem is that the structure stability of the catalytically active substance is poor, and the embedding and extraction of hydrogen ions in water can cause the collapse of the microstructure of the coating, thereby affecting the transmission of electrons and the efficiency of hydrogen production, and reducing the service life of the electrode in the long run; in view of the above problems, the inventors specially add a carbon material with high structural stability and a large number of specific surface area and attachment sites in the coating, which not only enhances the conductivity of the electrode but also enhances the interface interaction of the catalytic substance in the coating, promotes the diffusion and transmission of ions and electrons, effectively inhibits the collapse of the microstructure in the coating system, and improves the hydrogen production efficiency and hydrogen production.

[0014] Further, the preparation method of the carbon material loaded transition metal selenide is: dispersing a transition metal salt, a surfactant, urea and a carbon material in deionized water, stirring and reacting at 45-55°C for 1-3h, and then freeze-drying to obtain a solid; mixing the solid and selenium powder and placing them in a tube furnace for calcination for 2-4h, and the calcination temperature is 580-650°C; then grinding and taking out.

[0015] Further, the weight ratio of the transition metal salt to the carbon material is (10-20):1.

[0016] In a preferred embodiment, the transition metal salt is a trivalent iron salt selected from any one of ferric nitrate and ferric chloride; and the carbon material is a graphene nanosheet.

[0017] Further, the graphene nanosheet has 1-8 layers, and the diameter is <30μm; preferably, the number of layers is 1-3 layers, and the diameter is <10μm, and the specific surface area is 500-550m 2 / g.

[0018] Further, the surfactant is an alkyl sulfonate or polyvinyl alcohol; preferably, it is dodecyl sulfonate. The addition amount of the surfactant is 1-4% of the weight of the transition metal salt.

[0019] Further, the addition amount of urea is 0.8-1.2 times the weight of the transition metal salt.

[0020] Furthermore, the weight ratio of the transition metal salt to the volume ratio of deionized water is 60-80 mg / mL.

[0021] Furthermore, the weight ratio of the solid to the selenium powder is 1:(3-5).

[0022] Furthermore, the raw materials for preparing the intermediate coating also include 90-150 parts water, 1-4 parts binder, and 0.5-1 part dispersant.

[0023] Further, the adhesive includes at least one of sodium carboxymethyl cellulose, hydroxypropyl methyl cellulose, ethyl cellulose, polyethylene glycol, sodium alginate, and polylactic acid; preferably polyethylene glycol, more preferably polyethylene glycol 200-600.

[0024] Furthermore, the dispersant is selected from at least one of sodium hexametaphosphate, sodium tripolyphosphate, and terpineol; preferably sodium hexametaphosphate.

[0025] Furthermore, the total dry film thickness of the intermediate coating is 25-60 μm, more preferably 30-45 μm.

[0026] Furthermore, the surface coating is a noble metal coating, which includes at least one of RuO2, PdO2, IrO2, and PtO2.

[0027] Preferably, the noble metal coating comprises IrO2 and PtO2.

[0028] Secondly, this application also provides a method for preparing the composite electrode for water electrolysis, comprising the following steps:

[0029] S1. Pretreatment of titanium substrate;

[0030] S2, Preparation of raw materials for the intermediate coating;

[0031] S3, Intermediate Coating Spraying: The raw material of the intermediate coating of S2 is sprayed onto the surface of the titanium substrate using a plasma spraying process.

[0032] S4. Preparation of raw materials for surface coating;

[0033] S5. Surface coating application.

[0034] Furthermore, the pretreatment of the titanium substrate includes: degreasing, sandblasting, acid etching, cleaning, and drying.

[0035] Furthermore, after sandblasting, the surface roughness Ra value of the titanium substrate is 3-10 μm, preferably 3-5 μm.

[0036] Furthermore, after undergoing S1 treatment, the surface roughness of the titanium substrate is 4-9 μm.

[0037] Further, S2 specifically involves: mixing and dispersing the raw materials for the intermediate coating to obtain a suspension, drying the suspension, and using a spray dryer to make it into composite particles with an average diameter of 10-45 μm.

[0038] Further, S3 involves: using a plasma spraying process to melt-spray the composite particles obtained in S2 onto the titanium substrate of S1, with 2-5 spraying cycles; the plasma spraying process parameters are: plasma gas: Ar: 25-40 standard L / min, H2: 10-20 standard L / min; spraying current: 450-530A; spraying voltage: 60-70V; spraying distance: 100-150mm; powder feed rate: 25-30rad / min. This application employs a specific plasma spraying process to match the coating raw materials with the above-mentioned components, thereby increasing the hydrogen production capacity of the coated electrode and reducing the redox overpotential of water. This is likely because the coating raw materials are mostly solid particles; after plasma melting, these solid particles agglomerate to a certain extent, forming larger particles. This results in a specific three-dimensional structure and pore distribution in the electrode coating. This three-dimensional structure and pore distribution promote the exposure of more catalytic active sites in the coating raw materials, avoiding the problem of reduced hydrogen production due to the shielding of active sites. Furthermore, the plasma-sprayed coating has a relatively rough surface, which is beneficial for the adhesion of upper noble metal particles. However, when the spraying voltage, current, etc., are too high, or the spraying distance is too large, the impact force of the coating raw materials on the electrode substrate is too strong, causing changes in the three-dimensional structure. This results in excessively dense coatings and uneven pore distribution, which in turn reduces the hydrogen production capacity and uniformity.

[0039] Furthermore, the preparation of the raw materials for the S4 surface coating includes: dissolving iridium salt and platinum salt in a solvent to prepare a mixed solution of precursors. The solvent is a mixed solution of water and ethanol, preferably in a volume ratio of 1:1.

[0040] Furthermore, the iridium salt includes, but is not limited to, any one of iridium chloride, iridium nitrate, and iridium acetate.

[0041] Furthermore, the platinum salt includes, but is not limited to, any one of platinum chloride, chloroplatinic acid, and platinum nitrate.

[0042] Furthermore, the total molar concentration of iridium and platinum salts in the mixed solution is 0.1-0.45 mol / L.

[0043] Furthermore, the molar ratio of the iridium salt to the platinum salt is 1:(1-4).

[0044] Further, S5 specifically involves coating the mixed solution of S4 onto the titanium substrate loaded with the intermediate coating obtained in S3, drying it, and then sintering it at 480-550℃ for 15-60 minutes; repeating the coating and sintering process 3-8 times to obtain the composite electrode for water electrolysis.

[0045] Furthermore, the coating amount of the mixed solution on the titanium substrate is 0.03-0.06 mL / cm². 2 .

[0046] Finally, this application also provides the application of the composite electrode, which is used in the preparation of electrolyzed water products as an anode and / or cathode.

[0047] Preferably, when the composite electrode is used as both an anode and a cathode for water electrolysis, the externally applied voltage is 3-8V and the current is 5-9A; more preferably, the externally applied voltage is 5V and the current is 7A.

[0048] Advantages

[0049] 1. The composite electrode prepared in this application includes a titanium substrate, an intermediate coating and a surface coating. The intermediate coating can provide a large number of catalytic active sites, effectively reduce the amount of noble metal material coated in the surface coating, reduce production costs, and has special roughness and surface structure, which can enhance the adhesion of the surface coating to the titanium substrate.

[0050] 2. This application optimizes the types and amounts of raw materials used in the intermediate coating, and specifically specifies that the weight ratio of titanium oxide, nickel oxide, transition metal selenide and molybdenum carbide is 100:(10-20):(1-5):(1-10) to enhance the conductivity of the composite electrode and its catalytic activity on water, increase the amount of hydrogen produced and reduce the redox overpotential of water, reduce the amount of precious metals used, and also increase the selenium content in the water.

[0051] 3. This application specifically uses carbon-supported transition metal selenides, which utilize the special structure of carbon materials to weaken the interfacial interaction between intermediate coating raw materials, improve the conductivity and structural stability of the composite electrode, and enhance its service life (up to 3-5 years).

[0052] 4. This application optimizes the plasma spraying process of the intermediate coating, so that raw materials with specific composition produce specific three-dimensional structures and pore distributions under specific spraying processes, thereby enhancing hydrogen production capacity and uniformity by improving the specific surface area, structural stability and adsorption-desorption performance of the coating.

[0053] 5. This application optimizes the amount of precious metal substances in the surface coating to increase hydrogen production. Detailed Implementation

[0054] Example

[0055] Example 1

[0056] This embodiment provides a composite electrode for water electrolysis, the electrode comprising a titanium substrate, an intermediate coating, and a surface coating; the preparation method of the composite electrode is as follows:

[0057] S1. Pretreatment of titanium substrate:

[0058] The pretreatment of the titanium substrate includes: degreasing, sandblasting (the surface roughness Ra value of the titanium substrate after sandblasting is 4μm), acid etching, cleaning and drying; after the titanium substrate undergoes S1 treatment, the surface roughness is 7μm.

[0059] S2. Preparation of raw materials for the intermediate coating:

[0060] The raw materials for preparing the intermediate coating, by weight, include: 100 parts titanium oxide, 13 parts nickel oxide, 4 parts graphene-supported Fe3Se4, 8 parts molybdenum carbide, 100 parts water, 3 parts binder (polyethylene glycol 400), and 0.7 parts dispersant (sodium hexametaphosphate).

[0061] The preparation method of the graphene-supported Fe3Se4 is as follows: ferric chloride, sodium dodecyl sulfonate, urea, and graphene nanosheets are dispersed in deionized water, stirred at 50°C for 1 hour, and then freeze-dried to obtain a solid. This solid is then mixed with selenium powder and calcined in a tube furnace for 3.5 hours at 620°C. After calcination, it is then removed and ground. The weight ratio of ferric chloride to deionized water is 70 mg / mL, the weight ratio of ferric chloride to graphene nanosheets is 15:1, the amount of sodium dodecyl sulfonate added is 2.5% of the weight of ferric chloride, the amount of urea added is 1.2 times the weight of ferric chloride, and the weight ratio of solid to selenium powder is 1:4. The graphene nanosheets have 1-3 layers, a diameter <10 μm, and a specific surface area of ​​500-550 m². 2 / g, purchased from Shanghai NaoNano, product number NO-C-066-1.

[0062] The raw materials for the intermediate coating are mixed and dispersed to obtain a suspension. The suspension is dried and a spray dryer is used to make composite particles with an average diameter of 15 μm.

[0063] S3, Spraying of the intermediate coating:

[0064] The composite particles obtained in S2 were melt-sprayed onto the titanium substrate of S1 using a plasma spraying process, with three spraying passes. The plasma spraying process parameters were as follows: plasma gas: Ar: 35 standard L / min, H2: 15 standard L / min; spraying current: 500A; spraying voltage: 65V; spraying distance: 130mm; powder feed rate: 26rad / min.

[0065] The total dry film thickness of the intermediate coating is 45 μm.

[0066] S4. Preparation of raw materials for surface coating:

[0067] A mixed solution of precursors was prepared by dissolving iridium acetate and chloroplatinic acid in a mixed solution of water and ethanol (volume ratio 1:1) at a molar ratio of 1:2, with a total molar concentration of iridium salt and platinum salt of 0.3 mol / L.

[0068] S5. Surface coating application:

[0069] The mixed solution of S4 was coated onto the titanium substrate with the intermediate coating obtained in S3, and the coating amount of the mixed solution on the titanium substrate was 0.04 mL / cm. 2 After drying, sinter at 520℃ for 30 minutes; repeat the coating and sintering operation 5 times according to the above method; and the composite electrode for electrolysis of water can be obtained.

[0070] Example 2

[0071] This embodiment provides a composite electrode for water electrolysis, the electrode comprising a titanium substrate, an intermediate coating, and a surface coating; the preparation method of the composite electrode is as follows:

[0072] S1. Pretreatment of titanium substrate:

[0073] The pretreatment of the titanium substrate includes: degreasing, sandblasting (after sandblasting, the surface roughness Ra value of the titanium substrate is 5μm), acid etching, cleaning and drying; the surface roughness of the titanium substrate after S1 treatment is 9μm.

[0074] S2. Preparation of raw materials for the intermediate coating:

[0075] The raw materials for preparing the intermediate coating, by weight, include: 100 parts titanium oxide, 20 parts nickel oxide, 5 parts graphene-supported Fe3Se4, 10 parts molybdenum carbide, 150 parts water, 4 parts binder (polyethylene glycol 600), and 1 part dispersant (sodium hexametaphosphate).

[0076] The preparation method of the graphene-supported Fe3Se4 is as follows: ferric chloride, sodium dodecyl sulfonate, urea, and graphene nanosheets are dispersed in deionized water, stirred at 55°C for 1 hour, and then freeze-dried to obtain a solid. This solid is then mixed with selenium powder and calcined in a tube furnace for 2 hours at 650°C. After calcination, it is then removed and ground. The weight ratio of ferric chloride to deionized water is 80 mg / mL, the weight ratio of ferric chloride to graphene nanosheets is 20:1, the amount of sodium dodecyl sulfonate added is 4% of the weight of ferric chloride, the amount of urea added is 1.2 times the weight of ferric chloride, and the weight ratio of solid to selenium powder is 1:5. The graphene nanosheets have 1-3 layers, a diameter <10 μm, and a specific surface area of ​​500-550 m². 2 / g, purchased from Shanghai NaoNano, product number NO-C-066-1.

[0077] The raw materials for the intermediate coating are mixed and dispersed to obtain a suspension. The suspension is dried and a spray dryer is used to make composite particles with an average diameter of 45 μm.

[0078] S3, Spraying of the intermediate coating:

[0079] The composite particles obtained in S2 were melt-sprayed onto the titanium substrate of S1 using a plasma spraying process, with two spraying passes. The plasma spraying process parameters were as follows: plasma gas: Ar: 40 standard L / min, H2: 10 standard L / min; spraying current: 530 A; spraying voltage: 70 V; spraying distance: 150 mm; powder feed rate: 30 rad / min.

[0080] The total dry film thickness of the intermediate coating is 60 μm.

[0081] S4. Preparation of raw materials for surface coating:

[0082] A mixed solution of precursors was prepared by dissolving iridium acetate and chloroplatinic acid in a mixed solution of water and ethanol (volume ratio 1:1) at a molar ratio of 1:4, with a total molar concentration of iridium salt and platinum salt of 0.45 mol / L.

[0083] S5. Surface coating application:

[0084] The mixed solution of S4 was coated onto the titanium substrate with the intermediate coating obtained in S3, and the coating amount of the mixed solution on the titanium substrate was 0.06 mL / cm. 2 After drying, sinter at 480℃ for 60 minutes; repeat the coating and sintering operation three times according to the above method; and the composite electrode for electrolysis of water can be obtained.

[0085] Example 3

[0086] This embodiment provides a composite electrode for water electrolysis, the electrode comprising a titanium substrate, an intermediate coating, and a surface coating; the preparation method of the composite electrode is as follows:

[0087] S1. Pretreatment of titanium substrate:

[0088] The pretreatment of the titanium substrate includes: degreasing, sandblasting (the surface roughness Ra value of the titanium substrate after sandblasting is 3μm), acid etching, cleaning and drying; the surface roughness of the titanium substrate after S1 treatment is 5μm.

[0089] S2. Preparation of raw materials for the intermediate coating:

[0090] The raw materials for preparing the intermediate coating, by weight, include: 100 parts titanium oxide, 10 parts nickel oxide, 1 part graphene-supported Fe3Se4, 1 part molybdenum carbide, 90 parts water, 1 part binder (polyethylene glycol 200), and 0.5 parts dispersant (sodium hexametaphosphate).

[0091] The preparation method of the graphene-supported Fe3Se4 is as follows: ferric chloride, sodium dodecyl sulfonate, urea, and graphene nanosheets are dispersed in deionized water, stirred at 45°C for 1 hour, and then freeze-dried to obtain a solid. This solid is then mixed with selenium powder and calcined in a tube furnace for 4 hours at 580°C. After calcination, it is then removed and ground. The weight ratio of ferric chloride to deionized water is 60 mg / mL, the weight ratio of ferric chloride to graphene nanosheets is 10:1, the amount of sodium dodecyl sulfonate added is 1% of the weight of ferric chloride, the amount of urea added is 0.8 times the weight of ferric chloride, and the weight ratio of solid to selenium powder is 1:3. The graphene nanosheets have 1-3 layers, a diameter <10 μm, and a specific surface area of ​​500-550 m². 2 / g, purchased from Shanghai NaoNano, product number NO-C-066-1.

[0092] The raw materials for the intermediate coating are mixed and dispersed to obtain a suspension. The suspension is dried and a spray dryer is used to make composite particles with an average diameter of 10 μm.

[0093] S3, Spraying of the intermediate coating:

[0094] The composite particles obtained in S2 were melt-sprayed onto the titanium substrate of S1 using a plasma spraying process, with 5 spraying passes. The plasma spraying process parameters were as follows: plasma gas: Ar: 25 standard L / min, H2: 20 standard L / min; spraying current: 450A; spraying voltage: 60V; spraying distance: 100mm; powder feed rate: 25rad / min.

[0095] The total dry film thickness of the intermediate coating is 30 μm.

[0096] S4. Preparation of raw materials for surface coating:

[0097] A mixed solution of precursors was prepared by dissolving iridium acetate and chloroplatinic acid in a mixed solution of water and ethanol (volume ratio 1:1) at a molar ratio of 1:1, with a total molar concentration of iridium salt and platinum salt of 0.1 mol / L.

[0098] S5. Surface coating application:

[0099] The mixed solution of S4 was coated onto the titanium substrate with the intermediate coating obtained in S3, and the coating amount of the mixed solution on the titanium substrate was 0.03 mL / cm. 2 After drying, sinter at 550℃ for 30 minutes; repeat the coating and sintering operation 8 times according to the above method; and the composite electrode for electrolysis of water can be obtained.

[0100] Comparative Example 1

[0101] The preparation of the intermediate coating is basically the same as that in Example 1, except that the raw materials include: 100 parts titanium oxide, 40 parts nickel oxide, 4 parts graphene-supported Fe3Se4, 8 parts molybdenum carbide, 130 parts water, 3 parts binder (polyethylene glycol 200-600), and 0.7 parts dispersant (sodium hexametaphosphate).

[0102] Comparative Example 2

[0103] The preparation of the intermediate coating is basically the same as that in Example 1, except that the raw materials include: 100 parts titanium oxide, 40 parts nickel oxide, 4 parts graphene-supported Fe3Se4, 0.5 parts molybdenum carbide, 100 parts water, 3 parts binder (polyethylene glycol 400), and 0.7 parts dispersant (sodium hexametaphosphate).

[0104] Comparative Example 3

[0105] It is basically the same as Example 1, except that graphene nanosheets are not added in the preparation method of Fe3Se4.

[0106] Comparative Example 4

[0107] The method is basically the same as in Example 1, except that the graphene nanosheets have 5-8 layers, a diameter of <10μm, and a specific surface area of ​​300-350m². 2 / g, purchased from Shanghai Naoyun Nanomaterials, product number NO-C-066-2.

[0108] Comparative Example 5

[0109] It is basically the same as Example 1, except that the weight ratio of ferric chloride and graphene nanosheets is 30:1.

[0110] Comparative Example 6

[0111] The process is basically the same as in Example 1, except that the plasma spraying process parameters are as follows: plasma gas: Ar: 35 standard L / min, H2: 15 standard L / min; spraying current: 600A; spraying voltage: 82V; spraying distance: 100mm; powder feed rate: 30rad / min.

[0112] Comparative Example 7

[0113] It is basically the same as Example 1, except that the sintering temperature in S5 is 600℃.

[0114] Comparative Example 8

[0115] It is basically the same as Example 1, except that the adhesive in S2 is polyethylene glycol 1000.

[0116] Performance testing methods:

[0117] The composite electrode in the above embodiment is used as both cathode and anode, and a diaphragm (Nafion115) is set up to assist in the construction of an electrolysis device (the electrolyte is pure water, and the water volume is 1.5L). A constant current circuit is set to work, and the current intensity is 10A. After electrolysis for 20 minutes, the oxidation-reduction overpotential value (ORP), the hydrogen content in the water, and the selenium content are measured.

[0118] Performance test results:

[0119] The test results are shown in Table 1.

[0120] Table 1

[0121]

[0122]

[0123] Results Analysis: Examples 1-3 all achieved good hydrogen and selenium contents, and also had the lowest redox potential values. In Comparative Example 1, nickel oxide was beneficial for the adhesion of hydrogen atoms to the electrode and electron exchange; however, excessive use led to a decrease in hydrogen production. This may be because excessive nickel oxide had too high an adsorption activity for hydrogen, disrupting the adsorption-desorption balance of hydrogen particles. Only a specific amount of nickel oxide could synergistically provide optimal catalytic activity for water splitting with specific amounts of titanium oxide, transition metal selenides, and molybdenum carbide, producing the highest hydrogen content in the water. In Comparative Example 2, when the amount of molybdenum carbide was too small, on the one hand, the number of catalytic active sites decreased, and on the other hand, the conductivity of the composite electrode decreased, both leading to a decrease in the catalytic performance of the electrode for water electrolysis, a decrease in hydrogen production, and an increase in redox overpotential. Only a specific amount of molybdenum carbide could synergistically provide the best catalytic decomposition state for water with specific amounts of titanium oxide, nickel oxide, and transition metal selenides. In Comparative Example 3, without the addition of graphene nanosheets, the raw materials formed numerous interfaces, and some effective sites were obscured, disrupting the original intermediate coating state with its larger specific surface area and unique interface distribution, leading to a decrease in electrode catalytic performance. In Comparative Example 4, when the number of graphene nanosheet layers was excessive, the interaction and compression overlap between layers also altered the unique distribution of other raw materials on the graphene, and the reduction in specific surface area further affected the electrode's catalytic performance, similar to Example 3. In Comparative Example 5, when the amount of ferric chloride was too high, Fe3Se4 was more widely distributed in situ on the graphene, reducing the distribution of other intermediate layer raw materials on the graphene, causing effective sites to be obscured or excessive interfacial interactions, thus resulting in poor hydrogen production and redox potential. In Comparative Example 6, the plasma spraying process was changed, and the impact force of the coating raw materials on the electrode substrate was too strong, which may have altered the three-dimensional structure. The coating was too dense and the pore distribution was uneven, reducing hydrogen production and hydrogen production uniformity. In Comparative Example 7, the sintering temperature was increased, which may have led to the thermal decomposition of some effective catalytic substances and a certain degree of collapse in their three-dimensional structure, thus resulting in a decrease in catalytic performance. In Comparative Example 8, the binder had a relatively high average molecular weight, and the excessive interaction forces generated by its molecular chains affected the dispersion state of the intermediate coating raw materials, which in turn affected the arrangement of the raw materials in the intermediate coating.

Claims

1. A composite electrode for water electrolysis, characterized in that, The electrode comprises a titanium substrate, an intermediate coating, and a surface coating; the intermediate coating is prepared by means of molybdenum carbide, wherein the amount of molybdenum carbide added is 1-15 parts; the intermediate coating is also prepared by means of 90-150 parts of water, 1-4 parts of binder, and 0.5-1 parts of dispersant. The raw materials for preparing the intermediate coating, by weight, include: 100 parts titanium oxide, 5-30 parts nickel oxide and 1-8 parts carbon-supported transition metal selenide; The preparation method of the transition metal selenide supported on the carbon material is as follows: the transition metal salt, surfactant, urea and carbon material are dispersed in deionized water, stirred and reacted at 45-55℃ for 1-3 hours, and then freeze-dried to obtain a solid; the solid is mixed with selenium powder and calcined in a tube furnace for 2-4 hours at a calcination temperature of 580-650℃; then it is taken out and ground; the carbon material is graphene.

2. The composite electrode according to claim 1, characterized in that, The transition metal selenides include at least one of Fe3Se4, FeSe, CoSe2, NiSe, NiSe2, CuSe, and ZrSe2.

3. The composite electrode according to claim 1, characterized in that, The weight ratio of transition metal salts to carbon materials is (10-20):

1.

4. The composite electrode according to any one of claims 1-3, characterized in that, The surface coating is a noble metal coating, which includes at least one of RuO2, PdO2, IrO2, and PtO2.

5. The method for preparing the composite electrode according to claim 4, characterized in that, Includes the following steps: S1. Pretreatment of titanium substrate; S2, Preparation of raw materials for the intermediate coating; S3, Intermediate Coating Spraying: The raw material of the intermediate coating of S2 is sprayed onto the surface of the titanium substrate using a plasma spraying process. S4. Preparation of raw materials for surface coating; S5. Surface coating application.

6. The preparation method according to claim 5, characterized in that, The preparation of the raw materials for the S4 surface coating includes: dissolving iridium salt and platinum salt in a solvent to prepare a mixed solution of precursors; the molar ratio of iridium salt and platinum salt is 1:(1-4).

7. The preparation method according to claim 6, characterized in that, Specifically, S5 involves coating the mixed solution of S4 onto the titanium substrate loaded with the intermediate coating obtained in S3, drying it, and then sintering it at 480-550℃ for 15-60 minutes; repeating the coating and sintering process 3-8 times to obtain the composite electrode for water electrolysis.

8. The application of the composite electrode according to any one of claims 1-3, characterized in that, The composite electrode is used in the preparation of electrolyzed water products, serving as the anode and / or cathode.

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