A method for preparing an electrode with enhanced adhesion of RuO2 to a titanium substrate by an interface sintering method

Abstract

The present application relates to a method for preparing RuO2 / Ti electrode by loading RuO2 nanoparticles on titanium substrate through interface sintering method. The prepared RuO2 / Ti electrode has complete and continuous coating, no crack, RuO2 in the coating keeps nanostructure, RuO2 has strong adhesion with titanium substrate, and the electrode has high catalytic activity and long running life. Compared with the RuO2 / Ti electrode prepared by traditional physical bonding method, the RuO2 / Ti electrode prepared by the present application has 80%-140% higher electrochemical chlorine evolution yield; and the RuO2 / Ti electrode prepared by the physical bonding method has only 4-10 min stability under the condition of 1 M H2SO4, 100 mA / cm 2 2, while the RuO2 / Ti electrode prepared by the present application has 45-55 h stability. The RuO2 nanoparticles in the present application include but are not limited to hydrothermal method synthesized RuO2 nanoparticles, thermal decomposition method prepared RuO2 nanoparticles, commercially purchased RuO2 nanoparticles, and RuO2 nanoparticles doped and modified by Cr or Zn or Ir or Al or N or Rh or Si. The preparation method of the present application is simple and easy to scale up.

Description

Technical Field

[0001] This invention relates to a method for preparing RuO2 / Ti electrodes by loading RuO2 nanoparticles onto a titanium substrate through an interface sintering method, thereby improving the adhesion between RuO2 and the titanium substrate, and belongs to the field of inorganic materials technology. Background Technology

[0002] RuO2 possesses excellent electrochemical chlorine and oxygen evolution catalytic activity, making it a current research hotspot for doping modification. For example, Wang et al. improved the intrinsic activity and stability of RuO2 catalysts by doping RuO2 with Rh [Nat. Commun. 2023, 14, 1412]; Ping et al. stabilized the highly active Ru sites in RuO2 and suppressed lattice oxygen oxidation through interstitial silicon doping [Nat. Commun. 2024, 15, 2501]. However, the preparation of RuO2 electrodes mainly relies on physical bonding methods, such as mixing RuO2 powder with binders (e.g., Nafion, PTFE) and then laminating or coating it onto a substrate [Nat. Commun. 2024, 15, 2501; Angew. Chem. Int. Ed. 2024, 63, e202405798]. In electrodes prepared by physical bonding, the adhesion between RuO2 and the substrate is weak, and the bonding interface is prone to aging and detachment, leading to easy loss of RuO2 catalyst and short electrode life. Furthermore, binders are mostly polymers or organic materials, many of which are non-conductive or have poor conductivity, potentially covering the active sites of the catalyst and reducing its activity. Physical bonding methods are mainly suitable for laboratory-scale characterization and analysis, and are difficult to apply to practical applications requiring high activity and stability (such as electrochemical chlorination and electrochemical water treatment), thus limiting the practical application prospects of RuO2 (including modified RuO2) nanoparticles. On the other hand, titanium substrates (titanium sheets or meshes, etc.) are the preferred electrode substrates in the chlor-alkali industry, water electrolysis for oxygen production, and electrochemical water treatment due to their excellent corrosion resistance and high mechanical strength. Therefore, there is an urgent need to develop a method for preparing RuO2 / Ti electrodes by loading RuO2 nanoparticles onto titanium substrates to improve the adhesion between RuO2 and the titanium substrate, thereby enhancing the catalytic activity and stability of the electrode. Summary of the Invention

[0003] This invention provides a method for preparing RuO2 / Ti electrodes by loading RuO2 nanoparticles onto a titanium substrate via interface sintering. The RuO2 catalytic component in the prepared RuO2 / Ti electrode has strong adhesion to the titanium substrate, resulting in high electrocatalytic activity, long lifespan, and ease of scale-up production.

[0004] The technical solution of the present invention is as follows:

[0005] A method for preparing a RuO2 / Ti electrode using an interface sintering method to enhance the adhesion between RuO2 and a titanium substrate is characterized by the following steps: a non-noble metal precursor with a radius similar to that of Ru ions is selected and added to an organic solvent along with citric acid and RuO2 nanoparticles to prepare a coating solution. The coating solution is then applied to a titanium substrate using a brush, followed by calcination to form the RuO2 / Ti electrode. During calcination, the non-noble metal precursor sintersects at the interface between RuO2 and the titanium substrate, transforming into a metal oxide. Simultaneously, it undergoes an interfacial reaction with both RuO2 and the titanium substrate, generating a chemically bonded diffusion layer. This enhances the adhesion between RuO2 and the titanium substrate, thereby improving the activity and stability of the RuO2 / Ti electrode. The brush-coating-calcination electrode preparation method is simple and easily scaled up for production. The RuO2 / Ti electrode preparation method described herein is applicable to various RuO2 nanoparticles, including but not limited to RuO2 nanoparticles synthesized by hydrothermal methods, RuO2 nanoparticles prepared by thermal decomposition methods, commercially available RuO2 nanoparticles, and RuO2 nanoparticles modified by elemental doping such as Cr, Zn, Ir, Al, N, Rh, or Si. The RuO2 / Ti electrode coating prepared by this method is complete, continuous, and crack-free, with the RuO2 maintaining its nanostructure. The RuO2 adheres strongly to the titanium substrate, resulting in high catalytic activity and a long service life. Compared to RuO2 / Ti electrodes prepared by traditional physical bonding methods, the RuO2 / Ti electrode prepared by the interface sintering method exhibits an 80%-140% increase in chlorine evolution yield. Furthermore, the RuO2 / Ti electrode prepared by the physical bonding method shows improved performance at 1 M H2SO4 and 100 mA / cm². 2 Under certain conditions, the stability is only 4-10 min, while the stability of the RuO2 / Ti electrode prepared by the interface sintering method is 45-55 h.

[0006] A specific method for preparing a RuO2 / Ti electrode using an interface sintering method to enhance the adhesion between RuO2 and a titanium substrate is as follows: (1) Titanium substrate pretreatment: After polishing the titanium substrate with sandpaper, it is placed in acetone, anhydrous ethanol and deionized water for ultrasonic cleaning for 10-30 min in sequence. Then it is placed in oxalic acid solution (mass fraction of 10%), heated to a slight boil for acid etching for 1-2 h, then cleaned with deionized water, and finally the treated titanium substrate is placed in anhydrous ethanol for storage. (2) Preparation of coating solution: Add a certain amount of RuO2 nanoparticles, non-precious metal precursor and citric acid to an organic solvent at the same time, and add a small amount of concentrated hydrochloric acid dropwise. Stir evenly to obtain coating solution. (3) Electrode coating and calcination: The coating solution in (2) is applied to the titanium substrate treated in (1) by brush. Each time the coating is applied, the coated electrode is dried under an infrared lamp. Then the electrode is placed in a muffle furnace at 450-550℃ and thermally oxidized in air atmosphere for 5-10 min. After that, it is taken out and cooled to room temperature before the next coating is applied. This process is repeated 8-12 times. After the last coating, the electrode is placed in a muffle furnace at 450-550℃ and calcined in air atmosphere for 1-2 h. After naturally cooling to room temperature in the furnace, the RuO2 / Ti electrode is obtained. (4) Electrode performance testing: The RuO2 / Ti electrode prepared in (3) was subjected to surface morphology and phase analysis, and adhesion, chlorine evolution performance and stability tests were performed; adhesion was tested by a simple tape pull-out method, in which the tape was applied to the electrode surface and then peeled off. The less coating powder left on the tape surface, the better the adhesion; chlorine evolution performance was tested at 50 mM NaCl, pH 7, 10 mA / cm 2 The stability test was conducted under the following conditions: 1 M H₂SO₄, 100 mA / cm⁻¹. 2 Under the conditions.

[0007] According to the method of the present invention, the preferred method is: In step (2) above, the non-precious metal precursor is tetrabutyl titanate or stannous chloride.

[0008] In step (2) above, the molar ratio of the non-precious metal precursor to RuO2 in the coating solution is (3-7.5):3, and the total concentration of non-precious metals and Ru in the coating solution is 0.15-0.28 mol / L.

[0009] In step (2) above, the RuO2 nanoparticles include, but are not limited to, RuO2 nanoparticles synthesized by hydrothermal method, RuO2 nanoparticles prepared by thermal decomposition method, commercially purchased RuO2 nanoparticles, and RuO2 nanoparticles modified by doping with elements such as Cr, Zn, Ir, Al, N, Rh, or Si.

[0010] In step (2) above, the citric acid has a mass fraction of 2-3 wt% in the solvent.

[0011] In step (2) above, the organic solvent is a mixed solution of ethylene glycol and ethanol in a volume ratio of 7:3.

[0012] The technical features of this invention are as follows: 1. This invention involves dispersing RuO2 nanoparticles in an organic solvent containing a non-precious metal precursor and citric acid to prepare a coating solution. The coating solution is then applied to a titanium substrate using a brush, followed by calcination to form a RuO2 / Ti electrode. During calcination, the bulk crystal structure of the RuO2 nanoparticles and the titanium substrate remains unchanged. Citric acid is burned to CO2 and removed, while the organic solvent is removed through volatilization and combustion. The non-precious metal precursor sintersects at the interface between RuO2 and the titanium substrate, transforming into a metal oxide. Simultaneously, it undergoes an interfacial reaction with both RuO2 and the titanium substrate, generating a chemically bonded diffusion layer. This significantly enhances the interfacial bonding strength between RuO2 and the titanium substrate, thereby synergistically improving the electrocatalytic activity and stability of the electrode.

[0013] 2. The RuO2 / Ti electrode coating prepared by this invention is complete, continuous, and crack-free. The RuO2 in the coating maintains its nanostructure, exhibiting strong adhesion between the RuO2 and the titanium substrate. This results in high catalytic activity and a long operating life for the electrode. Compared to RuO2 / Ti electrodes prepared by traditional physical bonding methods, the RuO2 / Ti electrode prepared by this invention shows an 80%-140% increase in electrochemical chlorine evolution yield. Furthermore, the RuO2 / Ti electrode prepared by the physical bonding method exhibits higher catalytic activity at 1 M H2SO4 and 100 mA / cm². 2 Under certain conditions, the stability is only 4-10 min, while the RuO2 / Ti electrode prepared by this invention has a stability of 45-55 h.

[0014] 3. The selection of non-precious metals plays an important role in this invention. Ru in RuO2 4+ The ionic radius is approximately 62 pm; a small amount of TiO2 is formed on the titanium substrate surface during calcination. 4+ The ionic radius is approximately 60.5 pm. The non-precious metals selected in this invention patent are titanium or tin, which form TiO2 or SnO2 after calcination. 4+ The ionic radius is approximately 69 pm. It can be seen that the selected titanium or tin reacts with RuO2 and Ru in the titanium substrate. 4+ Ti 4+ With similar ionic radii and lattice matching, tin readily undergoes interfacial reactions, forming diffusion layers with Ti-O-Ru or Sn-O-Ru bonds at the RuO2 interface and with Ti-O-Ti or Sn-O-Ti bonds at the titanium substrate interface, thereby enhancing the interfacial bonding strength between RuO2 and the titanium substrate. Furthermore, both titanium and tin are non-precious metals and inexpensive.

[0015] 4. The amount of non-precious metal precursor added to the coating solution plays a crucial role in this invention. The molar ratio of non-precious metal precursor to RuO2 in the coating solution is (3-7.5):3, and the total concentration of non-precious metal and Ru in the coating solution is 0.15-0.28 mol / L. When the amount of non-precious metal precursor added is too low, the interfacial reaction with RuO2 and titanium substrate during calcination is insufficient, leading to easy detachment of RuO2, which is detrimental to the stability of the RuO2 / Ti electrode. When the amount of non-precious metal precursor added is too high, the content of non-precious metal oxides after calcination is too high, which masks the catalytic active sites of RuO2 and reduces the catalytic activity of the RuO2 / Ti electrode.

[0016] 5. The selection of citric acid and its amount added to the coating solution play a crucial role in this invention. A single citric acid molecule contains three carboxyl groups, exhibiting strong chelating properties, thus improving the dispersion of RuO2 nanoparticles in the coating solution and helping to maintain the nanostructure of RuO2 during electrode formation. Simultaneously, citric acid has a low thermal decomposition temperature and can be completely burned off above 450°C, thus avoiding any adverse effects on the RuO2 / Ti electrode. 6. In this invention, the mass fraction of citric acid in the coating solution is 2-3 wt%. If the mass fraction is too low, the dispersion ability of RuO2 nanoparticles is insufficient; if the mass fraction is too high, the viscosity of the coating solution is too high, which easily leads to uneven coating.

[0017] 7. The process flow for preparing the RuO2 / Ti electrode in this invention is as follows: preparing a coating solution, applying the coating solution to the titanium substrate by brushing, and calcining. This process is suitable for existing industrial preparation processes, namely the surface coating thermal decomposition method, and is easy to scale up for production.

[0018] 8. The RuO2 / Ti electrode prepared by the interface sintering method in this invention differs fundamentally from the commercially available chlorine-evolving coated titanium electrode (DSA) in terms of coating solution composition and electrode coating composition. The commercially available chlorine-evolving DSA electrode is prepared by surface coating thermal decomposition, using an organic solvent containing RuCl3 and tetrabutyl titanate. During calcination, RuCl3 and tetrabutyl titanate undergo simultaneous thermal decomposition, forming a coating whose main component is a RuO2-TiO2 solid solution. Because all components in the coating undergo thermal decomposition during calcination, significant thermal stress is generated, making the coating prone to crack formation. Furthermore, the electrode coating prepared by the surface coating thermal decomposition method is difficult to form nanostructures. The coating solution for the RuO2 / Ti electrode prepared by the interface sintering method is an organic solvent containing RuO2 nanoparticles, a non-noble metal precursor, and citric acid, which forms a coating with RuO2 as the main component after calcination. During the interfacial sintering calcination process, RuO2 nanoparticles do not need to undergo thermal decomposition and transformation. Only the non-precious metal precursor undergoes thermal decomposition at the interface between RuO2 and the titanium substrate, generating less thermal stress and making the coating less prone to cracking.

[0019] Commercial chlorine evolution DSA electrodes involve the simultaneous thermal decomposition of RuCl3 and tetrabutyl titanate, forming a RuO2-TiO2 solid solution coating. The main catalytic component in the coating, Ru, exhibits strong covalent properties and high stability. The Ti–O bond is more easily broken than the Ru–O bond, and Ti… 4+ By Ru 4+ It is more easily reduced. Therefore, when it is necessary to dope and modify the catalytic coating, it is difficult to precisely control the chemical valence state of Ru. In the interface sintering method, the catalytic component Ru is a pre-prepared RuO2 nanoparticle. Therefore, the chemical valence state of Ru can be precisely controlled through doping and other methods to prepare RuO2 nanoparticles with higher catalytic activity, thereby obtaining an electrode with higher catalytic activity. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the electrode cross-sectional composition in Examples 1-3; Figure 2 The results are the adhesion test results between the electrode coating and the titanium substrate in Examples 1-2 and Comparative Examples 1-3; Figure 3 SEM images of the electrode surfaces in Example 1, Comparative Example 1, and Comparative Example 4; Figure 4 This is an elemental distribution diagram of the electrode in Example 1; Figure 5 The XRD results are for the electrodes in Example 1; Figure 6 The chlorine evolution performance of the electrodes in Examples 1-3 and Comparative Examples 1-4; Figure 7 The results show the stability test results of the electrodes in Example 1 and Comparative Example 1. Detailed Implementation

[0021] The present invention will now be described in detail with reference to specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0022] Example 1 Titanium substrate pretreatment After polishing the titanium sheet with sandpaper, it was ultrasonically cleaned in acetone, anhydrous ethanol and deionized water for 20 minutes in sequence. Then it was placed in oxalic acid solution (mass fraction of 10%) and heated to a slight boil for acid etching for 2 hours. After cleaning with deionized water, the treated titanium sheet was stored in anhydrous ethanol for later use. Preparation of coating solution 50 mg RuO2 nanoparticles, 0.3 mL tetrabutyl titanate, and 88 mg citric acid were simultaneously added to a mixed solution of 5 mL ethylene glycol and ethanol (volume ratio of ethylene glycol to ethanol: 7:3), and a small amount of concentrated hydrochloric acid was added dropwise. The mixture was stirred until homogeneous to obtain the coating solution. Electrode coating and calcination The coating solution in (2) was applied to the titanium sheet treated in (1) using a brush. After each coating, the coated electrode was dried under an infrared lamp. Then, the electrode was placed in a muffle furnace at 500℃ and thermally oxidized in air for 10 min. After that, it was taken out and cooled to room temperature before the next coating was applied. This process was repeated 10 times. After the last coating, the electrode was placed in a muffle furnace at 500℃ and calcined in air for 1 h. After naturally cooling to room temperature in the furnace, the RuO2 / Ti electrode was obtained. Electrode performance testing The electrode prepared in (3) was subjected to surface morphology and phase analysis, and adhesion, chlorine evolution performance and stability tests were performed. Surface morphology analysis showed that the electrode coating was complete and continuous without cracks, and RuO2 in the coating maintained a nanostructure with an average particle size of about 140 nm. Phase analysis showed that the main component of the coating was crystalline RuO2. Adhesion was tested by a simple tape pull-out method. After the tape was applied to the electrode surface and then peeled off, almost no coating powder remained on the tape surface, and the tape remained transparent. Chlorine evolution performance was tested at 50 mM NaCl, pH 7, and 10 mA / cm². 2 The test was conducted under the following conditions, and the chlorine yield after 15 min was measured to be 15.6 mg / L; the stability test was performed at 1 M H2SO4 and 100 mA / cm². 2 The process was carried out under specific conditions, and the prepared RuO2 / Ti electrode was cut into 1×1 cm pieces. 2 The size is such that a pure titanium sheet is used as the cathode, and the electrode remains stable within 48 hours.

[0023] Example 2 As described in Example 1, the difference is: In step (2), 50 mg RuO2 nanoparticles, 150 mg stannous chloride and 88 mg citric acid were added to a mixed solution of 5 mL ethylene glycol and ethanol (the volume ratio of ethylene glycol and ethanol was 7:3), and a small amount of concentrated hydrochloric acid was added dropwise. The mixture was stirred evenly to obtain the coating solution. In step (4), the adhesion test showed that a very small amount of coating powder remained on the surface of the tape, and the tape was mainly transparent; the chlorine evolution performance was measured to be 15.0 mg / L in 15 min; the stability test showed that the electrode could remain stable within 45 h.

[0024] Steps (1) and (3) are the same as in Example 1.

[0025] Example 3 As described in Example 1, the difference is: In step (2), 50 mg RuO2 nanoparticles, 0.25 mL tetrabutyl titanate and 88 mg citric acid are added to a mixed solution of 5 mL ethylene glycol and ethanol (the volume ratio of ethylene glycol and ethanol is 7:3), and a small amount of concentrated hydrochloric acid is added dropwise. The mixture is stirred evenly to obtain the coating solution. In step (4), the adhesion test showed that a very small amount of coating powder remained on the surface of the tape, and the tape was mainly transparent; the chlorine evolution performance was measured to be 12.64 mg / L after 15 min; the stability test showed that the electrode could remain stable within 45 h.

[0026] Steps (1) and (3) are the same as in Example 1.

[0027] Comparative Example 1 As described in Example 1, the difference is: In step (2), 5 mg of RuO2 nanoparticles were added to 950 μL and 50 μL of Nafion solution and sonicated for 1 h to obtain a coating solution; In step (3), the coating liquid in (2) is drop-coated onto the titanium sheet treated in (1). Each time it is coated, it needs to be air-dried naturally before the next coating is carried out. By weighing the titanium sheet before coating and the electrode after the last coating, the mass of RuO2 nanoparticles coated on the titanium sheet is ensured to be consistent with that in Example 1. After the last coating is air-dried, the RuO2 / Ti electrode prepared by physical bonding method is obtained. In step (4), the electrode prepared by the physical bonding method in (3) was subjected to surface morphology and phase analysis, and adhesion, chlorine evolution performance and stability tests were performed. Surface morphology analysis showed that the electrode coating had a small number of cracks, and no nanoparticle RuO2 was observed in the coating. Large particle agglomeration and blocky bodies were mainly observed. Phase analysis showed that the main component of the coating was crystalline RuO2. Adhesion test showed that a lot of coating powder was obviously left on the tape surface, and the tape turned black. The chlorine evolution performance was measured to be 6.75 mg / L after 15 min. Stability test showed that the electrode remained stable only within 4 min.

[0028] Step (1) is the same as in Example 1.

[0029] Comparative Example 2 As described in Example 1, the difference is: In step (2), 50 mg RuO2 nanoparticles, 128 mg manganese sulfate and 88 mg citric acid were added to a mixed solution of 5 mL ethylene glycol and ethanol (the volume ratio of ethylene glycol to ethanol was 7:3), and a small amount of concentrated hydrochloric acid was added dropwise. The mixture was stirred evenly to obtain the coating solution. In step (4), the adhesion test showed that a lot of coating powder remained on the surface of the tape, and some areas of the tape turned black; the chlorine evolution performance was measured to be 6.5 mg / L after 15 min; the stability test showed that the electrode remained stable only within 10 min.

[0030] Steps (1) and (3) are the same as in Example 1.

[0031] Comparative Example 3 As described in Example 1, the difference is: In step (2), 50 mg RuO2 nanoparticles and 88 mg citric acid were added simultaneously to a mixed solution of 5 mL ethylene glycol and ethanol (the volume ratio of ethylene glycol to ethanol was 7:3), and a small amount of concentrated hydrochloric acid was added dropwise. The mixture was stirred evenly to obtain the coating solution. In step (4), the adhesion test showed that a lot of coating powder remained on the surface of the tape, and the tape turned black; the chlorine evolution performance was measured to be 5.05 mg / L after 15 min; the stability test showed that the electrode remained stable only within 10 min.

[0032] Steps (1) and (3) are the same as in Example 1.

[0033] Comparative Example 4 As described in Example 1, the difference is: In step (2), 0.933 g of ruthenium trichloride, 3.58 mL of tetrabutyl titanate and 1.1 mL of hydrochloric acid were added to 30 mL of anhydrous ethanol, and a small amount of concentrated hydrochloric acid was added dropwise. The mixture was stirred until homogeneous to obtain the coating solution. In step (3), the coating solution in (2) is applied to the titanium sheet treated in (1) with a brush. After each coating, the coated electrode is dried under an infrared lamp, and then placed in a muffle furnace at 500°C for thermal oxidation in air atmosphere for 10 min. Finally, it is taken out and cooled to room temperature before the next coating. By weighing the mass of the titanium sheet before coating and the mass of the electrode after the last coating, the mass of RuO2 coated on the titanium sheet is ensured to be consistent with that in Example 1. After the last coating, the electrode is placed in a muffle furnace at 500°C for calcination in air atmosphere for 1 h. After naturally cooling to room temperature in the furnace, the electrode is taken out to obtain the electrode prepared according to the commercial chlorine evolution DSA electrode preparation method. In step (4), surface morphology analysis showed that the electrode coating was discontinuous, had obvious cracks, and had no nanoparticle structure; phase analysis showed that the main component of the coating was RuO2-TiO2 solid solution; adhesion test showed that there was almost no coating powder residue on the tape surface, and the tape was still transparent; chlorine evolution performance was measured to be 7.07 mg / L after 15 min; stability test showed that the electrode remained stable within 45 h.

[0034] Step (1) is the same as in Example 1. Note: The RuO2 nanoparticles described in Examples 1-3 and Comparative Examples 1-3 were all prepared by thermal decomposition: a certain amount of RuCl3·3H2O was dissolved in 10 mL of anhydrous ethanol, mixed to form a homogeneous solution, and then the solution was dried in an oven at 120°C. After the ethanol was completely evaporated, it was calcined in a muffle furnace at 500°C for 3 h. After naturally cooling to room temperature, it was ground uniformly to obtain RuO2 nanoparticles with an average particle size of about 140 nm.

[0035] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing an electrode using interfacial sintering to enhance the adhesion between RuO2 and a titanium substrate, comprising the following steps: (1) Titanium substrate pretreatment: After polishing the titanium substrate with sandpaper, it is placed in acetone, anhydrous ethanol and deionized water for ultrasonic cleaning for 10-30 min in sequence. Then it is placed in oxalic acid solution (mass fraction of 10%), heated to a slight boil for acid etching for 1-2 h, then cleaned with deionized water, and finally the treated titanium substrate is placed in anhydrous ethanol for storage. (2) Preparation of coating solution: Add a certain amount of RuO2 nanoparticles, non-precious metal precursor and citric acid to an organic solvent at the same time, and add a small amount of concentrated hydrochloric acid dropwise. Stir evenly to obtain coating solution. (3) Electrode coating and calcination: The coating solution in (2) is applied to the titanium substrate treated in (1) by brush. After each coating, the coated electrode is dried under an infrared lamp. Then the electrode is placed in a muffle furnace at 450-550℃ and thermally oxidized in air atmosphere for 5-10 min. After that, it is taken out and cooled to room temperature before the next coating is performed. This process is repeated 8-12 times. After the last coating, the electrode is placed in a muffle furnace at 450-550℃ and calcined in air atmosphere for 1-2 h. After naturally cooling to room temperature in the furnace, the RuO2 / Ti electrode is obtained. (4) Electrode performance testing: The RuO2 / Ti electrode prepared in (3) was subjected to surface morphology and phase analysis, and adhesion, chlorine evolution performance and stability tests were performed; adhesion was tested by a simple tape pull-out method, in which the tape was applied to the electrode surface and then peeled off. The less coating powder left on the tape surface, the better the adhesion; chlorine evolution performance was tested at 50 mM NaCl, pH 7, 10 mA / cm 2 The stability test was conducted under the following conditions: 1 M H₂SO₄, 100 mA / cm⁻¹. 2 Under the conditions.

2. The preparation method according to claim 1, characterized in that, The non-precious metal precursor in the coating solution in step (2) is tetrabutyl titanate or stannous chloride; the molar ratio of the non-precious metal precursor to RuO2 is (3-7.5):3, and the total concentration of non-precious metal and Ru in the coating solution is 0.15-0.28 mol / L.

3. The preparation method according to claim 1, characterized in that, The RuO2 nanoparticles mentioned in step (2) include, but are not limited to, RuO2 nanoparticles synthesized by hydrothermal method, RuO2 nanoparticles prepared by thermal decomposition method, commercially purchased RuO2 nanoparticles, and RuO2 nanoparticles modified by doping with elements such as Cr, Zn, Ir, Al, N, Rh, or Si.

4. The preparation method according to claim 1, characterized in that, The citric acid in step (2) has a mass fraction of 2-3 wt% in the solvent.

5. The preparation method according to claim 1, characterized in that, The organic solvent mentioned in step (2) is a mixed solution of ethylene glycol and ethanol, with a volume ratio of ethylene glycol to ethanol of 7:

3.

6. The preparation method according to claim 1, characterized in that, In step (3), after each coating and drying, the electrode is thermally oxidized in a muffle furnace at 450-550℃ for 5-10 min; the electrode after the last coating is calcined in a muffle furnace at 450-550℃ for 1-2 h.

7. The preparation method according to claim 1, characterized in that, The RuO2 / Ti electrode coating is complete and continuous without cracks. The RuO2 in the coating maintains a nanostructure and has strong adhesion to the titanium substrate.

8. The preparation method according to claim 1, characterized in that, The prepared RuO2 / Ti electrode exhibits high catalytic activity and good stability. Compared with the RuO2 / Ti electrode prepared by the physical bonding method, the prepared RuO2 / Ti electrode has an 80%-140% higher electrochemical chlorine evolution yield and a stability of 45-55 h, which is much higher than the stability of the RuO2 / Ti electrode prepared by the physical bonding method (only 4-10 min).

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