A nitrogen-doped-ruthenium dioxide-titania coated titanium electrode and a method for preparing the same

Abstract

The application belongs to the technical field of inorganic materials, and discloses a nitrogen-doped RuO2-TiO2-coated titanium electrode and a preparation method thereof. 3+ , Ti 3+ , thereby improving the chlorine evolution activity and service life of the electrode; compared with a conventional RuO2-TiO2-coated titanium electrode without nitrogen doping, the nitrogen-doped RuO2-TiO2-coated titanium electrode has a chlorine evolution yield increased by 20%-80% and a service life increased by 50%-150%. The application further provides a preparation method of the nitrogen-doped RuO2-TiO2-coated titanium electrode, which is prepared by adding a nitrogen-containing precursor into a coating solution and adopting a surface coating method to perform annealing. The application has simple process equipment and strong operability, and is suitable for large-scale production.

Description

Technical Field

[0001] The invention relates to a nitrogen-doped-RuO2-TiO2 coating titanium electrode and a preparation method thereof, belonging to the technical field of inorganic materials. Background Art

[0002] RuO2-TiO2-coated titanium electrodes, as anodes, can electrocatalytically convert chloride ions in water into dissolved elemental chlorine, hypochlorous acid, hypochlorite, and other free chlorine. They also possess advantages such as high mechanical strength, dimensional stability, and corrosion resistance, making them the most widely used chlorine evolution electrodes in modern chemical engineering, the chlor-alkali industry, and water treatment and disinfection. The electrocatalytic activity and electrode life of RuO2-TiO2-coated titanium electrodes are important indicators for evaluating electrode performance. The chemical valence and occurrence form of Ru, Ti, and O in the RuO2-TiO2 coating are closely related to the electrode's catalytic activity. Zhang et al. prepared RuO2 electrocatalysts enriched in oxygen vacancies by combining sodium alginate with ruthenium ions and found that oxygen vacancies enhance RuO2's electrocatalytic oxygen evolution activity [Angew. Chem. Int. Ed. 2021, 60, 18821–18829]. However, the method described in this paper prepares RuO2 powder particles and loads them onto a glassy carbon electrode for testing, making it suitable only for laboratory-scale characterization and analysis and unsuitable for practical applications. Furthermore, the current method for increasing the service life of RuO2-TiO2-coated titanium electrodes primarily involves adding the precious metal iridium (Ir) to the coating. However, Ir reserves in the Earth's crust are only one ten-millionth of a ton, making it extremely expensive. Therefore, new methods are urgently needed to enhance the electrocatalytic activity and lifetime of RuO2-TiO2-coated titanium electrodes. Summary of the Invention

[0003] The present invention provides a nitrogen-doped modified RuO2-TiO2 coated titanium electrode (nitrogen-doped-RuO2-TiO2 coated titanium electrode) and a preparation method thereof. The prepared electrode has rich Ru 3+ 、Ti 3+ , and oxygen vacancy active sites, resulting in high chlorine evolution activity and a long service life. The nitrogen-doped RuO2-TiO2-coated titanium electrode is prepared by in-situ introduction of a nitrogen-containing precursor into the RuO2-TiO2 coating solution, a method known as in-situ modification of the coating solution. This method does not require changes to the existing electrode preparation process and is easily scaled up for production.

[0004] The technical solutions of the present invention are as follows:

[0005] A nitrogen-doped RuO2-TiO2 coated titanium electrode is prepared by annealing a surface coating method. The electrode is characterized in that the electrode has a uniform and complete active coating, and the active component of the coating is nitrogen-doped RuO2-TiO2; the nitrogen element is evenly distributed in the active coating, and the nitrogen doping makes the active coating rich in RuO2-TiO2.3+ 、Ti 3+ , and oxygen vacancy active sites, so that the electrode has a higher chlorine evolution yield and a longer service life. 2 Under the conditions of enhanced life test at 40°C, the life of the nitrogen-doped-RuO2-TiO2-coated titanium electrode was increased by 50%-150% compared to the RuO2-TiO2-coated titanium electrode. The nitrogen-doped-RuO2-TiO2-coated titanium electrode has the characteristics of high chlorine evolution yield and long life.

[0006] A method for preparing a nitrogen-doped-RuO2-TiO2 coated titanium electrode is as follows:

[0007] (1) Pretreatment of titanium substrate

[0008] The titanium substrate was placed in an annealing furnace for annealing to eliminate stress, and after cooling to room temperature, it was sandblasted, cleaned with acetone for oil removal, etched with oxalic acid, and cleaned with deionized water. The treated titanium substrate was placed in anhydrous ethanol for storage.

[0009] The titanium substrate is a titanium mesh or a titanium sheet; the annealing furnace temperature is set at 400-600°C and the holding time is 10-60 minutes; the acid etching is to boil the titanium substrate in slightly boiling oxalic acid for 1-2 hours, and the mass fraction of the oxalic acid solution used for acid etching is 10%-15%.

[0010] (2) Preparation of coating liquid

[0011] Add a certain amount of nitrogen-containing precursor to anhydrous ethanol, stir and dissolve at 10-60°C, then add a certain amount of tetrabutyl titanate and ruthenium trichloride, and dropwise add a small amount of concentrated hydrochloric acid, stir evenly, to obtain a coating liquid;

[0012] The nitrogen-containing precursor is ammonium chloride, dicyandiamide, or imidazole, and the mass fraction of the nitrogen-containing precursor in the coating liquid is 0.1wt%-10wt%;

[0013] The molar ratio of tetrabutyl titanate to ruthenium trichloride added to the coating solution is (7-9):(3-1), and the total concentration of Ti and Ru in the coating solution is 0.1-0.5 mol / L;

[0014] (3) Electrode coating and calcination

[0015] The coating liquid in (2) is applied to the titanium substrate treated in (1) using a brush or a dip coating machine. Each time the coating is applied, the coated electrode is dried under an infrared lamp for 10-15 minutes, and then the electrode is placed in a muffle furnace at 400-600°C and thermally oxidized in an air atmosphere for 10-15 minutes. Finally, the electrode is taken out and cooled to room temperature before the next coating is applied. This is repeated 6-15 times.

[0016] The electrode after the last coating is placed in a muffle furnace at 400-600° C. and calcined in an air atmosphere for 1-2 hours. After naturally cooling to room temperature in the furnace, it is taken out to obtain a nitrogen-doped-RuO2-TiO2 coated titanium electrode.

[0017] The pulling speed of the immersion and pulling coating machine is 500-1000 μm / s;

[0018] The nitrogen content in the nitrogen-doped-RuO2-TiO2 coating titanium electrode is 1wt%-15wt%, and the nitrogen is evenly distributed in the coating; doping with nitrogen increases the activity of RuO2 in the chlorine evolution active site in the electrode. 3+ 、Ti 3+ , and the number of oxygen vacancies;

[0019] (4) Electrode performance test

[0020] The electrode prepared in (3) was tested for chlorine evolution performance and stability. The chlorine evolution performance test was carried out at 50 mM NaCl, pH 7, 10 mA / cm 2 The stability test was carried out under the conditions of 1M H2SO4, 2A / cm 2 , carried out under the conditions of 40℃;

[0021] Compared with the traditional RuO2-TiO2 coated titanium electrode which is not nitrogen-doped, the nitrogen-doped-RuO2-TiO2 coated titanium electrode has a chlorine evolution output increased by 20%-80% and a strengthened service life increased by 50%-150%.

[0022] The technical features of the present invention are as follows:

[0023] 1. The present invention uses nitrogen-containing precursors to nitrogen-dope the electrode coating liquid. The nitrogen atoms in the nitrogen-containing precursors react with Ru 3+ Chelation, so that the nitrogen-containing precursor in the coating solution and Ru 3+ A stable and uniform dispersion is formed, thereby obtaining a nitrogen-doped-RuO2-TiO2 coated titanium electrode uniformly doped with N element.

[0024] 2. The selection of nitrogen-containing precursors in the present invention plays an important role in the preparation of electrodes. The nitrogen-containing precursors selected in this patent include but are not limited to ammonium chloride (slightly soluble in ethanol), imidazole (easily soluble in ethanol), and dicyandiamide (easily soluble in ethanol). The above three nitrogen-containing precursors are all reducing. During the thermal oxidation process, their reducing properties promote the formation of low-valent Ti in the TiO2-RuO2 coating. 3+ 、Ru 3+ ; Furthermore, the low-valent Ti in the RuO2-TiO2 lattice 3+ 、Ru 3+ Promoting the generation of oxygen vacancies. TiO2-RuO2 low valence Ti3+ 、Ru 3+ , and oxygen vacancies significantly improved the chlorine evolution activity and stability of the electrode.

[0025] 3. The mass fraction of the nitrogen-containing precursor in the coating liquid in the patent of this invention is 0.1wt%-10wt%. When the mass fraction is too low, the electrode performance is not significantly improved due to the low N doping amount; when the mass fraction is too high, there are problems such as insufficient dissolution of the nitrogen-containing precursor and excessive chelation with metal ions, which destroys the uniformity of the coating liquid.

[0026] 4. In the present invention, the content of N in the coating is 1wt%-15wt%; the N in the coating is evenly distributed and incorporated into the lattice in the form of O-Ti-N; the incorporation of N stabilizes the oxygen vacancies and Ru in the coating. 3+ 、Ti 3+ , thereby increasing the chlorine evolution activity and life of the electrode; compared with the traditional RuO2-TiO2 coated titanium electrode without nitrogen doping, the nitrogen-doped-RuO2-TiO2 coated titanium electrode has a chlorine evolution yield increased by 20%-80% and an enhanced life increased by 50%-150%.

[0027] 5. The pretreatment process of the titanium substrate includes an annealing step to eliminate thermal stress, which helps to slow down the generation of coating cracks caused by thermal stress during the coating brushing-drying-calcination process. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a scanning electron microscope photograph of the nitrogen-doped-RuO2-TiO2 coated titanium electrode in Example 1;

[0029] Figure 2 This is the EDS distribution diagram of the nitrogen-doped-RuO2-TiO2 coated titanium electrode in Example 1;

[0030] Figure 3 This is the EDS spectrum result of the nitrogen-doped-RuO2-TiO2 coated titanium electrode in Example 2;

[0031] Figure 4 The XPS results of the electrodes in Example 2 and the comparative example are as follows: the Ru peak and the Ti peak move toward the low energy direction, indicating that Ru 3+ With Ti 3+ Increased content; V The increase in the (oxygen vacancy) peak area indicates an increase in the oxygen vacancy content; the N peak at 398.6 eV indicates that N exists in the electrode coating in the form of O-Ti-N;

[0032] Figure 5 is the electrode chlorine evolution yield in Example 3 and the comparative example;

[0033] Figure 6This is the accelerated life experiment of the electrodes in Example 3 and the comparative example. DETAILED DESCRIPTION

[0034] The present invention will be described in detail below with reference to specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0035] Example 1

[0036] (1) Pretreatment of titanium substrate

[0037] The titanium mesh was placed in an annealing furnace at 500°C for 30 minutes to eliminate stress. After cooling to room temperature, it was sandblasted and cleaned with acetone for degreasing. Then, it was boiled in slightly boiling oxalic acid (15% mass fraction) for 2 hours and then washed with deionized water. Finally, the treated titanium mesh was placed in anhydrous ethanol for storage.

[0038] (2) Preparation of coating liquid

[0039] 0.32 g of dicyandiamide was added to 100 mL of anhydrous ethanol and stirred at 60°C to dissolve. Then, 11.93 mL of tetrabutyl titanate and 3.11 g of ruthenium trichloride were added, and 3.3 mL of concentrated hydrochloric acid was added dropwise. The mixture was stirred evenly to obtain a coating solution.

[0040] (3) Electrode coating and calcination

[0041] The coating liquid in (2) is applied to the titanium mesh treated in (1) with a brush. Each time the coating is applied, the coated electrode is dried under an infrared lamp for 10 minutes, and then the electrode is placed in a muffle furnace at 450°C for thermal oxidation in an air atmosphere for 10 minutes. Finally, the electrode is taken out and cooled to room temperature before the next coating is applied. This is repeated 15 times.

[0042] The electrode after the last coating was placed in a muffle furnace at 450°C and calcined in air atmosphere for 1 hour. After cooling naturally to room temperature in the furnace, it was taken out to obtain a nitrogen-doped-RuO2-TiO2 coated titanium electrode. The nitrogen content in the coating was 4.25 wt%.

[0043] (4) Electrode performance test

[0044] The electrode prepared in (3) was tested for chlorine evolution performance and stability. The chlorine evolution performance test was carried out at 50 mM NaCl, pH 7, 10 mA / cm 2 The results show that the chlorine evolution yield of the RuO2-TiO2 coated titanium electrode prepared under the same conditions was 24.8 mg / L in 30 minutes. The chlorine evolution yield of the RuO2-TiO2 coated titanium electrode without nitrogen doping was 20.2 mg / L in 30 minutes. The chlorine evolution yield of the nitrogen-doped RuO2-TiO2 coated titanium electrode was 22.8% higher than that of the RuO2-TiO2 coated titanium electrode.

[0045] The stability test adopts the enhanced life experiment, in 1M H2SO4, 2A / cm 2 The prepared nitrogen-doped-RuO2-TiO2 coated titanium electrode was cut into 1×1 cm 2 The size of the RuO2-TiO2 titanium electrode was used as the anode and the pure titanium sheet was used as the cathode. The life span was measured to be 16.5h when the cell voltage rose to 20V; the life span of the RuO2-TiO2 titanium electrode without nitrogen doping prepared under the same conditions was measured to be 9.5h under this condition; the life span of the nitrogen-doped-RuO2-TiO2 titanium electrode was increased by 73.7% compared with the life span of the RuO2-TiO2 titanium electrode.

[0046] Example 2

[0047] As described in Example 1, except that:

[0048] In step (2), 0.44 g of imidazole was added to 100 mL of anhydrous ethanol and stirred at 60° C. to dissolve the mixture. Then, 11.93 mL of tetrabutyl titanate and 3.11 g of ruthenium trichloride were added, and 3.3 mL of concentrated hydrochloric acid was added dropwise. The mixture was stirred evenly to obtain a coating solution.

[0049] In step (3), the coating liquid in (2) is applied to the titanium mesh treated in (1) with a brush. Each time the coating is applied, the coated electrode is dried under an infrared lamp for 10 minutes, and then the electrode is placed in a muffle furnace at 450°C and thermally oxidized in an air atmosphere for 10 minutes. Finally, the electrode is taken out and cooled to room temperature before the next coating is applied. This is repeated 15 times.

[0050] The electrode after the last coating was placed in a muffle furnace at 450°C and calcined in air atmosphere for 1 hour. After cooling naturally to room temperature in the furnace, it was taken out to obtain a nitrogen-doped-RuO2-TiO2 coated titanium electrode. The nitrogen content in the coating was 3.65 wt%.

[0051] In step (4), the electrode prepared in (3) was subjected to a chlorine evolution performance and stability test. The chlorine evolution performance test was carried out at 50 mM NaCl, pH 7, 10 mA / cm 2 The results show that the chlorine evolution yield of the RuO2-TiO2 coated titanium electrode prepared under the same conditions was 25.2 mg / L in 30 minutes. The chlorine evolution yield of the RuO2-TiO2 coated titanium electrode without nitrogen doping was 20.2 mg / L in 30 minutes under the same conditions. The chlorine evolution yield of the nitrogen-doped RuO2-TiO2 coated titanium electrode increased by 24.8% compared with that of the RuO2-TiO2 coated titanium electrode.

[0052] The stability test adopts the enhanced life experiment, in 1M H2SO4, 2A / cm 2The prepared nitrogen-doped-RuO2-TiO2 coated titanium electrode was cut into 1×1 cm 2 The size of the RuO2-TiO2 coated titanium electrode was used as the anode and the pure titanium sheet was used as the cathode. The lifespan was measured to be 15.2h when the cell voltage rose to 20V; the lifespan of the RuO2-TiO2 coated titanium electrode prepared under the same conditions without nitrogen doping was measured to be 9.5h under this condition; the lifespan of the nitrogen doped-RuO2-TiO2 coated titanium electrode was increased by 60% compared with that of the RuO2-TiO2 coated titanium electrode.

[0053] Step (1) is the same as in Example 1.

[0054] Example 3

[0055] As described in Example 1, except that:

[0056] In step (2), 0.27 g of ammonium chloride was added to 100 mL of anhydrous ethanol and stirred at 60° C. to dissolve the mixture. Then, 11.93 mL of tetrabutyl titanate and 3.11 g of ruthenium trichloride were added, and 3.3 mL of concentrated hydrochloric acid was added dropwise. The mixture was stirred evenly to obtain a coating solution.

[0057] In step (3), the coating liquid in (2) is applied to the titanium mesh treated in (1) with a brush. Each time the coating is applied, the coated electrode is dried under an infrared lamp for 10 minutes, and then the electrode is placed in a muffle furnace at 450°C and thermally oxidized in an air atmosphere for 10 minutes. Finally, the electrode is taken out and cooled to room temperature before the next coating is applied. This is repeated 15 times.

[0058] The electrode after the last coating was placed in a muffle furnace at 450°C and calcined in air atmosphere for 1 hour. After cooling naturally to room temperature in the furnace, it was taken out to obtain a nitrogen-doped-RuO2-TiO2 coated titanium electrode. The nitrogen content in the coating was 1.45 wt%.

[0059] In step (4), the electrode prepared in (3) was subjected to a chlorine evolution performance and stability test. The chlorine evolution performance test was carried out at 50 mM NaCl, pH 7, 10 mA / cm 2 The results show that the chlorine evolution yield of the RuO2-TiO2 coated titanium electrode prepared under the same conditions was 35.0 mg / L in 30 minutes. The chlorine evolution yield of the RuO2-TiO2 coated titanium electrode without nitrogen doping was 20.2 mg / L in 30 minutes under the same conditions. The chlorine evolution yield of the nitrogen-doped RuO2-TiO2 coated titanium electrode increased by 73.3% compared with that of the RuO2-TiO2 coated titanium electrode.

[0060] The stability test adopts the enhanced life experiment, in 1M H2SO4, 2A / cm 2 The prepared nitrogen-doped-RuO2-TiO2 coated titanium electrode was cut into 1×1 cm2 The size of the RuO2-TiO2 titanium electrode was used as the anode and the pure titanium sheet was used as the cathode. The life span was measured to be 18.3h when the cell voltage rose to 20V; the life span of the RuO2-TiO2 titanium electrode without nitrogen doping prepared under the same conditions was measured to be 9.5h under this condition; the life span of the nitrogen-doped-RuO2-TiO2 titanium electrode was increased by 92.6% compared with the life span of the RuO2-TiO2 titanium electrode.

[0061] Step (1) is the same as in Example 1.

[0062] Comparative Example

[0063] As described in Example 1, except that:

[0064] In step (2), 11.93 mL of tetrabutyl titanate and 3.11 g of ruthenium trichloride were added to 100 mL of anhydrous ethanol, and 3.3 mL of concentrated hydrochloric acid was added dropwise, and the mixture was stirred to obtain a coating solution;

[0065] In step (3), the coating liquid in (2) is applied to the titanium mesh treated in (1) with a brush. Each time the coating is applied, the coated electrode is dried under an infrared lamp for 10 minutes, and then the electrode is placed in a muffle furnace at 450°C and thermally oxidized in an air atmosphere for 10 minutes. Finally, the electrode is taken out and cooled to room temperature before the next coating is applied. This is repeated 15 times.

[0066] The electrode after the last coating was placed in a muffle furnace at 450° C. and calcined in an air atmosphere for 1 hour. After naturally cooling to room temperature in the furnace, it was taken out to obtain a RuO 2 -TiO 2 coated titanium electrode that was not nitrogen-doped.

[0067] In step (4), the RuO2-TiO2 coated titanium electrode prepared in (3) without nitrogen doping was subjected to chlorine evolution performance and stability test. The chlorine evolution performance test was carried out under the conditions of 50 mM NaCl, pH 7, 10 mA / cm 2 The experiment was carried out under the conditions of 100 nm and the chlorine evolution yield in 30 min was measured to be 20.2 mg / L.

[0068] The stability test adopts the enhanced life experiment, in 1M H2SO4, 2A / cm 2 The prepared RuO2-TiO2-coated titanium electrode without nitrogen doping was cut into 1×1 cm 2 The size is used as the anode and the pure titanium sheet as the cathode. The life is measured to be 9.5h when the cell voltage rises to 20V.

[0069] Step (1) is the same as in Example 1.

Claims

1. A method for preparing a nitrogen-doped RuO2-TiO2 coated titanium electrode, comprising the following steps: (1) Pretreatment of titanium substrate The titanium substrate was placed in an annealing furnace for annealing to eliminate stress, and after cooling to room temperature, it was sandblasted, cleaned with acetone for oil removal, etched with oxalic acid, and cleaned with deionized water. The treated titanium substrate was placed in anhydrous ethanol for storage. The titanium substrate is a titanium mesh or a titanium sheet; the annealing furnace temperature is set to 400-600°C, and the holding time is 10-60 minutes; the acid etching is performed by placing the titanium substrate in slightly boiling oxalic acid for 1-2 hours, and the mass fraction of the oxalic acid solution used for acid etching is 10%-15%; (2) Preparation of coating liquid Add a certain amount of nitrogen-containing precursor to anhydrous ethanol, stir and dissolve at 10-60°C, then add a certain amount of tetrabutyl titanate and ruthenium trichloride, and dropwise add a small amount of concentrated hydrochloric acid, stir evenly, to obtain a coating liquid; The nitrogen-containing precursor is ammonium chloride, dicyandiamide, or imidazole, and the mass fraction of the nitrogen-containing precursor in the coating liquid is 0.1wt%-10wt%; The molar ratio of tetrabutyl titanate to ruthenium trichloride added to the coating solution is (7-9):(3-1), and the total concentration of Ti and Ru in the coating solution is 0.1-0.5 mol / L; (3) Electrode coating and calcination The coating liquid in (2) is applied to the titanium substrate treated in (1) using a brush or a dip coating machine. Each time the coating is applied, the coated electrode is dried under an infrared lamp for 10-15 minutes, and then the electrode is placed in a muffle furnace at 400-600°C and thermally oxidized in an air atmosphere for 10-15 minutes. Finally, the electrode is taken out and cooled to room temperature before the next coating is applied. This is repeated 6-15 times. The electrode after the last coating is placed in a muffle furnace at 400-600° C. and calcined in an air atmosphere for 1-2 hours. After naturally cooling to room temperature in the furnace, it is taken out to obtain a nitrogen-doped-RuO2-TiO2 coated titanium electrode. The pulling speed of the immersion coating machine is 500-1000 μm / s; the nitrogen content in the nitrogen-doped-RuO2-TiO2 coated titanium electrode is 1wt%-15wt%, and the nitrogen is evenly distributed in the coating. The doping of nitrogen increases the chlorine evolution active site Ru in the electrode. 3+ 、Ti 3+ , and the number of oxygen vacancies, the electrode doped with nitrogen has high chlorine evolution activity and long life; (4) Electrode performance test The electrode prepared in (3) was tested for chlorine evolution performance and stability. The chlorine evolution performance test was carried out in 50 mM NaCl aqueous solution, pH = 7, 10 mA / cm 2 The stability test was carried out under the conditions of 1M H2SO4, 2A / cm 2 , carried out under the conditions of 40℃; Compared with the traditional RuO2-TiO2 coated titanium electrode without nitrogen doping, the nitrogen doped-RuO2-TiO2 coated titanium electrode has a chlorine evolution output increased by 20%-80% and a strengthened service life increased by 50%-150%.

2. The preparation method according to claim 1, wherein In the step (1), the titanium substrate is first placed in an annealing furnace for annealing to eliminate stress. The annealing furnace temperature is 500° C. and the holding time is 60 minutes.

3. The preparation method according to claim 1, wherein In the step (2), the type of nitrogen-containing precursor is ammonium chloride, dicyandiamide or imidazole, and the mass fraction of the nitrogen-containing precursor in the coating liquid is 0.1wt%-10wt%; the nitrogen atoms in the nitrogen-containing precursor react with Ru 3+ Chelation, so that the nitrogen-containing precursor in the coating solution and Ru 3+ A stable and uniform dispersion is formed, thereby obtaining a nitrogen-doped-RuO2-TiO2 coated titanium electrode uniformly doped with N element.

4. The preparation method according to claim 1, wherein In the step (2), the molar ratio of tetrabutyl titanate to ruthenium trichloride added to the coating liquid is 7:3, 8:2 or 9:1, and the total concentration of Ti and Ru in the coating liquid is 0.1-0.5 mol / L.

5. The preparation method according to claim 1, wherein In the step (3), after each coating and drying, the electrode is thermally oxidized in a muffle furnace at 450-550°C; and the electrode after the last coating is calcined in a muffle furnace at 450-550°C.

6. The preparation method according to claim 1, wherein In the nitrogen-doped RuO2-TiO2 coated titanium electrode, the N content in the coating is 1wt%-15wt%; the N element in the coating is doped into the lattice in the form of O-Ti-N; doping with nitrogen increases the Ru active site of chlorine evolution in the electrode. 3+ 、Ti 3+ , and the number of oxygen vacancies; compared with the traditional RuO2-TiO2 coated titanium electrode without nitrogen doping, the nitrogen-doped-RuO2-TiO2 coated titanium electrode has a chlorine evolution yield increased by 20%-80% and an enhanced life increased by 50%-150%.

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