Preparation method of non-noble metal and rare earth metal co-doped modified oxide composite coating

Abstract

The invention discloses a preparation method of a non-noble metal and rare earth metal co-doped modified oxide composite coating, which comprises the following steps: (1) adding SnCl4 5H2O and SbCl3 into an acid-alcohol mixed solution, and uniformly stirring to form a main metal solution; (2) respectively adding a non-noble metal modifier and a rare earth metal modifier into the main metal solution, and uniformly stirring to form an A / B precursor solution; (3) coating the surface of the Ti matrix with the A precursor solution, and performing pyrolysis-roasting to form an intermediate layer; (4) coating the surface of the intermediate layer with a B precursor solution, and performing pyrolysis-roasting to obtain a composite coating; and (5) carrying out heat treatment on the composite coating prepared in the step (4). According to the method provided by the invention, the SnO2-Sb is modified by doping the non-noble metal / rare earth metal, and the layered brushing mode is adopted, so that coating grains can be effectively refined, coating cracks are reduced, the stability of the anode is further improved, and the service life of the anode is remarkably prolonged.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical technology, specifically relating to a method for preparing a composite coating of non-precious metals and rare earth metals co-doped modified oxides. Background Technology

[0002] The anodes used in non-ferrous metal hydrometallurgical processes are mainly Pb alloy anodes. Compared with Pb alloy anodes, Ti-based coated anodes have higher corrosion resistance and lower oxygen evolution potential.

[0003] Currently, industrial Ti-based coated anodes mainly include Ti / RuO2, Ti / RuO2-SnO2, Ti / IrO2-SnO2, and Ti / Ta2O5-IrO2 anodes. These noble metal oxide coated titanium electrodes have low oxygen evolution potentials and long lifespans, but due to the consumption of large amounts of rare and precious metals, the anode manufacturing cost is too high to meet the needs of actual industrial production. Therefore, researchers have begun to turn to the study of base metal oxide coatings, such as SnO2, PbO2, and MnO2. Further research has revealed that single metal oxide coatings have drawbacks such as easy substrate passivation and short lifespan. Therefore, the research trend is to study novel composite coated anodes with intermediate and catalytic layers to improve electrode conductivity and significantly extend electrode lifespan. Using SnO2-Sb as an interlayer can improve the bonding between the substrate and the oxide coating, delay coating detachment, and prevent the formation of a TiO2 resistive film between the substrate and the coating, thus delaying coating failure. Furthermore, adding a SnO2-Sb interlayer can reduce internal resistance, improve electron transport capacity, lower the oxygen evolution potential, and enhance the catalytic activity of the electrode while saving energy. However, a single SnO2-Sb oxide coating system is prone to cracking, resulting in poor anode stability and a short lifespan, which cannot meet the actual needs of industrial production. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the main objective of this invention is to provide a method for preparing a composite coating of non-precious metal and rare earth metal co-doped modified oxides with corrosion resistance and long service life. This method has simple process steps and low cost. By modifying SnO2-Sb with non-precious metal elements and rare earth metals, the stability of the composite coating is significantly improved, and the service life of the anode is extended, meeting the needs of actual industrial electrolysis.

[0005] The objective of this invention is achieved through the following technical solution: A method for preparing a composite coating of non-precious metals and rare earth metals co-doped modified oxides includes the following steps: (1) Add SnCl4 5H2O and SbCl3 to the acid and alcohol mixture and stir until homogeneous to form a main metal solution; (2) Add a non-precious metal modifier to the main metal solution prepared in step (1) and stir until homogeneous to form precursor solution A; and add a rare earth metal modifier to the main metal solution prepared in step (1) and stir until homogeneous to form precursor solution B. (3) Coat the A precursor solution prepared in step (2) onto the surface of the Ti substrate, pyrolyze-calcine, and then coat-pyrolyze-calcine again. Repeat this process multiple times until the coating thickness formed by the A precursor solution reaches the required thickness and an intermediate layer is formed. (4) Coat the B precursor solution prepared in step (2) onto the surface of the intermediate layer, pyrolyze-calcine, and then coat-pyrolyze-calcine again. Repeat this process multiple times until the coating thickness formed by the B precursor solution reaches the required level, and obtain a composite coating. (5) Heat treatment is performed on the composite coating prepared in step (4) to obtain a composite coating of non-precious metal and rare earth metal co-doped modified oxide.

[0006] In some specific embodiments, the coating-pyrolysis-calcination cycle is repeated 10-70 times; In some specific implementations, the acid in step 1) is one or a mixture of concentrated hydrochloric acid or concentrated nitric acid, and the alcohol is one or more of ethanol, n-butanol or isopropanol, and the volume ratio of the alcohol to the acid is 1.5-1:1.

[0007] In some specific implementations, SnCl4 5H2O and SbCl3 mentioned in step 1) contain Sn 2+ Sb 3+ The molar ratio is 10~20:1.

[0008] In some specific implementations, the Ti substrate is also pretreated, specifically by boiling the Ti substrate in an alkaline aqueous solution to degrease it, and then etching the Ti substrate in an acidic aqueous solution.

[0009] Furthermore, the alkaline aqueous solution is a 5-15 wt% NaOH aqueous solution, and the acidic aqueous solution is a 5-15 wt% oxalic acid aqueous solution; In some specific embodiments, the roughness of the pretreated Ti substrate is 7.5 μm to 8.5 μm.

[0010] In some specific embodiments, the concentration of the main metal solution in step 1) is 0.425-1.70 g / ml.

[0011] In some specific implementations, the non-precious metal modifier mentioned in step 2) is one or more of Ni(NO3)26H2O, Co(NO3)26H2O, and Mn(NO3)26H2O.

[0012] In some specific implementations, the rare earth metal modifier mentioned in step 2) is one or more of La(NO3)36H2O, Ce(NO3)36H2O, and Nd(NO3)26H2O.

[0013] In some specific implementations, the non-precious metal ions in the non-precious metal modifier described in step 2) react with Sn. 2+ The molar ratio is 1-5:100; the rare earth metal ions in the rare earth metal modifier react with Sn. 2+ The molar ratio is 0.01-0.08:100.

[0014] In some specific implementations, in the pyrolysis-calcination process of steps 3) and 4), the process parameters of pyrolysis are 70~100℃ and the time is 5~30 min; the process parameters of calcination are 400~500℃ and the time is 10~30 min.

[0015] In some specific implementations, the process parameters for the heat treatment in step 5) are: the heat treatment temperature is 400~500℃ and the time is 1~3h.

[0016] Compared with the prior art, the present invention has at least the following advantages: 1) The composite coating of non-precious metal and rare earth metal co-doped modified oxide provided by the present invention uses non-precious metals as the materials and does not contain precious metals. The raw materials are low in cost and the coating is prepared by coating method. The preparation of materials is simple. 2) The method provided by the present invention modifies SnO2-Sb by doping with non-precious metal elements and SnO2-Sb by doping with rare earth metals, and then adopts a layered coating method, which not only effectively refines the coating grains, but also effectively reduces coating cracks, thereby improving the stability of the anode and significantly extending the service life of the anode. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0018] When a quantity, concentration, or other value or parameter is described as a range, preferred range, or preferred upper and lower limits, it should be understood that it is equivalent to specifically disclosing any range by combining any pair of upper or preferred values ​​with any lower or preferred values, regardless of whether the range is specifically disclosed. Unless otherwise stated, the numerical range values ​​listed herein include the endpoints of the range and all integers and fractions within that range.

[0019] Unless otherwise stated, all percentages, parts, ratios, etc. in this document are by weight.

[0020] The materials, methods, and embodiments described herein are exemplary and should not be construed as limiting unless otherwise stated.

[0021] Example 1 This embodiment provides a method for preparing a composite coating of non-noble metals and rare earth metals co-doped modified oxides, which includes the following steps: 1) First, the Ti matrix was boiled in a 5 wt.% NaOH aqueous solution to degrease it, and then the Ti matrix was etched to 7.89 μm in a 5 wt.% oxalic acid aqueous solution; 2) Preparation of precursor solution A a) Mix SnCl4 5H2O and SbCl3 according to Sn 2+ :Sb 3+ A molar ratio of 15:1 was added to a mixed solution of n-butanol and concentrated hydrochloric acid with a volume ratio of 4:2 and stirred until homogeneous to form the main metal (Sn). 2+ Sb 3+ Solution A (hereinafter the same) has a concentration of 0.5 g / ml; b) Mix Mn(NO3)26H2O according to Mn 2+ With Sn 2+ A mixture of 1.5:100 molar ratios was added to solution A and stirred until homogeneous to obtain solution A. c) Ce(NO3)36H2O is disposed of according to Ce... 3+ With Sn 2+ A molar ratio of 0.03:100 is added to the A mixed solution in step b) and stirred until homogeneous to form the A precursor solution; 3) Preparation of precursor solution B a) Mix SnCl4 5H2O and SbCl3 according to Sn 2+ :Sb 3+ The solution was added to a mixed solution of n-butanol and concentrated hydrochloric acid with a molar ratio of 15:1 and stirred until homogeneous to form solution B with a main metal concentration of 1.0 g / ml. b) Mix Mn(NO3)26H2O according to Mn2+ With Sn 2+ A mixture of 1.5:100 molar ratios was added to solution B and stirred until homogeneous to obtain solution B. c) Ce(NO3)36H2O is disposed of according to Ce... 3+ With Sn 2+ A molar ratio of 0.03:100 was added to the B mixed solution in step b) and stirred until homogeneous to form the B precursor solution; 4) First, use a brush to apply the A precursor solution evenly to the Ti substrate surface. Then, heat treat it at 100℃ for 10 minutes, and then at 450℃ for 15 minutes. Repeat this process 50 times to form an intermediate layer. 5) Then use a brush to apply the B precursor solution evenly to the surface of the intermediate layer in step 4). First, heat treat it at 100℃ for 10 min, then treat it at 450℃ for 15 min. Repeat this process 10 times to obtain a composite coating. 6) Finally, the composite coating is heat-treated at 500℃ for 1 h to obtain the composite coating of non-precious metal and rare earth metal co-doped modified oxide.

[0022] Example 2 This embodiment provides a method for preparing a composite coating of non-noble metals and rare earth metals co-doped modified oxides, which includes the following steps: 1) First, the Ti matrix was boiled in a 10 wt.% NaOH aqueous solution to remove the oil, and then the Ti matrix was etched to 7.89 μm in a 10 wt.% oxalic acid aqueous solution; 2) Preparation of precursor solution A a) Mix SnCl4 5H2O and SbCl3 according to Sn 2+ :Sb 3+ The solution was added to a mixed solution of n-butanol and concentrated hydrochloric acid with a molar ratio of 10:1 and stirred until homogeneous to form solution A with a main metal concentration of 1.7 g / ml. b) Mix Mn(NO3)26H2O according to Mn 2+ With Sn 2+ A mixture of 2.5:100 molar ratios was added to solution A and stirred until homogeneous to obtain solution A. c) Ce(NO3)36H2O is disposed of according to Ce... 3+ With Sn 2+ A molar ratio of 0.06:100 is added to the A mixed solution in step b) and stirred until homogeneous to form the A precursor solution; 3) Preparation of precursor solution B a) Mix SnCl4 5H2O and SbCl3 according to Sn 2+ :Sb3+ The solution was added to a mixed solution of n-butanol and concentrated hydrochloric acid with a molar ratio of 10:1 and stirred until homogeneous to form solution B with a main metal concentration of 0.85 g / ml. b) Mix Mn(NO3)26H2O according to Mn 2+ With Sn 2+ A mixture of 2.5:100 molar ratios was added to solution B and stirred until homogeneous to obtain solution B. c) Ce(NO3)36H2O is disposed of according to Ce... 3+ With Sn 2+ A molar ratio of 0.06:100 was added to the B mixed solution in step b) and stirred until homogeneous to form the B precursor solution; 4) First, use a brush to apply the A precursor solution evenly to the Ti substrate surface. Then, heat treat it at 100℃ for 5 minutes, and then at 500℃ for 10 minutes. Repeat this process 50 times to form an intermediate layer. 5) Then, use a brush to apply the B precursor solution evenly to the surface of the intermediate layer in step 4). First, heat treat it at 100°C for 5 minutes, then treat it at 500°C for 10 minutes. Repeat this process 10 times to obtain a composite coating. 6) Finally, the composite coating is heat-treated at 500℃ for 1 h to obtain the composite coating of non-precious metal and rare earth metal co-doped modified oxide.

[0023] This application uses Example 2 as an example to test the lifetime of the composite coated anode prepared by accelerated lifetime testing, specifically: The test conditions were: the anode current density was controlled at 1 A / cm². 2 The electrolyte is 160 g / L H2SO4, and the counter electrode is 2*2 cm. 2 The platinum electrode is used as the reference electrode, which is a saturated calomel electrode. The electrode is considered to be in failure when the electrode voltage exceeds 10V.

[0024] The measured failure lifetime of the coated anode was 70502 s. According to the accelerated lifetime formula t2=(J2 / J1), n t1 (where t1 is the accelerated lifetime, t2 is the actual lifetime, J2 is the accelerating current density, J1 is the actual current density, and n is a constant equal to 2) is used to obtain the electrode at 50 mA / cm 2 Its lifespan is 7833.55 hours.

[0025] Example 3 This embodiment provides a method for preparing a composite coating of non-noble metals and rare earth metals co-doped modified oxides, which includes the following steps: 1) First, the Ti matrix was boiled in a 10 wt.% NaOH aqueous solution to remove the oil, and then the Ti matrix was etched to 7.89 μm in a 10 wt.% oxalic acid aqueous solution; 2) Preparation of precursor solution A a) Mix SnCl4 5H2O and SbCl3 according to Sn 2+ :Sb 3+ The solution was added to a mixed solution of n-butanol and concentrated hydrochloric acid with a molar ratio of 20:1 and stirred until homogeneous to form solution A with a main metal concentration of 1.2 g / ml. b) Mix Mn(NO3)26H2O according to Mn 2+ With Sn 2+ A mixture of 4:100 molar ratios was added to solution A and stirred until homogeneous to obtain solution A. c) Ce(NO3)36H2O is disposed of according to Ce... 3+ With Sn 2+ A molar ratio of 0.08:100 is added to the A mixed solution in step b) and stirred until homogeneous to form the A precursor solution; 3) Preparation of precursor solution B a) Mix SnCl4 5H2O and SbCl3 according to Sn 2+ :Sb 3+ The solution was added to a mixed solution of n-butanol and concentrated hydrochloric acid with a molar ratio of 20:1 and stirred until homogeneous to form solution B with a main metal concentration of 0.5 g / ml. b) Mix Mn(NO3)26H2O according to Mn 2+ With Sn 2+ A mixture of 4:100 molar ratios was added to solution B and stirred until homogeneous to obtain solution B. c) Ce(NO3)36H2O is disposed of according to Ce... 3+ With Sn 2+ A molar ratio of 0.08:100 was added to the B mixed solution in step b) and stirred until homogeneous to form the B precursor solution; 4) First, use a brush to apply the A precursor solution evenly to the Ti substrate surface. Then, heat treat it at 100℃ for 5 minutes, and then at 500℃ for 10 minutes. Repeat this process 50 times to form an intermediate layer. 5) Then use a brush to apply the B precursor solution evenly to the surface of the intermediate layer in step 4). First, heat treat it at 80°C for 15 min, then treat it at 400°C for 20 min. Repeat this process 10 times to obtain a composite coating. 6) Finally, the composite coating is heat-treated at 450℃ for 1.5 h to obtain the composite coating of non-precious metal and rare earth metal co-doped modified oxide.

[0026] Comparative Example 1 This comparative example provides a method for preparing a composite coating of oxides co-doped with non-noble metals and rare earth metals, which is basically the same as that in Example 2, except that the host metal solution is not modified by non-noble metal and rare earth metal doping. Specifically: 1) First, the Ti matrix was boiled in a 10 wt.% NaOH aqueous solution to remove the oil, and then the Ti matrix was etched to 7.89 μm in a 10 wt.% oxalic acid aqueous solution; 2) Mix SnCl4 + 5H2O and SbCl3 according to Sn 2+ :Sb 3+ The solution was added to a mixed solution of n-butanol and concentrated hydrochloric acid with a molar ratio of 10:1 and stirred until homogeneous to form solution A with a main metal concentration of 1.7 g / ml. 3) Apply solution A evenly to the Ti substrate surface with a brush, heat-treat at 100℃ for 5 min, then at 500℃ for 10 min, repeat this process 50 times, and finally heat-treat at 500℃ for 1 h to obtain the final product.

[0027] This application describes the lifetime of the composite-coated anode prepared in this comparative example, tested through accelerated lifetime testing, specifically as follows: The test conditions were: the anode current density was controlled at 1 A / cm². 2 The electrolyte is 160 g / L H2SO4, and the counter electrode is 2*2 cm. 2 The platinum electrode is used as the reference electrode, which is a saturated calomel electrode. The electrode is considered to be in failure when the electrode voltage exceeds 10V.

[0028] The measured failure lifetime of the coated anode was 59 s. According to the accelerated lifetime formula t2=(J2 / J1), n t1 (where t1 is the accelerated lifetime, t2 is the actual lifetime, J2 is the accelerating current density, J1 is the actual current density, and n is a constant equal to 2) is used to obtain the electrode at 50 mA / cm 2 Its lifespan is 6.55 hours.

[0029] Comparative Example 2 This comparative example provides a method for preparing a composite coating of oxides co-doped with non-noble metals and rare earth metals, which is basically the same as that in Example 2, except that only the host metal solution is modified with non-noble metals. Specifically: 1) First, the Ti matrix was boiled in a 10 wt.% NaOH aqueous solution to remove the oil, and then the Ti matrix was etched to 7.89 μm in a 10 wt.% oxalic acid aqueous solution; 2) Mix SnCl4 + 5H2O and SbCl3 according to Sn2+ :Sb 3+ The solution was added to a mixed solution of n-butanol and concentrated hydrochloric acid with a molar ratio of 10:1 and stirred until homogeneous to form solution A with a main metal concentration of 1.7 g / ml. 3) Mix Mn(NO3)26H2O according to Mn 2+ With Sn 2+ A mixture of 2.5:100 molar ratios was added to solution A and stirred until homogeneous to obtain solution A. 4) First, use a brush to apply the A mixed solution evenly to the Ti substrate surface. Then, heat treat it at 100℃ for 5 min, and then at 500℃ for 10 min. Repeat this process 50 times to form a composite coating. 5) Finally, the composite coating is heat-treated at 500℃ for 1 hour to obtain the final product.

[0030] This application describes the lifetime of the composite-coated anode prepared in this comparative example, tested through accelerated lifetime testing, specifically as follows: The test conditions were: the anode current density was controlled at 1 A / cm². 2 The electrolyte is 160 g / L H2SO4, and the counter electrode is 2*2 cm. 2 The platinum electrode is used as the reference electrode, which is a saturated calomel electrode. The electrode is considered to be in failure when the electrode voltage exceeds 10V.

[0031] The measured failure lifetime of the coated anode was 755 s. According to the accelerated lifetime formula t2=(J2 / J1), n t1 (where t1 is the accelerated lifetime, t2 is the actual lifetime, J2 is the accelerating current density, J1 is the actual current density, and n is a constant equal to 2) is used to obtain the electrode at 50 mA / cm 2 Its lifespan is 83.88 hours.

[0032] Comparative Example 3 This comparative example provides a method for preparing a composite coating of oxides co-doped with non-noble metals and rare earth metals, which is basically the same as that in Example 2, except that only rare earth metals are modified in the main metal solution. Specifically: 1) First, the Ti matrix was boiled in a 10 wt.% NaOH aqueous solution to remove the oil, and then the Ti matrix was etched to 7.89 μm in a 10 wt.% oxalic acid aqueous solution; 2) Mix SnCl4 + 5H2O and SbCl3 according to Sn 2+ :Sb 3+ The solution was added to a mixed solution of n-butanol and concentrated hydrochloric acid with a molar ratio of 10:1 and stirred until homogeneous to form solution A with a main metal concentration of 1.7 g / ml. 3) Ce(NO3)36H2O is disposed of according to Ce 3+ With Sn 2+ A molar ratio of 0.06:100 is added to the A mixed solution in step b) and stirred until homogeneous to form the A precursor solution; 4) First, use a brush to apply the A precursor solution evenly to the Ti substrate surface. Then, heat treat it at 100℃ for 5 minutes, and then at 500℃ for 10 minutes. Repeat this process 50 times to form a coating. 5) Finally, the coating is heat-treated at 500℃ for 1 hour to obtain the final product; This application describes the lifetime of the composite-coated anode prepared in this comparative example, tested through accelerated lifetime testing, specifically as follows: The test conditions were: the anode current density was controlled at 1 A / cm². 2 The electrolyte is 160 g / L H2SO4, and the counter electrode is 2*2 cm. 2 The platinum electrode is used as the reference electrode, which is a saturated calomel electrode. The electrode is considered to be in failure when the electrode voltage exceeds 10V.

[0033] The failure lifetime of the coated anode was measured to be 1530 s. According to the accelerated lifetime formula t2=(J2 / J1), n t1 (where t1 is the accelerated lifetime, t2 is the actual lifetime, J2 is the accelerating current density, J1 is the actual current density, and n is a constant equal to 2) is used to obtain the electrode at 50 mA / cm 2 Its lifespan is 170.00 hours.

[0034] Comparative Example 4 This comparative example provides a method for preparing a composite coating of non-precious metal and rare earth metal co-doped modified oxides. Its components and ratios are basically the same as those in Example 2, except that precursor solution B is not prepared, and only precursor solution A is prepared. Its process steps and parameters are the same as those in Example 2.

[0035] 1) First, the Ti matrix was boiled in a 10 wt.% NaOH aqueous solution to remove the oil, and then the Ti matrix was etched to 7.89 μm in a 10 wt.% oxalic acid aqueous solution; 2) Preparation of precursor solution A a) Mix SnCl4 5H2O and SbCl3 according to Sn 2+ :Sb 3+ The solution was added to a mixed solution of n-butanol and concentrated hydrochloric acid with a molar ratio of 10:1 and stirred until homogeneous to form solution A with a main metal concentration of 1.7 g / ml. b) Mix Mn(NO3)26H2O according to Mn 2+ With Sn 2+A mixture of 2.5:100 molar ratios was added to solution A and stirred until homogeneous to obtain solution A. c) Ce(NO3)36H2O is disposed of according to Ce... 3+ With Sn 2+ A molar ratio of 0.06:100 is added to the A mixed solution in step b) and stirred until homogeneous to form the A precursor solution; 3) Apply the A precursor solution evenly to the Ti substrate surface with a brush, heat-treat at 100℃ for 5 min, then treat at 500℃ for 10 min, repeat this process 50 times to form a composite coating. 4) Finally, the composite coating is heat-treated at 500℃ for 1 hour to obtain the final product.

[0036] This application describes the lifetime of the composite-coated anode prepared in this comparative example, tested through accelerated lifetime testing, specifically as follows: The test conditions were: the anode current density was controlled at 1 A / cm². 2 The electrolyte is 160 g / L H2SO4, and the counter electrode is 2*2 cm. 2 The platinum electrode is used as the reference electrode, which is a saturated calomel electrode. The electrode is considered to be in failure when the electrode voltage exceeds 10V.

[0037] The measured failure lifetime of the coated anode was 1826 s. According to the accelerated lifetime formula t2=(J2 / J1), n t1 (where t1 is the accelerated lifetime, t2 is the actual lifetime, J2 is the accelerating current density, J1 is the actual current density, and n is a constant equal to 2) is used to obtain the electrode at 50 mA / cm 2 Its lifespan is 202.88 hours.

[0038] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for preparing a composite coating of non-precious metals and rare earth metals co-doped modified oxides, characterized in that, Includes the following steps: (1) Add SnCl4 5H2O and SbCl3 to the acid and alcohol mixture and stir until homogeneous to form a main metal solution; (2) Add a non-precious metal modifier to the main metal solution prepared in step (1) and stir until homogeneous to form A precursor solution; And add rare earth metal modifier to the main metal solution prepared in step (1) and stir evenly to form B precursor solution; (3) After coating the A precursor solution prepared in step (2) onto the surface of the Ti substrate, pyrolysis-calcination is performed to form an intermediate layer; (4) After coating the B precursor solution prepared in step (2) onto the surface of the intermediate layer, pyrolyze-calcine to obtain a composite coating; (5) Heat-treat the composite coating prepared in step (4) to obtain a composite coating of non-precious metal and rare earth metal co-doped modified oxide.

2. The method for preparing a composite coating of non-noble metal and rare earth metal co-doped modified oxides according to claim 1, characterized in that, The acid mentioned in step 1) is one or a mixture of concentrated hydrochloric acid or concentrated nitric acid, and the alcohol is one or more of ethanol, n-butanol or isopropanol, and the volume ratio of the alcohol to the acid is 1.5-1:

1.

3. The method for preparing a composite coating of non-noble metals and rare earth metals co-doped modified oxides according to claim 1, characterized in that, In step 1), SnCl4 5H2O and SbCl3 contain Sn 2+ Sb 3+ The molar ratio is 10~20:

1.

4. The method for preparing a composite coating of non-noble metal and rare earth metal co-doped modified oxides according to claim 1, characterized in that, It also includes pretreatment of the Ti substrate, specifically: boiling the Ti substrate in an alkaline aqueous solution to degrease it, and then etching the Ti substrate in an acidic aqueous solution.

5. The method for preparing a composite coating of non-precious metals and rare earth metals co-doped modified oxides according to claim 4, characterized in that, The concentration of the main metal solution mentioned in step 1) is 0.425-1.70 g / ml.

6. The method for preparing a composite coating of non-noble metal and rare earth metal co-doped modified oxides according to claim 1, characterized in that, The non-precious metal modifier mentioned in step 2) is one or more of Ni(NO3)26H2O, Co(NO3)26H2O, and Mn(NO3)26H2O.

7. The method for preparing a composite coating of non-noble metal and rare earth metal co-doped modified oxides according to claim 1, characterized in that, The rare earth metal modifier mentioned in step 2) is one or more of La(NO3)36H2O, Ce(NO3)36H2O, and Nd(NO3)26H2O.

8. The method for preparing a composite coating of non-noble metal and rare earth metal co-doped modified oxides according to claim 4, characterized in that, The non-precious metal ions in the non-precious metal modifier described in step 2) react with Sn. 2+ The molar ratio is 1-5:100; the rare earth metal ions in the rare earth metal modifier react with Sn. 2+ The molar ratio is 0.01-0.08:

100.

9. The method for preparing a composite coating of non-noble metal and rare earth metal co-doped modified oxides according to claim 7, characterized in that, In steps 3) and 4), the pyrolysis-calcination process parameters are 70~100℃ and 5~30 min; the calcination process parameters are 400~500℃ and 10~30 min.

10. The method for preparing a composite coating of non-noble metal and rare earth metal co-doped modified oxides according to claim 7, characterized in that, The process parameters for the heat treatment in step 5) are: the heat treatment temperature is 400~500℃ and the time is 1~3h.