Composite coating anode and preparation method and application thereof

Abstract

The invention provides a composite coating anode and a preparation method and application thereof.The preparation method of the composite coating anode comprises the steps that S1, a MnO2 thin film layer is prepared on the surface of a Ti substrate, and a middle layer is formed through nitriding treatment; and S2, preparing a MnO2 thin film layer on the surface of the intermediate layer, and performing heat treatment to obtain the composite coating anode. The composite coating anode prepared by the preparation method provided by the invention is long in service life, good in catalytic activity and capable of playing an obvious catalytic role; the MnNx intermediate layer in the composite coating can effectively improve the corrosion resistance of the anode and can perform N doping on the MnO2 layer under subsequent heat treatment at the same time, so that the catalytic activity of the catalyst layer is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrometallurgy, and particularly relates to a composite coating anode and its preparation method and application. Background Art

[0002] The anodes for wet metallurgy electrodes are mainly Pb-based alloy anodes. However, such anodes have poor oxygen evolution catalytic activity, are prone to creep, and have poor corrosion resistance, and cannot meet the requirements of harsh industrial environments. Thanks to the development of the chlor-alkali industry, Ti-based coated anodes have been gradually introduced into the anodes for electrochemical extraction in non-ferrous metal metallurgy. Such anodes have completely changed the selection idea of traditional alloy anodes, not only reducing the preparation cost of the anodes, but also improving the mechanical properties, corrosion resistance of the anodes and the quality of cathode products.

[0003] IrO2 and RuO2 were earliest applied to prepare Ti-based coated anodes due to their strong electrocatalytic activity and electrochemical stability. However, the preparation cost of Ir and Ru-based oxides is too high, which limits their industrial applications. In order to save production costs, non-precious metal oxides, such as Mn, Fe, Pb, and Sn-based oxide coatings, came into being. However, the catalytic performance and electrochemical stability of such non-precious metal oxides are poor. Summary of the Invention

[0004] Aiming at the above technical problems, the purpose of the present invention is to provide a composite coating anode and its preparation method and application.

[0005] To achieve the above purpose, the present invention proposes the following solutions: In the first aspect, a preparation method of a composite coating anode is provided, including: S1. Prepare a MnO2 thin film layer on the surface of a Ti substrate, and perform nitridation treatment to form an intermediate layer; S2. Prepare a MnO2 thin film layer on the surface of the intermediate layer, and perform heat treatment to obtain the composite coating anode.

[0006] Further, in step S1, the temperature of the nitridation treatment is 500-900 °C; the time of the nitridation treatment is 0.5-2 h.

[0007] Further, in step S1, the atmosphere of the nitridation treatment is one or two of N2 and NH3.

[0008] Further, in step S2, the temperature of the heat treatment is 150-200 °C; the time of the heat treatment is 0.5-2 h.

[0009] Further, in steps S1 and S2, the preparation method of the MnO2 thin film layer is any one of electrolysis method, pyrolysis method, hydrothermal method, and chemical precipitation method.

[0010] Further, in step S1, the preparation method of the MnO2 thin film layer includes: preparing a metal Mn layer on a Ti substrate by any one of electrochemical deposition, vapor phase method, and chemical reduction method, and then performing high-temperature oxidation to obtain the MnO2 thin film layer.

[0011] Further, in step S1, the temperature of the high-temperature oxidation is 400-500 °C, and the time of the high-temperature oxidation is 1-2 h.

[0012] Further, in steps S1 and S2, the thickness of the MnO2 thin film layer is 50-100 μm.

[0013] In a second aspect, a composite coating anode is provided, which is prepared by using the aforementioned preparation method.

[0014] In a third aspect, an application of the aforementioned composite coating anode in hydrometallurgy is provided.

[0015] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: In the composite coating anode prepared by the provided preparation method, the composite coating can not only effectively inhibit the passivation of the substrate, significantly extend the service life of the anode, but also play an obvious catalytic role; the MnN x intermediate layer can effectively improve the corrosion resistance of the anode while performing N doping on the MnO2 layer under subsequent heat treatment, further improving the catalytic activity of the catalytic layer.

[0016] The provided preparation method has simple process operation, short process time, uses non-precious metals as raw materials, low cost and wide material sources, and is easy to be widely applied industrially. Detailed implementation manners

[0017] In view of the technical problems that the catalytic performance and electrochemical stability of the coating anode obtained by forming an MnO2 coating on the Ti substrate surface are poor, the applicant has found through research that by first preparing non-precious metal oxide MnO2 on the Ti substrate surface, reducing MnO2 by high-temperature nitriding to generate an MnN x non-oxide intermediate layer, then preparing an MnO2 catalytic layer on the surface of the intermediate layer, and performing heat treatment at a certain temperature to make N element diffuse into the catalytic layer to form an N-modified MnO2 catalytic layer, the corrosion resistance and catalytic performance of the prepared composite coating anode are significantly improved, and the improvement of catalytic activity can reduce production energy consumption.

[0018] The present invention provides a preparation method of a composite coating anode, including: S1. Prepare an MnO2 thin film layer on the surface of a Ti substrate, and perform nitriding treatment to form an intermediate layer; S2. Prepare an MnO₂ thin film layer on the surface of the intermediate layer and obtain the composite coating anode after heat treatment.

[0019] The above preparation process is simple and has a short preparation time, which can significantly improve the corrosion resistance and catalytic performance of the anode, and the prepared coating anode can reduce the production cost of industrial electrowinning.

[0020] In some preferred embodiments, in step S1, the temperature of the nitriding treatment is 500 - 900 °C, such as 500 °C, 550 °C, 600 °C, 650 °C, 700 °C, 750 °C, 800 °C, 850 °C, 900 °C, etc.; the time of the nitriding treatment is 0.5 - 2 h, such as 0.5 h, 0.8 h, 1 h, 1.2 h, 1.5 h, 1.8 h, 2 h, etc.

[0021] In some preferred embodiments, in step S1, the atmosphere of the nitriding treatment is one or two of N₂ and NH₃. The flow rate of the nitriding treatment can be routinely determined according to the actual process requirements.

[0022] In some preferred embodiments, in step S2, the temperature of the heat treatment is 150 - 200 °C, such as 150 °C, 160 °C, 170 °C, 180 °C, 190 °C, 200 °C, etc.; the time of the heat treatment is 0.5 - 2 h, such as 0.5 h, 0.8 h, 1 h, 1.2 h, 1.5 h, 1.8 h, 2 h, etc.

[0023] In steps S1 and S2, the preparation method of the MnO₂ thin film layer can directly prepare the MnO₂ thin film layer by using the conventional preparation methods in the art. For example, the preparation method of the MnO₂ thin film layer can be any one of electrolysis method, pyrolysis method, hydrothermal method, and chemical precipitation method, and the process parameters can be routinely determined.

[0024] The MnO₂ thin film layer can also be obtained by first preparing an Mn layer and then performing an oxidation treatment. In some preferred embodiments, in step S1, the preparation method of the MnO₂ thin film layer includes: preparing a metal Mn layer on a Ti substrate by any one of electrochemical deposition method, vapor phase method, and chemical reduction method, and then performing high-temperature oxidation to obtain the MnO₂ thin film layer.

[0025] In some preferred embodiments, in step S1, the temperature of the high-temperature oxidation is 400 - 500 °C, such as 400 °C, 420 °C, 450 °C, 480 °C, 500 °C, etc.; in step S1, the time of the high-temperature oxidation is 1 - 2 h, such as 1 h, 1.2 h, 1.5 h, 1.8 h, 2 h, etc.

[0026] In steps S1 and S2, the thickness of the MnO2 thin film layer can be determined according to actual requirements. During the preparation process of the MnO2 thin film layer, the coating thickness can be controlled by conventional process parameter regulation. After research, the applicant has determined a preferred thickness of the MnO2 thin film layer. In some preferred embodiments, in steps S1 and S2, the thickness of the MnO2 thin film layer is 50 - 100 μm, such as 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, etc.

[0027] In some embodiments, a composite coating anode is provided, which is prepared by the aforementioned preparation method.

[0028] In some embodiments, the application of the aforementioned composite coating anode in hydrometallurgy is provided.

[0029] To facilitate the understanding of the present invention, the present invention will be described more comprehensively and in detail below in conjunction with preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0030] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0031] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through the market or can be prepared by existing methods.

[0032] Example 1 First, a MnO2 thin film was prepared on the surface of a Ti substrate by electrolysis. The specific process parameters were: the concentration of Mn 2+ was 45 g / L, the concentration of H2SO4 was 40 g / L, the electrolysis temperature was 95 °C, the electrolysis time was 2 h, and the applied potential was 40 A / m 2 . The prepared Ti / MnO2 thin film material was placed in a tubular furnace, NH3 was introduced, the gas flow rate was 0.5 L / min, the heat treatment temperature was 800 °C, and the heat treatment time was 2 h. Then, a layer of MnO2 was prepared on the surface of the intermediate layer by electrolysis (the preparation steps and process parameters were: electrolyte composition: Mn 2+ concentration: 45 g / L, H2SO4 concentration: 40 g / L, anodic current density: 40 A / m 2 , electrolysis temperature: 95 °C, electrolysis time: 2 h), and then heat-treated at 180 °C for 2 h.

[0033] The lifetime of the prepared coating anode was tested through an accelerated life test. The test conditions were: the anodic current density was controlled at 1 A / cm2 , the electrolyte is 160g / L H2SO4 solution, the counter electrode is 2*2cm 2 The platinum electrode and the reference electrode are saturated calomel electrodes. When the electrode voltage exceeds 10V, the electrode is considered to be in failure. The failure life of the coated anode is measured to be 260280s. According to the accelerated life formula t 2=( J 2 / J 1) n t 1 (where t1 is the accelerated life, t2 is the actual life, J2 is the accelerated current density, J1 is the actual current density, and n is a constant equal to 2) to obtain the electrode at 50 mA / cm 2 The lifespan is 1205 days (reflecting corrosion resistance). The current density is 50mA / cm 2 When the anode potential is 1.727V vs. SCE (Showing Catalytic Effect).

[0034] Example 2 First, MnO2 thin film was prepared on the surface of Ti substrate by electrolysis. The specific process parameters were Mn 2+ The concentration is 45g / L, the H2SO4 concentration is 40g / L, the electrolysis temperature is 95℃, the electrolysis time is 2h, and the applied potential is 40A / m 2 The prepared Ti / MnO2 thin film material was placed in a tube furnace, N2 was introduced, the gas flow rate was 1.0L / min, the heat treatment temperature was 800℃, and the heat treatment time was 2h. Then a layer of MnO2 was prepared on the surface of the intermediate layer by electrolysis (the preparation steps and process parameters were: electrolyte composition: Mn 2+ Concentration: 45 g / L, H2SO4 concentration: 40 g / L, anode current density: 40 A / m 2 , electrolysis temperature: 95°C, electrolysis time: 2h), and then heat treated at 180°C for 2h.

[0035] The test conditions were the same as those in Example 1. The accelerated life of the anode was measured to be 281655s. 2 The lifespan is 1303 days. The current density is 50 mA / cm 2 When the anode potential is 1.726V vs. SCE.

[0036] Example 3 First, a metal Mn layer was prepared on the surface of the Ti substrate by electrochemical deposition. The specific process parameters were Mn 2+The concentration is 20 g / L, the concentration of (NH4)2SO4 is 100 g / L, the concentration of SeO2 is 0.03 g / L, the electrolysis temperature is 42 °C, the electrolysis time is 25 min, and the applied potential is 420 A / m 2 Put the prepared Ti / Mn thin film material into a tube furnace. Under an air atmosphere, the heat treatment temperature is 500 °C and the heat treatment time is 2 h. After preparation, NH3 is introduced, the gas flow rate is 1.5 L / min, the heat treatment temperature is 900 °C, and the heat treatment time is 1 h. Then, a layer of MnO2 is prepared on the surface of the intermediate layer by electrolysis (the preparation steps and process parameters are: electrolyte composition: Mn 2+ concentration: 45 g / L, H2SO4 concentration: 40 g / L, anodic current density: 40 A / m 2 , electrolysis temperature: 95 °C, electrolysis time: 2 h), and then heat treatment is carried out at 180 °C for 2 h.

[0037] The test conditions are the same as those in Example 1. The measured accelerated life of the anode is 298320 s, and the life of the anode at 50 mA / cm 2 is 1381 days. When the current density is 50 mA / cm 2 , the anodic potential is 1.728 V vs. SCE.

[0038] Example 4 First, a metal Mn layer is prepared on the surface of a Ti substrate by electrochemical deposition. The specific process parameters are Mn 2+ concentration is 20 g / L, the concentration of (NH4)2SO4 is 100 g / L, the concentration of SeO2 is 0.03 g / L, the electrolysis temperature is 42 °C, the electrolysis time is 25 min, and the applied potential is 420 A / m 2 Put the prepared Ti / Mn thin film material into a tube furnace. Under an air atmosphere, the heat treatment temperature is 450 °C and the heat treatment time is 2 h. After preparation, a mixture of N2 and NH3 is introduced, the gas flow rate is 1.5 L / min, the heat treatment temperature is 800 °C, and the heat treatment time is 2 h. Then, a layer of MnO2 is prepared on the surface of the intermediate layer by electrolysis (the preparation steps and process parameters are: electrolyte composition: Mn 2+ concentration: 45 g / L, H2SO4 concentration: 40 g / L, anodic current density: 40 A / m 2 , electrolysis temperature: 95 °C, electrolysis time: 2 h), and then heat treatment is carried out at 150 °C for 2 h.

[0039] The test conditions are the same as those in Example 1. The measured accelerated life of the anode is 287553 s, and the life of the anode at 50 mA / cm 2 is 1331 days. When the current density is 50 mA / cm 2When the anode potential is 1.766 V vs. SCE.

[0040] Example 5 First, a metal Mn layer was prepared on the surface of a Ti substrate by electrochemically depositing method. The specific process parameters were as follows: the concentration of Mn 2+ was 20 g / L, the concentration of (NH4)2SO4 was 100 g / L, the concentration of SeO2 was 0.03 g / L, the electrolysis temperature was 42 °C, the electrolysis time was 25 min, and the applied potential was 420 A / m 2 . The prepared Ti / Mn thin film material was placed in a tube furnace. Under an air atmosphere, the heat treatment temperature was 450 °C and the heat treatment time was 2 h. After preparation, a mixed gas of N2 and NH3 was introduced, the gas flow rate was 1.5 L / min, the heat treatment temperature was 500 °C, and the heat treatment time was 2 h. Then, a layer of MnO2 was prepared on the surface of the intermediate layer by electrolysis method (the preparation steps and process parameters were: the composition of the electrolyte: Mn 2+ concentration: 45 g / L, the concentration of H2SO4: 40 g / L, the anode current density: 40 A / m 2 , the electrolysis temperature: 95 °C, the electrolysis time: 2 h), and then heat treatment was carried out at 150 °C for 2 h.

[0041] The test conditions were the same as those in Example 1. The measured accelerated life of the anode was 281985 s, and the life of the anode at 50 mA / cm 2 was 1305 days. When the current density was 50 mA / cm 2 , the anode potential was 1.767 V vs. SCE.

[0042] Example 6 First, a metal Mn layer was prepared on the surface of a Ti substrate by electrochemically depositing method. The specific process parameters were as follows: the concentration of Mn 2+ was 20 g / L, the concentration of (NH4)2SO4 was 100 g / L, the concentration of SeO2 was 0.03 g / L, the electrolysis temperature was 42 °C, the electrolysis time was 25 min, and the applied potential was 420 A / m 2 . The prepared Ti / Mn thin film material was placed in a tube furnace. Under an air atmosphere, the heat treatment temperature was 450 °C and the heat treatment time was 2 h. After preparation, a mixed gas of N2 and NH3 was introduced, the gas flow rate was 1.5 L / min, the heat treatment temperature was 800 °C, and the heat treatment time was 2 h. Then, a layer of MnO2 was prepared on the surface of the intermediate layer by electrolysis method (the preparation steps and process parameters were: the composition of the electrolyte: Mn 2+ concentration: 45 g / L, the concentration of H2SO4: 40 g / L, the anode current density: 40 A / m 2 , the electrolysis temperature: 95 °C, the electrolysis time: 2 h), and then heat treatment was carried out at 200 °C for 2 h.

[0043] The test conditions were the same as those in Example 1. The measured accelerated life of the anode was 287750 s, and the life of the anode at 50 mA / cm 2 was 1332 days. When the current density was 50 mA / cm 2 , the anode potential was 1.729 V vs. SCE.

[0044] Comparative Example 1 First, an MnO2 film was prepared on the surface of a Ti substrate by electrolysis. The specific process parameters were as follows: the Mn 2+ concentration was 45 g / L, the H2SO4 concentration was 40 g / L, the electrolysis temperature was 95 °C, the electrolysis time was 2 h, and the applied potential was 40 A / m 2 .

[0045] The life of the prepared coated anode was tested by an accelerated life test. The test conditions were as follows: the anode current density was controlled at 1 A / cm 2 , the electrolyte was 160 g / L H2SO4, the counter electrode was a 2×2 cm 2 platinum electrode, and the reference electrode was a saturated calomel electrode. The electrode was considered to have failed when the electrode voltage exceeded 10 V. The measured failure life of the coated anode was 118745 s. According to the accelerated life formula t t2 = ( J t2 / t J 1) n t 1 (where t1 is the accelerated life, t2 is the actual life, J2 is the accelerated current density, J1 is the actual current density, and n is a constant equal to 2), the life of the electrode at 50 mA / cm 2 was 549 days. When the current density was 50 mA / cm 2 , the anode potential was 1.895 V vs. SCE.

[0046] Comparative Example 2 The difference between this comparative example and Example 1 was only that a manganese nitride layer was formed only on the anode surface. Specifically: First, an MnO2 film was prepared on the surface of a Ti substrate by electrolysis. The specific process parameters were as follows: the Mn 2+ concentration was 45 g / L, the H2SO4 concentration was 40 g / L, the electrolysis temperature was 95 °C, the electrolysis time was 2 h, and the applied potential was 40 A / m 2 . The prepared Ti / MnO2 film material was placed in a tube furnace, and NH3 was introduced. The gas flow rate was 0.5 L / min, the heat treatment temperature was 800 °C, and the heat treatment time was 2 h.

[0047] The lifespan of the prepared coated anode was tested through an accelerated life test. The test conditions were as follows: the anode current density was controlled at 1 A / cm 2 , the electrolyte was 160 g / L H2SO4, the counter electrode was a 2*2 cm 2 platinum electrode, the reference electrode was a saturated calomel electrode, and the electrode was considered to have failed when the electrode voltage exceeded 10 V. The failure lifespan of the coated anode was measured to be 129865 s. According to the accelerated life formula t2=(J2 / J1)nt1 (where t1 is the accelerated lifespan, t2 is the actual lifespan, J2 is the accelerated current density, J1 is the actual current density, and n is a constant equal to 2), the lifespan of the electrode at 50 mA / cm 2 was obtained as 601 days. When the current density was 50 mA / cm 2 , the anode potential was 2.132 V vs. SCE.

[0048] Comparative Example 3 The difference between this comparative example and Example 1 was only that the heat treatment step was omitted. Specifically: First, an MnO2 thin film was prepared on the surface of a Ti substrate by electrolysis. The specific process parameters were that the Mn 2+ concentration was 45 g / L, the H2SO4 concentration was 40 g / L, the electrolysis temperature was 95 °C, the electrolysis time was 2 h, and the applied potential was 40 A / m 2 . The prepared Ti / MnO2 thin film material was placed in a tubular furnace, NH3 was introduced, the gas flow rate was 0.5 L / min, the heat treatment temperature was 800 °C, and the heat treatment time was 2 h. Then, a layer of MnO2 was prepared on the surface of the intermediate layer by electrolysis (the preparation steps and process parameters were: electrolyte composition: Mn 2+ concentration: 45 g / L, H2SO4 concentration: 40 g / L, anode current density: 40 A / m 2 , electrolysis temperature: 95 °C, electrolysis time: 2 h).

[0049] The lifespan of the prepared coated anode was tested through an accelerated life test. The test conditions were as follows: the anode current density was controlled at 1 A / cm 2 , the electrolyte was 160 g / L H2SO4, the counter electrode was a 2*2 cm 2 platinum electrode, the reference electrode was a saturated calomel electrode, and the electrode was considered to have failed when the electrode voltage exceeded 10 V. The failure lifespan of the coated anode was measured to be 220879 s. According to the accelerated life formula t2=(J2 / J1)nt1 (where t1 is the accelerated lifespan, t2 is the actual lifespan, J2 is the accelerated current density, J1 is the actual current density, and n is a constant equal to 2), the lifespan of the electrode at 50 mA / cm 2 was obtained as 1022 days. When the current density was 50 mA / cm 2At that time, the anode potential was 1.898 V vs. SCE.

[0050] Comparing the performances of the composite coating anodes prepared in the above examples and comparative examples, it is found that the anodes of the composite coating anodes prepared in each example have a low anode and a long service life. Compared with the composite coating anodes of Comparative Examples 1 to 3, the anode potential of the composite coating anode prepared in Example 1 is significantly reduced, indicating that the oxygen evolution catalytic activity of the anode is improved, and the service life is significantly increased. After analysis, this may be because the composite coating can effectively inhibit the passivation of the substrate. The MnN x The intermediate layer can effectively improve the corrosion resistance of the anode while performing N doping on the MnO2 layer under subsequent heat treatment, further improving the catalytic activity of the catalytic layer.

[0051] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. Preparation method of composite coating anode, characterized in that, Including: S1. Prepare a MnO2 thin film layer on the surface of a Ti substrate, and after nitridation treatment, form an intermediate layer; S2. Prepare a MnO2 thin film layer on the surface of the intermediate layer, and after heat treatment, obtain a composite coating anode.

2. The preparation method of the composite coating anode according to claim 1, characterized in that, In step S1, the temperature of the nitridation treatment is 500-900 °C; the time of the nitridation treatment is 0.5-2 h.

3. The preparation method of the composite coating anode according to claim 1 or 2, characterized in that, In step S1, the atmosphere of the nitridation treatment is one or both of N2 and NH3.

4. The preparation method of the composite coating anode according to claim 1, characterized in that, In step S2, the temperature of the heat treatment is 150-200 °C; the time of the heat treatment is 0.5-2 h.

5. The preparation method of the composite coating anode according to claim 1, characterized in that, In steps S1 and S2, the preparation method of the MnO2 thin film layer is any one of electrolysis method, pyrolysis method, hydrothermal method, and chemical precipitation method.

6. The preparation method of the composite coating anode according to claim 1, characterized in that, In step S1, the preparation method of the MnO2 thin film layer includes: preparing a metal Mn layer on the Ti substrate by any one of electrochemical deposition method, gas phase method, and chemical reduction method, and then performing high-temperature oxidation to obtain a MnO2 thin film layer.

7. The preparation method of the composite coating anode according to claim 6, characterized in that, In step S1, the temperature of the high-temperature oxidation is 400-500 °C, and the time of the high-temperature oxidation is 1-2 h.

8. The preparation method of the composite coating anode according to claim 1, characterized in that, In steps S1 and S2, the thickness of the MnO2 thin film layer is 50-100 μm.

9. Composite coating anode, characterized in that, Prepared by using the preparation method according to any one of claims 1-8.

10. Application of the composite coating anode according to claim 9 in hydrometallurgy.