Anode material and preparation method thereof

Abstract

The present invention provides an anode material and a preparation method thereof, belonging to the technical field of electrolytic cell electrodes. The anode material includes a titanium substrate and a lead dioxide surface layer, and further includes an intermediate layer between the titanium substrate and the lead dioxide surface layer, wherein the intermediate layer adopts modified carbon-doped titanium dioxide, and the preparation method is as follows: A1, mixing butyl titanate with anhydrous ethanol, adding dropwise to deionized water under stirring, filtering a white precipitate, and drying to obtain titanium dioxide; A2, mixing the titanium dioxide obtained in A1 with glucose, and roasting in an inert atmosphere at 300-320°C for 2.5-3.5h to obtain carbon-doped titanium dioxide; A3, soaking the carbon-doped titanium dioxide in a sulfuric acid solution for 8-10min, taking it out, rinsing it with deionized water until the rinsing liquid is neutral, and drying to obtain modified carbon-doped titanium dioxide. The present invention can effectively inhibit surface peeling and improve the service life of the obtained anode material.

Description

Technical Field

[0001] The invention belongs to the technical field of electrolytic cell electrodes, and particularly relates to an anode material and a preparation method thereof. Background Art

[0002] In the electrolytic preparation of sodium perchlorate, an external circulation electrolytic cell is used, with titanium-based lead dioxide as the anode and lead or stainless steel as the cathode. The electrolyte is sodium chlorate solution with a concentration controlled at 300-400g / L. In terms of electrolytic reaction conditions, the current density is 1500-2500A / m 2 , the temperature is 40-50°C (maintained by cooling in an external circulation tank). First, sodium chloride solution is electrolyzed to produce sodium chlorate, with the reaction formula: NaCl + 3H2O → NaClO3 + 3H2↑; then, sodium chlorate solution is further electrolyzed to produce sodium perchlorate, with the reaction formula: NaClO3 + H2O → NaClO4 + H2↑.

[0003] Traditional sodium perchlorate anode materials are titanium-based lead dioxide-plated. After long-term use, such anodes will cause the lead dioxide to fall off due to high current, oxidation, and other factors. The lead dioxide (PbO2) coating is the main active interface for electrochemical oxidation reactions. Its shedding leads to a reduction in the effective reaction area, an increase in local current density, an increase in the anode potential, and the oxygen evolution side reaction (2H2O−4 e - →O2↑+4H + ) ratio increases, and the main reaction (such as ClO3 - →ClO4 - ) competition, reducing current efficiency. Bubbles generated by the oxygen evolution reaction are retained at the coating peeling interface, hindering mass transfer and increasing local resistance and anode potential, forming a positive feedback loop: coating peeling → increased potential → increased oxygen evolution → bubble accumulation → accelerated coating peeling, leading to increased coating peeling and shortening the service life of the anode material. Summary of the Invention

[0004] In order to solve the problems existing in the background technology, the present invention provides an anode material and a preparation method thereof, which effectively inhibits surface peeling and improves the service life of the prepared anode material.

[0005] To achieve the above objectives, in a first aspect, the present invention provides an anode material comprising a titanium substrate and a lead dioxide surface layer, and further comprising an intermediate layer located between the titanium substrate and the lead dioxide surface layer, wherein the intermediate layer is made of modified carbon-doped titanium dioxide, and the preparation method thereof is as follows:

[0006] A1. Mix butyl titanate with anhydrous ethanol, add dropwise to deionized water under stirring, filter the white precipitate, and dry to obtain titanium dioxide;

[0007] A2. Mix the titanium dioxide obtained in A1 with glucose and calcine at 300-320°C in an inert atmosphere for 2.5-3.5 hours to obtain carbon-doped titanium dioxide;

[0008] A3. Soak the carbon-doped titanium dioxide in a sulfuric acid solution for 8-10 minutes, take it out, rinse it with deionized water until the rinse solution is neutral, and dry it to obtain modified carbon-doped titanium dioxide.

[0009] Furthermore, in A1, the mass ratio of the butyl titanate to anhydrous ethanol is 1:(6-8).

[0010] Furthermore, in A1, the dropping speed is 0.1-0.2 mL / s, and the mass ratio of deionized water to butyl titanate is (30-35):1.

[0011] Furthermore, in A2, the mass ratio of titanium dioxide to glucose is (8-10):1.

[0012] Furthermore, the thickness of the intermediate layer is 0.5-0.8 μm.

[0013] Furthermore, the lead dioxide surface layer has a thickness of 120-150 μm.

[0014] In a second aspect, the present invention provides a method for preparing the above-mentioned anode material, comprising the following steps:

[0015] S1, sandblasting the titanium substrate to remove surface burrs and oil stains, and then ultrasonically cleaning it with deionized water to obtain a pretreated substrate;

[0016] S2. Modifying carbon-doped titanium dioxide on the pretreated substrate by medium-frequency magnetron sputtering to form an intermediate layer to obtain a first material;

[0017] S3. Depositing lead dioxide on the intermediate layer by electroplating precipitation to form a lead dioxide surface layer, thereby obtaining the anode material.

[0018] Furthermore, the specific operation of S3 is as follows: the first material is used as the anode and the pure titanium plate is used as the cathode, which are fixed in the electrolytic cell respectively, and then the electrolyte is added, the electrolyte is heated in a water bath to a temperature of 60-80°C, and the electrodeposition is carried out for 2.5-3 hours. After deposition, it is rinsed with deionized water to neutrality and dried at 70-80°C for 2-2.5 hours to obtain the anode material.

[0019] Furthermore, the electrolyte comprises lead nitrate, sodium fluoride and copper ions, the concentration of the lead nitrate is 270-300 g / L, the concentration of the sodium fluoride is 8-9 g / L, and the concentration of the copper ions is 0.3-0.5 g / L.

[0020] Furthermore, the pH value of the electrolyte is 1.5-2.5.

[0021] This application has the following beneficial effects:

[0022] The present invention adds a modified carbon-doped titanium dioxide intermediate layer between the titanium substrate and the lead dioxide surface layer. During the carbonization process, the amorphous carbon or graphitized carbon generated by the carbonization of glucose can form an interpenetrating network with the titanium dioxide. This disperses the stress field, inhibiting crack propagation and reducing the risk of peeling or shedding of the lead dioxide surface layer.

[0023] The sulfuric acid activation process can expose the Ti by etching the carbon-rich area on the surface of carbon-doped titanium dioxide. 4+ Active sites, which form Pb-O-Ti bonds during the electrodeposition of lead dioxide, form strong chemical bonds, enhance interfacial bonding strength, and effectively inhibit the peeling / shedding of the lead dioxide surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 , a comparative trend chart of the test data of the enhanced life (days) of the anode materials obtained in Examples 1 to 3 of the present invention and Comparative Examples 1 to 3. DETAILED DESCRIPTION

[0025] The present application is further described in detail below with reference to the embodiments.

[0026] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0027] Example 1: (1) The preparation method of modified carbon-doped titanium dioxide is as follows:

[0028] A1. Mix butyl titanate and anhydrous ethanol in a mass ratio of 1:7 and add dropwise to deionized water under stirring at 280 r / min. The addition rate should be 0.15 mL / s. Do not add too fast to avoid local oversaturation and particle agglomeration. The mass ratio of deionized water to butyl titanate is 32:1. Filter the white precipitate and dry it in a vacuum at 80°C for 7 h to obtain titanium dioxide.

[0029] A2. Titanium dioxide and glucose were ball-milled in a mass ratio of 9:1 for 30 minutes to improve dispersion uniformity. The mixture was heated at a rate of 5°C / min to avoid structural defects caused by local thermal stress. The mixture was heated to 310°C and calcined in an inert atmosphere (nitrogen flow rate of 50 mL / min to ensure an oxygen-deficient environment) for 3 hours to obtain carbon-doped titanium dioxide.

[0030] A3. Soak the carbon-doped titanium dioxide in a 2 mol / L sulfuric acid solution at room temperature for 9 minutes, then take it out and rinse it with deionized water until the rinse solution is neutral (pH = 7.0 ± 0.2). Dry it in a vacuum at 60°C for 4 hours to avoid high temperature damage to the carbon-doped structure, thereby obtaining modified carbon-doped titanium dioxide.

[0031] (2) A method for preparing an anode material, comprising the following steps:

[0032] S1. The titanium substrate was sandblasted (sand particle size 80-120 mesh, compressed air pressure of about 0.6 MPa, sandblasting time 3 min), surface burrs and oil stains were removed (ultrasonic cleaning in 10% NaOH alkaline solution at 40°C for 15 min), and then ultrasonically cleaned with deionized water to obtain a pretreated substrate.

[0033] S2. Carbon-doped titanium dioxide is modified on the pretreated substrate by medium-frequency magnetron sputtering, with a sputtering power of about 180 W, a working gas pressure of about 0.4 Pa, and a substrate temperature of about 240° C. to form an intermediate layer with a thickness of 0.63 μm, thereby obtaining the first material.

[0034] S3. Use electroplating sedimentation method to deposit lead dioxide on the intermediate layer to form a lead dioxide surface layer, thus obtaining the anode material. Specifically, the first material is used as the anode, and the pure titanium plate is used as the cathode, which are fixed in the electrolytic cell respectively, and then the electrolyte is added. The electrolyte includes lead nitrate, sodium fluoride and copper ions. The concentration of lead nitrate is 280g / L, the concentration of sodium fluoride is 8.7g / L, the concentration of copper ions is 0.4g / L, and the pH value of the electrolyte is 2.1. Heat the electrolyte in a water bath to a temperature of 70°C, and turn on the power (the current density is controlled at 25mA / cm 2 ) was deposited for 2.7 hours, and after deposition, it was rinsed with deionized water until neutral, and dried at 75°C for 2.3 hours to form a lead dioxide surface layer with a thickness of 137 μm, thereby obtaining the anode material.

[0035] Example 2: The difference between this example and Example 1 is that: (1) the preparation method of modified carbon-doped titanium dioxide is as follows:

[0036] A1. Mix butyl titanate and anhydrous ethanol in a mass ratio of 1:6, add dropwise to deionized water with stirring at a rate of 0.1 mL / s. The mass ratio of deionized water to butyl titanate is 30:1. Filter the white precipitate and dry it to obtain titanium dioxide.

[0037] A2. Titanium dioxide and glucose were mixed in a mass ratio of 8:1, and calcined at 300°C in an inert atmosphere for 3.5 hours to obtain carbon-doped titanium dioxide.

[0038] A3. Soak the carbon-doped titanium dioxide in a sulfuric acid solution for 8 minutes, take it out, rinse it with deionized water until the rinse solution is neutral, and dry it to obtain the modified carbon-doped titanium dioxide.

[0039] (2) A method for preparing an anode material, comprising the following steps:

[0040] S1. Sandblast the titanium substrate to remove surface burrs and oil stains, and then ultrasonically clean it with deionized water to obtain a pretreated substrate.

[0041] S2. Modify carbon-doped titanium dioxide on the pretreated substrate by medium-frequency magnetron sputtering to form an intermediate layer with a thickness of 0.71 μm, thereby obtaining a first material.

[0042] S3. Use electroplating sedimentation to deposit lead dioxide on the intermediate layer to form a lead dioxide surface layer, thereby obtaining the anode material. Specifically, the first material is used as the anode, and the pure titanium plate is used as the cathode, which are fixed in the electrolytic cell respectively, and then the electrolyte is added. The electrolyte includes lead nitrate, sodium fluoride and copper ions. The concentration of lead nitrate is 280g / L, the concentration of sodium fluoride is 8.7g / L, the concentration of copper ions is 0.4g / L, and the pH value of the electrolyte is 2.1. The temperature of the electrolyte is heated to 60°C in a water bath, and the electroplating is carried out for 3 hours. After deposition, it is rinsed with deionized water to neutrality and dried at 70°C for 2.5 hours to form a lead dioxide surface layer. The thickness of the lead dioxide surface layer is 133μm, thereby obtaining the anode material.

[0043] Example 3: The difference between this example and Example 1 is that: (1) the preparation method of modified carbon-doped titanium dioxide is as follows:

[0044] A1. Mix butyl titanate and anhydrous ethanol in a mass ratio of 1:8, add dropwise to deionized water with stirring at a rate of 0.2 mL / s. The mass ratio of deionized water to butyl titanate is 35:1. Filter the white precipitate and dry it to obtain titanium dioxide.

[0045] A2. Titanium dioxide and glucose were mixed in a mass ratio of 10:1, and calcined at 320°C in an inert atmosphere for 2.5 hours to obtain carbon-doped titanium dioxide.

[0046] A3. Soak the carbon-doped titanium dioxide in a sulfuric acid solution for 10 minutes, take it out, rinse it with deionized water until the rinse solution is neutral, and dry it to obtain the modified carbon-doped titanium dioxide.

[0047] (2) A method for preparing an anode material, comprising the following steps:

[0048] S1. Sandblast the titanium substrate to remove surface burrs and oil stains, and then ultrasonically clean it with deionized water to obtain a pretreated substrate.

[0049] S2. Modify carbon-doped titanium dioxide on the pretreated substrate by medium-frequency magnetron sputtering to form an intermediate layer with a thickness of 0.73 μm, thereby obtaining a first material.

[0050] S3. Use electroplating sedimentation to deposit lead dioxide on the intermediate layer to form a lead dioxide surface layer, thereby obtaining the anode material. Specifically, the first material is used as the anode, and the pure titanium plate is used as the cathode, which are fixed in the electrolytic cell respectively, and then the electrolyte is added. The electrolyte includes lead nitrate, sodium fluoride and copper ions. The concentration of lead nitrate is 280g / L, the concentration of sodium fluoride is 8.7g / L, the concentration of copper ions is 0.4g / L, and the pH value of the electrolyte is 2.1. The temperature of the electrolyte is heated to 80°C in a water bath, and the electroplating is carried out for 3 hours. After deposition, it is rinsed with deionized water to neutrality and dried at 80°C for 2 hours to form a lead dioxide surface layer. The thickness of the lead dioxide surface layer is 131μm, thereby obtaining the anode material.

[0051] Comparative Example 1: The only difference between this comparative example and Example 1 is that the middle layer is deleted.

[0052] Specifically, the method for preparing the anode material comprises the following steps:

[0053] S1. Sandblast the titanium substrate to remove surface burrs and oil stains, and then ultrasonically clean it with deionized water to obtain a pretreated substrate.

[0054] S2. Using an electroplating sedimentation method to deposit lead dioxide on the pretreated substrate to form a lead dioxide surface layer, thereby obtaining an anode material.

[0055] Comparative Example 2: The only difference between this comparative example and Example 1 is that in the preparation of the intermediate layer, the modified carbon-doped titanium dioxide is replaced by titanium dioxide.

[0056] Specifically, the preparation method of titanium dioxide is as follows: take butyl titanate and anhydrous ethanol in a mass ratio of 1:7, mix, and add dropwise into deionized water under stirring at a dropping speed of 1.5 mL / s. The mass ratio of deionized water to butyl titanate is 32:1. Filter the white precipitate and dry it to obtain titanium dioxide.

[0057] Comparative Example 3: The difference between this comparative example and Example 1 is that in the preparation of the intermediate layer, the modified carbon-doped titanium dioxide is replaced by carbon-doped titanium dioxide.

[0058] Specifically, the preparation method of carbon-doped titanium dioxide is as follows:

[0059] A1. Mix butyl titanate and anhydrous ethanol in a mass ratio of 1:7, add dropwise to deionized water with stirring at a rate of 1.5 mL / s. The mass ratio of deionized water to butyl titanate is 32:1. Filter the white precipitate and dry it to obtain titanium dioxide.

[0060] A2. Titanium dioxide and glucose were mixed in a mass ratio of 9:1, and calcined at 310°C in an inert atmosphere for 3 h to obtain carbon-doped titanium dioxide.

[0061] Test Example: Test subjects: Anode materials prepared from Examples 1-3 and Comparative Examples 1-3. Test item: Accelerated life test (ASTM verification method). Intensified test conditions: Current density: 30,000 A / m 2 Temperature: 55 ± 1°C. Electrolyte acidity: H₂SO₄ added to a pH of 0.5 (to accelerate interfacial corrosion and shedding). The test cycle consisted of a 30-minute power outage every 8 hours (to simulate start-stop shock). The anode surface was cleaned with 3% HNO₃ every 24 hours (to remove the passivation film). Test results: See Table 1.

[0062] Table 1. Test data of experimental example

[0063]

[0064] Result analysis: Analyze Example 1-Example 3 and combine the data in Table 1 and Figure 1 It can be seen that the anode material prepared in the present invention (Example 1 to Example 3) has an enhanced lifespan of more than 54 days.

[0065] Analyze Example 1 and Comparative Examples 1-3 and combine the data in Table 1 and Figure 1 Comparing Comparative Examples 1 and 2, it can be seen that adding a titanium dioxide interlayer between the titanium substrate and the lead dioxide surface layer results in a decrease in the enhanced lifespan of the resulting anode material. This is because the thermal expansion coefficients of the lead dioxide surface layer and the titanium dioxide interlayer differ significantly, resulting in insufficient bonding between the two. This prevents the effective dissipation of Joule heating-induced interfacial stresses. The mechanical stress combined with the impact of oxygen-evolving bubbles (cavitation) accelerates the peeling / detachment of the lead dioxide surface layer from the titanium dioxide interlayer, shortening the enhanced lifespan of the anode material.

[0066] Comparing Comparative Examples 2 and 3, it can be seen that replacing the titanium dioxide intermediate layer between the titanium substrate and the lead dioxide surface layer with a carbon-doped titanium dioxide intermediate layer can improve the strengthening life of the resulting anode material. However, it is still slightly lower than the strengthening life of the anode material without an intermediate layer in Comparative Example 1. This is because, during the carbon doping process, the amorphous carbon or graphitized carbon generated after the carbonization of glucose can form an interpenetrating network structure with titanium dioxide, inhibiting crack propagation by dispersing the stress field and reducing the risk of peeling / shedding of the lead dioxide surface layer. However, carbon doping cannot completely offset the negative effects of adding a titanium dioxide intermediate layer.

[0067] By comparison with Example 1, it can be seen that replacing the carbon-doped titanium dioxide intermediate layer between the titanium substrate and the lead dioxide surface layer with a modified carbon-doped titanium dioxide intermediate layer can further improve the reinforcement life of the anode material. This is because the sulfuric acid activation process can expose the carbon-rich area on the surface of the carbon-doped titanium dioxide by etching. 4+Active sites, which form Pb-O-Ti bonds during the electrodeposition of lead dioxide, form strong chemical bonds, enhance interfacial bonding strength, and effectively inhibit the peeling / shedding of the lead dioxide surface.

[0068] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0069] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. An anode material comprising a titanium substrate and a lead dioxide surface layer, characterized in that: It also includes an intermediate layer located between the titanium substrate and the lead dioxide surface layer, the thickness of the intermediate layer is 0.5-0.8 μm, and the intermediate layer is made of modified carbon-doped titanium dioxide, and the preparation method thereof is as follows: A1. Mix butyl titanate and anhydrous ethanol in a mass ratio of 1:(6-8) and add dropwise to deionized water with stirring at a rate of 0.1-0.2 mL / s. The mass ratio of deionized water to butyl titanate is (30-35):

1. Filter the white precipitate and dry it to obtain titanium dioxide. A2. Mix the titanium dioxide obtained in A1 with glucose in a mass ratio of (8-10):1, and calcine at 300-320°C in an inert atmosphere for 2.5-3.5 hours to obtain carbon-doped titanium dioxide; A3. Soak the carbon-doped titanium dioxide in a sulfuric acid solution for 8-10 minutes, take it out, rinse it with deionized water until the rinse solution is neutral, and dry it to obtain modified carbon-doped titanium dioxide; The method for preparing the anode material comprises the following steps: S1, sandblasting the titanium substrate to remove surface burrs and oil stains, and then ultrasonically cleaning it with deionized water to obtain a pretreated substrate; S2. Modifying carbon-doped titanium dioxide on the pretreated substrate by medium-frequency magnetron sputtering to form an intermediate layer to obtain a first material; S3. Depositing lead dioxide on the intermediate layer by electroplating precipitation to form a lead dioxide surface layer, thereby obtaining the anode material.

2. The anode material according to claim 1, characterized in that The thickness of the lead dioxide surface layer is 120-150 μm.

3. The anode material according to claim 1, characterized in that The specific operation of S3 is as follows: the first material is used as the anode and the pure titanium plate is used as the cathode, which are fixed in the electrolytic cell respectively, and then the electrolyte is added, and the electrolyte is heated in a water bath to a temperature of 60-80°C, and the electrolyte is electroplated for 2.5-3 hours. After deposition, it is rinsed with deionized water to neutrality and dried at 70-80°C for 2-2.5 hours to obtain the anode material.

4. The anode material according to claim 3, characterized in that The electrolyte comprises lead nitrate, sodium fluoride and copper ions, wherein the concentration of the lead nitrate is 270-300 g / L, the concentration of the sodium fluoride is 8-9 g / L, and the concentration of the copper ions is 0.3-0.5 g / L.

5. The anode material according to claim 3, characterized in that The pH value of the electrolyte is 1.5-2.5.

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