A crystalline cobalt antimonate coating on a titanium electrode and a method for making the same
By preparing a crystalline cobalt antimonate coated titanium electrode, the problem of high cost of TiO2-RuO2 electrode was solved, and the chlorine evolution activity and stability were improved, reducing costs and extending service life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- RES CENT FOR ECO ENVIRONMENTAL SCI THE CHINESE ACAD OF SCI
- Filing Date
- 2023-01-04
- Publication Date
- 2026-06-26
Smart Images
Figure CN116162956B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of inorganic materials technology and relates to a crystalline cobalt antimonate coated titanium electrode and its preparation method. Background Technology
[0002] Chlorine (Cl2), as a crucial basic chemical, is widely used in polymer production, organic synthesis, the pulp and paper industry, and water treatment. In the chlor-alkali industry, Cl2 is primarily produced through an anodic electrochemical chlorine evolution reaction (CER) in an acidic, saturated NaCl aqueous solution. Furthermore, CER is also important in the on-site electrochemical treatment of wastewater. Chloride ions in wastewater can be oxidized into active chlorine species, including Cl2, HOCl, and ClO. - This helps with the oxidation of organic matter, the breakdown of heavy metal complexes, and disinfection and sterilization.
[0003] Hybrid metal oxide electrodes composed of TiO2 and RuO2 or IrO2 are the most widely used chlorine evolution electrodes in the chlor-alkali industry and water treatment. Due to the high cost of Ru and Ir, methods such as incorporating other metal elements (Ta, Co, Sn, and Nb) to modify porosity and adjust surface hydrophilicity / hydrophobicity have been used to improve the CER activity and stability of TiO2-RuO2 electrodes. However, the high cost of the precious metal Ru limits the large-scale application of TiO2-RuO2 electrodes. Therefore, we have developed a cobalt antimonate-coated titanium electrode without precious metals as a chlorine evolution electrode. Summary of the Invention
[0004] This invention provides a precious metal-free crystalline cobalt antimonate coated titanium electrode and its preparation method. The prepared cobalt antimonate electrode exhibits slightly lower chlorine evolution activity than the classic TiO2-RuO2 electrode, but a longer lifespan. Furthermore, the cost of the cobalt antimonate coating is only 1-2% of that of the TiO2-RuO2 coating.
[0005] The technical solution of the present invention is as follows:
[0006] A crystalline cobalt antimonate-coated titanium electrode was prepared by thermal decomposition annealing. The active component of the coating is crystalline CoSb₂O₆; Co and Sb elements are uniformly distributed in the coating; the precursor solution is prepared using the citric acid-ethylene glycol sol-gel method to complex Co and Sb metal ions, ensuring uniform dispersion of Co and Sb metal ions in the solution. The coating method is dip-coating to obtain a uniform and dense electrocatalytic film during thermal decomposition. Chlorine evolution activity was tested at 50 mmol / L NaCl and 20 mA / cm². 2Under conditions of high current density, the chlorine evolution rate of the cobalt antimonate-coated titanium electrode reached 78-85% of that of the TiO2-RuO2-coated titanium electrode. Accelerated lifetime testing was conducted at 1 mol / L H2SO4 and 1 A / cm². 2 Under conditions of high current density, the service life of cobalt antimonate coated titanium electrodes increased by 37-55% compared to TiO2-RuO2 coated titanium electrodes.
[0007] A specific method for preparing a crystalline cobalt antimonate coated titanium electrode is as follows:
[0008] (1) First, the titanium substrate is pretreated. The titanium sheet is polished with sandpaper, and then the grease is removed by ultrasonic cleaning with acetone, ethanol and water for 15 minutes respectively. The cleaned titanium sheet is placed in boiling 10% oxalic acid for 2 hours to etch it, and a titanium sheet with a uniform roughness gray surface is obtained. Then the etched titanium sheet is cleaned with deionized water and stored in anhydrous ethanol.
[0009] (2) Then, prepare the coating solution by dissolving a certain amount of citric acid in ethylene glycol and stirring at 60°C to obtain solution A;
[0010] (3) Dissolve a certain amount of cobalt salt and antimony salt in an alcohol solvent, add a small amount of concentrated HCl, and obtain a solution B with a total metal salt concentration of 0.5-1.5 mol / L. The molar ratio of Co to Sb in solution B is 1:(1-4).
[0011] (4) Mix solution A in (2) with solution B in (3) and stir at 60°C to dissolve, to obtain solution C. The molar ratio of ethylene glycol:citric acid:metal salt in solution C is 14:3:(1-3).
[0012] (5) Use an dip-coating machine to uniformly coat the solution C in (4) onto the pretreated titanium sheet in (1). After each coating, dry in an oven at 120-150℃ for 10-15 minutes, and then place it in a muffle furnace at 500-600℃ for 10-15 minutes. After calcination, remove the electrode from the muffle furnace and cool it to room temperature. Weigh the electrode before and after each coating to calculate the coating load.
[0013] (6) Repeat the coating process in (5) 12-18 times to achieve approximately 0.8-1.2 mg / cm³. 2 The coating loading was adjusted, and the electrode after the last coating was calcined at 500-600℃ for 1-2 hours. After naturally cooling to room temperature in a muffle furnace, it was removed to obtain a crystalline cobalt antimonate coated titanium electrode.
[0014] According to the method of the present invention, the preferred method is:
[0015] In step (3) above, the cobalt salt in solution B is CoSO4·7H2O, Co(NO3)2·6H2O or CoCl2·6H2O, the antimony salt is SbCl3 or antimony acetate, and the alcohol solvent is anhydrous ethanol, ethylene glycol, glycerol or terpineol.
[0016] In step (3) above, the molar ratio of Co to Sb in solution B is 1:(2-3).
[0017] In step (3) above, the total concentration of metal salt in solution B is 1 mol / L.
[0018] In step (4) above, the molar ratio of ethylene glycol:citric acid:metal salt in solution C is 14:3:2.
[0019] In step (5) above, the lifting speed of the dip-coating machine is 1-1.5 mm / s.
[0020] In step (5) above, the calcination temperature in the muffle furnace is 540-560℃.
[0021] For comparison, a classic TiO2-RuO2 coated titanium electrode was used, and its preparation method is as follows:
[0022] (1) First, the titanium substrate is pretreated. The titanium sheet is polished with sandpaper, and then the grease is removed by ultrasonic cleaning with acetone, ethanol and water for 15 minutes respectively. The cleaned titanium sheet is placed in boiling 10% oxalic acid for 2 hours to etch it, and a titanium sheet with a uniform roughness gray surface is obtained. Then the etched titanium sheet is cleaned with deionized water and stored in anhydrous ethanol.
[0023] (2) Dissolve 11.9g tetrabutyl titanate, 3.9g RuCl3·3H2O and 2mL concentrated HCl in 36mL of an equal volume of n-butanol / isopropanol to obtain a solution with a total metal concentration of 1mol / L and a molar ratio of Ti to Ru of 7:3.
[0024] (3) The solution in (2) is uniformly coated onto the pretreated titanium sheet in (1) at a lifting speed of 1.5 mm / s using an dip-coating machine. After each coating, the electrode is dried in an oven at 100°C for 10 minutes and then placed in a muffle furnace at 450°C for 15 minutes. After calcination, the electrode is taken out of the muffle furnace and cooled to room temperature. The electrode is weighed before and after each coating to calculate the coating load.
[0025] (4) Repeat the application process in (3) 15 times to achieve approximately 1 mg / cm³. 2 The coating loading was adjusted, and the electrode after the last coating was calcined at 450°C for 1.5 hours. After being naturally cooled to room temperature in a muffle furnace, it was removed to obtain a TiO2-RuO2 coated titanium electrode.
[0026] The technical features of this invention are as follows:
[0027] Compared to most current experiments based on doping modification of TiO2-RuO2 coated titanium electrodes, this invention presents a cobalt antimony-coated titanium electrode without precious metals, which, after optimization, achieves excellent chlorine evolution activity and stability. The chlorine evolution rate of the cobalt antimony-coated titanium electrode reaches 78-85% of that of the TiO2-RuO2 coated titanium electrode, and its lifetime is increased by 37-55% compared to the TiO2-RuO2 coated titanium electrode. Furthermore, the cost of the cobalt antimony coating is only 1-2% of that of the TiO2-RuO2 coating. Attached Figure Description
[0028] Figure 1 Flowchart for the fabrication of cobalt antimonate coated titanium electrodes;
[0029] Figure 2 CoSb in Example 1 2.5 O y Electrode XRD patterns;
[0030] Figure 3 The chlorine evolution rate at the electrode in Example 1;
[0031] Figure 4 This is the electrode accelerated life experiment in Example 1. Detailed Implementation
[0032] The present invention will now be described in detail with reference to specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.
[0033] Example 1
[0034] (1) First, the titanium substrate is pretreated. The titanium sheet (2cm×7cm) is polished with sandpaper, and then the grease is removed by ultrasonic cleaning with acetone, ethanol and water for 15 minutes respectively. The cleaned titanium sheet is then placed in boiling 10% oxalic acid for 2 hours to etch it, and a titanium sheet with a uniform roughness gray surface is obtained. The etched titanium sheet is then cleaned with deionized water and stored in anhydrous ethanol.
[0035] (2) Then, prepare the coating solution by adding 12.608g of citric acid to 17.380g of ethylene glycol and stirring in a water bath at 60°C for 0.5 hours to dissolve it, thus obtaining solution A;
[0036] (3) Dissolve 3.326g Co(NO3)2·6H2O, 6.518g SbCl3 and 1mL concentrated HCl in 40mL anhydrous ethanol to obtain solution B with a total metal salt concentration of 1mol / L. The molar ratio of Co to Sb in solution B is 1:2.5.
[0037] (4) Mix solution A in (2) with solution B in (3) and stir at 60°C for 3 hours to obtain solution C. The molar ratio of ethylene glycol:citric acid:metal salt in solution C is 14:3:2.
[0038] (5) Using an dip-coating machine, solution C from (4) is uniformly coated onto the pretreated titanium sheet from (1) at a dipping speed of 1.5 mm / s. After each coating, the electrode is dried in an oven at 150°C for 10 minutes, and then placed in a muffle furnace and calcined at 550°C for 15 minutes. After calcination, the electrode is removed from the muffle furnace and cooled to room temperature. The electrode is weighed before and after each coating to calculate the coating load.
[0039] (6) Repeat the application process in (5) 15 times to achieve approximately 1 mg / cm³. 2 The coating loading was adjusted, and the electrode after the final coating was calcined at 550°C for 1.5 hours. After natural cooling to room temperature in a muffle furnace, it was removed to obtain a cobalt antimonate-coated titanium electrode (CoSb) with a Co:Sb molar ratio of 1:2.5. 2.5 O y electrode).
[0040] (7) Chlorine evolution experiment: The prepared coated titanium electrode was used as the anode and stainless steel as the cathode. In a neutral aqueous solution of 50 mmol / L NaCl, at 20 mA / cm²... 2 Electrolysis was performed for 10 min under constant current conditions. The prepared CoSb was measured. 2.5 O y The chlorine evolution rate at the electrode was 0.23 mmol / cm². -2 h -1 The chlorine evolution rate of the prepared TiO2-RuO2 electrode was 0.27 mmol / cm. -2 h -1 CoSb 2.5 O y The chlorine evolution rate of the electrode reached 85% of that of the TiO2-RuO2 electrode.
[0041] (8) Accelerated life test: The prepared coated titanium electrode was cut into 1×1cm pieces. 2 The size is such that a titanium sheet is used as the anode and a titanium sheet as the cathode. In 1 mol / L H₂SO₄, at 1 A / cm⁻¹... 2 The test was conducted at a current density of [value missing], and the test was terminated when the cell voltage rose to 10V. The prepared CoSb [value missing] was measured. 2.5 O y The lifetime of the first electrode was 37.3 h, while the lifetime of the prepared TiO2-RuO2 electrode was 25.7 h. (CoSb) 2.5 O y The electrode lifetime is increased by 45% compared to the TiO2-RuO2 electrode.
[0042] Example 2
[0043] As described in Example 1, the difference is:
[0044] In step (3), 3.880g Co(NO3)2·6H2O, 6.083g SbCl3 and 1mL concentrated HCl are dissolved in 40mL anhydrous ethanol to obtain solution B, in which the molar ratio of Co to Sb is 1:2.
[0045] In step (5), after each application, the product is dried in an oven at 120°C for 15 minutes, and then placed in a muffle furnace and calcined at 560°C for 10 minutes.
[0046] In step (6), the application process in (5) is repeated 18 times to achieve approximately 1.2 mg / cm³. 2 The coating loading was adjusted, and the electrode after the final coating was calcined at 560°C for 2 hours. This yielded a cobalt antimonate-coated titanium electrode (CoSb₂O₃) with a Co:Sb molar ratio of 1:2. y electrode).
[0047] In step (7), CoSb2O was measured. y The chlorine evolution rate at the electrode was 0.21 mmol / cm². -2 h -1 CoSb2O y The chlorine evolution rate of the electrode reached 78% of that of the TiO2-RuO2 electrode.
[0048] In step (8), CoSb2O was measured. y When the cell voltage of the electrode rises to 10V, the electrode lifetime is 39.9h. (CoSb2O) y The electrode lifetime is increased by 55% compared to the TiO2-RuO2 electrode.
[0049] Step (1) is the same as in Example 1;
[0050] Step (2) is the same as in Example 1;
[0051] Step (4) is the same as in Example 1.
[0052] Example 3
[0053] As described in Example 1, the difference is:
[0054] In step (3), 2.910g Co(NO3)2·6H2O, 6.844g SbCl3 and 1mL concentrated HCl are dissolved in 40mL anhydrous ethanol to obtain solution B, in which the molar ratio of Co to Sb is 1:3.
[0055] In step (5), solution C from (4) is uniformly coated onto the pretreated titanium sheet from (1) at a dipping and lifting speed of 1 mm / s using an dip-coating machine. After each coating, the sheet is dried in an oven at 150°C for 10 minutes and then placed in a muffle furnace and calcined at 540°C for 15 minutes.
[0056] In step (6), the application process in (5) is repeated 12 times to achieve approximately 0.8 mg / cm³. 2 The coating loading was adjusted, and the electrode after the final coating was calcined at 540°C for 1 hour. This yielded a cobalt antimonate-coated titanium electrode (CoSb3O4) with a Co:Sb molar ratio of 1:3. y electrode).
[0057] In step (7), CoSb3O was measured. y The chlorine evolution rate at the electrode was 0.22 mmol / cm². -2 h -1 CoSb3O y The chlorine evolution rate of the electrode reached 81% of that of the TiO2-RuO2 electrode.
[0058] In step (8), CoSb3O was measured. y When the cell voltage of the electrode rises to 10V, the electrode lifetime is 35.2 hours. (CoSb3O) y The electrode lifetime is increased by 37% compared to the TiO2-RuO2 electrode.
[0059] Step (1) is the same as in Example 1;
[0060] Step (2) is the same as in Example 1;
[0061] Step (4) is the same as in Example 1.
Claims
1. A method for preparing a crystalline cobalt antimonate coated titanium electrode, comprising the following steps: (1) First, the titanium substrate is pretreated. The titanium sheet is polished with sandpaper, and then the grease is removed by ultrasonic cleaning with acetone, ethanol and water for 15 minutes respectively. The cleaned titanium sheet is placed in boiling 10% oxalic acid for 2 hours to etch it, and a titanium sheet with a uniform roughness gray surface is obtained. Then the etched titanium sheet is cleaned with deionized water and stored in anhydrous ethanol. (2) Then, prepare the coating solution by dissolving a certain amount of citric acid in ethylene glycol and stirring at 60°C to obtain solution A; (3) Dissolve a certain amount of cobalt salt and antimony salt in an alcohol solvent, and add a small amount of concentrated HCl to obtain a solution B with a total metal salt concentration of 0.5-1.5 mol / L; (4) Mix solution A in (2) with solution B in (3) and stir at 60°C to dissolve, to obtain solution C. The molar ratio of ethylene glycol:citric acid:metal salt in solution C is 14:3:(1-3). (5) Use an dip-coating machine to uniformly coat the solution C in (4) onto the pretreated titanium sheet in (1). After each coating, dry in an oven at 120-150℃ for 10-15 minutes, and then place it in a muffle furnace at 500-600℃ for 10-15 minutes. After calcination, remove the electrode from the muffle furnace and cool it to room temperature. Weigh the electrode before and after each coating to calculate the coating load. (6) Repeat the coating process in (5) 12-18 times to achieve a concentration of 0.8-1.2 mg / cm³. 2 The coating loading was adjusted, and then the electrode after the last coating was calcined at 500-600℃ for 1-2 hours. After naturally cooling to room temperature in a muffle furnace, it was removed to obtain a crystalline cobalt antimonate coated titanium electrode. (7) The crystalline cobalt antimonate electrode from (6) was subjected to chlorine evolution activity and accelerated life test. The chlorine evolution activity test was conducted at 50 mmol / L NaCl and 20 mA / cm 2 Accelerated lifetime testing was conducted at a current density of 1 mol / L H₂SO₄ and 1 A / cm⁻¹. 2 The experiment was conducted under conditions of current density.
2. The preparation method according to claim 1, characterized in that, In step (3), the cobalt salt in solution B is CoSO4·7H2O, Co(NO3)2·6H2O or CoCl2·6H2O, the antimony salt is SbCl3 or antimony acetate, the alcohol solvent is anhydrous ethanol, ethylene glycol, glycerol or terpineol, the molar ratio of Co to Sb in solution B is 1:(1-4), and the total concentration of the metal salt is 0.5-1.5 mol / L.
3. The preparation method according to claim 1, characterized in that, In step (4), the molar amount of the metal salt in solution C is the sum of the molar amounts of Co and Sb, and the molar ratio of ethylene glycol:citric acid:metal salt in solution C is 14:3:(1-3).
4. The preparation method according to claim 1, characterized in that, In step (5), the coating is applied by an automated dip-coating method, and the dipping speed of the dip-coating machine is 1-1.5 mm / s.
5. The preparation method according to claim 1, characterized in that, In step (5), the electrode is calcined in a muffle furnace at a temperature of 500-600°C and held for 10-15 minutes.
6. The preparation method according to claim 1, characterized in that, In step (6), the electrode is calcined in a muffle furnace at a temperature of 500-600℃ and held for 1-2 hours.
7. The preparation method according to claim 1, characterized in that, The prepared electrode is a crystalline cobalt antimonate coated titanium electrode. The electrode coating does not contain precious metals. The chlorine evolution rate of the cobalt antimonate coated titanium electrode reaches 78-85% of that of the TiO2-RuO2 coated titanium electrode, and the lifespan is increased by 37-55% compared with the TiO2-RuO2 coated titanium electrode. Moreover, the cost of the cobalt antimonate coating is only 1-2% of that of the TiO2-RuO2 coating.