TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of electrochemical water treatment, and particularly relates to a TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode and a preparation method and application thereof.The composite electrode comprises a TiO2-NTs substrate, a Ti4O7-NTs middle layer growing on the surface of the TiO2-NTs substrate in situ and a Ce-Sb co-doped SnO2 active layer coating the Ti4O7-NTs middle layer; wherein in the Ce-Sb co-doped SnO2 active layer, the molar ratio of Sn to Ce to Sb is (8 to 9.4) to (0.5 to 1.5) to (0.1 to 0.5); the composite electrode has a hierarchical structure, the Ti4O7-NTs intermediate layer strengthens interface bonding through an anchoring effect, Ce-Sb double doping synergistically optimizes conductivity and catalytic activity, when the composite electrode is applied to salt-containing organic wastewater degradation as an anode, an electrolysis system is constructed to adjust conductivity, 1-10 V direct current voltage is applied to electrolyze for 0.5-3 h, the rhodamine B degradation rate is higher than 95% within 90 min, the COD removal rate reaches 92%, and the composite electrode can be applied to degradation of salt-containing organic wastewater. The continuous service life exceeds 300 hours, the energy consumption is low, the salt resistance is excellent, and the method is suitable for efficient treatment of salt-containing degradation-resistant organic wastewater in the industries of printing and dyeing, chemical engineering and the like.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical water treatment technology, specifically relating to TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrodes, their preparation methods, and applications. Background Technology

[0002] Saline organic wastewater widely originates from industrial production processes such as dyeing, printing and dyeing, chemicals, pharmaceuticals, and pesticides. Its core characteristics include high salt concentration (total dissolved solids (TDS) often ≥3.5%), stable organic pollutant structure (often containing rigid groups such as benzene rings and azo bonds), and poor biodegradability (BOD5 / COD ratio typically below 0.3). Traditional treatment technologies are inadequate. Biological treatment is easily inhibited by high-salt environments, leading to microbial inactivation; physical adsorption only achieves phase transfer of pollutants without complete mineralization; and chemical oxidation suffers from high reagent dosage and operating costs, all of which fail to meet the demands of industrial-scale deep treatment.

[0003] Electrochemical oxidation, with its advantages of strong oxidizing power, mild reaction conditions, and no secondary pollution, has become a core technology for treating saline and recalcitrant organic wastewater. Electrode materials, as the core carrier of this technology, directly determine degradation efficiency and operational economics. SnO2-based electrodes have gained widespread attention in the field of electrocatalysis due to their high oxygen evolution overpotential (approximately 1.7V vs SCE), good chemical stability, and cost advantages. However, pure SnO2 electrodes have inherent drawbacks: their room temperature resistivity is high... Its poor conductivity and low density of surface active sites severely limit its practical application effectiveness.

[0004] Doping modification is a key technology for optimizing the performance of SnO2 electrodes. Sb, as a classic n-type dopant, can significantly reduce electrode resistivity by introducing free charge carriers, with the optimal doping amount typically controlled at 5-10 at%. However, single Sb-doped electrodes still face bottlenecks in terms of the number of active sites and long-term operational stability, making it difficult to meet the requirements of long-term continuous treatment of high-salt wastewater.

[0005] The interfacial bonding strength between the electrode substrate and the active layer is a core factor affecting the electrode's lifespan. In traditional titanium-based SnO2 electrodes, the active coating and substrate are mostly physically attached, which is prone to detachment due to stress during electrolysis, leading to the loss of active components. Ti4O7, as a novel conductive ceramic material, possesses both high conductivity (resistivity...) Due to its chemical inertness, the preparation of Ti4O7 in existing technologies mostly adopts high-temperature gas reduction or solid carbon source reduction methods. These methods have problems such as high energy consumption, stringent equipment requirements, and difficulty in accurately controlling the integrity of the nanotube array structure.

[0006] Meanwhile, research on Ce-Sb dual-doped SnO2 electrodes is mostly based on planar titanium-based or carbon-based supports, which suffers from problems such as low active layer loading, long electron transport paths, and high interfacial impedance. Furthermore, long-term stability data under high-salt environments has not yet met industrial application standards. In particular, for typical recalcitrant pollutants such as phenol and aniline, the mineralization efficiency (TOC removal rate is mostly below 65%) and energy consumption (energy consumption per unit COD treatment ≥ 4.5 kWh / kg) of existing electrodes still have significant room for improvement. Therefore, developing a Ce-Sb doped SnO2 composite electrode based on a Ti4O7-NTs interlayer prepared by cathodic reduction is of great practical significance for overcoming existing technological bottlenecks. Summary of the Invention

[0007] To address the technical problems of high energy consumption in the preparation of Ti4O7, weak bonding between the Ce-Sb-doped SnO2 electrode substrate and the active layer, limited specific surface area, insufficient stability under high salt conditions, and low mineralization efficiency for recalcitrant pollutants such as phenol and aniline, this invention provides a TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode and its preparation method. The Ti4O7-NTs intermediate layer is prepared by cathodic reduction (using a specific electrolyte composition and reaction parameters). Combining its three-dimensional support with the synergistic effect of Ce-Sb dual doping, the electrode's conductivity, catalytic activity, and stability are simultaneously optimized. The prepared composite electrode exhibits core performance advantages such as low resistivity, high oxygen evolution overpotential, and high active site density.

[0008] To achieve the above objectives, the present invention provides a TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode, the composite electrode comprising: a TiO2-NTs substrate, a Ti4O7-NTs intermediate layer grown in situ on the surface of the TiO2-NTs substrate, and a Ce-Sb co-doped SnO2 active layer coated on the Ti4O7-NTs intermediate layer; wherein, in the Ce-Sb co-doped SnO2 active layer, the molar ratio of Sn, Ce and Sb is (8-9.4):(0.5-1.5):(0.1-0.5).

[0009] Preferably, the composite electrode has a continuous service life of ≥300 h in 5000 mg / L NaCl solution.

[0010] A second aspect of the present invention provides a method for preparing a TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode, the method comprising the following steps: S1, TiO2-NTs substrate preparation: using foamed titanium as the anode, oxidation is carried out in ethylene glycol electrolyte to grow an ordered TiO2 nanotube array on the surface of the foamed titanium in situ, thus obtaining the TiO2-NTs substrate; S2, Ti4O7-NTs intermediate layer preparation; prepare cathode reduction electrolyte, use the inactive region of TiO2-NTs substrate as cathode, perform cathode electrolytic reduction in constant current mode to grow TiO2-NTs in situ into Ti4O7-NTs, and obtain the Ti4O7-NTs intermediate layer after rinsing and drying. S3, Ce-Sb co-doped SnO2 active layer preparation: The precursor solution is prepared according to the above molar ratio, and after sol and gelation, it is uniformly coated on the surface of the Ti4O7-NTs intermediate layer, and then placed in a muffle furnace for calcination to form Ce-Sb co-doped SnO2 active layer. After cooling to room temperature with the furnace, the TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode is obtained.

[0011] Preferably, in step S1, the ethylene glycol electrolyte contains 0.1-1.5 wt% NH4F and 1-5 vol% H2O; during the oxidation process, anodic oxidation is carried out for 1-3 hours under a constant voltage of 40-60V.

[0012] Preferably, in step S2, during the cathode electrolytic reduction process, the anode is a Pt mesh, and the cathode reduction electrolyte consists of 0.5-2M (NH4)2SO4 and composition.

[0013] Preferably, in step S2, during the electrolytic reduction process, the current density is 10-30 mA / cm². 2 The electrolysis time is 1-3 hours.

[0014] Preferably, in step S3, during the preparation of the precursor solution, the Sn-containing compound, the Sb-containing compound, and the Ce-containing compound are dissolved in an organic solvent, and a complexing agent is added and stirred until a uniform and transparent precursor solution is formed; wherein, the molar ratio of Sn, Ce and Sb is (8-9.4):(0.5-1.5):(0.1-0.5).

[0015] Preferably, in step S3, during the sol and gel process, the precursor solution is placed in a constant temperature water bath environment of 30℃-60℃ and stirred for 2 h-6 h to form a sol, which is then placed in a sealed container and aged at room temperature for 12 h-24 h to form a gel.

[0016] Preferably, in step S3, during the coating process, the coating is repeated 5-10 times using the dip-coating method or spin coating method, and after each coating, it is placed in an oven at 60℃-120℃ to dry for 0.5 h-2 h; During the calcination process, the heating temperature is 450℃-550℃, and the holding time is 1h-3h.

[0017] The third aspect of this invention provides the application of the above-mentioned composite electrode in the degradation of saline organic wastewater.

[0018] The beneficial technical effects of the present invention are as follows: The Ti4O7-NTs interlayer preparation of this invention features low energy consumption and high controllability: it employs a specific electrolyte composition and constant current reduction parameters, eliminating the need for high temperature and inert gas protection, resulting in a gentle preparation process. Furthermore, the interlayer formation area is precisely controlled through tape winding, ensuring both the purity of the Ti4O7 crystal phase and the integrity of the nanotube structure. This significantly improves the uniformity of the interlayer structure, solving the problems of high energy consumption and easy structural damage associated with traditional high-temperature reduction methods. Energy consumption is reduced by more than 60% compared to traditional high-temperature reduction methods.

[0019] The composite electrode prepared by this invention can achieve a degradation rate of over 90% for recalcitrant pollutants such as crystal violet and acid red; especially for Rhodamine B pollutants, the degradation rate can reach over 95% within 90 minutes, which is significantly better than existing similar electrodes.

[0020] The strong bonding between the Ti4O7-NTs intermediate layer and the active layer of this invention significantly extends the electrode life and reduces the replacement frequency. Compared with traditional planar titanium-based electrodes, the interfacial bonding strength is increased by more than 40%, which can effectively suppress the shedding of the active layer during electrolysis. The preparation process combining cathode reduction and sol-gel has the characteristics of simple operation, easy control of doping concentration, and high raw material utilization (≥90%), making it suitable for large-scale industrial production. The electrode preparation cost is reduced by more than 60% compared with Ti / IrO2-Ta2O5 electrodes.

[0021] The composite electrode prepared by this invention exhibits excellent salt resistance: in high-salt environments, there is no obvious corrosion on the electrode surface. The three-dimensional Ti4O7-NTs intermediate layer can effectively disperse the local stress generated during electrolysis. Combined with the repair effect of Ce element on lattice defects, the electrode's continuous service life in 5000 mg / L NaCl solution exceeds 300 hours, which is more than 2.5 times that of the traditional Ti / Sb-SnO2 electrode. This solves the technical problem of poor stability of traditional electrodes in high-salt wastewater treatment and is suitable for the efficient treatment of salty and difficult-to-degrade organic wastewater in industries such as printing and dyeing and chemical processing. Attached Figure Description

[0022] Figure 1The impedance spectra of foamed titanium / Ti4O7-NTs electrodes prepared under different cathode reduction conditions provided by this invention are shown.

[0023] Figure 2 This is a diagram showing the oxygen evolution potential of foamed titanium / Ti4O7-NTs electrodes prepared under different anodic oxidation voltages, provided by the present invention.

[0024] Figure 3 These are X-ray diffraction (XRD) patterns of the electrodes prepared in Example 1 and Comparative Example 1 of this invention.

[0025] Figure 4 These are the AC impedance spectra of the electrodes of Examples 1, 3, and 4 of this invention in 0.5 mol / L H2SO4 solution.

[0026] Figure 5 This is a comparison chart of COD removal efficiency between Examples 1-2 and Comparative Examples 1-4 of the present invention.

[0027] Figure 6 This is a comparison chart of the degradation rates of Rhodamine B in saline organic wastewater in Examples 1-2 and Comparative Examples 1-4 of the present invention.

[0028] Figure 7 This is a comparison chart of the degradation rates of crystal violet, methyl orange, and acid red by the composite electrode prepared in Example 1 of this invention.

[0029] Figure 8 This is the stability test curve of the composite electrode prepared in Example 1 of this invention under the accelerating current density. Detailed Implementation

[0030] This invention discloses a TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode, its preparation method, and its applications. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired results. It is particularly important to note that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0031] This invention employs a two-step method—intermediate layer cathode reduction preparation and active layer sol-gel modification—to prepare TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrodes. The specific process is as follows: S1, TiO2-NTs substrate preparation: using foamed titanium as the anode, oxidation is carried out in ethylene glycol electrolyte to grow an ordered TiO2 nanotube array on the surface of the foamed titanium in situ, thus obtaining the TiO2-NTs substrate; Specifically, in step S1, foamed titanium is selected as the substrate material, and its porous structure is used to further enhance the three-dimensional support effect. The pretreated foamed titanium is used as the anode and Pt sheet is used as the cathode. The substrate is placed in an ethylene glycol electrolyte containing 0.1-1.5wt% NH4F and 1-5vol% H2O and anodized for 1-3 hours under a constant voltage of 40-60V. An ordered TiO2 nanotube array (TiO2-NTs) is grown in situ on the substrate surface. After rinsing with deionized water and drying, the TiO2-NTs substrate is obtained.

[0032] S2, Ti4O7-NTs intermediate layer preparation; prepare cathode reduction electrolyte, use the inactive region of TiO2-NTs substrate as cathode, perform cathode electrolytic reduction in constant current mode to grow TiO2-NTs in situ into Ti4O7-NTs, and obtain the Ti4O7-NTs intermediate layer after rinsing and drying. Specifically, in step S2, during the preparation of the Ti4O7-NTs intermediate layer, it is necessary to strictly follow the steps to ensure the crystal phase purity of Ti4O7 and the integrity of the nanotube structure. The Ti4O7 nanotube array (Ti4O7-NTs) provides a three-dimensional support interface, and the "anchoring effect" enhances the bonding force between the active layer and the substrate. In step S2, during the preparation of the Ti4O7-NTs intermediate layer, the electrolyte is first prepared by weighing (NH4)2SO4 and... Dissolve the solid in deionized water, then place the solution in a constant temperature water bath and stir continuously until the solid is completely dissolved. The solution will turn pale yellow, yielding 0.5-2M (NH4)2SO4 and The cathode reduction electrolyte, in which (NH4)2SO4 is the supporting electrolyte. This promotes the uniformity of the reduction reaction and avoids excessive local reduction on the electrode surface. A cathodic reduction reaction is then performed, using TiO2-NTs in the exposed active region as the cathode and a Pt mesh as the anode to construct a dual-electrode electrolysis system. Electrolytic reduction is carried out in constant current mode with a current density of 10-30 mA / cm². 2 The electrolysis time is 1-3 h, achieving efficient conversion of TiO2 to Ti4O7 at room temperature without damaging the nanotube array structure. After the reaction is completed, the electrode is removed from the electrolyte and repeatedly rinsed with distilled water until no electrolyte residue remains on the surface. Then it is dried in an 80℃ vacuum drying oven to obtain the Ti4O7-NTs intermediate layer.

[0033] Preparation of S3, Ce-Sb co-doped SnO2 active layer: A precursor solution was prepared by molar ratio, and after sol and gelation, it was uniformly coated on the surface of Ti4O7-NTs intermediate layer, and then placed in a muffle furnace for calcination to form Ce-Sb co-doped SnO2 active layer. After cooling to room temperature with the furnace, TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode was obtained. Specifically, in step S3, a precursor solution is first prepared by weighing Sn-containing, Sb-containing, and Ce-containing compounds according to stoichiometric ratios, wherein the preferred molar ratio of Sn, Ce, and Sb is (8-9.4):(0.5-1.5):(0.1-0.5), for example, 8:0.5:0.1, 8.5:0.8:0.2, 9:1.2:0.4, or 9.4:1.5:0.5. The metal compounds are dissolved in anhydrous ethanol or ethylene glycol organic solvents, and citric acid or ethylenediaminetetraacetic acid is added as a complexing agent. The mixture is stirred continuously at room temperature for 2-4 hours to form a uniform and transparent precursor solution. This ratio range, through precise control of the dopant element content, effectively avoids the problem of exacerbated lattice distortion caused by high Ce doping, while ensuring the full utilization of Sb's conductivity modification effect. The resulting precursor solution is then placed in a constant temperature water bath at 30℃-60℃ and continuously stirred for 2-6 hours. A homogeneous sol is formed through hydrolysis and condensation reactions, and then aged in a sealed container at room temperature for 12-24 hours to allow the sol to fully age and form a stable gel. The gel is then uniformly coated onto the pretreated Ti4O7-NTs intermediate layer surface using either a dip-coating method (coating speed 3-5 cm / min) or a spin-coating method (speed 1500-2500 r / min). After each coating, the substrate is immediately dried in a 60-120℃ oven for 0.5-2 hours, repeating the coating 5-10 times to control the active layer thickness and ensure coating uniformity and integrity. Finally, the dried substrate is placed in a muffle furnace and heated to 450-550℃ at a rate of 2-5℃ / min. The gel was calcined at ℃ in air for 1-3 h to thermally decompose the gel and form a crystalline Ce-Sb-doped SnO2 active layer. After cooling to room temperature in the furnace, a TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode was obtained.

[0034] The application strategy of the TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode provided by this invention in the degradation of saline organic wastewater is as follows: A two-dimensional electrolysis system was constructed by using the prepared composite electrode as the anode and a platinum or graphite electrode as the cathode. Electrolytes such as NaCl were added to saline organic wastewater to adjust the conductivity to the target range, and a DC voltage was applied to initiate the electrolysis reaction. In this system, the electrode surface efficiently generates highly oxidizing active species ·OH through anodizing, which can non-selectively attack the molecular structure of organic pollutants, achieving ring opening and deep mineralization of benzene rings. Simultaneously, under high-salt conditions, the Cl in the solution… - An oxidation reaction occurs on the anode surface to generate chlorine-containing oxides such as Cl2 and HClO, forming a synergistic oxidation system of "hydroxyl radicals-chlorine-containing species" that accelerates the degradation process of Rhodamine B pollutants.

[0035] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0036] Unless otherwise specified, the following embodiments are all conventional methods.

[0037] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0038] Example 1 S1. Preparation of TiO2-NTs substrate: The surface oxide layer of the foamed titanium substrate was removed by sequentially polishing with 400# and 800# sandpaper. It was then ultrasonically cleaned in acetone for 20 minutes to remove oil, rinsed with deionized water, and dried for later use. Using the treated foamed titanium as the anode and a platinum sheet as the cathode, TiO2-NTs were obtained by anodic oxidation at a constant voltage of 60V for 3 hours in an ethylene glycol electrolyte containing 0.5wt% NH4F and 2vol% H2O. After rinsing and drying, the NTs were ready for use.

[0039] Preparation of S2 and Ti4O7-NTs interlayer: Weigh 26.4278g of (NH4)2SO4 and Dissolve the TiO2-NTs in 200 mL of deionized water and stir in a constant temperature water bath until completely dissolved and turning pale yellow to obtain the cathode reducing electrolyte. Wrap the inactive region of TiO2-NTs with tape, exposing only the surface of TiO2-NTs. Using this electrode as the cathode and a Pt mesh as the anode, set the current density to 15 mA / cm². 2 The electrode was reduced by constant current electrolysis for 1.5 h. After the reaction was completed, the electrode was rinsed with distilled water and dried in a vacuum drying oven at 80 °C to obtain the Ti4O7-NTs substrate.

[0040] Preparation of S3 and Ce-Sb co-doped SnO2 active layer; Preparation of precursor solution: Accurately weigh 9 mmol tin tetrachloride, 1 mmol antimony trichloride, and 0.2 mmol cerium nitrate, dissolve them in 50 mL anhydrous ethanol, add 5 mmol citric acid as a complexing agent, and stir continuously at room temperature for 3 h until completely dissolved to obtain a uniform and transparent precursor solution. Sol-gel and coating: The precursor solution was placed in a 40℃ constant temperature water bath and stirred for 4 hours to form a homogeneous sol. The sol was transferred to a sealed container and aged at room temperature for 18 hours to obtain a stable gel. The gel was coated on the surface of Ti4O7-NTs substrate using the dip-coating method (coating speed 5cm / min). After each coating, the substrate was dried in an 80℃ oven for 1 hour. The coating was repeated 10 times. Calcination and shaping: The substrate with the coating dried is placed in a muffle furnace and heated to 500℃ at a heating rate of 5℃ / min. It is then calcined in air for 2 h and cooled to room temperature with the furnace to obtain the TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode.

[0041] Degradation of organic dye wastewater: The prepared TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode was used as the anode, and a platinum electrode was used as the cathode. The electrode was placed in simulated saline organic wastewater containing Rhodamine B, and electrolysis was performed for 1.5 hours under a 5V DC voltage. Testing showed that the degradation rate of the simulated saline organic wastewater containing Rhodamine B reached 96%.

[0042] The prepared titanium foam / Ti4O7-NTs / Ce-Sb co-doped SnO2 electrode was tested at 1 A / cm in a 5000 mg / L NaCl solution. 2 Stability tests were conducted at accelerated current density. During the test, the voltage generally showed a slow upward trend, such as... Figure 8 As shown, the voltage suddenly rose to 10V at 183 min, indicating that the active layer on the electrode surface had detached. The experiment was terminated according to the test settings. The actual lifespan of the electrode was calculated according to the given formula: T2=T1·(i1 / i2) 2 The acceleration test current density i1 = 1 A / cm 2 Based on the current density i1, the test life T1 = 3.05h, and the actual operating current density i2 = 0.1 A / cm². 2 The calculated actual lifespan is 305 hours.

[0043] Example 2 In step S3, 8 mmol of stannous chloride, 1.5 mmol of antimony pentachloride, and 0.5 mmol of cerium chloride were weighed and dissolved in 40 mL of ethylene glycol. 6 mmol of ethylenediaminetetraacetic acid was added as a complexing agent, and the mixture was stirred for 4 hours to obtain a precursor solution. The precursor solution was subjected to hydrolysis and condensation reaction at 50 °C for 3 hours to obtain a sol, which was then aged for 20 hours to become a gel. The titanium mesh was pretreated using the same method as in Example 1, and the gel was coated onto the Ti4O7-NTs substrate surface using the dip-coating method (coating speed 5 cm / min). After each coating, the substrate was dried in an oven at 80 °C for 1 hour, and the coating was repeated 10 times. The coated titanium mesh was calcined at 500 °C for 2 hours to obtain a Ce-Sb-doped SnO2 electrode. The remaining steps were the same as in Example 1.

[0044] Degradation of organic dye wastewater: In simulated saline organic wastewater containing Rhodamine B, using this electrode as the anode and a graphite electrode as the cathode, a voltage of 7V was applied, and electrolysis was performed for 2 hours. The degradation rate of simulated saline organic wastewater containing Rhodamine B reached 93%.

[0045] Comparative Example 1 A titanium foam / Sb-SnO2 electrode was prepared using a pure titanium sheet as the substrate. The precursor ratio in step S3 did not contain Ce, and the Ti4O7-NTs intermediate layer preparation in step S2 was not performed. The remaining steps were the same as in Example 1, and a titanium foam / Sb-SnO2 electrode was obtained.

[0046] Degradation of organic dye wastewater: The prepared Sb-SnO2 electrode was used as the anode and the platinum electrode as the cathode. The electrode was placed in simulated Rhodamine B saline organic wastewater, and a 5V DC voltage was applied for electrolysis for 1.5 hours. Testing showed that the degradation rate of the simulated Rhodamine B saline organic wastewater was 62%, and the COD removal rate was 70%, significantly lower than in Example 1.

[0047] Comparative Example 2 A foamed titanium / Ce-Sb-SnO2 electrode was prepared using a pure titanium sheet as the substrate. The Ti4O7-NTs intermediate layer preparation in step S2 was omitted, and the remaining steps were the same as in Example 1, resulting in a foamed titanium / Ce-Sb-SnO2 electrode.

[0048] Degradation of organic dye wastewater: The prepared foamed titanium / Ce-Sb-SnO2 electrode was used as the anode and the platinum electrode as the cathode. The electrode was placed in simulated Rhodamine B-containing saline organic wastewater, and a 5V DC voltage was applied for electrolysis for 1.5 hours. Testing showed that the degradation rate of the simulated Rhodamine B-containing saline organic wastewater was 83%, and the COD removal rate was 81%, significantly lower than in Example 1.

[0049] Comparative Example 3 To prepare a foamed titanium / Ti4O7 / SnO2 electrode, 10 mmol of tin tetrachloride was weighed and dissolved in 50 mL of anhydrous ethanol. 5 mmol of citric acid was added, and a pure SnO2 electrode was prepared following the same sol-gel, coating, drying, and calcination steps as in Example 1.

[0050] Degradation of organic dye wastewater: A pure SnO2 electrode was used as the anode and a platinum electrode as the cathode, placed in simulated Rhodamine B saline organic wastewater, and electrolyzed for 1.5 hours under a 5V DC voltage. The degradation rate of the simulated Rhodamine B saline organic wastewater was measured to be 45%, significantly lower than in Example 1.

[0051] Comparative Example 4 To prepare a foamed titanium / Ti4O7 / Sb-SnO2 electrode, 10 mmol of tin tetrachloride and 1 mmol of antimony trichloride were weighed and dissolved in 50 mL of anhydrous ethanol. 5 mmol of citric acid was added, and the Sb-doped SnO2 electrode was prepared following the same subsequent steps as in Example 1.

[0052] Degradation of organic dye wastewater: The prepared foamed titanium / Ti4O7 / Sb-SnO2 electrode was used as the anode and the platinum electrode as the cathode. The electrode was placed in simulated Rhodamine B-containing saline organic wastewater, and a 5V DC voltage was applied for electrolysis for 1.5 hours. Testing showed that the degradation rate of the simulated Rhodamine B-containing saline organic wastewater was 75%, significantly lower than in Example 1.

[0053] The experimental results are as follows: For the titanium foam / Ti4O7-NTs prepared in step S2 of Example 1 under cathodic reduction conditions, the charge transfer resistance of the prepared titanium foam / Ti4O7-NTs electrode was measured after changing the cathodic reduction conditions. The specific measurement results are shown in Table 1: Table 1. Fitted resistance of titanium foam / Ti4O7-NTs electrode under different cathodic reduction conditions

[0054] As shown in Table 1, the charge transfer resistance of the electrodes varies considerably under different cathode reduction conditions. At 40 V and 1.5 h, the polarization current density ranges from 3 mA / cm². 2 Increased to 15 mA / cm 2 The charge transfer internal resistance decreased from 735.4Ω to 301Ω; at 60 V and 10 mA / cm 2 Under these conditions, as the polarization time increased from 1 h to 1.5 h, the charge transfer internal resistance decreased from 599.7 Ω to 439.8 Ω; while at 15 mA / cm 2Under 1.5 h conditions, the anodic oxidation voltage increased from 40 V to 60 V, while the charge transfer internal resistance decreased slightly from 301 Ω to 93.2 Ω. Figure 1 Impedance spectra of foamed titanium / Ti4O7-NTs electrodes prepared under different cathodic reduction conditions are shown in the figure. As can be seen from the figure, the intersection points of the fitted curves with the real axis for all electrodes are small and the values ​​are close, indicating that their ohmic resistance is small and the differences are not significant. This confirms that cathodic reduction treatment significantly improves the electrode conductivity. Therefore, increasing the polarization current density and extending the polarization time can effectively reduce the charge transfer resistance, promote the transport of substances on the electrode surface, and improve its catalytic performance. Compared with polarization current density and polarization time, the anodic oxidation voltage has a smaller impact on the electrochemical performance of the electrode. When the polarization current density is 15 mA / cm², the effect is relatively small. 2 When the polarization time is 1.5 h, the electrode prepared under anodizing voltage of 60 V exhibits the best mass transport capability and electrochemical performance, which is slightly better than the electrode prepared under voltage of 40 V.

[0055] Figure 2 To investigate the effect of anodic oxidation voltage on the oxygen evolution potential of titanium foam / Ti4O7-NTs prepared by cathodic reduction, linear sweep voltammetry was performed on the electrodes. The preparation conditions for the two sets of electrodes were an anodic oxidation voltage of 40 V and a polarization current density of 15 mA / cm². 2 The polarization time was 1.5 h and the anodic oxidation voltage was 60 V, with all other conditions remaining the same as before. Figure 2 shows that the polarization curve of the electrode can be divided into two regions. At the boundary between these regions, the relationship between voltage and current changes significantly. In the first region, the current remains relatively constant with increasing voltage. However, in the second region, the current increases sharply with increasing voltage, indicating that the oxygen evolution reaction occurs in this rising segment of the curve. At an anodic oxidation voltage of 40 V, the oxygen evolution potential of the prepared electrode was 1.596 V. When the anodic oxidation voltage was increased to 60 V, the oxygen evolution potential became 1.888 V. This result indicates that as the anodic oxidation voltage increases, the oxygen evolution potential of the electrode also increases. A higher oxygen evolution potential helps reduce the likelihood of oxygen evolution side reactions and reduces current loss. Therefore, from the perspective of oxygen evolution potential, the electrode prepared at 60 V oxidation voltage performs significantly better than the electrode prepared at 40 V. In summary, the optimal cathode reduction conditions are an anodic oxidation voltage of 60 V and a polarization current density of 15 mA / cm². 2 The polarization time is 1.5 h.

[0056] Figure 3The XRD comparison diagrams of the electrodes of Example 1 and Comparative Example 4 are shown. The horizontal axis represents the 2θ angle (unit: °), and the vertical axis represents the diffraction intensity (relative value). As can be seen from the figure, all samples show the characteristic diffraction peaks of SnO2 (corresponding to JCPDS standard card No. 41-1445, such as 2θ = 26.6°, 33.8°, and 37.9°, which correspond to the (110), (101), and (200) crystal planes of SnO2, respectively, indicating that doping did not change the rutile crystal structure of SnO2; in addition, no oxide impurity peaks of Ce or Sb were found in Example 1, indicating that Ce and Sb elements were successfully incorporated into the SnO2 lattice, achieving effective doping.

[0057] Figure 4 The figures show the electrochemical impedance spectroscopy (EIS) spectra of the electrodes from Examples 1, 3, and 4 in 0.5 mol / L H₂SO₄ solution. Compared to the pure SnO₂ electrode, the high-frequency semicircle diameter of the Sb-doped SnO₂ electrode is significantly reduced, while the semicircle diameter of the Ce-Sb co-doped electrode is the smallest, indicating that co-doping can significantly reduce charge transfer resistance. As shown in Figure 4, the Rct of the electrode from Example 1 is much lower than that of Comparative Examples 3 and 4, indicating that the co-doping of Ce and Sb can synergistically improve the conductivity of the electrode, reduce electron transport resistance, and provide a good electron transport channel for the electrochemical oxidation and degradation of organic dyes.

[0058] Figure 5 This is a comparison chart of COD removal efficiency between Examples 1-2 and Comparative Examples 1-4. Under the same electrolysis conditions, the electrode of Example 1 achieved a COD removal rate of 92% for Rhodamine B-simulated saline organic wastewater, significantly better than the other comparative electrodes. This excellent treatment effect is mainly due to the multiple advantages brought by Ce-Sb synergistic doping: Ce 3+ The introduction of Ce improves the uniformity and density of the electrode surface, significantly increasing the effective reaction area. At the same time, the synergistic effect of Ce and Sb greatly reduces the charge transfer resistance of the electrode, providing an efficient electron transport channel for the electrochemical oxidation process and promoting the continuous generation of reactive oxygen species such as hydroxyl radicals.

[0059] Figure 6 The graphs show a comparison of the degradation rates of Rhodamine B-containing organic wastewater in Examples 1-2 and Comparative Examples 1-4. It can be seen that the composite electrode prepared in Example 1 exhibits superior degradation performance for Rhodamine B-containing organic wastewater, with a degradation rate as high as 96%, significantly higher than that of the Sb-doped SnO2 electrode (75%) and the pure SnO2 electrode (45%). This highly efficient degradation capability for complex-structured dyes stems from the optimization effect of Ce doping on the electron cloud distribution of SnO2, significantly enhancing the intrinsic activity of the surface catalytic active sites. Combined with its excellent charge transport characteristics, this ensures the efficient generation of reactive oxygen species and the rapid oxidative decomposition of dye molecules.

[0060] Figure 7 This is a comparison of the degradation rates of three different types of dyes (crystal violet, methyl orange, and acid red) on the foamed titanium / Ti4O7-NTs / Ce-Sb co-doped SnO2 electrode prepared in Example 1. The data in the figure show that this composite electrode exhibits excellent degradation efficiency for all three recalcitrant dyes. The degradation rates of all three dyes are consistently above 90%, indicating that this composite electrode has a broad-spectrum and highly efficient degradation capability for organic dye pollutants with different structural types.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode, characterized in that, The composite electrode comprises: a TiO2-NTs substrate, a Ti4O7-NTs intermediate layer grown in situ on the surface of the TiO2-NTs substrate, and a Ce-Sb co-doped SnO2 active layer coated on the Ti4O7-NTs intermediate layer; wherein, in the Ce-Sb co-doped SnO2 active layer, the molar ratio of Sn, Ce and Sb is (8-9.4):(0.5-1.5):(0.1-0.5).

2. The TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode according to claim 1, characterized in that, The composite electrode has a continuous service life of ≥300 h in 5000 mg / L NaCl solution.

3. A method for preparing a TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode, characterized in that, The preparation method includes the following steps: S1, TiO2-NTs substrate preparation: using foamed titanium as the anode, oxidation is carried out in ethylene glycol electrolyte to grow an ordered TiO2 nanotube array on the surface of the foamed titanium in situ, thus obtaining the TiO2-NTs substrate; S2, Ti4O7-NTs intermediate layer preparation; prepare cathode reduction electrolyte, use the inactive region of TiO2-NTs substrate as cathode, perform cathode electrolytic reduction in constant current mode to grow TiO2-NTs in situ into Ti4O7-NTs, and obtain the Ti4O7-NTs intermediate layer after rinsing and drying. S3, Ce-Sb co-doped SnO2 active layer preparation: The precursor solution is prepared according to the molar ratio in claim 1, and after sol and gelation, it is uniformly coated on the surface of the Ti4O7-NTs intermediate layer, and then placed in a muffle furnace for calcination to form the Ce-Sb co-doped SnO2 active layer. After cooling to room temperature with the furnace, the TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode is obtained.

4. The method for preparing a TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode according to claim 3, characterized in that, In step S1, the ethylene glycol electrolyte contains 0.1-1.5wt% NH4F and 1-5vol% H2O; during the oxidation process, anodic oxidation is carried out for 1-3 hours under a constant voltage of 40-60V.

5. The method for preparing a TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode according to claim 3, characterized in that, In step S2, during the cathode electrolytic reduction process, the anode is a Pt mesh, and the cathode reduction electrolyte consists of 0.5-2M (NH4)2SO4 and composition.

6. The method for preparing a TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode according to claim 3, characterized in that, In step S2, during the cathode electrolytic reduction process, the current density is 10-30 mA / cm². 2 The electrolysis time is 1-3 hours.

7. The method for preparing a TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode according to claim 3, characterized in that, In step S3, during the preparation of the precursor solution, the Sn-containing compound, the Sb-containing compound, and the Ce-containing compound are dissolved in an organic solvent, and a complexing agent is added and stirred until a uniform and transparent precursor solution is formed; wherein, the molar ratio of Sn, Ce and Sb is (8-9.4):(0.5-1.5):(0.1-0.5).

8. The method for preparing a TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode according to claim 3, characterized in that, In step S3, during the sol and gel process, the precursor solution is placed in a constant temperature water bath environment of 30℃-60℃ and stirred for 2 h-6 h to form a sol. The sol is then placed in a sealed container and aged at room temperature for 12 h-24 h to form a gel.

9. The method for preparing a TiO2-NTs / Ti4O7-NTs / Ce-Sb-SnO2 composite electrode according to claim 3, characterized in that, In step S3, during the coating process, the coating is repeated 5-10 times using the dip-coating method or spin coating method, and after each coating, it is placed in an oven at 60℃-120℃ to dry for 0.5 h-2 h. During the calcination process, the heating temperature is 450℃-550℃, and the holding time is 1h-3h.

10. The application of the composite electrode according to claim 1 or the composite electrode prepared according to claim 3 in the degradation of saline organic wastewater.

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