A nickel-doped cobalt-titanium-based electrode material for chlorine evolution reaction and a preparation method and application thereof

Abstract

This invention relates to the field of electrochemical water softening technology, and particularly to a nickel-doped cobalt tetroxide-based electrode material for chlorine evolution reaction, its preparation method, and its application. The preparation method includes the following steps: S1, providing a titanium substrate; S2, coating the surface of the titanium substrate with a precursor solution containing a cobalt source and a nickel source to form a wet film; S3, sequentially drying, calcining, and cooling the wet film to form a single-layer coating; S4, repeating steps S2 and S3 to cyclically build new coating layers on the single-layer coating until a multi-layer coating structure is formed; S5, annealing and cooling the titanium substrate with the multi-layer coating structure to obtain the nickel-doped cobalt tetroxide-based electrode material. Compared with existing technologies, this invention constructs a thick-film, non-reducing agent-treated multi-layer nickel-doped cobalt tetroxide coating, which has advantages such as simple preparation method, high selectivity for chlorine evolution reaction, and low reaction resistance, effectively improving the chloride ion removal efficiency during electrolytic softening.

Description

Technical Field

[0001] This invention relates to the field of electrochemical water softening technology, and in particular to a nickel-doped cobalt tetroxide-based electrode material for chlorine evolution reaction, its preparation method, and its application. Background Technology

[0002] Cleaner production and sustainable development are the core orientations of modern industrial system transformation. As a key link in ensuring the stable operation of the production process, the green and efficient treatment technology of industrial circulating cooling water systems is crucial. Increasing the concentration ratio (N) of the circulating water system is a core approach to water conservation and emission reduction; the higher the concentration ratio, the less water is needed for system makeup, and the more significant the water resource utilization efficiency. However, with the increase of the concentration ratio, corrosive ions in the water (such as Cl-) increase... - ), scale-forming ions (such as Ca) 2+ Mg 2+ HCO3 - As water and nutrients accumulate, the risk of metal corrosion, system scaling, and microbial growth will increase, leading to a decrease in heat exchange efficiency and threatening operational safety. This constitutes a prominent contradiction between "water-saving benefits" and "system operational stability".

[0003] To address issues such as corrosion, scaling, and microbial growth in highly concentrated circulating water, chemical treatment methods, including the addition of scale inhibitors, corrosion inhibitors, and bactericides, are widely used. However, these methods suffer from limited treatment efficiency and secondary water pollution caused by chemical residues, contradicting the demands of green and low-carbon development. Therefore, there is an urgent need to develop new, efficient, and environmentally friendly circulating water treatment technologies.

[0004] Electrochemical water softening technology boasts advantages such as low energy consumption and no need for continuous chemical addition. Through electrolysis, a strongly alkaline environment is created in the cathode region to remove hardness ions, while a strong oxidizing substance with antibacterial properties is generated in the anode region. This achieves scale control, corrosion protection, and sterilization, mitigating the risk of secondary pollution in circulating cooling water treatment at its source. It is a promising circulating cooling water treatment technology. The chlorine evolution reaction (CER) occurring on the anode surface is crucial for regulating the chloride ion content in the water. - Concentration is key to achieving sterilization; it utilizes an anodic reaction to remove Cl from the water. - It is oxidized to Cl2, and then converted to hypochlorite (ClO). - Strong oxidizing substances such as hypochlorous acid (HClO) can damage microbial cell membranes and inhibit biological reproduction, as well as affect the growth of oxide films on metal surfaces and alleviate the effects of Cl. -Corrosion of stainless steel. Current research on electrochemical water softening mainly focuses on cathode modification or electrolytic cell optimization to improve hardness removal efficiency, while research on CER-promoting, especially high-performance CER catalytic anode materials, remains relatively insufficient. The catalytic efficiency and selectivity of CER are highly dependent on the anode catalytic material. Currently, research on electrochemical softening commonly uses titanium anodes coated with metal oxides such as RuO2 or IrO2. Although these electrodes have good stability, they contain Cl... - Limited conversion efficiency and high cost are problems. Therefore, developing novel anode materials that combine high activity, high selectivity, and low cost is of great significance.

[0005] Patent publication number CN105332003A discloses an ultrathin nanosheet array electrocatalytic material with a nanoporous structure and oxygen vacancies. This material consists of a primary array of cobalt tetroxide nanosheets doped with metals, grown perpendicular to a conductive substrate. Each primary nanosheet contains an ultrathin nanosheet with oxygen vacancies and nanoporous structure. The conductive substrate is a titanium sheet or a nickel foam sheet, and the doping metal is zinc, nickel, or manganese, with a molar ratio of the doping metal to cobalt of 0.2-0.5:1. The thickness of the metal-doped cobalt tetroxide ultrathin nanosheets is 1.22 nm, and the nanosheets possess a three-dimensional porous structure with nanopore sizes of 3-6 nm. This material has been shown to exhibit extremely low overpotentials and high conversion frequencies for the oxygen evolution reaction (OER). However, the OER and the chlorine evolution reaction (CER) have fundamentally different requirements for the catalyst's structure and surface chemistry. Specifically, OER typically occurs under strongly alkaline conditions, requiring the catalyst to possess abundant oxygen vacancies to adsorb OH-. - Furthermore, the ultrathin structure facilitates mass transfer and bubble desorption; while CER is carried out in a neutral / weakly alkaline chlorine-containing system, requiring a catalyst that is resistant to Cl. - It has a specific adsorption capacity, and oxygen vacancies may actually become OH groups. - Competing adsorption sites for Cl are unfavorable. - The oxygen vacancy exhibits specific oxidation characteristics. Therefore, while the ultrathin oxygen-rich vacancy nanoarray electrode disclosed in CN105332003A can serve as an excellent OER catalyst, its technical approach is entirely unsuitable for direct application in CER. Oxygen vacancies preferentially adsorb OH groups in chlorine-containing systems. - This leads to the oxygen evolution side reaction becoming dominant, resulting in extremely low chlorine evolution Faraday efficiency; ultrathin nanosheets with a thickness of only 1.22 nm are suitable for use in highly oxidizing, high-Cl environments. - Under anodic polarization conditions, lattice oxygen readily participates in the reaction and rapidly dissolves and detaches.

[0006] Currently, there are no reports on nickel-doped cobalt tetroxide-based anode materials specifically designed for reverse engineering under CER conditions. This invention, based on the understanding of the aforementioned technical contradictions, proposes a material design strategy that is completely reverse-engineered from existing OER catalysts. Summary of the Invention

[0007] The purpose of this invention is to overcome the defect of poor selectivity of cobalt tetroxide-based electrode materials in the chlorine evolution reaction in the prior art, and to provide a nickel-doped cobalt tetroxide-based electrode material for the chlorine evolution reaction, its preparation method and application, which exhibits high chlorine evolution activity in chlorine-containing systems.

[0008] The objective of this invention can be achieved through the following technical solutions: One of the technical solutions of the present invention is to provide a method for preparing a nickel-doped cobalt tetroxide-based electrode material for chlorine evolution reaction, comprising the following steps: S1, Provides a titanium substrate; S2. A precursor solution containing a cobalt source and a nickel source is coated on the surface of the titanium substrate to form a wet film; S3. The wet film is sequentially dried, calcined, and cooled to form a single-layer coating layer; S4. Repeat steps S2 and S3 to build new coating layers on the single-layer coating layer in a cyclic manner until a multi-layer coating layer structure is formed. S5. Anneal and cool the titanium substrate with the multilayer coating structure to obtain the nickel-doped cobalt tetroxide titanium-based electrode material.

[0009] Furthermore, in step S1, the titanium substrate undergoes pretreatment of grinding, degreasing, and pickling in sequence before use; The pickling process involves etching in an acid solution for 80-100 minutes, preferably 85-95 minutes; the acid solution is hydrochloric acid; the mass concentration is 15%-25%, preferably 18%-22%; the etching temperature is 60-95℃, preferably 80-92℃. The degreasing process involves immersing the sample in an acetone solution and then sonicating it.

[0010] Further, in step S2, the cobalt source is cobalt nitrate or cobalt chloride, the nickel source is nickel nitrate, and the solvent of the precursor solution is n-butanol or isopropanol.

[0011] Further, in step S2, the molar ratio of cobalt in the cobalt source to nickel in the nickel source is 5~30:1, preferably 10~20:1. If the molar ratio is too small, nickel cannot effectively regulate the crystal structure; if the molar ratio is too large, it will affect the catalytic effect of cobalt tetroxide. The concentration of the cobalt source in the precursor solution is 0.001~0.01 mol / L.

[0012] Further, in step S3, the drying temperature is 100~110℃, preferably 103~106℃; the drying time is 5~20min, preferably 8~15min; The calcination temperature is 300~500℃, preferably 300~400℃; the calcination time is 5~20min, preferably 8~15min; The temperature after cooling is room temperature.

[0013] Furthermore, in step S3, the multilayer coating structure has 5 to 20 coating layers, preferably 8 to 15 layers. Repeated coating can gradually reduce the thermal stress between the coating layer and the titanium substrate, making the adhesion of the coating layer stronger. Fewer coating times cannot guarantee an effective coating thickness; increasing the number of coating times increases the corresponding cost.

[0014] Furthermore, the thickness of each coating layer is 0.2~5.0µm, preferably 1.0~2.5µm. Furthermore, the annealing temperature is 300~500℃, preferably 300~400℃; the annealing time is 50~250min, preferably 150~200min.

[0015] The second technical solution of the present invention is to provide a nickel-doped cobalt tetroxide-based electrode material for chlorine evolution reaction, which is prepared by the preparation method described above.

[0016] Furthermore, the electrode material comprises a titanium substrate and a multilayer coating structure supported on its surface. The multilayer coating structure has several coating layers, each being nickel-doped cobalt tetroxide. The overall thickness of the multilayer coating structure is on the micrometer scale, and its surface exhibits a porous morphology composed of stacked nanoparticles. The charge transfer resistance of the nickel-doped cobalt tetroxide electrode is significantly lower than that of the undoped cobalt tetroxide electrode.

[0017] The third technical solution of the present invention is to provide an application of a nickel-doped cobalt tetroxide titanium-based electrode material for chlorine evolution reaction as an anode in the field of electrochemical soft water treatment technology.

[0018] Compared with the prior art, the present invention has the following advantages: (1) High chlorine evolution selectivity. Co is induced by nickel doping. 3+ / Co 2+ with Ni 2+ / Ni 3+ Dynamic electron transfer between Co 3+ + Ni 2+ ⇔Co 2+ + Ni 3+ ), Co 3+ Site-specific adsorption of Cl - Formation of Co-Cl + intermediate, Co 2+This accelerates the desorption of electrons from the intermediate, thus significantly lowering the activation energy of the CER reaction. Simultaneously, by deliberately avoiding the introduction of oxygen vacancies, OH... - Adsorption was effectively suppressed, the relative contribution of the oxygen evolution reaction pathway was significantly reduced, and the chlorine evolution reaction occupied a more favorable competitive position in the anodic process. Figure 4 The results show that the electrode of this invention achieves 10 mA / cm² in a chlorine-containing system. 2 The required potential is 510 mV lower than that of the chlorine-free system, while the electrode in the comparative paper does not exhibit similar selectivity under these conditions.

[0019] (2) Excellent charge transfer kinetics. The synergistic effect of nickel doping and multilayer thick film structure improves the charge transfer resistance (Rt). ct ) 243.7 Ω·cm without cobalt tetroxide 2 Reduced to 3.55 Ω·cm 2 ( Figure 6 This provides a strong driving force for the chlorine evolution reaction.

[0020] (3) Excellent anodic stability. The multilayer coating structure eliminates the through-thickness defects of a single-layer coating, and the thick film barrier layer effectively prevents the electrolyte from penetrating into the titanium substrate. Compared with the ultrathin nanosheet array with a thickness of only 1.22 nm in CN105332003A, the micron-scale thick film coating of this invention has significantly higher structural stability and corrosion resistance in a strongly oxidizing chlorine-containing environment.

[0021] (4) The preparation process is simple and environmentally friendly. No hydrothermal reactor or strong reducing agent treatment is required. It can be achieved simply by conventional coating-thermal decomposition, which is low in cost and easy to scale up. Attached Figure Description

[0022] Figure 1 Comparison of SEM surface morphology of Ti / Ni-Co3O4 electrode (a) and Ti / Co3O4 electrode (b); Figure 2 Linear sweep voltammetry (LSV) curves of Ti / Ni-Co3O4 electrodes with different cobalt-nickel molar ratios in simulated cooling water. Figure 3 LSV curves of Ti / Ni-Co3O4 electrodes (cobalt-nickel molar ratio 15:1) at different thermal decomposition temperatures; Figure 4 LSV curves of Ti / Ni-Co3O4 electrode and Ti / Co3O4 electrode in simulated cooling water containing and without chlorine; Figure 5 Comparison of LSV curves for Ti / Ni-Co3O4 electrode (Example 1), Ti / Co3O4 electrode (Comparative Example 1) and commercial Ti / RuO2 electrode; Figure 6 Electrochemical impedance spectroscopy (EIS) of Ti / Ni-Co3O4 electrode (Example 1), Ti / Co3O4 electrode (Comparative Example 1), and commercial Ti / RuO2 electrode: (a) Nyquist plot; (b) magnified view; (c) equivalent circuit diagram. Figure 7 Cl- in cooling water after constant voltage electrolysis of Ti / Ni-Co3O4 electrode (Example 1) and Ti / Co3O4 electrode (Comparative Example 1) for different times - Removal rate comparison; Figure 8 A comparison of the Faraday efficiency of Ti / Ni-Co3O4 electrode (Example 1) and Ti / Co3O4 electrode (Comparative Example 1) in constant voltage electrolysis in cooling water for 1 hour; Figure 9 Linear sweep voltammetry (LSV) curves of multilayer coated Ti / Ni-Co3O4 electrode (Example 1) and single-layer coated Ti / Ni-Co3O4 electrode (Comparative Example 2) in simulated cooling water. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. All other embodiments obtained by those skilled in the art based on the given embodiments without creative effort are within the scope of protection of this application.

[0024] Unless otherwise specified, the reagents, methods, instruments and equipment used in this invention are conventional reagents, methods, instruments and equipment in the art.

[0025] In the following embodiments, the titanium sheet has a size of 50 mm × 25 mm × 2 mm, is manufactured by Shanghai Luosong Electromechanical Equipment Co., Ltd., and has a model number of TA1; the Ti / RuO2 electrode can be a commercially available ruthenium-iridium-titanium mixed oxide coated electrode, which can be purchased through commercial channels.

[0026] A method for preparing a nickel-doped cobalt tetroxide-based electrode material for chlorine evolution reaction includes the following steps: S1, Provides a titanium substrate; S2. A precursor solution containing a cobalt source and a nickel source is coated on the surface of the titanium substrate to form a wet film; S3. The wet film is sequentially dried, calcined, and cooled to form a single-layer coating layer; S4. Repeat steps S2 and S3 to build new coating layers on the single-layer coating layer in a cyclic manner until a multi-layer coating layer structure is formed. S5. Anneal and cool the titanium substrate with the multilayer coating structure to obtain the nickel-doped cobalt tetroxide titanium-based electrode material.

[0027] In some specific embodiments, in step S1, the titanium substrate undergoes pretreatment of grinding, degreasing and pickling in sequence before use; The pickling process involves etching in an acid solution for 80-100 minutes, preferably 85-95 minutes; the acid solution is hydrochloric acid; the mass concentration is 15%-25%, preferably 18%-22%; the etching temperature is 60-95℃, preferably 80-92℃. The degreasing process involves immersing the sample in an acetone solution and then sonicating it.

[0028] In some specific embodiments, in step S2, the cobalt source is cobalt nitrate or cobalt chloride, the nickel source is nickel nitrate, and the solvent of the precursor solution is n-butanol or isopropanol.

[0029] In some specific embodiments, in step S2, the molar ratio of cobalt in the cobalt source to nickel in the nickel source is 5~30:1, preferably 10~20:1. If the molar ratio is too small, nickel cannot effectively regulate the crystal structure; if the molar ratio is too large, it will affect the catalytic effect of cobalt tetroxide. The concentration of the cobalt source in the precursor solution is 0.001~0.01 mol / L.

[0030] In some specific embodiments, in step S3, the drying temperature is 100~110℃, preferably 103~106℃; the drying time is 5~20min, preferably 8~15min. The calcination temperature is 300~500℃, preferably 300~400℃; the calcination time is 5~20min, preferably 8~15min; The temperature after cooling is room temperature.

[0031] In some specific embodiments, in step S3, the multilayer coating structure locally comprises 5 to 20 coating layers, preferably 8 to 15 layers. Repeated coating can gradually reduce the thermal stress between the coating layer and the titanium substrate, resulting in stronger adhesion of the coating layer. Fewer coating layers cannot guarantee an effective coating thickness; increasing the number of coating layers increases the corresponding cost.

[0032] In some specific embodiments, the thickness of each coating layer is 0.2~5.0µm, preferably 1.0~2.5µm. In some specific embodiments, the annealing temperature is 300~500℃, preferably 300~400℃; the annealing time is 50~250min, preferably 150~200min.

[0033] A nickel-doped cobalt tetroxide-based electrode material for chlorine evolution reaction is prepared using the method described above.

[0034] In some specific embodiments, the electrode material includes a titanium substrate and a multilayer coating structure supported on its surface. The multilayer coating structure has several coating layers, which are nickel-doped cobalt tetroxide. The overall thickness of the multilayer coating structure is on the micrometer scale, and the surface exhibits a porous morphology composed of stacked nanoparticles. The charge transfer resistance of the nickel-doped cobalt tetroxide electrode is significantly lower than that of the undoped cobalt tetroxide electrode.

[0035] Application of a nickel-doped cobalt tetroxide-based electrode material for chlorine evolution reaction as an anode in the field of electrochemical soft water treatment technology.

[0036] Each of the above embodiments can be implemented individually or in any combination of two or more.

[0037] The following description uses specific examples to illustrate the point.

[0038] Example 1 A method for preparing a nickel-doped cobalt tetroxide-based electrode material for chlorine evolution reaction includes the following steps: (1) Provide a titanium substrate A titanium sheet with dimensions of 50 mm × 25 mm × 2 mm was used as the titanium substrate. The surface of the titanium sheet was progressively sanded with sandpaper, followed by rinsing with deionized water. It was then immersed in acetone solution for ultrasonic degreasing for 30 minutes, and rinsed with deionized water again. Finally, it was subjected to acid etching in 20% hydrochloric acid at 90°C for 90 minutes, and then rinsed with deionized water to obtain the titanium substrate. The titanium substrate was stored in ethanol.

[0039] (2) Formation of a wet film 0.392 g Co(NO3)2‧6H2O and 0.044 g Ni(NO3)2‧6H2O (cobalt-nickel molar ratio of 15:1) were dissolved in 5 mL n-butanol and stirred until homogeneous to obtain a precursor solution containing cobalt and nickel sources. The precursor solution was uniformly coated onto the titanium substrate from step (1) to a thickness of 1.0~2.5 µm to form a wet film.

[0040] (3) Forming a single-layer coating The wet film is first dried in an oven at 105°C for 10 min, then transferred to a muffle furnace at 350°C for 10 min, and cooled to room temperature to form a single-layer coating.

[0041] (4) Forming a multi-layer coating structure Repeat steps (2) and (3) 10 times to build new coating layers on the single coating layer until a multi-layer coating structure is formed.

[0042] (5) Obtaining nickel-doped cobalt tetroxide titanium-based electrode material The titanium substrate with the multilayer coating structure was annealed in a muffle furnace at 350°C for 3 hours and then cooled to room temperature in the furnace to obtain the nickel-doped cobalt tetroxide titanium-based (Ti / Ni-Co3O4) electrode material.

[0043] Example 2 In step (2), the amount of Ni(NO3)2‧6H2O was adjusted to 0.131g, the amount of cobalt source remained unchanged (cobalt-nickel molar ratio was 5:1), and the other conditions were the same as in Example 1.

[0044] Example 3 In step (2), the amount of Ni(NO3)2‧6H2O was adjusted to 0.022g, the amount of cobalt source remained unchanged (cobalt-nickel molar ratio was 30:1), and the other conditions were the same as in Example 1. Example 4 In step (5), the calcination temperature is adjusted to 300℃, and the other conditions are the same as in Example 1.

[0045] Example 5 In step (5), the calcination temperature is adjusted to 400℃, and the other conditions are the same as in Example 1.

[0046] Example 6 In step (5), the calcination temperature is adjusted to 450℃, and the other conditions are the same as in Example 1.

[0047] Example 7 In step (5), the calcination temperature is adjusted to 500℃, and the other conditions are the same as in Example 1.

[0048] Comparative Example 1 The two examples are largely the same as in Example 1, except for step (2) forming a wet film: 0.436 g of Co(NO3)2 was dissolved in 5 mL of n-butanol (without nickel doping), and stirred until homogeneous to obtain a precursor solution containing a cobalt source. The precursor solution was uniformly coated onto the titanium substrate from step (1) to a thickness of 1.0~2.5 µm to form a wet film. Finally, a Ti / Co3O4 electrode was obtained.

[0049] Comparative Example 2 Only one coating-calcination process was performed, with a coating thickness of approximately 1–2 μm. Steps S2 and S3 were not repeated, resulting in only a single-layer coating. All other conditions were the same as in Example 1. During the enhanced lifetime test, this electrode failed due to passivation caused by easy penetration of the coating by the electrolyte, demonstrating that a multilayered accumulation structure is indispensable for long-term stability under CER conditions.

[0050] Performance testing (1) Surface morphology test Figure 1 The SEM surface morphology comparison shows the Ti / Ni-Co3O4 electrode (a) of Example 1 and the Ti / Co3O4 electrode (b) of Comparative Example 1. The Ti / Ni-Co3O4 electrode exhibits a porous morphology composed of nanoparticles, which effectively increases the contact area between the electrode and the electrolyte and shortens the mass transfer path, providing more active sites for CER. The Ti / Co3O4 electrode, however, exhibits a denser structure with a few cracks. During heat treatment, the Co3O4 grains generated from the precursor decomposition in the nickel-free coating grow along the thermodynamically optimal path, forming a dense structure. Simultaneously, rapid solvent evaporation and uneven distribution of thermal stress lead to cracks on the coating surface. 2+ The solid solution formed by incorporating Co3O4 lattice reduces the relative surface energy of the crystal planes, promoting the preferential growth of ultrathin nanosheets. These nanosheets form through-holes through interlayer stacking during thermal decomposition and self-assembly, thus exhibiting a porous structure.

[0051] (2) Electrochemical performance testing An electrochemical workstation was used, with the Ti / Ni-Co3O4 electrode prepared in Example 1, the Ti / Co3O4 electrode in Comparative Example 1, and the commercial Ti / RuO2 electrode as working electrodes, a saturated calomel electrode as the reference electrode, and a platinum electrode as the auxiliary electrode. All three electrodes were placed in the test solution. Linear sweep voltammetry was performed using the electrochemical workstation. Electrochemical impedance spectroscopy was also performed using the electrochemical workstation.

[0052] The electrode electrochemical performance test solutions used chlorine-containing simulated cooling water and chlorine-free simulated cooling water. The chlorine-containing simulated cooling water had the following composition: CaCl2 concentration of 3 mmol / L, MgCl2 concentration of 2 mmol / L, NaHCO3 concentration of 6 mmol / L, and Na2SO4 concentration of 3.5 mmol / L. The chlorine-free simulated cooling water had the following composition: CaSO4 concentration of 3 mmol / L, MgSO4 concentration of 2 mmol / L, NaHCO3 concentration of 6 mmol / L, and Na2SO4 concentration of 3.5 mmol / L.

[0053] Linear scan voltammetry was performed at a scan rate of 5 mV / s between 0 V and 2.5 V. Electrochemical impedance spectroscopy was performed at a frequency range of 10 mV / s. 5 ~10 -2 The frequency was Hz, and the amplitude was 10 mV. The charge transfer resistance was obtained by fitting the electrochemical impedance spectroscopy, and the resistance to the electrochemical reaction was analyzed.

[0054] Figure 2Linear sweep voltammetry (LSV) curves of Ti / Ni-Co3O4 electrodes and Ti / Co3O4 electrodes (Examples 1-3 and Comparative Example 1) with different cobalt-nickel molar ratios in chlorinated simulated cooling water show that nickel doping significantly improves CER activity, with a cobalt-nickel ratio of 15:1 being optimal. The electrode with a cobalt-nickel molar ratio of 5:1 exhibits slightly lower CER activity than the 15:1 sample, but is still significantly better than the undoped electrode. The electrode with a cobalt-nickel molar ratio of 30:1 still shows better activity than the undoped electrode, but the electronic modulation effect is slightly weaker at lower nickel contents.

[0055] Figure 3 The LSV curves of Ti / Ni-Co3O4 electrodes (cobalt-nickel molar ratio 15:1) at different thermal decomposition temperatures (300~500℃, Examples 1, 4~7) in chlorine-containing simulated cooling water show that 350℃ is the optimal calcination temperature. When the thermal decomposition temperature is too low, the precursor decomposes incompletely, the Co3O4 crystal structure is incomplete, and Ni ions are difficult to fully incorporate into the lattice. When the temperature is too high, the difference in thermal expansion coefficients between the catalyst layer and the titanium substrate increases, leading to a decrease in bonding strength and charge transfer efficiency.

[0056] Figure 4 LSV curves of Ti / Ni-Co3O4 electrode (Example 1), Ti / Co3O4 electrode (Comparative Example 1) and commercial Ti / RuO2 electrode are compared. Figure 4 The results show that the Ti / Ni-Co3O4 electrode of this invention achieves 10 mA / cm² in chlorine-containing simulated cooling water. 2 The potential (2.11 V) is 510 mV lower than that in simulated cooling water without chlorine (2.62 V). More importantly, at the same anode potential (e.g., 2.3 V), the anodic current density of the Ti / Ni-Co3O4 electrode of this invention is 9.4 times that of the Ti / Co3O4 electrode. This significant difference directly demonstrates the effectiveness of the electrode of this invention in resisting Cl-. - Oxidation exhibits a highly specific response, with surface reactions dominated by CER. In contrast, the CN105332003A electrode, due to its abundance of oxygen vacancies, will still preferentially undergo OER in chlorine-containing systems, thus failing to achieve highly selective CER.

[0057] Figure 5 LSV curves of Ti / Ni-Co3O4 electrode (Example 1), Ti / Co3O4 electrode (Comparative Example 1) and commercial Ti / RuO2 electrode are compared. Figure 5 In (a), the anodic reaction current density of Ti / Ni-Co3O4, Ti / Co3O4 and Ti / RuO2 electrodes reaches 10 mV / cm. 2The required potentials were 2.11V, 2.35V, and 2.58V, respectively, indicating that the introduction of Ni into Co3O4 effectively enhances its CER catalytic activity. Furthermore, the Tafel slope can be used to analyze electrode reaction resistance; a smaller Tafel slope indicates lower electrode reaction resistance, which is more conducive to accelerating the reaction rate. Figure 5 (b) It can be seen that the Tafel slope of the Ti / Ni-Co3O4 anodic reaction is 701.4 mV / dec, which is lower than that of Ti / Co3O4 (881.2 mV / dec) and Ti / RuO2 electrode (1501.5 mV / dec). This indicates that the Ti / Ni-Co3O4 electrode surface has the least resistance to the anodic reaction, and the anodic reaction is easier to carry out.

[0058] Figure 6 Electrochemical impedance spectroscopy (EIS) spectra of a Ti / Ni-Co3O4 electrode (Example 1), a Ti / Co3O4 electrode (Comparative Example 1), and a commercial Ti / RuO2 electrode are shown. (a) Nyquist plot; (b) magnified view; (c) equivalent circuit diagram. EIS fitting results show that the charge transfer resistance (R) of the Ti / Ni-Co3O4 electrode of this invention is [missing information]. ct = 3.55 Ω·cm 2 The efficiency is much lower than that of the Ti / Co3O4 electrode (243.7 Ω·cm). 2 ) and commercial Ti / RuO2 electrode (55.39 Ω·cm) 2 This order-of-magnitude reduction is due to nickel doping optimizing the electronic structure of Co3O4; the multilayer thermal decomposition process forms a continuous and dense conductive network. This extremely low charge transfer resistance is the key to the high current density CER driven by the electrode of this invention at low overpotential, and it is also difficult to achieve by the ultrathin array electrode in the prior art CN105332003A. (3) Electrolytic softening treatment The Ti / Ni-Co3O4 electrode prepared in Example 1 and the Ti / Co3O4 electrode prepared in Comparative Example 1 were used as anodes, 304 stainless steel plate electrodes were used as cathodes, and the electrolysis voltage was 11V to perform electrolytic softening treatment of chlorine-containing simulated cooling water. The composition of the chlorine-containing simulated cooling water was the same as above.

[0059] Figure 7 Cl- in cooling water after constant voltage electrolysis of Ti / Ni-Co3O4 electrode (Example 1) and Ti / Co3O4 electrode (Comparative Example 1) for different times - Removal rate comparison; Figure 8 A comparison of the Faraday efficiency of Ti / Ni-Co3O4 electrode (Example 1) and Ti / Co3O4 electrode (Comparative Example 1) in constant voltage electrolysis in cooling water for 1 hour. Figure 7 and Figure 8 This indicates that after electrolysis at constant voltage for 60 min, the Cl in the electrode of this invention... -The removal rate reached 28.0%, and the Faraday efficiency was 35.9%, both significantly better than those of the Ti / Co3O4 electrode (12.3% and 22.2%, respectively). This result confirms the advantages of the oxygen-free vacancy thick film anode for CER in chlorinated water environments: it maintains high catalytic activity while avoiding rapid deactivation caused by lattice oxygen participation in the reaction.

[0060] Figure 9 Linear sweep voltammetry (LSV) curves of multilayer coated Ti / Ni-Co3O4 electrode (Example 1) and single-layer coated Ti / Ni-Co3O4 electrode (Comparative Example 2) in simulated cooling water. Figure 9 This indicates that the multilayer coated Ti / Ni-Co3O4 electrode of the present invention achieves 10 mA / cm² in chlorine-containing simulated cooling water. 2 The potential (2.11 V) is 1.02 V lower than that of the monolayer coated Ti / Ni-Co3O4 electrode. This difference indicates that the multilayer coated Ti / Ni-Co3O4 electrode provides more active sites and a faster reaction rate, thus achieving a potential of 10 mA / cm at a lower potential. 2 The anodic reaction current density. Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, some modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention are within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a nickel-doped cobalt tetroxide-based electrode material for chlorine evolution reaction, characterized in that, Includes the following steps: S1, Provides a titanium substrate; S2. A precursor solution containing a cobalt source and a nickel source is coated on the surface of the titanium substrate to form a wet film; S3. The wet film is sequentially dried, calcined, and cooled to form a single-layer coating layer; S4. Repeat steps S2 and S3 to build new coating layers on the single-layer coating layer in a cyclic manner until a multi-layer coating layer structure is formed. S5. Anneal and cool the titanium substrate with the multilayer coating structure to obtain the nickel-doped cobalt tetroxide titanium-based electrode material.

2. The method for preparing a nickel-doped cobalt tetroxide-based electrode material for chlorine evolution reaction according to claim 1, characterized in that, In step S1, the titanium substrate undergoes pretreatment of grinding, degreasing, and pickling in sequence before use; The pickling process involves etching in an acid solution for 80-100 minutes. The acid solution is hydrochloric acid with a mass concentration of 15%-25%, and the etching temperature is 60-95℃.

3. The method for preparing a nickel-doped cobalt tetroxide-based electrode material for chlorine evolution reaction according to claim 1, characterized in that, In step S2, the cobalt source is cobalt nitrate or cobalt chloride, the nickel source is nickel nitrate, and the solvent of the precursor solution is n-butanol or isopropanol.

4. The method for preparing a nickel-doped cobalt tetroxide-based electrode material for chlorine evolution reaction according to claim 1, characterized in that, In step S2, the molar ratio of cobalt in the cobalt source to nickel in the nickel source is 5~30:1, and the concentration of the cobalt source in the precursor solution is 0.001~0.01mol / L.

5. The method for preparing a nickel-doped cobalt tetroxide-based electrode material for chlorine evolution reaction according to claim 1, characterized in that, In step S3, the drying temperature is 100~110℃, and the drying time is 5~20min; The calcination temperature is 300~500℃, and the calcination time is 5~20min; The temperature after cooling is room temperature.

6. The method for preparing a nickel-doped cobalt tetroxide-based electrode material for chlorine evolution reaction according to claim 1, characterized in that, In step S3, the multilayer coating structure has 5 to 20 coating layers.

7. The method for preparing a nickel-doped cobalt tetroxide-based electrode material for chlorine evolution reaction according to claim 1, characterized in that, The annealing temperature is 300~500℃, and the annealing time is 50~250min.

8. A nickel-doped cobalt tetroxide-based electrode material for chlorine evolution reaction, which is prepared by any one of the preparation methods described in claims 1 to 7.

9. The nickel-doped cobalt tetroxide-based electrode material for chlorine evolution reaction according to claim 8, characterized in that, The electrode material includes a titanium substrate and a multilayer coating structure supported on its surface. The multilayer coating structure has several coating layers, which are nickel-doped cobalt tetroxide. The overall thickness of the multilayer coating structure is on the micrometer scale, and the surface exhibits a porous morphology composed of stacked nanoparticles.

10. The application of the nickel-doped cobalt tetroxide-based electrode material for chlorine evolution reaction as described in claim 8 as an anode in the field of electrochemical soft water treatment technology.

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