An ultra-stable high-entropy metal oxide electrode for alternating reverse polarity

Abstract

The application belongs to the field of electrochemical water treatment, and particularly relates to an ultra-stable high-entropy metal oxide electrode with a breakthrough design, which is particularly suitable for application in an alternating current reverse electrode environment. By carefully adjusting the proportions of various metal elements and adopting high-energy laser direct energy deposition, plasma and ceramicization processes, a high-entropy oxide material with complex chemical composition and highly stable structure is formed. The electrode exhibits excellent electrochemical stability and corrosion resistance in an alternating current field, can be stably operated for a long time under the condition of frequent polarity reversal, effectively prevents the occurrence of cathode fouling, and ensures that the electrocatalytic performance does not obviously decay. The unique structural design provides a high-performance and long-life electrode material solution for the field of water pollution control, especially for the treatment of high-hardness and high-salinity industrial wastewater.

Description

I. Technical Field

[0001] This invention relates to the field of environmental pollution control technology, specifically to an ultra-stable, high-entropy metal oxide electrode that can be used for alternating current reversal. Given that cathode scaling on electrocatalytic electrodes severely restricts the application of electrocatalysis in the treatment of high-salt, high-hardness wastewater, electrocatalytic electrodes capable of frequent reversal are of great significance in the industrial application of electrocatalysis technology. II. Background Technology

[0002] High-salinity wastewater originates from a wide range of sources, primarily including the chemical, pharmaceutical, printing and dyeing, seawater desalination, and food processing industries. Its production volume is enormous and continues to rise with industrial development. High-salinity wastewater is characterized by its high content of inorganic salts, such as sodium chloride and sodium sulfate, and may also contain various organic compounds and heavy metals. Its salinity is typically above 3.5%, or even higher. High-salinity wastewater poses serious environmental hazards. Direct discharge leads to soil salinization, affecting vegetation growth and crop yields; after entering water bodies, it increases salinity, disrupting the balance of aquatic ecosystems and impacting the survival and reproduction of aquatic organisms. Furthermore, the organic matter and heavy metals in high-salinity wastewater may accumulate in the environment and be transferred through the food chain, posing a potential threat to human health. The treatment of high-salinity wastewater is challenging and represents one of the major challenges currently facing environmental protection.

[0003] In the field of advanced treatment of high-salinity wastewater, common treatment technologies include membrane separation, ion exchange, advanced oxidation, and evaporation crystallization. Membrane separation technology can efficiently separate impurities and produce high-quality effluent, but the membrane is susceptible to fouling, requires high-quality influent, and needs regular cleaning and replacement, increasing operating costs. Ion exchange technology can selectively remove specific ions, is simple to operate, and requires little space; however, the resin needs to be regenerated, the regeneration process generates wastewater, and it is easily saturated with high-concentration brine. Advanced oxidation technology can generate strong oxidizing free radicals, effectively removes recalcitrant organic matter, has a fast reaction rate, and produces no secondary pollution; however, it has high operating costs, some oxidants are unstable, and it requires strict reaction conditions. Evaporation crystallization technology can achieve salt recovery and zero wastewater discharge, with stable treatment results suitable for high-salinity wastewater; however, it has high energy consumption, large equipment investment, and the crystallized products need further treatment to avoid secondary pollution.

[0004] Electrocatalysis has wide applications in the advanced treatment of high-salinity wastewater. Its main advantages lie in its mild reaction conditions, simple operation, and efficient removal of organic matter and some heavy metal ions from wastewater. The high salinity of high-salinity wastewater can increase the solution conductivity and reduce the energy consumption of the electrocatalytic process. However, electrocatalysis also has drawbacks in treating high-salinity wastewater, especially when the water hardness is high, leading to scaling at the cathode. The reaction mechanism of cathode scaling mainly involves the combination of calcium and magnesium ions in the water with hydroxide ions on the cathode surface, forming insoluble precipitates such as calcium carbonate and magnesium hydroxide. The chemical composition of the scale layer is mainly calcium carbonate and magnesium hydroxide, and its thickness gradually increases with operating time. Scale layer has many adverse effects on the electrocatalytic process, such as reducing the effective surface area of ​​the electrode, leading to decreased current efficiency; increasing the resistance between electrodes, increasing energy consumption; affecting the stability and lifespan of the electrode, and increasing maintenance costs. Simultaneously, the scale layer may also hinder the contact between pollutants and the electrode surface, reducing the removal efficiency of organic matter and heavy metals.

[0005] Analyzing the current problems in the electrocatalytic deep treatment of high-salinity wastewater highlights the urgent need to develop new technologies to prevent cathode scaling. This will improve the efficiency and stability of electrocatalytic deep treatment of high-salinity wastewater. Reducing cathode scaling can increase electrode current efficiency, lower energy consumption, and ensure the continuous and stable operation of the treatment process. This will help achieve compliant discharge or resource recycling of high-salinity wastewater, promote sustainable industrial development, and protect the ecological environment. Simultaneously, the development of new methods will bring technological innovation to the field of high-salinity wastewater treatment, providing strong support for solving water scarcity and environmental pollution problems. III. Summary of the Invention

[0006] This invention addresses the problems existing in the prior art. Generally, cathode scaling can be mitigated through physical, chemical, and electrochemical methods. For example, optimizing the electrode structure and designing special electrodes can reduce scaling, but this typically increases cost and process complexity; ultrasonic treatment requires additional equipment and has high energy consumption. In chemical methods, adding scale inhibitors such as polyphosphates and organophosphonic acids can form complexes with calcium and magnesium ions to prevent precipitation, but this may introduce new chemical substances that affect wastewater treatment; adjusting pH values ​​also requires careful consideration of its impact on pollutant treatment effectiveness.

[0007] The main principle behind the anode-cathode reversal method to prevent electrochemical scaling is to periodically change the polarity of the electrodes, causing the scale deposited on the cathode to dissolve or transform under the anode polarity, thus preventing continuous scale accumulation. Taking common calcium and magnesium ion scaling as an example, during normal electrocatalysis, the cathode reaction increases the concentration of hydroxide ions in the water. Calcium and magnesium ions combine with hydroxide ions to form calcium carbonate (CaCO3) and magnesium hydroxide (Mg(OH)2) precipitates. The reaction formula is:

[0008] Ca 2 ++2OH-→CaCO3+H2O

[0009] Mg2++2OH-→Mg(OH)2

[0010] When the cathode and anode are reversed, the original cathode becomes the anode, and calcium carbonate and magnesium hydroxide will dissolve through oxidation at the anode. This effectively prevents long-term scale accumulation on the electrode, maintaining electrode performance and the stability of the electrocatalytic process. For example, calcium carbonate may react as follows:

[0011] CaCO3 + 2H+ + →Ca 2 ++CO2+H2O

[0012] However, the current problem is that commonly used commercial anode materials, such as ruthenium-iridium, lead oxide, tin oxide, and nickel oxide, cannot withstand long-term cathode current, which may cause unavoidable damage to the electrode. Therefore, there is an urgent need to develop metal oxide electrodes that can be used for AC reversal and have high stability, high activity, and selectivity.

[0013] To achieve the above objectives, the present invention provides an ultrastable high-entropy metal oxide electrode that can be used for AC reversal, characterized in that the preparation method of the electrode includes the following steps:

[0014] Step 1: The tantalum substrate is subjected to high-precision polishing to achieve a surface roughness of Ra 0.5μm. Then, the polished tantalum substrate is placed in an ultrasonic cleaner and cleaned with acetone for 15 minutes to remove surface oil. Next, it is rinsed with deionized water and then immersed in a 5% dilute hydrochloric acid solution for 15 minutes to remove surface oxides. Finally, it is rinsed with deionized water and dried at 100℃ for 30 minutes.

[0015] Step 2: An ultra-stable corrosion-resistant carbide layer is formed using ion implantation technology. The implanted ions are titanium carbide ions and zirconium carbide ions, the implantation energy is 120 keV, and the implantation dose is 8 × 10⁻⁶. 16 ions cm -2 The injection process is carried out under a vacuum of 1×10⁻⁶. -3 The implantation was carried out in an environment of Pa, with an implantation temperature of 150°C and an implantation time of 10 seconds, to obtain a tantalum substrate with an ultra-stable corrosion-resistant carbide layer.

[0016] Step 3: Select seven elemental metal powders (tantalum, rubidium, gadolinium, dysprosium, chromium, nickel, and cadmium) and mix them in a molar ratio of 120:7:16:22:9:2:1. Place the mixed raw materials into a planetary ball mill for mechanical alloying treatment at a speed of 400 rpm. –1The ball-to-material ratio was 15:1, the ball milling time was 20 hours, and argon gas was introduced during the ball milling process to prevent metal oxidation. The milled powder was then subjected to a vacuum of 1×10⁻⁶. –2 Heat treatment was performed under vacuum at 800℃ for 2 hours to obtain a mixed powder of 7 metals.

[0017] Step 4: Using argon as the carrier gas, inject the mixed powder of the seven metals obtained in Step 3 at a speed of 20 L / min. –1 The nozzle temperature was 1200℃. The laser was progressively scanned onto the tantalum substrate with an ultra-stable, corrosion-resistant carbide layer obtained in step 2 after ion implantation treatment. Simultaneously, high-entropy alloy powder was fused onto the tantalum substrate using high-energy laser direct energy deposition (HEAD) to form a high-entropy alloy surface active layer. The laser power was 15kW, and the scanning speed was 0.5 mm / s. –1 The overlap rate is 40%, and the cladding process is carried out under argon protection. Due to the cyclic heat input and rapid solidification, the deposited high-entropy alloy will produce a gradient grain structure with alternating growth of equiaxed and columnar crystals.

[0018] Step 5: The high-entropy alloy surface active layer obtained in step 4 after laser cladding is subjected to plasma treatment and ceramicization to improve its surface activity and corrosion resistance. The plasma treatment uses a mixture of argon and oxygen, with an oxygen volume fraction of 10%, a treatment power of 300W, a treatment time of 20min, and a treatment temperature of 50℃ to transform the high-entropy alloy layer into a high-entropy ceramic layer.

[0019] Step 6: A nano-titanium dioxide coating is prepared on the high-entropy ceramic layer obtained in Step 5 using the sol-gel method. First, tetrabutyl titanate, ethanol, acetylacetone, and deionized water are mixed in a mass ratio of 8:2:10:1 and stirred until homogeneous to obtain a sol. Then, the electrode is immersed in the sol at a depth of 4 mm / min. –1 After repeated lifting and drying in air, the product is subjected to heat treatment at 450℃ for 2 hours.

[0020] Step 7: Finally, the electrode is modified using ion doping technology to improve its electrocatalytic activity and selectivity. Molybdenum ions are selected for doping at a mass concentration of 3%. The doping method is electrochemical deposition with a deposition voltage of -1.0V. The deposition process is carried out in an electrolyte containing 20% ​​ammonium molybdate at a temperature of 40°C. After 30 minutes of deposition, the electrode is removed and washed with deionized water to obtain an ultra-stable high-entropy metal oxide electrode that can be used for AC reversal.

[0021] The advantages of this invention are:

[0022] 1) Excellent corrosion resistance: An ultra-stable corrosion-resistant carbide layer is formed on the tantalum substrate by ion implantation technology. Titanium carbide ions and zirconium carbide ions are implanted under specific vacuum, temperature and energy conditions, which greatly improves the corrosion resistance of the electrode and can extend the service life of the electrode in harsh environments.

[0023] 2) Unique high-entropy alloy formulation and preparation method: Seven metal elemental powders, namely tantalum, rubidium, gadolinium, dysprosium, chromium, nickel and cadmium, are selected and mixed in a specific molar ratio. The mixture is mechanically alloyed using a planetary ball mill and heat-treated under specific conditions. Then, it is combined with argon carrier gas injection and high-energy laser direct energy deposition to form a high-entropy alloy surface active layer, which produces a gradient grain structure and enhances the performance of the electrode.

[0024] 3) Enhanced surface activity and corrosion resistance: Plasma treatment and ceramicization of the high-entropy alloy surface active layer are carried out. The high-entropy alloy layer is transformed into a high-entropy ceramic layer by using a mixed gas of argon and oxygen at specific power, time and temperature. At the same time, a nano-titanium dioxide coating is prepared by sol-gel method, which further improves the surface activity and corrosion resistance of the electrode.

[0025] 4) AC reversible electrode prevents scaling and saves costs: The electrode can be reversed by alternating current without affecting the electrode. This effectively prevents calcium and magnesium ions in high-salt wastewater from scaling on the electrode, saving a lot of reagent and labor costs, and providing an efficient and economical solution for high-salt wastewater treatment. IV. Description of the attached drawings

[0026] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the following description of the specific embodiments are briefly explained. Figure 1 The formation of scale on the surface of an ultrastable high-entropy metal oxide electrode suitable for AC reversal is shown by scanning electron microscopy under AC reversal frequencies of 20 Hz (a), 10 Hz (b), 0.1 Hz (c), and 0 Hz (d).

[0027] Figure 2 The change of exchange current intensity over time for an ultra-stable high-entropy metal oxide electrode that can be used for AC reversal is shown under AC reversal frequencies of 20Hz, 10Hz, 0.1Hz, and 0Hz.

[0028] Figure 3 The variation of the AC impedance (EIS) spectrum of an ultrastable high-entropy metal oxide electrode surface that can be used for AC reversal is determined under AC reversal frequencies of 20Hz, 10Hz, 0.1Hz, and 0Hz.

[0029] Figure 4The variation of calcium ion concentration with reaction time in solutions with different initial calcium ion concentrations under 20Hz AC reversal conditions for an ultrastable high-entropy metal oxide electrode that can be used for AC reversal.

[0030] Figure 5 To illustrate the batch degradation process of landfill leachate using commercially available lead oxide electrodes at an AC reversal frequency of 20Hz, the electrode activity varies with the degradation batch.

[0031] Figure 6 To illustrate the batch degradation process of landfill leachate using an ultra-stable high-entropy metal oxide electrode with AC reversal frequency of 20Hz, the electrode activity varies with the degradation batch.

[0032] Figure 7 To demonstrate the batch degradation process of fracturing flowback fluid using an ultra-stable high-entropy metal oxide electrode that can be used for AC reversal at an AC reversal frequency of 20Hz, the electrode activity varies with the degradation batch. V. Detailed Implementation Methods

[0033] The present invention will now be described in detail with reference to the accompanying drawings and embodiments:

[0034] Example 1:

[0035] An ultra-stable high-entropy metal oxide electrode for AC reversal is characterized by the following steps in its preparation method: First, a tantalum substrate is subjected to high-precision grinding to achieve a surface roughness of Ra 0.5 μm. Then, the ground tantalum substrate is placed in an ultrasonic cleaner and cleaned with acetone for 15 minutes to remove surface oil. Next, it is rinsed with deionized water and then immersed in a 5% dilute hydrochloric acid solution for 15 minutes to remove surface oxides. Finally, it is rinsed with deionized water and dried at 100°C for 30 minutes. An ultra-stable corrosion-resistant carbide layer is formed using ion implantation technology, with titanium carbide and zirconium carbide ions implanted at an energy of 120 keV and a dose of 8 × 10⁻⁶ ions. 16 ions cm –2 The injection process is carried out under a vacuum of 1×10⁻⁶. –3 The process was carried out in an environment of Pa, with an injection temperature of 150℃ and an injection time of 10s, to obtain a tantalum substrate with an ultra-stable corrosion-resistant carbide layer. Seven elemental metal powders—tantalum, rubidium, gadolinium, dysprosium, chromium, nickel, and cadmium—were selected and mixed in a molar ratio of 120:7:16:22:9:2:1. The mixed raw materials were then placed in a planetary ball mill for mechanical alloying treatment at a speed of 400 rpm. –1 The ball-to-material ratio was 15:1, the ball milling time was 20 hours, and argon gas was introduced during the ball milling process to prevent metal oxidation. The milled powder was then subjected to a vacuum of 1×10⁻⁶. –2Heat treatment was performed under vacuum at 800℃ for 2 hours to obtain a mixed powder of seven metals. The mixed powder of the seven metals was then injected with argon as the carrier gas at a controlled injection rate of 20 L / min. –1 The nozzle temperature is 1200℃, and the laser is progressively sprayed onto a tantalum substrate with an ion-implanted, ultra-stable, corrosion-resistant carbide layer. Simultaneously, high-entropy alloy powder is fused onto the tantalum substrate using high-energy laser direct energy deposition (HEAD) to form a high-entropy alloy surface active layer. The laser power is 15kW, and the scanning speed is 0.5mm / s. –1 The overlap rate was 40%, and the cladding process was carried out under argon protection. Due to cyclic heat input and rapid solidification, the deposited high-entropy alloy exhibited a gradient grain structure with alternating equiaxed and columnar crystals. The surface active layer of the high-entropy alloy after laser cladding underwent plasma treatment and ceramicization to improve its surface activity and corrosion resistance. The plasma treatment used a mixture of argon and oxygen, with an oxygen volume fraction of 10%, a treatment power of 300W, a treatment time of 20min, and a treatment temperature of 50℃, transforming the high-entropy alloy layer into a high-entropy ceramic layer. A nano-titanium dioxide coating was then prepared on the high-entropy ceramic layer using the sol-gel method. First, tetrabutyl titanate, ethanol, acetylacetone, and deionized water were mixed in a mass ratio of 8:2:10:1 and stirred until a sol was obtained. Then, the electrode was immersed in the sol at a depth of 4mm / min. –1 After repeated lifting and drying in air, the electrode was heat-treated at 450℃ for 2 hours. Finally, the electrode was modified using ion doping technology to improve its electrocatalytic activity and selectivity. Molybdenum ions were selected for doping at a concentration of 3% by electrochemical deposition at a voltage of -1.0V. The deposition process was carried out in an electrolyte containing 20% ​​ammonium molybdate at 40℃ for 30 minutes. After the deposition time, the electrode was removed and washed with deionized water to obtain an ultra-stable high-entropy metal oxide electrode suitable for AC reversing.

[0036] Example 2:

[0037] The scale inhibition performance of the ultrastable high-entropy metal oxide electrode (hereinafter referred to as the sample electrode) obtained in Example 1, which can be used for AC reversal, was tested under different AC reversal conditions. The tests were conducted in a 150 mL glass vessel, using a 1 cm × 1 cm sample electrode as the working electrode, a platinum sheet electrode as the counter electrode, and a saturated calomel electrode as the reference electrode. The reaction temperature was 60 °C, and the CaCl2 concentration in the electrolyte was set to 300.0 mg / L. –1 NaHCO3 concentration 300.0 mg / L –1 The concentration of MgCl2 was 150.0 mg / L. –1 The supporting electrolyte Na2SO4 concentration is 1.0 g / L.–1 A periodic reverse current with a current density of 10 mA cm⁻¹ was applied to the sample electrode using a CHI660E electrochemical workstation. –1 The reverse electrode frequencies were 0Hz (i.e., DC), 0.1Hz, 10Hz, and 20Hz. After a certain reaction time, the sample electrode was subjected to in-situ measurement of AC impedance and linear scanning voltammetry. After the reaction was completed, the sample electrode was removed and characterized by scanning electron microscopy.

[0038] Simultaneously, the initial CaCl2 concentration was adjusted to investigate the effect of different calcium ion concentrations on the scaling behavior of the sample electrode under 20Hz inverted electrode conditions. This was mainly determined by the decrease in calcium ion concentration, which was measured according to the national standard GB7476-1987. Calcium ions were titrated with disodium EDTA solution at a pH of 12–13.

[0039] Scanning electron microscope images are attached. Figure 1 As shown, as the reversal frequency gradually decreases, scaling becomes more and more obvious. Under DC conditions, even large crystals appear. High-frequency (20Hz) AC reversal is beneficial to the active interface of the sample electrode.

[0040] Changes in exchange current intensity (with appendix) Figure 2 This also proves the above conclusion. An alternating current of 20Hz can ensure that a stable exchange current exists on the sample electrode surface at all times, while under 0Hz conditions, scale forms rapidly, causing the current to shrink rapidly to zero.

[0041] Under AC reversal frequencies of 20Hz, 10Hz, 0.1Hz, and 0Hz, the differences in the AC impedance spectra of the sample electrodes are also extremely significant. At high frequencies, the real part of the AC impedance (ohms) is significantly lower than that at low frequencies (see appendix). Figure 3 ).

[0042] Under high-frequency conditions, the effect of different calcium ion concentrations on the scaling behavior of the sample electrodes under 20Hz reversal conditions was investigated. It was found that no significant scaling occurred on the sample electrodes within 60 minutes; the decrease in calcium ion concentration was minimal, and most of the calcium ion deposits were in-solution precipitates rather than deposited on the electrode surface. (See attached image) Figure 4 ).

[0043] Example 3:

[0044] The sample electrode prepared in this invention and a commercially available lead oxide electrode were used to treat leachate collected from a landfill. The initial concentration (chemical oxygen demand) of the leachate was 350 mg / L, and the hardness was 570 mg / L (CaCO3). The electrocatalytic reactor was made of plexiglass and had a volume of 30 (length) × 30 (width) × 50 (height) cm.3 The working electrode is the sample electrode, with an area of ​​30 (length) × 30 (width) cm. 2 The electrode is placed on one side of the reactor, while the counter electrode, made of the same stainless steel plate as the working electrode, is placed on the other side. An AC power source of 10 mA / cm² is provided by a square wave frequency converter. -2 Regularly sampled water samples and determined the concentration of chemical oxygen demand in the samples according to HJ 828-2017 (Water Quality - Determination of Chemical Oxygen Demand - Potassium Dichromate Method).

[0045] The results showed that commercially available lead oxide electrodes could not maintain their catalytic activity under AC reverse polarity conditions; after 10 cycles of degradation testing, their activity decreased by more than 60% (see attached). Figure 5 In contrast, the sample electrode maintained high electrocatalytic performance; after 10 cycles of testing, its activity showed almost no significant change, and the degradation rate remained above 95% for 300 minutes (see attached). Figure 6 ).

[0046] Example 4:

[0047] The sample electrode prepared in this invention was used to treat fracturing flowback fluid collected from a drilling site. The initial concentration (chemical oxygen demand) of the fracturing flowback fluid was 210 mg / L, and the hardness was 336 mg (CaCO3) / L. The results showed that the sample electrode maintained high electrocatalytic performance; after 10 cycles of testing, its activity showed almost no significant change, and the degradation rate remained above 80% for 300 min (see attached diagram). Figure 7 )

[0048] The specific embodiments described above are only used to illustrate the spirit of the present invention. The scope of protection of the present invention is not limited thereto. For those skilled in the art, other embodiments can be easily made by means of changes, substitutions or modifications based on the technical content disclosed in this specification. All such other embodiments should be covered within the scope of protection of the present invention.

Claims

1. A superstable high-entropy metal oxide electrode that can be used for AC reversal, characterized in that, The electrode is prepared by the following steps: Step 1: The tantalum substrate is subjected to high-precision polishing to achieve a surface roughness of Ra 0.5μm. Then, the polished tantalum substrate is placed in an ultrasonic cleaner and cleaned with acetone for 15 minutes to remove surface oil. Next, it is rinsed with deionized water and then immersed in a 5% dilute hydrochloric acid solution for 15 minutes to remove surface oxides. Finally, it is rinsed with deionized water and dried at 100℃ for 30 minutes. Step 2: An ultra-stable corrosion-resistant carbide layer is formed using ion implantation technology. The implanted ions are titanium carbide ions and zirconium carbide ions, the implantation energy is 120 keV, and the implantation dose is 8 × 10⁻⁶. 16 ions cm -2 The injection process is carried out under a vacuum of 1×10⁻⁶. -3 The implantation was carried out in an environment of Pa, with an implantation temperature of 150°C and an implantation time of 10 seconds, to obtain a tantalum substrate with an ultra-stable corrosion-resistant carbide layer. Step 3: Select seven elemental metal powders (tantalum, rubidium, gadolinium, dysprosium, chromium, nickel, and cadmium) and mix them in a molar ratio of 120:7:16:22:9:2:

1. Place the mixed raw materials into a planetary ball mill for mechanical alloying treatment at a speed of 400 rpm. -1 The ball-to-material ratio was 15:1, the ball milling time was 20 hours, and argon gas was introduced during the ball milling process to prevent metal oxidation. The milled powder was then subjected to a vacuum of 1×10⁻⁶. -2 Heat treatment was performed under vacuum at 800℃ for 2 hours to obtain a mixed powder of 7 metals. Step 4: Using argon as the carrier gas, inject the mixed powder of the seven metals obtained in Step 3 at a rate of 20 L / min. -1 The nozzle temperature was 1200℃. The laser was progressively scanned onto the tantalum substrate with an ultra-stable, corrosion-resistant carbide layer obtained in step 2 after ion implantation treatment. Simultaneously, high-entropy alloy powder was fused onto the tantalum substrate using high-energy laser direct energy deposition (HEAD) to form a high-entropy alloy surface active layer. The laser power was 15kW, and the scanning speed was 0.5 mm / s. -1 The overlap rate is 40%, and the cladding process is carried out under argon protection. Due to the cyclic heat input and rapid solidification, the deposited high-entropy alloy will produce a gradient grain structure with alternating growth of equiaxed and columnar crystals. Step 5: The high-entropy alloy surface active layer obtained in step 4 after laser cladding is subjected to plasma treatment and ceramicization to improve its surface activity and corrosion resistance. The plasma treatment uses a mixture of argon and oxygen, with an oxygen volume fraction of 10%, a treatment power of 300W, a treatment time of 20min, and a treatment temperature of 50℃ to transform the high-entropy alloy layer into a high-entropy ceramic layer. Step 6: A nano-titanium dioxide coating is prepared on the high-entropy ceramic layer obtained in Step 5 using the sol-gel method. First, tetrabutyl titanate, ethanol, acetylacetone, and deionized water are mixed in a mass ratio of 8:2:10:1 and stirred until homogeneous to obtain a sol. Then, the electrode is immersed in the sol at a depth of 4 mm / min. -1 After repeated lifting and drying in air, the product is subjected to heat treatment at 450℃ for 2 hours. Step 7: Finally, the electrode is modified using ion doping technology to improve its electrocatalytic activity and selectivity. Molybdenum ions are selected for doping at a mass concentration of 3%, and the doping method is electrochemical deposition. The deposition voltage is -1.0V, and the deposition process is carried out in an electrolyte containing 20% ​​ammonium molybdate at a temperature of 40℃. After 30 minutes of deposition, the electrode is removed and washed with deionized water to obtain an ultra-stable high-entropy metal oxide electrode that can be used for AC reversal.

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