A preparation method for denim dye electrocatalytic hydrogenation cathode material

Abstract

The present invention relates to a method for preparing a denim dye electrocatalytic hydrogenation cathode material, comprising: (1) pre-treating a carbon-based substrate material, followed by surface oxidation and carbonization; (2) dissolving a reagent containing a molybdenum source and a sulfur source in deionized water, then adding a metal salt to the solution and stirring to obtain a uniform solution; (3) adding the carbon-based substrate material treated in step (1) to the solution for a hydrothermal reaction; (4) naturally cooling to room temperature after the reaction, washing the obtained electrode material, and then vacuum drying to obtain the denim dye electrocatalytic hydrogenation cathode material. The preparation method of the present invention is simple, and the obtained cathode material selectively generates active hydrogen during alkaline water electrolysis. The active hydrogen with strong reducing properties significantly improves the reduction efficiency of the dye adsorbed on the electrode surface, and can also control the formation of active hydrogen, avoid excessive reduction of the dye, improve the dye reduction efficiency, and ensure dyeing quality.

Description

Technical Field

[0001] The invention belongs to the field of fabric dyeing and finishing, and in particular relates to a method for preparing a denim dye electrocatalytic hydrogenation cathode material. Background Art

[0002] Traditionally, denim is dyed with vat dyes, such as indigo and sulfur dyes. Due to the inherent properties of these dyes, indigo and sulfur dyes can only be dyed after being reduced to their leuco form, which then undergoes a process of infiltration, adsorption, and oxidation in the air. For example, in the indigo dyeing process, hydrosulfite and caustic soda are added to the indigo dye solution. At a certain temperature, the indigo is reduced to its leuco form, where it forms hydrogen bonds with the yarn fibers, completing the dyeing process. However, multiple padding cycles are required to achieve the desired dyeing effect. For example, when dyeing denim yarn with indigo, six to twelve dye baths are typically used, depending on the desired color depth, resulting in a lengthy production process. Because leuco indigo is easily oxidized by oxygen in the air during the dyeing process, excess indigo mother liquor and dye auxiliaries are often added to the dye baths to maintain a stable dye concentration. Furthermore, uneven yarn tension control and a large amount of floating color on the yarn hinder further penetration of dye molecules into the fiber, resulting in low dye utilization and dye uptake, poor rubbing fastness, and color differences between edges and ends. Furthermore, dyeing consumes large amounts of water, hydrosulfite, and other dyes and chemicals. The resulting wastewater pollutes the environment and significantly increases wastewater treatment costs. Therefore, developing a clean denim dyeing technology with a short process, low energy consumption, high water efficiency, and zero carbon emissions can improve denim dyeing quality while reducing energy consumption and pollutant emissions during production, which is of great significance to the sustainable development of denim production.

[0003] In recent years, researchers have been studying novel reduction methods to address the shortcomings of sodium hydrosulfite, such as large dosage, difficult storage, and environmental pollution. These include novel chemical reduction methods (such as sodium hydrosulfite regeneration, environmentally friendly reducing agents, and two-component systems involving divalent iron salts), catalytic hydrogenation pre-reduction, and electrochemical reduction. The main principle of electrochemical reduction is to replace the reducing agent with electrons, and no harmful byproducts are produced during the reaction, making it a green and environmentally friendly dyeing method. From the perspective of high electron transfer speed and the controllability of the applied voltage / current over the reaction, electrochemical technology has the advantages of high efficiency, cleanliness, and certain tunability and controllability, which has promoted electrochemical reduction dyeing to become a current research hotspot.

[0004] Currently, electrochemical reduction methods for denim dyes can be broadly categorized into three types: direct electroreduction, indirect electrochemical reduction, and electrocatalytic hydrogenation. Direct electroreduction primarily involves two mechanisms: direct electron transfer between the dye and the electrode solid phases, and reduction via dye free radicals. Due to the limited interface between the cathode material and the dye particles and the low free radical concentration, the dye concentration required to achieve the same hue is higher than that required by conventional reduction processes. Therefore, direct electroreduction is inefficient, while indirect electrochemical reduction and electrocatalytic hydrogenation are the most promising methods for industrialization. Indirect electrochemical reduction, which involves adding a reversible redox couple to the dye liquor as an electron carrier, offers advantages such as low chemical reagent usage, easily controllable dyeing conditions, minimal wastewater production, and dye liquor recyclability. However, continuous dyeing requires the addition of an additional mediator feed to compensate for mediator losses caused by liquid discharge proportional to the amount of fabric or yarn. Furthermore, filtration during dye liquor recovery increases costs and introduces additional technical challenges.

[0005] Electrocatalytic hydrogenation using nickel or similar large-surface-area conductive catalytic materials with low hydrogen overvoltage is a promising electrocatalytic reduction method and has been successfully applied in numerous organic reactions. Electrocatalytic hydrogenation of vat dyes primarily utilizes active hydrogen generated in situ by water electrolysis to reduce the vat dyes onto a conductive catalytic metal with a low hydrogen evolution overpotential to a soluble leuco form. This approach utilizes readily available raw materials, is environmentally friendly, and avoids the tedious process of electrochemical hydrogen production followed by pure chemical catalytic hydrogenation. By applying an appropriate voltage, the hydrogen evolution side reaction is reduced, thereby optimizing the hydrogenation process. However, vat and sulfur dyes are mostly water-insoluble solid particles, resulting in poor contact with catalysts. Consequently, research has long focused on the selection of electrocatalytically active materials. Commonly used materials are primarily platinum group elements and transition metals. However, platinum group metals (such as platinum, ruthenium, and palladium) are expensive and prone to deactivation; transition metals (such as iron, cobalt, nickel, molybdenum, and tungsten) have high overpotentials and poor current efficiency; and achieving industrially viable reduction rates still requires a large electrode surface area. Therefore, there is an urgent need to develop a new electrode material and electrochemical reduction dyeing method to improve the reduction efficiency, current efficiency and dyeing effect in the electrocatalytic reduction of dyes. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing a denim dye electrocatalytic hydrogenation cathode material. The obtained cathode material selectively generates active hydrogen during alkaline water electrolysis. The active hydrogen with strong reducing properties significantly improves the reduction efficiency of the dye adsorbed on the electrode surface. At the same time, the formation of active hydrogen can be controlled to avoid excessive reduction of the dye, improve the dye reduction efficiency, and ensure dyeing quality.

[0007] The present invention provides a method for preparing a denim dye electrocatalytic hydrogenation cathode material, comprising:

[0008] (1) Pre-treating the carbon-based substrate material, followed by surface oxidation and carbonization;

[0009] (2) dissolving a reagent containing a molybdenum source and a sulfur source in deionized water, then adding a metal salt to the solution and stirring to obtain a uniform solution;

[0010] (3) adding the carbon-based substrate material treated in step (1) to the above solution for hydrothermal reaction;

[0011] (4) After the reaction is completed, the mixture is naturally cooled to room temperature, and the obtained electrode material is repeatedly washed with deionized water and ethanol, and then vacuum-dried in an oven to obtain a denim dye electrocatalytic hydrogenation cathode material.

[0012] The carbon-based substrate material in step (1) is at least one of carbon cloth, carbon paper, carbon felt, and graphite felt.

[0013] The pretreatment method in step (1) is: soaking the carbon-based substrate material in an acetone solution for 8 to 18 hours to remove surface impurities; then rinsing with deionized water and drying.

[0014] The oxidation in step (1) is specifically as follows: placing the carbon-based substrate material in dilute acid for oxidation (hydrophilic) treatment, then rinsing with deionized water and drying; wherein the dilute acid is sulfuric acid with a volume fraction of 5% to 15%, or nitric acid with a volume fraction of 10% to 30%; the oxidation process temperature is 30 to 75°C, and the treatment time is 30 to 120 minutes.

[0015] The carbonization in step (1) is specifically as follows: nitrogen protection is passed through, the carbonization treatment temperature is 500-900° C., and the carbonization treatment time is 30-120 min.

[0016] The reagent containing a molybdenum source in the step (2) is at least one of sodium molybdate, ammonium molybdate, and ammonium tetrathiomolybdate, and the mass ratio of the reagent containing a molybdenum source to deionized water is 1:20 to 1:30; the reagent containing a sulfur source is one or more of thiourea, thioacetamide, and ammonium tetrathiomolybdate, and the mass ratio of the reagent containing a sulfur source to deionized water is 1:5 to 1:15.

[0017] The metal salt in step (2) is at least one of iron salt, cobalt salt, nickel salt, copper salt and manganese salt.

[0018] The iron salt is one of ferric sulfate, ferrous sulfate, ferric nitrate, ferrous nitrate, ferric chloride, and ferrous chloride, and the mass ratio of the iron salt to deionized water is 1:800 to 1:2000; the cobalt salt is one of cobalt nitrate and cobalt chloride, and the mass ratio of the cobalt salt to deionized water is 1:1000 to 1:3000; the nickel salt is one of nickel nitrate, nickel sulfate, nickel acetate, and nickel chloride, and the mass ratio of the nickel salt to deionized water is 1:750 to 1:2500; the copper salt is one of copper nitrate and copper sulfate, and the mass ratio of the copper salt to deionized water is 1:500 to 1:2000; the manganese salt is manganese sulfate, and the mass ratio of the manganese salt to deionized water is 1:750 to 1:1500.

[0019] The hydrothermal reaction kettle in step (3) is a stainless steel autoclave lined with polytetrafluoroethylene, with a volume of 20 to 100 mL; the hydrothermal reaction temperature is 180 to 220° C., and the reaction time is 6 to 20 hours.

[0020] The vacuum drying temperature in step (4) is 50-80° C., and the vacuum drying time is 6-12 hours.

[0021] The present invention also provides a method for constructing a high-efficiency electrochemical reduction device for denim dyes, comprising:

[0022] like Figure 1 As shown, the electrochemical high-efficiency reduction device for denim dye liquid flow comprises a cathode catalytic electrode, a cathode chamber, a grid, an anode electrode, an anode chamber, and a diaphragm; wherein the cathode catalytic electrode uses the above-mentioned denim dye electrocatalytic hydrogenation cathode material; the anode electrode is any one of a graphite electrode and a stainless steel electrode; the diaphragm is a cation exchange membrane; (1) adding an auxiliary electrolyte to the alkaline solution and stirring evenly to obtain an anolyte;

[0023] (2) adding the dye to the alkali solution and stirring uniformly to obtain a cathode electrolyte;

[0024] (3) Under the protection of protective gas, the cathode and anode electrolytes are respectively introduced into the cathode chamber and anode chamber of the liquid flow electrolytic cell at room temperature for electrolytic reduction.

[0025] The auxiliary electrolyte in step (1) is any one of sodium sulfate and sodium chloride, and the alkali solution is sodium hydroxide. The sodium sulfate content is 0.05-0.2 mol / L, the sodium chloride content is 0.1-0.4 mol / L, and the sodium hydroxide content is 0.5-1 mol / L.

[0026] The dye concentration in the cathode electrolyte in step (2) is 0.0038 to 0.228 mol / L, wherein the dye is any one of indigo, vat yellow F3GC, vat blue RS, vat red FBB, and sulphur black BR, and the pH of the cathode electrolyte is adjusted to 11 to 14 with an alkali solution, wherein the alkali solution is sodium hydroxide.

[0027] The protective gas in step (3) is nitrogen or argon, the electrolysis voltage is 1 to 30 V, and the reduction time is 15 to 150 minutes.

[0028] Beneficial effects

[0029] First, the present invention utilizes a carbon-based substrate material (such as carbon felt) as the substrate material, which has good electron transport and ion conduction characteristics, high porosity, light weight, high elasticity and low cost. The three-dimensional structure of the carbon felt has a high surface adsorption performance for active hydrogen and a certain affinity for dye molecules, which is conducive to the hydrogenation reduction of the dye molecules by active hydrogen.

[0030] Secondly, the present invention uses a one-step hydrothermal method to grow a nano-heterostructured molybdenum disulfide-based electrocatalyst on carbon felt and applies it to the electrocatalytic hydrogenation reduction dyeing of reduced dyes. The nanostructured molybdenum disulfide-based electrocatalyst is inexpensive, has a large specific surface area, and the heterogeneity and synergistic effect of the active sites between the metal and non-metal optimizes the catalyst structure, enhancing its adsorption capacity for active hydrogen and dye molecules, promoting contact and reaction between active hydrogen and dye molecules, and increasing the rate of the electrocatalytic hydrogenation reduction reaction of the dye.

[0031] Third, sodium sulfate, sodium chloride, etc. are used as auxiliary substances in the anode electrolyte to increase the conductivity of the electrolyte solution. At the same time, the electron transfer rate of the entire system is improved under the joint action of an external power supply.

[0032] Fourthly, the preparation method of the electrocatalytic hydrogenation cathode material for denim dyes provided by the present invention is simple. The obtained electrode material selectively produces active hydrogen during alkaline water electrolysis. The active hydrogen with strong reducing properties significantly improves the reduction efficiency of the dye adsorbed on the electrode surface. At the same time, it can control the formation of active hydrogen, avoid excessive reduction of the dye, improve the dye reduction efficiency, and ensure the dyeing quality.

[0033] Fifth, the electrochemical reduction equipment provided by the present invention is simple. The process completely abandons the use of hydrosulfite and does not add any medium, which can effectively reduce the amount of chemical reagents used. It will not produce a large amount of high-concentration salt. The dye solution can be recycled. The reduction dyeing process is cleaner and more environmentally friendly. The reaction conditions are mild. The hydrogenation process is easy to control, and it has obvious ecological and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1Schematic diagram of the electrochemical efficient reduction equipment for denim dye liquid flow.

[0035] Figure 2 Electrocatalytic reduction process and mechanism of denim dyes.

[0036] Figure 3 This is a scanning electron microscope image of the cathode material prepared in Example 1.

[0037] Figure 4 The LSV curve and Tafel curve of the cathode material prepared in Example 1 are shown.

[0038] Figure 5 This is a picture of indigo dyeing fabric using the cathode material prepared in Example 1. DETAILED DESCRIPTION

[0039] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0040] test:

[0041] The catalytic activity of the cathode electrode was evaluated by linear sweep voltammetry (LSV test), and the catalytic efficiency was evaluated by comparing the overpotential and Tafel slope. The current density was 10 mA / cm 2 The potential at which the overpotential is obtained is called the overpotential. The lower the overpotential, the higher the catalytic activity. The Tafel curve can be converted from the LSV curve according to the Tafel empirical formula to study the kinetic process on the electrode surface.

[0042] η=a+blog j;

[0043] Where η is the overpotential, a is the current density of 1 mA / cm 2 The overpotential is j, the current density is b, and the Tafel slope is b.

[0044] Dye Conversion (Reduction): Dissolve the dye in a 1.0 M caustic soda solution at concentrations of 1 g / L, 2 g / L, 3 g / L, 4 g / L, and 5 g / L. Reduce the dye to its leuco form using an excess of hydrosulfite or sodium sulfide. Determine the maximum absorption wavelength of the leuco form using a UV spectrophotometer and create a concentration vs. absorbance standard curve. Remove the cathode solution after electrochemical reduction, test its concentration, and calculate the dye conversion.

[0045] Dye conversion rate = C / Co;

[0046] Faradaic current efficiency = (m*N*F) / Q;

[0047] Where Co is the concentration of the dye solution, C is the concentration of the leuco dye, Q is the total charge, m is the number of moles of the leuco dye, n is the number of electrons required to reduce one dye molecule, and F is the Faraday constant.

[0048] Reduction potential ORP: Refer to the industry standard SL94-1994 method for determining redox potential. Use a redox potentiometer and place it in the dye solution at room temperature. After the value stabilizes, read the reduction potential value.

[0049] K / S value: Fold the sample into four layers (opaque) and test using a Color-i5 computerized colorimeter (X-Rite, USA). Measure at three different locations and take the average value.

[0050] Example 1

[0051] A method for preparing a denim dye electrocatalytic hydrogenation cathode material and a liquid flow electrochemical high-efficiency reduction device. The method comprises the following steps:

[0052] (1) The carbon felt was soaked in an acetone solution for 8 hours, then rinsed and dried with deionized water, and then placed in 10% dilute nitric acid at 60°C for 40 minutes, and then heated in a tubular furnace for carbonization treatment (600°C, 60 minutes, nitrogen protection).

[0053] (2) 1.235 g of ammonium molybdate tetrahydrate and 2.218 g of thiourea were dissolved in 30 mL of deionized water, and 0.0215 g of nickel sulfate hexahydrate was added and stirred to obtain a uniform solution. The pretreated carbon felt was then added to the above solution and transferred to a hydrothermal reactor. The reaction was carried out in a vacuum oven at 200°C for 8 hours. The obtained cathode material was further repeatedly washed with distilled water and ethanol, and then dried in a vacuum oven. The denim dye electrocatalytic hydrogenation cathode material was obtained.

[0054] (3) The denim dye electrocatalytic hydrogenation cathode material prepared above was used as the cathode. The indigo concentration in the cathode electrolyte was 0.019 mol / L, and the pH was adjusted to 13 with alkaline solution. The anode was a graphite electrode, and the electrolyte composition was 0.5 mol / L sodium hydroxide and 0.1 mol / L sodium sulfate. The diaphragm was a sulfonic acid type cation exchange membrane. Electrolytic reduction was carried out under nitrogen protection at room temperature, with an electrolysis voltage of 6 V and a dyeing time of 30 min. Electrochemical reduction dyeing: Pure cotton semi-bleached coarse twill cloth pre-moistened with distilled water was added to the cathode electrolyte obtained in step (3), with a bath ratio of 1:20 and a dyeing time of 1 min. After dyeing, the fabric was air-oxidized, and then soaped and washed to complete the post-dyeing treatment. The color depth K / S value of the resulting fabric was tested.

[0055] After testing; the overpotential of the cathode material obtained in Example 1 was 145.65mV, the Tafel slope was 100.53mV / dev, the dye conversion rate was 48%, the current efficiency was 15.5%, the cathode liquid reduction potential after electrolysis was -821mV, and the dyeing sample K / S value was 16.23.

[0056] Example 2

[0057] The preparation method of the cathode material in this embodiment includes the following steps:

[0058] (1) The carbon felt was soaked in an acetone solution for 10 hours, then rinsed and dried with deionized water, and then treated in 10% dilute sulfuric acid at 70°C for 30 minutes, and then heated in a tubular furnace for carbonization treatment (500°C, 90 minutes, nitrogen protection).

[0059] (2) 0.785 g of sodium molybdate dihydrate and 1.786 g of thioacetamide were dissolved in 20 mL of deionized water, and 0.0185 g of ferric sulfate nonahydrate was added and stirred to obtain a uniform solution. The pretreated carbon felt was then added to the above solution and transferred to a hydrothermal reactor. The reaction was carried out in a vacuum oven at 180°C for 10 hours. The obtained cathode material was further repeatedly washed with distilled water and ethanol, and then dried in a vacuum oven. The denim dye electrocatalytic hydrogenation cathode material was obtained.

[0060] (3) The denim dye electrocatalytic hydrogenation cathode material prepared above was used as the cathode. The indigo concentration in the cathode electrolyte was 0.019 mol / L, and the pH was adjusted to 13 with alkaline solution. The anode was a graphite electrode, and the electrolyte composition was 0.5 mol / L sodium hydroxide and 0.1 mol / L sodium sulfate. The diaphragm was a sulfonic acid type cation exchange membrane. Electrolytic reduction was carried out under nitrogen protection at room temperature, with an electrolysis voltage of 5 V and a dyeing time of 25 minutes. Electrochemical reduction dyeing: Pure cotton semi-bleached coarse twill cloth pre-moistened with distilled water was added to the cathode electrolyte obtained in step (3), with a bath ratio of 1:20 and a dyeing time of 1 minute. After dyeing, the fabric was air-oxidized, and then soaped and washed to complete the post-dyeing treatment. The color depth K / S value of the resulting fabric was tested.

[0061] After testing; the overpotential of the cathode material obtained in Example 2 was 176.43mV, the Tafel slope was 121.14mV / dev, the dye conversion rate was 44.5%, the current efficiency was 13.7%, the cathode liquid reduction potential after electrolysis was -812mV, and the dyeing sample K / S value was 15.84.

[0062] Comparative Example

[0063] Electrolytic system and indirect electrochemical dyeing process for vat dyes:

[0064] (1) Electrochemical reduction and dissolution of dyes: A complex system obtained by thoroughly mixing ferric sulfate and sodium gluconate, indigo dye, and sodium borohydride were added to a 0.0625 mol / L caustic soda solution in this order, and the mixture was stirred thoroughly to obtain a cathode electrolyte. The contents of the electrolyte were 0.004 mol / L iron ions, 0.012 mol / L sodium gluconate, 0.019 mol / L indigo dye, and 0.016 mol / L sodium borohydride. The content of the iron ions in the anolyte was 0.25 mol / L, and the content of sodium sulfate was 0.2112 mol / L. The cathode used was an iron electrode, the anode was a graphite electrode, the electrolysis voltage was 7.5 V, and the reduction was carried out at room temperature for 50 min under nitrogen protection. After the reduction was completed, a reduction potentiometer was placed in the dye solution at room temperature. After the value stabilized, the reduction potential was read.

[0065] (2) Electrochemical reduction dyeing: a semi-bleached pure cotton coarse twill cloth pre-moistened with distilled water is added to the solution of step (1) at a bath ratio of 1:20 and a dyeing time of 1 min. After dyeing, the fabric is oxidized by ventilation, and then soaped and washed to complete the post-dyeing treatment. The color depth K / S value of the resulting fabric is tested.

[0066] After the reduction was completed, the lowest reduction potential of the dye solution reached -807mV, and the color depth K / S value of the dyed cloth sample after washing with water and soaping was 15.56.

[0067] It can be seen from Example 1, Example 2 and the comparative example that the electrocatalytic reduction dyeing method proposed in the present invention uses fewer chemical reagents, has a lower electrolysis voltage, a shorter electrolysis time, a better dyeing effect, and higher energy-saving and environmental protection benefits than the traditional indirect electrochemical reduction dyeing method.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for constructing a high-efficiency electrochemical reduction device for denim dyes, comprising: The electrochemical high-efficiency reduction device for denim dye liquid flow comprises a cathode catalytic electrode, a cathode chamber, a grid, an anode electrode, an anode chamber, and a diaphragm; wherein the cathode catalytic electrode uses a denim dye electrocatalytic hydrogenation cathode material; the anode electrode is any one of a graphite electrode and a stainless steel electrode; and the diaphragm is a cation exchange membrane; ① Add auxiliary electrolyte to alkali solution and stir evenly to obtain anolyte; ② Add the dye to the alkali solution and stir evenly to obtain the cathode electrolyte; ③ Under the protection of protective gas, the cathode and anode electrolytes are respectively introduced into the cathode chamber and anode chamber of the liquid flow electrolytic cell at room temperature for electrolytic reduction; The auxiliary electrolyte in step ① is any one of sodium sulfate and sodium chloride, and the alkali solution is sodium hydroxide; The preparation method of the denim dye electrocatalytic hydrogenation cathode material comprises: (1) Pre-treating the carbon-based substrate material, followed by surface oxidation and carbonization; (2) dissolving a reagent containing a molybdenum source and a sulfur source in deionized water, then adding a metal salt to the solution and stirring to obtain a uniform solution; wherein the metal salt is an iron salt or a nickel salt; (3) adding the carbon-based substrate material treated in step (1) to the above solution for hydrothermal reaction; (4) After the reaction is completed, the mixture is naturally cooled to room temperature, and the obtained electrode material is repeatedly washed with deionized water and ethanol, and then vacuum-dried in an oven to obtain a denim dye electrocatalytic hydrogenation cathode material.

2. The construction method according to claim 1, wherein: The carbon-based substrate material in step (1) is at least one of carbon cloth, carbon paper, carbon felt, and graphite felt.

3. The construction method according to claim 1, wherein: The pretreatment method in step (1) is: soaking the carbon-based substrate material in an acetone solution for 8 to 18 hours to remove surface impurities; then rinsing with deionized water and drying.

4. The construction method according to claim 1, wherein: The oxidation in step (1) is specifically as follows: placing the carbon-based substrate material in dilute acid for oxidation treatment, then rinsing with deionized water and drying; wherein the dilute acid is sulfuric acid with a volume fraction of 5% to 15%, or nitric acid with a volume fraction of 10% to 30%; the oxidation process temperature is 30 to 75°C, and the treatment time is 30 to 120 minutes.

5. The construction method according to claim 1, wherein: The carbonization in step (1) is specifically as follows: nitrogen protection is passed through, the carbonization treatment temperature is 500-900° C., and the carbonization treatment time is 30-120 min.

6. The construction method according to claim 1, wherein: The reagent containing a molybdenum source in the step (2) is at least one of sodium molybdate, ammonium molybdate, and ammonium tetrathiomolybdate, and the mass ratio of the reagent containing a molybdenum source to deionized water is 1:20 to 1:30; the reagent containing a sulfur source is one or more of thiourea, thioacetamide, and ammonium tetrathiomolybdate, and the mass ratio of the reagent containing a sulfur source to deionized water is 1:5 to 1:

15.

7. The construction method according to claim 1, wherein: The iron salt is one of ferric sulfate, ferrous sulfate, ferric nitrate, ferrous nitrate, ferric chloride, and ferrous chloride, and the mass ratio of the iron salt to deionized water is 1:800 to 1:2000; the nickel salt is one of nickel nitrate, nickel sulfate, nickel acetate, and nickel chloride, and the mass ratio of the nickel salt to deionized water is 1:750 to 1:2500.

8. The construction method according to claim 1, wherein: The hydrothermal reaction kettle in step (3) is a stainless steel autoclave lined with polytetrafluoroethylene, with a volume of 20 to 100 mL; the hydrothermal reaction temperature is 180 to 220° C., and the reaction time is 6 to 20 hours.

9. The construction method according to claim 1, wherein: The vacuum drying temperature in step (4) is 50-80° C., and the vacuum drying time is 6-12 hours.

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