Preparation method of selenium cobalt rich in double defects and application thereof in electrocatalytic oxygen reduction for preparing hydrogen peroxide

Abstract

This invention relates to a method for preparing cobalt selenide rich in double defects and its application in the electrocatalytic reduction of oxygen to hydrogen peroxide. First, selenium powder is mixed with sodium hydroxide solution to obtain material A. Cobalt salt is mixed with EDTA-2Na solution to obtain material B. Material B and material A are then mixed and subjected to a hydrothermal reaction. The resulting product is centrifuged, washed, and vacuum dried to obtain cobalt selenide powder. The cobalt selenide powder is dispersed in anhydrous ethanol, and then potassium thiocyanate powder is added. After vigorous stirring, ultrasonic exfoliation is performed. The product is centrifuged, washed, dried, and calcined to obtain cobalt selenide rich in double defects. This invention provides a simple preparation method that can rapidly and cost-effectively prepare double-defect cobalt selenide under mild conditions. The obtained double-defect cobalt selenide can effectively reduce oxygen to hydrogen peroxide under electrocatalytic conditions, solving the problems of high price and low efficiency of current catalysts for hydrogen peroxide production under acidic conditions.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, specifically a method for preparing cobalt selenide rich in double defects and its application in the electrocatalytic reduction of oxygen to produce hydrogen peroxide. Background Technology

[0002] Currently, H2O2 is widely used in the chemical and environmental protection fields. It is an environmentally friendly, multifunctional oxidant, and one of its key advantages is its solubility in water and many organic solvents or pure substrates, producing no other harmful byproducts. The global demand for H2O2 is projected to reach 6 million tons by 2027. Currently, H2O2 production mainly involves the traditional anthraquinone process and the direct synthesis method from H2 and O2. The anthraquinone process typically requires complex, large-scale infrastructure and generates a large number of byproducts, posing safety concerns and significant costs for H2O2 transportation and storage. The direct synthesis method from H2 and O2 is a relatively greener route with lower synthesis and operating costs, but the mixing of H2 and O2 is prone to explosion, posing safety risks. Electrochemical oxygen reduction (ORR) to produce H2O2 can effectively solve the problems of high byproducts, low yield, high storage and transportation costs, and safety hazards associated with the anthraquinone process and the direct synthesis method from H2 and O2.

[0003] Oxygen reduction that involves a two-electron reaction (2e) - The ORR (Organic Reaction) reaction process produces only water as a byproduct, and under certain stringent technical requirements (such as in medical and aerospace applications), it can also generate high concentrations of H₂O₂, which is a significant advantage. Although many studies have been reported on 2e⁻... - While catalysts for ORR (Organic Recombinant Hydrocarbons) are available, highly active, selective, and inexpensive catalysts are still lacking. This is particularly relevant for the electrosynthesis of H₂O₂ under acidic conditions, which have broad practical applications. For example, Fenton's reagent is mainly used in organic synthesis and wastewater treatment, with an optimal pH range of 2.5-3.5. Therefore, studying the electrosynthesis of H₂O₂ in acidic media is of greater significance.

[0004] The main drawback of preparing H2O2 in acidic media is that most materials are unstable and even dissolve in acid. Some noble metals and their alloys exhibit good activity and stability. For example, early studies (Nature Materials, 2013, 12(12): 1137-1143) showed that carbon-supported mercury-platinum alloys or mercury-palladium nanoparticles can be used to synthesize H2O2 via two-electron ORR in acidic media, exhibiting high activity and selectivity. However, these catalysts contain rare noble metals and toxic mercury, thus limiting their application in H2O2 synthesis.

[0005] Therefore, it is necessary to develop high 2e in acidic systems. -Electrocatalytic materials with good ORR catalytic performance are urgently needed. Solving the aforementioned problems in the electrocatalytic H2O2 process is also one of the pressing issues that many forward-thinking researchers in this field need to address.

[0006] In recent years, transition metal selenides have been widely studied due to their abundant resources, low cost, and environmental friendliness. Constructing dual-deficiency cation and anion structures using defect engineering strategies is an effective way to improve catalytic performance. This approach enables highly efficient spatial separation and migration of charge carriers in dual channels, inducing electron transfer and redistribution, thereby enhancing the catalytic activity and selectivity of the catalyst for oxygen reduction to H₂O₂. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing cobalt selenide rich in dual defects and its application in electrocatalytic oxygen reduction to produce H2O2. First, cobalt selenide containing selenium defects is generated via hydrothermal reaction. Then, an appropriate amount of potassium thiocyanate is added to an anhydrous ethanol dispersion of cobalt selenide, and the mixture is thoroughly stirred to achieve SCN. - The cobalt selenide material, rich in dual defects, is obtained by directional adsorption at Co sites on the surface, followed by ultrasonic exfoliation, water washing, alcohol washing, and drying in a vacuum drying oven, and then calcination in a tube furnace. This process achieves controllable modulation and uniform distribution of cation defect concentration. The cobalt selenide exhibits good dispersibility, a large specific surface area, and good conductivity. It demonstrates excellent electrocatalytic oxygen reduction (H2O2) performance in acidic media, exhibiting high activity, selectivity, and yield. This solves the problems of low activity and selectivity, and high cost commonly found in current catalysts for H2O2 production under acidic conditions.

[0008] One objective of this invention is to provide a method for preparing cobalt selenide rich in dual defects, the method specifically comprising the following steps:

[0009] (1) Weigh a certain amount of selenium powder and add it to a NaOH solution with a concentration of 0.133 g / mL. Stir vigorously for 30 to 60 minutes to obtain mixture A;

[0010] (2) Weigh a certain amount of cobalt metal salt and add it to a 0.25 mol / L EDTA-2Na solution. Stir vigorously for 30 to 60 minutes to obtain mixture B.

[0011] (3) Add mixture B to mixture A and stir for 10-30 min to obtain mixture C. Transfer mixture C to a reactor for hydrothermal reaction. The hydrothermal reaction temperature is 200℃ and the reaction time is 6 h. After the hydrothermal reaction is completed, the reactor is naturally cooled to room temperature. Then, the product in the reactor is centrifuged and the black precipitate is collected and washed three times with hydrochloric acid solution. Then, it is washed with ultrapure water until the washing liquid is neutral. After that, the precipitate is collected and placed in a vacuum drying oven and dried at 60℃ for 12-20 h to obtain cobalt selenide powder.

[0012] (4) Weigh a certain amount of cobalt selenide powder prepared in step (3), add it to a beaker containing anhydrous ethanol and disperse it, then add a certain amount of potassium thiocyanate powder to the beaker and stir vigorously for 30-60 min; then transfer the beaker to a cell disruptor and sonicate it at 40-50℃ for 2-4 h, centrifuge the dispersion after sonication, wash the precipitate with anhydrous ethanol five times, collect a large amount of black precipitate, transfer it to a vacuum drying oven and dry it at 80℃ for 12 h, place the dried sample in a tube furnace and calcine it at 300℃ for 2 h in an air atmosphere, and finally obtain cobalt selenide rich in double defects.

[0013] As a preferred embodiment of the present invention, the cobalt salt in step (2) is one of cobalt nitrate, cobalt chloride and cobalt acetate.

[0014] As a preferred embodiment of the present invention, the molar ratio of selenium powder to cobalt salt is (1.8-2):1.

[0015] As a preferred embodiment of the present invention, the concentration of the hydrochloric acid solution in step (3) is 0.5 to 2 mol / L.

[0016] As a preferred embodiment of the present invention, the mass ratio of cobalt selenide powder to potassium thiocyanate powder added in step (4) is 1:(0.04~0.14).

[0017] As a preferred embodiment of the present invention, in step (4), the ultrasonic power is 100-250W, the centrifuge speed is 7500rpm, the centrifugation time is 4-6min, and the heating rate of the tube furnace is 5℃ / min.

[0018] The cobalt selenide rich in double defects prepared according to the above method is in the form of nanorods with a diameter of about 40 nm and a length of about 200 nm.

[0019] This invention also provides an application of the prepared double-defect-rich cobalt selenide as an electrocatalyst, particularly its application in the electrocatalytic reduction of oxygen to hydrogen peroxide in acidic media. The hydrogen peroxide yield of the double-defect cobalt selenide at 0 V vs. RHE is 147.74 mmol / g. cat. -1 h-1 Therefore, cobalt selenide with dual defects significantly improves acidic 2e - ORR performance.

[0020] Compared with existing technologies, this invention has significant advantages and beneficial effects. Through the above technical solution, this invention achieves considerable technological advancement and practicality, and has broad application value, possessing at least the following advantages:

[0021] (1) This invention uses selenium powder as the selenium source and cobalt salt as the cobalt source to obtain cobalt selenide with abundant selenium defects through a one-step hydrothermal method. A certain amount of potassium thiocyanate white crystalline powder is added to an anhydrous ethanol solution of cobalt selenide and stirred thoroughly to achieve SCN. - Directed adsorption at Co sites makes CoSCN more soluble in organic solutions, and ultrasonic exfoliation accelerates the dissolution of SCN. - The process of directional adsorption at Co sites and dissolution of CoSCN in organic solvents involved ultrasonic exfoliation, followed by washing with water and alcohol, drying in a vacuum oven, and then calcination in a tube furnace at a specific temperature. This process ultimately achieved controllable modulation and uniform distribution of cation defect concentration, yielding cobalt selenide rich in dual defects. Cobalt selenide rich in dual defects can effectively regulate the adsorption configuration of oxygen-containing intermediates and possesses appropriate binding energies. When used in the electrocatalytic oxygen reduction reaction to prepare H₂O₂, it exhibits higher activity and selectivity compared to ordered CoSe₂.

[0022] (2) The prepared cobalt selenide sample rich in dual defects exhibits a nanorod morphology. At 0.4V, the selectivity for H2O2 is significantly improved to 72%, which is beneficial for 2e. - The ORR process converts to H₂O₂. Its Tafel slope (155 mV / dec) is significantly lower than that of ordered cobalt selenide (275 mV / dec), indicating that the catalytic reaction kinetics of double-defect cobalt selenide are faster. C₂O₂ is rich in double-defect cobalt selenide. dl It is 0.32mFcm -2 This indicates that it has a high electrochemical active surface area, which is beneficial for 2e - ORR process. At 0V vs. RHE, the hydrogen peroxide yield of cobalt selenide rich in double defects was 147.74 mmol / g. cat. -1 h -1 Therefore, cobalt selenide with dual defects significantly improves acidic 2e⁻ content. - ORR performance.

[0023] (3) Based on the fact that double-defect cobalt selenide has good dispersibility, large specific surface area, and good conductivity, it has good electrocatalytic oxygen reduction to prepare H2O2 in acidic media, with high activity, selectivity and yield.

[0024] (4) The preparation method of the present invention is simple and can obtain double-defect cobalt selenide quickly and at low cost under mild conditions. The obtained double-defect cobalt selenide can effectively reduce oxygen to hydrogen peroxide under electrocatalytic conditions, which solves the problems of high price and low efficiency of current catalysts for producing hydrogen peroxide under acidic conditions. Attached Figure Description

[0025] Figure 1 This is a transmission electron microscope image of the double-defect cobalt selenide powder prepared in Example 1;

[0026] Figure 2 The X-ray crystal diffraction patterns are those of cobalt selenide rich in double defects (sample II) prepared in Example 1 and cobalt selenide (sample I) prepared in steps (1)-(3);

[0027] Figure 3 The Raman spectra are those of cobalt selenide rich in double defects prepared in Example 1 (sample II) and cobalt selenide prepared in steps (1)-(3) (sample I);

[0028] Figure 4 These are XPS images of cobalt selenide rich in double defects prepared in Example 1 (sample II) and cobalt selenide prepared in steps (1)-(3) (sample I);

[0029] Figure 5 This is the electron paramagnetic resonance (EPR) image of the double-defect cobalt selenide prepared in Example 1;

[0030] Figure 6 The polarization curves of cobalt selenide rich in double defects (sample II) prepared in Example 1 and cobalt selenide (sample I) prepared in steps (1)-(3) are used to electrocatalyze the production of hydrogen peroxide by oxygen reduction.

[0031] Figure 7 This is a catalyst selectivity diagram of cobalt selenide rich in double defects prepared in Example 1 (sample II) and cobalt selenide prepared in steps (1)-(3) (sample I);

[0032] Figure 8 The electron transfer graphs are of cobalt selenide rich in double defects prepared in Example 1 (sample II) and cobalt selenide prepared in steps (1)-(3) (sample I);

[0033] Figure 9 The Tafel slope diagrams are of cobalt selenide rich in double defects prepared in Example 1 (sample II) and cobalt selenide prepared in steps (1)-(3) (sample I);

[0034] Figure 10The double-layer capacitance diagrams are of cobalt selenide (sample II) rich in double defects prepared in Example 1 and cobalt selenide (sample I) prepared in steps (1)-(3);

[0035] Figure 11 This is a yield diagram of the oxygen reduction to H2O2 produced by cobalt selenide rich in double defects (sample II) prepared in Example 1 and cobalt selenide (sample I) prepared in steps (1)-(3). Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. The embodiments described and shown in the accompanying drawings can generally be implemented through various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claims, but merely to illustrate selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0037] This invention does not impose any special restrictions on the source of any of the raw materials used; they can be commercially available or self-made, and there are no special restrictions on their purity.

[0038] Example 1:

[0039] (1) Weigh 4 mmol of selenium powder and add it to a beaker containing 30 mL of NaOH (4 g of NaOH, Chinese medicine) solution. Stir vigorously for 30 min to obtain mixture A.

[0040] (2) Weigh 2 mmol of cobalt nitrate hexahydrate and add it to a beaker containing 10 mL of 0.25 MEDTA-2Na solution. Stir vigorously for 30 min to obtain mixture B.

[0041] (3) Add mixture B to mixture A and stir for 20 min to obtain mixture C. Transfer mixture C to a reactor for hydrothermal reaction at a temperature of 200℃ for 6 h. After the hydrothermal reaction is completed, allow the reactor to cool naturally to room temperature. Then, centrifuge the product in the reactor and collect the black precipitate. Disperse the black precipitate in 100 mL of 0.1 mol / L hydrochloric acid solution and stir for 6 h. Then centrifuge. Repeat this process three times with 100 mL of 0.1 mol / L hydrochloric acid solution each time, and centrifuge with ultrapure water until the washing solution is neutral. The centrifuge parameters are 7500 rpm and the centrifugation time is 4 min. After that, collect a large amount of black precipitate and place it in a vacuum drying oven at 60℃ for 24 h to obtain cobalt selenide powder, which is designated as sample I.

[0042] (4) Weigh 1.0g of the cobalt selenide powder prepared in step (3) (sample I), add it to a beaker containing 100mL of anhydrous ethanol and disperse it. Then add 0.1344g of potassium thiocyanate white crystalline powder to the beaker and stir vigorously for 60min. Then transfer the beaker to a cell disruptor and sonicate it at 40-50℃ for 4h. The ultrasonic power is 100W. Centrifuge the sonicated cobalt selenide dispersion at 7500rpm for 4min. Wash the precipitate five times with anhydrous ethanol. Then collect a large amount of black precipitate and transfer it to a vacuum drying oven and dry it at 80℃ for 12h. Place the dried sample in a tube furnace and calcine it at 300℃ (heating rate of 5℃ / min) for 2h in an air atmosphere. Finally, cobalt selenide rich in double defects is obtained and is recorded as sample II.

[0043] Figure 1 The transmission electron microscope (TEM) image of the double-defect cobalt selenide powder catalyst prepared in Example 1 shows that the prepared cobalt selenide sample rich in double defects has a nanorod morphology with a diameter of about 40 nm and a length of about 200 nm.

[0044] Electrochemical performance testing procedure for cobalt selenide rich in dual defects (sample II):

[0045] 5 mg of cobalt selenide rich in dual defects and 1 mg of conductive carbon black were weighed, added to 750 μL of isopropanol and 250 μL of ultrapure water, followed by 10 μL of 5% Nafion solution. The mixture was then sonicated until the catalyst was uniformly dispersed, yielding a dispersion. 2.5 μL of this dispersion was drop-coated onto a rotating ring-disk electrode to obtain the working electrode. A carbon rod and a saturated silver chloride electrode were used as the counter and reference electrodes, respectively, and the tests were performed using a Chenhua CHI760e electrochemical workstation rotating ring-disk instrument. The electrolyte used was a 0.1 mol / L HClO4 solution. Before testing the ORR, Ar gas was passed through the electrolyte for 30 min for CV activation, followed by oxygen passage for 30 min. The polarization curves were obtained at a scanning speed of 10 mV / s at 1600 rpm, with a ring voltage of 1.3 V relative to the standard hydrogen electrode and a disk voltage of -0.35 to 0.55 V relative to the saturated silver chloride electrode. All data were acquired after the scanning current stabilized.

[0046] 200 μL of the dispersion was drop-coated onto a 2.5 cm × 2.5 cm gas diffusion carbon paper to obtain an electrode sheet. Electrocatalytic oxygen reduction to hydrogen peroxide production was tested in a flow electrolytic cell using a 0.1 mol / L HClO4 solution. Under oxygen saturation, the hydrogen peroxide yield was plotted at 0 V vs. RHE, as shown in the figure. Figure 11 As shown.

[0047] The electrochemical performance of cobalt selenide (sample I) prepared in steps (1) to (3) was tested according to the above test method.

[0048] Figure 2 The X-ray crystal diffraction patterns of cobalt selenide rich in double defects (sample II) prepared in Example 1 and cobalt selenide (sample I) prepared in steps (1)-(3) are compared with the data of the cobalt selenide standard PDF card. Each diffraction peak can be assigned to the peaks of the (110), (011), (101), (111), (120), (121), (211), (002), (031), (131), (310) and (122) crystal planes of the cobalt selenide standard PDF card, which is consistent with the standard data, indicating that the material is cobalt selenide.

[0049] Figure 3 These are Raman spectra of cobalt selenide rich in double defects prepared in Example 1 (sample II) and cobalt selenide prepared in steps (1)-(3) (sample I), used to analyze the structural information of the samples. Figure 3 It can be seen that the sample is at 168cm. -1 and 668cm -1 The characteristic peaks on the left and right sides respectively indicate the A of CoSe2 g and A 1g Stretch mode, located at 465cm -1512cm -1 and 603cm -1 The peak at 185 cm⁻¹ is a characteristic peak of cobalt selenide. For cobalt selenide, the peak at 185 cm⁻¹ is... -1 and 300cm -1 The nearby characteristic peaks are due to vibrations caused by selenium defects.

[0050] Figure 4 XPS spectra of cobalt selenide rich in dual defects (sample II) prepared in Example 1 of this invention and cobalt selenide (sample I) prepared in steps (1)-(3) are shown. It can be seen that, compared to the cobalt selenide catalyst prepared in steps (1)-(3), the Co 2p spectrum of cobalt selenide rich in dual defects (sample II) shows a significant peak shift, moving towards higher binding energies, indicating the presence of cobalt defects in the bulk cobalt selenide phase. The Se 3d spectra of the samples show binding energies of 54.78 eV and 55.63 eV, respectively, corresponding to Se in CoSe2. 2- Se 3d 3 / 2 and Se 3d 5 / 2 The Se 3d spectrum of cobalt selenide rich in double defects (sample II) prepared in Example 1 also showed a significant peak shift and a shift towards higher binding energies. This is due to the generation of cobalt defects, which weakens the electron-accepting ability.

[0051] Figure 5 The EPR image of the double-defect cobalt selenide prepared in Example 1 of this invention shows that the sample exhibits a symmetrical EPR signal, and g = 2.003 and g = 2.17 confirm the existence of double defects.

[0052] Figure 6 The polarization curves for the electrocatalytic oxygen reduction to hydrogen peroxide production of cobalt selenide rich in double defects (sample II) prepared in Example 1 of this invention and cobalt selenide prepared in steps (1)-(3) are shown. It can be seen that the ring current and disk current of the double-defect cobalt selenide (sample II) are much higher than those of cobalt selenide (sample I). The ring current of all samples at 0.4 V relative to the standard hydrogen electrode is 0.40 mA / cm². -2 (Sample II) and 0.1 mAcm -2 (Sample I)

[0053] Figure 7 This is a catalyst selectivity diagram for cobalt selenide rich in double defects (sample II) prepared in Example 1 of this invention and cobalt selenide prepared in steps (1)-(3) (sample I). It can be seen that at 0.4 V, the selectivity for H2O2 significantly increases from 43% (sample I) to 72% (sample II). Clearly, cobalt selenide rich in double defects is beneficial for 2e... - The process of ORR converting to H2O2.

[0054] Figure 8 The electron transfer number diagrams are shown for cobalt selenide rich in double defects (sample II) prepared in Example 1 of this invention and cobalt selenide (sample I) prepared in steps (1)-(3). The calculated electron transfer number of cobalt selenide (sample I) at 0.4V is 3.07, while the electron transfer number of cobalt selenide with double defects (sample II) at 0.4V is 2.68 (cobalt selenide), which is closer to 2e - The theoretical electron transfer number of ORR.

[0055] Figure 9 Tafel plots are shown for cobalt selenide rich in double defects (sample II) prepared in Example 1 of this invention and cobalt selenide prepared in steps (1)-(3) (sample I). It can be seen that the Tafel slope value of cobalt selenide rich in double defects (155 mV / dec) is much lower than that of cobalt selenide (sample I) (275 mV / dec), indicating that the catalytic reaction kinetics of cobalt selenide rich in double defects are faster.

[0056] Figure 10 The image shows the double-layer capacitance of cobalt selenide rich in double defects (sample II) prepared in Example 1 of this invention and cobalt selenide (sample I) prepared in steps (1)-(3). It can be seen that C dl They are 0.32mFcm respectively -2 (Sample II) and 0.14 mFcm -2 (Sample I). Clearly, the double-defect cobalt selenide possesses a higher electrochemically active surface area, which is beneficial for 2e... - ORR procedure.

[0057] Figure 11 The graph shows the yield of H2O2 produced by catalytic oxygen reduction using cobalt selenide rich in double defects (sample II) prepared in Example 1 of this invention and cobalt selenide prepared in steps (1)-(3). It can be seen that the hydrogen peroxide yield of the double-defect cobalt selenide at 0V vs. RHE is 147.74 mmol / g. cat. -1 h -1 In contrast, cobalt selenide (sample I) exhibited a lower H2O2 yield, with a hydrogen peroxide yield of 61.14 mmol / g at 0 V vs. RHE. cat. -1 h -1 Therefore, cobalt selenide with dual defects significantly improves acidic 2e⁻ content. - ORR performance.

[0058] Example 2:

[0059] (1) Weigh 4 mmol of selenium powder and add it to a beaker containing 30 mL of NaOH (4 g of NaOH, Chinese medicine) solution. Stir vigorously for 30 min to obtain mixture A.

[0060] (2) Weigh 2 mmol of cobalt nitrate hexahydrate and add it to a beaker containing 10 mL of 0.25 MEDTA-2Na solution. Stir vigorously for 30 min to obtain mixture B.

[0061] (3) Add mixture B to mixture A and stir for 10 min to obtain mixture C. Transfer mixture C to a reactor for hydrothermal reaction at a temperature of 200℃ for 6 h. After the hydrothermal reaction is completed, allow the reactor to cool naturally to room temperature. Then, centrifuge the product in the reactor and collect the black precipitate. Disperse the black precipitate in 100 mL of 0.1 mol / L hydrochloric acid solution and stir for 6 h. Then centrifuge. Repeat this process three times each time using 100 mL of 0.1 mol / L hydrochloric acid solution. Centrifuge with ultrapure water until the washing solution is neutral. Centrifuge parameters are 7500 rpm and centrifugation time is 4 min. After that, collect a large amount of black precipitate and place it in a vacuum drying oven at 60℃ for 24 h to obtain cobalt selenide powder.

[0062] (4) Weigh 1.0g of the cobalt selenide powder prepared in step (3) and add it to a beaker containing 100mL of anhydrous ethanol for dispersion. Then add 0.0896g of potassium thiocyanate white crystalline powder to the beaker and stir vigorously for 60min. Then transfer the beaker to a cell disruptor and sonicate at 40-50℃ for 4h with an ultrasonic power of 100W. Centrifuge the sonicated cobalt selenide dispersion at 7500rpm for 4min. Wash the precipitate five times with anhydrous ethanol. Then collect a large amount of black precipitate and transfer it to a vacuum drying oven to dry at 80℃ for 12h. Place the dried sample in a tube furnace and calcine at 300℃ (heating rate of 5℃ / min) for 2h in an air atmosphere to finally obtain cobalt selenide rich in double defects.

[0063] Example 3:

[0064] (1) Weigh 4 mmol of selenium powder and add it to a beaker containing 30 mL of NaOH (4 g of NaOH, Chinese medicine) solution. Stir vigorously for 30 min to obtain mixture A.

[0065] (2) Weigh 2 mmol of cobalt chloride and add it to a beaker containing 10 mL of 0.25 M EDTA-2Na solution. Stir vigorously for 30 min to obtain mixture B.

[0066] (3) Add mixture B to mixture A and stir for 30 min to obtain mixture C. Transfer mixture C to a reactor for hydrothermal reaction at a temperature of 200℃ for 6 h. After the hydrothermal reaction is completed, allow the reactor to cool naturally to room temperature. Then, centrifuge the product in the reactor and collect the black precipitate. Disperse the black precipitate in 100 mL of 0.1 mol / L hydrochloric acid solution and stir for 6 h. Then centrifuge. Repeat this process three times each time using 100 mL of 0.1 mol / L hydrochloric acid solution. Centrifuge with ultrapure water until the washing solution is neutral. Centrifuge parameters are 7500 rpm and centrifugation time is 4 min. After that, collect a large amount of black precipitate and place it in a vacuum drying oven at 60℃ for 24 h to obtain cobalt selenide powder.

[0067] (4) Weigh 1.0g of the cobalt selenide powder prepared in step (3) and add it to a beaker containing 100mL of anhydrous ethanol for dispersion. Then add 0.0448g of potassium thiocyanate white crystalline powder to the beaker and stir vigorously for 60min. Then transfer the beaker to a cell disruptor and sonicate at 40-50℃ for 4h with an ultrasonic power of 100W. Centrifuge the sonicated cobalt selenide dispersion at 7500rpm for 4min. Wash the precipitate five times with anhydrous ethanol. Then collect a large amount of black precipitate and transfer it to a vacuum drying oven to dry at 80℃ for 12h. Place the dried sample in a tube furnace and calcine at 300℃ (heating rate of 5℃ / min) for 2h in air atmosphere to finally obtain cobalt selenide rich in double defects.

[0068] Example 4:

[0069] (1) Weigh 4 mmol of selenium powder and add it to a beaker containing 30 mL of NaOH (4 g of NaOH, Chinese medicine) solution. Stir vigorously for 30 min to obtain mixture A.

[0070] (2) Weigh 2 mmol of cobalt acetate and add it to a beaker containing 10 mL of 0.25 M EDTA-2Na solution. Stir vigorously for 30 min to obtain mixture B.

[0071] (3) Add mixture B to mixture A and stir for 30 min to obtain mixture C. Transfer mixture C to a reactor for hydrothermal reaction at a temperature of 200℃ for 6 h. After the hydrothermal reaction is completed, allow the reactor to cool naturally to room temperature. Then, centrifuge the product in the reactor and collect the black precipitate. Disperse the black precipitate in 100 mL of 0.1 mol / L hydrochloric acid solution and stir for 6 h. Then centrifuge. Repeat this process three times each time using 100 mL of 0.1 mol / L hydrochloric acid solution. Centrifuge with ultrapure water until the washing solution is neutral. Centrifuge parameters are 7500 rpm and centrifugation time is 4 min. After that, collect a large amount of black precipitate and place it in a vacuum drying oven at 60℃ for 24 h to obtain cobalt selenide powder.

[0072] (4) Weigh 1.0g of the cobalt selenide powder prepared in step (3) and add it to a beaker containing 100mL of anhydrous ethanol for dispersion. Then add 0.1344g of potassium thiocyanate white crystalline powder to the beaker and stir vigorously for 60min. Then transfer the beaker to a cell disruptor and sonicate at 40-50℃ for 4h with an ultrasonic power of 100W. Centrifuge the sonicated cobalt selenide dispersion at 7500rpm for 4min. Wash the precipitate five times with anhydrous ethanol. Then collect a large amount of black precipitate and transfer it to a vacuum drying oven to dry at 80℃ for 12h. Place the dried sample in a tube furnace and calcine at 300℃ (heating rate of 5℃ / min) for 2h in air atmosphere to finally obtain cobalt selenide rich in double defects.

[0073] The above description is merely an embodiment of the present invention and is not intended to limit the present invention in any way. The present invention can also have other embodiments based on the above structure and function, which will not be listed hereafter. Therefore, any simple modifications, equivalent changes, and alterations made by those skilled in the art to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing cobalt selenide rich in dual defects, characterized in that... Specifically, the following steps are included: (1) Weigh a certain amount of selenium powder and add it to a NaOH solution with a concentration of 0.133 g / mL. Stir vigorously for 30-60 min to obtain mixture A; (2) Weigh a certain amount of cobalt metal salt and add it to a 0.25 mol / L EDTA-2Na solution. Stir vigorously for 30-60 min to obtain mixture B; (3) Add mixture B to mixture A and stir for 10-30 min to obtain mixture C. Transfer mixture C to a reactor for hydrothermal reaction. The temperature of the hydrothermal reaction is 200 °C and the reaction time is 6 h. After the hydrothermal reaction is completed, the reactor is naturally cooled to room temperature. Then, the product in the reactor is centrifuged and the black precipitate is collected and washed three times with hydrochloric acid solution. Then, it is washed with ultrapure water until the washing liquid is neutral. After that, the precipitate is collected and placed in a vacuum drying oven and dried at 60 °C for 12-20 h to obtain cobalt selenide powder. (4) Weigh a certain amount of cobalt selenide powder prepared in step (3), add it to a beaker containing anhydrous ethanol and disperse it, then add a certain amount of potassium thiocyanate powder to the beaker and stir vigorously for 30-60 min; then transfer the beaker to a cell disruptor and sonicate it at 40-50 ℃ for 2-4 h, centrifuge the dispersion after sonication, wash the precipitate with anhydrous ethanol five times, collect a large amount of black precipitate, transfer it to a vacuum drying oven and dry it at 80 ℃ for 12 h, place the dried sample in a tube furnace and calcine it at 300 ℃ for 2 h in an air atmosphere, and finally obtain cobalt selenide rich in double defects.

2. The method for preparing cobalt selenide rich in dual defects as described in claim 1, characterized in that... The cobalt salt mentioned in step (2) is one of cobalt nitrate, cobalt chloride, and cobalt acetate.

3. The method for preparing cobalt selenide rich in dual defects as described in claim 1, characterized in that... The molar ratio of selenium powder to cobalt salt is (1.8~2):

1.

4. The method for preparing cobalt selenide rich in dual defects as described in claim 1, characterized in that... The concentration of hydrochloric acid solution in step (3) is 0.5~2 mol / L.

5. The method for preparing cobalt selenide rich in dual defects as described in claim 1, characterized in that... The mass ratio of cobalt selenide powder to potassium thiocyanate powder added in step (4) is 1:(0.04~0.14).

6. The method for preparing cobalt selenide rich in dual defects as described in claim 1, characterized in that... In step (4), the ultrasonic power is 100~250 W, the centrifuge speed is 7500 rpm, and the centrifugation time is 4~6 min.

7. The method for preparing cobalt selenide rich in dual defects as described in claim 1, characterized in that... In step (4), the heating rate of the tube furnace is 5 °C / min.

8. The cobalt selenide material rich in dual defects prepared by the preparation method according to claim 1, characterized in that... It is in the shape of a nanorod, with a diameter of 40 nm and a length of 200 nm.

9. The application of the cobalt selenide material rich in dual defects prepared by the preparation method according to claim 1 in the electrocatalytic oxygen reduction to H2O2 production in acidic media.

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