Boron nitride-based zinc monatomic composite material as well as preparation method and application thereof

Abstract

The invention provides a boron nitride-based zinc monatomic composite material BN-Zn-CN as well as a preparation method and application thereof. The composite material has a sheet structure, graphene-like (N-doped C) grows in situ on the surface of BN, and monatomic Zn forms coordination with N and O to become a new active site for oxygen reduction reaction. The composite material is used as a catalyst for electrocatalytic oxygen reduction synthesis of H2O2, sufficient activation of O2 molecules is facilitated, and the electrocatalytic oxygen reduction reaction performance is improved. When the BN-Zn-CN is synthesized, the production process is simple, the catalyst cost is low, the H2O2 current is large, and the H2O2 selectivity is good.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalytic hydrogen peroxide synthesis, and in particular, to a boron nitride-based zinc single-atom composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Hydrogen peroxide (H2O2) is one of the 100 most important chemicals globally and is a multifunctional environmentally friendly oxidant. H2O2 is widely used in medical and industrial processes such as green chemical synthesis, wastewater treatment, fuel cells, and the paper industry. It is widely used as an environmental disinfectant. Currently, nearly 99% of H2O2 is produced by the indirect anthraquinone method. However, the basic equipment for this process is complex, consumes a large amount of energy, and generates a considerable amount of organic solvents when noble metal palladium is used as a catalyst. In addition, the equipment for producing H2O2 has high pollution, high transportation costs, and cannot be used on-site, and these characteristics do not reflect its inherent value in producing H2O2. Therefore, the electrocatalytic oxygen reduction reaction (ORR) to generate H2O2 as a green and clean on-site production method has attracted great interest. ORR occurs at the cathode, and O2 may undergo competitive reactions of 2e - (H2O2) and 4e - (H2O). The 2e - selective reaction is divided into O2 + 2H + + 2e - / H2O2 (acidic) or O2 + 2H2O + 2e - / HO2 - (alkaline). Electrocatalytic production of H2O2 is a very satisfactory method, which requires the selection of highly selective and highly active catalysts and equipment for on-site production of H2O2.

[0003] Currently, the catalysts for electrocatalytic production of H2O2 are noble metal-based and alloy materials (such as Pd-based, Pt-based, and Pd-Au), single-atom catalysts, and carbon-based materials. These catalysts exhibit high activity and selectivity in a wide voltage range. However, these catalysts have low reserves, complex processes, and poor stability, which hinder their large-scale application. Among them, non-metallic materials, such as carbon-based materials, have been widely studied due to their large reserves and adjustable structural properties and have been proven to be promising alternative materials. Given the general activity of pristine carbon, the surface properties of carbon materials should be adjusted to improve their electrocatalytic performance. For example, a series of model carbon catalysts are used to determine the active oxygen functional groups that are beneficial to 2e - ORR. It is necessary to adjust the oxygen-containing functional groups on the surface of carbon materials and add heteroatoms to the carbon materials to fully optimize their electrochemical H2O2 performance.

[0004] Recently, an emerging technology for synthesizing H2O2 based on the electrochemical oxygen reduction reaction (ORR) has received extensive attention due to its low energy consumption, environmental friendliness, and high efficiency. However, the instability of H2O2, which is prone to decomposition in an alkaline environment, severely restricts the application of this technology. With the in-depth research, the emergence of the electro-Fenton technology has partially broken through the production limitation of H2O2 under alkaline conditions and can play an important role in the degradation of organic pollutants. In recent years, the technology of preparing H2O2 by electrochemical two-electron oxygen reduction (2e - ORR) has become an emerging field and shown broad application prospects. This technology is expected to replace the high-energy-consuming anthraquinone process and provide solutions for achieving the goals of carbon peak and carbon neutrality. Through the raw materials of O2 and H2O in the air, the ORR technology can be used to produce small-sized, highly efficient, and low-energy-consuming "ready-to-use" H2O2, providing safe and low-cost solutions for disinfection in high-risk places such as hospitals, airports, and schools.

[0005] The two main paths of ORR include the four-electron generation of H2O and the two-electron generation of H2O2 reactions. 2e - The catalytic reaction of ORR is divided into two steps, and the adsorption strength of the *OOH intermediate is crucial for the generation of H2O2. Too weak adsorption force will inhibit the reaction, and too strong adsorption force will make it difficult to separate the generated H2O2. Therefore, it is crucial to select a suitable catalyst to improve the reaction activity and H2O2 selectivity. Currently, common 2e - ORR catalysts include noble metals, metal alloys, metal compounds, single-atom catalysts, and metal-free materials. Compared with noble metal-based catalysts, carbon-based materials have become the focus of research due to their rich reserves and low cost.

[0006] Currently, there is no report on the application of BN-Zn-CN single-atom composite materials in electrocatalytic synthesis of H2O2. Summary of the Invention

[0007] The purpose of the present invention is to provide a boron nitride-based zinc single-atom composite material, its preparation method, and application to solve the technical problems such as high post-treatment cost, serious pollution, and low reaction selectivity existing in the H2O2 synthesis process.

[0008] To achieve the above purpose, the present invention provides a boron nitride-based zinc single-atom composite material, its preparation method, and application.

[0009] 1. A preparation method of a boron nitride-based zinc single-atom composite material, the specific steps are as follows:

[0010] (1) First, grind boron nitride nanosheets (BNNS) evenly with potassium hydroxide (KOH) and sodium hydroxide (NaOH) to obtain a mixed powder; heat the mixed powder in a sealed manner for reaction, and perform post-treatment to obtain BN-OH;

[0011] (2) BN-OH and zinc nitrate hexahydrate are then placed in pure water, urea is added, the mixture is dispersed by stirring, and the mixture is dried by stirring in a water bath to obtain a white powder;

[0012] (3) adding the white powder into soybean oil and grinding thoroughly to obtain a grinding product;

[0013] (4) Finally, the ground product is transferred to a tubular furnace and calcined with nitrogen to achieve zinc atom coordination, thereby obtaining the composite material BN-Zn-CN.

[0014] Preferably, in step (1), the masses of the boron nitride nanosheets, potassium hydroxide and sodium hydroxide are 2 g, 4.1 g and 5.4 g, respectively, and the particle size of the boron nitride nanosheets is 100 nm.

[0015] Preferably, in step (1), the process conditions for the sealed heating reaction are: sealed heating reaction at 180° C. for 2 hours.

[0016] Preferably, in step (1), the post-treatment comprises: naturally cooling to room temperature, filtering out the filter residue, washing with distilled water until neutral, and vacuum drying.

[0017] Preferably, in step (2) and step (3), the usage ratio of pure water, BN-OH, zinc nitrate hexahydrate, urea and soybean oil is 50 mL: 0.25 g: 0.0298-0.18 g: 2 g: 5 g.

[0018] More preferably, the usage ratio of pure water, BN-OH, zinc nitrate hexahydrate and urea is 50 mL: 0.25 g: 0.0894 g: 2 g: 5 g.

[0019] Preferably, in step (2), the stirring and dispersing time is 30 minutes; and the process conditions for water bath stirring and drying are: 60° C., 350 rpm, stirring for 9 hours.

[0020] Preferably, in step (4), the calcination process conditions are: firstly heating to 550°C at 5°C / min, calcining for 1 hour, then heating to 800°C at 2°C / min, calcining for 2 hours.

[0021] 2. A boron nitride-based zinc single-atom composite material obtained by the aforementioned preparation method.

[0022] 3. Application of the aforementioned boron nitride-based zinc single-atom composite material in the preparation of hydrogen peroxide.

[0023] Preferably, the composite material is used as a catalyst for electrocatalytic oxygen reduction to synthesize hydrogen peroxide.

[0024] 4. A method for preparing hydrogen peroxide, using oxygen as a raw material and the above-mentioned composite material as a catalyst, and obtaining hydrogen peroxide through an electrocatalytic oxygen reduction reaction.

[0025] Preferably, a rotating ring-disk electrode (RRDE) is used as the working electrode, a graphite rod as the counter electrode, and Hg / HgO as the reference electrode. O2 is used as the reactant dissolved in an alkaline solution as the electrolyte; through the electrocatalytic oxygen reduction reaction, H2O2 is obtained.

[0026] More preferably, the alkaline solution is 0.1 mol / L potassium hydroxide solution.

[0027] More preferably, the conditions for the electrocatalytic oxygen reduction reaction are: the scanning voltage is 0 - 1 V vs. RHE, and the ring voltage is set to 1.5 V vs. RHE.

[0028] Preferably, the specific steps are as follows:

[0029] S1. First, add the aforementioned composite material into a mixed solution of water, isopropyl alcohol, and Nafion solution, and perform ultrasonic dispersion to obtain a catalyst slurry. The Nafion solution is from Suzhou Shengeruo Technology Co., Ltd.

[0030] S2. Use a rotating ring-disk electrode (RRDE), drop the catalyst slurry onto the glassy carbon disk, and dry it.

[0031] S3. Pass O2 into the alkaline solution of RRDE, and through the oxygen reduction reaction, obtain H2O2.

[0032] More preferably, in step S1, the dosage ratio of the composite material to the mixed solution is 5 mg: 1 mL, the volume ratio of water, isopropyl alcohol, and Nafion solution is 29: 20: 1, and the mass concentration of the Nafion solution is 5%.

[0033] More preferably, in step S1, the ultrasonic dispersion time is 30 minutes, and the vibration frequency is 250 kHz.

[0034] More preferably, in step S2, the dosage of the catalyst slurry is 50 μL.

[0035] More preferably, in step S3, the oxygen passing time is 30 minutes.

[0036] More preferably, in step S3, the alkaline solution is 0.1 mol / L KOH solution.

[0037] The present invention has the following beneficial effects:

[0038] The present invention provides a boron nitride-based zinc single-atom composite material BN-Zn-CN, its preparation method and application. The composite material has a flaky structure, with graphene-like (N-doped C) grown in-situ on the surface of BN. The single-atom Zn forms coordination with N and O, becoming a new active site for the oxygen reduction reaction. The present invention uses this composite material as a catalyst for electrocatalytic oxygen reduction to synthesize H2O2, which is beneficial to the full activation of O2 molecules and improves the performance of the electrocatalytic oxygen reduction reaction. When synthesizing BN-Zn-CN in the present invention, the production process is simple, the catalyst cost is low, the H2O2 current is large, and the H2O2 selectivity is good.

[0039] The specific advantages of the present invention are as follows:

[0040] (1) High catalytic activity: Due to its unique structure and composition, the BN-Zn-CN single-atom composite material exhibits high catalytic activity (E = 0V RHE , H2O2 current = 1.94 mA / cm 2 ). The presence of single-atom Zn not only provides more active sites but also enhances the interaction between the catalyst and the reactants, thus improving the efficiency of the electrocatalytic oxygen reduction reaction. At the same time, compared with the comparative example, the interaction between Zn, BN, and graphene-like is beneficial to the adsorption and activation of O2 on the catalyst surface, enhancing the performance of O2 electroreduction to H2O2;

[0041] (2) High selectivity: During the electrocatalytic reduction of O2, the BN-Zn-CN single-atom composite material can effectively promote the generation of the target product H2O2 while suppressing the formation of by-products (H2O2 selectivity 90%).

[0042] (3) Good stability: The BN-Zn-CN single-atom composite material has good stability and can maintain its catalytic activity and selectivity during a long reaction process. This stability not only ensures the continuity and repeatability of the reaction but also extends the service life of the catalyst;

[0043] (4) Green and environmentally friendly: The electrocatalytic reduction method itself is a green and environmentally friendly synthesis technology that uses renewable electrical energy to drive the reaction, reducing carbon emissions from fossil fuels. The use of the BN-Zn-CN single-atom composite material further enhances this environmental friendliness because it avoids the use of toxic or precious metal catalysts and reduces waste and pollutant generation.

[0044] In addition to the purposes, features, and advantages described above, the present invention has other purposes, features, and advantages. The following will further describe the present invention in detail with reference to the drawings. Description of the Drawings

[0045] The accompanying drawings, which form a part of this application, are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0046] Figure 1 are the Raman spectra of the composite materials obtained in Example 1 and Comparative Examples 1 and 2;

[0047] Figure 2 is the transmission electron microscope image of the composite material obtained in Example 1;

[0048] Figure 3 is the graph of the change of the reaction current of electrocatalytic oxygen reduction of O2 to H2O2 with potential for the composite materials obtained in Example 1 and Comparative Examples 1 and 2. Detailed Description of the Invention

[0049] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways defined and covered by the claims.

[0050] Example 1: Synthesis of 1% BN-Zn-CN Catalyst and Study on Its Electrocatalytic Production Performance of H2O2

[0051] (1) Take 2 g of commercial hexagonal BN (raw-BN, 100 nm, flaky) and mix it with 4.1 g of KOH and 5.4 g of NaOH, and grind them into a powder;

[0052] (2) Seal and heat the reaction at 180 °C for 2 hours, cool to room temperature, perform suction filtration, wash the filter residue with distilled water, and then freeze-dry at -54 °C to obtain BN-OH;

[0053] (3) Weigh 0.25 g of BN-OH, 0.0298 g of Zn(NO3)2·6H2O and 2 g of urea, add deionized water and stir for 30 min. Stir and dry under water bath (60 °C, stir at 350 rpm for 9 hours) to obtain a solid powder.

[0054] (4) Put the solid powder in (3) into a porcelain boat, wrap it with tin foil, grind it with 5 g of soybean oil in a nitrogen atmosphere and calcine it at 550 °C for 1 h, then raise the temperature to 800 °C and calcine it for 2 h. After cooling to room temperature, the obtained composite material is finally obtained, denoted as BN-Zn-CN.

[0055] For the Raman spectrum of the 1% BN-Zn-CN catalyst obtained in Example 1 ( Figure 1 ), the D peak (around 1356 cm -1 ) and G peak (around 1578 cm -1 ) of the graphite carbon structure appear, corresponding to defective carbon and graphite carbon respectively. In addition, a strong 2D band (2500 - 2800 cm-1 ) is a remarkable feature of the graphene structure, while the Raman spectrum of BN only shows characteristic peaks caused by the E2g vibration mode, located near 1359 cm -1 . These results prove the formation of the graphene structure. As can be seen from the scanning electron microscope (TEM) images in Figure 2 , there are distorted lattice fringes on the surface of BN-Zn-CN, indicating that the graphene structure has grown successfully on the BN surface, corroborating the results of the Raman spectrum. The presence of Zn-related nanoparticles was not observed. The RRDE polarization curve is shown in Figure 3 .

[0056] The catalytic performance of the 1% BN-Zn-CN catalyst prepared in Example 1 was tested as follows:

[0057] Weigh 5 mg of the prepared BN-Zn-CN catalyst powder and add it to a mixed solution of 400 μL of isopropanol, 600 μL of deionized water, and 20 μL of Nafion solution (the mass fraction of the Nafion solution is 5%). Sonicate for 30 min at a vibration frequency of 250 kHz to completely disperse the catalyst and obtain a homogeneous catalyst slurry. Take 50 μL of the dispersed catalyst slurry and evenly drop-coat it on a glass disk, dry it, and directly use it as the working electrode (i.e., the material with the BN-Zn-CN catalyst coated on the glass disk is used as the working electrode). Control the O2 flow rate with a flow meter and carry out the reaction using an H-cell reactor. Load 0.25 mg of the catalyst on fluorine-doped tin oxide (FTO, 1×2.5 cm) as the working electrode, and the electrolyte is 150 mL of 0.1 M KOH (75 mL in each electrolysis chamber). A ZF-500 anion exchange membrane is used as the diaphragm between the anode and cathode chambers. CV activation is carried out in an O2-saturated electrolyte, and chronoamperometry is carried out at a constant potential of 0.4 V RHE (without iR correction). During this period, keep O2 fed into the electrode chamber at a constant rate to generate H2O2. Use 0.1 mol / L KOH solution as the reaction solution; use a rotating ring-disk electrode (RRDE) as the working electrode, a graphite rod as the counter electrode, and Hg / HgO as the reference electrode. Use O2 as the reactant dissolved in the alkaline solution as the electrolyte.

[0058] S1: Feed O2 with a flow rate of 100 SCCM into the electrolytic solution;

[0059] S2: Set the scanning CV activation scanning speed to 50 mV / s, and the scanning range to 1.0 V RHE~0 V RHE.

[0060] S3: Dissolve 20.2 mg of Ce(SO4)2 . 4H2O in 100 mL of 0.5 M H2SO4 solution to form a yellow transparent Ce(SO4)2 solution.

[0061] S4: Take 50 μL of the electrolytic solution in the cathode chamber in step S2 every 1 h, add 3 mL of cerium sulfate product, and measure it by ultraviolet spectrophotometry. Measure the absorbance curve. Compare the absorbance value of the obtained curve at 320.2 nm with the standard curve.

[0062] Example 2: Synthesis of 3% BN-Zn-CN Catalyst and Study on Its Electrocatalytic H2O2 Production Performance

[0063] (1) Take 2 g of commercial hexagonal BN (raw-BN, 100 nm, flaky), mix it with 4.1 g of KOH and 5.4 g of NaOH, and grind them into a powder.

[0064] (2) Seal and heat the reaction at 180 °C for 2 hours, cool it to room temperature, perform suction filtration. After washing the filter residue with distilled water, then freeze-dry it at -54 °C to obtain BN-OH.

[0065] (3) Weigh 0.25 g of BN-OH, 0.0894 g of Zn(NO3)2·6H2O and 2 g of urea, add deionized water and stir for 30 min. Stir and dry it under water bath (stir at 60 °C and 350 rpm for 9 hours) to obtain a solid powder.

[0066] (4) Put the solid powder in (3) into a porcelain boat, wrap it with tin foil, add 5 g of soybean oil and grind it in a nitrogen atmosphere, then calcine it at 550 °C for 1 h, raise the temperature to 800 °C and calcine it for 2 h. After cooling to room temperature, finally obtain the composite material, denoted as BN-Zn-CN.

[0067] Test the catalytic performance of the 3% BN-Zn-CN catalyst prepared in Example 2. The specific method is as follows:

[0068] Weigh 5 mg of the prepared BN-Zn-CN catalyst powder and add it to a mixed solution of 400 μL of isopropanol, 600 μL of deionized water, and 20 μL of Nafion solution (the mass fraction of the Nafion solution is 5%). Ultrasonicate for 30 min at a vibration frequency of 250 kHz to completely disperse the catalyst and obtain a uniform catalyst slurry. Take 50 μL of the well-dispersed catalyst slurry and evenly drop-coat it on a glass disk, then dry it to directly serve as the working electrode (i.e., the material with the BN-Zn-CN catalyst coated on the glass disk serves as the working electrode). Control the O2 flow rate with a flow meter and carry out the reaction using an H-cell reactor. Load 0.25 mg of the catalyst on fluorine-doped tin oxide (FTO, 1×2.5 cm) as the working electrode, and use 150 mL of 0.1 M KOH (75 mL in each electrolytic cell) as the electrolyte. A ZF-500 anion exchange membrane serves as the diaphragm between the anode and cathode chambers. CV activation is carried out in an O2-saturated electrolyte, and chronoamperometry is carried out at a constant potential of 0.4 V RHE (without iR correction). During this period, keep O2 fed into the electrode chamber at a constant rate to produce H2O2. Use 0.1 mol / L KOH solution as the reaction solution; use a rotating ring-disk electrode (RRDE) as the working electrode, a graphite rod as the counter electrode, and Hg / HgO as the reference electrode, and use O2 as the reactant dissolved in the alkaline solution as the electrolyte.

[0069] S1: Feed O2 with a flow rate of 100 SCCM into the electrolytic solution;

[0070] S2: Set the scanning speed of CV activation to 50 mV / s and the scanning range to 1.0 V RHE to 0 V RHE.

[0071] S3: Dissolve 20.2 mg of Ce(SO4)2 . 4H2O in 100 mL of 0.5 M H2SO4 solution to form a yellow transparent Ce(SO4)2 solution.

[0072] S4: Take 50 μL of the electrolytic solution in the cathode chamber of step S2 every 1 h, add 3 mL of cerium sulfate product, and measure it by ultraviolet spectrophotometry. Measure the absorbance curve. Compare the absorbance value of the obtained curve at 320.2 nm with the standard curve.

[0073] Example 3: Synthesis of 6% BN-Zn-CN Catalyst and Study on Its Electrocatalytic H2O2 Production Performance

[0074] (1) Take 2 g of commercial hexagonal BN (raw-BN, 100 nm, flaky) and mix it with 4.1 g of KOH and 5.4 g of NaOH, and grind them into a powder;

[0075] (2) Heat the reaction mixture under sealed conditions at 180 °C for 2 hours, cool it to room temperature, perform suction filtration, wash the filter residue with distilled water, and then freeze-dry it at -54 °C to obtain BN-OH.

[0076] (3) Weigh 0.25 g of BN-OH, 0.18 g of Zn(NO3)2·6H2O, and 2 g of urea, add them to deionized water, and stir for 30 min. Stir and dry under a water bath (stir at 60 °C and 350 rpm for 9 hours) to obtain a solid powder.

[0077] (4) Put the solid powder in (3) into a porcelain boat, wrap it with tin foil, grind it with 5 g of soybean oil in a nitrogen atmosphere, and calcine it at 550 °C for 1 h, then raise the temperature to 800 °C and calcine it for 2 h. After cooling to room temperature, finally obtain the; composite material, denoted as BN-Zn-CN.

[0078] Test the catalytic performance of the 5% BN-Zn-CN catalyst prepared in Example 3. The specific method is as follows:

[0079] Weigh 5 mg of the prepared BN-Zn-CN catalyst powder, add it to a mixed solution of 400 μL of isopropanol, 600 μL of deionized water, and 20 μL of Nafion solution (the mass fraction of the Nafion solution is 5%), and ultrasonicate for 30 min at a vibration frequency of 250 kHz to completely disperse the catalyst and obtain a uniform catalyst slurry. Take 50 μL of the dispersed catalyst slurry and evenly drop-coat it on a glass disk, dry it, and directly use it as a working electrode (that is, the material with the BN-Zn-CN catalyst coated on the glass disk is used as the working electrode). Control the O2 flow rate by a flow meter, perform the reaction using an H-cell reactor, load 0.25 mg of the catalyst on fluorine-doped tin oxide (FTO, 1×2.5 cm) as the working electrode, and use 150 mL of 0.1 M KOH (75 mL in each electrolytic cell) as the electrolyte. A ZF-500 anion exchange membrane is used as the diaphragm between the anode and cathode chambers. CV activation is carried out in an O2-saturated electrolyte, and chronoamperometry is carried out at a constant potential of 0.4 V RHE (without iR correction). During this period, keep O2 fed into the electrode chamber at a constant rate to produce H2O2. Use 0.1 mol / L KOH solution as the reaction solution; use a rotating ring-disk electrode (RRDE) as the working electrode, a graphite rod as the counter electrode, and Hg / HgO as the reference electrode, and use O2 as the reactant dissolved in the alkaline solution as the electrolyte.

[0080] S1: Feed O2 with a flow rate of 100 SCCM into the electrolytic solution;

[0081] S2: Set the scanning speed of CV activation to 50 mV / s, and the scanning range to 1.0 V RHE to 0 V RHE.

[0082] S3: Dissolve 20.2 mg of Ce(SO4)2 . 4H2O in 100 mL of 0.5 M H2SO4 solution to form a yellow transparent Ce(SO4)2 solution.

[0083] S4: Take 50 μL of the electrolyzed solution in the cathode chamber of step S2 every 1 h, add 3 mL of cerium sulfate product, and measure it by ultraviolet spectrophotometry. Measure the absorbance curve. Compare the absorbance value of the obtained curve at 320.2 nm with the standard curve.

[0084] Comparative Example 1: Synthesis of BN-CN catalyst and study on its electrocatalytic performance for H2O2 production

[0085] (1) Take 2 g of commercial hexagonal BN (raw-BN, 100 nm, flaky) and mix it with 4.1 g of KOH and 5.4 g of NaOH, and grind them into a powder;

[0086] (2) Heat and react hermetically at 180 °C for 2 hours, cool to room temperature, perform suction filtration, wash the filter residue with distilled water, and then freeze-dry it at -54 °C to obtain BN-OH;

[0087] (3) Weigh 0.25 g of BN-OH and 2 g of urea, add deionized water, and stir for 30 min. Stir and dry it under water bath (stir at 60 °C and 350 rpm for 9 hours) to obtain a solid powder.

[0088] (4) Put the solid powder in (3) into a porcelain boat, wrap it with tin foil, grind it with 5 g of soybean oil in a nitrogen atmosphere, and calcine it at 550 °C for 1 h, then raise the temperature to 800 °C and calcine it for 2 h. After cooling to room temperature, finally obtain the composite material, denoted as BN-CN.

[0089] Weigh 5 mg of the prepared BN-CN catalyst powder and add it to a mixed solution of 400 μL of isopropanol, 600 μL of deionized water, and 20 μL of Nafion solution (the mass fraction of the Nafion solution is 5%). Ultrasonic for 30 min with a vibration frequency of 250 kHz to completely disperse the catalyst and obtain a uniform catalyst slurry. Take 50 μL of the dispersed catalyst slurry and evenly drop-coat it on a glass disk, dry it, and directly use it as a working electrode (that is, the material with the BN-CN catalyst coated on the glass disk is used as the working electrode). Control the O2 flow rate by a flow meter. Use an H-cell reactor for the reaction. Load 0.25 mg of the catalyst on fluorine-doped tin oxide (FTO, 1×2.5 cm) as the working electrode, and the electrolyte is 150 mL of 0.1 M KOH (75 mL for each electrolytic cell). A ZF-500 anion exchange membrane is used as the diaphragm between the anode and cathode chambers. CV activation is carried out in an O2-saturated electrolyte. Chronoamperometry is carried out at a constant potential of 0.4 V RHE (without iR correction). During this period, keep O2 fed into the electrode chamber at a constant rate to generate H2O2. Use 0.1 mol / L KOH solution as the reaction solution; use a rotating ring-disk electrode (RRDE) as the working electrode, a graphite rod as the counter electrode, and Hg / HgO as the reference electrode. Use O2 as the reactant dissolved in the alkaline solution as the electrolyte.

[0090] S1: Feed O2 with a flow rate of 100 SCCM into the electrolytic solution;

[0091] S2: Set the scanning speed of CV activation scanning to 50 mV / s, and the scanning range to 1.0 V RHE~0 V RHE.

[0092] S3: Dissolve 20.2 mg of Ce(SO4)2 . 4H2O in 100 mL of 0.5 M H2SO4 solution to form a yellow transparent Ce(SO4)2 solution.

[0093] S4: Take 50 μL of the electrolytic solution in the cathode chamber in step S2 every 1 h, add 3 mL of cerium sulfate, and measure the product by ultraviolet spectrophotometry. Measure the absorbance curve. Compare the absorbance value of the obtained curve at 320.2 nm with the standard curve.

[0094] The Raman spectrogram is shown in Figure 1 and the RRDE polarization curve is shown in Figure 3 .

[0095] Comparative Example 2: Synthesis of BN catalyst and study on its electrocatalytic performance for producing H2O2

[0096] (1) Mix 2 g of commercial hexagonal BN (raw - BN, 100 nm, flaky) with 4.1 g of KOH and 5.4 g of NaOH, and grind them into a powder.

[0097] (2) Heat the mixture in a sealed container at 180 °C for 2 hours, cool it to room temperature, perform suction filtration. After washing the filter residue with distilled water, then freeze - dry it at - 54 °C to obtain the BN catalyst.

[0098] Weigh 5 mg of the prepared BN catalyst powder and add it to a mixed solution of 400 μL of isopropanol, 600 μL of deionized water, and 20 μL of Nafion solution (the mass fraction of the Nafion solution is 5%). Ultrasonicate for 30 min at a vibration frequency of 250 kHz to completely disperse the catalyst and obtain a homogeneous catalyst slurry. Take 50 μL of the dispersed catalyst slurry and evenly drop - coat it on a glass disk, then dry it to directly serve as the working electrode (that is, the material with the BN catalyst coated on the glass disk serves as the working electrode). Control the O2 flow rate with a flow meter. Use an H - cell reactor for the reaction. Load 0.25 mg of the catalyst on fluorine - doped tin oxide (FTO, 1×2.5 cm) as the working electrode, and the electrolyte is 150 mL of 0.1 M KOH (75 mL for each electrolysis chamber). A ZF - 500 anion - exchange membrane serves as the diaphragm between the anode and cathode chambers. CV activation is carried out in an O2 - saturated electrolyte, and chronoamperometry is carried out at a constant potential of 0.4 V RHE (without iR correction). During this period, keep O2 fed into the electrode chamber at a constant rate to generate H2O2. Use 0.1 mol / L KOH solution as the reaction solution; use a rotating ring - disk electrode (RRDE) as the working electrode, a graphite rod as the counter electrode, and Hg / HgO as the reference electrode. Use O2 as the reactant dissolved in the alkaline solution as the electrolyte.

[0099] S1: Feed O2 with a flow rate of 100 SCCM into the electrolytic solution.

[0100] S2: Set the scanning speed of CV activation to 50 mV / s, and the scanning range to 1.0 V RHE~0 V RHE.

[0101] S3: Dissolve 20.2 mg of Ce(SO4)2·4H2O in 100 mL of 0.5 M H2SO4 solution to form a yellow - transparent Ce(SO4)2 solution.

[0102] S4: Take 50 μL of the electrolytic solution in the cathode chamber every 1 h in step S2, add 3 mL of cerium sulfate product, and measure it by ultraviolet spectrophotometry. Determine the absorbance curve. Compare the absorbance value of the obtained curve at 320.2 nm with the standard curve.

[0103] The Raman spectrum is shown in Figure 1, RRDE polarization curves are shown in Figure 3 .

[0104] The Raman spectra of BN-CN and BN-Zn-CN showed the D peak of graphite carbon structure (1356 cm -1 Nearby) and G Peak (1578cm -1 ), corresponding to defective carbon and graphite carbon, respectively. The ID / IG values ​​of the two materials are similar. In addition, there is an obvious 2D band (2500-2800cm -1 ), which is the interlayer stacking of graphite carbon atoms and is a significant feature of graphene structure, while the Raman spectrum of BN only shows a characteristic peak caused by the E2g vibration mode, located at 1359cm -1 These results demonstrate the formation of graphene structures.

[0105] Figure 3 :The solid line is the ORR current density (jdisk) on the disk electrode, and the dotted line is the H2O2 oxidation current (Iring) on ​​the Pt ring. In this system, BN exhibits the smallest jdisk and Iring, indicating that BN exhibits the worst ORR and H2O2 production performance under alkaline conditions. However, it still has considerable HO2 - % (81.8%, electron transfer number 2.36, E = 0.4 VRHE), this is because BN has a weak adsorption of O2, which makes the dissociation of *OOH into *O and *OH thermodynamically unfavorable, promoting the reaction to 2e - The low jdisk is attributed to the poor conductivity of BN. In situ growth of graphene-like structures (BNCN) on the BN surface can enhance the conductivity and significantly improve its ORR performance. At a potential of 0.4 VRHE, jdisk increased from 0.798 mA / cm 2 Increased to 1.090mA / cm 2 , while Iring barely improved, HO2 - % decreased to 70.5%, indicating that BN-CN is more likely to occur in 4e - ORR. This may be because there are more pyridinic-N in the graphene-like structure, and the carbon atoms adjacent to it are considered to be the direct source of ORR activity. After the introduction of Zn single atoms to form O Zn-N3 coordination (BN-Zn-CN), Iring increased significantly, reaching 0.087 mA at 0.4VRHE, much larger than BN (0.052 mA) and BN-CN (0.056 mA), and HO2-% was 91.5% (electron transfer number 2.17), which is better than BN and BN-CN (HO2-% is 70.5%, electron transfer number 2.59). This result proves that O-Zn-N3 coordination is 2e - The activity of ORR plays an important role.

[0106] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a boron nitride-based zinc single-atom composite material, characterized in that: The specific steps are as follows: (1) firstly mixing boron nitride nanosheets with potassium hydroxide and sodium hydroxide and grinding them uniformly to obtain a mixed powder; the mixed powder is sealed and heated for reaction, and then post-treated to obtain BN-OH; (2) BN-OH and zinc nitrate hexahydrate are then placed in pure water, urea is added, the mixture is dispersed by stirring, and the mixture is dried by stirring in a water bath to obtain a white powder; (3) adding the white powder into soybean oil and grinding thoroughly to obtain a grinding product; (4) Finally, the ground product is transferred to a tubular furnace and calcined with nitrogen to achieve zinc atom coordination, thereby obtaining the composite material BN-Zn-CN.

2. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of boron nitride nanosheets, potassium hydroxide and sodium hydroxide is 2:4.1:5.4, and the particle size of the boron nitride nanosheets is 100 nm.

3. The preparation method according to claim 1, characterized in that: In step (1), the process conditions for the sealed heating reaction are: sealed heating reaction at 180° C. for 2 hours.

4. The preparation method according to claim 1, characterized in that: In step (2) and step (3), the usage ratio of pure water, BN-OH, zinc nitrate hexahydrate, urea and soybean oil is 50mL:0.25g:0.0298~0.18g:2g:5g.

5. The preparation method according to claim 1, characterized in that: In step (4), the calcination process conditions are: firstly increase the temperature to 550°C at 5°C / min, calcine for 1 hour, then increase the temperature to 800°C at 2°C / min, and calcine for 2 hours.

6. A boron nitride-based zinc single-atom composite material, characterized in that: The invention is obtained by the preparation method according to any one of claims 1 to 5.

7. Use of the boron nitride-based zinc single-atom composite material according to claim 6 in the preparation of hydrogen peroxide.

8. The use according to claim 7, characterized in that: The composite material according to claim 6 is used as a catalyst for electrocatalytic oxygen reduction to synthesize hydrogen peroxide.

9. A method for preparing hydrogen peroxide, characterized in that: Oxygen is used as a raw material and the composite material described in claim 6 is used as a catalyst to obtain hydrogen peroxide through an electrocatalytic oxygen reduction reaction.

10. The preparation method according to claim 9, characterized in that: A rotating ring disk electrode was used as the working electrode, a graphite rod as the counter electrode, Hg / HgO as the reference electrode, and O2 as the reactant dissolved in an alkaline solution as the electrolyte; H2O2 is obtained through electrocatalytic oxygen reduction reaction.

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