Preparation method and application of carbon material containing carboxylated boron nitride

Abstract

The present invention relates to a preparation method and application of a carbon material containing carboxylated boron nitride, belonging to the field of catalyst technology. The present invention provides a preparation method and application of a carbon material containing carboxylated boron nitride. The catalyst is a novel h-BN region with carboxyl functionalization; the catalyst can achieve a high production rate of 13400mmol g in a neutral electrolyte. ‑1 h ‑1 The catalyst can operate stably at high current density and produce a high mass concentration of hydrogen peroxide solution, reaching 2.1wt.%.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts and relates to a preparation method and application of a carbon material containing carboxylated boron nitride. Background Art

[0002] Hydrogen peroxide (H2O2), an environmentally friendly and highly efficient oxidant, has a wide range of applications in the textile industry, industrial intermediate synthesis, wastewater treatment (disinfection and sterilization), pulp bleaching, semiconductor cleaning, and fuel cells. According to data, the global hydrogen peroxide market was worth US$2.44 billion in 2016 and is expected to reach US$3.68 billion by the end of 2025, with a compound annual growth rate (CAGR) of 4.7%. Consequently, the production of H2O2 has become a hot topic in social research. Currently, H2O2 is produced industrially using the anthraquinone oxidation method. Its greatest advantage is that hydrogen and oxygen do not come into contact, preventing gas explosions and offering high safety. However, this process requires large-scale centralized production equipment, generates a large amount of byproducts, and poses significant safety risks during transportation and storage of these highly concentrated hydrogen peroxide solutions (20% to 30% by weight). To conserve energy, reduce costs, and build a sustainable society, green, environmentally friendly, and efficient H2O2 production has become a major research focus. In addition to the anthraquinone method used in industrial production of H2O2, current H2O2 production methods also include direct synthesis, photocatalytic oxygen reduction, electrocatalytic oxygen reduction and electrocatalytic water oxidation. - ORR) is a green, environmentally friendly and sustainable method with the advantages of simple equipment (electrolytic cell), mild operating conditions (normal temperature and pressure), simple experimental process, and the prepared H2O2 concentration can meet daily needs.

[0003] In the electrocatalytic oxygen reduction process (2e - In ORR, the catalysts involved include metal alloys, metal oxides, covalent organic frameworks (COFs), metal organic frameworks (MOFs), porous carbon materials and their derivatives. Carbon catalysts have attracted widespread attention due to their abundance of earth elements, low cost, renewability, strong conductivity, good stability and easy adjustment of structure and function. In particular, the metal-free nature of carbon catalysts makes them suitable for fields such as medicine and water treatment. People have been working hard to improve the performance of carbon catalysts in 2e -The activity and selectivity of the ORR process are often enhanced by doping heteroatoms such as B, N, S, and P into carbon materials as active sites and adjusting the charge distribution around the carbon atoms to obtain better activity and selectivity. In particular, due to their different electronegativity, B and N atoms are doped into the conjugated carbon skeleton to form a boron nitride / graphitized heterojunction (h-BN / G structure, such as BN-C1 and G / h-BN), which effectively adjusts the electronic structure of the material and improves the hydrogen peroxide generation ability (J.Am.Chem.Soc.2018,140,7851-7859; Carbon Energy,2022;5,e309). Oxygen-containing functional groups also help to improve the 2e - In this context, surface oxidation methods have been used to introduce specific oxygen functional groups to improve ORR selectivity, such as oxidized carbon nanotubes (OCNTs) and oxidized folded graphene (OCGs) (Nat. Catal., 2018, 1, 156–162; Energy Environ. Sci., 2022, 15, 2858–2866). However, in the application of carbon-catalyzed electrochemical oxygen reduction to hydrogen peroxide, the coupling effect of heteroatom doping and surface functionalization is still under exploration.

[0004] In the existing technology, the hydrogen peroxide electrosynthesis method under neutral conditions has the advantages of inhibiting the decomposition of hydrogen peroxide and slowing down the corrosion of equipment, which is beneficial to the storage and transportation of the product. However, the neutral electrolyte usually has a low ion concentration, resulting in high ohmic loss, 2e - The ORR reaction kinetics are slow, making it difficult to achieve high-performance production. At the same time, due to the lack of low-cost, high-performance electrocatalysts, it is difficult to produce at industrially relevant current densities (>100 mA cm -2 However, the practical application of hydrogen peroxide is still hindered by the need to maintain high productivity and Faradaic efficiency (FE) under high pressure and high temperature conditions to achieve large-scale accumulation of hydrogen peroxide. Therefore, it is crucial to develop a catalyst with high activity and stability. Summary of the Invention

[0005] In order to overcome the defects of the prior art, the present invention provides a preparation method and application of a carbon material containing carboxylated boron nitride. The specific technical solution is as follows:

[0006] A carbon material containing carboxylated boron nitride, the material having a carboxyl-functionalized h-BN region, forming an h-BN / G heterojunction structure; in an embodiment of the present invention, a CBNO catalyst (wherein C represents activated carbon, B represents boric acid, N represents dicyandiamide, and O represents nitric acid treatment) is prepared by:

[0007] S1, mixing activated carbon, dicyandiamide and boric acid, and then grinding;

[0008] S2, heating the product obtained in S1;

[0009] S3, acid-etching the cooled S2 product; then washing with water until the pH is neutral and drying to obtain the product.

[0010] In the present invention, the activated carbon, dicyandiamide and boric acid in S1 are mixed in a mass ratio of 1:1:(1-4).

[0011] In the present invention, the grinding treatment in S1 is to grind the mixed activated carbon, dicyandiamide and boric acid until the solid particle size is ≤2 μm.

[0012] In the present invention, the heating treatment of S2 is to heat the product to 800-1100° C. at a heating rate of 1-5° C. / min, and then calcine under this condition for 2-4 hours.

[0013] In the present invention, the acid etching treatment of S3 is carried out using a dilute acid solution, condensed under reflux at 70-90° C. for 24-36 hours; the dilute acid solution is a dilute nitric acid, dilute sulfuric acid or dilute hydrochloric acid solution with a concentration of 3-5 mol / L.

[0014] In the embodiments of the present invention, the preparation processes of the reference catalysts CNO, CBO, and CBN are provided. The preparation process of the reference catalysts differs from the preparation process of CBNO in that:

[0015] When preparing CNO (wherein C represents activated carbon, N represents dicyandiamide, and O represents nitric acid treatment), no boric acid raw material is added in step 1;

[0016] When preparing CBO (wherein C represents activated carbon, B represents boric acid, and O represents nitric acid treatment), no dicyandiamide raw material is added in step 1;

[0017] When preparing CBN (wherein C represents activated carbon, B represents boric acid, and N represents dicyandiamide), hydrochloric acid is used instead of nitric acid in step three.

[0018] A method for preparing hydrogen peroxide uses a carbon material containing carboxylated boron nitride as a catalyst. The catalyst is prepared by acid etching a carbon material co-doped with nitrogen and boron.

[0019] A method for preparing hydrogen peroxide by using an electrocatalytic redox method adopts a carbon material containing carboxylated boron nitride as a catalyst. The catalyst is prepared by acid etching a nitrogen and boron co-doped carbon material.

[0020] Beneficial effects

[0021] The beneficial effects of the present invention are:

[0022] (1) A novel, efficient and inexpensive activated carbon catalyst with carboxyl-functionalized h-BN regions was synthesized;

[0023] (2) A high production rate of 13400 mmol g was achieved in neutral electrolyte. -1 h -1 ;

[0024] (3) It can operate stably at high current density and produce a high mass concentration of hydrogen peroxide solution, with a cumulative concentration of up to 2.1 wt.%. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of CBNO synthesis

[0026] Figure 2 Scanning electron micrograph of CBNO

[0027] Figure 3 Transmission electron microscopy image of CBNO

[0028] Figure 4 Enlarged transmission electron microscope image of CBNO

[0029] Figure 5 XRD diffraction patterns of CBNO, CBN, CBO, CNO and AC

[0030] Figure 6 Raman spectra of CBNO, CBN, CBO, CNO and AC

[0031] Figure 7 Infrared spectra of CBNO, CBN, CBO, CNO and AC

[0032] Figure 8 B1s XPS patterns of CBNO and CBN

[0033] Figure 9 N1s XPS patterns of CBNO and CBN

[0034] Figure 10 C1s XPS patterns of CBNO and CBN

[0035] Figure 11 O1s XPS images of CBNO and CBN

[0036] Figure 12 B-edge X-ray absorption fine structure (NEXAFS) spectra of CBN, boron nitride, and CBNO

[0037] Figure 13 N-edge X-ray absorption fine structure (NEXAFS) spectra of CBN, boron nitride, and CBNO

[0038] Figure 14 O-edge X-ray absorption fine structure (NEXAFS) spectra of CBN, boron nitride, and CBNO

[0039] Figure 15 Ring-disk electrode test diagram for CBNO, CBN, CBO, CNO and AC

[0040] Figure 16 according to Figure 14 Calculated selectivity of different samples

[0041] Figure 17 according to Figure 14 Calculated Tafel slopes for different samples

[0042] Figure 18 Linear sweep voltammetry curves of CBNO in oxygen and nitrogen atmospheres

[0043] Figure 19 Linear sweep voltammetry curves of CBNO in H-type cell and flow cell

[0044] Figure 20 Comparison with the production rate of reported catalysts

[0045] Figure 21 The total amount of hydrogen peroxide generated after CBNO electrolysis for 24 hours

[0046] Figure 22 Comparison with the total amount of hydrogen peroxide generated by reported catalysts

[0047] Figure 23 Production rate and performance diagram of samples calcined at 800℃

[0048] Figure 24 Production rate and performance diagram of samples calcined at 900℃

[0049] Figure 25 Production rate and performance diagram of samples calcined at 1000℃

[0050] Figure 26 Production rate and performance diagram of samples calcined at 1100℃

[0051] Figure 27 Production rate and performance diagram of samples treated with nitric acid for 12 hours

[0052] Figure 28 Production rate and performance diagram of samples treated with nitric acid for 24 hours

[0053] Figure 29 Production rate and performance diagram of samples treated with nitric acid for 36 hours

[0054] Figure 30 Production rate and performance diagram of samples treated with nitric acid for 48 hours

[0055] Figure 31 Production rate and performance diagram of the sample with activated carbon: dicyandiamide: boric acid = 1:1:1

[0056] Figure 32 Production rate and performance diagram of the sample of activated carbon: dicyandiamide: boric acid = 1:1:2

[0057] Figure 33 Production rate and performance diagram of the sample with activated carbon: dicyandiamide: boric acid = 1:1:3

[0058] Figure 34 Production rate and performance diagram of the sample of activated carbon: dicyandiamide: boric acid = 1:1:4 DETAILED DESCRIPTION

[0059] 1. In the examples of the present invention, the preparation processes of the reference catalysts CNO, CBO, and CBN are provided. The preparation process of the reference catalysts differs from the preparation process of CBNO in that:

[0060] When preparing CNO (wherein C represents activated carbon, N represents dicyandiamide, and O represents nitric acid treatment), no boric acid raw material is added in step 1;

[0061] When preparing CBO (wherein C represents activated carbon, B represents boric acid, and O represents nitric acid treatment), no dicyandiamide raw material is added in step 1;

[0062] When preparing CBN (wherein C represents activated carbon, B represents boric acid, and N represents dicyandiamide), hydrochloric acid is used instead of nitric acid in step three.

[0063] 2. The electrochemical test embodiment provided by the present invention has the following measurement method:

[0064] The catalyst prepared by the present invention was subjected to electrochemical measurements under the same test conditions as advanced and efficient carbon catalysts in the prior art. The existing catalysts used for comparison in the present invention include: CoPc-OCNT catalyst, N-FLG catalyst, NiB2 catalyst, BNC catalyst, OCNS900 catalyst, NBO-G / CNTs catalyst, OCG catalyst, Co-NG(O) catalyst, Co-NC catalyst, NiMOF NSs catalyst, O-GOMC catalyst, P-NMG-X catalyst, PBT catalyst, CQD catalyst, h-SNO2 catalyst, Co-NC catalyst, Co / NC catalyst, and ZnO@ZnO2 catalyst.

[0065] The electrochemical measurements used in the present invention were all performed in a conventional three-electrode system on a CHI 760E electrochemical workstation, using a 0.1 M Na2SO4 solution as the electrolyte. The selectivity of hydrogen peroxide and the number of transferred electrons during the ORR process were measured using a rotating ring disk electrode (RRDE). The electrode was equipped with a glassy carbon (GC) electrode, Ag / AgCl, and a carbon rod as the working electrode, reference electrode, and counter electrode, respectively.

[0066] All potentials are referred to as reversible hydrogen electrode (RHE).

[0067] The specific test steps are as follows: 5 mg of the sample to be tested was dispersed in a solution containing 500 μL of ethanol and 50 μL of Nafion (D520) to prepare a catalyst slurry; the mixture was sonicated for 30 minutes, and then 5.5 μL of the catalyst slurry was dropped onto a glass electrode; a linear sweep voltammetry (LSV) test was performed at 1600 rpm in an oxygen-saturated 0.1 M Na2SO4 electrolyte; and a potential of 1.2 V was applied to the ring electrode to oxidize the generated hydrogen peroxide.

[0068] The following formulas are used to calculate the selectivity and the number of transferred electrons:

[0069] Selectivity of hydrogen peroxide (%) = 200 × (i r / N) / (i d +i r / N)

[0070] Number of transferred electrons (n) = 4×i d / (i d +i r / N)

[0071] Among them, i r is the ring current, i d is the disk current, and N is the collection efficiency (0.37 after calibration).

[0072] 3. Faraday efficiency (FE)

[0073] In electrocatalytic redox reactions, charge (such as electrons) transfer occurs at the metal-solution interface on the electrode, and the electron transfer causes an oxidation or reduction reaction. Since the reaction obeys Faraday's law (that is, the amount of chemical reaction caused by the passage of current is proportional to the amount of electricity passed), they are called Faradaic processes. The gas products obtained during the reaction can be qualitatively and quantitatively detected by gas chromatography to determine how much charge is used to generate gas products during the reaction. Therefore, Faradaic efficiency (FE) can be used to evaluate the performance of the catalyst. In the photoelectrocatalytic reaction, Faradaic efficiency (FE) refers to the percentage of actual products and theoretical products, that is, the utilization efficiency of energy conversion, which can be calculated according to the formula:

[0074] FE (%) = 2C × V × F / Q × 100

[0075] Where C represents the concentration of H2O2; V represents the volume of the electrolyte; F is the Faraday constant (96485C mol -1 ); Q is the total number of electrons transferred during the reaction.

[0076] Introduction to the measurement method of C (in the present invention, the value of C is determined by the electrochemical measurement results of the embodiment):

[0077] The cerium sulfate Ce(SO4)2 titration method is used to quantitatively measure the concentration of H2O2. 4+ The solution changes color to colorless Ce through the following reaction 3+ :2Ce 4+ +H2O2→2Ce 3+ +2H++O2

[0078] The following is the actual operation process of the present invention. Weighed Ce(SO4)2 is dissolved in a 0.5M aqueous solution of sulfuric acid (H2SO4) to obtain a Ce(SO4)2 aqueous solution (1mM). 1mL of a 0.1 to 0.5mM aqueous H2O2 solution is mixed with 3mL of the above Ce(SO4)2 solution to prepare a series of mixed solutions. The UV-visible spectra of these solutions are collected to create a calibration curve. The H2O2 concentration (C) is calculated according to the formula.

[0079] C = -0.362 x x + 0.919, where x is the absorbance measured by UV-visible spectroscopy.

[0080] V is the volume of the electrolyte solution, and its value is 50 ml.

[0081] Q is calculated according to the following formula: Q = I × t

[0082] I is the current density during the reaction, which is 100 mA cm -2 , t is the test time, its value is 24h.

[0083] In the present invention,

[0084] C, V, Q = I × t are obtained from the electrochemical test embodiment description and the embodiment measurement results. In the embodiment (electrochemical test embodiment) provided by the present invention, according to the embodiment description and the electrochemical measurement results, C is 623mmol L -1 ; V is 50ml; I is 100mA cm -2 , t is 24h.

[0085] Example 1

[0086] Preparation of CBNO:

[0087] 0.1g of activated carbon, 0.1g of dicyandiamide, and 0.4g of boric acid were weighed separately in an agate mortar and thoroughly mixed. The mixture was then repeatedly ground for 15 minutes until there were no solid particles and a uniform, fine slurry formed. The mixture was then transferred to a 2cm × 6cm ark and placed in a tube furnace. The temperature was raised at a rate of 2°C / min to a final setting of 1000°C. The calcination process was completed by maintaining the temperature at this setting for 2 hours and then cooling. After the material cooled to room temperature, it was placed in a 25mL round-bottom flask and 15mL of 3mol / L nitric acid solution was added. The mixture was then refluxed in an 80°C waterbath for 24 hours. The slurry was then washed repeatedly with deionized water until the pH reached neutrality and dried in a 70°C oven for 12 hours. The resulting material is designated CBNO (where C represents activated carbon, B represents boric acid, N represents dicyandiamide, and O represents nitric acid treatment).

[0088] Example 2

[0089] Preparation of CBN

[0090] 0.1g of activated carbon, 0.1g of dicyandiamide, and 0.4g of boric acid were weighed separately and placed in an agate mortar. After thorough mixing, the mixture was repeatedly ground for 15 minutes until there were no solid particles and a uniform fine slurry was formed. The mixture was then transferred to a 2cm×6cm ark and placed in a tube furnace. The temperature was increased at a rate of 2°C / min to the final set temperature of 1000°C. The calcination process was completed after the temperature was maintained at this condition for 2 hours and then cooled. After the material cooled to room temperature, it was placed in a 100mL beaker and 60mL of dilute hydrochloric acid solution (5mol / L) was added. The mixture was then washed and stirred on a stirrer at room temperature for 24 hours. After removal, it was repeatedly washed with deionized water until the solution pH reached neutrality and then dried in a 70°C oven for 12 hours. The prepared material is designated as CBN (where C represents activated carbon, B represents boric acid, and N represents dicyandiamide).

[0091] Example 3

[0092] Preparation of CBO

[0093] 0.1g of activated carbon and 0.4g of boric acid were weighed separately and placed in an agate mortar. After thorough mixing, the mixture was repeatedly ground for 15 minutes until there were no solid particles and a uniform fine slurry was formed. The mixture was then transferred to a 2cm×6cm ark and placed in a tube furnace. The temperature was increased at a rate of 2°C / min to the final set temperature of 1000°C. The calcination process was completed after the temperature was lowered to maintain this condition for 2 hours. After the material cooled to room temperature, it was placed in a 25mL round-bottom flask and 15mL of 3mol / L nitric acid solution was added. The flask was refluxed in an 80°C waterbath for 24 hours. After removal, the solution was repeatedly washed with deionized water until the pH reached neutrality and then dried in a 70°C oven for 12 hours. The prepared material is designated CBO (where C represents activated carbon, B represents boric acid, and O represents nitric acid treatment).

[0094] Example 4

[0095] Preparation of CNO

[0096] 0.1g of activated carbon and 0.4g of dicyandiamide were weighed separately and placed in an agate mortar. After thorough mixing, the mixture was repeatedly ground for 15 minutes until there were no solid particles and a uniform fine slurry was formed. The mixture was then transferred to a 2cm×6cm ark and placed in a tube furnace. The temperature was increased at a rate of 2°C / min to a final setting of 1000°C. The calcination process was completed after the temperature was maintained at this condition for 2 hours. After cooling, the material was placed in a 25mL round-bottom flask and 15mL of 3mol / L nitric acid solution was added. The flask was refluxed in an 80°C waterbath for 24 hours. After removal, the solution was repeatedly washed with deionized water until the pH reached neutrality and then dried in a 70°C oven for 12 hours. The resulting material is designated CNO (where C represents activated carbon, N represents dicyandiamide, and O represents nitric acid treatment).

[0097] Example 5

[0098] Preparation of CBNO:

[0099] 0.1g of activated carbon, 0.1g of dicyandiamide, and 0.4g of boric acid were weighed separately in an agate mortar and thoroughly mixed. The mixture was then repeatedly ground for 15 minutes until there were no solid particles and a uniform, fine slurry formed. The mixture was then transferred to a 2cm × 6cm ark and placed in a tube furnace. The temperature was raised at a rate of 2°C / min to a final setting of 800°C. The calcination process was completed by maintaining the temperature at this setting for 2 hours and then cooling. After the material cooled to room temperature, it was placed in a 25mL round-bottom flask and 15mL of 3mol / L nitric acid solution was added. The mixture was then refluxed in an 80°C waterbath for 24 hours. The flask was then washed repeatedly with deionized water until the pH reached neutrality and dried in a 70°C oven for 12 hours. The resulting material is designated CBNO (where C represents activated carbon, B represents boric acid, N represents dicyandiamide, and O represents nitric acid treatment).

[0100] Example 6

[0101] Preparation of CBNO:

[0102] 0.1g of activated carbon, 0.1g of dicyandiamide, and 0.4g of boric acid were weighed separately in an agate mortar and thoroughly mixed. The mixture was then repeatedly ground for 15 minutes until there were no solid particles and a uniform, fine slurry formed. The mixture was then transferred to a 2cm×6cm ark and placed in a tube furnace. The temperature was raised at a rate of 2°C / min to a final setting of 900°C, maintained at this temperature for 2 hours, and then cooled to complete the calcination process. After the material cooled to room temperature, it was placed in a 25mL round-bottom flask and 15mL of 3mol / L nitric acid solution was added. The mixture was then refluxed in an 80°C waterbath for 24 hours. The flask was then washed repeatedly with deionized water until the pH reached neutrality and dried in a 70°C oven for 12 hours. The resulting material is designated CBNO (where C represents activated carbon, B represents boric acid, N represents dicyandiamide, and O represents nitric acid treatment).

[0103] Example 7

[0104] Preparation of CBNO:

[0105] 0.1g of activated carbon, 0.1g of dicyandiamide, and 0.4g of boric acid were weighed separately in an agate mortar and thoroughly mixed. The mixture was then repeatedly ground for 15 minutes until no solid particles were present and a uniform, fine slurry formed. The mixture was then transferred to a 2cm × 6cm ark and placed in a tube furnace. The temperature was raised at a rate of 2°C / min to a final setting of 1100°C. The calcination process was completed by maintaining the temperature at this setting for 2 hours and then cooling. After the material cooled to room temperature, it was placed in a 25mL round-bottom flask and 15mL of 3mol / L nitric acid solution was added. The mixture was then refluxed in an 80°C waterbath for 24 hours. The slurry was then washed repeatedly with deionized water until the pH reached neutrality and dried in a 70°C oven for 12 hours. The resulting material is designated CBNO (where C represents activated carbon, B represents boric acid, N represents dicyandiamide, and O represents nitric acid treatment).

[0106] Example 8

[0107] Preparation of CBNO:

[0108] 0.1g of activated carbon, 0.1g of dicyandiamide, and 0.4g of boric acid were weighed separately in an agate mortar and thoroughly mixed. The mixture was then repeatedly ground for 15 minutes until no solid particles were present and a uniform, fine slurry formed. The mixture was then transferred to a 2cm × 6cm ark and placed in a tube furnace. The temperature was raised at a rate of 2°C / min to a final setting of 1000°C. The calcination process was completed by maintaining the temperature at this setting for 2 hours and then cooling. After the material cooled to room temperature, it was placed in a 25mL round-bottom flask and 15mL of 3mol / L nitric acid solution was added. The mixture was then refluxed in an 80°C waterbath for 12 hours. The slurry was then washed repeatedly with deionized water until the pH reached neutrality and dried in a 70°C oven for 12 hours. The resulting material is designated CBNO (where C represents activated carbon, B represents boric acid, N represents dicyandiamide, and O represents nitric acid treatment).

[0109] Example 9

[0110] Preparation of CBNO:

[0111] 0.1g of activated carbon, 0.1g of dicyandiamide, and 0.4g of boric acid were weighed separately in an agate mortar and thoroughly mixed. The mixture was then repeatedly ground for 15 minutes until no solid particles were present and a uniform, fine slurry formed. The mixture was then transferred to a 2cm × 6cm ark and placed in a tube furnace. The temperature was raised at a rate of 2°C / min to a final setting of 1000°C. The calcination process was completed by maintaining the temperature at this setting for 2 hours and then cooling. After the material cooled to room temperature, it was placed in a 25mL round-bottom flask and 15mL of 3mol / L nitric acid solution was added. The mixture was then refluxed in an 80°C waterbath for 36 hours. The slurry was then washed repeatedly with deionized water until the pH reached neutrality and dried in a 70°C oven for 12 hours. The resulting material is designated CBNO (where C represents activated carbon, B represents boric acid, N represents dicyandiamide, and O represents nitric acid treatment).

[0112] Example 10

[0113] Preparation of CBNO:

[0114] 0.1g of activated carbon, 0.1g of dicyandiamide, and 0.4g of boric acid were weighed separately in an agate mortar and thoroughly mixed. The mixture was then repeatedly ground for 15 minutes until no solid particles were present and a uniform, fine slurry formed. The mixture was then transferred to a 2cm × 6cm ark and placed in a tube furnace. The temperature was raised at a rate of 2°C / min to a final setting of 1000°C. The calcination process was completed by maintaining the temperature at this setting for 2 hours and then cooling. After the material cooled to room temperature, it was placed in a 25mL round-bottom flask and 15mL of 3mol / L nitric acid solution was added. The mixture was then refluxed in an 80°C waterbath for 48 hours. The slurry was then washed repeatedly with deionized water until the pH reached neutrality and dried in a 70°C oven for 12 hours. The resulting material is designated CBNO (where C represents activated carbon, B represents boric acid, N represents dicyandiamide, and O represents nitric acid treatment).

[0115] Example 11

[0116] Preparation of CBNO:

[0117] 0.1g of activated carbon, 0.1g of dicyandiamide, and 0.1g of boric acid were weighed separately in an agate mortar and thoroughly mixed. The mixture was then repeatedly ground for 15 minutes until no solid particles were present and a uniform, fine slurry formed. The mixture was then transferred to a 2cm × 6cm ark and placed in a tube furnace. The temperature was raised at a rate of 2°C / min to a final setting of 1000°C. The calcination process was completed by maintaining the temperature at this setting for 2 hours and then cooling. After the material cooled to room temperature, it was placed in a 25mL round-bottom flask and 15mL of 3mol / L nitric acid solution was added. The mixture was then refluxed in an 80°C waterbath for 48 hours. The slurry was then washed repeatedly with deionized water until the pH reached neutrality and dried in an 80°C oven for 18 hours. The resulting material is designated CBNO (where C represents activated carbon, B represents boric acid, N represents dicyandiamide, and O represents nitric acid treatment).

[0118] Example 12

[0119] Preparation of CBNO:

[0120] 0.1g of activated carbon, 0.1g of dicyandiamide, and 0.2g of boric acid were weighed separately in an agate mortar and thoroughly mixed. The mixture was then repeatedly ground for 15 minutes until no solid particles were present and a uniform, fine slurry formed. The mixture was then transferred to a 2cm × 6cm ark and placed in a tube furnace. The temperature was raised at a rate of 2°C / min to a final setting of 1000°C. The calcination process was completed by maintaining the temperature at this setting for 2 hours and then cooling. After the material cooled to room temperature, it was placed in a 25mL round-bottom flask and 15mL of 3mol / L nitric acid solution was added. The flask was then refluxed in an 80°C waterbath for 48 hours. The flask was then washed repeatedly with deionized water until the pH reached neutrality and then dried in a 90°C oven for 24 hours. The resulting material is designated CBNO (where C represents activated carbon, B represents boric acid, N represents dicyandiamide, and O represents nitric acid treatment).

[0121] Example 13

[0122] Preparation of CBNO:

[0123] 0.1g of activated carbon, 0.1g of dicyandiamide, and 0.3g of boric acid were weighed separately in an agate mortar and thoroughly mixed. The mixture was then repeatedly ground for 15 minutes until no solid particles were present and a uniform, fine slurry formed. The mixture was then transferred to a 2cm × 6cm ark and placed in a tube furnace. The temperature was raised at a rate of 2°C / min to a final setting of 1000°C. The calcination process was completed by maintaining the temperature at this setting for 2 hours and then cooling. After the material cooled to room temperature, it was placed in a 25mL round-bottom flask and 15mL of 3mol / L nitric acid solution was added. The mixture was then refluxed in an 80°C waterbath for 48 hours. The slurry was then washed repeatedly with deionized water until the pH reached neutrality and dried in a 70°C oven for 12 hours. The resulting material is designated CBNO (where C represents activated carbon, B represents boric acid, N represents dicyandiamide, and O represents nitric acid treatment).

[0124] Attachment Figure 1 A schematic diagram of the synthesis of the catalyst provided by the present invention is shown.

[0125] Attachment Figures 2 to 14 Examples of tests for material characterization are presented.

[0126] Material properties test example 1

[0127] The CBNO prepared in Example 1 was measured by scanning electron microscopy (SEM), and the test results were as follows: Figure 2 As shown:

[0128] After high-temperature pyrolysis and acid treatment, the original form of the carbon material in the obtained catalyst is retained.

[0129] Scanning electron microscopy (SEM) images of the samples were collected on a Hitachi S-4800 scanning electron microscope (10 kV).

[0130] Material properties test example 2

[0131] The CBNO prepared in Example 1 was measured by transmission electron microscopy (TEM), and the test results were as follows: Figure 3 、 Figure 4 (Partial enlarged image) as shown:

[0132] Figure 3 The image shows a region where a large amount of h-BN and graphene layers coexist; the d(002) of one h-BN domain is 0.366 nm, with a bright spot (blue box) in the FFT image, while the d(002) of the graphitized region is 0.335 nm, with a bright spot (yellow box);

[0133] Figure 4 It shows that the graphitized area (yellow area) is closely connected to the h-BN area (blue area), forming an h-BN / G heterojunction structure.

[0134] Transmission electron microscopy (TEM) images of the samples were obtained on a JEM-2100 (JEOL) electron microscope (200 kV).

[0135] Material properties test example 3

[0136] The XRD diffraction patterns of the CBNO, CBN, CBO, CNO samples and commercial activated carbon (AC, commercially available) prepared in Examples 1 to 4 were measured. The test results are as follows: Figure 5 As shown:

[0137] Figure 5 The amorphous structures of CBNO, CBN, CNO, CBO, and AC are shown. Compared with the other samples, the B and N co-doped CBN sample shows a sharper diffraction peak at 26.5°, indicating the presence of a large number of h-BN / G microcrystals.

[0138] X-ray diffraction (XRD) patterns of all samples were collected using a Rigaku Smart Lab X-ray diffractometer.

[0139] Material properties test example 4

[0140] The Raman spectra of the CBNO, CBN, CBO, CNO samples and commercial activated carbon (AC, commercially available) prepared in Examples 1 to 4 were measured. The test results are as follows: Figure 6 As shown:

[0141] Figure 6The peak area ratios of the D and G peaks for CBN and CBNO are 0.43 and 0.64, respectively, lower than those for the other three samples. The D and G peak area ratios are used to characterize the quality of the prepared crystals; lower values ​​indicate higher quality, meaning the crystals are closer to an ideal structure. The peak area ratio for CBNO is higher than that for CBN, indicating that the crystal structure of the prepared CBNO catalyst is of lower quality than that of the prepared CBN catalyst, but higher than that of the CBO and CNO samples, as well as commercial activated carbon (AC).

[0142] Raman spectra of all samples were collected by a Horiba HR 800 spectrometer coupled with a Spectra-Physics 2018 argon / krypton ion laser system (excitation wavelength: 514 nm).

[0143] Material properties test example 5

[0144] The CBNO, CBN, CBO, CNO samples prepared in Examples 1 to 4 and commercial activated carbon (AC, commercially available) were subjected to Fourier transform infrared spectroscopy (FTIR) testing. The test results are as follows: Figure 7 As shown:

[0145] Figure 7 The Fourier transform infrared (FTIR) spectrum of AC is in the range of 700-1450 cm -1 A broad band is shown at the center, representing the random distribution of different C–O groups, such as hydroxyl groups, ether bonds (700–1100 cm -1 ) and epoxy groups (1100-1450cm -1 ); after high-temperature pyrolysis, these adsorption bands disappear because the original oxygen-containing groups are removed, thereby retaining some C–O groups, such as 1049 cm -1 As shown by the peak value at

[0146] CBNO and CBN at 722cm -1 and 1380cm -1 The peak from h-BN appears at , and the peak intensity of the former is greater, indicating that more B–N bonds are formed;

[0147] CBNO, CBO and CNO at 1716 cm -1 A peak from the C=O functional group appeared at , confirming that the sample contained abundant oxygen-containing functional groups after nitric acid treatment.

[0148] Fourier transform infrared (FTIR) spectra of all samples were obtained on an Agilent Cary 660.

[0149] Material properties test example 6

[0150] The CBNO and CBN prepared in Examples 1 and 2 were subjected to X-ray photoelectron spectroscopy (XPS) spectrum measurement. The test results are as follows: Figures 8-11 As shown:

[0151] Figure 8 High-resolution B1s XPS spectra of CBNO and CBN are shown, revealing the presence of B–C (190.7 eV), B–N (191.5 eV), N–B–O (192.1 eV), and B–O (192.9 eV) species;

[0152] Figure 9 The N1s XPS spectra of CBNO and CBN in the medium showed N–C (398.3 eV), N–B (398.8 eV), and N–BO (399.5 eV) signals. Compared with CBN, CBNO showed a lower binding energy N1s signal and a weaker N–B signal, which was attributed to the formation of N–B–C.

[0153] Figure 10 The C1s XPS spectra of CBO, CNO, and CBNO show obvious C=O bonds, which means that functional carboxyl groups are formed after nitric acid treatment. Samples containing B and N show obvious C–B (283.4 eV) and C–N (286 eV) peaks, further revealing the covalent bond connecting the h-BN and graphene interface. C–N and C–B signals can also be observed in CNO and CBO, which proves the respective doping of N and B elements.

[0154] Figure 11 The O1s XPS spectra of the samples showed that the C–O bonds in all samples originated from the intrinsic functional groups in AC; the C=O functional groups in CBNO, CBO, and CNO originated from the oxidation of nitric acid.

[0155] X-ray photoelectron spectroscopy (XPS) spectra of all samples were collected on a PHI5000 Versa Probe X-ray photoelectron spectrometer equipped with Al Kα radiation (1486.6 eV).

[0156] Material properties test example 7

[0157] The CBNO, CBN and pure boron nitride (BN, commercially available) prepared in Examples 1 and 2 were subjected to near-edge X-ray absorption fine structure (NEXAFS) spectroscopy based on synchrotron radiation. The test results are as follows: Figures 12-14 As shown:

[0158] like Figure 12 As shown, the BK-edge NEXAFS spectrum of pure boron nitride (BN) shows sp 2The spectral fingerprint of hybrid h-BN; the three characteristic peaks at 191.6eV, 192.3eV and 192.9eV are the π* transition peaks of B–N bonds in h-BN (such as BN3), BN2O and BNO2 respectively; the BK-edge NEXAFS spectra of CBNO and CBN are similar to those of BN, indicating the presence of h-BN;

[0159] Figure 13 The NK-edge NEXAFS spectra further confirmed the above viewpoints; all samples showed obvious π*(h-BN) (400.5eV) and σ*(h-BN) (407.5eV) resonance peaks, consistent with typical h-BN; combined B- and NK-edge NEXAFS showed that the characteristic π* transition peak was significantly weakened in the sequence of BN, CBN and CBNO, indicating that weaker N-bond structures such as N–C and B–N–C were formed in the latter two samples compared with the N–B bond of BN;

[0160] Figure 14 The middle OK-edge NEXAFS spectrum further analyzed the surface oxygen functional groups; the π* resonance peak at 531.8 eV indicated the presence of C–O–C groups; in contrast, CBNO showed weaker peaks near 532 and 540 eV, while σ*(COOH) showed a clear peak at 535 eV, verifying the formation of –COOH-functionalized h-BN / G structure.

[0161] Synchrotron radiation-based near-edge X-ray absorption fine structure (NEXAFS) measurements of all samples were performed at the Surface, Interface and Nanostructure Science (SINS) beamline at the Singapore Synchrotron Radiation Source, which is equipped with a Scienta R4000 electron energy analyzer.

[0162] Electrochemical test example

[0163] Attachment Figures 15-34 Examples of electrochemical testing are presented.

[0164] All electrochemical measurements were performed in a conventional three-electrode system on a CHI 760E electrochemical workstation using 0.1 M Na2SO4 solution as the electrolyte. The selectivity of hydrogen peroxide and the number of transferred electrons during the ORR process were measured using a rotating ring disk electrode (RRDE), which was equipped with a glassy carbon (GC) electrode, Ag / AgCl, and a carbon rod as the working electrode, reference electrode, and counter electrode, respectively. All potentials were referred to as reversible hydrogen electrode (RHE).

[0165] The following formulas are used to calculate the selectivity and the number of transferred electrons:

[0166] Selectivity of hydrogen peroxide (%) = 200 × (i r / N) / (id +i r / N)

[0167] Number of transferred electrons (n) = 4×i d / (i d +i r / N)

[0168] Among them, i r is the ring current, i d is the disk current, and N is the collection efficiency (0.37 after calibration).

[0169] The specific test steps are as follows: 5 mg of the sample to be tested was dispersed in a solution containing 500 μL of ethanol and 50 μL of Nafion (D520) to prepare a catalyst slurry; the mixture was ultrasonicated for 30 minutes, and then 5.5 μL of the catalyst slurry was dropped onto a glass electrode; a linear sweep voltammetry (LSV) test was performed at 1600 rpm in an oxygen-saturated 0.1 M Na2SO4 electrolyte; and a potential of 1.2 V was applied to the ring electrode to oxidize the generated hydrogen peroxide.

[0170] Electrochemical measurements were performed on the CBNO, CBN, CBO, CNO samples prepared in Examples 1 to 4 and commercial activated carbon (AC, commercially available).

[0171] The test results are as follows Figures 15-22 As shown:

[0172] like Figure 15 As shown, all tested samples have significant oxygen reduction disk current and hydrogen peroxide oxidation decomposition ring current; the ring current density of CBNO (0.88 mA cm -2 ) is higher than AC (0.37mA cm -2 ) and other samples doped with B and N (0.34-0.64 mA cm -2 ), showing excellent hydrogen peroxide generation ability;

[0173] Figure 16 The selectivity obtained from the ring-disk current value shows that the electron transfer number (n) of CBNO at 0.60 V is close to 2, and the selectivity is as high as 95%, reflecting the 2e - Favorable trends in ORR process;

[0174] Figure 17 The Tafel slopes of different samples were calculated and the results showed that in the high potential range (0.72-0.76 V), the 51.8 mV dec of CBNO -1 The value is lower than CBN (78.8mv dec -1 )、CBO(97.1mv dec -1 )、CNO(120mvdec-1 ) and AC (112mv dec -1 ), reflecting that the former has more superior ORR kinetics;

[0175] Figure 18 The linear sweep voltammetry (LSV) curves show that the current density in O2-saturated solution is significantly higher than that in N2-saturated solution, demonstrating excellent ORR activity.

[0176] Figure 19 As can be seen from the figure, in the H-type cell at 0V, the hydrogen peroxide yield of CBNO is as high as 2890mmol g -1 h -1 (FE = 95%); The process of electrosynthesis of hydrogen peroxide from CBNO in a flow cell was further optimized, and the hydrogen peroxide yield reached an unprecedented 13400 mmol g -1 h -1 , FE value is as high as 93%.

[0177] Figure 20 A comprehensive comparison with previous work showed that its hydrogen peroxide yield exceeded that of the most advanced carbon catalysts and even most metal-based catalysts;

[0178] Figure 21 It can be seen that during the 24-hour electrocatalytic process, CBNO maintained stability at a high current density, resulting in a cumulative concentration of hydrogen peroxide as high as 2.1 wt.% (623 mmol L -1 );

[0179] Figure 22 A comprehensive comparison with previous work shows that this concentration is one of the highest to date.

[0180] Further investigation was conducted on the effect of different pyrolysis temperatures on the 2e-ORR activity. The CBNO prepared in Example 1 and Examples 5 to 7 was subjected to electrochemical determination.

[0181] The test results are as follows Figures 23-26 As shown:

[0182] When the calcination temperature in the tube furnace increased from 800°C to 1000°C, the ORR production rate of hydrogen peroxide was the highest at a relative applied voltage of -0.3V, and the corresponding Faradaic efficiency increased to 93%. When the pyrolysis temperature was further increased to 1100°C, the production rate of hydrogen peroxide produced by oxygen electroreduction became 456mmol g -1 h -1 , the Faraday efficiency dropped to 79%. Comparative analysis of these experimental results shows that the reaction activity of the boron-nitrogen co-doped carbon material prepared at a pyrolysis temperature of 1000℃ is the best.

[0183] Further investigation of the effect of different nitric acid treatment times on 2e - The effect of ORR activity was determined by electrochemical analysis of the CBNO prepared in Examples 1 and 8 to 10.

[0184] The test results are as follows Figures 27-30 As shown:

[0185] The results show that the reaction activity (Faraday efficiency and production rate) of samples treated with HNO3 for 12 hours is lower than that of samples treated with HNO3 for 24 hours. However, as the HNO3 treatment time continues to increase, the hydrogen peroxide production rate of the corresponding catalyst in the ORR reaction gradually decreases, while the corresponding Faradaic efficiency increases significantly during this process. This indicates that excessive nitric acid treatment time can easily cause a certain degree of corrosion on the sample surface, hindering the interaction between oxygen and the catalyst surface, thereby reducing the hydrogen peroxide production rate.

[0186] Further investigation was conducted on the effect of the feed ratio of the precursor on the 2e-ORR activity. The CBNO prepared in Example 1 and Examples 11 to 13 was subjected to electrochemical determination.

[0187] The test results are as follows Figures 31-34 As shown:

[0188] When the ratio of activated carbon to dicyandiamide is fixed and the content of boric acid is changed, Figures 31-34 Activity comparison found that the ORR reaction activity reached the optimal level when the mass ratio of activated carbon, dicyandiamide and boric acid was 1:1:4.

Claims

1. A nitrogen and boron co-doped carbon material, characterized in that: The nitrogen and boron co-doped carbon material is prepared by mixing activated carbon, dicyandiamide and boric acid, followed by high-temperature pyrolysis treatment to form an h-BN / G heterojunction structure, and then acid etching to form a carboxyl functionalized h-BN region; the acid etching treatment is performed by using one or more of dilute nitric acid, dilute sulfuric acid or dilute hydrochloric acid solutions to condense and reflux the material to be treated at 70 to 90°C.

2. A method for preparing hydrogen peroxide, characterized in that: A carbon material containing carboxylated boron nitride is used as a catalyst. The carbon material containing carboxylated boron nitride is prepared by mixing activated carbon, dicyandiamide and boric acid, followed by high-temperature pyrolysis treatment to form an h-BN / G heterojunction structure, and then undergoing acid etching treatment to form a carboxyl-functionalized h-BN region. The acid etching treatment is performed by using one or more of dilute nitric acid, dilute sulfuric acid or dilute hydrochloric acid solutions to condense and reflux the material to be treated at 70-90°C.

3. A method for preparing hydrogen peroxide using an electrocatalytic redox method, characterized in that: A carbon material containing carboxylated boron nitride is used as a catalyst. The carbon material containing carboxylated boron nitride is prepared by mixing activated carbon, dicyandiamide and boric acid, followed by high-temperature pyrolysis treatment to form an h-BN / G heterojunction structure, and then undergoing acid etching treatment to form a carboxyl-functionalized h-BN region. The acid etching treatment is performed by using one or more of dilute nitric acid, dilute sulfuric acid or dilute hydrochloric acid solutions to condense and reflux the material to be treated at 70-90°C.

4. The method according to claim 3, wherein The preparation method of the carbon material containing carboxylated boron nitride is as follows: S1, mixing activated carbon, dicyandiamide and boric acid, and then grinding; S2, heating the product obtained in S1; S3, performing acid etching on the cooled S2 product; washing the acid-etched product with water until the pH is neutral, and then drying the product to obtain a carbon material containing carboxylated boron nitride.

5. The method according to claim 4, wherein The activated carbon, dicyandiamide and boric acid in S1 are mixed in a mass ratio of 1:1:(1-4); the grinding treatment in S1 is to grind the mixed activated carbon, dicyandiamide and boric acid until the solid particle size is ≤2 μm.

6. The method according to claim 4, wherein The heating treatment of S2 is to heat the product to 800-1100° C. at a heating rate of 1-5° C. / min, and then calcine under this condition for 2-4 hours.

7. The method according to claim 4, wherein The acid etching treatment of S3 is performed by using a dilute acid solution and condensing and refluxing at 70-90° C. for 24-36 hours; the dilute acid solution is a dilute nitric acid, dilute sulfuric acid or dilute hydrochloric acid solution with a concentration of 3-5 mol / L.

8. The method according to claim 4, wherein The drying treatment in S3 is heating and drying at 70-90° C. for 12-24 hours.

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