Carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst, preparation method and application

Abstract

The invention discloses a carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst as well as a preparation method and application thereof. The carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst is formed by crosslinking a carbon-coated zinc oxide nanosheet and a carbon nitride nanosheet through a carbon layer, and a heterojunction is formed between the carbon-coated zinc oxide nanosheet and the carbon nitride nanosheet. The preparation method comprises the following steps: mixing and grinding a carbon-coated zinc oxide nano-material and a carbon nitride nano-sheet, and calcining in a protective atmosphere. The carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst can effectively promote photon-generated carrier separation, reduce the recombination rate of electron-hole pairs, and significantly improve the efficiency of photocatalytic production of hydrogen peroxide in an air atmosphere. Meanwhile, hydrogen peroxide generated in situ can react with bicarbonate in the system to generate peroxybicarbonate with high oxidation activity, and active oxygen species such as hydroxyl radicals are generated through activation in the photocatalytic process, so that the degradation capacity on the organic pollutants is further enhanced, and efficient degradation of the organic pollutants is realized.

Description

Technical Field

[0001] This invention relates to a heterojunction composite photocatalyst, specifically to a carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst, its preparation method, and its application, belonging to the fields of environmental chemistry, chemical engineering, and materials science. Background Technology

[0002] Environmental and energy issues have become increasingly pressing global concerns. Hydrogen peroxide, as a green and environmentally friendly chemical, is experiencing continuously growing global demand as an oxidant and energy carrier. However, the anthraquinone process, widely used in industry, suffers from high risks of raw material and product explosions, involves strong oxidants and high-pressure conditions, consumes a large amount of energy, and generates substantial amounts of toxic wastewater, making it difficult to meet the requirements of sustainable development. Therefore, the technology of directly synthesizing hydrogen peroxide from water and oxygen using solar energy-driven photocatalytic reactions has become an important alternative to traditional processes due to its cleanliness, sustainability, and high efficiency, attracting significant attention from both academia and industry.

[0003] Therefore, finding a heterojunction composite photocatalyst capable of photocatalytic production of H2O2 and constructing a photocatalytic peroxybicarbonate advanced oxidation system has become a long-term goal for researchers in the industry. Summary of the Invention

[0004] The main objective of this invention is to provide a carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst and its preparation method, so as to overcome the shortcomings of the prior art.

[0005] Another object of the present invention is to provide the application of the aforementioned carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: This invention provides a carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst, which is composed of carbon-coated zinc oxide nanosheets and carbon nitride nanosheets cross-linked together by a carbon layer, wherein a heterojunction is formed between the carbon-coated zinc oxide nanosheets and carbon nitride nanosheets.

[0007] This invention also provides a method for preparing a carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst, comprising: The zinc source, surfactant, and organic ligand are mixed and stirred to promote the self-assembly of zinc ions in the zinc source with the organic ligand to form a zinc oxide precursor. The zinc oxide precursor was mixed and stirred with tannic acid solution, the solid phase was collected, and then subjected to a first high-temperature calcination to obtain carbon-coated zinc oxide nanomaterials. The carbon-coated zinc oxide nanomaterials and carbon nitride nanosheets were mixed, ground, and then subjected to a second high-temperature calcination to obtain a carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst.

[0008] This invention also provides a carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst prepared by the above-described method.

[0009] This invention also provides the application of the carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst in photocatalytic preparation of hydrogen peroxide or water treatment.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) The carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst provided by the present invention is composed of a carbon layer introduced between zinc oxide and carbon nitride interface to make the two cross-linked. In addition, the carbon layer acts as an electron conduction layer and constructs a built-in electric field to promote charge separation and transfer and enhance the redox reaction on the catalyst surface. 2) The photocatalyst of this invention constructs a photocatalytic peroxybicarbonate advanced oxidation system for degrading organic pollutants in water. It utilizes in-situ produced hydrogen peroxide to react with bicarbonate through an equilibrium reaction to generate peroxybicarbonate. The peroxybicarbonate is then activated through a photocatalytic process to generate reactive oxygen species, achieving rapid removal of organic pollutants. This system exhibits strong oxidative stability and high efficiency in pollutant degradation under alkaline and near-neutral conditions (close to natural water conditions). The reaction system is simple, non-corrosive, and free of side reactions. This method aligns with the current needs of the chemical industry for compatibility with the ecological environment and sustainable development, thus possessing significant industrial application value and social significance. 3) The carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst of the present invention uses air as the O2 source and solar energy as the energy source under normal pressure to achieve efficient photocatalytic production of hydrogen peroxide and to construct a photocatalytic peroxybicarbonate advanced oxidation system to degrade organic pollutants in water. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a transmission electron microscope image of ZnO@C prepared in step (2) of Example 1 of the present invention; Figure 2 This is a high-magnification transmission electron microscope image of ZnO@C prepared in step (2) of Example 1 of the present invention; Figure 3 This is a transmission electron microscope image of the PHI prepared in step (3) of Example 1 of the present invention; Figure 4 These are transmission electron microscope (TEM) images and high-magnification TEM images of ZnO@C / PHI prepared in step (4) of Example 1 of this invention. Figure 5 These are the X-ray diffraction spectra of ZnO@C, PHI, and ZnO@C / PHI prepared in steps (2), (3), and (4) of Example 1 of the present invention; Figure 6 These are the UV-Vis diffuse reflectance absorption spectra of ZnO@C, PHI, and ZnO@C / PHI prepared in steps (2), (3), and (4) of Example 1 of the present invention. Figure 7 The transient photocurrent diagrams of ZnO@C, PHI and ZnO@C / PHI prepared in steps (2) and (3) and (4) of Example 1 of the present invention are shown. Figure 8 These are the electrochemical impedance spectroscopy diagrams of ZnO@C, PHI, and ZnO@C / PHI prepared in steps (2), (3), and (4) of Example 1 of the present invention; Figure 9 The graph shows the photocatalytic H2O2 production performance of the ZnO@C, PHI and ZnO@C / PHI catalysts prepared in steps (2) and (3) and (4) of Example 1 of this invention in pure water. Figure 10 These are the photocatalytic H2O2 production performance graphs of the ZnO@C / PHI catalysts prepared in Examples 1-4 and Comparative Example 1 of this invention in pure water; Figure 11 This is a graph showing the photocatalytic H2O2 production performance of the ZnO@C / PHI catalyst prepared in Examples 1 and 5-6 of this invention in pure water; Figure 12 This is a graph showing the photocatalytic H2O2 production performance of the ZnO@C / PHI catalyst prepared in Examples 1 and 7-8 of this invention in pure water; Figure 13 The graph shows the photocatalytic H2O2 production performance of the ZnO@C / PHI catalyst prepared in Example 7 of this invention in aqueous solution and bicarbonate solution under different atmospheres. Figure 14 The ZnO@C / PHI catalyst prepared in Example 7 of this invention is used in... 13 Photocatalytic production of H2O2 from C-carbonate aqueous solution 13 C-labeled peroxybicarbonate NMR image; Figure 15 These are the photocatalytic performance diagrams of the ZnO@C, PHI, and ZnO@C / PHI catalysts prepared in steps (2) and (3) of Examples 7 and 1 of the present invention for the generation of hydroxyl radicals in aqueous solution; Figure 16 This is a graph showing the performance of the ZnO@C, PHI and ZnO@C / PHI catalysts prepared in steps (2) and (3) of Example 7 and Example 1 of this invention in the photocatalytic degradation of sulfamethoxazole in aqueous solution. Detailed Implementation

[0013] In view of the shortcomings of the existing technology, the inventors of this case, through long-term research and extensive practice, have been able to propose the technical solution of this invention, which mainly provides a carbon-coated zinc oxide / carbon nitride (ZnO@C / PHI) heterojunction photocatalyst and its preparation method, as well as its application in photocatalytic production of H2O2 and the construction of a photocatalytic peroxybicarbonate advanced oxidation system in water treatment.

[0014] Graphite carbon nitride, as a typical polymer semiconductor, possesses suitable band gap, appropriate band positions, tunable electronic structure, good visible light absorption, and chemical stability. Zinc oxide photocatalysts exhibit high UV photocatalytic activity, strong oxidation capacity, low cost, environmental friendliness, good biocompatibility, and diverse morphologies, making them suitable for large-scale applications and consistent with sustainable development principles. Furthermore, the conduction band position of carbon nitride satisfies the oxygen reduction reaction to produce hydrogen peroxide, while the valence band position of zinc oxide provides sufficient conditions for the water oxidation reaction to produce oxygen or hydrogen peroxide. The design of heterojunction composite photocatalysts can address issues such as low charge migration rate, easy recombination of photogenerated electrons and holes, low quantum efficiency, low reactivity, slow kinetics of water oxidation, and limited visible light absorption range. Simultaneously, a photocatalytic peroxybicarbonate advanced oxidation system is constructed by combining in-situ generated hydrogen peroxide with bicarbonate ions. Through the action of photogenerated electrons, it promotes the decomposition of hydrogen peroxide into reactive oxygen species such as hydroxyl radicals and carbonate radicals, significantly broadening the degradation pathway of pollutants and improving degradation efficiency. This addresses the problem of low utilization efficiency of hydrogen peroxide in water treatment, the low pH requirement, large amount of oxidant input, and sludge generation in the Fenton reaction, and the issue of adding hydrogen peroxide in the peroxybicarbonate advanced oxidation system.

[0015] The following will further explain the technical solution, its implementation process, and its principles. However, it should be understood that within the scope of this invention, the above-mentioned technical features of this invention and the technical features specifically described below (in embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described in detail here.

[0016] As one aspect of the technical solution of the present invention, the carbon-coated zinc oxide / carbon nitride (ZnO@C / PHI) heterojunction photocatalyst is composed of carbon-coated zinc oxide nanosheets (ZnO@C) and carbon nitride nanosheets (PHI) cross-linked with each other through a carbon layer, wherein a heterojunction is formed between the carbon-coated zinc oxide nanosheets (ZnO@C) and carbon nitride nanosheets (PHI).

[0017] In some embodiments, the mass ratio of the carbon-coated zinc oxide nanosheets to the carbon nitride nanosheets is 1:0.5~2.

[0018] In some embodiments, the carbon-coated zinc oxide nanosheets are obtained by coating zinc oxide nanoparticles with a carbon layer.

[0019] The zinc oxide nanoparticles have a diameter of 10-20 nm.

[0020] Furthermore, the thickness of the carbon layer is 1~8 nm.

[0021] In some preferred embodiments, the carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst is a composite photocatalytic material formed by carbon-coated zinc oxide (ZnO) nanoparticles with a diameter of 10-20 nm and carbon nitride (PHI) through grinding and high-temperature calcination; the PHI exhibits a nanosheet morphology; and the ZnO has a wurtzite crystal structure.

[0022] The carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst provided by this invention is constructed by introducing a carbon layer between zinc oxide and carbon nitride at their interface, causing them to crosslink. Furthermore, the carbon layer acts as an electron conduction layer, enabling the carbon-coated zinc oxide and carbon nitride to form a heterojunction and construct a built-in electric field. Carbon nitride acts as a reduction photocatalyst, and zinc oxide as an oxidation photocatalyst. The reduction photocatalyst has a more negative conduction band position, while the oxidation photocatalyst has a more positive valence band position. After their combination, the reduction and oxidation sites separate. Driven by band bending and the built-in electric field, photogenerated holes accumulate in the valence band of zinc oxide, while photogenerated electrons remain in the conduction band of carbon nitride. Therefore, this promotes the separation and migration of photogenerated charges, enhancing the redox reaction on the catalyst surface.

[0023] As another aspect of the technical solution of the present invention, the preparation method of a carbon-coated zinc oxide / carbon nitride (ZnO@C / PHI) heterojunction photocatalyst includes: mixing and grinding carbon-coated zinc oxide nanosheets and carbon nitride nanosheets, and calcining them under inert gas protection.

[0024] Specifically, the preparation method of the carbon-coated zinc oxide / carbon nitride (ZnO@C / PHI) heterojunction photocatalyst includes: The zinc source, surfactant, and organic ligand are mixed and stirred to promote the self-assembly of zinc ions in the zinc source with the organic ligand to form a zinc oxide precursor. The zinc oxide precursor was mixed and stirred with tannic acid solution, the solid phase was collected, and then subjected to a first high-temperature calcination to obtain carbon-coated zinc oxide nanomaterials. The carbon-coated zinc oxide nanomaterials and carbon nitride nanosheets were mixed, ground, and then subjected to a second high-temperature calcination to obtain a carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst.

[0025] In some embodiments, the zinc source may include one or a combination of two of zinc acetate (Zn(CH3COO)2), zinc nitrate (Zn(NO3)2), etc., but is not limited thereto.

[0026] In some embodiments, the organic ligand may include one or more combinations of 2-methylimidazole, terephthalic acid, pyromellitic acid, etc., but is not limited thereto.

[0027] In some embodiments, the surfactant may include one or more of hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, dodecyltrimethylammonium bromide, etc., but is not limited thereto.

[0028] In some embodiments, the preparation method specifically includes: mixing a zinc source, an organic ligand, and a surfactant evenly, stirring continuously at room temperature for 6 to 18 hours, preferably 6 to 12 hours, centrifuging, washing, and drying to obtain a zinc oxide precursor.

[0029] In some embodiments, the molar ratio of the surfactant to the zinc source is 0.1~0.5:10~25.

[0030] In some preferred embodiments, the preparation method specifically includes: dissolving a surfactant in water, then sequentially adding a zinc source and a 2-methylimidazole aqueous solution, continuously stirring the reaction at room temperature for 6-18 h, centrifuging, washing, and drying to obtain a zinc oxide precursor. The drying temperature is 60-100 °C, and the time is 6-18 h.

[0031] In some more preferred embodiments, the molar volume ratio of the surfactant to water is 0.1~0.5 mmol: 100~200 mL.

[0032] In some more preferred embodiments, the concentration of the 2-methylimidazole aqueous solution is 0.2~0.6 mol / L, and the volume added is 100~200 mL.

[0033] In some embodiments, the preparation method specifically includes: dissolving tannic acid in a mixed solvent of water and ethanol to form an aqueous solution of tannic acid, adding zinc oxide precursor, stirring continuously for 1-4 h, collecting the solid phase by centrifugation, and then performing a first high-temperature calcination to obtain carbon-coated zinc oxide nanomaterials.

[0034] In some implementations, the mass ratio of tannic acid to zinc oxide precursor is 1:5 to 30. Tannic acid is used as a precursor for generating the carbon layer. If the mass ratio of tannic acid to zinc oxide precursor is 1:60, it will affect the coating effect between zinc oxide and the carbon layer. There may be cases where zinc oxide is not loaded on the carbon layer, and the photocatalytic performance will be reduced.

[0035] In some more preferred embodiments, the preparation method specifically includes: dissolving 0.05 g to 0.2 g of tannic acid in a mixed solvent of 20 to 60 vol% ethanol by ultrasonication to form an aqueous solution of tannic acid.

[0036] In some preferred embodiments, the preparation method specifically includes: drying the collected solid phase at 60~100 °C for 6~18 h, then placing it in a muffle furnace and heating it to 350~450 °C at a heating rate of 2~6 °C / min, holding it for 2~5 h, and cooling it to room temperature to collect carbon-coated zinc oxide nanomaterials.

[0037] In some embodiments, the preparation method specifically includes: thoroughly grinding melamine, lithium chloride, and potassium chloride, wherein the salts such as lithium chloride and potassium chloride serve as reaction media and salt templates to promote the diffusion of reactants and accelerate the reaction process, and the mixture is subjected to a third high-temperature calcination to obtain carbon nitride nanosheets.

[0038] In some implementations, the mass ratio of melamine, lithium chloride and potassium chloride is 1~3:2~15:2~15.

[0039] In some preferred embodiments, the preparation method specifically includes: thoroughly grinding melamine, lithium chloride and potassium chloride, drying at 60~100 °C for 6~18 h, placing it in a muffle furnace, heating it to 500~580 °C at a heating rate of 2~6 °C / min in a protective atmosphere, holding it for 2~5 h, cooling it to room temperature and collecting carbon nitride nanosheets.

[0040] In some preferred embodiments, the preparation method specifically includes: grinding carbon-coated zinc oxide nanomaterials and carbon nitride nanosheets at a mass ratio of 1:0.5~2 thoroughly for 0.25~1.0 h; then, under a protective atmosphere, calcining at a temperature of 2~6℃ / min to 300~400℃ for 1~5 h to obtain a carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst. Different calcination temperatures will affect the long-term H2O2 accumulation performance.

[0041] Furthermore, the protective atmosphere includes a nitrogen atmosphere or an argon atmosphere.

[0042] In some more preferred embodiments, a method for preparing a carbon-coated zinc oxide / carbon nitride heterojunction photocatalytic material specifically includes: S1. Add zinc source (zinc acetate (Zn(CH3COO)2) or zinc nitrate (Zn(NO3)2)) and 2-methylimidazole to an aqueous solution of surfactant cetyltrimethylammonium bromide, stir continuously for 6-12 hours, centrifuge and wash to collect the precipitate to obtain ZnO precursor; S2. Dissolve tannic acid in a mixed solvent of ethanol and water, then add the ZnO precursor obtained in S1 and disperse it in the tannic acid aqueous solution. Stir continuously for 1 to 4 hours, centrifuge to collect the dry solid material, and prepare carbon-coated ZnO nanomaterials (ZnO@C) by first high-temperature calcination. S3. Melamine is thoroughly ground with lithium chloride and potassium chloride, the mixture is dried and calcined at high temperature (i.e., the third high temperature calcination) to prepare PHI nanosheets; S4. The PHI obtained in S3 and the ZnO@C obtained in S2 are thoroughly ground and then calcined at high temperature (i.e., second high-temperature calcination) to obtain the ZnO@C / PHI heterojunction photocatalytic material; wherein the mass ratio of ZnO@C to PHI is 1:0.5~2.

[0043] In some more specific implementation schemes, step S1 includes the following steps: dissolving 0.1-0.5 mmol of hexadecyltrimethylammonium bromide in 100-200 mL of ultrapure water, then adding 10-25 mmol of zinc acetate and stirring to form a transparent solution; then adding dropwise a 0.2-0.6 mol / L aqueous solution of 2-methylimidazole, and continuously stirring the reaction at room temperature for 6-18 hours to promote the self-assembly of zinc ions and ligands to form a zinc oxide precursor; collecting the solid material by centrifugation, washing it several times with deionized water, and drying it at 60-100 °C for 6-18 hours to obtain a white solid zinc oxide precursor powder.

[0044] In some more specific implementation schemes, step S2 includes the following steps: dissolving 0.05 g to 0.2 g of tannic acid in a 20 to 60 vol% ethanol aqueous solution by ultrasonication; adding zinc oxide precursor powder at a mass ratio of tannic acid to zinc oxide precursor of 1:5 to 30; stirring for 1 to 4 hours; collecting the solid material by centrifugation; drying the solid material at 60 to 100 °C for 6 to 18 hours; placing the solid material in a muffle furnace and heating it to 350 to 450 °C at a heating rate of 2 to 6 °C / min, holding it for 2 to 5 hours; cooling it to room temperature and collecting the carbon-coated zinc oxide nanomaterial ZnO@C.

[0045] In some more specific implementation schemes, step S3 includes the following steps: grinding and mixing 1-3 g of melamine with 2-15 g of lithium chloride and 2-15 g of potassium chloride until uniform, placing the mixture in a ceramic boat and covering it, then drying it at 60-100 °C for 6-18 hours, placing it in a tube furnace, and heating it to 500-580 °C (preferably 500-560 °C) at a heating rate of 2-6 °C / min under an inert atmosphere (N2 or Ar), holding it for 2-5 hours, cooling it to room temperature, collecting the yellow powder, washing it several times with deionized water, and collecting the dried solid powder to obtain carbon nitride material PHI.

[0046] Furthermore, wash with deionized water 2 to 5 times, and dry at 60 to 100 ℃ for 6 to 18 hours.

[0047] In some more specific implementation schemes, step S4 specifically includes: mixing the ZnO@C obtained in S2 and the PHI obtained in S3 at a mass ratio of 1:0.5~2 and grinding them thoroughly for 0.25~1.0 hours, placing them in a ceramic boat, putting them in a tube furnace, and heating them to 300~400 ℃ at a heating rate of 2~6 ℃ / min under an inert atmosphere (N2 or Ar), holding them for 1~5 hours, cooling them to room temperature, and collecting the yellowish-brown powder to obtain the carbon-coated zinc oxide / carbon nitride (ZnO@C / PHI) heterojunction photocatalytic material.

[0048] As another aspect of the technical solution of the present invention, it also relates to a carbon-coated zinc oxide / carbon nitride (ZnO@C / PHI) heterojunction photocatalytic material prepared by the aforementioned preparation method.

[0049] As another aspect of the technical solution of the present invention, it also relates to the application of the carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst in the fields of photocatalytic preparation of hydrogen peroxide (H2O2) or water treatment.

[0050] In some embodiments, the application includes generating hydrogen peroxide (H2O2) using oxygen molecules (O2) and water molecules (H2O) as raw materials and the carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst as a catalyst.

[0051] Specifically, using air as an O2 source, hydrogen peroxide is generated in pure water. The application includes generating H2O2 using O2 and H2O as raw materials under continuous introduction of high-purity O2 or air.

[0052] In some implementations, the application includes: using the carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst as a catalyst to construct a photocatalytic peroxybicarbonate advanced oxidation system for use in the field of water treatment, preferably in the field of organic pollutant degradation.

[0053] In some embodiments, the application includes: adding the carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst to a solution containing bicarbonate (potassium bicarbonate or sodium bicarbonate) (HCO3). - In an aqueous solution, hydrogen peroxide (H2O2) and bicarbonate (HCO3) are generated in situ by photocatalysis. - In-situ formation of peroxybicarbonate (HCO4) - ), in situ generated peroxybicarbonate (HCO4) - Under photocatalysis, it decomposes to generate hydroxyl radicals (•OH) and carbonate radicals (•CO3). - These reactive oxygen species promote the rapid degradation of organic pollutants.

[0054] As another aspect of the technical solution of the present invention, it also relates to a method for degrading organic pollutants in water using a photocatalytic peroxybicarbonate advanced oxidation system, wherein the method utilizes the above-mentioned carbon-coated zinc oxide / carbon nitride (ZnO@C / PHI) heterojunction photocatalyst as a catalyst.

[0055] In one embodiment of the present invention, the method involves using the carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst to photocatalyze the degradation of organic pollutants in a light-drenched, bicarbonate-containing, and oxygen-containing environment, utilizing the photocatalyst to photocatalyze the bicarbonate peroxide system.

[0056] In one embodiment of the present invention, the organic pollutant is sulfamethoxazole, but is not limited thereto.

[0057] The present invention also provides a method for degrading sulfamethoxazole, using air as an O2 source, and in a solution containing bicarbonate, irradiating the above-mentioned carbon-coated zinc oxide / carbon nitride (ZnO@C / PHI) heterojunction photocatalyst to photocatalyze the degradation of sulfamethoxazole in a peroxybicarbonate system.

[0058] In one embodiment of the present invention, the degradation of sulfamethoxazole by the photocatalytic peroxybicarbonate advanced oxidation system is carried out in a pH range of 6.5 to 8.5.

[0059] In one embodiment of the present invention, the catalytic material generates photogenerated electrons under photoexcitation to promote the generation of hydrogen peroxide and activates peroxybicarbonate to generate reactive oxygen species such as hydroxyl radicals and carbonate radicals, which greatly improves the efficiency of degrading organic pollutants.

[0060] In one embodiment of the present invention, the method specifically comprises: The prepared carbon-coated zinc oxide / carbon nitride (ZnO@C / PHI) heterojunction photocatalyst was dispersed at 5–50 mg in a closed reactor containing 10–60 mL of water. After stirring with air at a flow rate of 10–50 mL / min for 5–30 min, the solution was irradiated for 30 and 60 min under a 300 W xenon lamp with a wavelength range of 350–780 nm. 1–5 mL of the solution was collected at different time points and filtered through a 0.22 μL filter membrane to remove the catalyst, yielding a transparent solution. Then, 1.5 mL of the solution was taken, and 0.4 mol / L potassium iodide solution and 0.1 mol / L potassium hydrogen phthalate solution were added. After standing in the dark for 30 min, the hydrogen peroxide concentration was measured using a UV spectrophotometer.

[0061] In one embodiment of the present invention, the method specifically comprises: The prepared carbon-coated zinc oxide / carbon nitride (ZnO@C / PHI) heterojunction photocatalyst, at concentrations of 5–50 mg, was dispersed in a closed reactor containing 10–60 mL of sulfamethoxazole solution at 10–30 ppm. 0–45 mg of sodium bicarbonate was added, and the reactor was stirred with air at a flow rate of 10–50 mL / min for 5–30 min. The solution was then irradiated with a 300 W xenon lamp (wavelength range 350–780 nm) for 5, 10, 20, 30, and 40 min, with 1–5 mL of solution taken at different time points. The catalyst was removed by filtration through a 0.22 μL filter membrane, yielding a clear solution. The removal efficiency of sulfamethoxazole was then determined by high-performance liquid chromatography (HPLC). Finally, 1.5 mL of the solution was taken, and 0.4 mol / L potassium iodide solution and 0.1 mol / L potassium hydrogen phthalate solution were added. After standing in the dark for 30 min, the hydrogen peroxide concentration was measured using a UV spectrophotometer.

[0062] By employing the above technical solution, the carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst of the present invention can effectively promote the separation of photogenerated carriers, reduce the recombination rate of electron-hole pairs, and significantly improve the efficiency of photocatalytic hydrogen peroxide production in an air atmosphere. Simultaneously, the in-situ generated hydrogen peroxide can react with bicarbonate in the system to generate peroxybicarbonate with high oxidizing activity. This peroxybicarbonate is then activated through the photocatalytic process to generate reactive oxygen species such as hydroxyl radicals, further enhancing the degradation capacity of organic pollutants and achieving highly efficient degradation of organic pollutants.

[0063] The specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings, but the embodiments described do not constitute a limitation of the present invention. All modifications that are conceived or derived from the content disclosed in this invention are considered to be within the scope of protection of this invention.

[0064] All raw materials used in the embodiments of this invention were purchased from the market.

[0065] The instruments and equipment used in the following examples are all conventional equipment in the relevant fields, and the performance tests are all conducted in accordance with the requirements of conventional standards.

[0066] Example 1: Preparation of ZnO@C / PHI heterojunction photocatalytic material (1) Dissolve 0.2 mmol of hexadecyltrimethylammonium bromide in 100 mL of ultrapure water, then add 20 mmol of zinc acetate and stir to form a transparent solution; then add 100 mL of 2-methylimidazole aqueous solution with a concentration of 0.5 mol / L and stir continuously at room temperature for 12 hours to promote the self-assembly of zinc ions and ligands to form zinc oxide precursor; collect the solid material by centrifugation, wash several times with deionized water, and dry at 80 °C for 12 hours to obtain white solid zinc oxide precursor powder.

[0067] (2) Dissolve 0.1 g of tannic acid in 100 mL of 50 vol% ethanol aqueous solution by ultrasonication. Add precursor powder according to the mass ratio of tannic acid to zinc oxide precursor of 1:10, wherein the mass of zinc oxide precursor is 1 g. Stir for 2 hours, collect the solid material by centrifugation, and dry at 80 °C for 12 hours to obtain solid material. Place the solid material in a muffle furnace and calcine it at a heating rate of 5 °C / min to 420 °C for 2 hours. Cool it down to room temperature and collect the carbon-coated zinc oxide nanomaterial ZnO@C.

[0068] (3) Grind 1g of melamine, 2.7g of lithium chloride and 3.3g of potassium chloride together until uniform, place in a porcelain boat, cover and dry at 80 ℃ for 12 hours, place in a tube furnace, under inert atmosphere (N2) protection, heat to 550 ℃ at a heating rate of 2 ℃ / min, maintain for 4 hours, cool to room temperature and collect yellow powder, wash several times with deionized water, collect dry solid powder to obtain carbon nitride material PHI.

[0069] (4) Grind the ZnO@C obtained in step (2) and the PHI obtained in step (3) at a mass ratio of 1:1 for 0.5 hours, place them in a ceramic boat, put them in a tube furnace, and calcine them at a high temperature of 300 ℃ at a heating rate of 5 ℃ / min under the protection of an inert atmosphere (N2), hold for 2 hours, cool down to room temperature and collect the yellowish-brown powder to obtain carbon-coated zinc oxide / carbon nitride (ZnO@C / PHI) heterojunction photocatalytic material.

[0070] Figure 1 The transmission electron microscope (TEM) image of ZnO@C prepared in step (2) of Example 1 shows that zinc oxide nanoparticles of tens of nanometers are loaded on the carbon layer, confirming the successful preparation of zinc oxide coated with carbon layer. Figure 2 The successful preparation of zinc oxide was confirmed by observing the lattice fringes of zinc oxide through high-magnification transmission electron microscopy (HR-TEM).

[0071] Figure 3 The image is a transmission electron microscope (TEM) image of carbon nitride PHI prepared in step (3) of Example 1, showing that it exhibits a special nanosheet stacked structure.

[0072] Figure 4 The images shown are transmission electron microscope (TEM) and high-power transmission electron microscope (HR-TEM) images of the ZnO@C / PHI heterojunction photocatalytic material prepared in step (4) of Example 1. The composite of ZnO@C and PHI can be observed, and the ZnO@C and PHI components at the edge of the composite material can be clearly seen. Furthermore, oxidative lattice fringes can be observed, with lattice fringes spacings of 0.246 nm, 0.280 nm and 0.260 nm, respectively, corresponding to the (101), (100) and (002) crystal planes of zinc oxide.

[0073] Figure 5 The X-ray diffraction spectra of ZnO@C, PHI and ZnO@C / PHI prepared in steps (2) and (3) and (4) of Example 1 show diffraction peaks of zinc oxide and carbon nitride. The diffraction peaks of zinc oxide and carbon nitride appear simultaneously in the ZnO@C / PHI heterojunction photocatalytic material, which confirms the successful preparation of the photocatalytic material.

[0074] Figure 6 The UV-Vis diffuse reflectance absorption spectra of ZnO@C, PHI and ZnO@C / PHI prepared in steps (2) and (3) and (4) of Example 1 show that after ZnO@C and PHI are constructed into heterojunction photocatalysts, their light absorption intensity in the visible light region is enhanced.

[0075] Figure 7 The transient photocurrent diagrams of ZnO@C, PHI, and ZnO@C / PHI prepared in steps (2) and (3) and (4) of Example 1 are shown. The diagrams show that the photocurrent intensity of ZnO@C and PHI is enhanced after constructing heterojunction photocatalysts, which confirms that the photogenerated charge separation and migration of ZnO@C / PHI heterojunction photocatalytic materials are promoted.

[0076] Figure 8 The images show the electrochemical impedance spectroscopy of ZnO@C, PHI, and ZnO@C / PHI prepared in steps (2), (3), and (4) of Example 1. The spectra show that the electrochemical impedance of ZnO@C and PHI decreases after constructing heterojunction photocatalysts, further confirming that the photogenerated charge separation and migration of ZnO@C / PHI heterojunction photocatalytic materials are promoted.

[0077] Comparative Example 1 The preparation method of the ZnO@C / PHI heterojunction photocatalytic material in this comparative example is the same as that in Example 1 except for the following differences: In step (2), the mass ratio of tannic acid to zinc oxide precursor is 0:1.

[0078] Example 2 The preparation method of the ZnO@C / PHI heterojunction photocatalytic material in this embodiment is the same as that in Example 1 except for the following differences: In step (2), the mass ratio of tannic acid to zinc oxide precursor is 1:5.

[0079] Example 3 The preparation method of the ZnO@C / PHI heterojunction photocatalytic material in this embodiment is the same as that in Example 1 except for the following differences: In step (2), the mass ratio of tannic acid to zinc oxide precursor is 1:20.

[0080] Example 4 The preparation method of the ZnO@C / PHI heterojunction photocatalytic material in this embodiment is the same as that in Example 1 except for the following differences: In step (2), the mass ratio of tannic acid to zinc oxide precursor is 1:30.

[0081] Example 5 The preparation method of the ZnO@C / PHI heterojunction photocatalytic material in this embodiment is the same as that in Example 1 except for the following differences: In step (4), the mass ratio of carbon-coated zinc oxide to carbon nitride is 1:2.

[0082] Example 6 The preparation method of the ZnO@C / PHI heterojunction photocatalytic material in this embodiment is the same as that in Example 1 except for the following differences: In step (4), the mass ratio of carbon-coated zinc oxide to carbon nitride is 2:1.

[0083] Example 7 The preparation method of the ZnO@C / PHI heterojunction photocatalytic material in this embodiment is the same as that in Example 1 except for the following differences: In step (4), the high-temperature calcination temperature is 350 ℃.

[0084] Example 8 The preparation method of the ZnO@C / PHI heterojunction photocatalytic material in this embodiment is the same as that in Example 1 except for the following differences: In step (4), the high-temperature calcination temperature is 400 ℃.

[0085] Example 1-1 (1) Dissolve 0.1 mmol of sodium dodecylbenzenesulfonate in 150 mL of ultrapure water, then add 10 mmol of zinc nitrate and stir to form a transparent solution; then add 150 mL of 0.2 mol / L terephthalic acid aqueous solution and stir continuously at room temperature for 6 hours to promote the self-assembly of zinc ions and ligands to form zinc oxide precursor; collect the solid material by centrifugation, wash several times with deionized water, and dry at 60 °C for 18 hours to obtain white solid zinc oxide precursor powder.

[0086] (2) Dissolve 0.1 g of tannic acid in 100 mL of 20 vol% ethanol aqueous solution by ultrasonication. Add precursor powder according to the mass ratio of tannic acid to zinc oxide precursor of 1:10, wherein the mass of zinc oxide precursor is 1 g. Stir for 1 hour, collect the solid material by centrifugation, and dry at 60 °C for 18 hours to obtain solid material. Place the solid material in a muffle furnace and calcine it at a heating rate of 2 °C / min to 350 °C. Maintain the temperature for 3 hours, cool to room temperature and collect carbon-coated zinc oxide nanomaterial ZnO@C.

[0087] (3) Grind 1g of melamine, 2g of lithium chloride and 2g of potassium chloride together and mix them evenly. Place them in a porcelain boat, cover it, and dry it at 60 ℃ for 18 hours. Place it in a tube furnace and calcine it at 500 ℃ under an inert atmosphere (N2) with a heating rate of 3 ℃ / min. Hold it for 5 hours, cool it down to room temperature and collect the yellow powder. Wash it several times with deionized water and collect the dry solid powder to obtain carbon nitride material PHI.

[0088] (4) Grind the ZnO@C obtained in step (2) and the PHI obtained in step (3) at a mass ratio of 1:1 for 0.25 hours, place them in a ceramic boat, put them in a tube furnace, and calcine them at a high temperature of 300 ℃ at a heating rate of 2 ℃ / min under the protection of an inert atmosphere (N2), hold for 5 hours, cool down to room temperature and collect the yellowish-brown powder to obtain carbon-coated zinc oxide / carbon nitride (ZnO@C / PHI) heterojunction photocatalytic material.

[0089] Examples 1-2 (1) Dissolve 0.5 mmol of dodecyltrimethylammonium bromide in 200 mL of ultrapure water, then add 25 mmol of zinc nitrate and stir to form a transparent solution; then add dropwise 200 mL of 0.6 mol / L pyromellitic acid aqueous solution and stir continuously at room temperature for 18 hours to promote the self-assembly of zinc ions and ligands to form zinc oxide precursor; collect the solid material by centrifugation, wash several times with deionized water, and dry at 100 °C for 6 hours to obtain white solid zinc oxide precursor powder.

[0090] (2) Dissolve 0.1 g of tannic acid in 100 mL of 60 vol% ethanol aqueous solution by ultrasonication. Add precursor powder according to the mass ratio of tannic acid to zinc oxide precursor of 1:10, wherein the mass of zinc oxide precursor is 1 g. Stir for 4 hours, collect the solid material by centrifugation, and dry at 100 °C for 6 hours to obtain solid material. Place the solid material in a muffle furnace and calcine it at a heating rate of 6 °C / min to 450 °C. Maintain the temperature for 5 hours, cool to room temperature and collect carbon-coated zinc oxide nanomaterial ZnO@C.

[0091] (3) Grind 1g of melamine, 5g of lithium chloride and 5g of potassium chloride together and mix them evenly. Place them in a porcelain boat, cover it, and dry it at 100 ℃ for 6 hours. Place it in a tube furnace and calcine it at 580 ℃ under an inert atmosphere (N2) with a heating rate of 6 ℃ / min. Hold it for 2 hours, cool it down to room temperature and collect the yellow powder. Wash it several times with deionized water and collect the dry solid powder to obtain carbon nitride material PHI.

[0092] (4) Grind the ZnO@C obtained in step (2) and the PHI obtained in step (3) at a mass ratio of 1:1 for 1.0 hours, place them in a ceramic boat, put them in a tube furnace, and calcine them at a high temperature of 400 ℃ under an inert atmosphere (N2) with a heating rate of 6 ℃ / min. Hold the temperature for 1 hour, cool it down to room temperature, and collect the yellowish-brown powder to obtain carbon-coated zinc oxide / carbon nitride (ZnO@C / PHI) heterojunction photocatalytic material.

[0093] Example 9 In this embodiment, 25 mg of the ZnO@C, PHI, and ZnO@C / PHI heterojunction photocatalyst materials prepared in Examples 1-8 were dispersed in a closed reactor containing 50 mL of water. After stirring for 10 min under an O2 atmosphere with a flow rate of 20 mL / min, the solution was irradiated for 30 and 60 min at different time points under a 300 W xenon lamp with a wavelength range of 350-780 nm. The catalyst was filtered out using a 0.22 μL filter membrane to obtain a transparent solution. Then, 0.4 mol / L potassium iodide solution and 0.1 mol / L potassium hydrogen phthalate were added. After standing in the dark for 30 min, the hydrogen peroxide concentration was detected using a UV spectrophotometer.

[0094] Figure 9 This is a comparison chart of the photocatalytic production of hydrogen peroxide (H2O2) in pure water by the ZnO@C, PHI and ZnO@C / PHI catalysts prepared in steps (2) and (3) and (4) of Example 1. As can be seen from the chart, the ZnO@C / PHI heterojunction photocatalyst exhibits the best performance, with a hydrogen peroxide concentration of 507 µmol / L produced in one hour.

[0095] Figure 10 The graph shows a comparison of the photocatalytic hydrogen peroxide (H2O2) production performance of the ZnO@C / PHI catalysts prepared in Examples 1-4 and Comparative Example 1 in pure water. As can be seen from the graph, the photocatalytic hydrogen peroxide production performance is best when the mass ratio of tannic acid to zinc oxide precursor is 1:10.

[0096] Figure 11 This is a comparison chart of the photocatalytic hydrogen peroxide (H2O2) production performance of the ZnO@C / PHI catalysts prepared in Examples 1 and 5-6 in pure water. As can be seen from the chart, the photocatalytic hydrogen peroxide production performance is best when the mass ratio of ZnO@C to PHI is 1:1.

[0097] Figure 12The graph shows a comparison of the photocatalytic hydrogen peroxide (H2O2) production performance of the ZnO@C / PHI catalysts prepared in Examples 1 and 7-8 in pure water. As can be seen from the graph, the photocatalytic hydrogen peroxide production performance is best when the high-temperature calcination temperature in step (4) is 350℃.

[0098] Example 10 In this embodiment, 25 mg of the ZnO@C / PHI heterojunction photocatalyst material prepared in Example 7 was dispersed in a closed reactor containing 50 mL of water. After stirring for 10 min under O2, air, and N2 atmospheres with a flow rate of 20 mL / min, the solution was irradiated for 30 and 60 min at different time points using a 300 W xenon lamp with a wavelength range of 350~780 nm as the light source. The catalyst was filtered out using a 0.22 μL filter membrane to obtain a transparent solution. Then, 0.4 mol / L potassium iodide solution and 0.1 mol / L potassium hydrogen phthalate were added. After standing in the dark for 30 min, the hydrogen peroxide concentration was detected using a UV spectrophotometer.

[0099] Figure 13 This is a comparison chart of the photocatalytic hydrogen peroxide (H2O2) production performance of the ZnO@C / PHI catalyst prepared in Example 7 in aqueous solution under different atmospheres. As can be seen from the chart, the photocatalytic hydrogen peroxide production performance is not much different in O2 atmosphere and air atmosphere, while the performance is poor in N2 atmosphere.

[0100] Example 11 In this embodiment, 25 mg of the ZnO@C / PHI heterojunction photocatalyst material prepared in Example 7 was dispersed in a closed reactor containing 50 mL of aqueous solution of 21 mg sodium bicarbonate. After stirring for 10 min under O2, air, and N2 atmospheres with a flow rate of 20 mL / min, the solution was irradiated for 30 and 60 min at different time points using a 300 W xenon lamp with a wavelength range of 350~780 nm as the light source. The catalyst was filtered out using a 0.22 μL filter membrane to obtain a transparent solution. Then, 0.4 mol / L potassium iodide solution and 0.1 mol / L potassium hydrogen phthalate were added. After standing in the dark for 30 min, the hydrogen peroxide concentration was detected using a UV spectrophotometer.

[0101] Figure 13 This is a comparison of the photocatalytic hydrogen peroxide (H2O2) production performance of the ZnO@C / PHI catalyst prepared in Example 7 in bicarbonate solutions under different atmospheres. As can be seen from the figure, the addition of bicarbonate under O2 atmosphere and air atmosphere leads to a slight decrease in the photocatalytic hydrogen peroxide production performance, because hydrogen peroxide reacts with bicarbonate through an equilibrium reaction to generate peroxybicarbonate.

[0102] Example 12 In this embodiment, 25 mg of the ZnO@C / PHI heterojunction photocatalyst material prepared in Example 7 was dispersed in a solution containing 21 mg of... 13 In a closed reactor containing 25 mL of a 50 vol% deuterium aqueous solution of sodium bicarbonate, an O2 atmosphere with a flow rate of 20 mL / min was introduced and stirred for 10 min. Then, the solution was irradiated for 30 and 60 min at different time points using a 300 W xenon lamp with a wavelength range of 350–780 nm as the light source. The catalyst was filtered out using a 0.22 μL filter membrane to obtain a transparent solution, which was then placed in an NMR tube for nuclear magnetic resonance (NMR) testing.

[0103] Figure 14 The ZnO@C / PHI catalyst prepared in Example 7 was subjected to O2 atmosphere. 13 In the photocatalytic reaction of C bicarbonate aqueous solution to produce H2O2 13 The NMR spectrum of C-labeled peroxybicarbonate shows that, as can be seen from the figure, [the following was observed]. 13 The formation of C-peroxybicarbonate.

[0104] Example 13 In this embodiment, 25 mg of ZnO@C, PHI, and ZnO@C / PHI catalysts prepared in steps (2) and (3) of Example 7 and Example 1, and 21 mg of sodium bicarbonate (NaHCO3) were dissolved in 50 ml of an aqueous solution containing 3 mM terephthalic acid (TPA). Before irradiation, the suspension was stirred with air for 10 min. The solution was irradiated for 15, 30, 45, and 60 mins using a 300 W xenon lamp with a wavelength range of 350~780 nm as the light source. At different time points, 5 mL of the solution was taken and filtered to remove the catalyst using a 0.22 μL filter membrane to obtain a transparent solution. The concentration of generated HTPA was measured by fluorescence spectroscopy. Finally, the cumulative concentration of generated hydroxyl radicals could be calculated based on the established correlation relationship.

[0105] Figure 15 This is a comparison of the photocatalytic hydroxyl radical production performance of the ZnO@C, PHI, and ZnO@C / PHI catalysts prepared in steps (2) and (3) of Example 7 and Example 1 in different aqueous solutions under air atmosphere. As can be seen from the figure, the ZnO@C / PHI heterojunction photocatalyst produces the best concentration of hydroxyl radicals in the presence of bicarbonate, which confirms that bicarbonate peroxide can be activated to generate hydroxyl radicals during the photocatalytic reaction, confirms the successful construction of the photocatalytic bicarbonate advanced oxidation system, and improves the utilization efficiency of hydrogen peroxide.

[0106] Example 14 In this embodiment, 25 mg of ZnO@C, PHI, and ZnO@C / PHI catalysts prepared in Examples 7 and 1 (2) and (3) were dispersed in a closed reactor containing 50 mL of sulfamethoxazole (SMX) solution with 20 ppm, and 21 mg of sodium bicarbonate was added. After stirring with air at a flow rate of 20 mL / min for 10 min, 3 mL of the solution was taken at different time points of 5, 10, 20, 30, and 40 min under a 300W xenon lamp with a wavelength range of 350~780 nm as the light source. The catalyst was filtered off with a 0.22 μL filter membrane to obtain a transparent solution, and the removal efficiency of sulfamethoxazole was detected by high performance liquid chromatography.

[0107] Figure 16 This is a comparison of the photocatalytic degradation performance of ZnO@C, PHI, and ZnO@C / PHI catalysts prepared in steps (2) and (3) of Example 7 and Example 1 in different aqueous solutions under air atmosphere. As can be seen from the figure, the ZnO@C / PHI heterojunction photocatalyst has the best performance in degrading sulfamethoxazole in the presence of bicarbonate, which further confirms the successful construction of the photocatalytic peroxybicarbonate advanced oxidation system and promotes the degradation of sulfamethoxazole.

[0108] The method for testing the concentration of hydrogen peroxide used in the above embodiments is as follows: Hydrogen peroxide and KI can form a yellow solution. The absorbance at 350 nm is measured using a UV spectrophotometer, and the concentration of hydrogen peroxide is calculated using Beer-Lambert's law. Specifically, at regular intervals, 3 mL of the reaction solution is taken, and the catalyst powder is removed using a 0.22 μL 13 mm nylon needle filter. Then, 1 mL of potassium hydrogen phthalate solution (0.1 M) and 1 mL of potassium iodide (0.4 M) are added. After reacting for more than 30 minutes, the solution is diluted several times. Finally, the absorbance of the solution is measured using a UV spectrophotometer, and the concentration of hydrogen peroxide is calculated.

[0109] The method for detecting the concentration of hydroxyl radicals used in the above embodiments is as follows: the reaction of hydroxyl radicals with terephthalic acid (TPA) generates the fluorescent product 2-hydroxyterephthalic acid (HTPA). This allows for the quantitative analysis of the hydroxyl radicals generated in the system. HTPA can be excited at a wavelength of 315 nm and emits fluorescence at a wavelength of 425 nm. Therefore, since the concentration of HTPA is directly proportional to the peak intensity at 425 nm, it can be determined using formula C. [羟基自由基] =C [HTPA]The concentration of hydroxyl radicals was calculated at 35%. The specific steps were as follows: In a sealed 100 mL reactor, 25 mg of catalyst and 21 mg of sodium bicarbonate (NaHCO3) were dissolved in 50 mL of an aqueous solution containing 3 mM terephthalic acid (TPA). Before irradiation, the suspension was aerated and stirred for 10 min. The solution was irradiated for 15, 30, 45, and 60 mins using a 300 W xenon lamp with a wavelength range of 350–780 nm. At each time point, 5 mL of the solution was taken, filtered through a 0.22 μL filter to remove the catalyst, and the concentration of generated HTPA was determined using a fluorescence spectrometer. Finally, based on the established correlation, the cumulative concentration of generated hydroxyl radicals was calculated.

[0110] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0111] The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Therefore, although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst, characterized in that, The carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst is composed of carbon-coated zinc oxide nanosheets and carbon nitride nanosheets cross-linked together through a carbon layer, and a heterojunction is formed between the carbon-coated zinc oxide nanosheets and carbon nitride nanosheets.

2. The carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst according to claim 1, characterized in that: The mass ratio of the carbon-coated zinc oxide nanosheets to the carbon nitride nanosheets is 1:0.5~2; And / or, the carbon-coated zinc oxide nanosheets are obtained by coating zinc oxide nanoparticles with a carbon layer. Preferably, the diameter of the zinc oxide nanoparticles is 10~20 nm, and preferably, the thickness of the carbon layer is 1~8 nm.

3. A method for preparing a carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst, characterized in that, include: The zinc source, surfactant, and organic ligand are mixed and stirred to promote the self-assembly of zinc ions in the zinc source with the organic ligand to form a zinc oxide precursor. The zinc oxide precursor was mixed and stirred with tannic acid solution, the solid phase was collected, and then subjected to a first high-temperature calcination to obtain carbon-coated zinc oxide nanomaterials. The carbon-coated zinc oxide nanomaterials and carbon nitride nanosheets were mixed, ground, and then subjected to a second high-temperature calcination to obtain a carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst.

4. The preparation method according to claim 3, characterized in that: The zinc source includes one or a combination of two of zinc acetate and zinc nitrate; and / or, the organic ligand includes one or a combination of two of 2-methylimidazole, terephthalic acid, and trimesic acid; and / or, the surfactant includes one or a combination of two of hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, and dodecyltrimethylammonium bromide. And / or, the preparation method includes: mixing a zinc source, an organic ligand and a surfactant evenly, stirring continuously at room temperature for 6 to 18 hours, preferably 6 to 12 hours, centrifuging, washing and drying to obtain a zinc oxide precursor; And / or, the molar ratio of the surfactant to the zinc source is 0.1~0.5:10~25; Preferably, the preparation method includes: dissolving a surfactant in water, then sequentially adding a zinc source and a 2-methylimidazole aqueous solution, continuously stirring the reaction at room temperature for 6-18 h, centrifuging, washing and drying to obtain a zinc oxide precursor; particularly preferably, the drying temperature is 60-100 °C and the time is 6-18 h. Preferably, the molar volume ratio of the surfactant to water is 0.1~0.5 mmol: 100~200 mL; Preferably, the concentration of the 2-methylimidazole aqueous solution is 0.2~0.6 mol / L, and the added volume is 100~200 mL.

5. The preparation method according to claim 3, characterized in that, include: Tannic acid was dissolved in a mixed solvent of water and ethanol to form an aqueous solution of tannic acid. Zinc oxide precursor was then added and stirred continuously for 1-4 hours. The solid phase was collected by centrifugation and then subjected to a first high-temperature calcination to obtain carbon-coated zinc oxide nanomaterials. And / or, the mass ratio of the tannic acid to the zinc oxide precursor is 1:5~30; Preferably, the preparation method includes: dissolving 0.05 g to 0.2 g of tannic acid in a mixed solvent of 20 to 60 vol% ethanol by ultrasonication to form an aqueous solution of tannic acid; Preferably, the preparation method includes: drying the collected solid phase at 60~100 ℃ for 6~18 h, then placing it in a muffle furnace, heating it to 350~450 ℃ at a heating rate of 2~6 ℃ / min, holding it for 2~5 h, and cooling it to room temperature to collect carbon-coated zinc oxide nanomaterials.

6. The preparation method according to claim 3, characterized in that, include: Melamine, lithium chloride and potassium chloride were thoroughly ground, and the resulting mixture was subjected to a third high-temperature calcination to obtain carbon nitride nanosheets. And / or, the mass ratio of melamine, lithium chloride and potassium chloride is 1~3:2~15:2~15; Preferably, the preparation method includes: grinding melamine, lithium chloride and potassium chloride thoroughly, drying at 60~100 ℃ for 6~18 h, placing it in a muffle furnace, heating it to 500~580 ℃ at a heating rate of 2~6 ℃ / min in a protective atmosphere, holding it for 2~5 h, cooling it to room temperature and collecting carbon nitride nanosheets. And / or, the preparation method includes: grinding carbon-coated zinc oxide nanomaterials and carbon nitride nanosheets at a mass ratio of 1:0.5~2 for 0.25~1.0 h, and then calcining them at 300~400℃ at a heating rate of 2~6 ℃ / min in a protective atmosphere for 1~5 h to obtain a carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst; Preferably, the protective atmosphere includes a nitrogen atmosphere or an argon atmosphere.

7. A carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst prepared by any one of claims 3 to 6.

8. The application of the carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst according to any one of claims 1 to 2 and 7 in the field of photocatalytic preparation of hydrogen peroxide or water treatment.

9. The application according to claim 8, characterized in that, The application includes: using oxygen molecules and water molecules as raw materials, and the carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst as a catalyst, to generate hydrogen peroxide; And / or, the applications include: using the carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst as a catalyst to construct a photocatalytic peroxybicarbonate advanced oxidation system for use in the field of water treatment, especially in the field of organic pollutant degradation; Preferably, the application includes: adding the carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst to an aqueous solution containing bicarbonate, whereby the photocatalyst-generated hydrogen peroxide reacts with the bicarbonate to form peroxybicarbonate, which then decomposes under photocatalysis to generate hydroxyl radicals and carbonate radicals, thereby promoting the degradation of organic pollutants.

10. A method for degrading organic pollutants in water using a photocatalytic percarbonate advanced oxidation system, characterized in that, include: In light-, bicarbonate-containing, and oxygen-containing environments, the carbon-coated zinc oxide / carbon nitride heterojunction photocatalyst is used to photocatalyze the degradation of peroxybicarbonate system for organic pollutants; Preferably, the organic pollutant includes sulfamethoxazole.

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