阅读说明：本技术 一种硒化钨/氮化碳复合纳米片及其制备方法和应用 (Tungsten selenide/carbon nitride composite nanosheet and preparation method and application thereof ) 是由 王万军 古文泉 高艳蓬 安太成 李桂英 于 2020-05-12 设计创作，主要内容包括：本发明属于光催化材料技术领域,公开一种硒化钨/氮化碳复合纳米片及其制备方法和应用。所述硒化钨/氮化碳复合纳米片是先采用热聚合法将前驱体升温至520～560℃加热,制得体相石墨相氮化碳；然后将单质硒、钨酸钠溶解在有机溶剂中,加入硼氢化钠搅拌,再加入体相石墨相氮化碳搅拌,所得悬浊液在150～280℃进行溶剂热反应,收集粗产品,洗涤、烘干；将所得粗产品在保护气氛中在100～400℃进行煅烧后制得。该复合纳米片不含贵金属成分,且产双氧水效率高,可作为光催化剂实现在可见光下进行光催化产双氧水的应用,在环保领域具有潜在应用价值。(The invention belongs to the technical field of photocatalytic materials, and discloses a tungsten selenide/carbon nitride composite nanosheet and a preparation method and application thereof. The tungsten selenide/carbon nitride composite nanosheet is prepared by heating a precursor to 520-560 ℃ by adopting a thermal polymerization method to prepare bulk graphite phase carbon nitride; dissolving elemental selenium and sodium tungstate in an organic solvent, adding sodium borohydride, stirring, adding bulk graphite phase carbon nitride, stirring, carrying out solvothermal reaction on the obtained suspension at 150-280 ℃, collecting a crude product, washing and drying; and calcining the obtained crude product at 100-400 ℃ in a protective atmosphere to obtain the catalyst. The composite nanosheet does not contain precious metal components, is high in hydrogen peroxide production efficiency, can be used as a photocatalyst to realize the application of photocatalytic hydrogen peroxide production under visible light, and has potential application value in the field of environmental protection.)

1. The tungsten selenide/carbon nitride composite nanosheet is characterized in that a precursor is heated to 520-560 ℃ by adopting a thermal polymerization method to prepare bulk graphite phase carbon nitride; dissolving elemental selenium and sodium tungstate in an organic solvent, adding sodium borohydride, stirring, adding bulk graphite phase carbon nitride, stirring, carrying out solvothermal reaction on the obtained suspension at 150-280 ℃, collecting a crude product, washing and drying; and calcining the obtained crude product at 100-400 ℃ in a protective atmosphere to obtain the catalyst.

2. The tungsten selenide/carbon nitride composite nanosheet of claim 1, wherein the precursor is dicyandiamide, melamine, urea, or thiourea.

3. Tungsten selenide/carbon nitride composite nanoplatelets according to claim 1, wherein the organic solvent is N, N-dimethylformamide, N-methyl-pyrrolidone or dimethylsulfoxide.

4. The tungsten selenide/carbon nitride composite nanosheet of claim 1, wherein the elemental selenium, sodium tungstate and organic solvent are present in a ratio of 2 mol: 1 mol: (40-70) mL; the mass ratio of the total amount of the elemental selenium and the sodium tungstate to the mass ratio of the sodium borohydride to the bulk graphite phase carbon nitride is 3 mol: (20-300) mg: (1-10) g.

5. Tungsten selenide/carbon nitride composite nanoplatelets according to claim 1 wherein the heating time is 2-6 h; the solvothermal reaction time is 10-36 h.

6. Tungsten selenide/carbon nitride composite nanoplatelets according to claim 1, wherein the protective atmosphere is nitrogen, argon or vacuum.

7. The tungsten selenide/carbon nitride composite nanosheet of claim 1, wherein the calcination time is 2-36 hours.

8. The preparation method of tungsten selenide/carbon nitride composite nanosheets according to any one of claims 1 to 7, comprising the specific steps of:

s1, heating the precursor to 520-560 ℃ by adopting a thermal polymerization method to prepare bulk graphite phase carbon nitride;

s2, dissolving elemental selenium and sodium tungstate in an organic solvent, adding sodium borohydride, stirring, adding bulk graphite phase carbon nitride, stirring, carrying out solvothermal reaction on the obtained suspension at 150-280 ℃, collecting a crude product, washing and drying;

and S3, calcining the obtained crude product at 100-400 ℃ in a protective atmosphere to obtain the tungsten selenide/carbon nitride composite nanosheet.

9. Use of tungsten selenide/carbon nitride composite nanoplatelets according to any of claims 1-7 in the photocatalytic production of hydrogen peroxide in an aqueous system.

10. The use of tungsten selenide/carbon nitride composite nanoplatelets according to claim 9 in the photocatalytic production of hydrogen peroxide in an aqueous system, wherein the aqueous system is one or a mixture of any two of pure water, ethanol or methanol; the photoresponse wavelength range of the photocatalytic hydrogen peroxide generation is 420-700 nm.

Technical Field

The invention belongs to the technical field of photocatalytic materials, and particularly relates to a tungsten selenide/carbon nitride composite nanosheet and a preparation method and application thereof.

Background

The graphite-phase carbon nitride has a unique layered structure and excellent chemical stability, and is applied to the fields of photocatalytic hydrogen peroxide production and the like as a high-efficiency photocatalyst in recent years. However, the photo-generated electron hole recombination rate is high, and the absorption to visible light is low, so that the efficiency of generating hydrogen peroxide by photocatalysis is low, and how to improve the quantum efficiency and the yield of hydrogen peroxide by compounding the cocatalyst is a problem to be solved urgently. Tungsten selenide as a novel transition metal chalcogenide material has excellent electro-catalytic performance and visible light absorption, has a layered structure, can regulate and control an energy band structure by controlling the number of layers, and shows potential application in the fields of photocatalytic degradation and hydrogen production. Research shows that tungsten selenide can be used as a cocatalyst to capture photoproduction electrons so as to inhibit the recombination of photoproduction electron-hole pairs and improve the quantum efficiency, so that the tungsten selenide can be used as the cocatalyst to be combined with carbon nitride, and the photocatalytic hydrogen peroxide production efficiency of the carbon nitride is expected to be obviously enhanced.

At present, the synthesis of tungsten selenide is mainly prepared by high-temperature calcination and other modes, and the improvement of the photocatalytic performance is very limited. Research shows that the thickness of the layered material is reduced, so that the photoproduction electron-hole separation rate of the layered material can be further improved. Therefore, the material preparation method is developed to synthesize the tungsten selenide ultrathin nanosheets, and the tungsten selenide ultrathin nanosheets are simultaneously loaded on the carbon nitride nanosheets in situ to form a two-phase nanosheet structure, so that the tungsten selenide loaded on the carbon nitride nanosheets composite photocatalytic material can be realized. In this regard, the solvothermal method can achieve nanomaterial preparation and in-situ loading under mild conditions by adding different solvents and reducing agents. Until now, no research and report about the preparation method of the tungsten selenide/carbon nitride composite nanosheet and the related research and report about the photocatalytic hydrogen peroxide production are found.

Disclosure of Invention

In order to solve the defects and shortcomings of the prior art, the invention provides a tungsten selenide/carbon nitride composite nanosheet. The tungsten selenide/carbon nitride composite nanosheet has strong absorption of visible light and excellent photo-generated electron-hole separation efficiency, and overcomes the defects of a single carbon nitride photocatalyst in the aspect of photocatalytic hydrogen peroxide production performance.

The invention also aims to provide a preparation method of the tungsten selenide/carbon nitride composite nanosheet. The method combines ultrathin tungsten selenide and graphite-phase carbon nitride, adopts a solvothermal method to prepare the tungsten selenide/carbon nitride composite nanosheet under mild conditions, is economical and cheap, can be synthesized in one step to prepare the catalyst, and greatly reduces the application cost.

The invention further aims to provide application of the tungsten selenide/carbon nitride composite nanosheet.

The purpose of the invention is realized by the following technical scheme:

a tungsten selenide/carbon nitride composite nanosheet is characterized in that a precursor is heated to 520-560 ℃ by adopting a thermal polymerization method to prepare bulk graphite phase carbon nitride; dissolving elemental selenium and sodium tungstate in an organic solvent, adding sodium borohydride, stirring, adding bulk graphite phase carbon nitride, stirring, carrying out solvothermal reaction on the obtained suspension at 150-280 ℃, collecting a crude product, washing and drying; and calcining the obtained crude product at 100-400 ℃ in a protective atmosphere to obtain the catalyst.

Preferably, the precursor is dicyandiamide, melamine, urea or thiourea.

Preferably, the organic solvent is N, N-dimethylformamide, N-methyl-pyrrolidone or dimethyl sulfoxide.

Preferably, the dosage ratio of the elemental selenium, the sodium tungstate and the organic solvent is 2 mol: 1 mol: (40-70) mL; the mass ratio of the total amount of the elemental selenium and the sodium tungstate to the mass ratio of the sodium borohydride to the bulk graphite phase carbon nitride is 3 mol: (20-300) mg: (1-10) g.

Preferably, the heating time is 2-6 h; the solvothermal reaction time is 10-36 h.

Preferably, the protective atmosphere is nitrogen, argon or vacuum.

Preferably, the calcining time is 2-36 h.

The preparation method of the tungsten selenide/carbon nitride composite nanosheet comprises the following specific steps:

s1, heating the precursor to 520-560 ℃ by adopting a thermal polymerization method to prepare bulk graphite phase carbon nitride;

s2, dissolving elemental selenium and sodium tungstate in an organic solvent, adding sodium borohydride, stirring, adding bulk graphite phase carbon nitride, stirring, carrying out solvothermal reaction on the obtained suspension at 150-280 ℃, collecting a crude product, washing and drying;

and S3, calcining the obtained crude product at 100-400 ℃ in a protective atmosphere to obtain the tungsten selenide/carbon nitride composite nanosheet.

The tungsten selenide/carbon nitride composite nanosheet is applied to the photocatalytic production of hydrogen peroxide in a water phase system.

Preferably, the aqueous phase system is one or a mixture of any two of pure water, ethanol or methanol; the photoresponse wavelength range of the photocatalytic hydrogen peroxide generation is 420-700 nm, and the full coverage of a visible light area is basically realized.

Compared with the prior art, the invention has the following beneficial effects:

1. the thickness of the tungsten selenide in the tungsten selenide/carbon nitride composite nano sheet is less than 30nm, and the tungsten selenide is generated in the reaction process and loaded on the carbon nitride nano sheet in situ. The hydrogen peroxide production efficiency of the composite nanosheet is higher than that of pure tungsten selenide and carbon nitride, the composite nanosheet can be used as a photocatalyst to realize application of photocatalytic hydrogen peroxide production under visible light, and the ultrathin tungsten selenide serving as a cocatalyst improves the photoproduction electron-hole separation rate, so that the photocatalytic hydrogen peroxide production efficiency is greatly improved.

2. The preparation method combines ultrathin tungsten selenide and graphite-phase carbon nitride, and prepares the tungsten selenide/carbon nitride composite nanosheet by adopting a solvothermal method under mild conditions, wherein the catalyst does not contain precious metal components, and has the advantages of simple preparation method, capability of greatly reducing the preparation cost and potential application value in the field of environmental protection.

The tungsten selenide/carbon nitride composite nanosheet photocatalyst prepared by the invention is a novel high-activity photocatalytic hydrogen peroxide production material, the photoresponse wavelength range of hydrogen peroxide produced by photocatalysis is 420-700 nm, and the visible light area is basically covered completely.

Drawings

Fig. 1 is a scanning electron microscope image of tungsten selenide/tungsten selenide composite nanosheets of example 1;

fig. 2 is a graph comparing the photocatalytic hydrogen peroxide production efficiency of the tungsten selenide/tungsten selenide composite nanosheets, pure tungsten selenide and carbon nitride in example 1.

Detailed Description

The following examples are presented to further illustrate the present invention and should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.