Method for recovering photocatalytic stability of ZnO / ZnS homologous heterojunction catalyst

Abstract

The invention discloses a method for recovering the photocatalytic stability of a nano ZnO / ZnS homologous heterojunction catalyst. The catalyst is prepared by self-oxidation with ZnS as a precursor, and the photocatalytic performance of the catalyst can be recovered after secondary calcination. The method for recovering the stability of the catalyst nano ZnO / ZnS material is simple, the raw materials are cheap and easy to obtain, other toxic and harmful organic surfactants do not need to be additionally used, the method is safe and environmentally friendly, the preparation concept of green synthesis is met, the cost is effectively reduced, and certain technical enlightenment is provided for recovery of the photocatalytic performance of the sulfide.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic nanomaterials and relates to a method for recovering the photocatalytic stability of a ZnO / ZnS homologous heterojunction catalyst. Background Art

[0002] Metal sulfides have the advantages of suitable electronic band gap, band position, exposed active sites, high photosensitivity, large specific capacity, low redox potential, low melting point, etc. Metal sulfides are compounds formed by the combination of sulfur anions and cationic metals or semimetals to form MxSy. 2 S.M. 3 S 4 and MS 2 Sulfur is an easy-to-handle and inexpensive element that can be obtained from ammonium sulfide, thiols (decanethiol (DDT)) or organic sulfur compounds (thiourea and thioacetamide). Therefore, metal sulfides have attracted attention as catalyst / photocatalyst materials in the fields of electrocatalytic hydrogen production, photoelectrochemical (PEC) water separation, environmental remediation, batteries and sensors in the past few decades. The application of metal sulfides in batteries, capacitors, adsorption, electrochemistry and medicine has also attracted increasing attention.

[0003] Zinc sulfide (ZnS) is a II-VI compound with many advantages, such as excellent transport properties, high electron mobility, non-toxicity, insolubility in water and unique photoelectric effect. It is widely used in many fields such as optics, catalysis, magnetism, electricity, mechanics, etc. Under light, ZnS can quickly generate photogenerated electron-hole pairs and has a high reduction potential. Therefore, ZnS is a potential photocatalyst.

[0004] Zinc oxide (ZnO) is an important oxide material with a wide direct band gap of 3.37 eV. This n-type semiconductor has been extensively studied due to its large exciton binding energy (60 meV). In addition, zinc oxide has the advantages of low cost, non-toxicity, easy generation of photogenerated holes, and strong oxidation ability, and can be used to degrade environmental pollutants.

[0005] In recent years, ZnO / ZnS heterostructures have attracted much attention. Combining ZnO and ZnS to form a junction has advantages such as lower photoexcitation threshold and lower electron-hole pair recombination rate than the individual components. Coupling ZnO and ZnS to produce heterostructures is a feasible way to enhance the photoactivity of photocatalysts and expand photoreactions. Typical methods for generating junctions include coprecipitation, thermal evaporation, hydrothermal method, and ZnO and gaseous H 2 The high temperature vulcanization method of S. However, due to the instability of sulfide, its recycling rate is low. Therefore, it is very important to find a method to solve the problem of its poor stability.

[0006] The present invention discloses a method for restoring the photocatalytic stability of a ZnO / ZnS homogeneous heterojunction catalyst, wherein the obtained catalyst is subjected to secondary calcination after performance testing to restore its performance. The method effectively solves the problem of poor stability of ZnO / ZnS. Summary of the invention

[0007] The object of the present invention is to provide a method for recovering the photocatalytic stability of a ZnO / ZnS homogeneous heterojunction catalyst, which synthesizes granular ZnO / ZnS nanomaterials by calcining in a muffle furnace through cheap reactants and a simple operation method, and recovers its photocatalytic performance.

[0008] The present invention is achieved through the following technical solutions:

[0009] A method for restoring the photocatalytic stability of a ZnO / ZnS homogeneous heterojunction catalyst, characterized by being carried out according to the following steps:

[0010] The zinc source and the sulfur source are respectively placed in the solution and mixed evenly. After stirring at room temperature for 2.5 hours, the obtained solution is filtered, washed and dried, and then the precursor is placed in a muffle furnace for calcination to obtain granular nano ZnO / ZnS material. After the performance test, the solution is filtered to recover the catalyst, and secondary calcination is performed to restore its stability.

[0011] Furthermore, the order of adding the reactants is: firstly, the zinc source and sodium sulfide are put into the solution and stirred, and then the sodium sulfide solution is dropped into the zinc acetate solution to produce a white precipitate, and stirring is continued for 2.5 hours.

[0012] Furthermore, the zinc source is one of zinc acetate, zinc nitrate, zinc sulfide or zinc chloride, preferably zinc acetate.

[0013] Furthermore, the sulfur source is one of sodium sulfide, precipitated sulfur, sublimated sulfur, thiourea, and thioacetamide, preferably sodium sulfide.

[0014] Furthermore, the calcination temperature is 500°C and the holding time is 1h.

[0015] Furthermore, the molar ratio of Zn / S of the zinc acetate and sodium sulfide is 0.8:1.

[0016] Furthermore, the secondary calcination temperature is 500°C and the holding time is 1h.

[0017] Compared with the existing technology, the beneficial effects of the present invention are mainly reflected in: using cheap and easily available solid materials on the market; using a solution reaction method with simple operation and low cost for preparation; and restoring the photocatalytic performance after secondary calcination.

[0018] In summary, the chemical method for restoring the photocatalytic stability of ZnO / ZnS homologous heterojunction catalysts provided by the present invention is a relatively simple synthesis scheme, so that the present invention has certain technical inspiration for synthesizing catalysts with restored photocatalytic stability in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the X-ray diffraction pattern of the nano ZnO / ZnS material prepared in Examples 1-4 of the present invention.

[0020] Figure 2 This is a scanning electron microscope photo of the nano ZnS / ZnO material prepared by the present invention.

[0021] Figure 3 This is a hydrogen production stability curve of the nano ZnS / ZnO material prepared by the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with specific embodiments. These embodiments should be understood to be only used to illustrate the present invention and not to limit the scope of protection of the present invention. After reading the contents of the present invention, various changes or modifications made to the present invention based on the principles of the present invention also fall within the scope defined by the claims of the present invention.

[0023] Embodiment 1: A method for preparing a granular nano ZnO / ZnS material comprises the following specific steps: accurately measuring 1.834 g zinc acetate and 0.78 g sodium sulfide, respectively placing the sodium sulfide in 20 mL distilled water, placing the zinc acetate in 20 mL DMF, stirring for five minutes to fully dissolve it, then dropping the sodium sulfide solution into the zinc acetate solution to produce a white precipitate, continuing to stir for 2.5 hours to fully react it, then filtering the mixed solution, washing and drying the obtained sample as a precursor, placing the precursor in a muffle furnace, raising the temperature to 500°C at 5°C per minute, keeping the temperature for 1 hour, and collecting the product after cooling.

[0024] Example 2: A method for restoring the stability of a granular nano ZnO / ZnS material, comprising the following specific steps: accurately measuring 1.834 g zinc acetate and 0.78 g sodium sulfide, respectively placing sodium sulfide in 20 mL distilled water, placing zinc acetate in 20 mL DMF, stirring for five minutes to fully dissolve it, then dropping the sodium sulfide solution into the zinc acetate solution to produce a white precipitate, continuing to stir for 2.5 hours to fully react it, then filtering the mixed solution, washing and drying it, the obtained sample is a precursor, the precursor is placed in a muffle furnace, raised to 500°C at 5°C per minute, kept warm for 1h, and the product is collected after cooling. After the obtained product is subjected to performance testing, it is calcined twice and then the product is collected.

Claims

1. A method for restoring the photocatalytic stability of a nano ZnO / ZnS homogeneous heterojunction catalyst, comprising the following steps: The zinc source and the sulfur source are placed in an aqueous solution in a certain chemical ratio for reaction, and then the obtained solution is filtered, washed and dried. The obtained sample is placed in a muffle furnace for calcination. After the obtained ZnO / ZnS is subjected to performance testing, it is subjected to secondary calcination to restore its photocatalytic performance.

2. The nano ZnO / ZnS material prepared according to claim 1, characterized in that: The zinc source is one of zinc acetate, zinc nitrate, zinc sulfide or zinc chloride; the sulfur source is one of sodium sulfide, precipitated sulfur, sublimated sulfur, thiourea and thioacetamide.

3. The nano ZnO / ZnS material prepared according to claim 1, characterized in that: The molar ratio of zinc acetate to sodium sulfide Zn / S is 0.8:

1.

4. The nano ZnO / ZnS material prepared according to claim 1, characterized in that: The muffle furnace calcination temperature is 500°C and the holding time is 1h.

5. The nano ZnO / ZnS material prepared according to claim 1, characterized in that: The temperature of the secondary calcination was 500°C and the holding time was 1 h.

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