| Bismuth oxyhalide?BiOX,X=Cl,Br,I?is widely used in solar photovoltaic conversion,green organic synthesis and environmental pollutant treatment and other fields,with its unique layered crystal structure and adjustable energy band and electronic structure,as well as the advantages of low price,wide source and non-toxicity.However,the bismuth oxyhalide synthesized by traditional hydrothermal method still has problems that need to be solved,such as low specific surface area,high photogenerated charge recombination rate,short carrier diffusion distance,and spontaneous growth into a large-sized structure,resulting in its limited photocatalytic activity.Among many controllable methods,the adjustment of oxygen vacancy defects can not only expand the light absorption range,but also effectively improve the efficiency of photo-generated charge separation,thereby significantly improving the catalytic activity of the photocatalyst.The research work in this paper is mainly focus on the prepartion of oxygen-vacancy-enriched bismuth oxyhalide photocatalyst with high catalytic activity through an efficient,simple and environmentally friendly synthetic route to purify various environmental pollutants and achieve selective oxidation of toluene C?sp3?-H chemical bonds.The main research contents and achievements of this article are as follows:?1?We prepared a cluster-like bismuth oxychloride nanoparticles in a mixed solution of ethylene glycol and water with the volume ratio of 4:1 through the polyvinylpyrrolidone-assisted hydrolysis method in room-temperature.The photocatalyst prepared by this method has the advantages of the high yield,stability and large specific surface area,it has excellent catalytic properties in the photo-degradation of Rhodamine B and the photo-reduction of Cr?VI?and can be used repeatedly.In addition,we conducted an in-depth discussion on the reason why the catalyst has highly active photocatalytic activity,and found that due to the large specific surface area of the cluster-like bismuth oxychloride nanoclusters,a large number of surface hydroxyl groups can be spontaneously converted into oxygen vacancies during the photocatalytic process,and the energy level and electronic structure of the bismuth oxychloride nanoclusters with rich oxygen vacancies will be changed,which greatly improves the photogenerated charge separation efficiency and the redox ability of the catalyst.This provides a reference for the development of new high-efficiency photocatalysts,and provides an important material basis and theoretical reference for the practical application of pollutant degradation,heavy metal ion reduction,and catalyzed oxidation.?2?We synthesized the BiOBr ultra-thin nanosheets by the electrolyte precipitation method assisted by poly?sodium 4-styrenesufonate?.With the help of the large specific surface area and oxygen vacancy defects brought by the ultra-thin nanosheet structure,we successfully improved the photocatalytic selective oxidation rate of toluene.Moreover,by changing the ratio of halogen,the effect of BiOX on the photocatalytic selective oxidation performance of toluene was adjusted.Among them,BiOBr has the best photocatalytic oxidation capacity of toluene due to the appropriate band gap and energy level,its conversion rate of toluene reached 3.54%,and the benzaldehyde synthesis rate reached 3379?mol g-1 h-1.In addition,Pt metal nanoparticles were loaded on the surface of the synthesized BiOBr ultra-thin nanosheets by photo-reduction,which promoted the separation of photogenerated charges,which increased the toluene conversion rate to 4.15%and the synthesis rate of benzaldehyde reached 3647?mol g-1 h-1.This work provides an environment-friendly method for the preparation of ultra-thin BiOBr nanosheets with oxygen-enriched vacancies at room temperature,and the synthesized catalyst is suitable for the photocatalytic selective oxidation of toluene,which provides an important material basis for green organic synthesis. |
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