The Structure Engineering And Photocatalytic Performance Of Bismuth Oxyhalide(BiOX)-based Photocatalyst

With the rapid development of modern industry and the explosion of the world's population,energy crisis and environmental pollution issues are becoming increasingly serious.In order to prevent the further deterioration of these problems,researchers have made efforts to find alternative green energy and ways to reduce environmental pollution.Photocatalytic technology is considered to be one of the effective ways to solve these problems.In order to make full use of abundant solar energy,it is of great importance to develop a semiconductor catalyst with high catalytic activity and high efficiency of light absorption in the visible-light region.The study focuses on the modification of the Bi OX-type photocatalyst in which X is a halogen.To address the problems of Bi OX in light absorption,interfacial redox reaction and photochemical stability,several material-modification strategies have been used to improve the photocatalytic performance of the catalyst.The main research contents of this paper are covered the following aspects:(1)Bi₅O₇Br porous nanotubes with a uniform morphology and a diameter of 5 nm were successfully synthesized via a facile hydrothermal method.The structures and properties of the catalysts were characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),UV-vis diffuse reflectance spectroscopy(UV-Vis DRS)and Mott-Schottky test(MS).As a result,Bi₅O₇Br porous nanotubes have large amount of oxygen vacancies on the surface,stronger reduction ability,and more excellent photocatalytic stability compared with Bi OBr nanosheets.Moreover,Bi₅O₇Br nanotubes exhibit excellent catalytic activity in the photocatalytic degradation of Rh B.(2)Based on the preparation method of Bi₅O₇Br porous nanotubes,Bi₅O₇I porous nanotubes and unconventional-phase monoclinic Bi₅O₇I nanobelts were successfully synthesized.The as-prepared samples were characterized by XRD,TEM,XPS and UV-Vis DRS.The results indicated that the Bi₅O₇I nanotubes exhibit smaller band gap(2.31eV)than Bi₅O₇Br nanotubes,which significantly enhanced the visible-light absorption and utilization.As compared with BiOI nanosheets,Bi₅O₇I nanotubes show stronger redox capacity,richer surface oxygen vacancy and enhanced stability.In this chapter,we investigated a comprehensive study on the formation mechanism of Bi₅O₇X(X=Br,I)nanotubes based on pH value,reaction time,reaction temperature and the amount of PVP.The Bi₅O₇X(X=Br,I)nanotubes were believed to be formed through oriented attachment with the assistance of PVP.(3)In view of the deep-doping strategy,we successfully prepared Bi₄Ta O₈Br nanoplates with layered structure via molten-salt method.The as-synthesized samples were characterized by XRD,scanning electron microscopy(SEM),XPS,UV-Vis DRS and MS.Compared with Bi OBr,Bi₄TaO₈Br nanoplates exhibit excellent light absorption property,carrier separation ability and photochemical stability.Therefore,the catalyst exhibits excellent catalytic activity and selectivity in the photocatalytic reduction of nitrobenzene.