Preparation Of Bi₅O₇I And Its Heterojunction By Hydrolysis And Study On Its Photocatalytic Properties

The large-scale industrialization process of human society has caused increasingly serious environmental pollution and energy shortage.Photocatalytic technology can make use of inexhaustible solar energy to treat water and atmospheric pollutants,produce hydrogen,and reduce CO₂ to fuels.Therefore,it is a technology with great prospects for dealing with environment and energy issues.Bi₅O₇I,as a new photocatalyst,has a unique one-dimensional rod structure and shows good performance in treating pollutants in water.However,Bi₅O₇I has poor absorption of visible light and high recombination rate of photogenerated electron-hole.Besides,the preparation and modification of Bi₅O₇I suffer from high temperature,high stress and long reaction time.In order to overcome its defects,we prepared Bi₅O₇I by a fast and facile hydrolysis way.The surface modification of as-synthesized Bi₅O₇I was carried out,and heterojunction materials based on this Bi₅O₇I was constructed to improve its visible light absorption capacity and separation efficiency of photogenerated carriers.The specific research contents are as follows:（1）The Bi₅O₇I photocatalyst was prepared by hydrolysis way and modified by Hexadecyl Trimethyl Ammonium Bromide（CTAB）,Sodium Dodecyl Benzene Sulfonate（SDBS）and Polyvinyl Pyrrolidone（PVP）surfactants.The experimental results showed that PVP-Bi₅O₇I had the highest photocatalytic activity and the degradation efficiency was twice that of the pure Bi₅O₇I sample.Further tests showed that PVP-Bi₅O₇I had higher specific surface area and higher photocurrent responsiveness,which improved the photocatalytic activity of B Bi₅O₇I.（2）The Bi₅O₇I and BiOBr_0.2I_0.8 photocatalysts were coprecipitated in solution by hydrolysis to form BiOBr_0.2I_0.8/Bi₅O₇I heterojunction photocatalyst.The experiments showed that the BiOBr_0.2I_0.8/Bi₅O₇I heterojunction photocatalyst had higher photocatalytic activity in comparison to the pure Bi₅O₇I,BiOBr_0.2I_0.8 and physically mixtures of them.The construction of the heterojunction successfully increased the separation efficiency of photogenerated charge carriers and light absorption of Bi₅O₇I.（3）The Bi₅O₇I was modified by SDBS,which is an anionic surfactant.Then,the SDBS-Bi₅O₇I/BiOBr_0.5I_0.5 heterojunction photocatalyst was prepared by hydrolysis method.The interface area of the heterojunction photocatalyst was greatly increased.Experiments showed that SDBS-Bi₅O₇I/BiOBr_0.5I_0.5 effectively promoted the transfer and separation of charge,thereby improving its photocatalytic activity.