Synthesis,Modification And Photocatalytic Performances Of Bismuth Ferrite Photocatalyst

Photocatalysis has been regarded as one of the promising technologies for solving the problems of energy shortage and environmental pollutions.Recently,BiFeO₃?BFO?has attracted a great deal of attention because of its potential utilization in photocatalysis.However,BFO materials encounter some real problems,such as low separation efficiency,rapid recombination of photogenerated electronhole pairs and lack of active sites during the practical photocatalytic reactions.In this work,herein,we firstly synthesized pure BFO through a modified hydrothermal method,and then made several modifications to it.The photocatalytic properties of as-prepared BFO materials were evaluated and their photocatalytic mechanism was tentatively proposed.The main contents in this work are given as follows: 1.Synthesis and characterizations of pure BiFeO₃Pure BiFeO₃ material was synthesized through the coupling of co-precipitation and a modified hydrothermal method.Experimental results demonstrate that pure BFO has good crystallinity and low band gap,which can well respond to visible light.The as-prepared BFO material can decompose methyl orange under visible light irradiation,and the photodegradation efficiency is about 15%.2.Synthesis of Heterojunction CuO/BiFeO₃ Composite Photocatalysts andphotocatalytic evaluationA novel p-n heterojunction CuO/BFO composite photocatalyst for visible light photodegradation of environmental pollutants was successfully prepared through an impregnation process.It was revealed that a p-n heterostructure was constructed at the interface between CuO and BFO particle.The photocatalytic efficiency for degradation of methyl orange under visible light irradiation was much higher than that of pure BFO and CuO.When the loading content of CuO was 15%,the optimal photocatalytic degradation efficiency was achieved up to 50%,which was more than 3 times higher than that of pure BFO and CuO.The enhanced photocatalytic performance was mainly attributed to the formation of p-n heterojunction interface structure of CuO/BFO,which could facilitate the efficient separation of photogenerated electron-hole pairs,thus greatly improving the photocatalytic activity.3.Synthesis,characterization and photocatalytic mechanism of Pt/BiFeO₃composite photocatalystDifferent amounts of the cocatalyst Pt nanoparticles were successfully deposited on the surface of BFO particles through a wet impregnation process.SEM and TEM images showed that quasi-spherical Pt particles with an average particle size of ca.10 nm were well dispersed on the surface of BFO particles.The photocatalytic experiments demonstrated that the loading of Pt cocatalyst could effectively enhance the photocatalytic activity of BFO under visible light irradiation.The MO degradation activity of the Pt/BFO sample containing 1.0 wt% Pt was 5 times that of the pure BFO sample.Furthermore,the Pt/BFO photocatalysts showed a good stability during recycling experiment even in acidic condition.Electron Paramagnetic Resonance?EPR?measurements and trapping experiments give evidences that the predominant active species in the photocatalytic process was O₂^-? rather than ?OH or photo-generated holes.The enhanced photocatalytic activity of BFO by loading Pt cocatalyst could be attributed to the heterojunction formation of the Schottky barrier between BFO and Pt particles,which would facilitate photogenerated electron-hole separation and thus improve the photocatalytic activity of BFO.