Preparation And Performance Of Bismuth Vanadate Composite Photocatalytic Materials With Sillen Family Bismuth Compounds Modified

Photocatalysis is a promising approach to address the issues on energy crisis and environment pollution.Bismuth Vanadate?BiVO₄?shows its potential in water splitting,CO₂reduction and organic contaminant degradation by photocatalysis because of the economical cost,adequate bandgap energy,simple synthesis process,high photostability and environmental friendliness.However,the poor separation efficiency and low transfer rate of the photo-generated electron-hole pairs limit the quantum efficiency of BiVO₄.Therefore,it is of great significance to modify BiVO₄ or combine it with other semiconductors.The main researches are as follows:1.BiVO₄/BiOBr composites with enhanced photocatalytic activity were fabricated by a CTAB-assisted polyol method through a coprecipitation process.The photocatalytic activities of as-prepared samples were evaluated by the degradation of Rhodamine B under irradiation of500 W xenon lamp.The highest degradation efficiency could reach 94.4%in 90 min when the molar ratio of V to Br was 1:1,and the apparent degradation rate constant was 0.02998 min^-1,which was 54.5 and 2.9 times higher than that of the pure BiVO₄ and BiOBr,respectively.The combination of BiVO₄ and BiOBr could increase the migration efficiency and inhibit the recombination of photo-generated electron-hole pairs indicated by electrochemical and photoluminescence analysis.Confirmed by the radical trapping experiments,holes?h⁺?and superoxide radicals?·O₂^-?were the main active species for the degradation of RhB.It was supposed that n-type BiVO₄ and p-type BiOBr could form p-n junction at their interface,promoting the transfer of photo-induced carriers by internal electric field.Furthermore,BiVO₄/BiOBr composites showed stable photocatalytic performance and structural stability after 7 consecutive recycles for the photo-degradation of RhB.2.BiVO₄/BiOCOOH composites with enhanced photocatalytic activity were fabricated by a two-step route.Pure BiVO₄ was first obtained by polyol method and then BiVO₄/BiOCOOH was formed through solvothermal treatment.The photocatalytic activities of as-prepared samples were evaluated by the degradation of RhB under simulated sunlight.When the molar ratio of BiOCOOH to BiVO₄ was 1:0.5?BBC0.5?,the sample showed the highest degradation efficiency?76.2%in 100 min?and its apparent degradation rate constant reached 1.028×10^-5min^-1,which was 188 and 3.6 times higher than that of the pure BiVO₄ and BiOCOOH,respectively.Shown by photoluminescence analysis,the intensity of fluorescence decreased effectively after the combination of BiVO₄ and BiOCOOH,which could increase the migration efficiency and inhibit the recombination of photo-generated electron-hole pairs.Confirmed by the radical trapping experiments,holes?h⁺?and superoxide radicals?·O₂^-?were the main active species for the degradation of RhB.Furthermore,BiVO₄/BiOBr composites showed relatively stable photocatalytic performance and structural stability for the photocatalytic degradation of RhB.