Electronic and optical competence of TiO2/BiVO4 nanocomposites in the photocatalytic processes

Abstract

Nanocomposites with different ratios of titanium dioxide and bismuth vanadate [TiO₂]/[BiVO₄] give rise to compatible electronic band structure alignment at their interfaces to ensure enhanced photoactivated charge transfer under visible light. The sol-gel method and suitable post-synthesis thermal treatments were used to synthesize different compositions with stabilized anatase phase of TiO₂ and monoclinic scheelite polymorph BiVO₄. Structural, electronic and optical characterizations were performed and the results were analysed as a function of the stoichiometry, in which both crystalline structures show a clear junction formation among their characteristic stacking planes. Photocatalytic and (photo) electrochemical responses of the nanocomposites were investigated and tested for the degradation of azo dyes (Acid Blue-113, AB-113) (~ 99%) under visible light radiation. The nanocomposite with a mass ratio of (1:10) shows the highest photocatalytic efficiency compared to the other compositions. HRTEM images showed marked regions in which both crystalline structures form a clear junction and their characteristic planes. However, the increase of BiVO₄ content in the network overcomes the photocatalytic activity due to the decrease in the reduction potential of the photo-generated electrons with high recombination rates.