A Generic Strategy for Preparation of TiO2/BixMyOz (M = W, Mo) Heterojunctions with Enhanced Photocatalytic Activities

Abstract Employment of nanoscale TiO 2 /Bi x M y O z (M = W, Mo) heterojunctions is one of the most promising strategies for improving the photocatalytic efficiency. However, the controllable synthesis and morphology modification of these heterojunctions are still highly challenging. In this work, we developed a generic approach to hydrothermally synthesize TiO 2 /Bi x M y O z heterojunctions and tailor their morphologies. The key of this strategy is to intentionally utilize the surface defects of TiO 2 as highly active sites to adsorb the intermediate hydrolysis-products, which is in marked contrast to the conventionally direct precipitation methods. In the subsequent hydrothermal reactions, MO 4 2- replaced the hydroxyl and nitrate radicals to form stable TiO 2 /Bi x M y O z heterojunctions, in which the second phase Bi x M y O z occupied the defect sites of TiO 2 nanobelts. Under visible light irradiation, the photocatalytic reaction rate constant of TiO 2 /Bi 2 WO 6 heterojunctions was four times higher than that of single phase Bi 2 WO 6 nanosheets, while the photocatalytic reaction rate constant of TiO 2 /Bi 3.64 Mo 0.36 O 6.55 heterojunctions exhibited a seven-fold increase compared with Bi 3.64 Mo 0.36 O 6.55 nanopaticles. The substantial enhancement of photocatalytic activity is primarily ascribed to the matching energy band structure in the TiO 2 /Bi x M y O z heterojunctions, which is able to improve the separation efficiency of photo-generated electron-hole pairs and prolong the lifetime of charge carriers in the heterojunctions.