Synthetic trends for BiVO4 photocatalysts: Molybdenum substitution vs. TiO2 and SnO2 heterojunctions

The influence of hydrothermal synthesis, thermal post-treatment at 500 degrees C and Mo content on a series of Bi1-x/3V1-xMoxO4 (0.02 < 0.15) photocatalysts was investigated for methylene blue (MB) degradation and 02 evolution. Mo incorporation stabilizes the tetragonal scheelite phase of BiVO4, thereby inducing a small blue shift of the band gap. This adverse effect can be partially compensated by incorporation of lower Mo amounts (up to ca. 4%), which stabilizes the particle morphology upon calcination. Both BiVO4@TiO2 and BiVO4:Mo@TiO2 heterojunction composites with TiO2 particle coatings in the 10 nm range were newly synthesized and displayed promising photocatalytic performance in MB degradation. Comparative studies with SnO2 heterojunctions revealed a superior influence of TiO2 deposition over SnO2 coating on both BiVO4 and Bi1-x/3V1-xMoxO4 oxide substrates. Different synthetic guidelines for BiVO4-based solid solutions and heterojunctions in photocatalytic wastewater treatment and water oxidation are discussed. (C) 2011 Elsevier Inc. All rights reserved.