Ce-V oxide catalysts supported on bimodal mesoporous SiO2 were prepared by a wet impregnation method to study their catalytic activity for SO3 decomposition, which is a key step in thermochemical water splitting cycles based on the sulfur iodine process. As-prepared Ce-V/SiO2 catalysts exhibited more than 50-fold higher turnover frequency at 600 degrees C compared to unsupported CeVO4. This is in accordance with the smaller size (13 nm) of CeVO4 particles highly dispersed in SiO2 mesopores, compared to approximately 600 nm for unsupported CeVO4 particles. The Ce-V/SiO2 catalysts exhibited a higher activity than supported V2O5 or CeO2 catalysts, which coexisted depending on the Ce/V ratio. Among the studied catalysts with different Ce/V molar ratios, the highest activity was achieved at Ce/V = 0.9, at which the greatest specific surface area of CeVO4 was attained. The catalyst demonstrated SO3 decomposition rates comparable to those of Pt/Al2O3 in a wide range of WHSV (3.6-110 g-H2SO4 g(-1) h(-1)) and no indication of noticeable deactivation during 40 h of the catalytic reaction at 650 degrees C. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.