Steering the selectivity in CO2 reduction on highly active Ru/TiO2 catalysts: Support particle size effects.

[Display omitted] • TiO 2 particle size can control selectivity of Ru/TiO 2 catalysts in CO 2 reduction. • Larger TiO 2 particle favor CO 2 methanation vs. CO formation after HT treatment. • O-vacancy formation upon high-temperature (HT) treatment. • O-vacancy formation is preferred on catalysts with smaller TiO 2 particles. • Formation of charged Ru sites due to electronic metal–support interactions (EMSIs). Aiming at a better understanding of the functioning of oxide-supported Ru catalysts in the reduction of CO 2 , a highly attractive reaction from ecologic reasons, we systematically investigated the influence of the support particle size on the performance of highly active Ru/TiO 2 catalysts. Employing mixed rutile-anatase supported catalysts with different TiO 2 particle size, but similar Ru particle size and loading, we found that after a reductive high-temperature (HT) treatment their selectivity can be controlled by the TiO 2 particle size, from 100% methanation to 100% CO formation. Comprehensive characterization of the catalysts shows that the changes in reaction behavior are paralleled by significant modifications of their structural, chemical and electronic properties. We propose that the change in reaction characteristics is due to a HT-induced increase in O-vacancies and charge transfer to Ru interface atoms, which is more pronounced for high-surface-area catalysts. We see this approach as interesting strategy for tailoring catalyst properties. [ABSTRACT FROM AUTHOR]