Au@TiO₂ Core–Shell Composites for the Photocatalytic Reduction of CO₂

Au/TiO₂ catalysts in different geometrical arrangements were designed to explore the role of morphology and structural properties for the photocatalytic reduction of CO₂ with H₂O in the gas-phase. The most active sample was a Au@TiO₂ core–shell catalyst with additional Au nanoparticles (NPs) deposited on the outer surface of the TiO₂ shell. CH₄ and CO are the primary carbon-containing products. Large amounts of H₂ are additionally formed by photocatalytic H₂O splitting. Shell thickness plays a critical role. The highest yields were observed with the thickest layer of TiO₂, stressing the importance of the semiconductor for the reaction. Commercial TiO₂ with and without Au NPs was less active in the production of CH₄ and CO. The enhanced activation of CO₂ on the core–shell system is concluded to result from electronic interaction between the gold core, the titania shell, and the Au NPs on the outer surface. The improved exposure of Au−TiO₂ interface contributes to the beneficial effect.