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

Au/TiO 2 catalysts in different geometrical arrangements were designed to explore the role of morphology and structural properties for the photocatalytic reduction of CO 2 with H 2 O in the gas‐phase. The most active sample was a Au@TiO 2 core–shell catalyst with additional Au nanoparticles (NPs) deposited on the outer surface of the TiO 2 shell. CH 4 and CO are the primary carbon‐containing products. Large amounts of H 2 are additionally formed by photocatalytic H 2 O splitting. Shell thickness plays a critical role. The highest yields were observed with the thickest layer of TiO 2 , stressing the importance of the semiconductor for the reaction. Commercial TiO 2 with and without Au NPs was less active in the production of CH 4 and CO. The enhanced activation of CO 2 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−TiO 2 interface contributes to the beneficial effect.