Titania-morphology-dependent dual-perimeter-sites catalysis by Au/TiO2 catalysts in low-temperature CO oxidation

Abstract Au/TiO 2 catalysts for low-temperature CO oxidation exhibit dual-perimeter-sites catalysis in which CO molecules adsorbed at both Au and TiO 2 surfaces diffuse to Au–TiO 2 perimeters and are oxidized into CO 2 . Via a comprehensive in situ DRIFTS study of CO adsorption and oxidation on Au/TiO 2 catalysts with different TiO 2 morphologies predominantly exposing {0 0 1}, {1 0 0}, and {1 0 1} facets, we report that such dual-perimeter-sites catalysis depends sensitively on TiO 2 morphology and facets. Adsorbed CO molecules remain stable on TiO 2 surfaces up to 223 K. The migration of CO molecules from TiO 2 to Au–TiO 2 perimeter sites depends on the catalytic activity of Au–TiO 2 perimeter sites. Dual-perimeter-sites catalysis occurs within Au/TiO 2 {1 0 0} and Au/TiO 2 {1 0 1} catalysts with catalytically active Au–TiO 2 perimeter sites that exhibit large coverage gradients between CO molecules adsorbed at Ti and Au sites, facilitating the migration of CO molecules from TiO 2 to the Au–TiO 2 perimeter sites, but seldom within Au/TiO 2 {0 0 1} catalysts with catalytically inactive Au–TiO 2 perimeter sites that exhibits few coverage gradients between CO molecules adsorbed at Ti and Au sites. These results provide novel insights into the structure–activity relationship in Au/TiO 2 catalysts for low-temperature CO oxidation.