Crystal Phase-Dependent Dispersion and Catalysis of the Ag Species Supported on TiO₂ for CO Oxidation with Excess Oxygen

Abstract

Oxidation-induced dispersion of supported metal catalysts has been frequently observed in gas–solid heterogeneous reactions, while precise tailoring of the structures of restructured metals remains challenging. Here, we successfully demonstrated the feasibility of using different TiO 2 crystal phases to tune the nanostructures of restructured silver species upon CO oxidation with excess O 2 . Compared to pure anatase and rutile phases, a mixture of anatase and rutile phases (m-TiO 2 ) is more advantageous for the dispersion of supported Ag species, with a particle size distribution of 3.5 ± 0.2 nm, which is closely related to the surface OH group and defect concentrations of TiO 2 supports. Spectroscopic characterizations clearly reveal the CO oxidation catalyzed by the Ag/TiO 2 catalysts following a Mars–van Krevelen mechanism. Consequently, in addition to the Ag dispersion, a Ag/m-TiO 2 catalyst with higher active oxygen species contents and correspondingly better reducibility, relevant for CO activation and reactivity, contributes to better catalytic performance in CO oxidation. These results highlight the potential of crystal phases of oxide supports in tailoring oxidation-induced restructuring to develop efficient heterogeneous catalysts for applications.