Theoretical insights into the roles of active oxygen species in heterogeneous oxidation of CO over Mn/TiO2 catalyst

Abstract

Quantum chemistry calculations were performed to reveal the roles of the active oxygen species in the CO oxidation and the interactions between the gaseous molecules (CO, O2, CO2, etc.) and the active sites to design a highly active and low-temperature Mn/TiO2 catalyst. The results show that the Ti5a-O2b-Mn5c (TOM) coordination structure is the active center for the chemisorption of CO and O2. The dominant cycles were proposed over the TOM structure, which consist of three reaction stages, i.e., first CO oxidation → surface re-oxidation → second CO oxidation. Two kinds of active oxygen species, i.e., the lattice oxygen of TOM and the two atomic oxygen formed during the surface re-oxidation process, play critical roles in the dominant CO oxidation cycles. The energy barriers of the dominant oxidation cycles are lower than 50 kJ/mol, which explain well the high low-temperature activity of Mn/TiO2 catalyst for CO abatement.