Direct CO oxidation by lattice oxygen on the SnO2(110) surface: a DFT study.

As a noble-metal-free catalyst for CO oxidation, SnO2 has sparked worldwide interest owing to its highly reactive lattice oxygen atoms and low cost. The current density functional theory (DFT) results demonstrate the process of CO oxidation by lattice oxygen on the SnO2(110) surface and the recovery of the reduced surface by O2. It is found that CO can be easily oxidized on the SnO2(110) surface following the Mars-van Krevelen mechanism. The adsorbed oxygen turns into various oxygen species by transferring electron(s) to the chemisorbed oxygen, which is only found on the partially reduced SnO2-x surface, but not on the perfect SnO2(110) surface: O2(gas) ↔ O2(ad) ↔ O2(-)(ad) ↔ O2(2-)(ad) ↔ O(2-)(lattice) + O(-)(ad). The calculated stretching frequencies would help to distinguish the various adsorbed species observed in experiment and of course help in the assignment of vibrational modes in the experimental spectra.