Direct simulation evidence of generation of oxygen vacancies at the golden cage Au16 and TiO2 (110) interface for CO oxidation.

We show Born-Oppenheimer molecular dynamics (BOMD) simulation evidence of the generation of oxygen vacancies at the golden cage Au16 and TiO2 (110) interface for CO oxidation. Unlike the conventional Langmuir-Hinshelwood (L-H) mechanism, the CO molecule adsorbed at the perimeter Au sites of Au16 tends to attack a nearby lattice oxygen atom on the TiO2 (110) surface rather than the neighboring co-adsorbed molecular O2. Our large-scale BOMD simulation provides, to our knowledge, the first real-time demonstration of feasibility of the Mars-van Krevelen (M-vK) mechanism as evidenced by the generation of oxygen vacancies on the TiO2 surface in the course of the CO oxidation. Furthermore, a comparative study of the CO oxidation at the golden cage Au18 and TiO2 interface suggests that the L-H mechanism is more favorable than the M-vK mechanism due to higher structural robustness of the Au18 cage. It appears that the selection of either M-vK or L-H mechanism for the CO oxidation is dependent on the structural fluxionality of the Au cage clusters on the TiO2 support.