We report a detailed theoretical investigation on the possible reaction mechanisms of CO oxidation catalyzed by a single Ti atom supported on divacancy defective graphene (TiDVG). The reaction between the adsorbed O2 with CO molecules on TiDVG is compared via three different mechanisms, i.e. Eley-Rideal (ER), Langmuir-Hinshelwood (LH) and termolecular Eley-Rideal (TER). According to our results, the energy barrier for the rate determining step of CO + O2 reaction in the TER mechanism is smaller than those of ER and LH ones. This can be attributed to the significant mixing of electronic states of adsorbed CO and O2 at the reaction site, as well as due to a sizable charge-transfer from the surface to these molecules. On the other hand, the calculated adsorption energies indicate that the coadsorption of O2 and CO molecules is slightly more energetically favored with respect to the coadsorption of two CO molecules. This result together with the relatively small reaction barriers reveal that the LH mechanism is also possible to occur at low temperature. Our results reported here suggest that TiDVG can be regarded as a green, low-cost and highly active catalyst for CO oxidation at room temperature.
