A Novel Single Atom Catalyst for CO Oxidation at Humid Environmental Conditions: Ni-Embedded Divacancy Graphene
The degradation for the catalyst towards CO oxidation in humid air is a common issue due to the blocking of active site by the adsorption and dissociation of water molecules. In order to evaluate the effect of humidity on the CO oxidation, the adsorption and dissociation of the common gas molecules in air, such as CO, O2, H2O, and N2 molecules on single Ni-embedded divacancy graphene (Ni-DG) have been investigated by using the first principles calculations. It is found that all the molecules keep molecular state and the adsorption energy of CO is much larger than the other molecules. In addition, the CO molecule can sufficiently substitute the pre-adsorbed O2, H2O, and N2 molecules with small energy barriers, indicating that the active site of the Ni-DG will not be blocking by the water molecules in humid environment. At most two CO molecules can be chemically adsorbed on the Ni-DG, indicating that a new termolecular Eleye-Rideal (TER) mechanism is preferred, and the energy barrier for the rate limiting step (2CO + O2 -> OCOOCO) is only 0.34 eV. Hirshfeld charge analysis shows that the charge transfer from O2-2π∗ orbital to CO-2π∗ orbital plays an important role for the CO oxidation along the TER mechanism. Overall, our result shows that the low cost Ni-DG is an efficient catalyst for CO oxidation even in humid air at low temperature.