Theoretical evaluation on single-atom Fe doped divacancy graphene for catalytic CO and NO oxidation by O2 molecules

The geometric stability, electronic structure and surface activity of non-noble metal Fe doped divacancy graphene (555-777-graphene-Fe) sheet are investigated through density functional theory calculations. Firstly, the adsorption geometries and magnetic properties of different gas reactants on 555-777-graphene-Fe substrate are discussed in detail. It is found that the coadsorption of O-2/NO or O-2/CO molecules are more stable than that of the single NO or CO, indicating that the presence of O-2 can promote the stability of reactants. Secondly, the possible catalytic oxidation reactions for NO or CO molecule are systematically analyzed through Eley-Rideal (ER), Langmuir-Hinshelwood (LH) and new termolecular Eley-Rideal (TER) mechanisms. Based on the calculated results, the interaction between 2 NO and 2CO molecules (2 NO + 2CO -> 2CO(2) + 2 N, 2 N -> N-2) through continuous reactions (< 0.3 eV) are an energetically more favorable than those of other reactions (LH, ER and TER). Furthermore, the preadsorbed O-2 reacting with CO molecule through ER reactions are easily generated CO2 (< 0.3 eV) as compared with those of LH and TER reactions. This research provides a further theoretical study for NO and CO oxidation on graphene-based catalyst in ambient temperatures.