Reaction mechanisms for CO catalytic oxidation on monodisperse Mo atom-embedded graphene

The geometric stability, electronic structure and catalytic activity of the Mo-embedded graphene (Mo/SV-graphene) are investigated by using the first-principle calculations. Compared with a Mo atom on pristine graphene, the Mo dopant in defective graphene exhibits more positively charged, which helps to weaken the CO adsorption and facilitates the O-2 adsorption. Besides, the two mechanisms (Langmuir-Hinshelwood, LH and Eley-Rideal, ER) for the sequential CO oxidation reactions are investigated comparison. Among the reaction processes, the coadsorption of O-2 and CO exists at the Mo/SV-graphene surface, the first step (CO + O-2 -> OOCO) with energy barrier is 0.60 eV and then form a CO2 molecule through the reaction (OOCO -> CO2 + O-ads) without any energy barrier, and thus the formation of OOCO complex is viewed as rate-controlling step. In the ER reaction, although the CO molecule reacts with the preadsorbed O-2 by the low-energy barrier (CO + O-2 -> CO3, 0.13 eV), the formation of CO3 is more stable than the generating CO2 and O-ads (0.84 eV). Hence, the LH mechanism as the starting step is energetically more favorable. The results provide the valuable guidance to fabricate graphene-based catalysis and validate the reactivity of atomic-scale catalyst.