Reaction Mechanisms for CO Catalytic Oxidation by N₂O on Fe-Embedded Graphene

Catalytic conversion of hazardous gases can solve many of the environmental problems caused by them. We performed a density functional theory (DFT) study with the Perdew–Burke–Ernzerhof (PBE) functional to investigate the CO oxidation by using N₂O as an oxidizing agent over an iron-embedded graphene (Fe-Graphene) catalyst. The N₂O molecule was first decomposed on the Fe site yielding the N₂ molecule and an Fe–O intermediate, which was an active species for the CO oxidation. The activation energy for the N₂O decomposition step was predicted to be 8 kcal/mol. According to the population analysis, the graphene acted as both the electron withdrawing and donating support to assist the charge transfer between the Fe atom and the probe molecules, which are important for the reaction. The reaction was found to be less facile when the Fe site was first covered by the CO which has a higher adsorption energy than that of the N₂O (−10.0 vs −33.6 kcal/mol). The reaction proceeded via a concerted transition structure and required an activation energy of 19.2 kcal/mol when the CO was prior adsorbed. Thus, control of the adsorbing molecules over Fe-Graphene might be a key factor for the activity of the catalyst. With the higher catalytic activities of Fe-embedded graphene compared to other typical catalysts, this may open new avenues in searching for oxidation of CO at an economical cost