Theoretical Insights into Nitrogen-Doped Graphene-Supported Fe, Co, and Ni as Single-Atom Catalysts for CO2 Reduction Reaction

Using single-atom catalysts for the electrochemical reduction of carbon dioxide is a promising method for excess renewable electricity as chemical energy in fuels. In this study, we have investigated single non-noble metal atoms supported on nitrogen-doped graphene (M-N4@Gr, where M = Fe, Co, Ni) as catalysts for the electrocatalytic reduction of CO2 using first-principles density functional theory and the computational hydrogen electrode model. The results show that HCOOH is the preferred product of CO2 reduction on the Ni-N4@Gr catalyst with an overpotential of 1.511 V, while Fe-N4@Gr and Co-N4@Gr prefer to reduce CO2 to CH4 with the overpotential of 0.877 and 0.687 V, respectively. The computational results revealed that the coordination environment affects d orbital occupations, leading to a difference in the spin polarization of the systems and thus affecting the performance and selectivity of catalysts. Our work may pave the way for extending single non-noble atom catalysts, which consist of earth-abundant elements, toward electrocatalytic CO2 reduction reaction by regulating coordination environments.