Unraveling electrochemical oxygen reduction mechanism on single‐atom catalysts by a computational investigation

Summary The extension of low‐expense and stable electrocatalysts for oxygen reduction reaction (ORR) is of importance to improve the performance of metal‐air batteries and fuel cells. In this work, we unravel the ORR electrocatalytical mechanisms on a series of transition metal atom‐doped on the defect graphene (TM@sv‐graphene) by carrying out spin‐polarized first‐principles computations. The formation energy of the TM@sv‐graphene, which is related to its stability, along with the binding energy of O2, OOH, 2OH, OH, and O species are evaluated. The calculations of Gibbs free energy show that two different pathways, O* mechanism and 2OH* mechanism, of ORR compete with each other based on the structures of intermediates (OOH, 2OH, OH and O). It is found that Co, Rh, Ir, Pt, and Mn@sv‐graphene favor the O* mechanism while Ag, Au, Cd, Cu, Zn, Fe, Ni, Pd, Sc, Cr, Ti, Zr, and V@sv‐graphene strongly promote the 2OH* mechanism. The overpotential (η) of the ORR is predicted and can be a valid descriptor that manifests the catalytic activity of different TM@sv‐graphene. Among these catalysts, the Pd@sv‐graphene (η = 1.20 V) exhibits the best activity for the ORR. The results provide new insight into electrochemical mechanism of ORR for novel single‐atom electrocatalyst. The catalytic mechanisms of oxygen reduction reaction (ORR) process on TM@sv‐graphene have been explored. Two ORR pathways, O* and 2OH* mechanisms based on the structures of intermediates (OOH, 2OH, OH and O) are investigated. The overpotential is predicted to manifest the ORR activity at different TM@sv‐graphene.