Graphene Defects Trap Atomic Ni Species for Hydrogen and Oxygen Evolution Reactions

Downsizing the catalyst to atomic scale provides an effective way to maximize the atom efficiency and enhance activity for electrocatalysis. Here, we report a concept whereby graphene defects trap atomic Ni species (aNi) inside to form an integrity (aNi@defect). X-ray adsorption characterization and density-functional-theory calculation revealed that the diverse defects in graphene can induce different local electronic densities of state (DOSs) of aNi, which suggests that aNi@defect serves as an active site for unique electrocatalytic reactions. As examples, aNi@G585 is responsible for the oxygen evolution reaction (OER), and aNi@G5775 activates the hydrogen evolution reaction (HER). The derived catalyst exhibits exceptionally good activity for both HER and OER, e.g., an overpotential of 70 mV at 10 mA/cm(2) for HER (analogous to the commercial Pt/C) and 270 mV at 10 mA/cm(2) for OER (much superior to that of Ir oxide).