Engineering Ni–N₂O₂ Coordination in Single-Atom Catalysts for Alkaline Hydrogen Evolution

The rational design of single-atom catalysts (SACs) with tailored coordination environments is essential for improving their electrocatalytic efficacy. This study employs a coordination engineering approach to immobilize atomically dispersed nickel atoms on nitrogen-doped carbon nanofibers (NCNFs), forming a novel Ni-N₂O₂/NCNFs catalyst. Unlike the traditional Ni-N₄ coordination configuration, each nickel atom in this Ni-N₂O₂ framework is stabilized within a rare and well-defined N₂O₂ coordination environment. This distinctive local structure is conclusively characterized using single-crystal X-ray diffraction and X-ray absorption spectroscopy. Consequently, the Ni-N₂O₂/NCNFs catalyst exhibits remarkable hydrogen evolution reaction activity in a 1.0 M KOH solution, necessitating an overpotential of merely 37 mV to attain a current density of 10 mA cm^-2. These results confirm the broad-scale applicability of the strategy for modulating the local coordination chemistry of SACs and provide novel insights that will facilitate the design of highly efficient and stable catalysts for alkaline water splitting.