Engineering Ni-NO 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-NO/NCNFs catalyst. Unlike the traditional Ni-N coordination configuration, each nickel atom in this Ni-NO framework is stabilized within a rare and well-defined NO coordination environment. This distinctive local structure is conclusively characterized using single-crystal X-ray diffraction and X-ray absorption spectroscopy. Consequently, the Ni-NO/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. 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.