Orbital-regulated interfacial electronic coupling endows Ni3N with superior catalytic surface for hydrogen evolution reaction

The interstitial structure and weak Ni-N interaction of NiN lead to high unoccupied d orbital energy and unsuitable orbital orientation, which consequently results in weak orbital coupling with HO and slow water dissociation kinetics for alkaline hydrogen evolution catalysis. Herein, we successfully lower the unoccupied d orbital energy of NiN to strengthen the interfacial electronic coupling by employing the strong electron pulling capability of oxygen dopants. The prepared O-NiN catalyst delivers an overpotential of 55 mV at 10 mA cm, very close to the commercial Pt/C. Refined structural characterization indicates the oxygen incorporation can decrease the electron densities around the Ni sites. Moreover, density functional theory calculation further proves the oxygen incorporation can create more unoccupied orbitals with lower energy and superior orientation for water adsorption and dissociation. The concept of orbital-regulated interfacial electronic coupling could offer a unique approach for the rational design of hydrogen evolution catalysts and beyond.