Accelerating water dissociation kinetics of Ni3N by tuning interfacial orbital coupling

The high unoccupied d band energy of Ni₃N basically results in weak orbital coupling with water molecule, consequently leading to slow water dissociation kinetics. Herein, we demonstrate Cr doping can downshift the unoccupied d orbitals and strengthen the interfacial orbital coupling to boost the water dissociation kinetics. The prepared Cr-Ni₃N/Ni displays an impressive overpotential of 37 mV at 10 mA·cm_geo^-2, close to the benchmark Pt/C in 1.0 M KOH solution. Refined structural analysis reveals the Cr dopant exists as the Cr-N₆ states and the average d band energy of Ni₃N is also lowered. Density functional theory calculation further confirms the downshifted d band energy can strengthen the orbital coupling between the unpaired electrons in O 2p and the unoccupied state of Ni 3d, which thus facilitates the water adsorption and dissociation. The work provides a new concept to achieve on-demand functions for hydrogen evolution catalysis and beyond, by regulating the interfacial orbital coupling.