Electron density modulation of NiCo 2 S 4 nanowires by nitrogen incorporation for highly efficient hydrogen evolution catalysis.

Metal sulfides for hydrogen evolution catalysis typically suffer from unfavorable hydrogen desorption properties due to the strong interaction between the adsorbed H and the intensely electronegative sulfur. Here, we demonstrate a general strategy to improve the hydrogen evolution catalysis of metal sulfides by modulating the surface electron densities. The N modulated NiCo ₂ S ₄ nanowire arrays exhibit an overpotential of 41 mV at 10 mA cm ^-2 and a Tafel slope of 37 mV dec ^-1 , which are very close to the performance of the benchmark Pt/C in alkaline condition. X-ray photoelectron spectroscopy, synchrotron-based X-ray absorption spectroscopy, and density functional theory studies consistently confirm the surface electron densities of NiCo ₂ S ₄ have been effectively manipulated by N doping. The capability to modulate the electron densities of the catalytic sites could provide valuable insights for the rational design of highly efficient catalysts for hydrogen evolution and beyond.