Atomic Arrangement in Metal-Doped NiS₂ Boosts the Hydrogen Evolution Reaction in Alkaline Media

We report a novel modulation strategy by introducing transition metals into NiS₂ nanosheets (NSs) to flexibly optimize the electronic configurations and atomic arrangement. The Co-NiS₂ NSs exhibit excellent hydrogen evolution reaction (HER) performance with an overpotential of 80 mV at j = 10 mA cm⁻² and long-term stability of 90 h in alkaline media. The turnover frequencies (TOFs) of 0.55 and 4.1 s⁻¹ at an overpotential of 100 and 200 mV also confirm their remarkable performance. DFT calculations reveal that the surface dopants abnormally sensitize surface Ni-3d bands in the long-range order towards higher electron-transfer activity, acting as the electron-depletion center. Meanwhile, the high lying surface S-sites possess substantially high selectivity for splitting the adsorbing H₂O that guarantee the high HER performance within alkaline conditions. This work opens opportunities for enhancing water splitting by atomic-arrangement-assisted electronic modulation via a facile doping strategy. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.