The atomic origin of nickel-doping-induced catalytic enhancement in MoS₂ for electrochemical hydrogen production

Transition metal (TM) doping has been demonstrated to be an efficacious way to boost the catalytic activity of molybdenum disulfide (MoS₂) for energy storage and conversion, especially for the hydrogen evolution reaction (HER). Real-space visualization of the atomic structure of Ni doped MoS₂ is crucial to understand the role of heteroatoms in enhancing electrocatalysis. By utilizing aberration corrected scanning transmission electron microscopy (STEM), we found that Ni dopants occupy Mo sites in MoS₂ synthesized by a one-pot hydrothermal method. Such selective occupation of the single-atom Ni dopants leads to significant lattice distortion and electronic structure modification of the catalytically inert basal planes of MoS₂, which are responsible for the enhanced HER catalysis of MoS₂ in both acidic and alkaline solutions.