Enhanced Activities in Alkaline Hydrogen and Oxygen Evolution Reactions on MoS Electrocatalysts by In-Plane Sulfur Defects Coupled with Transition Metal Doping.

2D transition metal disulfides (TMDs) are promising and cost-effective alternatives to noble-metal-based catalysts for hydrogen production. Activation of the inert basal plane of TMDs is crucial to improving the catalytic efficiency. Herein, introduction of in-plane sulfur vacancies (S ) and 3d transition metal dopants in concert activates the basal planes of MoS (M-S -MoS ) to achieve high activities in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Acetate introducing mild wet chemical etching removes surface S atoms facilitating subsequent cation exchange between the exposed Mo atoms and targeted metal ions in solution. Density-functional theory calculation demonstrates that the exposed 3d transition metal dopants in MoS basal planes serve as multifunctional active centers, which not only reduce ΔG but also accelerate water oxidation. As a result, the optimal Ni-S -MoS and Co-S -MoS electrocatalysts show excellent stability and alkaline HER and OER characteristics such as low overpotentials of 101 and 190 mV at 10 mA cm , respectively. The results reveal a strategy to activate the inert MoS basal planes by defect and doping co-engineering and the technique can be extended to other types of TMDs for high-efficiency electrocatalysis beyond water splitting.