Boosting Highly Active Exposed Mo Atoms by Fine-Tuning S-Vacancies of MoS 2 -Based Materials for Efficient Hydrogen Evolution.

Guided by the theoretical calculation, achieving an efficient hydrogen evolution reaction (HER) by S-vacancy engineering toward MoS 2 -based materials is quite challenging due to the contradictory relationship between the adsorption free energy of hydrogen atoms (Δ G H ) of the exposed Mo atoms (EMAs) and the number of EMAs per unit area ( N EMAs ). Herein, we demonstrate a novel one-pot incorporating-assisted compositing strategy to realize fine-tuning the concentration of S-vacancies ( C S-vacancies ) of MoS 2 -based materials to boost highly active EMAs for efficient HER. In our strategy, S-vacancies are modulated into basal planes of MoS 2 via decreasing the formation energy of S-vacancies by oxygen incorporation; moreover, C S-vacancies of the basal planes is precisely regulated by simply controlling the molar amount of the Co precursor based on the electron injection effect. At low or excessively high C S-vacancies , the as-synthesized electrocatalysts lack "highly active EMAs" in quantity or nature. The balance between the intrinsic activity of EMAs and N EMAs is realized for boosting EMAs with high catalytic performance. The optimal electrocatalysts exhibit excellent activity and stability at fine-tuning C S-vacancies to 9.61%. Our results will pave a novel strategy for unlocking the potential of an inert basal plane in MoS 2 for high-performance HER.