Engineering Double Sulfur-Vacancy in CoS 1.097 @MoS 2 Core-Shell Heterojunctions for Hydrogen Evolution in a Wide pH Range.

Heterostructured nanomaterials have arisen as electrocatalysts with great potential for hydrogen evolution reaction (HER), considering their superiority in integrating different active components but are plagued by their insufficient active site density in a wide pH range. In this report, double sulfur-vacancy-decorated CoS 1.097 @MoS 2 core-shell heterojunctions are designed, which contain a primary structure of hollow CoS 1.097 nanocubes and a secondary structure of ultrathin MoS 2 nanosheets. Taking advantage of the core-shell type heterointerfaces and double sulfur-vacancy, the CoS 1.097 @MoS 2 catalyst exhibits pH-universal HER performance, achieving the overpotentials at 10 mA cm -2 of 190, 139, and 220 mV in 0.5 M H 2 SO 4 , 1.0 M KOH, and 1.0 M PBS, respectively. Systematic theoretical results show that the double sulfur-vacancy can endow the CoS 1.097 @MoS 2 core-shell heterojunctions with promoted electron/mass transfer and enhanced reactive kinetics, thus boosting HER performance. This work clearly demonstrates an indispensable role of double sulfur-vacancy in enhancing the electrocatalytic HER performance of core-shell type heterojunctions under a wide pH operating condition.