Precise Tuning of Bilayer Ultrasmall MoS Featuring Inhibition of Carrier Recombination and Fast Surface Chemistry for Green H Evolution.

Achieving water splitting to produce green H , using the noble-metal-free MoS , has attracted huge interest from researchers. However, tuning the number of MoS layers precisely while obtaining small lateral sizes to surge the H -evolution rate is a tremendous challenge. Here, a bottom-up strategy is designed for the in situ growth of ultrasmall lateral-sized MoS with tunable layers on CdS nanorods (CN) by controlling the decomposition temperature and concentration of substrate seed (NH ) MoS . Here, the bilayer MoS and CN coupling (2L-MoS /CN) exhibits the optimum photocatalytic activity. Compared to thicker MoS , the 2L-MoS has sufficient reduction capacity to drive photocatalytic H evolution and the ultrasmall lateral size provides more active sites. Meanwhile, the indirect bandgap, in contrast to the direct bandgap of the monolayer MoS , suppresses the carrier recombination transferred to 2L-MoS . Under the synergistic effect of both, 2L-MoS /CN has fast surface chemical reactions, resulting in the photocatalytic H -evolution rate of up to 41.86 mmol g h . A novel strategy is provided here for tuning the MoS layers to achieve efficient H evolution.