Monolayer WS2 has interesting properties as a direct
bandgap semiconductor, photocatalyst, and electrocatalyst, but it is still a
significant challenge to prepare this material in colloidal form by liquidphase
exfoliation (LPE). Here, we report the preparation of 1−2 layer
semiconducting WS2 nanosheets in a yield of 18−22 wt % by a modified
LPE method that involves preintercalation with substoichometric
quantities of n-butyllithium. The exfoliated WS2 nanosheeets are ntype,
have a bandgap of ∼1.78 eV, and act as a cocatalyst with CdS
nanorods in photocatalytic hydrogen evolution using lactate as a
sacrificial electron donor. Up to a 26-fold increase in H2 evolution rate
was observed with WS2/CdS hybrids compared with their pure CdS
counterpart, and an absorbed photon quantum yield (AQE) of >60%

was measured with the optimized photocatalyst.