In situ growth of monolayer <scp>WS₂</scp> on spherical <scp>CdS</scp> to enhance photocatalytic hydrogen production activity

Abstract Transition metal dichalcogenides are considered excellent cocatalysts for photocatalytic hydrogen production, and their cocatalytic activity depends on the number of layers and their contact state with the photocatalysts. Herein, monolayer WS 2 is generated by anchoring (NH 4 ) 2 WS 4 nanocrystals on the CdS spheres with a continuous surface using a solid‐state thermal reduction reaction. Due to the difference in Fermi levels between WS 2 and CdS, as well as their intimate contact, electrons from the conduction band of CdS swiftly flow to WS 2 , achieving the spatioselective redistribution of carriers. The monolayer WS 2 shortens the longitudinal distance for electron migration from CdS to WS 2 . Benefiting from the abundance of active edge sites on monolayer WS 2 , the electrons enriched on WS 2 quickly capture and reduce protons to produce H 2 . The H 2 ‐generating rate of 0.75% WS 2 /CdS is 6.95 mmol·g −1 ·h −1 , with an AQE of 44.6% at λ = 420 nm. This work not only provides a facile method to anchor monolayer 2D materials on photocatalysts but also helps to understand the mechanism by which ultrathin cocatalysts enhance photocatalytic activity.