In situ growth of monolayer WS2 on spherical CdS 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 WS₂ is generated by anchoring (NH₄)₂WS₄ nanocrystals on the CdS spheres with a continuous surface using a solid-state thermal reduction reaction. Due to the difference in Fermi levels between WS₂ and CdS, as well as their intimate contact, electrons from the conduction band of CdS swiftly flow to WS₂, achieving the spatioselective redistribution of carriers. The monolayer WS₂ shortens the longitudinal distance for electron migration from CdS to WS₂. Benefiting from the abundance of active edge sites on monolayer WS₂, the electrons enriched on WS₂ quickly capture and reduce protons to produce H₂. The H₂-generating rate of 0.75% WS₂/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.