A cocatalyst-free CdS nanorod/ZnS nanoparticle composite for high-performance visible-light-driven hydrogen production from water

Abstract

Highly efficient, visible-light-induced hydrogen (H₂) production via water splitting can be achieved without the help of a cocatalyst by using a noble-metal-free core–shell photocatalyst, in which zinc sulfide (ZnS) nanoparticles as the protective shell are anchored on the surface of cadmium sulfide nanorods (CdS NRs). Due to the close interfacial contact of component semiconductors, the electronic structure of CdS is strongly coupled with that of ZnS nanoparticles, leading to efficient transfer of charge carriers between them and the improvement of the CdS photostability. The CdS/ZnS NR photocatalyst showed much higher catalytic activity for H₂ production than CdS NRs and ZnS under visible light irradiation (λ > 420 nm), which is probably due to fast transfer of the photogenerated charge carriers and/or electron tunneling in the one-dimensional core–shell nanorod structure. Under optimal conditions, the highest hydrogen evolution rate reached 239 μmol h⁻¹ mg⁻¹, which is much greater than ZnS and CdS NRs and also among the best cocatalyst-free photocatalysts for H₂ production. The average apparent quantum yield can be achieved as ∼16.8% after 8 h of irradiation (monochromatic light at 420 nm ± 5 nm). A possible mechanism for the photocatalytic reaction based on CdS/ZnS NRs is also discussed.