Porous direct Z-scheme heterostructures of S-deficient CoS/CdS hexagonal nanoplates for robust photocatalytic H2 generation

Abstract

Photocatalytic water-splitting with Z-scheme semiconductor heterojunctions is a promising way to achieve renewable solar fuels. Nevertheless, development of earth-abundant direct Z-scheme photocatalytic systems for efficient H₂ production is still underdeveloped. In this work, porous heterostructures of S-deficient CoS/CdS hexagonal nanoplates (HNPs) were fabricated for the first time through a self-template approach combined with a solvothermal process. As indicated by scanning Kelvin probe microscopy and ˙OH radical measurements, such a CoS/CdS heterojunction follows the Z-scheme charge transfer pathway. Noticeably, these unique CoS/CdS HNPs demonstrated excellent photocatalytic activity and stability for the H₂ evolution reaction (HER) under visible-light irradiation (λ >400 nm). Specifically, the optimal HER rate is as high as 39.29 mmol g⁻¹ h⁻¹ (corresponding to the apparent quantum yield of 14.5% at 400 nm), approximately 152, 112, and 51 times that of CoS, CdS, and 3 wt% Pt-loaded CdS, respectively. The exceptional HER capability of CoS/CdS HNPs could be associated with their outstanding visible-light harvesting capability, efficient Z-scheme charge separation, and abundant H₂ evolution active sites. The findings indicated here could impel the rational design of high-performance Z-scheme photocatalysts for energy and environmental applications.