Rational construction of S-scheme CdS quantum dots/In2O3 hollow nanotubes heterojunction for enhanced photocatalytic H2 evolution

Abstract

The rapid recombination of photogenerated carriers poses a significant limitation on the use of CdS quantum dots (QDs) in photocatalysis. Herein, the construction of a novel S-scheme heterojunction between cubic-phase CdS QDs and hollow nanotube In₂O₃ is successfully achieved using an electrostatic self-assembly method. Under visible light irradiation, all CdS-In₂O₃ composites exhibit higher hydrogen evolution efficiency compared to pure CdS QDs. Notably, the photocatalytic H₂ evolution rate of the optimal CdS-7%In₂O₃ composite is determined to be 2258.59 μmol g⁻¹ h⁻¹, approximately 12.3 times higher than that of pure CdS. The cyclic test indicates that the CdS-In₂O₃ composite maintains considerable activity even after 5 cycles, indicating its excellent stability. In situ X-ray photoelectron spectroscopy and density functional theory calculations confirm that carrier migration in CdS-In₂O₃ composites adheres to a typical S-scheme heterojunction mechanism. Additionally, a series of characterizations demonstrate that the formation of S-scheme heterojunctions between In₂O₃ and CdS inhibits charge recombination and accelerates the separation and migration of photogenerated carriers in the CdS QDs, thus achieving enhanced photocatalytic performance. This work elucidates the pivotal role of S-scheme heterojunctions in photocatalytic H₂ production and offers novel insights into the construction of effective composite photocatalysts.