Vacancy-engineered MoSe2/CdS hollow heterostructures boosting visible-light-induced Z-scheme photocatalysis

Abstract

Enhancing the Z-scheme photocatalysis of hollow semiconductor heterostructures via controllable vacancy engineering is intriguing yet remains under-developed to date. In this work, a hollow MoSe₂/CdS Z-scheme heterojunction was constructed by assembling S vacancy (S_V)-engineered CdS hollow spheres with few-layer MoSe₂ nanosheets, where Mo–S chemical bonds served as the high-speed channel for Z-scheme charge transmission, as validated by in situ light-irradiated X-ray photoelectron spectroscopy (XPS), surface photovoltage (SPV) spectroscopy, and ·O₂⁻ radical production measurements. Intriguingly, the Fermi level (E_f) difference between CdS and MoSe₂ can be enlarged by tuning S_V content, which helps to strengthen the internal electric field (IEF) of MoSe₂/CdS heterojunction to drive Z-scheme charge transmission efficiently. Meanwhile, MoSe₂/CdS could benefit from the enhanced light harvest and catalytic reaction kinetics facilitated by the hollow architecture. Therefore, the MoSe₂/CdS heterojunction displayed an exceptional visible-light-induced (λ > 400 nm) H₂ evolution activity of 20.49 mmol g⁻¹ h⁻¹, approximately 89.1- and 13.0-fold higher than that displayed by CdS and 3% Pt–CdS, respectively; this value also exceeded the H₂ evolution activity of many CdS-based photocatalysts reported previously. In addition, the MoSe₂/CdS heterojunction exhibited outstanding photocatalytic robustness for cyclic and long-term H₂ production. The present study may shed new insights on constructing highly active photocatalysts through the vacancy engineering of hollow-structured Z-scheme heterojunctions.