Direct Z-Scheme Charge Transfer via 3D/2D CdS/ReS ₂ Heterostructures with Sufficient Interfacial Coupling and Re Vacancies to Boost Solar-Driven CO ₂ Conversion

Constructing a heterostructure is an efficient strategy for achieving effective solar-driven CO 2 conversion, but severely limited by sacrificing redox ability. A Z-scheme heterostructure is considered to conquer this issue, while the effective construction remains a problem. Herein, a CdS/ReS 2 heterostructure rich in rhenium vacancies is constructed via a nonstoichiometric one-step solvothermal method. The Re vacancy optimized the energy band structure of ReS 2, transforming its energy band alignment with CdS from straddled (type I) to staggered. Furthermore, the sufficient interface coupling with CdS formed through a cation coordination competition growth method induced an interface built-in electric field (IEF) from ReS 2 to CdS, which facilitates photoholes of ReS 2 to directly recombine with photoelectrons of CdS in the space charge region and leaves photoelectrons with stronger reduction ability at the surface ReS 2 to drive CO 2 conversion, finally resulting in direct Z-scheme charge transfer (Z-ct) instead of type II. Comprehensive dynamic characterizations demonstrate that Z-ct can not only induce efficient photocarrier space separation and significantly prolong photoelectron lifetime but also reserve photocarriers’ stronger redox ability, leading to significantly improved photocatalytic CO 2 reduction efficiency (over 53 μmol g –1 h –1 ) with high selectivity for CO (98.7%). This work provides a perspective on vacancy-assisted construction of a direct Z-type heterostructure for application, contributing to the development of solar energy conversion systems.