Oxygen Vacancy Induced Charge Transfer in All Inorganic S‐Scheme Heterojunction for Efficient CO ₂ Photoreduction to Solar Fuels

ABSTRACT The construction of all‐inorganic S‐scheme heterojunctions with optimized charge dynamics and defect properties represents a promising strategy for advancing CO 2 photoreduction. This work demonstrates the successful synthesis of a metal oxide/sulfide MoO 3‐x /Cd 0.5 Zn 0.5 S heterojunction through an in situ hydrothermal method, which achieves remarkable photocatalytic performance for CO 2 ‐to‐solar fuels conversion. The combined evidence from X‐ray photoelectron spectroscopy (XPS) analysis and density functional theory calculations confirms the formation of an internal electric field at the heterointerface, while in situ irradiated XPS provides direct verification of the S‐scheme electron‐hole migration and recombination mechanism. Furthermore, electrochemical measurements elucidate the critical role of the enhanced oxygen vacancy concentration in inducing the directional charge transfer pathways. The optimal MoO 3‐x /Cd 0.5 Zn 0.5 S heterojunction exhibits CO and CH 4 production rates of 183.0 and 77.6 µmol g −1 h −1 under full‐spectrum irradiation, which are 13.9 and 9.6 times higher than those of pristine MoO 3‐x , respectively. The markedly improved performance is ascribed to the synergistic interaction among enhanced charge separation facilitated by the distinctive S‐scheme mechanism, the presence of oxygen vacancies at the interface, and the efficient photothermal effects. This study offers valuable insights into the strategic design of high‐performance photocatalytic systems through the integration of defect engineering and heterojunction construction.