Oxygen‐Vacancy‐Mediated Evolution from MoO3/CdMoO4 Type‐II to MoO3‐x/Ov−CdMoO4 S‐Scheme Heterojunctions for Enhanced Photocatalytic H2 Evolution

Abstract

Constructing semiconductor heterojunctions has been widely recognized as an effective strategy for enhancing photocatalytic performance. However, rational regulation of interfacial charge‐transfer pathways, particularly the controllable transformation from conventional Type‐II to direct S‐scheme heterojunctions, remains a fundamental challenge. Herein, an oxygen‐vacancy‐rich MoO3‐x/Ov‐CdMoO4 S‐scheme heterostructure photocatalyst was successfully constructed through a combined defect‐engineering and in situ transformation strategy, in which oxygen vacancies drive the evolution of the MoO3/CdMoO4 Type‐II heterojunction into a direct S‐scheme heterojunction. Density functional theory calculations, together with in situ irradiated XPS and Au photodeposition experiments, reveal that oxygen vacancies reconstruct the interfacial electronic structure by introducing defect states near the Fermi level and fundamentally regulating the interfacial charge‐transfer pathway. Consequently, the optimized MoO3‐x/Ov‐CdMoO4 heterostructure exhibits a photocatalytic H2 evolution rate of 25.1 µmol g−1 h−1, approximately 6 times higher than that of pristine Ov‐CdMoO4, while maintaining excellent structural stability. More importantly, this work demonstrates that oxygen vacancies are identified as the decisive factor governing the evolution of heterojunction charge‐transfer behavior from a conventional Type‐II mechanism to a direct S‐scheme pathway, enabling efficient charge separation without sacrificing redox capability.