Skillful promotion of charge separation via defect-mediated built-in electric field and LSPR effect for enhanced photocatalytic activity

Emerging S-scheme heterostructures offer distinct advantages in controlling charge transfer and maintaining redox capabilities. However, charge separation efficiency remains suboptimal, primarily due to the weak driving force for charge transfer. In this study, a novel plasmonic S-scheme MoO_3-x/CdS heterojunction was built to promote charge separation and enhance H₂ evolution, embodying the concept of “Two Birds with One Stone”. The rich oxygen vacancy in MoO_3-x serves as the one to this dual enhancement. First, the oxygen vacancy intensifies the internal electric field (IEF), thereby accelerating charge transfer kinetics. Second, it enhances the localized surface plasmonic resonance (LSPR) effect, boosting catalytic activity at high reaction temperatures. This strategy successfully achieves efficient charge separation through an LSPR-assisted S-scheme charge-transfer pathway, enabling long-lived electrons in the conduction band of CdS to contribute to H₂ evolution. As a result, the optimized MoO_3-x/CdS heterojunction demonstrates optimal H₂ evolution rates of 19.85 and 54.04 mmol·g⁻¹·h⁻¹ under visible light and full-spectrum irradiation, respectively. The concept of exploiting defect synergy to tune the IEF and photothermal effects in S-scheme heterostructures presents a promising strategy for the rational design of high-performance photocatalysts.