Engineered Charge Separation and Utilization in Oxygen-Vacancy-Mediated S-scheme Heterojunction for Enhanced Photoredox Catalysis

Abstract

Abstract Defect-mediated S-scheme heterojunction engineering offers a compelling strategy for advancing photocatalytic solar energy conversion. Herein, an S-scheme heterojunction photocatalyst is designed by coupling one-dimensional oxygen-vacancy-rich K2Ti8O17–x nanowires to two-dimensional g-C3N4 porous nanosheets via electrostatic self-assembly. The optimized nanocomposite exhibits substantially enhanced visible-light H2O2 production compared with the individual components while also outperforming its defect-free and physically mixed counterparts. Importantly, the oxygen vacancies trigger interfacial S-scheme charge transfer channels, which accelerate charge separation and improve photoredox capability, thereby boosting H2O2 production. Furthermore, selective 5-hydroxymethylfurfural oxidation to 2,5-diformylfuran is achieved with a nearly 4.8-fold enhanced H2O2 production rate, which not only highlights the significance of facilitated hole oxidation half-reaction in H2O2 photosynthesis but also represents a promising platform for biomass valorization. Encouragingly, the in situ-generated H2O2 can be utilized for efficient and durable environmental pollutant degradation via the photo-self-Fenton process. Experimental and theoretical analyses conclusively demonstrate the significantly enhanced photoredox catalysis mainly attributed to increased active sites, accelerated interfacial charge separation, and boosted charge utilization for surface catalytic reactions. This work provides deep insights into rational design of high-performance defect-mediated heterojunction photocatalysts for solar energy conversion and storage.