Unveiling the synergistic interplay of appropriate oxygen vacancies and S-scheme heterojunction structures in OVs-TiO2/g-C3N4 catalyst for efficient RhB photodegradation and H2 production

Abstract

This study presents a facile synthesis for an efficient S-scheme OVs-TiO2/g-C3N4 heterojunction (OVs-TCN) enriched with oxygen vacancies, demonstrating exceptional performance in photocatalytic RhB degradation and H2 production. Controlled introduction of g-C3N4 into OVs-TiO2 modulates appropriate oxygen vacancies within the OVs-TCN10 heterojunction. Under visible irradiation, OVs-TCN10 achieves a remarkable 97.2 % degradation of RhB over 120 min with 5 cycles, with an apparent rate constant of 0.021 min−1. Impressively, OVs-TCN10 exhibits significant H2 production from RhB degradation, reaching a rate of 150 µmol h−1 under visible irradiation for 30 h, with a 15 % AQY at 420 nm. Experimental and DFT analyses of charge density difference, along with Mulliken analysis at the OVs-TiO2/g-C3N4 interface, confirm the existence of an intrinsic electric field flowing from g-C3N4 to OVs-TiO2. This internal electric field enhances photogenerated electron-hole separation and transfer, facilitating the redox process via the S-scheme mechanism in the heterojunction for photocatalytic RhB degradation and H2 production. This work offers new insights into the controlled defects and interfacial mechanisms in heterojunctions, propelling advanced photocatalytic applications.