In-situ pressure-induced BiVO4/Bi0.6Y0.4VO4 S-scheme heterojunction for enhanced photocatalytic overall water splitting activity

Step-scheme (S-scheme) heterojunctions in photocatalysts can provide novel and practical insight on promoting photogenerated carrier separation. The latter is critical in controlling the overall efficiency in one-step photoexcitation systems. In this study, a nanosized Bi0.6Y0.4VO4 solid solution was prepared by a coprecipitation method following with hydrothermal or calcination processes. The S-scheme heterojunction was fabricated by in-situ pressure-induced transformations of bismuth vanadate from the tetragonal zircon phase to the monoclinic scheelite phase, which led to the formation of BiVO4 nanoparticles with a diameter of approximately 5 nm on the surface of Bi0.6Y0.4VO4. Bi0.6Y0.4VO4 with S-scheme heterojunctions showed significantly enhanced photocatalytic overall water splitting activity compared with using bare Bi0.6Y0.4VO4. Characterization of the carrier dynamics demonstrated that a superior carrier separation through S-type heterojunctions might have caused the enhanced overall water splitting (OWS) activity. Surface photovoltage spectra and the results of selective photodeposition experiments indicated that the photogenerated holes mainly migrated to the BiVO4 nanoparticles in the heterojunction. This confirmed that the charge transfer route corresponds to an S-scheme rather than a type-II heterojunction mechanism under light illumination. This study presents a facile and efficient strategy to construct S-scheme heterojunctions through a pressure-induced phase transition. The results demonstrated that S-scheme junctions composed of different crystalline phases can boost the carrier separation capacity and eventually improve the photocatalytic OWS activity.