Cascaded BiS bridges and Ti-VS vacancy restore centers trigger parallel dual S-scheme exciton highways for ultrafast photocatalytic redox.

Abstract

The performance of photocatalysts is often limited by charge recombination and sluggish kinetics at heterojunction interfaces. This study develops a multi-strategy interfacial modulation approach by constructing BiS covalent bonds at the BiVO4/Mn0.5Cd0.5S(MCS) interface to serve as electron transport "bridges", while simultaneously filling sulfur vacancies (VS) in MCS with Ti atoms to eliminate recombination centers. This dual optimization of interfacial charge dynamics is realized in a BiVO4/MCS/TiO2(BMT) ternary system. The design facilitates an efficient dual S-scheme heterojunction that, driven by an interfacial built-in electric field, enables highly efficient separation of photogenerated carriers while maximizing redox capability. Under visible-light irradiation, the composite achieves a degradation rate of 89.51% for norfloxacin within 30 min, along with excellent cycling stability. Combined spectroscopic analysis and theoretical calculations confirm that the BiS bonds significantly reduce the interfacial charge-transfer barrier, while the Ti-VS structure effectively suppresses carrier recombination. The synergy between these two mechanisms is key to constructing an efficient S-scheme charge-transfer pathway. This work provides a clear strategy for designing high-performance photocatalytic systems through the cooperative integration of interfacial bonding and defect engineering.