Dual Mo and Se Vacancies in Dual S-Scheme Heterojunction Suppress Charge Recombination and Boost Redox Capability for Simultaneous Removal of Tetracycline and Cr(VI)

Mo vacancy (V Mo ) and Se vacancy (V Se ) are doped into Bi 2 MoO 6 (BMO) and ZnSe, respectively, while they are mechanically ground and mixed to fabricate the dual S-scheme heterojunction. The lattice distortion is observed at the interface between V Mo -BMO and V Se -ZnSe/CdSe (V Se -ZCS) while XPS results confirm the construction of the dual S-scheme heterojunction V Mo -BMO/V Se -ZCS (V Mo+Se -BZCS). DFT simulation demonstrate that the doping of V Mo and V Se lead to more electrons transferring spontaneously through the heterojunction interfaces and promote the IEF strength accordingly. Both in-situ XPS and fs-TAS characterization prove the presence of a fast photoinduced charge transfer pathway from V Mo -BMO to V Se -ZnSe under LED light irradiation. V Mo and V Se function as the holes trapping center in V Mo -BMO and the electron trapping center in V Se -ZCS, respectively, thereby effectively suppressing the electron-hole recombination, which enhances the redox capability of V Mo+Se -BZCS together with the fast charge transferring. During the photocatalytic degradation experiments for the wastewater containing both tetracycline (TC) and Cr(VI), both the TC and the Cr(VI) degradation efficiency of V Mo+Se -BZCS are competitive under either LED or xenon lamp irradiation in comparison with some reported catalysts. Dual doping of V Mo and V Se were testified to amplify the bi-directional promotion effects (BPEs) between TC and Cr(VI).