Mediator-free direct dual-Z-scheme Bi2S3/BiVO4/MgIn2S4 composite photocatalysts with enhanced visible-light-driven performance towards carbamazepine degradation

The development of visible-light-driven photocatalysts with high photocatalytic performance is a desired research direction of scholars for energy crisis mitigation and environment restoration. In this study, a series of highly active mediator-free direct dual-Z-scheme Bi2S3/BiVO4/MgIn2S4 hybrid photocatalysts were controllably synthesized by a in-situ growth method for the first time. XRD manifested the coexistence of MgIn2S4, BiVO4 and Bi2S3 in the as-prepared nanocomposites. The intimate 2D-2D hetero-junction interfaces between BiVO4 and MgIn2S4 as well as BiVO4 and Bi2S3 in the hybrid photocatalysts were verified by TEM and HRTEM. The photocatalytic performance of as-fabricated catalysts was estimated by the degradation of carbamazepine (CBZ) under visible light illumination. The results demonstrated that the as-constructed Bi2S3/BiVO4/MgIn2S4 composites displayed significantly improved photocatalytic activity for CBZ degradation by factors of 44.9 and 423.1 compared to MgIn2S4 and BiVO4, respectively. The enhanced photocatalytic performance of Bi2S3/BiVO4/MgIn2S4 composites was actually ascribed to the direct dual-Z-scheme migration mechanism, which was proved by XPS analysis, trapping experiments and ESR results. The formation of direct dual-Z-scheme efficiently enhanced the separation of charge carriers. Furthermore, according to DRS, the expanded light absorption in visible wavelength region also contributed to the boosted photocatalytic activity of Bi2S3/BiVO4/MgIn2S4 composites. The photocatalytic degradation products of CBZ were detected and a tentative degradation pathway was proposed.