Fabrication of a hyphenated S-scheme and Schottky-junction photocatalyst based on a ternary TiNbCT_x@α-Bi₂O₃/ZnSe heterostructure with enhanced optical and photoelectrochemical properties

Environmental pollution by pharmaceuticals poses a serious threat to humans and animals. Hence there is a need for a low-cost, environmentally friendly, and sustainable treatment technology for environmental remediation. Herein, we report the synthesis of a novel TiNbCT_x@α-Bi₂O₃/ZnSe ternary photocatalytic nanocomposite, characterised using spectroscopic and microscopic techniques. Moreover, the optical and photoelectrochemical properties of the photocatalysts were assessed using spectroscopic tools such as UV–Vis DRS, EIS and PL. The synthesised pristine, cubic ZnSe, monoclinic Bi₂O₃, α-Bi₂O₃/ZnSe and the ternary composites’ crystallinity were all confirmed by the co-existence of their crystal planes and bands in XRD, SAED, and Raman spectroscopy, correspondingly. SEM and TEM analysis confirmed the anticipated characteristic morphologies and the interfaces. Improved optical properties deduced from UV–Vis DRS measurements revealed α-Bi₂O₃ and ZnSe to have band gaps of 2.7 eV and 2.41 eV, respectively. Upon creating an α-Bi₂O₃/ZnSe heterostructure and TiNbCT_x@α-Bi₂O₃/ZnSe ternary system, a red shift was observed in their band gaps, indicating improved optical properties. The electrochemical properties of the materials were determined using EIS. These were used to deduce the charge transfer kinetics of the heterostructure and ternary system, which showed TiNbCT_x@α-Bi₂O₃/ZnSe to be an outstanding photocatalyst over the synthesised pristine materials and α-Bi₂O₃/ZnSe heterostructure. The photocurrent response of the TBZ-7 % exhibited enhanced generation and separation of photoexcited charge carriers 4 folds higher than those of pristine materials. The PL spectra of the TBZ-7 % showed low intensity due to the suppression of charge recombination rates. Moreover, the Nyquist and LSV plots of TBZ-7 % presented improved charge transfer ability and a prolonged lifetime of photoinduced charge carriers (280 ms), respectively. With these enhanced properties, TiNbCT_x@α-Bi₂O₃/ZnSe ternary photocatalytic nanocomposite demonstrates the extraordinary potential for environmental remediation in degrading ARVs from water.