Charge Separated ZnNb2O6/SnO2 Type-II Heterojunction Photocatalyst for Enhanced Degradation of Emerging Contaminants

Abstract

ZnNb₂O₆ and a heterojunction ZnNb₂O₆/SnO₂ have been synthesized, characterized, and studied for its photocatalytic activity against organic and pharmaceutical pollutants under UV irradiation. The characterization techniques include X-ray Diffraction (XRD), ultraviolet-visible reflectance spectroscopy (UV–vis DRS), field emission scanning electron microscopy (FESEM), photoluminescence spectra (PL), and X-ray photoelectron spectroscopy (XPS). XRD confirms single phase formation. The particles sizes of ZnNb₂O₆ and ZnNb₂O₆/SnO₂ heterojunction are in range of 170–200 nm and 110–140 nm, respectively. Bandgaps as revealed by UV–vis DRS spectra are in the range 3.14–3.71 eV. The n-n type semiconductor heterojunction ZnNb₂O₆/SnO₂ shows enhanced photocatalytic activity than the individual components for degradation of pollutants due to more effective charge carrier separation. The rate of degradation by the heterojunction is twice that of the individual components. Methyl orange degradation pathways have been proposed using HRMS analysis. This is the first report of pharmaceutical antibiotic pollutants degradation by ZnNb₂O₆.