Construction of Z-scheme heterojunction based on BiOBr-nanoflakes embedded sulfonic-acid-functionalized g-C3N4 for enhanced photocatalytic removal of hazardous pollutants in aqueous media

Environmental remediation and energy production via semiconductor photocatalysis has attracted great interest in the research field because of their enormous physicochemical properties and ease of modification through forming various heterojunctions. In this work, the nanoflakes-like bismuth oxybromide embedded sulfonic acid-functionalized graphitic carbon nitride (BiOBr-NFs/g-C3N4-SAF) were prepared by hydrothermal and wet-impregnation methods. The FT-IR, XPS, and TGA studies confirm the presence of surface sulfonic groups. Meanwhile, PL, EIS, M-S, and transient photocurrent analyses indicate the suppressed recombination rate, interfacial charge transfer, band-edge potentials, and photoexcitation phenomena. The surface modification and the heterojunction formation of BiOBr-NFs/g-C3N4-SAF enable adequate band-edge potentials for photooxidation and photoreduction reactions. Among the as-synthesized photocatalysts, the 20 wt.% BiOBr-NFs/g-C3N4-SAF resulted in 98.39% of Cr(VI) photoreduction and 99.88% of RhB photooxidation within 15 min and 30 min, respectively. The rate constant (k') for the photooxidation of RhB (0.6615 min–1) is about 11.7 and 11.4 folds than g-C3N4-SAF and BiOBr-NFs, respectively. Meanwhile, the k' for the photoreduction of Cr(VI) (0.6243 min–1) is around 30.1 and 15.8 folds than g-C3N4-SAF and BiOBr-NFs, respectively. This enhanced photocatalytic activity is ascribed to the strongly associated BiOBr-NFs/g-C3N4-SAF Z-scheme heterojunction interface, assuring effective photogenerated charge transport and high redox band-edge potentials and reduced recombination rates.