Novel hierarchical BiOBr-based photocatalyst co-modified with Ag nanoparticles and porous g-C3N4 nanosheets for efficient removal of tetracycline and Cr(VI)

Preparation of advanced semiconductor materials with an environmentally friendly method to be used as visible-light-active photocatalysts has always been preferred. An environmentally convenient approach was employed to synthesize a novel ternary Ag/g-C3N4/BiOBr heterostructure, which showed significantly improved removal performance towards tetracycline (TC) and Cr(VI) ions. The removal efficiencies of Ag/g-C3N4/BiOBr heterostructure towards TC and Cr(VI) were 95% and 80% under visible-light irradiation after 100 min, which were 1.69- and 2.85-folds higher than that of BiOBr, respectively. Due to the synergistic effect between the g-C3N4/BiOBr heterojunction and Ag nanoparticles (SPR), the visible light absorption of the photocatalysts was enhanced, and the separation and transfer of photo-induced electrons and holes were accelerated. The superior light harvesting capability, electron transfer, and the underlying mechanism were investigated by UV-Vis spectroscopy, photoluminescence spectroscopy, transient photocurrent and Nernst impedance measurements. The trapping and electron paramagnetic resonance measurement results revealed that holes were the main species in the degradation of TC, but both hydroxyl and superoxide radicals took part as well in the process. The present work offers an environmentally friendly approach to construct ternary heterostructure photocatalysts for environmental remediation.

Automated summary

This study presented a novel ternary Ag/g-C3N4/BiOBr heterostructure photocatalyst synthesized using an environmentally friendly method, which exhibited significantly improved removal efficiency towards tetracycline and hexavalent chromium ions. The synergistic effect between the heterojunction structure and silver nanoparticles enhanced light absorption, accelerating the separation and transfer of photo-induced electrons and holes. Through various spectroscopic and measurement techniques, it was revealed that holes were the main species involved in tetracycline degradation, with hydroxyl and superoxide radicals also playing a role in the process. This research provides an environmentally friendly approach to developing ternary heterostructure photocatalysts for environmental remediation.