Plasmonic resonance excited dual Z-scheme BiVO4/Ag/Cu2O nanocomposite: synthesis and mechanism for enhanced photocatalytic performance in recalcitrant antibiotic degradation

Abstract

The utilization of solar energy based on semiconductor photocatalysts for pollutant removal and environmental remediation has become a research hot spot and attracted great attention. In this study, a novel ternary BiVO₄/Ag/Cu₂O nanocomposite has been successfully synthesized via simple wet impregnation of Cu₂O particles coupled with a subsequent photo-reduction pathway for the deposition of metallic Ag on the surface of BiVO₄. The resulting BiVO₄/Ag/Cu₂O photocatalyst was used for the degradation of tetracycline (TC) under visible light irradiation (λ > 420 nm). Results showed that the coating contents of the Cu₂O and Ag particles presented a great effect on the eventual photocatalytic activity of the photocatalysts, and the optimum coating contents of Cu₂O and Ag were obtained with their mass ratios of 3% and 2%, respectively. Under optimum conditions, nearly 91.22% TC removal efficiency was obtained based on ternary BiVO₄/Ag/Cu₂O nanocomposites, higher than that of pure BiVO₄ (42.9%) and binary BiVO₄/Cu₂O (65.17%) and BiVO₄/Ag (72.63%) nanocomposites. Meanwhile, the enhanced total organic carbon (TOC) removal efficiency also indicated the excellent photocatalytic degradation ability of the BiVO₄/Ag/Cu₂O nanocomposites. As for their practical application, the effects of initial TC concentration, various supporting electrolytes and different irradiation conditions were investigated in detail. Three-dimensional excitation–emission matrix fluorescence spectroscopy (3D EEMs) was used to show the by-products of TC molecule degradation. Cycling experiments indicated the high stability of the as-prepared photocatalysts. Furthermore, the results obtained from radical trapping experiments and ESR measurements suggested that the photocatalytic degradation of TC in the BiVO₄/Ag/Cu₂O based photocatalytic system was the joint action of the photogenerated holes (h⁺), superoxide radical (˙O₂⁻) and hydroxyl radical (˙OH). The enhanced photocatalytic activity of BiVO₄/Ag/Cu₂O was attributed to the synergistic effect of Cu₂O, Ag and BiVO₄, especially the surface plasmon resonance effect and the established local electric field brought about by metallic Ag. Additionally, to deeply understand the reaction mechanism, a dual Z-scheme charge transfer pathway has been proposed.