Excellent photocatalytic performance and dual-band degradation of organic pollutants through Z-scheme photocatalysts

Abstract

Organic pollutants, particularly nitrogen-rich explosives and carbon-rich dyes are generally degraded by different photocatalysts under either visible or ultraviolet light, leading to substantial waste and cost. Three photocatalysts with Z-scheme structures, Ag@AgBr/Cu2O-1, Ag@AgBr/Cu2O-2, and Ag@AgBr/Cu2O-3, are designed and synthesized employing a simple solvothermal and photoreduction technique to develop advanced photocatalyst materials that can degrade nitro substances under ultraviolet (UV) irradiation and organic dyes under visible-light irradiation. The structural characterization of Ag@AgBr/Cu2O-2 as determined through various spectroscopic techniques (e.g. XPS, XRD and TEM) reveal that the Z-scheme photocatalysts are composed of Ag, Cu2O and AgBr nanospheres with particle size less than 100 ​nm, while nano-Ag and nano-AgBr coupled to the surface of the Cu2O microspheres. Further investigations demonstrate that these photocatalysts exhibit a good UV–visible absorption range (200–800 ​nm) and outstanding photocatalytic degradation activity for two typical organic pollutants. Among them, Ag@AgBr/Cu2O-2 achieve a 100% degradation of trinitrotoluene (a common explosive) in 30 ​min under UV radiation, and a 99.2% degradation of rhodamine B (a typical dye) in 60 ​min under visible-light irradiation in the absence of UV light, demonstrating remarkable dual-band adaptability. Moreover, Ag@AgBr/Cu2O-2 displays superior stability, with a degradation rate of up to 85% after four cycles. The putative photocatalytic reaction mechanism is proposed based on the radical trapping experiment.