Excellent performance of BiOI/AgEuW2O8 S-Scheme heterojunction for photocatalytic degradation of contaminants under visible light: Experimental and computational studies

Abstract

A series of xBiOI/AgEuW2O8 (BIAEW-x, x = 1, 2, 3) photocatalysts were prepared by hydrothermal method, further applied for photocatalytic degradation of organic contaminants under the visible light irradiation. The microstructure and photocatalytic properties of the as-synthesized samples were determined by various techniques such as XRD, SEM, TG-DTG, XPS, UV–Vis, ESR, and N2-adsorption. Heterojunction was formed within transition area between BiOI and AgEuW2O8, and the special structure was further validated by the results of XRD and XPS. It was found the composite with 2:1 ratio of BiOI/AgEuW2O8 possessed the highest activity of 99.48 % rhodamine B (RhB) photodegradation which was observed under the optimized conditions (3 h, pH = 5, 60 mg, 30 mg/L). This may be due to the maximum existence of BiOI/AgEuW2O8 heterojunction within the solid, which promotes the generation of the active species during the photocatalytic process. Besides, the newly-formed O–Ag bonds bridging the interface between BiOI (1 0 2) and AgEuW2O8 (0 0 4) were also confirmed according to the DFT calculations, and the electrons and holes increased largely for the interface structure. Moreover, the photodegradation process of RhB promoted by xBiOI/AgEuW2O8 follows first-order kinetic law. Furthermore, the trapping experiments were respectively conducted via addition of different trapping reagents, of which the holes were confirmed as the key active species on photodegradation of RhB over BIAEW-2 under visible light irradiation.