Degradation of rhodamine B during visible light photocatalysis employing Ag@AgCl embedded on reduced graphene oxide

Visible light photocatalysis is an evolving technology for pollutant remediation. Plasmonic absorbers mounted upon semiconducting substrates have been shown to be highly efficient photocatalysts. In this work the ability of a silver nanoparticle – semiconducting silver chloride – reduced graphene oxide assemblage (Ag@AgCl/rGO) to degrade rhodamine B dye (RhB) has been examined, with particular emphasis upon establishing the nature of the degradation mechanism. During the dye degradation process, a range of intermediate chromophoric compounds are formed, which were quantified by a deconvolution of the UV–vis absorption spectrum, allowing insight into the kinetics of degradation of these intermediate chromophores. The concentration profiles of these products suggest that two discrete pathways of dye degradation are operative, which we propose occur as a result of an intrinsic oxidant generation capacity of the Ag@AgCl/rGO material as well as due to direct excitation of dye molecules adsorbed upon the Ag@AgCl/rGO material. Through competition experiments with tert-butanol it is shown that the oxidant generated in this system cannot be freely-diffusing hydroxyl radical.