Room-temperature synthesis of rGO/Ag nanocomposite as a photocatalyst for the degradation of organic pollutants in wastewater

We prepared a composite of reduced graphene oxide (rGO) and silver (Ag) nanoparticles (NPs) by using chemically exfoliated graphene as the base matrix, and adding biosynthesized Ag NPs. Transmission electron microscopy images show that rGO has a 2D delaminated layered structure with a sheet-like morphology, with a moderate concentration of isometric Ag NPs well dispersed over the basal planes of the rGO nanosheets. Ag NPs have a bimodal size distribution, with both larger (10–50 nm) and smaller (1–5 nm) particles evenly dispersed on the rGO. UV–visible absorption spectroscopy of the rGO/Ag composite reveals a hump around 265 nm, corresponding to π-π* electron resonance transitions owing to aromatic sp2-hybridized C–C bonds in graphene sheets, and a peak at 401 nm, attributed to Ag NPs. The photocatalytic potential of rGO/Ag nanocomposites was studied using organic compounds (methylene blue (MB), 4-nitrophenol, and coumarin) as models of water pollutants. The experiments show that for methylene blue the degradation efficacy of the rGO/Ag nanocomposite catalyst after 2 h is about 97 % and 90 % using UV and visible light irradiation, respectively. The rGO/Ag nanocomposite showed lower percentages of degradation toward 4-nitrophenol and coumarin due to their significantly higher concentrations, but the absolute rates of their decomposition were as high as those for MB. This study suggests that the nanocomposite synthesized at room temperature can be used as an efficient adaptable photocatalyst for the photodegradation of organic contaminants in industrial wastewater.