Green Synthesis of Bi2WO6 Nanocompounds Decorated with Carbonaceous Materials for Visible-LEDs-Light-Driven Highly Efficient Degradation of Organic Pollutants

Water contamination with dyes such as rhodamine B (RhB) affects living organisms and ecosystems. Heterogeneous photo-catalysis has been successfully employed in RhB degradation. In this work, different Bi2WO6 (BWO)-carbonaceous material nanocomposites (NCs) were synthesized using simple and environmentally friendly procedures and applied as photocatalysts for the visible degradation of RhB. The decoration of BWO with nitrogen-doped graphene (NG) and NG functionalized with citric acid (FNG) enhanced the photocatalytic activity of NCs. The synthesis and performance of NG-BWO and FNG-BWO catalysts have no precedent. RhB and other dyes (methylene blue, crystal violet, and methyl orange) were used to test the activity of BWO NCs under low-power white LEDs irradiation. The 1.25FNG-BWO (1.25% FNG content) photocatalyst achieved the highest activity toward RhB degradation among the other prepared NCs, attaining 100% in 150 min with 19 W white LEDs, which is comparable to the activity reported in other studies using similar NCs and high-power (300-500 W) xenon and tungsten lamps, also representing a considerable energy saving of the process. The photoelectrochemical assays figured out that diffusion phenomena are responsible for RhB degradation rate using BWO NCs, and that the photocurrent changes are related mainly to their Eg. Photocatalytic cycles corroborated the high stability of 1.25FNG-BWO. Besides, holes (h(+)) and superoxides (O-2(center dot-) ) are the main oxidizing species of RhB, and the mechanism of charge transfer and RhB photodegradation using 1.25FNG-BWO was postulated.