Carbon dots and Ag nanoparticles decorated g-C3N4 nanosheets for enhanced organic pollutants degradation under sunlight irradiation

In this work, novel ternary composites were prepared by depositing both carbon dots (CDs) and Ag nanoparticles (AgNPs) onto the surface of g-C3N4 nanosheets (CNNs). The as-prepared samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) techniques. The characterization results demonstrated that the CDs and AgNPs were well distributed on the surface of CNNs. The photocatalytic activities of all the samples were evaluated by degrading methyl orange (MO) and p-nitrophenol (PNP) in aqueous media under sunlight irradiation. Among the prepared samples, CNNs decorated with 2 wt% CDs and 1 wt% AgNPs showed higher degradation performance. The enhanced performance was attributed to the improved light harvesting capability and effective charge carrier separation at the AgNPs/CDs/CNNs interface. Superoxide radical species and photogenerated holes were found to be predominant reactive species responsible for the photodegradation of these pollutants. A suitable mechanism was proposed and discussed in detail. (C) 2017 Elsevier B.V. All rights reserved.