Carbon quantum dots/KNbO3 hybrid composites with enhanced visible-light driven photocatalytic activity toward dye waste-water degradation and hydrogen production

Abstract

In this work, a new visible-light driven photocatalyst, carbon quantum dots (CQDs)/KNbO3 composite, is successfully prepared via hydrothermal and mixed-calcination methods Multiple techniques, such as X-ray diffraction (XRD) spectroscopy, scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray (EDX) spectroscopy, fourier-transform infrared (FT-IR) spectroscopy, UV–vis diffuse reflectance spectroscopy and photoluminescence (PL) spectroscopy, are applied to investigate the morphologies, structures and optical properties of the prepared CQDs/KNbO3 composites. The photocatalytic activity of CQDs/KNbO3 composites is evaluated via degradation of crystal violet dye as target organic pollutant with simultaneous hydrogen production under visible-light irradiation. The results show that the CQDs/KNbO3 composites exhibit much higher photocatalytic activity than the KNbO3. It is ascribed to the presence of the CQDs as co-catalyst on the surface of KNbO3 particles, forming much more active sites for trapping electrons and promoting the separation of photo-generated electron-hole pairs. In addition, the CQDs can absorb visible-lights and emit the ultraviolet-lights to activate the wide band-gap KNbO3. The study of reusability shows that the CQDs/KNbO3 can be effectively recycled for four repetitive cycles and maintain a higher level of photocatalytic activity. In conclusion, the present work designs an effectively visible-light driven photocatalyst, which can be applied in photocatalytic degradation of organic pollutants with simultaneous hydrogen evolution.