Promoting effect of cellulose-based carbon dots at different concentrations on multifunctional photocatalytic degradation of dyes by ZnO

In this work, a novel cellulose based fluorescent carbon dots (CDs) doped ZnO composite, ZnO/CDs-x (x = 10, 20, 30, 40), was developed as a photocatalyst for the photocatalytic degradation of four dyes. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV visible diffuse reflectance spectroscopy (UV–Vis DRS), and transient photocurrent measurements were carried out to study the effects of different concentrations of CDs on the morphology and photocatalytic properties of ZnO/CDs−x (x = 10, 20, 30, 40) composites. When the concentration of CDs increased, the structure of ZnO/CDs−x (x = 10, 20, 30, 40) changed from a peony like structure (x = 10, 20) to a hexagonal prism like structure (x = 30, 40) and assembled into a flower like structure. Flower like ZnO/CDs-20 showed the best photocatalytic performance and good durability under UV light , and three types of excitation effects were observed: mixed light > sunlight >  visible light . It was found that the addition of CDs with a concentration of 20 mL in ZnO can significantly enhance the photoabsorption and the separation of photogenerated carriers, which is beneficial to improve the photocatalytic performance.