Preparation and photocatalytic performance of carbon dots/g-C3N4 composite catalyst

The light absorption and photo-induced carrier recombination of g-C3N4 are the key problems that limit its efficient photocatalytic applications. Herein, carbon dots (CDs) were synthesized using coal pitch as precursor and then the CDs/g-C3N4 composite catalyst was prepared by ultrasonic-assisted method. The structure, optical and photoelectrochemical properties of the catalyst were characterized by TEM, XRD, UV-Vis diffuse reflection spectrum, PL spectrum, EIS test and photocurrent response test. The results show that the regulation of band structure and the formation of interface after the introduction of CDs expand the range of light absorption of the composite photocatalyst, promote the effective separation and migration of photogenerated electrons and holes, and thus facilitate the photocatalytic reaction. Using rhodamine B (RhB) as the model, the photocatalytic activity of CDs/gC3N4 composite catalyst is significantly higher than that of pure g-C3N4 under visible light irradiation. The degradation rate of RhB can reach 98.6% within 40 min, and the degradation rate constant of CDs/g-C3N4 is 6.8 times that of g-C3N4. The capture of experiment of active species reveals that •O2− plays a major role in the degradation system. In addition, CDs/g-C3N4 composite catalyst exhibit good stability. After 5 cycles, the degradation rate of RhB is still up to 97.5%, which shows a good application prospect in visible light photocatalysis. © 2023 Beijing University of Aeronautics and Astronautics (BUAA). All rights reserved.