Enhanced Photocatalytic Degradation of Methylene Blue Using Morphology‐Controlled ZnO and ZnO/Carbon Quantum Dot Nanocomposites

ABSTRACT In this study, flower‐like ZnO (FZ), wool ball‐like ZnO (WbZ), and carbon quantum dots (CQDs)/wool ball‐like ZnO (WbZC) nanocomposites were synthesized by employing the hydrothermal method. The TEM and SEM characterizations showed average particle sizes of approximately 2.8, 4.0, and 5.5 nm for FZ, WbZ, and WbZC nanocomposites, respectively. The Barrett–Joyner–Halenda (BJH) analysis showed that the average pore size of WbZC was 223.4 nm, which is higher than the average pore size of FZ and WbZ (43.2 and 61.6 nm, respectively). These results indicate a significantly enhanced porosity with the incorporation of CQDs. Improving porosity is essential for facilitating enhanced adsorption and interaction with dye molecules. The WbZC nanocomposites exhibited efficient photocatalytic degradation of methylene blue dye. Catalytic efficiency of synthesized nanoparticles for methylene blue dye degradation was evaluated. WbZC nanocomposites with a minimum energy band gap (3.09 eV) and the highest pore size and porosity showed maximum catalytic activity with 97% dye degradation in a 100 PPM catalyst dose. However, WbZ showed the same catalytic activity for dye degradation in 60 min with a 200 PPM catalyst dose. FZ showed minimum catalytic activity with 97% of dye degradation in 90 min with 200 PPM catalyst activity.