Comparative Study of Hydrothermal and Sonochemical Preparation of Cu and Ag Codoped ZnO/Graphene Nanocomposites for Enhanced Catalytic and Inactivation of Pathogens

Developing high-performing photocatalysts and composites generate synergetic effects in modern photocatalysis. Zinc oxide (ZnO) is a promising photocatalyst; however, its wide bandgap and high charge carrier recombination rate significantly limit its visible-light activity and overall photocatalytic efficiency. To overcome these challenges, this study focuses on the synthesis of Cu-Ag codoped ZnO/graphene nanocomposites using both hydrothermal and sonochemical methods, aiming to regulate the interfacial interaction and enhance charge separation. The hydrothermally synthesized (CAZ/Gr)_H composite exhibited a lower bandgap, improved carrier transfer efficiency, and stronger Zn-O-C interfacial bonding compared to the sonochemically prepared (CAZ/Gr)_S sample. Density functional theory (DFT) calculations confirmed the reduced work function and enhanced electron mobility in the hydrothermal system. Under natural sunlight, the (CAZ/Gr)_H composite demonstrated superior photocatalytic degradation of organic dyes and excellent antibacterial activity against E. coli and S. aureus. These findings highlight the effectiveness of interface-regulated, green-synthesized ZnO-based nanocomposites in addressing the fundamental limitations of traditional ZnO photocatalysts.