Lotus-Shaped CuO/ZnO Nanocomposites with Tunable Band Gap for UVA-Induced Photocatalytic Degradation of Organic Dyes.

Industrial discharge of organic pollutants poses severe risks to aquatic ecosystems and human health, underscoring the urgent need for efficient, reusable photocatalysts for their degradative removal. In this study, binary CuO/ZnO nanocomposites with varying CuO contents (5, 10, and 15 wt %, denoted as CZ-5, CZ-10, and CZ-15, respectively) were synthesized via a hydrothermal route at 100 °C for 24 h from their corresponding salt precursors. Structural and surface characterizations of the prepared composites were performed using state-of-the-art techniques, confirming the formation of highly crystalline wurtzite ZnO and monoclinic CuO phases with abundant oxygen vacancies. In addition, the CZ-10 composite exhibited a distinctive Lotus-like morphology, a reduced bandgap energy (3.13 eV), and suppressed electron-hole recombination via the S-scheme mechanism by reserving high potential electrons and holes by combining the lower potential of electrons and holes. The Point of Zero Charge (PZC) of CZ-10 was found to be 6.9. Furthermore, complete degradation of methylene blue (MB) and 96% of orange G (OG) could be achieved within 90 min under UVA irradiation using CZ-10 with rate constants of 0.06 and 0.03 min