Ecofriendly synthesis of CuO–ZnO nanocomposite using Limonia Acidissima extract for photocatalytic degradation of methylene blue and rhodamine B
摘要
In this study, CuO–ZnO nanocomposites were synthesized using wood apple shell extract as a green, non-toxic reducing and stabilizing agent. The nanocomposites were comprehensively characterized using XRD, FT-IR, UV-DRS, PL, SEM, and EDAX to investigate their structural, optical, and morphological properties. UV-DRS analysis revealed a bandgap energy reduction to 2.86 eV, favoring enhanced visible-light absorption. The photocatalytic performance of the CuO–ZnO nanocomposite was evaluated for the degradation of methylene blue (MB) and rhodamine B (RhB) under sunlight irradiation. The catalyst exhibited exceptional degradation efficiencies, achieving 98.11 ± 1.91% MB removal and 98.57 ± 1.87% RhB removal within 180 min, with corresponding rate constants of 11.3 ± 0.8 × 10−3 min−1 and 14.5 ± 1.5 × 10−3 min−1,. This significantly outperformed pristine CuO and ZnO nanoparticles, which showed MB degradation of 56.82 ± 2.14% and 69.20 ± 1.86% and RhB degradation of 58.34 ± 2.27% and 69.04 ± 1.98% under identical conditions. The enhanced activity is attributed to the formation of a p-n heterojunction, which improved charge separation efficiency, minimized electron–hole recombination, and broadened the light absorption range. Furthermore, the catalyst demonstrated excellent stability and reusability, retaining 80% of its initial efficiency even after five consecutive cycles. Radical scavenging experiments confirmed that superoxide radicals (•O₂⁻) played the dominant role in the degradation process, while hydroxyl radicals (•OH) also contributed significantly.