Fabrication of Cu/Cu2O nanoparticles by banana peel extract for 4-nitrophenol degradation

• Cu/Cu 2 O nanocomposites were synthesized using banana peel extract • Green synthesized Cu/Cu 2 O effectively reduces 4-nitrophenol in water • Cellulose nanofibers from PBE guide self-assembly of Cu/Cu 2 O nanostructures. • Atomic vacancies in Cu/Cu 2 O enhance structural features and catalytic activity • The eco-friendly nanocomposites offer a scalable solution for pollutant remediation Developing sustainable nanomaterials with high catalytic activity is crucial for advancing green chemistry and environmental remediation. In this study, Cu/Cu 2 O nanocomposites were synthesized using banana peel extract (BPE) as a natural reducing and stabilizing agent for copper Cu 2+ ions. Rietveld refinement of X-ray diffraction patterns revealed that increasing BPE content reduces the Cu 2 O crystallite size from 23 to 13 nm, while simultaneously increasing both the Cu/Cu 2 O ratio and the Cu particle size. The specific surface area of the composite decreased from 54.62 to 9.12 m 2 g -1 as the BPE content in the reaction mixture increased. Additionally, BPE-derived cellulose nanofibers served as a platform for the solvothermal growth of Cu 2 O nanoparticles, leading to the self-assembly of Cu/Cu 2 O/nanofiber structures, as observed by SEM and TEM. High-resolution TEM revealed that low BPE content creates atomic lattice defects in Cu 2 O, giving rise to additional Raman features. The as-prepared Cu/Cu 2 O nanocomposites demonstrated excellent catalytic activity for 4-nitrophenol reduction in the presence of NaBH 4 , with an apparent rate constant (kₐₚₚ) of 0.0122 s⁻¹ and an activity factor (K) of 12.20 s⁻¹ g⁻¹ for the optimized sample. XPS analysis further confirmed the chemical states of the catalysts before and after catalytic reduction. The results indicate that BPE not only enables sustainable synthesis but also tailors the structure and catalytic performance of Cu/Cu 2 O nanocomposites for effective wastewater treatment. Graphical Abstract