Design of Cu2O:ZnO heterojunction nanocomposites with enhanced charge separation and broad-spectrum photocatalytic activity

Cu 2 O:ZnO nanocomposites with varying Cu:Zn molar ratios (1:0 to 1:10) were synthesized via a low-temperature co-precipitation method and comprehensively characterized to establish structure - property – function relationships. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and field-emission scanning electron microscopy (FESEM) confirmed the coexistence of cubic Cu 2 O and hexagonal ZnO phases, with strong interfacial coupling leading to crystallite sizes of ∼25–35 nm and nanoparticle morphologies of 50–80 nm. Optical absorption analysis revealed bandgap tunability, where ZnO narrowed from 3.4 to ∼3.3 eV under interfacial strain, while Cu 2 O retained its ∼2.44 eV bandgap. Vibrating sample magnetometry (VSM) indicated weak ferromagnetism, attributed to defect-induced spin polarization and interface effects. Photocatalytic studies demonstrated exceptional performance, with the optimal Cu:Zn ratio (1:8) achieving 99 % degradation of RhB within 30 min, representing a 4.3-fold enhancement over pristine Cu 2 O, along with efficient removal of phenol and ciprofloxacin and excellent recyclability. The superior activity is ascribed to the formation of a type-II heterojunction that promotes charge separation, suppresses recombination, and enhances reactive oxygen species generation. These findings highlight the potential of Cu 2 O:ZnO nanocomposites as efficient and durable photocatalysts for environmental remediation, while offering new insights into interfacial strain and defect engineering for next generation heterostructures. • Cu 2 O/ZnO nanocomposites were successfully synthesized via a low-temperature co-precipitation method. • XRD, FTIR, and FESEM confirmed the coexistence of cubic Cu 2 O and hexagonal ZnO phases. • Interfacial strain narrowed the ZnO bandgap from 3.40 to ∼3.30 eV, while Cu 2 O retained its ∼2.44 eV bandgap. • The optimal Cu:Zn molar ratio of 1:8 achieved 99 % degradation of RhB within 30 min. • The optimized Cu 2 O/ZnO nanocomposite exhibited excellent recyclability.