Solar light driven Zn@CuO/MoO3 heterojunction photocatalyst for photodegradation of methylene blue dye: Enhanced stability, charge separation, and environmental remediation

A novel Zn@CuO/MoO₃ binary heterojunction photocatalyst was synthesized via a wet chemical route and investigated for the degradation of methylene blue (MB) under visible light. XRD confirmed a monoclinic structure with ⁓20 nm crystallite size, while FTIR, Raman, TGA-DSC, and XPS analyses verified strong interfacial interaction, stability, and the presence of key oxidation states. SEM-EDX and elemental mapping revealed a uniform distribution of nanoparticles with the expected composition. UV–visible and PL showed enhanced optical absorption and reduced charge recombination. The Mott-Schottky curve of Zn@CuO/MoO₃ showed a positive slope, indicating n-type semiconductor behavior. Under optimal conditions, Zn@CuO/MoO₃ achieved 100 % photodegradation of MB in 30 min, demonstrating superior performance compared to pristine CuO, MoO₃, and Zn@CuO, which maintained 97 % efficiency after four cycles. Radical trapping tests revealed that hydroxyl [·OH] and superoxide [·O₂⁻] radicals played dominant roles in the degradation process, and the degradation followed pseudo-second-order kinetics with a rate constant of 0.10 g mg⁻¹ min⁻¹ (R² = 0.999). GC–MS and ECOSAR confirmed the reduced toxicity of byproducts. The superior performance of Zn@CuO/MoO₃ is attributed to enhanced UV–visible absorption, efficient charge separation, and reduced electron-hole recombination, highlighting its potential as a cost-effective, reusable, and efficient p-n heterojunction photocatalyst for environmental applications.