Enhanced photocatalytic degradation of methyl orange using CuO nanowires grown on copper substrates with TiO₂/H₂O₂ synergism

This study presents a materials and reaction-engineering strategy for treating dye-laden wastewater using immobilized cupric oxide (CuO) nanowires (NWs) on a copper substrate formed by thermal oxidation. High-density CuO NWs were grown directly on the substrate with an underlying cuprous oxide (Cu₂O) layer over an oxidation temperature range of 400–600 °C, with oxidation at 500 °C for 120 min yielding the most uniform morphology. This binder-free, substrate-supported architecture securely anchors the CuO/Cu 2 O photocatalyst, preventing loss into treated water, enabling direct reuse, and eliminating the need for post-treatment filtration. Even though the CuO/Cu₂O p–p heterojunction promotes charge separation and more reactive oxygen species (ROS) generation, only ~ 32% of 5 ppm methyl orange (MO) photodegradation was achieved after 5 h under UVC LED irradiation, indicating limited efficiency. Incorporation of low-dose hydrogen peroxide (0.5 mL H₂O₂) activated a Fenton-like pathway, accelerating ROS formation via Cu²⁺/Cu⁺ redox cycling and ~ 100% degradation of 20 ppm MO was achieved after 60 min irradiation. Further integration of titanium dioxide (TiO₂) to form a TiO₂/CuO/Cu₂O ternary heterostructure expanded light absorption and improved interfacial charge separation. In combination with H₂O₂, this system achieved complete MO degradation within 40 min under UVC LED irradiation and 100 min under visible light.