Solution-based synthesis of Co3O4/ZnO p-n heterojunctions for rapid visible-light-driven oxidation of ciprofloxacin

Semiconductor photocatalysts become an ecological solution for the oxidative degradation of emergent wastewater pollutants under light irradiation. However, the enormous bandgap energy (Eg) and the fast recombination of photoinduced charges are still obstacles for the actual application. Here, we introduce a solution-based synthesis of hexagonal ZnO nanoparticles decorated with Co3O4 smaller nanocrystals at lower amounts (1.0 ~ 4.0 wt%) to produce p-n heterojunctions. These Co3O4/ZnO exhibited a mesoporous active surface texture with high surface area (144 ~ 160 m2 g−1). Also, the loading of Co3O4 dots to ZnO revealed a broader visible-light absorption and reduction of Eg to 2.53 eV compared to 3.49 eV of the pure ZnO. The produced heterojunctions were tested for ciprofloxacin's (CIP) photoelimination, as an emerging antibiotic probe waste in the water. The optimized 3.0 wt% Co3O4-loaded ZnO displayed a total elimination of 10-ppm of CIP after 30 min of visible-light exposure with sustainable recyclability. The captivated act of Co3O4/ZnO is referred to as the formation of p-n heterojunction between Co3O4 and ZnO that reduces the Eg and enhances the photocharge separation. This work signifies the use of this novel heterojunction photocatalyst in the remediation of pharmaceutical wastes.