Effect of vegetable waste extract on microstructure, morphology, and photocatalytic efficiency of ZnO–CuO nanocomposites

Environment friendly and cost-effective structure-directing agents (SDAs) are highly desirable for the development of purposely designed functional nanomaterials. To comply, we aimed to explore vegetable waste extracts as potential SDAs for the synthesis of ZnO–CuO nanocomposites. Extracts of wastes of three different vegetables (cauliflowers, potatoes, and peas) were used, and their impact upon crystal structure, morphology, optical-band-gap (E_g), and photocatalytic efficiency of ZnO–CuO was explored. XRD and SEM revealed that the crystallite size and morphology varied with the vegetable waste extract. Similarly, the wide E_g of n-type ZnO narrowed upon coupling with p-type CuO, and also varied significantly with the vegetable waste extract. The resulting ZnO–CuO nanocomposites were used as photocatalysts for the degradation of model environmental pollutant (an organic dye) under visible light, and it was found that 95.6%, 93%, and 91.3% of the dye decomposes in 120 min under ZnO–CuO photocatalysts synthesized using cauliflower, peas, and potatoes waste extracts, respectively.