Photocatalytic properties of ZnO/CuO nanocomposite prepared in acidic media

In this work, the ZnO/CuO nanocomposite was synthesized with two different initial pH values in an acidic media through a simple one-step and cost-efficient chemical bath precipitation method. To alter the pH value of the solution, nitric acid was added dropwise and initial pH values were 1.5 and 4.5, respectively. The crystal phase structure of the samples was investigated by X-ray diffraction analysis (XRD), indicating the formation of wurtzite structure of ZnO and monoclinic structure of CuO. Additionally, the morphological structure of the as-formed nanocomposites was studied by field emission scanning electron microscopy (FESEM). It was demonstrated that at pH = 4.5 and 1.5, ZnO nanorods/CuO nanoflakes and ZnO nanoparticles/CuO nanosheets were formed, respectively. For optical characterizations, diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectra were performed. The band gap energy of the as-prepared samples was calculated at 3.08 and 2.9 eV with an initial pH of 1.5 and 4.5, respectively. Furthermore, PL data revealed that the sample synthesized in pH = 4.5 exhibits a significant decrease in electron/hole recombination rate compared with that of the sample fabricated in pH = 1.5. Accordingly, the photocatalytic activity of the as-prepared samples was studied employing methylene blue (MB) under visible-light irradiation. Overall, the prepared sample at pH = 4.5 and pH = 1.5 demonstrated ~76% and ~66% photo-degradation efficiency of MB after 150 min, respectively. Finally, the role of holes and hydroxyl radicals on the degradation of MB were proposed using charge carrier scavengers.