The enhanced photocatalytic activity of ZnO nanorods/CuO nanourchins composite prepared by chemical bath precipitation

Abstract

In this work, ZnO nanorods (NRs)/CuO nanourchins (NUs) were composed together to achieve the highest efficiency in methylene blue (MB) degradation. The nanocomposites were fabricated via a one-step, facile, and solution-based method named chemical bath precipitation. Crystal structures of hexagonal ZnO NRs and monoclinic CuO NUs phases were detected by X-ray diffraction (XRD) analysis, while field emission scanning electron microscopy (FESEM) confirmed the formation of ZnO NRs and CuO NUs with favorable interconnectivity. The chemical bonding stage of the Cu2+, Zn2+, and O2− were investigated with high-resolution X-ray photoelectron spectroscopy (HRXPS). Brunauer-Emmett-Teller (BET) method depicted a relatively wide pore size distribution for all the samples. Diffuse reflectance spectroscopy (DRS) demonstrated that band gap energy of ZnO NRs further narrowed by raising CuO concentration owing to the formation of the Cu(3d) energy state near the Zn(3d) valance band. Photoluminescence (PL) spectra revealed that the combination of ZnO NRs with CuO NUs significantly increased the lifetime of the photo-excited charge carriers. The ZnO/(10 mol%)CuO nanocomposite with the band gap energy of 2.9 eV and pore volume of 0.0180 cm3/g exhibited the highest efficiency and complete degradation of MB in less than 240 min. The photo-degradation kinetics of the as-prepared nanocatalyst followed a pseudo-first-order reaction model and exhibited about 12 times faster than ZnO. Finally, the photo-degradation mechanisms are proposed based on the role of reactive oxygen species and photo-generated charge carriers.