Highly operative near full spectrum Cu doped NiO/ZnO photocatalyst: Photodegradation of phenol and organic dyes

In this study, new and near full spectrum photocatalyst composed of Cu doped NiO/ZnO composite with higher photodegradation activity (95-99%) for phenol, malachite green (MG) and reactive yellow 145 (RY145) was realized. The simple and low cost coprecipitation method was used to synthesis the pure ZnO, NiO, NiO/ZnO and 5 wt% Cu doped NiO/ZnO catalysts. The crystal structure analysis of all samples confirmed the formation of hexagonal ZnO and cubic NiO phases and ruled out the reaction between constituents. The transmission electron microscope images of the powders demonstrates the synthesis of nanostructures particles with mean size of 41-46 nm and nearly have spherical shape with some nano-sheets, especially for Cu doped NiO/ZnO sample. Optically, Cu doped NiO/ZnO nanocomposite exhibits two main band gap energies of 3.4 eV (NiO) and 2.88 eV (ZnO) with high and extended absorption tail until 1 eV, indicating the wide absorption capacity for most sunlight spectrum. The experiments of the photodegradation under natural sunlight prove that Cu doped NiO/ ZnO nanocomposite has superior removal activity towards 30 ppm MG, 30 ppm RY145 and 15 ppm phenol with efficiency of 97% (60 min), 99% (70 min) and 95% (120 min), respectively. The radicals capture tests using different scavengers verify the main role of the superoxide (O2 ˉ) species in the photodegradation process, followed by hydroxyl (OH) radicals. The reusability of Cu doped NiO/ZnO nanocomposite for four runs shows excellent photocatalytic activity (>90%) for MG and RY145 and phenol pollutants, reflecting the high stability for practical uses. The superior photoactivity characteristics of Cu doped NiO/ZnO photocatalyst were attributed to the integration between p-n heterojunction and Cu doping which reinforce the wide-ranging absorption and the separation of the electron-hole pairs.