Surfactant-Assisted Synthesis of NiO-ZnO and NiO-CuO Nanocomposites for Enhanced Photocatalytic Degradation of Methylene Blue Under UV Light Irradiation
Hulugirgesh Degefu Weldekirstos, Birtukan Habtewold, Daniel Manaye Kabtamu
Abstract
The photocatalytic process over semiconducting oxide surfaces has attracted worldwide attention as a potentially efficient, environmentally friendly, and low-cost method for wastewater treatment. This study presents a straightforward, inexpensive, and rapid route for the synthesis of nickel oxide (NiO) and its composites with zinc oxide (NiO/ZnO) and copper oxide (NiO/CuO) nanoparticles through the chemical precipitation method using capping agent-hexadecyltrimethylammonium bromide (CTAB) for photocatalytic degradation of the methylene blue dye. The structure, morphology, and elemental constituents were characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The energy band gap of pure NiO, NiO-ZnO, and NiO-CuO composites was evaluated using the Tauc plot from absorption spectra and resulted as 3.00, 2.90, and 3.25 eV, respectively. The optimum parameters for all photocatalysts were the following: pH 8, irradiation time 175 min, catalyst amount 75 mg, and dye concentration 7 mg/L. At these optimum parameters, the degradation efficiency of the prepared photocatalysts toward the MB dye achieved was 89.8% for NiO, 97% for NiO/ZnO, and 94.2% for NiO/CuO. The highest activity of the p-type/n-type (NiO/ZnO) nanocomposite for MB degradation is possibly due to electron–hole pair recombination inhibition by charge transfer processes. Therefore, semiconducting composite-based nanocatalysts such as NiO/ZnO with high photocatalytic activity are promising for future industrial applications to remove undesirable organic pollutants from the environment.