Surfactant-Assisted Synthesis of NiO-ZnO and NiO-CuO Nanocomposites for Enhanced Photocatalytic Degradation of Methylene Blue Under UV Light Irradiation

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.