A comprehensive study on the enhanced photocatalytic activity of CuO-NiO nanoparticles: Designing the experiments

Effects of coupling, calcination temperature and mole ratio were studied on the photocatalytic activity of CuO and NiO nanoparticles. Both semiconductors' nanoparticles were synthesized by sol-gel method. The coupled CuO-NiO system showed better photocatalytic activity than the mono-component NiO and CuO semiconductors. Hence, the coupled system with the best activity was characterized by the field emission scanning electron microscope (FESEM), EDX, X-ray Mapping, XRD, DRS, FT-IR and electrochemical impedance spectroscopy (EIS) techniques. The higher photocatalytic activity of the coupled system relates to its higher charge transfer ability that prevents from the electron/hole recombination. The NiO-CuO catalyst with mole ratio of 1:1 that calcined at 800 degrees C for 4 h, showed the best photocatalytic activity. The degradation of methylene blue (MB) was followed by UV-vis spectroscopy and the degradation extent was confirmed by chemical oxygen demand (COD) method. To investigate the interaction effects of the experimental variables on the photocatalytic activity of the coupled system, experimental design was applied based on the response surface methodology (RSM) approach. Among the interaction terms, effect of pH- time had the most importance (40%) on the created response. The best MB photodegradation result was obtained in a run included pH 3.5, catalyst dosage of 0.9 g L-1, 3.2 mg L-1 of MB during 26 min. (C) 2018 Elsevier B.V. All rights reserved.