Enhanced Photocatalytic Properties of Zinc-Doped CuO Decorated with Silver Obtained by Microwave-Assisted Hydrothermal Method: Statistical Factorial Design

Zinc-doped CuO powders were obtained by microwave-assisted hydrothermal processing at 140°C for 30 min then decorated with silver by photodeposition and characterized by x-ray diffraction (XRD) analysis, field-scanning electron microscopy (SEM), and ultraviolet–visible (UV–Vis) spectroscopy region for E gap estimation. The photocatalytic activity of the powders was measured using methylene blue dye. To provide further information on the influence of the process variables on the photocatalytic activity, a 2 3 factorial design was carried out with three central points, using the amounts of zinc and silver and the stirring time under UV radiation as variables. The XRD patterns indicated ZnO precipitation when 8% Zn was added. SEM micrographs showed that the CuO had predominantly nanoplate morphology, with loss of the regular aspect of the ends and increased thickness on addition of zinc atoms. The photocatalytic activity results showed that addition of zinc and silver increased the photocatalytic activity of pure CuO. According to the factorial design, the stirring time of the CuO powder in contact with AgNO 3 solution was the most significant variable affecting the photocatalytic properties, with longer time being detrimental due to an increase in the size of the silver nanoparticles.