Photocatalytic activity of ZnO-Ag nanocomposites prepared by a one-step process using flame pyrolysis

The degradation of organic pollutants using photocatalysis is more effective than conventional methods, with ZnO being the most widely used of the various semiconductor materials for application in photocatalysis. Unfortunately, degradation efficiency is inhibited by the electron-hole recombination. The photocatalytic activity of ZnO can be enhanced by adding noble metals, such as Ag nanoparticles. However, the fabrication of ZnO-Ag using liquid-phase processes is complicated and often requires multiple steps. In this study, the effects of Ag content, ranging from 0 to 20 wt%, in the photocatalytic activity of ZnO-Ag nanocomposites are investigated. The nanocomposites were fabricated by a one-step process using flame pyrolysis and with zinc acetate and AgNO₃ as the precursors. The nanocomposites were collected using an electrostatic precipitator and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and nitrogen adsorption-desorption of the Brunauer-Emmett-Teller (BET) specific surface area. The XRD results confirm the existence of Ag nanoparticles in the prepared nanocomposites, whose crystallite size was not significantly influenced by the presence of the nanoparticles. The SEM indicated that the morphology of the nanocomposites produced was spherical, with some aggregates. Particle size distribution of the nanocomposites increased with higher Ag content. The photocatalytic activity of the produced nanocomposites, estimated by evaluating the degradation of the methylene blue aqueous solution under UV irradiation, showed that the highest photocatalytic performance was attained when the concentration of Ag was equal to 5 wt%.