A poly-vinyl alcohol aided multiphase Z-scheme ZnO–AgI–CuO nanocomposite as an efficient photocatalyst for dye photodegradation

Abstract

Single-phase ZnO and CuO photocatalysts as well as a multiphase PVA-assisted ZnO–AgI–CuO nanocomposite were synthesized by sol–gel method. In contrast, a AgI photocatalyst was synthesized by precipitation. The calcination temperature (500 °C) was determined using the TGA-DTA technique. FTIR, XRD, DLS, DRS, BET, and SEM techniques were used to characterized the synthesized nanomaterials. The ZnO–AgI–CuO nanocomposite was also characterized using SEM-EDS, TEM, HRTEM, and SAED. The HRTEM and SAED findings reveal the intimate contact of the AgI and CuO photocatalysts on the surfaces of ZnO. The photocatalytic efficiency of CuO is higher than that of the two pristine AgI and ZnO. This is probably due to the lower band gap energy of CuO photocatalyst. Furthermore, the ZnO–AgI–CuO nanocomposite shows outstanding catalytic performance, and its activity is 2.1, 1.64, and 1.46 times higher than those of ZnO, CuO, and AgI, respectively. This catalytic enhancement could be attributed to the synergistic effect of its components. The photocatalytic performance of the ZnO–AgI–CuO nanocomposite was also explored in industrial wastewater collected from KK textile factory, Addis Ababa, Ethiopia. The findings obtained for ZnO–AgI–CuO were 95% and 82% for MB and industrial wastewater, respectively. The higher efficiency of ZnO–AgI–CuO for the MB dye than the industrial wastewater may be due to the presence of many pollutants in industrial wastewater. Reuse experiments for five cycles were examined using the ZnO–AgI–CuO nanocomposite, and nearly the same efficiency was observed. The ZnO–AgI–CuO nanocomposite was analyzed using FTIR, XRD, and DRS techniques before and after the photocatalytic experiments. The results demonstrate that the phases and structural characteristics of the ZnO–AgI–CuO nanocomposite remain largely unchanged before and after reuse. Besides, a conceivable photocatalytic Z-scheme mechanism was proposed. This could offer novel findings in the design of stable Z-scheme heterojunctions using ZnO, CuO, and AgI photocatalysts.