Photocatalytic degradation of Reactive Black dye using ZnO–CeO2 nanocomposites

This study presents the photocatalytic efficiency of ZnO-CeO2 nanocomposites for the degradation of a model Reactive Black (RB) dye. Nano-CeO2 was synthesized using cerium nitrate precursor solution via chemical precipitation. Synthesized nano-CeO2 was mixed with ZnO nanoparticles in different mass ratios to obtain ZnO-CeO2 heterojunction photocatalyst. The morphology of the nanocomposites was examined using transmission electron microscope (TEM). X-ray diffraction patterns of the CeO2 corresponded well with (1 1 1) plane of cubic-phase CeO2. The band gap of the ZnO-CeO2 nanocatalyst synthesized was determined to be 3.08 eV, which was lower than that of the pristine CeO2 and ZnO powders, respectively. The results indicate that 1:1 wt. ratio ZnO-CeO2 nanocomposite provides about 85% RB degradation within 90 min under UV light under alkaline pH conditions. Degradation rate of RB dye achieved with ZnO-CeO2 nanocomposite was almost 1.5 times greater than that obtained with pristine ZnO. Increasing CeO2 ratio beyond 1:1 wt. ratio did not significantly increase RB degradation. The results demonstrate that addition of CeO2 to ZnO results in lowering its band gap energy and aids charge carrier separation resulting in enhanced oxidation of RB dye under UV light.