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.