Photocatalytic degradation of  reactive black dye using ZnO– CeO2 Nanocomposites

Abstract Nano-CeO2 was synthesized via the chemical precipitation of cerium precursor solution, and then mixed with nano-ZnO at various weight ratios to obtain ZnO-CeO2nanocomposites. The composites were characterized for their morphological and photocatalytic properties. X-ray diffraction patterns of the pristine metal oxides corresponded well with (1 0 1) and (1 1 1) peaks of hexagonal wurtzite like-ZnO and cubic-phase CeO2, respectively. The band gap of the ZnO-CeO2nanocomposite was 3.08 eV, while that of pristine CeO2 and ZnO powder was 3.24 eV and 3.12 eV respectively. Photocatalytic activity of ZnO-CeO2composite was evaluated at various Reactive Black (RB) dye and catalyst concentrations. A 1:1 wt ratio ZnO-CeO2 nanocompsite provided the maximum (~ 85%) RB oxidation under UV light within 90 minutes. Rate of dye degradation obtained with ZnO-CeO2nanocomposite was almost 1.5 times more than that obtained with bare ZnO. It was observed that increase in CeO2 to ZnO ratio increased oxidation rates up to 1:1 wt ratio. Increasing CeO2 ratio beyond 1:1 wt. ratio did not significantly increase RB oxidation. The results confirm that addition of CeO2 to ZnO has resulted in lowering its bandgap energy and in-turn favors oxidation of RB dye under UV light.