Preparation of Dumbbell-like Er/ZnO Microrods with Efficient Energy Upconversion for the Catalytic Degradation of Tartaric Acid in Water

Abstract

Photon upconversion element, Er, doped in bulk and nanostructured ZnO materials synthesized using a traditional hydrothermal method has been conducted in this study to promote efficient energy upconversion for better photocatalytic degradation of tartaric acids in water under the irradiation of visible light. The FE-SEM images clearly reveal that the Er/ZnO crystallites self-organized into dumbbell-like microrods with moderate addition of PVP as a dispersant agent. The photocatalytic activity was investigated by photodegradation of water containing an aqueous tartaric acid solution under visible light irradiation for 6.5 h. Among the prepared photocatalysts, the first-order rate constant reaches the maximum of 2.5 × 10⁻³ min⁻¹ with Er/ZnO-4 catalyst. Moreover, the Er ions provide a favorable redox potential, which resulted in the photoproduction of electronic defects and the inhibition of electron–hole recombination. The surface favored the generation of positive holes, which were considered to be the active centers of the reaction. Thus, the generation of holes leads to an effective removal of the tartaric acid.