CeO2 Nanoparticle Transformation to Nanorods and Nanoflowers in Acids with Boosted Oxidative Catalytic Activity

Nanoceria (CeO2 nanoparticle) with oxidase-like catalytic activity has been used for a diverse range of analytical, environmental, and nanomedicine applications. In this work, the use of nanoceria for the oxidation of common chromogenic substrates was investigated at low pH, where its activity was greatly enhanced. In addition, the shape of the nanoparticles changed dramatically, yielding nanorods in the presence of adsorbed substrates at pH 1. This work provides an interesting method to synthesize CeO2 nanorods at room temperature. By slightly increasing the reaction temperature, CeO2 nanoflowers were further obtained. This change of shape also affected its catalytic activity, with the nanorods being the most active. The physical and chemical properties of the nanoceria materials were characterized by various spectroscopic, microscopic, and electrochemical techniques. The increased activity at low pH was due to the promoted release of the oxidation product, as well as increased oxygen vacancy concentration and enhanced electron transfer. This work has deepened our understanding of nanoceria as a catalyst, enhanced its catalytic activity, and provided a useful way of controlling its morphology.