Promoting urea oxidation and water oxidation through interface construction on a CeO2@CoFe2O4 heterostructure.

Spinel ferrites are considered practical and promising oxygen evolution reaction (OER) and urea oxidation reaction (UOR) electrocatalysts because of their advantages in the adsorption and activation of electrocatalytic substances. A CeO2 functional metal oxide was used to modify a spinel oxide in order to further improve the electrocatalytic performance of the spinel oxide. In this work, a CeO2@CoFe2O4/NF hybrid nanostructure was synthesized for the first time by typical hydrothermal and calcination methods. In an alkaline medium, CeO2@CoFe2O4/NF displays superior OER activity and needs an overpotential of 213 mV to deliver a current density of 100 mA cm-2, which makes it one of the most active catalysts reported so far. In addition, the as-prepared CeO2@CoFe2O4/NF material needs a potential of 1.40 V at the same current density in 1.0 M KOH with 0.5 M urea, which displays superior UOR activity. The CeO2@CoFe2O4/NF catalyst also displays good durability and the performance of the electrode is negligibly attenuated at a large current intensity of 125 mA cm-2. Experimental results demonstrate that the activity of the CeO2@CoFe2O4/NF catalyst is ascribed to the exposure of more active centers and a faster electron transfer rate. This work develops a novel method for exploiting Earth-abundant, robust and environmentally friendly OER and UOR electrocatalysts.