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

Abstract

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.