One-pot achievement of MnO2/Fe2O3 nanocomposites for the oxygen reduction reaction with enhanced catalytic activity

Abstract

MnO₂/Fe₂O₃ nanocomposites were achieved via using KMnO₄ and FeCl₃ as starting materials in aqueous solution followed by hydrothermal and high-temperature treatment processes. The hydrolysis of FeCl₃ produces H⁺ ions to react with KMnO₄ to produce MnO₂, which further accelerates the hydrolysis process. The as-synthesized MnO₂/Fe₂O₃ nanocomposites present high oxygen reduction reaction activity with an onset and half-wave potential of 0.953 and 0.859 V vs. RHE, respectively, and a limited current density of 4.875 mA cm⁻² at 0.565 V, which are comparable to those of the commercial Pt/C catalyst. The excellent catalytic performance is considered to originate from the high Mn³⁺ content and the related oxygen vacancies. Furthermore, the unsatisfactory stability of the MnO₂/Fe₂O₃ nanocomposites can be solved by coating with a layer of polyaniline-derived carbon.