Amorphous Iron Oxide Decorated 3D Heterostructured Electrode for Highly Efficient Oxygen Reduction

Abstract

Low-temperature reduction of oxygen with high efficiency is required for widespread application of electrochemical devices. Noble metal catalysts are favored for use as the surface modifier on ceramic electrodes to enhance their oxygen reduction reactivity. However, the disadvantages of noble metals, such as sintering and high price, restrict their practical applications. Here, we present a 5-nm-thick amorphous iron oxide thin film decorated electrode possessing not only high electrocatalytic activity comparable to that of the platinum (Pt) modified one but also improved stability. The iron oxide is deposited into porous perovskite SrSc0.2Co0.8O3−δ (SSC) by chemical vapor deposition (CVD), forming a three-dimensional (3D) heterostructured electrode using ferrocene as the precursor. The importance of CVD is not only ensuring the uniform distribution of iron oxide but also allowing the iron oxide to be amorphous. At 700 °C, the area specific resistance (ASR) of the 3D heterostructured cathode is reduced to 0.01 Ω cm2, which is only 50% of that of the unmodified one, and the derived single fuel cell achieves higher power delivery. The electrode operates stably at 650 °C for 250 h without any degradation, while the performance of Pt modified SSC starts to degrade only after 30 min. These results suggest that amorphous iron oxide can be used as the catalyst to improve oxygen reduction reaction (ORR), with the benefits of long-lifetime and low cost.