A perovskite/noble-metal composite as a bifunctional oxygen electrocatalyst for alkaline electrochemical cells

Alkaline-based metal-air batteries require a low-resistance, bifunctional oxygen electrode to perform fast oxygen reduction and oxygen evolution reactions (ORR/OER) during discharging and charging cycles, respectively. However, achieving good ORR/OER bifunctionality with single materials has proven challenging. Here we report a composite material as a bifunctional oxygen electrode for ORR and OER. The composite oxygen electrode consists of an ORR-active 20 wt% Pt/C and an OER-active perovskite La0.6Sr0.4CoO3-$δ$ (LSCO). The study focuses on identifying the optimal LSCO:Pt/C ratio through electrochemical DC voltammetry techniques. The results show that the addition of Pt/C into the LSCO catalyst greatly enhances the ORR activity, due to Pt/C s superior ORR capabilities, while LSCO retains good OER performance, which is known to be poor for Pt/C. The optimal LSCO:Pt/C ratio among the seven compositions studied is found to be 60:40 (wt%) and is tested for stability through using a square-wave potentiostatic method. Overall, this study demonstrates a synergetic effect between LSCO and Pt/C, with each one contributing towards one of the electrode reactions in a positive manner.