Bifunctional electrocatalysts of lanthanum-based perovskite oxide with Sb-doped SnO_2 for oxygen reduction and evolution reactions

摘要

Bifunctional electrocatalysts for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are developed with perovskite-type oxide catalyst and antimony-doped tin oxide (ATO) as an oxidation-resistant conductive additive to increase the stability under an oxidizing atmosphere. In conventional carbon-supported catalysts, carbon plays an important role not only in increasing electric conductivity but also in catalyzing the first 2-electron reaction of the ORR. The ATO-mixed catalyst itself requires a perovskite-type oxide (ABO(3)) catalyst that is active in the first step of the ORR, such as La0.6Ca0.4MnO3 (LCMO), because of the poor ORR activity of ATO. On the other hand, OER performance strongly depends on the composition of the perovskite oxide and La0.6Ca0.4CoO3 (LCCO) shows high OER activity. Here, La0.6Ca0.4Co0.7Mn0.3O3 (LCCMO), in which Co and Mn are mixed at the B site of the perovskite-type oxide, mixed with ATO is proposed as a carbon-free bifunctional catalyst that shows activity for both the ORR and OER. The activity and durability of gas-diffusion air electrodes with the bifunctional catalysts are evaluated in zinc-air batteries, and the results suggest that the catalyst with ATO achieved similar charge-discharge performance and a longer lifetime compared to the conventional catalyst with carbon.