La0.8Sr0.2Co1-xMnxO3 perovskites as efficient bi-functional cathode catalysts for rechargeable zinc-air batteries

In this work, the La0.8Sr0.2Co1-xMnxO3 (x = 0, 0.2, 0.4, 0.6, 0.8, 1) perovskites (LSCM) were synthesized by a facile improved sol-gel method. The crystalline structures, morphologies, Co/Mn valence states and oxygen adsorption/desorption behavior of the LSCM materials are systematically studied, and their catalytic activities toward ORR and OER are investigated by the rotating-disk electrode (RDE) and zinc-air battery techniques. It is found that the proper substitution of Co with Mn can efficiently improve the ORR and OER activities of La0.8Sr0.2CoO3 perovskite at the same time. The LSCM-60 catalyst exhibits the optimum bi-functional activity. It is mainly attributed to the regulation of the Bi-site Co/Mn valence states and the improvement of the oxygen adsorption/desorption capability. Besides of the good bi-functional property, LSCM-60 shows superior durability compared with Pt/C and IrO2 catalysts. When using LSCM-60 as the cathode catalyst of zinc-air batteries, the low charge-discharge overpotential (1.05 V at 50 mA cm−2) and the excellent long-term cycle stability were obtained. This study exhibits the possibility to improve the bi-functional activity of La0.8Sr0.2CoO3 through a simple doping process.

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