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

In this work, the La 0.8 Sr 0.2 Co 1-x Mn x O 3 (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 La 0.8 Sr 0.2 CoO 3 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 IrO 2 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 La 0.8 Sr 0.2 CoO 3 through a simple doping process.