In situ exsolution-induced formation of amorphous/crystalline heterointerfaces in Ba_0.6Sr_0.4Co_0.8Fe_0.2O_3-δ for enhanced oxygen electrocatalysis in zinc-air batteries

The main obstacle in the commercial application of aqueous zinc-air batteries (ZABs) are emerging viable, sustainable, and safe alternatives in electrochemical energy conversion technologies. However, the practical realization of ZABs is impeded by four-electron oxygen evolution (OER) and reduction reactions (ORR) and their sluggish kinetics. Herein, we propose a niobium and fluorine co-doping strategy to regulate in situ Ba and Sr exsolution, inducing the formation of amorphous/crystalline Ba_0.6Sr_0.4Co_0.8Fe_0.2O_3-δ heterointerfaces with an alkali treatment. Associated with the formation of a low valence state of cobalt, an abundant oxygen defects, and amorphous/crystalline feature, the catalyst enables enhanced oxygen binding energy in the OER and ORR activities. The optimized bifunctional perovskite oxide (BSCFeN-F_al) catalysts present an excellent oxygen electrocatalytic activity and stability, with much lower OER and ORR overpotentials than other perovskite oxides in this work and with negligible performance decay in accelerated durability testing. When used as an air-electrode, the BSCFeN-F_al demonstrates excellent performance, achieving high power density and remarkable cycling stability. This work highlights the essential function of the heterostructure interface in oxygen electrocatalysis, opening a new avenue to advanced neutral metal-air batteries.