B-Site Doping Boosts the OER and ORR Performance of Double Perovskite Oxide as Air Cathode for Zinc-Air Batteries

Double perovskite oxides are key players as oxygen evolution and oxygen reduction catalysts in alkaline media due to their tailorable electronic structures by doping. In this study, we synthesized B-site doped NdBaCo_aFe_2-aO_5+δ (a=1.0, 1.4, 1.6, 1.8) electrocatalysts, systematically probed their bifunctionality and assessed their performance in zinc-air batteries as air cathodes. X-ray photoelectron spectroscopy analysis reveals a correlation between iron reduction and increased oxygen vacancy content, influencing electrocatalyst bifunctionality by lowering the work function. The electrocatalyst with highest cobalt content, NdBaCo_1.8Fe_0.2O_5+δ exhibited a bifunctionality value of 0.95 V, outperforming other synthesized electrocatalysts. Remarkably, NdBaCo_1.8Fe_0.2O_5+δ, demonstrated facilitated charge transfer rate in oxygen evolution reaction with four-electron oxygen reduction reaction process. As an air cathode in a zinc-air battery, NdBaCo_1.8Fe_0.2O_5+δ demonstrated superior performance characteristics, including maximum capacity of 428.27 mA h at 10 mA cm^-2 discharge current density, highest peak power density of 64 mW cm^-2, with an enhanced durability and stability. It exhibits lowest voltage gap change between charge and discharge even after 350 hours of cyclic operation with a rate capability of 87.14 %.