Hierarchical Core-Shell Nickel Cobaltite Chestnut-like Structures as Bifunctional Electrocatalyst for Rechargeable Metal-Air Batteries

Abstract

Nano-engineered hierarchical core-shell nickel cobaltite chestnut-like structures were successfully synthesized as a bifunctionally active electrocatalyst for rechargeable metal-air battery applications. Both the morphology and composition of the catalyst were optimized by a facile hydrothermal reaction, resulting in a 10h reacted sample demonstrating significantly enhanced activity toward both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in 0.1m KOH. Specifically, the catalyst demonstrated -0.28 and 0.60V versus SCE (saturated calomel electrode) at the ORR half-wave potential and an OER current density of 10mAcm(-2), respectively. The resulting ORR/OER potential difference of 0.90V was the smallest compared to the catalysts synthesized using 2, 6, and 12h of hydrothermal reaction time. The excellent bifunctional activity of the catalyst is attributed to the nanoscale porous morphology and the spinel nickel cobaltite composition, which improved the active site exposure and transport of reactants and charges during the oxygen reactions.