Transition metal MN4 macrocycle-derived bifunctional ORR/OER electrocatalysts for air electrodes in rechargeable zinc-air batteries

Abstract

Secondary Zn-air battery (ZAB), also known as rechargeable ZAB, is one of the most viable alternatives for Li-ion batteries for light transportation, electric vehicles, and portable electronics. Therefore, its development potential is significant, but at present it is limited mainly by the need for platinum-group-metal (PGM)-based air electrode materials to catalyze the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). MN₄ macrocyclic complexes, which have a central metal atom coordinated to surrounding nitrogen atoms, have emerged as one of the most promising alternatives to PGM-based catalysts for the ZAB air electrode, creating an intense and competitive research field. This review summarizes the most important MN₄ macrocycle-derived air electrode catalyst developments in recent years for rechargeable ZABs, while also highlighting some critical issues.