High-performance non-spinel cobalt-manganese mixed oxide-based bifunctional electrocatalysts for rechargeable zinc-air batteries

Development of efficient bifunctional electrocatalysts from earth abundant elements, simultaneously active for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), remains to be a grand challenge for electrocatalysis. Herein we firstly synthesized a new type of bifunctional catalyst (NCNT/Co_xMn_1-xO) consisting of non-spinel cobalt-manganese oxide supported on N-doped carbon nanotubes through a simple non-surfactant assistant hydrothermal method. This hybrid catalyst exhibits much higher OER activity than that of IrO₂, and comparable ORR activity to Pt/C with identical onset potential (0.96V) in alkaline media. Furthermore, the NCNT/Co_xMn_1-xO catalyst was studied as a cathode in both primary and rechargeable zinc-air batteries demonstrating similar performance to commercial Pt/C or (Pt/C+IrO₂), respectively. Primary zinc-air battery tests show a gravimetric energy density of 695WhkgZn-1, and the rechargeable battery exhibits a high round-trip efficiency evidenced by a low discharge-charge voltage gap (0.57V) at a current density of 7mAcm^-2.