Cu-N-C assisted MnO nanorods as bifunctional electrocatalysts for superior long-cycle Zn-air batteries

Abstract

The main factor constraining the performance of zinc-air batteries (ZABs) is the slow kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), for which high performance electrocatalysts are greatly needed. However, the state-of-the-art oxygen electrocatalysts still suffer from the low activity and limited stability. Herein, we report the synthesis of a novel MnO@Cu-N-C core-shell nanostructure comprising MnO nanorods coated by a Cu-N-C shell that is derived from zeolitic-imidazolate frameworks. The as-prepared MnO@Cu-N-C exhibits fairly high bifunctional electrocatalytic activity toward both ORR and OER, showing a combined overpotential as low as 0.80 V. Both experiments and theoretical calculations indicate that the superior performance is benefited from the synergy between MnO and Cu-N-C, which facilitates the interfacial electron transfer and thus leads to the lower overpotentials. When being employed as the air electrode in the rechargeable ZABs, MnO@Cu-N-C displays a high peak power density of 196.8 mW cm−2 and an impressively prolonged cycle life over 650 h at 10 mA cm−2, outperforming most of recently reported Mn-based counterparts. Moreover, its excellent electrochemical performance can also be transferred to solid-state ZABs, as showcased by a power density of 66.6 mW cm−2 and a cycle life of 16 h at 2 mA cm−2.