One-dimensional Mn3O4/NiCo2S4 nanocomposites as high-performance bifunctional electrocatalyst for rechargeable liquid/flexible Zn-air batteries

Abstract

Rational design of bifunctional oxygen catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with high efficiency and low-cost are significantly in the development of rechargeable Zn-air batteries (ZABs). Herein, it is designed one-dimensional rod-like Mn3O4/NiCo2S4 nanostructure. The inner Mn3O4 nanorod and the outer coating of the NiCo2S4 layers make the composite material have a stable structure, thus exhibiting a rather high bifunctional catalytic activity (ΔE = 0.74 V) and long-term durability toward ORR/OER. An interlaced region is formed at the interface of the dual phases by the Kirkendall effect, where Mn3O4/NiCo2S4 nanocrystals, oxygen vacancies and defects co-exist. The Mn3O4/NiCo2S4 exhibits an onset potential of 0.92 V and a half-wave potential of 0.81 V, and the OER potential is only 1.55 V at 10 mA cm−2. When using this catalyst in rechargeable ZABs, the batteries show a high power density (106.26 mW cm−2), superior rate stability, small charge-discharge voltage gap (0.86 V) and long-term cycles (650 cycles over 216 h at 5 mA cm−2). The flexible ZABs exhibit a high open-circuit voltage of 1.427 V and stably cycled 50 cycles (16.8 h) with a small charge-discharge voltage gap (0.5 V) at 1 mA cm−2.