3D carbon framework-supported CoNi nanoparticles as bifunctional oxygen electrocatalyst for rechargeable Zn-air batteries

Abstract

The rational design of optimal bifunctional oxygen electrocatalysts with low cost and high activity is greatly desired for the large-scale implementation of rechargeable Zn-air batteries. Herein, a novel bifunctional electrocatalyst with CoNi alloy nanoparticles supported by a butterfly wing-derived carbon framework (denoted as CoNi/BCF) was synthesized via a pyrolysis method. The obtained CoNi/BCF exhibited excellent oxygen electrocatalytic activity and stability in terms of a positive halfwave potential (0.80 V) for the oxygen reduction reaction (ORR) and a low overpotential (370 mV at 10 mA cm−2) for the oxygen evolution reaction (OER). Remarkably, the high bifunctional ORR/OER activity (ΔE(ORR–OER) = 0.80 V) also endows an excellent Zn-air battery performance with a high energy density of 853.1 mWh gZn−1, a peak power density of 155.1 mW cm−2, and an excellent cyclability of over 180 cycles at 10 mA cm−2. The satisfactory electrocatalytic performance is due to the synergetic effect between CoNi alloy nanoparticles and nitrogen-doped carbon framework, which includes the high conductivity, highly dispersed active sites and optimized electronic configuration and reaction pathways. Additionally, the smart structures of butterfly wings endow the hybrid catalyst with a large surface area, which is beneficial for the mass transfer, active sites exposure and the fixation of alloy nanoparticles. Our work presents a strategy to take full advantage of natural organisms, rich elements, and naturally optimized smart structures combined in a two-in-one solution, leading to significant improvements in the electrochemical performance. The realization of rechargeable Zn-air batteries also paves a new way for the design and development of efficient and stable electrocatalysts for energy conversion and storage devices.