Double synergetic FeCo-nanoparticles and single atoms embedded in N-doped carbon nanotube arrays as efficient bifunctional catalyst for high-performance zinc-air batteries

Herein, we report the design and fabrication of an efficient bifunctional electrocatalyst of biphasic FeConanoparticles and Fe, Co single atoms embedded in N-doped carbon nanotube (FeCo-NCNT) arrays, in which FeCo-nanoparticles are embedded inside each carbon nanotube, while Fe, Co single atoms are doped into the carbon nanotube matrix. The as-prepared electrocatalyst exhibits excellent bifunctional oxygen activity, with a low overpotential of 304 mV for the oxygen evolution reaction and a high halfwave potential (0.861 V) for the oxygen reduction reaction, resulting in a low potential gap (DE) of 0.673 V. The exceptional composite design and synergistic interaction of each component are responsible for the excellent bifunctional catalytic performance. Furthermore, FeCo-NCNT arrays on carbon cloth are used as binder-free air cathodes for both aqueous zinc-air batteries (ZABs) and flexible quasi-solid-state ZABs, which also have a high specific capacity of 881.8 mAh/gZn and excellent stability (working life of >245 h at 5 mA/cm2) for aqueous ZABs. Density functional theory calculation further reveals the synergy mechanism between Fe-N4, Co-N4 atomic sites and FeCo-nanoparticles, which can induce higher Fe-d/ Co-d anti-bond orbitals filling degree and weaken the binding ability of oxygen intermediates, as a result in improving the oxygen evolution reaction/oxygen reduction reaction activity. (c) 2022 Elsevier Ltd. All rights reserved.