Supramolecular Complex Derived Carbon Nanotubes Decorated with Iron Single Atoms and Nanoclusters as Efficient Bifunctional Oxygen Electrocatalysts for Rechargeable Zn-Air Batteries

The great attention of rechargeable Zn-air battery has motivated extensive research on the development of inexpensive, highly efficient, and robust noble-metal-free bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, a supramolecular complex derived strategy was used to prepare bamboo-like carbon nanotubes with abundant Fe single atoms and sub-nanometer clusters anchored on tube walls. When served as a bifunctional ORR/OER electrocatalyst, this hybrid showed a small overpotential gap of 0.713 V and excellent stability. More importantly, a large power density of 213 mW cm−2 and stable long-time round-trip charge-discharge performance were achieved for the assembled rechargeable Zn-air batteries. Density functional theory calculations revealed that atomic Fe–N4 moiety in the catalyst could be the essence of high ORR activity, while atomic Fe–N4 moiety coupled sub-nanometer cluster significantly reduces the OER energy barrier. This work provides an effective strategy for the preparation of high-performance and robust oxygen electrode catalysts as well as a significant new insight on the catalytic mechanisms, helping to realize significant advances in energy devices.