Atomically Dispersed Fe₂ and Ni Sites for Efficient and Durable Oxygen Electrocatalysis

Developing highly efficient, cost-effective, and robust electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is paramount for the large-scale commercialization of renewable fuel cells and rechargeable metal-air batteries. Herein, a new ternary-atom catalyst that is composed of paired Fe sites and single Ni sites (as Fe₂-N₆ and Ni-N₄) coordinated onto hollow nitrogen-doped carbon microspheres is developed. The as-synthesized catalyst exhibits remarkable activities toward both the ORR and OER in alkaline media, with superior performances to those of the control materials that contain only Fe₂-N₆ or Ni-N₄ sites. Density functional theory calculations and in situ infrared (IR) spectroscopic studies clearly reveal that the Fe₂-N₆ centers are the active sites for both ORR and OER, and their electrocatalytic activities are synergistically enhanced through optimization of their d-band centers by the Ni-N₄ sites. This ternary-atom catalyst can potentially be a promising, alternative, sustainable catalyst to commercially used Pt- and Ru-based catalysts to drive both the ORR and the OER in rechargeable zinc-air batteries and other related applications.