Increasing the number of modulated Fe single-atom sites by adjacent nanoparticles for efficient oxygen reduction with spin-state transition

Abstract

Utilizing the nanoparticles (NPs) to improve the oxygen reduction reaction (ORR) performance of Fe single atoms (SAs) is conducive, but it is far from further application due to its limited number of enhanced SAs site and unclear origin of the enhanced electrocatalytic activity. Herein, we develop a hybrid catalyst contains a high density of activated SAs and explored the origin of this excellent activity. In the hybrid catalyst, the isolated Fe SAs are clustered within 2 nm around CFe2.5NPs ((CFe2.5)NP/FeSA-N-C), implying that these Fe SAs active sites are being modulated and enhanced. Further theory reveals those strong interactions between Fe SAs and adjacent CFe2.5 NPs induces transition of spin-polarization configuration of Fe centers from high spin state to low spin state, leading to weakened bonding strength of Fe atoms and OOH*. The optimized (CFe2.5)NP/FeSA-N-C possesses a superior ORR performance, and exhibits an amazing application potential in zinc-air batteries.