Identifying the impact of Fe nanoparticles encapsulated by nitrogen-doped carbon to Fe single atom sites for boosting oxygen reduction reaction toward Zn-air batteries

Herein, a proof-of-concept study on the evaluation of Fe nanoparticles (Fe NPs) encapsulated by nitrogen-doped carbon to Fe single atoms (Fe SAs) for boosting the oxygen reduction reaction (ORR) catalytic activity toward Znair batteries was reported. Specifically, unlike Fe SAs encapsulated by nitrogen-doped carbon (Fe SAs@NC), the Fe SAs and Fe NPs co-embedded in nitrogen-doped carbon (Fe SAs/NPs@NC) derived from a pyrolysis and acid dissolution protocols exhibits excellent ORR performance with good stability and remarkable methanol tolerance in alkaline solutions. Combining a series of experimental analyses, the strong interaction between the atomically dispersed Fe-Nx and adjacent Fe NPs in altering the electronic structure of isolated Fe-Nx sites could weaken the binding energies of the ORR intermediates on Fe SAs/NPs@NC, resulting in an enhanced electrocatalytic kinetics than Fe SAs@NC and Pt/C catalysts. This strategy not only offers a new way for synthesis highly efficient Fe-N/C catalysts toward ORR, but also provides the new insights into the understanding of the mechanism of adjacent Fe NPs encapsulated by nitrogen-doped carbon to Fe SAs sites.

Automated summary

In this proof-of-concept study, Fe nanoparticles encapsulated by nitrogen-doped carbon were evaluated and compared to Fe single atoms for boosting the catalytic activity of the oxygen reduction reaction (ORR) in Znair batteries. The Fe single atoms and Fe nanoparticles embedded in nitrogen-doped carbon exhibited excellent ORR performance with good stability and remarkable methanol tolerance. The strong interaction between the atomically dispersed Fe-Nx and adjacent Fe nanoparticles alters the electronic structure and enhances the electrocatalytic kinetics.