Electronic modulation induced by decorating single-atomic Fe-Co pairs with Fe-Co alloy clusters toward enhanced ORR/OER activity

Modulating the electronic properties of single-atomic metal sites with metal clusters is a promising strategy for boosting their intrinsic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity. Herein, we report an effective isolation-confinement strategy for synthesis of well-dispersed Fe-Co atom clusters and N4Fe-CoN4 atomic pair sites on carbon nanofibers (marked as β-FeCo-PCNF), in which the addition of β-cyclodextrin is crucial in avoiding the agglomeration of metal species. The Fe-Co atomic clusters induce a downward shift in the d-band center of Fe-Co atomic sites, and this shift effectively reduces the adsorption energy of OOH* on Fe-Co atomic sites, resulting in lower energy barriers for ORR and OER. Remarkably, the β-FeCo-PCNF-based Zn-air battery exhibits excellent power density and cycling stability. This work paves the way for a universal strategy to regulate the electronic localization of atomic pair sites by alloy clusters and provides essential guidance for designing multifunctional electrocatalysts.