Synergistic Charge Redistribution in a Dual-Atomic Fe-CoN6 on Nanofiber With Fe-N Site Preference of Intermediates Compared to Pristine Fe Single Atoms for Oxygen Redox in Zinc-Air Battery.

Reducing the reaction barriers of the oxygen reduction reaction (ORR) and accelerating the reaction kinetics of zinc-air batteries (ZABs) requires unique advantages in regulating electron orbitals with weakened adsorption of oxygen intermediates and conductive dissociation with a negative shift of the d-band center. The sluggish ORR and unstable Zn/electrolyte interface at relatively high-rate ability require bifunctional electrolysis. Herein, a multi-walled carbon nanotube (MWCNT) and resorcinol-formaldehyde (RF) polymer composite resulted nanofiber in which Fe and Co-atomic sites were incorporated in FeA-CoA/MWCNT-NC. As compared between the bridging Fe-Co and lateral Fe-Co model by Density Functional Theory (DFT) simulation and Bader charge analysis, optimal charge transfer at bridging with faster ORR kinetics as a result of balanced adsorption energy and electron distribution suggests a Fe-Co bridging model is more active. A comparison of ORR and ZAB with single-atomic FeSA950NC supports the DFT results of charge distribution and weakened adsorption of ORR intermediates. ORR and ZAB results reveal: 1) bridging atom sites with moderate charge polarization due to delocalization of d-band electrons, 2) significant electron conduction, 3) more adsorption-desorption on Fe-N sites. These findings offer insights into the electron redistribution in sites of electrodes and rational design for high-performance electrodes in energy storage devices.