Modulation in Spin State of Co₃O₄ Decorated Fe Single Atom Enables a Superior Rechargeable Zinc‐Air Battery Performance

Abstract

High‐performance bifunctional electrocatalyst for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is the keystone for the industrialization of rechargeable zinc‐air battery (ZAB). In this work, the modulation in the spin state of Fe single atom on nitrogen doped carbon (Fe1‐NC) is devised by Co3O4 (Co3O4@Fe1‐NC), and a mediate spin state is recorded. Besides, the d band center of Fe is downshifted associated with the increment in eg filling revealing the weakened interaction with OH* moiety, resulting in a boosted ORR performance. The ORR kinetic current density of Co3O4@Fe1‐NC is 2.0‐ and 5.6 times higher than Fe1‐NC and commercial Pt/C, respectively. Moreover, high spin state is found for Co in Co3O4@Fe1‐NC contributing to the accelerated surface reconstruction of Co3O4 witnessed by operando Raman and electrochemical impedance spectroscopies. A robust OER activity with overpotential of 352 mV at 50 mA cm−2 is achieved, decreased by 18 and 60 mV by comparison with Co3O4@NC and IrO2. The operando Raman reveals a balanced adsorption of OH* species and its deprotonation leading to robust stability. The ZAB performance of Co3O4@Fe1‐NC is 193.2 mW cm−2 and maintains for 200 h. Furthermore, the all‐solid‐state ZAB shows a promising battery performance of 163.1 mW cm−2.