In Situ Symbiosis of Cerium Oxide Nanophase for Enhancing the Oxygen Electrocatalysis Performance of Single-Atom Fe─N─C Catalyst with Prolonged Stability for Zinc-Air Batteries.

The Fenton reaction, induced by the H 2 O 2 formed during the oxygen reduction reaction (ORR) process leads to significant dissolution of Fe, resulting in unsatisfactory stability of the iron-nitrogen-doped carbon catalysts (Fe-NC). In this study, a strategy is proposed to improve the ORR catalytic activity while eliminating the effect of H 2 O 2 by introducing CeO 2 nanoparticles. Transmission electron microscopy and subsequent characterizations reveal that CeO 2 nanoparticles are uniformly distributed on the carbon substrate, with atomically dispersed Fe single-atom catalysts (SACs) adjacent to them. CeO 2 @Fe-NC achieves a half-wave potential of 0.89 V and a limiting current density of 6.2 mA cm -2 , which significantly outperforms Fe-NC and commercial Pt/C. CeO 2 @Fe-NC also shows a half-wave potential loss of only 1% after 10 000 CV cycles, which is better than that of Fe-NC (7%). Further, H 2 O 2 elimination experiments show that the introduction of CeO 2 significantly accelerate the decomposition of H 2 O 2 . In situ Raman spectroscopy results suggest that CeO 2 @Fe-NC significantly facilitates the formation of ORR intermediates compared with Fe-NC. The Zn-air batteries utilizing CeO 2 @Fe-NC cathodes exhibit satisfactory peak power density and open-circuit voltage. Furthermore, theoretical calculations show that the introduction of CeO 2 enhances the ORR activity of Fe-NC SAC. This study provides insights for optimizing SAC-based electrocatalysts with high activity and stability.