CeO₂ boosted Fe-N₅ electrocatalyst via relay catalysis for modulating oxygen reduction reaction in Al-air batteries

Abstract

Atomically dispersed iron-nitrogen-carbon (Fe-N-C) catalysts have demonstrated promising oxygen reduction reaction (ORR) activity. It poses a formidable challenge to simultaneously optimize the adsorption energies of multiple intermediates at a single active site. In addition, the lack of long-term stability remains a significant problem due to the unavoidable 2-electron by-product hydrogen peroxide (H₂O₂). Here, multiple active sites are achieved to modulate the adsorption energy of intermediates while removing the by-product of the reaction by growing the second active site CeO₂ nanoparticles in situ on the surface of the hollow-structured Fe-N₅, thus improving the efficiency and stability of the Fe-N₅/CeO₂. Density functional theory (DFT) calculations are employed to probe into the synergistic catalytic interaction between Fe-N₅ and CeO₂, proposing a relay catalytic mechanism underlying the enhanced catalytic activity. Furthermore, the catalyst stability is enhanced due to the ability of CeO₂ to scavenge the reaction by-product and inhibit its destructive effects on the Fe-N₅ active site. Additionally, the liquid Al – air batteries equipped with Fe-N₅/CeO₂ display a higher power density. This work proffers an innovative vista for the conception and refinement of multi-active-site catalysts with excellent catalytic performance and prolonged lifespan.