Engineering Active CeO2/Fe3C Interfacial Sites to Generate High-Charge-Density Fe for Enhanced Oxygen Reduction Reaction Efficiency

Abstract

The practical application of Fe₃C-based catalysts is hindered by two major challenges: the continuous dissolution of Fe atoms and the strong adsorption of oxygen intermediates. To overcome these limitations, a novel rare earth (RE) oxide/iron carbide heterostructure is designed, featuring abundant active CeO₂/Fe₃C interfacial sites anchored on N-doped carbon substrates (CeO₂/Fe₃C@N-C). The CeO₂/Fe₃C@N-C catalyst exhibits exceptional alkaline oxygen reduction reaction (ORR) performance, with a half-wave potential (E_1/2) of 0.926 V and remarkable durability, sustaining over 20 000 cycles with minimal degradation. These metrics surpass those of commercial 20% Pt/C and most reported Fe₃C-based electrocatalysts. When applied as a cathode catalyst in Zn–air batteries (ZABs), CeO₂/Fe₃C@N-C achieves a high-power density of 204 mW cm⁻², demonstrating its practical potential. Through a combination of experimental characterization and density functional theory (DFT) calculations, the mechanistic origins of enhanced performance is uncovered. CeO₂ acts as an electron donor, inducing electron redistribution at the CeO₂/Fe₃C interface and resulting in electron accumulation at the Fe active sites. This work not only demonstrates a high-performance ORR catalyst but also provides fundamental insights into the role of RE oxides in enhancing Fe₃C-based electrocatalysts. The findings offer a strategic pathway for designing advanced energy conversion materials with improved activity, stability, and efficiency.