Engineering of Fe d-band center in Fe₃O₄/CeO₂ hetero-nanoparticles via orbital coupling for high-efficiency oxygen reduction electrocatalysis

The deliberate engineering of the d-band center of metal site represents an effective strategy to boost the intrinsic electrocatalytic performance toward the oxygen reduction reaction (ORR). Herein, following a heterointerface-induced orbital coupling rationale, we report a judicious design of an efficient ORR electrocatalyst consisting of Fe₃O₄/CeO₂ hetero-nanoparticles in-situ encased into N-doped carbon nanofibers (abbreviated as Fe₃O₄/CeO₂@N-CNFs hereafter). The theoretic calculations uncover that the Fe₃O₄/CeO₂ heterointerface-triggered orbital coupling can cause the down shift of the d-band center positions of Fe sites, which leads to the weakened chemisorption of oxygenated groups and lowered energy barrier for the potential-determining step, ultimately dramatically boosting the ORR intrinsic activity. As a consequence, the well-designed Fe₃O₄/CeO₂@N-CNFs display admirable ORR activity with a half-wave potential of 0.84 V and outstanding structural/electrochemical stability in an alkaline electrolyte, surpassing the commercial Pt/C benchmark and a majority of recently reported Fe₃O₄-based electrocatalysts. More encouragingly, the Fe₃O₄/CeO₂@N-CNFs-incorporated Zn-air battery outperforms the Pt/C-assembled counterpart with higher power density, larger energy density, and excellent cycling stability, serving as a competent candidate for ORR-involved renewable energy setups. This study offers an innovative approach for the rational manipulation of the d-band center and interfacial electron behavior of active sites toward the optimization of electrocatalytic performance.