Orbital engineering of Fe3C nanocluster decorated Fe single atom enables a superior oxygen reduction performance

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Interfacial electron regulation between transition metal single atoms and metal carbide clusters is crucial for improving the catalytic activity in electrochemical oxygen reduction reaction (ORR). However, precisely controlling the heterointerface and in-depth understanding of structure-catalytic activity correlations of such catalysts remain a challenge. Herein, we developed a facile metallo-supramolecular network-confinement pyrolysis strategy for fabricating the heterostructured electrocatalyst of iron carbide nanoclusters-coupled iron single atoms on hierarchically nitrogen, sulfur-doped porous carbon nanosheets (Fe 3 C NCs -Fe SAs /NSC). Benefiting from a strong interfacial electronic effect on atomic Fe sites, the hybrid electrocatalyst Fe 3 C NCs /Fe SAs -NSC manifests exceptional oxygen reduction activity with half-wave potentials of 0.92 V in 0.1 M KOH and 0.84 V in 0.1 M HClO 4 solution, as well as excellent electrochemical stability. In addition, it delivers high performance in lab-made zinc-air batteries. Theoretical results indicate that the presence of Fe 3 C NCs can intensively tailor the electronic structure and d-band center of the outer Fe single atoms, which is conducive to lowering the energy barriers of the rate-determining step, allowing for accelerating kinetics during the ORR process. This work develops new methodology for the design of single atom site-cluster integrating catalysts and offers new insights into interfacial electron regulation.