Interface Engineering of MOF-on-MOF Derived Fe,Cu-N-C Catalysts for Efficient Oxygen Reduction Reaction

The development of efficient and stable non-precious metal electrocatalysts for the oxygen reduction reaction (ORR) is critical for advancing fuel-cell technology. This work presents an interface-engineering strategy based on a MOF-on-MOF precursor design, in which CuZn-ZIFs are epitaxially grown in situ on the surface of MIL-101(Fe), forming a spatially hierarchical MIL-101(Fe)@CuZn-ZIFs-x composite. Pyrolysis of this composite yields a series of Cu/Fe bimetallic nitrogen-doped carbon catalysts (Fe@CuNC-x). Structural characterization reveals that the optimized Fe@CuNC-3 catalyst possesses a unique composite polyhedral morphology, a high specific surface area (1164.5 m 2 g −1 ), and a hierarchical porous architecture. In alkaline medium, Fe@CuNC-3 exhibits outstanding ORR performance with a half-wave potential of 0.88 V, surpassing that of commercial Pt/C (0.84 V), an electron-transfer number close to the ideal four-electron pathway ( n = 3.97), excellent methanol tolerance, and long-term operational stability (∼95% current retention after 21600 s). The performance enhancement is attributed to the stable Cu x Fe 1−x alloy structure formed between Fe and Cu, which effectively optimizes the electronic properties of the active sites and suppresses metal leaching and carbon corrosion. This study provides a novel precursor engineering route for constructing high-performance bimetallic nitrogen-carbon ORR catalysts.