Fabricating Dual-Atom Iron Catalysts for Efficient Oxygen Evolution Reaction: A Heteroatom Modulator Approach.

Understanding the thermal aggregation behaviors of metal atoms is of significant importance for precise synthesis of supported metal clusters. Here, derived from a metal-organic framework encapsulating a trinuclear Fe III 2 Fe II complex (denoted as Fe 3 ) within the channels, a well-defined nitrogen-doped carbon layer is fabricated as an ideal support for stabilizing the generated iron nanoclusters. Atomic replacements of the Fe II by other metal(II) ions (e.g., Zn II /Co II ) via synthesizing isostructural trinuclear-complex precursors (Fe 2 Zn/Fe 2 Co), namely the "heteroatom modulator approach", realizes the inhibition of iron atoms aggregating toward nanoclusters with formation of a stable iron-dimer cluster in an optimal metal-nitrogen moiety within the carbon layer, clearly identified by direct transmission electron microscope imaging with X-ray absorption fine structure analyses. Further, the supported iron dimer, serving as cooperative metal-metal sites, has been experimentally demonstrated for efficient oxygen evolution catalysis. Our findings offer an atomic insight to guide the future design of ultrasmall metal clusters bearing outstanding catalytic capabilities for the vital chemical transformations.