Sublimation Transformation Synthesis of Dual‐Atom Fe Catalysts for Efficient Oxygen Reduction Reaction

Abstract

Dual‐atom catalysts (DACs) have garnered significant interest due to their remarkable catalytic reactivity. However, achieving atomically precise control in the fabrication of DACs remains a major challenge. Herein, we developed a straightforward and direct sublimation transformation synthesis strategy for dual‐atom Fe catalysts (Fe2/NC) by utilizing in situ generated Fe2Cl6(g) dimers from FeCl3(s). The structure of Fe2/NC was investigated by aberration‐corrected transmission electron microscopy and X‐ray absorption fine structure (XAFS) spectroscopy. As‐obtained Fe2/NC, with a Fe−Fe distance of 0.3 nm inherited from Fe2Cl6, displayed superior oxygen reduction performance with a half‐wave potential of 0.90 V (vs. RHE), surpassing commercial Pt/C catalysts, Fe single‐atom catalyst (Fe1/NC), and its counterpart with a common and shorter Fe−Fe distance of ~0.25 nm (Fe2/NC‐S). Density functional theory (DFT) calculations and microkinetic analysis revealed the extended Fe−Fe distance in Fe2/NC is crucial for the O2 adsorption on catalytic sites and facilitating the subsequent protonation process, thereby boosting catalytic performance. This work not only introduces a new approach for fabricating atomically precise DACs, but also offers a deeper understanding of the intermetallic distance effect on dual‐site catalysis.