Axial N Disrupt d –π Conjugation of Asymmetric Fe─Cu Dual‐Atom Enhances CO ₂ Electroreduction

ABSTRACT

Precise spin‐polarization modulation of electronic structures in dual single‐atomic sites (DSAS) is critical yet challenging for boosting electrocatalytic CO ₂ reduction reaction (CO ₂ RR). Here, we report a Fe 3 d ‐orbital spin‐polarization regulation strategy through constructing an axial N‐bridge bond and adjacent Cu–N ₄ on hollow bilayer Fe–Cu dual single‐atom catalysts (HFeCu–N–C DSACs). Experimental and theoretical evidence demonstrate that the axial N‐bridge bond disrupts the D _4h symmetry of the Fe–N ₄ active center, resulting in the rearrangement of Fe 3 d electrons and thereby breaking the surface d –π conjugate structure (Fe–N–C). Meanwhile, the Jahn‐Teller effect of the adjacent Cu–N ₄ sites is inferred to potentially regulate the spin state of Fe sites, which facilitates the transition from low‐spin ( ↓↑ , ↓↑ , ↑ , _, _) to high‐spin ( ↑ , ↑ , ↑ , ↑ , ↑ ). Therefore, the increased population of unpaired electrons on d _xz , and d _yz orbitals is pivotal for stabilizing the π ^* orbitals of CO ₂ and activating CO ₂ , thus enhancing the intrinsic reaction activity of HFeCu–N–C DSACs. The as‐made HFeCu–N–C DSACs present a superior faraday efficiency (FE) of a highly selective CO product, 99.32% @ −0.5 V (vs. RHE), and long‐term durability. This work provides a new strategy for tuning the electronic spin state of DSACs to boost CO ₂ RR electrocatalytic performance.