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

Abstract

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.