Breaking the electronic distribution symmetry at Fe–N4 sites in iron phthalocyanines enhances CO2 electrochemical reduction

Abstract

Iron phthalocyanines (FePc) feature a typical two-dimensional plane-symmetric structure and a symmetric electron distribution at the well-defined Fe–N₄ sites, resulting in low selectivity for CO₂ conversion to CO. Theoretical calculations reveal that the introduction of axially coordinated N atoms onto the Fe–N₄ motifs can break the electron density symmetry, facilitating electron transfer to CO₂. This enhances CO₂ adsorption and activation while reducing the binding energy of the CO intermediate. To validate these findings, a facile pyrolysis-free co-doping strategy is employed to fabricate the axial N-coordinated Fe–N₄ atomic configuration (Fe–N₅), identified as the active site. The synthesized Fe–N₅ structure exhibits excellent CO₂RR performance for CO production, achieving a selectivity of 96% and a turnover frequency of 5283 h⁻¹. This work provides a pyrolysis-free approach to optimize the local micro-environment of active sites for superior performance.