Breaking 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 in the well-defined Fe-N4 sites, resulting in low selectivity for CO2 conversion to CO. Theoretical calculations reveal that introduction of axial coordinated N atom 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 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.