Hierarchically porous N-doped carbon confined single-atom Fe catalyst for efficient electrochemical CO₂ reduction

Electrochemical CO₂ reduction reaction (CO₂RR) is a promising process for reducing CO₂ emissions and producing high-value chemicals. However, this process remains hindered by diffusion-limited mass transfer, low activity, and high overpotentials. Here, we controllably prepared hierarchically porous nitrogen-doped carbon, carbon nanosheets, and carbon nanotubes confined single-atom Fe catalysts for electrochemical CO₂ reduction. The hierarchically porous Fe-N-C (Fe-HP) exhibited prominent performance with a Faradaic efficiency of CO (FE_CO) up to 80% and a CO partial current density (j_CO) of −5.2 mA·cm⁻² at −0.5 V vs. reversible hydrogen electrode (RHE), far outperforming the single-atom Fe on N-C nanosheets (Fe-NS) and N-C nanotubes (Fe-NT). The detailed characterizations and kinetic analysis revealed that the hierarchically porous structure accelerated the mass transfer and electron transfer processes toward single-atom Fe sites, promoting the desorption of CO and thereby enhancing CO₂ reduction efficiency. This study provides a promising approach to designing efficient single-atom catalysts with porous structures for energy conversion applications.