Boosting CO₂ reduction on Fe-N-C with sulfur incorporation: Synergistic electronic and structural engineering

Developing earth-abundant efficient catalysts for CO₂ reduction reaction (CO₂RR) is of paramount importance for electrochemical conversion of CO₂ into value-added products. Despite numerous studies on iron and nitrogen codoped carbon (Fe-N-C) catalysts, grand challenges exist due to limited performance and understanding of catalytic mechanisms. This study reports a general strategy to boost electrocatalytic CO₂RR activity of Fe-N-C with the incorporation of S atoms to engineer carbon support structure and electronic properties of active Fe–N sites simultaneously via a copolymer-assisted synthetic approach. The employment of N,S comonomers significantly increases the numbers of micropores and surface area, enabling dense atomic Fe–N and enhanced utilization efficiency. The first-principles calculations reveal that S modulation upraises the Fermi energy of Fe 3d and increases charge density on Fe atoms of Fe–N₄, thereby enhancing intrinsic catalytic reactivity and selectivity for CO₂ reduction by strengthening the binding interaction between the Fe site and key COOH* intermediate. These integrated structural and electronic merits endow Fe-NS-C with outstanding activity (e.g., CO Faradaic efficiency of 98% at an overpotential of 490 mV) and stability (without deactivation in 30 h), ranking it one of the most active Fe-N-C reported to date. The finding offers an innovative design strategy to enable the design of advanced catalysts for CO₂ conversion.