Strengthened CO ₂ -to-CO Electroreduction from Low-Concentration CO ₂ Streams via the Phosphorus Heteroatoms-Regulated Electronic Structure of a Single Atomic FeN ₄ Catalyst

Single atomic Fe catalysts have demonstrated excellent activity for pure CO 2 electroreduction (CO 2 RR). However, designing a highly active catalyst for efficient CO 2 RR from streams with diluted CO 2 concentration remains a significant challenge. Herein, P atoms were introduced into the second coordination shell of FeN 4 (FeN 4 P), forming Fe–N–P bonds to facilitate the CO 2 -to-CO conversion in an aqueous solution. The incorporation of P atoms enhanced both the activity and selectivity toward CO, reaching a maximum CO Faradaic efficiency (FE CO ) of 96.2 ± 0.5% at a current density exceeding −200 mA cm –2 in 0.5 M KHCO 3 . Moreover, the superior activity was further demonstrated by the 80.5 ± 2.3 and 61.5 ± 1.3% FE CO at optimized conditions from streams containing only 15 and 5% CO 2, respectively. In situ characterizations reveal that the asymmetric FeN 4 P structure enhanced the kinetics of adsorbed CO 2 reduction. Density functional theory calculation revealed that the electron-enriched FeN 4 center, modulated by the adjacent P atom, facilitated CO 2 adsorption and activation and lowered the energy barrier for *COOH formation, thereby promoting CO 2 -to-CO conversion.