Modulating Charge Transfer via Coordination Engineering in C ₅₆₈ -Fe-3N@M (M = B, C, S) Single-Atom Catalysts for CO ₂ Electroreduction to Methane

Electrocatalytic CO 2 reduction to fuels requires catalysts with high activity and selectivity. Here, a nitrogen-doped carbon support anchoring single Fe atoms (C 568 -Fe-4N) was modeled using C 568 as the prototype, and nonmetal dopants were introduced to form C 568 -Fe-3N@M (M = B, C, S) single-atom catalysts. Calculations show that tuning the coordinating atom is more effective than varying coordinating N, especially for CO 2 activation and the first protonation step. Appropriate σ-donation/π-backdonation balances CO 2 adsorption and activation, lowering the barrier for the first protonation. C 568 -Fe-3N@M delivers lower limiting potentials than Cu(211); C 568 -Fe-3N@B reaches −0.44 V. Electronic-structure analyses indicate that coordination-driven orbital optimization at the potential-determining step reduces reaction barriers.