“Outside‐in”Design of Single‐Atom Catalysts: Linking Specific Peripheral Geometry to Defined CO2 Reduction Performance

The regulation of single‐atom catalyst (SAC) through microenvironment engineering, particularly via peripheral species, has recently garnered significant attention in the fields of materials science and heterogeneous catalysis. Nevertheless, establishing unambiguous structure‐property relationships for SAC, especially concerning peripheral effects, remains a significant challenge. Herein, we propose a strategy for the design of N‐doped carbon‐supported Fe SACs for CO2 reduction reaction (CO2RR). Density functional theory calculations reveal that installing five‐ or six‐membered ring in the outer shell modulates the electronic properties of the inner‐shell coordination N species, altering their electron transfer capabilities while fine‐tuning the d‐p coupling between the Fe center and adjacent N atoms. Notably, five‐membered rings induce stronger d‐p coupling compared to their six‐membered counterparts, leading to higher Fe valance state. This electronic modulation optimizes the adsorption strength of key CO2RR intermediates (COOH* and CO*), enhancing catalytic performance for CO production. Extensive experimental studies corroborate these theoretical findings. The proposed “outside‐in” design strategy can be extended to Ni SACs, offering new insights into the exploration of highly efficient single‐atom centers through peripheral geometric effects.