"Outside-in" Design of Single-Atom Catalysts: Linking Specific Peripheral Geometry to Defined CO₂ Reduction...

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(DFT) 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 a higher Fe valence 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.