Gas Diffusion Strategy for Inserting Atomic Iron Sites into Graphitized Carbon Supports for Unusually High‐Efficient CO 2 Electroreduction and High‐Performance Zn–CO 2 Batteries

Emerging single‐atom catalysts (SACs) hold great promise for CO 2 electroreduction (CO 2 ER) , but the design of highly active and cost‐efficient SACs is still challenging. Herein, a gas diffusion strategy, along with one‐step thermal activation, for fabricating N‐doped porous carbon polyhedrons with trace isolated Fe atoms (Fe 1 NC) is developed. The optimized Fe 1 NC/S 1 ‐1000 with atomic Fe‐N 3 sites supported by N‐doped graphitic carbons exhibits superior CO 2 ER performance with the CO Faradaic efficiency up to 96% at −0.5 V, turnover frequency of 2225 h −1 , and outstanding stability, outperforming almost all previously reported SACs based on N‐doped carbon supported nonprecious metals. The observed excellent CO 2 ER performance is attributed to the greatly enhanced accessibility and intrinsic activity of active centers due to the increased electrochemical surface area through size modulation and the redistribution of doped N species by thermal activation. Experimental observations and theoretical calculations reveal that the Fe‐N 3 sites possess balanced adsorption energies of *COOH and *CO intermediates, facilitating CO formation. A universal gas diffusion strategy is used to exclusively yield a series of dimension‐controlled carbon‐supported SACs with single Fe atoms while a rechargeable Zn–CO 2 battery with Fe 1 NC/S 1 ‐1000 as cathode is developed to deliver a maximal power density of 0.6 mW cm −2 .