Selenic Acid Etching Assisted Atomic Engineering for Designing Metal-Semimetal Dual Single-Atom Catalysts for Enhanced CO2 Electroreduction.

Single-atom catalysts are promising for electrocatalytic CO₂ conversion but face challenges in controllable syntheses. Herein, a facile selenic acid etching-assisted strategy has been developed to fabricate a hybrid metal-semimetal dual single-atom catalyst for electrocatalytic CO₂ reduction. This strategy enables the simultaneous generation of monodisperse active sites and hierarchical morphologies with hollow nanostructures. The as-obtained catalyst with Fe-Se dual single-atom sites supported by porous nitrogen-doped carbon (FeSe-NC) shows exceptional catalytic activity and CO selectivity, delivering a Faradaic efficiency (FE) of >97% with industrially comparable j_CO, superior to the Fe single-atom catalyst. Moreover, the FeSe-NC-based rechargeable Zn-CO₂ battery delivers a high power density (2.01 mW cm^-2) and outstanding FE_CO (>90%), as well as excellent cycling stability. Experimental results together with theoretical calculations reveal that the etching-induced defects and the Se-modulated Fe centers with asymmetrical polarized charge distributions synergistically facilitate the key intermediate *CO desorption and thus accelerate the CO₂-to-CO conversion.