Atomic‐Level Regulation of Microenvironment in In 1 Cu Single‐Atom Alloys for Selective CO 2 ‐to‐CO Electroreduction

Electrochemical CO 2 reduction offers a promising route for sustainable carbon utilization but is often limited by insufficient selectivity and competing hydrogen evolution. Herein, we report an In 1 Cu single‐atom alloy (SAA) catalyst that achieves highly selective CO 2 ‐to‐CO conversion through atomic‐level dual microenvironment engineering. Density functional theory calculations indicate that In 1 Cu SAA is the optimal catalyst, with a low energy barrier for the formation of * COOH intermediates and effective inhibition of hydrogen evolution reactions. Experimentally, the In 1 Cu SAA delivers a CO Faradaic efficiency of 97.8% at −0.7 V vs. RHE and maintains above 90% across a wide potential window from −0.4 to −0.8 V. Mechanistic investigations reveal that strong In 5 p –Cu 3 d orbital hybridization reconstructs the electronic structure to facilitate * COOH formation, whereas geometric reconfiguration alters the adsorption mode of * CO to weaken its binding and accelerate product desorption. The synergistic modulation of electronic and spatial microenvironments effectively decouples the energetics of * COOH formation and * CO desorption, thereby promoting CO production while suppressing competing reaction pathways. This work establishes a microenvironment‐engineering strategy for overcoming scaling relationship limitations in Cu‐based catalysts and provides new insights into the rational design of highly selective CO 2 reduction electrocatalysts.