Atomic-Level Regulation of Microenvironment in In₁Cu Single-Atom Alloys for Selective CO₂-to-CO Electroreduction

Electrochemical CO₂ reduction offers a promising route for sustainable carbon utilization but is often limited by insufficient selectivity and competing hydrogen evolution. Herein, we report an In₁Cu single-atom alloy (SAA) catalyst that achieves highly selective CO₂-to-CO conversion through atomic-level dual microenvironment engineering. Density functional theory calculations indicate that In₁Cu 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 In₁Cu 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 5p-Cu 3d 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 CO₂ reduction electrocatalysts.