Isomerization‐Guided Trace Sulfur Doping Enables Selective CO ₂ ‐to‐Ethanol Conversion

Directing the CO 2 reduction reaction (CO 2 RR) toward ethanol offers a promising route to sustainable liquid fuels. However, achieving high ethanol selectivity under industrially relevant current densities still remains a major challenge. Here, we introduce trace sulfur doping via thiourea isomerization, which enables precise sulfur incorporation to weakly bind bridge‐adsorbed OH species, thereby suppressing OH − adsorption on active sites and preventing their attack on defect sites. In situ Raman spectroscopy further reveals that suppressed OH − adsorption promotes the exposure of undercoordinated Cu active sites, enabling robust *CO atop‐binding configurations to be sustained, particularly under strongly cathodic current densities. Additionally, the tailored surface microenvironment boosts *CO dimerization kinetics, and its synergistic interplay with *OH modulation channels the reaction pathway toward ethanol generation. Consequently, the catalyst delivers a current density of −0.9 A cm −2 with a Faradaic efficiency of nearly 79.6% for C 2+ products, including 40% toward ethanol. This work highlights trace heteroatom‐driven surface reconstruction as an effective strategy to engineer catalytic CO 2 utilization.