Unsaturated Copper Sites for Selective Electroreduction of CO to Alcohol.

Electrochemical reduction reaction of carbon monoxide (CORR) has been extensively studied due to its high selectivity for producing multi-carbon (C2+) products. However, the selective production of alcohol-an highly valuable class of chemical feedstock-remains unsatisfactory, hindered by poor selectivity and low energy efficiency. Here, we report that low coordination (unsaturated) Cu sites generated through the reduction of Cu2O catalysts with ammonia increases the binding energy of CO and enable the pre-protonation of *CO to *CHO, as opposed to CO-CO coupling. This modification enables a shift from symmetric *CO-*CO post-protonation coupling to asymmetric *CO-*CHO coupling, thereby promoting alcohol formation. The Faradaic efficiency for alcohol production reaches up to 64.5% (51.5% for ethanol and 13% for 1-propanol) at 500 mA cm-2, with a full-cell alcohol energy efficiency of ∼27.1% and over 120 h of stable operation in a membrane electrode assembly. In situ spectroscopy and theory calculation reveal the preferential formation of key intermediates (*CHO, *COCHO, and *OC2H5) along the alcohol production pathway on the unsaturated Cu sites. This strategy of tuning intermediate pre-protonation offers a promising direction for catalyst design aimed at converting carbon emissions into value-added products.