Selective Electrosynthesis of Ethanol from CO 2 Enabled by High Cu I Content and Enhanced H 2 O Activation of Molecularly Modified Cu-Based Catalyst

Electrocatalytic synthesis of ethanol from CO 2 and water is a promising strategy to close the carbon cycle while producing value-added chemicals. However, highly selective production of ethanol remains an enormous challenge especially at high current density. In this work, we design a series of copper (Cu)-based catalysts by covering a layer of coordination complex on the surface of Cu 2 O to stabilize Cu I in the CO 2 electroreduction process. By tuning the coverage, the atomic percent of Cu I can be regulated from 9.7 to 83.6%, their selectivity for CO 2 electroreduction to ethanol may be improved from 6.1 to 56.8%, and a linear correlation is observed between the Cu I atomic percent and ethanol selectivity. Notably, the optimal (Cu I ) 83.6 /Cu + BTEC exhibits a C 2+ Faradaic efficiency (FE) of 87.3% with a partial current density of 676.0 mA cm –2 . In particular, the ethanol FE is 56.8%, and the partial current density is up to 439.8 mA cm –2, which is close to the record value reported previously, and the catalyst is stable in 110 h electrolysis. In situ spectroscopy techniques and DFT calculations reveal that the catalyst reduces the energy barrier of *CO atop –*COH coupling, stabilizes the selectivity-determining intermediate CH 3 CHO*, and accelerates the dissociation of water molecules into active hydrogen (*H), thus resulting in an excellent selective production of ethanol.