Selective Electrosynthesis of Ethanol from CO₂ Enabled by High Cu^I Content and Enhanced H₂O Activation of Molecularly...

Electrocatalytic synthesis of ethanol from CO₂ 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 Cu₂O to stabilize Cu^I in the CO₂ electroreduction process. By tuning the coverage, the atomic percent of Cu^I can be regulated from 9.7 to 83.6%, their selectivity for CO₂ 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 C₂₊ 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 CH₃CHO*, and accelerates the dissociation of water molecules into active hydrogen (*H), thus resulting in an excellent selective production of ethanol.