Selective Electrosynthesis of Ethanol from CO2 Enabled by High CuI Content and Enhanced H2O Activation of Molecularly Modified Cu-Based Catalyst.

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 CuI in the CO2 electroreduction process. By tuning the coverage, the atomic percent of CuI 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 CuI atomic percent and ethanol selectivity. Notably, the optimal (CuI)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 *COatop-*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.