Hydroxylation of Cu Sites Enhances Selectivity of Electrosynthesis of Ethanol via Tandem Reduction of CO2

Abstract

Electrochemical conversion of CO₂ into value-added multi-carbon products is highly attractive for CO₂ utilization using sustainable electricity energy. However, achieving high ethanol selectivity of copper-based catalysts remains challenging due to the competing side reactions such as ethylene formation. Herein, a novel electrocatalyst, PANI-Ag/Cu-OH is reported, comprising of polyaniline-supported silver single atoms coupled with hydroxyl-modified copper clusters. Tandem reduction of CO₂ into ethanol with a high selectivity is realized by coupling CO formation on Ag site and further reduction on hydroxylated Cu sites. The synergistic approach enables a high Faradaic efficiency of 68.9% for ethanol with a current density of −263.8 mA cm⁻² at −0.78 V versus RHE in alkaline media. CO-TPD and in situ infrared spectra studies reveal that strong CO adsorption and Cu⁺ species stabilized by hydroxyl groups are crucial for asymmetric C–C coupling and stabilization of the ethanol intermediates, leading to the enhanced ethanol selectivity.