Ethanol is a highly desirable product of the electrochemical reduction of CO and/or CO2 on copper. Although ethanol and ethylene share common intermediates at the early stages of CO/CO2 reduction to C-2 species on copper, the pathways bifurcate and most copper surfaces favor the formation of ethylene. We present here a combined experimental-computational study of the electroreduction of acetaldehyde to ethanol on Cu(1 11), Cu(1 0 0) and Cu(3 2 2). The experiments show structure-sensitive onset potentials for acetaldehyde reduction such that lower overpotentials are observed for more open facets (eta(322)< eta 1(00) < eta(111)). Our DFT calculations show that the electrochemical reduction of acetaldehyde proceeds via a CH3CH2O* intermediate on the three electrodes at high *H coverage, and that the stability of this weakly bound intermediate determines the onset potential. Our results suggest that during the late stages of CO/CO2 reduction to C-2 species on copper, ethanol formation has higher energetic barriers than ethylene formation, and hence the selectivity is inclined toward the latter. Importantly, our results suggest that the barriers for ethanol formation can be lowered by making use of its structure sensitivity. (C) 2015 Elsevier B.V. All rights reserved.