Concentration Optimization of Localized Cu0 and Cu+ on Cu-Based Electrodes for Improving Electrochemical Generation of Ethanol from Carbon Dioxide

Abstract

Copper-based electrodes can catalyze electroreduction of CO2 to two-carbon products. However, obtaining a specific product with high efficiency depends on the oxidation state of Cu for the Cu-based materials. In this study, Cu-based electrodes were prepared on fluorinated tin oxide (FTO) using the one-step electrodeposition method. These electrodes were used as efficient electrocatalysts for CO2 reduction to ethanol. The concentration ratio of Cu0 and Cu+ on the electrodes was precisely modulated by adding monoethanolamine (MEA). The results of spectroscopic characterization showed that the concentration ratio of localized Cu+ and Cu0 (Cu+/Cu0) on the Cu-based electrodes was controlled from 1.24/1 to 1.54/1 by regulating the amount of MEA. It was found that the electrode exhibited the best electrochemical efficiency and ethanol production in the CO2 reduction reaction at the optimal concentration ratio Cu+/Cu0 of 1.42/1. The maximum faradaic efficiencies of ethanol and C2 were 48% and 77%, respectively, at the potential of −0.6 V vs. a reversible hydrogen electrode (RHE). Furthermore, the optimal concentration ratio of Cu+/Cu0 achieved the balance between Cu+ and Cu0 with the most favorable free energy for the formation of *CO intermediate. The stable existence of the *CO intermediate significantly contributed to the formation of the C–C bond for ethanol production.

Recent Progress and Perspective of the Electrochemical Conversion of Carbon Dioxide to Alcohols

“…(a) Faradaic efficiency vs year and (b) partial current density vs faradaic efficiency for the electrochemical CO 2 reduction to alcohols: methanol, − ethanol, − and n -propanol. − …”