Electrodeposited Cu-Sn Alloy for Electrochemical CO2 Reduction to CO/HCOO−

Cu-Sn alloy electrodes were prepared by simple electrodeposition method for the electrochemical reduction of CO 2 into CO and HCOO − . The alloy electrode surfaces provided good selectivity and efficiency in electrochemical CO 2 conversion because they provided appropriate binding energies between the metal and the reactive species obtained through CO 2 reduction. Therefore, product selectivity can be modulated by altering the Cu-Sn crystal structure of the electrode. Using the Cu-Sn alloy electrodes, electrochemical reduction was performed at applied potentials ranging from − 0.69 to − 1.09 V vs. reversible hydrogen electrode (RHE). During electrochemical CO 2 reduction, all the prepared Cu-Sn alloy electrodes showed prominent suppression of hydrogen evolution. In contrast, Cu 87 Sn 13 has high selectivity for CO formation at all the applied potentials, with maximum faradaic efficiency (FE) of 60% for CO at − 0.99 V vs. RHE. On the other hand, Cu 55 Sn 45 obtained a similar selectivity for electrodeposition of Sn, with FE of 90% at − 1.09 V vs. RHE. Surface characterization results showed that the crystal structure of Cu 87 Sn 13 comprised solid solutions that play an important role in increasing the selectivity for CO formation. Additionally, it suggests that the selectivity for HCOO − formation is affected by the surface oxidation state of Sn rather than by crystal structures like intermetallic compounds. The Cu-Sn alloy catalysts prepared by simple electrodeposition can control the selectivity for CO and HCOO − formation by tuning its crystal structure. Surface analyses revealed that solid solutions and the oxidation state of Sn play an important role in the formation of CO and HCOO − upon CO 2 reduction, respectively.