Electrochemical Reduction of CO2 to Value-Added Chemicals on Zn/Cu Alloy Catalysts Prepared by Electrodeposition

Abstract

In this work, Zn/Cu alloy electrocatalysts prepared by electrodeposition of Zn on Cu foil (Zn/Cu) and electrodeposition of Zn and Cu on Cu foil (ZnCu/Cu) in different electrodeposition baths consisting of NaCl bath (Zn/Cu-Na, ZnCu/Cu-Na) and HCl bath (Zn/Cu-H, ZnCu/Cu-H) with deposition times 60 and 200 s were investigated in the electrochemical reduction of CO2 (CO2-ERC). As revealed by SEM-EDX and XRD results, the electroplating conditions affected the Zn structure being formed (dendrite or bulky). Under the conditions used, the electrochemical reduction of CO2 using these electrodes led to the formation of gaseous products including carbon monoxide and hydrogen and liquid products including formate and n-propanol as confirmed by GC and NMR, respectively. Among the catalysts studied, Zn/Cu-Na200 is the best electrocatalyst that produces high CO product with low H2 at potential -1.6 V vs. Ag/AgCl because of the high coverage of Zn particles on Cu substrate. The catalyst is stable during the 4 hour reaction time although larger dendritic Zn particles were observed after reaction, suggesting the re-depositing of Zn during CO2 ERC. Zn/Cu-H with bulky structure, on the other hand, led to formate as the outstanding product due probably to the presence of hexagonal close pack (0001) facet that promotes formate production via the reduction of HCOO* intermediate.