Electrochemical Reduction of Carbon Dioxide on Zinc-Modified Copper Electrodes

Electrochemical reduction of carbon dioxide (CO 2 ) was performed on zinc-deposited copper (Cu/Zn) electrodes, and the faradaic efficiency of this system toward methane, ethane, and hydrogen was evaluated. Hierarchically structured Zn was electrodeposited on a Cu substrate under constant voltage in a varying bath concentration of Zn to yield low- and high-concentration deposits, represented as Cu/Zn-A and Cu/Zn-B, respectively. The prepared materials were characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. The reduction of CO 2 was performed with the Cu/Zn electrodes in an H-type cell, and the results obtained were compared with those from bare Cu and Zn electrodes, revealing that a high deposit of Zn on Cu (Cu/Zn-B) shows greater conversion efficiency than does a low Zn deposit (Cu/Zn-A) and the maximum faradaic efficiency of methane follows the order Cu/Zn-B (52%) > Cu (23%) > Zn (7%). Moreover, the efficiency of hydrogen formation is suppressed on Cu/Zn-B (8%) compared to bare Cu (68%) in the potential range studied. The results suggest that depositing Zn on Cu favors a protonation reaction, which results in higher C 1 product formation on a Cu/Zn-B electrode.