Electrochemical reduction of CO2 on Cu doped titanium nanotubes-An insight on ethylene selectivity

Electrochemical reduction of CO2 is performed on Cu electrodeposited Ti nanotubes (Cu/TiNT). TiNT is prepared by anodization method followed by electrodeposition of Cu and the CO2 reduction achieved is compared with that of bare electrodes. The comparison between Cu/TiNT and TiNT is done based on the characterization techniques of Scanning Electron Microscopy, X-ray Diffraction, Transmission Electron Microscopy, X-ray Photoelectron Spectroscopy and UV-Diffuse Reflectance Spectroscopy. Electrochemical reduction of CO2 is carried out in an H-type cell with 0.5 M KCl electrolyte, and ethylene, methane, formic acid, CO, hydrogen along with methanol and ethanol are observed as trace products. Among the electrodes studied, maximum Faradaic efficiency (55%) is observed for Cu/TiNT compared to TiNT and bare electrodes. To understand the mechanism of CO2 reduction which produces ethylene on the surface, calculations of first principles are carried out for the Ti nanotubes with Cu deposition on the surface and the binding configurations of various intermediates are studied. The result of first principle calculation shows that the ethylene formation on the Cu deposited surface is favorable than the methane which is in line with the experimental observation.