Selective formation of C2 products from the electrochemical conversion of CO2 on CuO-derived copper electrodes comprised of nanoporous ribbon arrays

Promotion of C-C bond coupling in the electrochemical conversion of CO2 to fuels is of great scientific and practical interest. Selective formation of C-2 over the C-1 products, however, is a formidable challenge on all electrocatalysts known in literature. Here, we report the selectivity of CuO-derived porous copper nanoribbon arrays as the electrode to convert CO2 to C-2 products. The C-C bond coupling occurred at electrode potentials <-0.701 V vs. RHE. The total Faradaic efficiency towards the formation of these C-2 compounds (C2H4, C2H6 and C2H5OH) reached to similar to 40% at -0.816 V vs. RHE under ambient pressure and temperature. More importantly, at the same condition, the total Faradaic efficiency for C-1 products (CO and HCOO-) was <3%, which were major products when a Cu2O-derived Cu electrode was used. Methane was not observed, a key product on a Cu foil electrode. This increased selectivity towards the formation of C-2 chemicals, meanwhile suppressed C-1 chemicals, are attributed to the presence of surface defects and a large number of grain boundaries on the CuO-derived porous Cu nanoribbon arrays electrode. Moreover, the activation of CO2 was found to likely occur at the copper surface; while the presence of copper oxide layer reported in literature may result from the interaction between copper and water during the post analysis process. (C) 2016 Published by Elsevier B.V.