CO₂ Electroreduction to Hydrocarbons on Carbon-Supported Cu Nanoparticles

© 2014 American Chemical Society. Activities of Cu nanoparticles supported on carbon black (VC), single-wall carbon nanotubes (SWNTs), and Ketjen Black (KB) toward CO2 electroreduction to hydrocarbons (CH4, C2H2, C2H4, and C2H6) are evaluated using a sealed rotating disk electrode (RDE) setup coupled to a gas chromatograph (GC). Thin films of supported Cu catalysts are deposited on RDE tips following a procedure well-established in the fuel cell community. Lead (Pb) underpotential deposition (UPD) is used to determine the electrochemical surface area (ECSA) of thin films of 40 wt % Cu/VC, 20 wt % Cu/SWNT, 50 wt % Cu/KB, and commercial 20 wt % Cu/VC catalysts on glassy carbon electrodes. Faradaic efficiencies of four carbon-supported Cu catalysts toward CO2 electroreduction to hydrocarbons are compared to that of electrodeposited smooth Cu films. For all the catalysts studied, the only hydrocarbons detected by GC are CH4 and C2H4. The Cu nanoparticles are found to be more active toward C2H4 generation versus electrodeposited smooth copper films. For the supported Cu nanocatalysts, the ratio of C2H4/CH4 Faradaic efficiencies is believed to be a function of particle size, as higher ratios are observed for smaller Cu nanoparticles. This is likely due to an increase in the fraction of under-coordinated sites, such as corners, edges, and defects, as the nanoparticles become smaller.