CO₂ Electroreduction to Hydrocarbons on Carbon-Supported Cu Nanoparticles

Abstract

Activities of Cu nanoparticles supported on carbon black (VC), single-wall carbon nanotubes (SWNTs), and Ketjen Black (KB) toward CO 2 electroreduction to hydrocarbons (CH 4, C 2 H 2, C 2 H 4, and C 2 H 6 ) 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 CO 2 electroreduction to hydrocarbons are compared to that of electrodeposited smooth Cu films. For all the catalysts studied, the only hydrocarbons detected by GC are CH 4 and C 2 H 4 . The Cu nanoparticles are found to be more active toward C 2 H 4 generation versus electrodeposited smooth copper films. For the supported Cu nanocatalysts, the ratio of C 2 H 4 /CH 4 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.