UC Berkeley

Copper is uniquely active for the electrocatalytic reduction of carbon dioxide (CO₂) to products beyond carbon monoxide, such as methane (CH₄) and ethylene (C₂H₄). Therefore, understanding selectivity trends for CO₂ electrocatalysis on copper surfaces is critical for developing more efficient catalysts for CO₂ conversion to higher order products. Herein, we investigate the electrocatalytic activity of ultrathin (diameter ∼20 nm) 5-fold twinned copper nanowires (Cu NWs) for CO₂ reduction. These Cu NW catalysts were found to exhibit high CH₄ selectivity over other carbon products, reaching 55% Faradaic efficiency (FE) at -1.25 V versus reversible hydrogen electrode while other products were produced with less than 5% FE. This selectivity was found to be sensitive to morphological changes in the nanowire catalyst observed over the course of electrolysis. Wrapping the wires with graphene oxide was found to be a successful strategy for preserving both the morphology and reaction selectivity of the Cu NWs. These results suggest that product selectivity on Cu NWs is highly dependent on morphological features and that hydrocarbon selectivity can be manipulated by structural evolution or the prevention thereof.