Mechanistic Insights into the Enhanced Activity and Stability of Agglomerated Cu Nanocrystals for the Electrochemical Reduction of Carbon Dioxide to n-Propanol

The reduction of carbon dioxide (CO2) to n-propanol (CH3CH2CH2OH) using renewable electricity is a potentially sustainable route to the production of this valuable engine fuel. In this study, we report that agglomerates of similar to 15 nm sized copper nanocrystals exhibited unprecedented catalytic activity for this electrochemical reaction in aqueous 0.1 M KHCO3. The onset potential for the formation of n-propanol was 200300 mV more positive than for an electropolished Cu surface or Cu nanoparticles. At -0.95 V (vs RHE), n-propanol was formed on the Cu nanocrystals with a high current density (j(n)_(propanol)) of -1.74 mA/cm2, which is similar to 25x larger than that found on Cu-0 nanoparticles at the same applied potential. The Cu nanocrystals were also catalytically stable for at least 6 h, and only 14% deactivation was observed after 12 h of CO, reduction. Mechanistic studies suggest that n-propanol could be formed through the CC coupling of carbon monoxide and ethylene precursors. The enhanced activity of the Cu nanocrystals toward n-propanol formation was correlated to their surface population of defect sites.