(79e) Mass Transfer Effects in CO2 Reduction Electrocatalysis

Significant interests have risen in the development of catalytic nanomaterials for the electroreduction of CO₂. While extensive studies have been reported on tuning of surface structures to improve the chemical kinetics, less attention has been paid to the mass transfer effects in the CO₂ reduction reaction on nanoscale electrocatalysts. We report here an systematic investigation of CO₂ electroreduction on highly dense Cu nanowires, with the focus placed on practical high-flux conditions. Mass transfer effects are found to play an important role in this case, giving rise to diffusion-limited CO₂ reduction activity and selectivity. By correlating the observed transport phenomena to the calculated CO₂ consumption rate and simulated surface concentration of chemical species (including local pH) on the nanowires, an upper limit is revealed for the CO₂ conversion rate on the nanostructured electrodes, which also causes the drop in Faradaic efficiency of CO₂ reduction at large current densities. Our work emphasizes the necessity of considering mass transfer effects in the design of advanced electrocatalysts for CO₂ reduction as well as for understanding their structure-performance relationships.