Mass transfer effects in CO2 reduction on Cu nanowire electrocatalysts

Abstract

Significant interest has 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 a systematic investigation of CO₂ electroreduction on highly dense Cu nanowires, with the focus placed on practically relevant 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 CO₂ conversion rate calculated from the experimental data and the surface concentration of CO₂ on the nanowires derived from transport modeling, 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.