Mass transport modelling for the electroreduction of CO₂ on Cu nanowires

Mass transport plays an important role in CO₂ reduction electrocatalysis. Albeit being more pronounced on nanostructured electrodes, the studies of mass transport for CO₂ reduction have yet been limited to planar electrodes. We report here the development of a mass transport model for the electroreduction of CO₂ on Cu nanowire electrodes. Fed with the experimental data from electrocatalytic studies, the local concentrations of CO₂, [Formula: see text] and OH^- on the nanostructured electrodes are calculated by solving the diffusion equations with spatially distributed electrochemical reaction terms incorporated. The mass transport effects on the catalytic activity and selectivity of the Cu nanowire electrocatalysts are thus discussed by using the local pH as the descriptor. The established correlations between the electrocatalytic performance and the local pH shows that, the latter does not only determine the acid-base reaction equilibrium, but also regulates the mass transport and reaction kinetics. Based on these findings, the optimal range of local pH for CO₂ reduction is discussed in terms of a fine balance among the suppression of hydrogen evolution, improvement of C₂ product selectivity and limitation of CO₂ supply. Our work highlights the importance of understanding the mass transport effects in interpretation of CO₂ reduction electrocatalysis on high-surface-area catalysts.