Micro-Electrode with Fast Mass Transport for Enhancing Selectivity of Carbonaceous Products in Electrochemical CO₂ Reduction

During electrochemical carbon dioxide (CO₂) reduction on copper electrodes in an aqueous electrolyte, one of the key challenges is the competition between hydrogen evolution and CO₂ reduction, especially under large current density. Here, micro-electrodes are designed with a copper wire as the substrate, which shows improved mass transport compared to the planar electrode. The Faradaic efficiency for C₂₊ products reaches 79% with a partial geometric current density −77.7 mA cm⁻² on Cu₂O nanowire/micro-electrode, which is 3.7 times higher than Cu₂O nanowire/planar-electrode. The authors also designed CuO and metallic Cu with micro-electrode as substrate and observed enhanced selectivity for carbonaceous products, proving the universality of the concept. The improved activity is attributed to the fast mass transport of CO₂ to the catalytic interface and thus the suppression of hydrogen production.