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.