Within the range of voltages, the side bicarbonate reaction competes with CO2RR due to the rising local pH (Fig. ). As availability of CO2 is key to production of hydrocarbons on Cu electrodes, their current density is significantly affected. High concentration of bicarbonate ion recorded in this work (Fig. ) is a result of the assumption of flooded agglomerates and the low surface area, which hinders efficient transport of CO2 to reaction sites and observed low current densities of the GDE. Therefore, even though the catalytic surface area is lower which should have increased the availability of surface CO2, the rising pH enables the parasitic bicarbonate reaction ultimately producing bicarbonates.