Scale-up of electrochemical flow cell towards industrial CO₂ reduction to potassium formate

The CO2 electroreduction reaction (CO2RR) presents a pathway to decarbonize the manufacturing industry by using clean electricity and CO2 as feedstocks instead of relying on fossil fuels. Although known for over 100 years, this technology has yet only been developed at bench-top scale (1-100 cm(2)). In this manuscript, we report CO2 electroreduction to potassium formate (HCOOK) in a stack of two 1526-cm(2) three-compartments electrochemical cells with gas diffusion electrode (GDE) cathodes. In this stack, we achieved over 60 % current selectivity towards HCOOK at current densities of 200 mA cm(-2) and under cell voltages of similar to 4.0 V. We reached these performance metrics by tuning electrolyte composition and cell architecture. We also show that a minimum of +10-14 kPa of pressure difference must be applied between gaseous and catholyte compartments to enable the CO2RR to take place. We emphasize the challenges associated with scaling-up a CO2 electrochemical cell, specifically by demonstrating that optimal operation parameters are strongly correlated to cell architecture. This study demonstrates the feasibility of developing CO2RR electrochemical cells to an industrial scale.