Design of an elevated pressure electrochemical flow cell for CO₂ reduction

Abstract: The electrochemical CO₂ reduction reaction (CO₂RR) has been proposed as a sustainable way of closing the carbon cycle while synthesizing useful commodity chemicals. One of the possible routes to scale up the process is the elevated pressure CO₂RR, as this increases the concentration of the poorly soluble CO₂ in aqueous systems. Yet, there are not many studies that focus on this route owing to the inherent challenges with high pressure systems. In this study, a novel high pressure flow cell setup has been designed and validated. The modular design uses a clamp system, which facilitates simple stacking of multiple cell parts while being capable of handling pressures up to 50 bar. The effects of CO₂ pressure on the reaction were investigated on a gold (Au) foil cathode in a 0.1 M KHCO₃ electrolyte. We successfully measured gaseous products produced during high pressure operation using an inline gas chromatograph. We find that the selectivity toward CO₂ reduction products is enhanced while that of H₂ evolution is suppressed as the pressure is increased from 2 to 30 bar. The reported setup provides a robust means to conduct high pressure electrolysis experiments in an easy and safe manner, making this technology more accessible to the electrochemical CO₂RR community. Graphical abstract: [Figure not available: see fulltext.].