Cation transport phenomena during CO2 electroreduction in an H-type cell with a Nafion membrane

Abstract

CO₂ electroreduction (CO₂RR) was predominantly investigated in an electrocatalytic cell with anodic and cathodic chambers separated by a cation exchange membrane. Unfortunately, after long-term operation, the current inevitably decreased sharply even to zero in a static cell without refreshing electrolyte. The intrinsic reason has not been well elucidated yet, which is important for large-scale production. In the current work, two catalytic systems of CO₂RR to a gaseous product of carbon monoxide or liquid product of formate in potassium bicarbonate electrolyte in an H-type cell were selected for monitoring the cation transport effect on the electrocatalytic process. The results show that the potassium cations were transported through the membrane from the anodic side to the cathodic side, leading to a concentration increase of potassium cations in the catholyte and finally the depletion of ions in the anolyte. Finally, the significantly increased ohmic resistance of the anolyte reduced the total current, which can be recovered by adding more cations into the anolyte. This understanding offers valuable insights for optimizing the design and operation of CO₂RR, particularly in addressing the challenges associated with ions depletion during prolonged operation.