Fig. 4: Measured cell voltage (E_cell), Faradaic efficiency for CO (FE_CO), pH of electrolyte, the rate of in situ CO₂ generation, and CO₂ utilization during 16-hours electrolysis at 100 mA cm^–2 with a bicarbonate electrolyzer with a cation exchange membrane using 3 M KHCO₃ as both anolyte and catholyte at room temperature (50 mL for each).

Over the course of the 16-hour experiment, both the anolyte and catholyte were fed to the electrolyzer from the same reservoir to facilitate the mixing of the anolyte and catholyte solutions. The stability experiment was performed at room temperature. a E_cell remains relatively stable throughout the 16-hour electrolysis, but FE_CO begins to decline after 30 min. b The pH of the electrolyte and the rate of in situ CO₂ (i-CO₂) generation remain steady during the sustained 16-hour electrolysis. c CO₂ utilization begins to decline after 30 min of electrolysis indicating that the cathode is deactivating.