Electrolyte Effects in Membrane-Electrode-Assembly CO Electrolysis

Membrane-electrode-assembly (MEA)-based CO electrolysis (COE) has demonstrated the capability to produce C₂₊ products with high faradaic efficiency at ampere-level current densities. However, most studies on COE have achieved performance benchmarks under strongly alkaline conditions (e.g., ≥1 m KOH, pH ≥14), raising the question of whether such high pH levels are essential for optimal performance. In this study, we investigated the effects of different electrolytes (KHCO₃, K₂CO₃, and KOH) on MEA-based CO electrolysis, focusing on the influence of pH and the impact of anodic oxidation on the selectivity of various liquid products. By adjusting electrolyte concentration and pH, we achieved significant partial current densities for ethanol (189 ± 5 mA cm^-2) and propanol (89 ± 4 mA cm^-2) using 0.5 M K₂CO₃. This high performance is attributed to the creation of a moderate local alkaline environment and the relatively high resistance to anodic oxidation. Additionally, durability measurements emphasized the critical importance of eliminating anodic oxidation to optimize MEA-based COE for ethanol and propanol production.