Electrochemical carbon monoxide reduction at high current density: Cell configuration matters

Electrochemical carbon monoxide reduction (COR) is an important link between the electrochemical CO2-to-CO reduction and the renewable production of C2+ chemicals. Along with the development of catalyst materials for selective and efficient COR, it is imperative to optimize electrolysis conditions and cell parameters to efficiently reduce CO at industrially relevant current density and produce concentrated product streams. This study focuses on understanding fundamental differences in reaction selectivity during COR, when the same Cu catalyst was used in three different cell configurations, namely, microfluidic, hybrid anode zero-gap, and zero-gap electrolysers. In all cases, ethylene, acetate, ethanol, and propanol formation was confirmed at industrially relevant current densities (0.5–––1.2 A cm−2) at reasonable cell voltages, albeit with subtle differences. The local chemical environment at the electrode/electrolyte interface is very different in each configuration leading to different product distribution and crossover to the anode. This stresses the importance of cell architecture and implies that comparing the catalytic activity of a catalyst studied with different cell configurations can lead to inconsistent conclusions.