From Potentiostatic to Galvanostatic Control in Pulsed Electrochemical CO 2 Reduction to Ethylene

ABSTRACT In order to scale electrochemical CO 2 reduction (CO 2 R) from H‐cells to zero‐gap electrolyzers in an industrial setting, the focus must shift from potential‐ to current‐controlled operation. This work studies a two‐gap flow cell in three‐electrode configuration as an intermediate platform that enables high current densities while retaining potential control, using the ethylene‐selective CO 2 R on copper electrodes as a model reaction. Key limitations of potentiostatic operation are identified, including ohmic losses, gas evolution, and resulting instabilities that alter reaction stoichiometry and thus affect selectivity. Galvanostatic operation mitigates these instabilities and provides more robust and reproducible performance. Pulsed electrolysis protocols, which are traditionally operated under potential control, favor C 2 H 4 as a product. To mimic such potentiostatic regeneration pulses in a current‐controlled protocol, we transferred them to a charge‐controlled scheme by implementing additional anodic current steps. This strategy enables the study of pulsed operation under realistic, industrially relevant conditions and demonstrates the versatility of the two‐gap cell bridging the gap between fundamental mechanistic studies and practical zero‐gap electrolyzer applications.