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Hartwig, Carl Eric ; Tschernoster, Jan ; Hämmerle, Martin ; Hoffmann, Hendrik ; Magori, Erhard ; Wiesner-Fleischer, Kerstin ; Moos, Ralf ; Roth, Christina:
Bridging Potentiostatic Operation in H-Cells and Galvanostatic Operation in Zero-Gap Electrolyzers for Scaled-Up CO₂ Reduction Using a Two-Gap Flow Cell.
2026
Veranstaltung: GDCh Electrochemistry 2026
, 22-25 September 2026
, Bayreuth, Germany.
(Veranstaltungsbeitrag: Kongress/Konferenz/Symposium/Tagung
,
Poster
)
Abstract
Scaling up the electrochemical CO2 reduction reaction (CO2RR) from conventional H-cells (three-electrode set-up) to zero-gap electrolyzers (two-electrode set-up) typically requires a transition from potentiostatic to current-controlled operation. In this work, a two-gap flow cell (three-electrode set-up) is introduced as an intermediate platform that enables high current density operation while retaining the ability to determine the potential via a reference electrode. Potentiostatic operation reveals key limitations for stable CO2RR at elevated current densities. Increased ohmic losses and gas evolution lead to pronounced potential drops which, even under active iR-drop compensation, can induce severe current instabilities. In addition, variations in current density at constant CO2 feed flow alter the effective reaction stoichiometry (λ), significantly affecting product selectivity. Neglecting this effect under potentiostatic operation may result in misinterpretation of potential-dependent selectivity trends. Nevertheless, pulsed potential operation has shown beneficial effects in H-cells and flow cells for enhanced selectivity and stability. In this work, the transfer of such pulsed operational concepts from H-cells under potentiostatic operation to zero-gap systems under galvanostatic operation was investigated using a two-gap configuration. In pulsed potential operation, a constant working potential is periodically interrupted by a less negative regeneration pulse. Depending on the respective potential levels during this switch, an anodic current spike may occur. To replicate this behaviour under current-controlled operation, an anodic current step was introduced to reproduce the observed current spike. Using this approach, potential-pulsed operation can be translated to and studied under current- controlled condition. Overall, this study highlights the importance of current-controlled effects in CO2RR and proves the two-gap flow cell to be a versatile platform for bridging fundamental insights with practical electrolyzer operation.