Print Email Facebook Twitter Voltage losses in zero-gap alkaline water electrolysis Title Voltage losses in zero-gap alkaline water electrolysis Author Haverkort, J.W. (TU Delft Energy Technology) Rajaei, H. (TU Delft Energy Technology) Date 2021 Abstract Reducing the gap between the electrodes and diaphragm to zero is an often adopted strategy to reduce the ohmic drop in alkaline water electrolyzers for hydrogen production. We provide a thorough account of the current–voltage relationship in such a zero-gap configuration over a wide range of electrolyte concentrations and current densities. Included are voltage components that are not often experimentally quantified like those due to bubbles, hydroxide depletion, and dissolved hydrogen and oxygen. As is commonly found for zero-gap configurations, the ohmic resistance was substantially larger than that of the separator. We find that this is because the relatively flat electrode area facing the diaphragm was not active, likely due to separator pore blockage by gas, the electrode itself, and or solid deposits. Over an e-folding time-scale of ten seconds, an additional ohmic drop was found to arise, likely due to gas bubbles in the electrode holes. For electrolyte concentrations below 0.5 M, an overpotential was observed, associated with local depletion of hydroxide at the anode. Finally, a high supersaturation of hydrogen and oxygen was found to significantly increase the equilibrium potential at elevated current densities. Most of these voltage losses are shown to be easily avoidable by introducing a small 0.2 mm gap, greatly improving the performance compared to zero-gap. Subject Alkaline water electrolysisBubble OverpotentialConcentration overpotentialZero-gapZirfon PERL To reference this document use: http://resolver.tudelft.nl/uuid:45f7f7ad-9370-493e-8bf9-87c9a2e65275 DOI https://doi.org/10.1016/j.jpowsour.2021.229864 ISSN 0378-7753 Source Journal of Power Sources, 497 Part of collection Institutional Repository Document type journal article Rights © 2021 J.W. Haverkort, H. Rajaei Files PDF 1_s2.0_S037877532100402X_main.pdf 1.51 MB Close viewer /islandora/object/uuid:45f7f7ad-9370-493e-8bf9-87c9a2e65275/datastream/OBJ/view