Voltage losses in zero-gap alkaline water electrolysis
| Autor: | J.W. Haverkort, H. Rajaei |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Materials science
Hydrogen Analytical chemistry Energy Engineering and Power Technology Separator (oil production) chemistry.chemical_element 02 engineering and technology Electrolyte Overpotential 010402 general chemistry 01 natural sciences Bubble Overpotential Zirfon PERL Electrical and Electronic Engineering Physical and Theoretical Chemistry Ohmic contact Concentration overpotential Hydrogen production Renewable Energy Sustainability and the Environment Alkaline water electrolysis 021001 nanoscience & nanotechnology 0104 chemical sciences Anode Zero-gap chemistry 0210 nano-technology |
| Zdroj: | Journal of Power Sources, 497 |
| ISSN: | 0378-7753 |
| DOI: | 10.1016/j.jpowsour.2021.229864 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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