Zero-Gap Electrochemical CO2Reduction Cells
Challenges and Operational Strategies for Prevention of Salt Precipitation
Mark Sassenburg (TU Delft - ChemE/Materials for Energy Conversion and Storage)
Maria Kelly (University of Colorado, National Renewable Energy Laboratory)
S.S. Subramanian (TU Delft - ChemE/Materials for Energy Conversion and Storage)
Wilson Smith (TU Delft - ChemE/Materials for Energy Conversion and Storage, National Renewable Energy Laboratory, University of Colorado)
Tom Burdyny (TU Delft - ChemE/Materials for Energy Conversion and Storage)
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Abstract
Salt precipitation is a problem in electrochemical CO2 reduction electrolyzers that limits their long-term durability and industrial applicability by reducing the active area, causing flooding and hindering gas transport. Salt crystals form when hydroxide generation from electrochemical reactions interacts homogeneously with CO2 to generate substantial quantities of carbonate. In the presence of sufficient electrolyte cations, the solubility limits of these species are reached, resulting in "salting out"conditions in cathode compartments. Detrimental salt precipitation is regularly observed in zero-gap membrane electrode assemblies, especially when operated at high current densities. This Perspective briefly discusses the mechanisms for salt formation, and recently reported strategies for preventing or reversing salt formation in zero-gap CO2 reduction membrane electrode assemblies. We link these approaches to the solubility limit of potassium carbonate within the electrolyzer and describe how each strategy separately manipulates water, potassium, and carbonate concentrations to prevent (or mitigate) salt formation.
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