Zero-Gap Electrochemical CO2 Reduction Cells: Challenges and Operational Strategies for Prevention of Salt Precipitation

Mark Sassenburg, Maria Kelly, Siddhartha Subramanian, Wilson Smith, Thomas Burdyny

Research output: Contribution to journalArticlepeer-review

59 Scopus Citations


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.

Original languageAmerican English
Pages (from-to)321-331
Number of pages11
JournalACS Energy Letters
Issue number1
StatePublished - 2023

Bibliographical note

Publisher Copyright:
© 2022 The Authors. Published by American Chemical Society.

NREL Publication Number

  • NREL/JA-5900-84612


  • CO2 reduction
  • degradation
  • electrochemistry
  • salt formation


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