Controlling Mass Transport in Direct Carbon Dioxide Zero-Gap Electrolyzers via Cell Compression

• Published in: Meeting abstracts (Electrochemical Society) Vol. MA2024-02; no. 61; p. 4145
• Main Authors: Lee, Dong Un (Daniel), Joensen, Bjørt, Jenny, Joel, Ehlinger, Victoria Marie, Lee, Sang-Won, Abiose, Kabir, Xu, Yi, Sarkar, Amitava, Lin, Tiras Y, Hahn, Christopher, Jaramillo, Thomas F.
• Format: Journal Article
• Language: English
• Published: The Electrochemical Society, Inc 22.11.2024
• ISSN: 2151-2043; 2151-2035
• DOI: 10.1149/MA2024-02614145mtgabs

The integration of renewable energy with industrially relevant CO 2 electrolyzers provides a promising pathway to achieving sustainable fuels and chemical generation. In this work, mass transport phenomena in a zero-gap membrane-electrode-assembly (MEA) are investigated by varying the thickness of the gaskets used during cell assembly, which in turn determines the overall applied cell compression ( Figure 1a ). X-ray computed tomography characterization (XCT) shows changes in the gas diffusion electrode (GDE) thickness and porosity as a result of changing the applied cell compression. Using the experimentally measured GDE properties, a computational model of the electrolyzer is developed to study mass transport effects on the performance of the Ag catalyst for CO 2 to CO conversion. Applying high cell compression is found to decrease electrode porosity and increase liquid saturation in the cathode catalyst layer and diffusion media, thereby limiting the mass transport of CO 2 . The two MEAs assembled and tested (MEA-008 and MEA-010) with 0.008” and 0.010” thick gaskets, respectively, show CO Faradaic efficiencies that are very similar to the model results ( Figure 1b ). MEA-010, which has higher porosity and thicker GDE, outperforms MEA-008 at high current densities (>100 mA cm -2 ) due to improved mass transport. However, MEA-010 shows increased cell resistance due to the reduced compression of the conductive fibers, resulting in higher operating cell voltages, highlighting the important trade-off between product selectivity and the voltage required to run the electrolyzer. Figure 1