Gas crossover study for improved efficiency, safety, and durability of an electrochemical direct air capture device
Date
2024
Authors
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Publisher
University of Delaware
Abstract
The increasingly adverse effects of global warming require bold and innovative solutions. The HEMCC direct air capture device of the Yan group can reduce atmospheric carbon dioxide concentrations while operating at ambient conditions fueled by a small hydrogen feed. Industrial application is currently limited due to its short operating life and a relatively high hydrogen consumption. ☐ Gas crossover is a common phenomenon in electrochemical systems that can decrease efficiency, create explosive mixtures, and degrade the membrane. It has not been examined in detail for hydroxide exchange membranes such as the PiperIon of the HEMCC. This thesis developed electrochemical testing methods to diagnose the severity of hydrogen and oxygen crossover. First, a typical 1-cell approach was tested as a baseline. Then, a novel 2-cell setup was built that separates the gas crossover from its electrochemical measurement. This approach achieved more detailed hydrogen crossover results than the current state-of-the-art 1-cell devices. The approach allowed for permeability testing at moderate temperatures and low hydrogen contents. The 2-cell setup was finally employed to evaluate the gas crossover in the shorted membrane of the HEMCC, which was found to be less permeable. The efficiency and safety consequences of gas crossover could be calculated from the obtained permeability data. ☐ It was found that gas crossover does not cause a significant fuel loss and does not pose a safety risk when the PiperIon membrane is tested in HEMCC conditions. Finally, a gas crossover durability test revealed that the lifetime of the HEMCC was not limited by gas crossover degradation. After being exposed to crossover effects for 120 h, no significant membrane or catalyst layer damage was observed. The employed permeability testing procedures could be easily modified to perform similar case studies on other electrochemical devices.
Description
Keywords
Direct air capture, Electrochemistry, Gas crossover, Hydroxide exchange membrane