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DOE OSTI · 2454984

Local ionic transport enables selective PGM-free bipolar membrane electrode assembly

Li, Mengran·Lees, Eric W.·Ju, Wen·Subramanian, Siddhartha·Yang, Kailun·Bui, Justin C.·Iglesias van Montfort, Hugo-Pieter·Abdinejad, Maryam·Middelkoop, Joost·Strasser, Peter·Weber, Adam Z.·Bell, Alexis T.·Burdyny, Thomas
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Abstract

Bipolar membranes in electrochemical CO 2 conversion cells enable different reaction environments in the CO 2 -reduction and O 2 -evolution compartments. Under ideal conditions, water-splitting in the bipolar membrane allows for platinum-group-metal-free anode materials and high CO 2 utilizations. In practice, however, even minor unwanted ion crossover limits stability to short time periods. Here we report the vital role of managing ionic species to improve CO 2 conversion efficiency while preventing acidification of the anodic compartment. Through transport modelling, we identify that an anion-exchange ionomer in the catalyst layer improves local bicarbonate availability and increasing the proton transference number in the bipolar membranes increases CO 2 regeneration and limits K + concentration in the cathode region. Through experiments, we show that a uniform local distribution of bicarbonate ions increases the accessibility of reverted CO 2 to the catalyst surface, improving Faradaic efficiency and limiting current densities by twofold. Using these insights, we demonstrate a fully platinum-group-metal-free bipolar membrane electrode assembly CO 2 conversion system exhibiting <1% CO 2 /cation crossover rates and 80-90% CO 2 -to-CO utilization efficiency over 150 h operation at 100 mA cm -2 without anolyte replenishment.

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRYcarbon capture and storagechemical engineering

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Li, Mengran, Lees, Eric W., Ju, Wen, Subramanian, Siddhartha, Yang, Kailun, Bui, Justin C., Iglesias van Montfort, Hugo-Pieter, Abdinejad, Maryam, Middelkoop, Joost, Strasser, Peter, Weber, Adam Z., Bell, Alexis T., Burdyny, Thomas. 2024-09-19. Local ionic transport enables selective PGM-free bipolar membrane electrode assembly. https://doi.org/10.1038/s41467-024-52409-z

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