Alkaline and bipolar membrane electrolyzers: A route to scalable energy storage and conversion?

events hall

Prof. Shannon W. Boettcher

18.11.2021

Auditorium, Meidan, for green pass holders, or via ZOOM

14:30

Commercialized membrane electrolyzers use acidic proton exchange membranes (PEMs). These offer high performance but require precious metal catalysts (IrO2 and Pt) that are stable under acidic conditions. We are studying alternative electrolysis platforms. First, I will discuss alkaline-exchange-membrane (AEM) electrolyzers that in principle offer the performance of PEM electrolyzers with the new ability to use earth-abundant and inexpensive catalysts and cell materials. I will present fundamental work in understanding earth-abundant water-oxidation catalysts and progress in building AEM electrolyzers. Our best systems operate at 1 A·cm-2 in pure water feed at < 1.85 V at a moderate temperature of ~70 °C. These devices, however, degrade too fast (~ 1 mV/h). I will discuss the chemical changes to the anode and cathode catalyst and ionomer that are correlated with this performance loss and strategies to mitigate degradation towards commercialization. Second, I will discuss bipolar membranes (BPM) electrolyzers. BPMs consist of a laminated AEM and PEM and can conduct ionic current by dissociating water into protons and hydroxide at the AEM/CEM junction. BPMs are used industrially in electrodialysis but are limited ~100 mA cm-2 due to large overpotentials for dissociating water. Our studies show how to accelerate water dissociation (Science, 2020) and enable BPMs at > 3 A cm-2 and with improved efficiency. BPMs also limit crossover and enable operation of a cathode and anode in different pH, and are thus useful for CO2 electrolysis, electrodialysis, and water electrolysis.

Host: Assoc Prof. Maytal Caspary-Toroker

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