September 15, 2021.
Alkaline and bipolar membrane electrolyzers: A route to scalable energy storage and conversion?
Professor in the Department of Chemistry and Biochemistry, University of Oregon
Wednesday September 15, 2021, 2:00-3:00 pm MT
Commercialized membrane electrolyzers use acidic proton exchange membranes (PEMs). These systems offer high performance but require the use of expensive precious-metal catalysts such as IrO2 and Pt that are nominally stable under the locally acidic conditions of the ionomer. I will present our efforts to study and develop alternative electrolysis platforms.
First, I will discuss alkaline-exchange-membrane (AEM) electrolyzers that, in principle, offer the performance of commercialized proton-exchange-membrane electrolyzers with the ability to use earth-abundant catalysts and inexpensive bipolar plate materials. I will present our fundamental work in understanding earth-abundant water-oxidation catalysts as well as progress in building high-performance AEM electrolyzers. To date, our best systems operate at 1 A·cm-2 in pure water feed at < 1.9 V at a moderate temperature of 69 °C. These devices, however, degrade rapidly (~ 1 mV/h) compared to PEM electrolyzers. I will show how we assess chemical changes to the anode and cathode catalyst and ionomer that is correlated with this performance loss, as well as present strategies to mitigate degradation.
Second, I will introduce the use of bipolar membranes (BPMs) in electrolysis devices. BPMs consist of an AEM and PEM laminated together. Under the appropriate bias, they conduct ionic current by dissociating water into protons and hydroxide at the AEM/CEM junction. Commercially, BPMs are used in electrodialysis, but generally are limited to low current densities below 100 mA cm-2 to avoid large losses in driving water dissociation. I will present our fundamental studies on how to accelerate water dissociation in BPMs (Science, 2020) and how that has enabled BPMs operating at > 3 A cm-2 and with improved efficiency. BPMs limit crossover and enable operation of a cathode and anode in different pH conditions and are thus seeing substantial interest for CO2 electrolysis, advanced electrodialysis systems, and water electrolysis.
Boettcher is a Professor in the Department of Chemistry and Biochemistry at the University of Oregon. His research is at the intersection of materials science and electrochemistry, with a focus on fundamental aspects of energy conversion and storage. He has been named a DuPont Young Professor, a Cottrell Scholar, a Sloan Fellow, and a Camille-Dreyfus Teacher-Scholar. He was included as an ISI highly cited researcher (top 0.1% over past decade) over the past two years. In 2019, he founded the Oregon Center for Electrochemistry and in 2020 launched the nation’s first targeted graduate program in electrochemical technology.