Advanced Bipolar Membranes: Design Principles and Applications in Electrochemical Technology (Webinar)

The abstract below and accompanying presentation were written and presented by Prof. Shannon Boettcher of the Department of Chemistry and Biochemistry and the Materials Science Institute (Oregon Center for Electrochemistry).

This webinar was the first in the Blue Box Series hosted by BioLogic USA. The second part of this webinar series (An Investigation of Structure-Electrochemistry Relationships in Novel Silicon Anodes for Lithium-ion Batteries by Candace K. Chan, Ph.D.) can be viewed by clicking here 

Advanced Bipolar Membranes: Design Principles and Applications in Electrochemical Technology

Bipolar membranes (BPMs) consist of an anion-selective ionomer membrane laminated with a cation-selective ionomer membrane. They have applications across electrochemical technology. BPMs generate pH gradients under an applied bias by driving water dissociation (WD) into protons and hydroxide at the interface between the two different ionomers. In BPM water electrolysis, this feature enables devices that operate proton reduction in locally acidic conditions where the kinetics are fast and water oxidation in locally basic conditions where efficient earth-abundant catalysts are stable. In electrodialysis, BPMs can be used to economically generate acid and base from brine on demand, which is critical for many industrial processes including water treatment. Alkaline solutions generated by BPM electrodialysis can further be used in CO₂ capture schemes from the air or ocean. As the predominant H⁺/OH^– ion flow is out from the center of the BPM, their use in CO₂ electrolysis devices mitigates unwanted cross-over of reactants or products.

I will present progress in designing advanced BPMs with a focus on understanding and optimizing the WD catalyst integrated between the anion- and cation-selective layers. We systematically studied ~40 metal and metal oxide nanoparticle interlayers and discovered that the local pH is a critical, but previously unrecognized, variable affecting WD kinetics. Combining WD catalysts efficient in acidic and basic conditions into catalyst bilayers nearly eliminates the WD overpotential in BPM water electrolyzers operating at 20 mA cm^-2 and enables BPM operation at 0.5 A cm^-2 with a total applied electrolysis potential of ~ 2 V. By thinning the cation-selective ionomer layer, water transport to the BPM junction is improved, leading to current densities > 3 A cm^-2. These values are substantial improvements over the state of the art and have the potential to lower operating costs (due to higher BPM voltage efficiency) and capital cost (due to higher current density) of the applications introduced above.

¹Oener, S. Z.; Foster, M. J.; Boettcher, S. W., Accelerating water dissociation in bipolar membranes and for electrocatalysis. Science 2020, DOI: 10.1126/science.aaz1487

Biography: 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 is a 2019 and 2020 ISI highly cited researcher (top 0.1% over the past decade). In 2019 he founded the Oregon Center for Electrochemistry and the nation’s first graduate program in Electrochemical Technology.

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