Summary
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. Alkaline-exchange-membrane (AEM) electrolyzers in principle offer the performance of PEM electrolyzers with earth-abundant catalysts and inexpensive cell components. Unfortunately, these electrolyzers have poor durability. We are studying and developing passivated electrode architectures for AEM electrolyzers where the OER catalysts and ionomers are physically separated with a thin-film amorphous oxide that is electrically insulating but conductive to hydroxide ions. We find that hybrid organic-inorganic HfOx passivation layers show sufficient hydroxide-ion transport to minimally affect the cell performance while substantially suppressing ionomer degradation. Related layers can be formed during operation by adding reactive inorganic species to the ionomer to build a solid-electrolyte layer during operation. By subsequently co-engineering catalyst solid-state chemistry and materials architecture along with the interphase with the ionomer electrolyte, AEMWEs that operate in electrolyte-free water at 2.0 A cm-2 near 1.8 V with voltage degradation rates of < 0.2 mV/h are possible. I will highlight the remaining challenges centered around durability and performance that must be addressed for scale-up and commercialization and how we are working to solve these through a combination of mechanistic understanding, applied device work, and industry partnerships.
Speaker
Shannon Boettcher, Professor, Departments of Chemical Engineering and Chemistry, Universty of California Berkeley
Host
Department of Chemical and Biomolecular Engineering, Penn Engineering