(Digital Presentation) Interfacial Durability of Anion Exchange Membrane Water Electrolyzers (AEMWEs)

Abstract

There is a growing industrial appeal of anion exchange membrane water electrolyzers (AEMWEs) to produce hydrogen. This is spurred by the recent advancements in high current density operation capability with relatively low overvoltage performance. Cost reduction has been pursued by reducing the reliance on expensive platinum group metal (PGM) catalysts while still achieving long-term, continuous operation conditions most relevant to the industry: high current densities above 2 A/cm2 while retaining overvoltage performance so that overall cell potential is less than 2V.Along with a selection of appropriate PGM-free catalysts, other approaches exist that drive down the associated cost to produce hydrogen from water splitting. Sources of water are extended to brackish and even seawater to further drive down costs due to the removal of costly water purification requirements. The introduction of salt to the water source may improve overvoltage performance in an AEMWE by raising electrolyte conductivity, however, it may also lead to some unknown instability within more severe high current operating conditions. The challenge remains that AEMWE durability testing is not standardized, and more minute interfacial degradation mechanisms between ionomer, catalyst, membrane, and electrolyte are not well characterized for many industrially relevant materials. When approaching AEMWE performance improvements with PGM-free and variable electrolyte content in water solution sources, the long-term performance needs to be demonstrated in a stable and reliable manner.A series of in-situ Raman experiments are presented in coordination with ex-situ spectroscopic and physical analysis of components in PGM-free AEMWEs that are expected to contribute to overall degradation of electrolyzer performance. Interfacial durability improvements are sought by providing insight into the main sources of failure during high current and long-term operations. Electrochemical testing protocols are also developed and presented in order to seek standardization of testing procedures. In-line gas chromatography (GC) analysis is also presented in tandem with other analytical methods to confirm product gas purity and corroborate hypotheses on possible degradation mechanisms.