(Invited) Materials Integration, Durability, and Perspectives in Anion Exchange Membrane-Based Low Temperature Electrolysis

Abstract

As an energy carrier, hydrogen has unique advantages due to its high energy density, ability for long-term storage, and the ability to convert between chemical bonds and electricity. [1] Although hydrogen currently has a small role in energy pathways, decreasing electricity prices can allow for a significant growth opportunity. Compared to alkaline electrolysis, anion exchange membrane (AEM) systems utilize zero-gap membrane electrode assemblies that improve performance and potentially enable hydrogen compression with back pressure. Compared to proton exchange membrane (PEM) systems, the high pH of AEMs allows for non-platinum group metal (non-PGM) catalysts and component coatings (transport layers, separators) that can reduce system cost and improve long-term durability.This presentation includes on an overview of NREL efforts in AEM electrolysis, and focuses on operation choices, materials integration, and catalysis. In recent years, membrane advancements have enabled higher AEM performance, particularly in supporting electrolytes. [2] Testing has included supported and unsupported (water) feeds, and operational strategies largely depend on the intended market. Efforts have been made to investigate the role supporting electrolytes play in improving AEM performance and assess the viability of AEM as a PEM replacement through water-only feeds and dry-cathode operation. [3,4]Materials integration focuses on strategies for incorporating catalysts and ionomers that have improved water performance and allowed for short-term durability testing. [3] These efforts include coating approaches and processing conditions to rearrange catalyst layers, and detail the complications of developing protocol recommendations with component changes. In catalysis, fundamental studies have improved an understanding of materials requirements in the oxygen and hydrogen evolution reactions, and the impact of ionomer interactions on reactivity. Ab-initio simulations have provided feedback into low- and non-PGM catalyst development studies that improve device-level kinetics. Perspectives in AEM electrolysis will be discussed, and include ongoing needs for component development and durability testing, to separate and accelerate relevant degradation mechanisms.