Dissociative electrochemical analysis of materials degradation of an anion exchange membrane electrolyser

Abstract

For anion exchange membrane (AEM) electrolysers, degradation studies provide valuable insights into how individual components degrade. Often, this presents a formidable challenge as each component significantly contributes to overall degradation. Here, we propose a methodology to individually compare the degradation of key components in AEM electrolysers: hydrogen evolution reaction (HER) catalyst, oxygen evolution reaction (OER) catalyst, and the AEM itself. First, to measure the degradation of catalyst-coated substrates (CCS) commonly used in AEM electrolysers, the AEM was replaced with a diaphragm (Zirfon Agfa UTP 500) permeable to OH？ ions and stable in alkaline media. Subsequently, a cell with a stable catalytic layer (Nafion-coated Ni-felt substrates) was assembled to focus on membrane degradation with an AEM Sustainion X37-50 Grade 60. Chronopotentiometry and electrochemical impedance spectroscopy (EIS) revealed that the cell with the AEM experienced a threefold increase in ohmic resistance, attributed to the loss of functional groups. Additionally, an ion exchange capacity (IEC) analysis indicated that Sustainion lost approximately 20% of its ion exchange capacity. In contrast, the cell composed of CCS and Zirfon showed lower degradation. EIS data fitting demonstrated increased kinetic-related resistances while the ohmic resistance remained unchanged. This work presents a practical approach for comparing component degradation in AEM electrolysers.