Impact of Accelerated Stress Tests on High Temperature PEMFC Degradation

Accelerated stress tests (ASTs) have been used to provoke and investigate degradation mechanisms inside commercial high temperature proton exchange membrane electrode assemblies based on phosphoric acid doped polybenzimidazole (PBI). A novel load cycling test using high current densities of 0.6 and 1.0 A cm−2 has been developed and compared with a test utilizing lower current densities between 0.0 and 0.3 A cm−2. A high comparability is ensured by testing membrane electrode assemblies (MEAs) from the same supplier and batch under identical test conditions. Next to daily electrochemical characterization (polarization curves, electrochemical impedance spectroscopy, linear sweep and cyclic voltammetry), ex situ investigations including product water analysis by inductively coupled plasma mass spectrometry (ICP‐MS) and micro‐computed tomography (µ‐CT) as a powerful 3D imaging tool have been carried out. Clear demarcations of AST consequences for cell ageing have been identified. Especially, differences in platinum catalyst degradation and in loss of phosphoric acid as electrolyte over AST time have been revealed. Furthermore, influences of electrochemical characterization on MEA performance have been shown, which should be considered in future durability tests of fuel cells.