Electrode Degradation in Proton Exchange Membrane Fuel Cells

Doctoral thesis, 2025

To mitigate the climate crisis and reduce carbon emissions from sectors such as transport and energy, hydrogen has been proposed to be used as an environmentally friendly alternative energy carrier. Proton exchange membrane fuel cells (PEMFCs), which are well suited as power sources for several types of vehicles, use hydrogen as a fuel to create electricity with the only by-products being water and heat. However, for successful commercialisation of PEMFCs, some aspects need to be improved. Lifetime, in particular, is a limiting factor due to harsh operation conditions. To improve lifetime, the mechanisms by which the materials in PEMFCs degrade must first be better understood. In this thesis, I investigate the behaviour and degradation of platinum (Pt) thin films and Pt/carbon-based PEMFC electrodes under various conditions in both half-cell setups and single-cell PEMFCs. Part of the work concerns the behaviour of Pt thin films in acidic and alkaline environments studied using electrochemical quartz crystal microbalance (EQCM) to measure the mass changes of Pt during electrochemical cycling and assess dissolution rates. Additionally, I present three studies on the feasibility of implementing identical location (IL) electron microscopy to follow cathode catalyst degradation under different operating conditions. These studies demonstrate how IL electron microscopy can be used to distinguish between various types of degradation phenomena during realistic operation conditions, opening up new possibilities for further research on the behaviour of catalyst layers during application relevant conditions. Finally, I present a study on the degradation of membrane electrode assemblies (MEAs) during voltage cycling at intermediate temperatures up to 120 °C. This study investigates how elevated temperatures impact the ageing of catalyst layers, motivated by the increasing demand for PEMFC applications that require a broader operational temperature range. Together, these studies explore different aspects of catalyst degradation, introduce new methods for tracking degradation under application-relevant conditions, and enhance our understanding of the performance of current state-of-the-art catalyst materials under new operational conditions.