Investigation of Catalyst Degradation in Proton Exchange Membrane Fuel Cell By Identical Location Electron Microscopy

Abstract

Proton exchange membrane fuel cells (PEMFCs) suffers from issues of degradation, partly due to the harsh conditions associated with an acidic environment, varying potentials and temperature cycling. To better understand and mitigate these issues, it is necessary to study the degradation of PEMFCs under realistic conditions. In this study, identical location (IL) electron microscopy was implemented in a single cell 5 cm2 PEMFC to examine the degradation of the cathodic catalyst layer at the nanoscopic scale during an accelerated stress test used to mimic start-up/shutdown conditions. IL scanning electron microscopy revealed the formation of cracks in the catalyst layer resulting in isolated islands of the catalytic layer with lifted edges and an increase in resistance due to loss of physical contact. Additionally, IL transmission electron microscopy analysis revealed that degradation of the carbon support forced Pt particles closer together, promoting Pt particle growth together with a significant decrease of electrochemical surface area. The carbon support was also observed to collapse at weak points, creating a less porous structure. These results shed light on the degradation mechanisms of the cathodic catalyst layer during start-up/shutdown events and can help with understanding the significant decrease of electrochemical performance during these conditions. Figure 1