Quantification on degradation mechanisms of polymer electrolyte membrane fuel cell catalyst layers during accelerated stress test

Abstract:Long term durability of the catalyst layers of a low working temperature fuel cell such as polymer electrolyte membrane fuel cell (PEMFC) is of significant scientific interest owing to their operation criteria and... [ view full abstract ]

Abstract:

Long term durability of the catalyst layers of a low working temperature fuel cell such as polymer electrolyte membrane fuel cell (PEMFC) is of significant scientific interest owing to their operation criteria and high initial cost. Identification of degradation mechanisms quantitatively during an accelerated stress test (AST) is essential to assess and improve the durability of such catalyst layers. In this study, we present a quantitative analysis of the degradation mechanisms such as (i) electronic connectivity loss due to carbon support corrosion, (ii) proton connectivity loss due to ionomer/catalyst interface loss, (iii) catalyst loss due to dissolution or detachment, and (iv) physical surface area loss due to particle growth responsible for the electrochemical surface area (ESA) loss in Pt-based catalyst layers for PEMFCs. Using a half membrane electrode assembly (half-MEA), where a gas diffusion electrode with genuine three-phase-boundaries is used as working electrode through solid electrolyte, we have observed the ESA loss due to ionomer/catalyst interface loss and identified catalyst heterogeneous degradation pattern during AST. Results suggest a significant ESA loss due to catalyst isolation from loss of electron and proton connectivities respectively by catalyst support corrosion and ionomer/catalyst interface loss (Fig. 1). Such knowledge and methodology can effectively contribute to catalyst material screening and electrode structure development to advance the PEMFC technology.

Figure caption:

Fig. 1: Contributions to ESA loss due to different mechanisms as obtained by AST through half-MEA setup