Correlative X-ray Tomographic Imaging of Catalyst Layer Degradation in Fuel Cells. Issue 13 (12th August 2019)

• Record Type: Journal Article
• Authors: White, Robin T.; Ramani, Dilip; Eberhardt, Sebastian; Najm, Marina; Orfino, Francesco P.; Dutta, Monica; Kjeang, Erik
• Is Part Of: Journal of the Electrochemical Society. Volume 166:Issue 13(2019)
• Page Start: F914
• Page End: F925
• Publication Date: 2019-08-12
• Subjects: Fuel Cells - PEM -- catalyst layer -- fuel cell -- X-ray computed tomography; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.0121913jes
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : Effective catalyst layer design is vital for high-performing polymer electrolyte fuel cells. However, the desired catalyst layer structure may be compromised by operational degradation, causing performance decay. The present work investigates the multi-scale catalyst layer structure and properties across different stages of degradation, including liquid water distribution in an operating fuel cell. A correlative, multi-scale imaging workflow with a combined analysis by operando lab-based micro-X-ray computed tomography (XCT) and nano-XCT is developed for this purpose. From operando XCT results, the catalyst layer solid area fraction was found to gradually decrease by 25% with crack formation and severe localized corrosion accompanied by up to 50% thinning and significantly altered liquid water distribution. Localized degradation features such as nano-scale cracks and internal pore-size distribution changes were resolved using nano-XCT and tracked by 3+1D imaging at different stages of degradation. Porosity changes quantified by nano-XCT on the order of 40% from beginning-of-life to end-of-life with reduction in connected pore fraction were observed as well as increase in average pore size by 50%. The effect of changes at the nano-scale on diffusion properties were calculated and an empirical model is proposed for degraded catalyst layer structures where Knudsen effects are dominant.