4D in situ visualization of mechanical degradation evolution in reinforced fuel cell membranes. (20th March 2020)

• Record Type: Journal Article
• Authors: Ramani, Dilip; Singh, Yadvinder; White, Robin T.; Wegener, Matthew; Orfino, Francesco P.; Dutta, Monica; Kjeang, Erik
• Is Part Of: International journal of hydrogen energy. Volume 45:Number 16(2020)
• Page Start: 10089
• Page End: 10103
• Publication Date: 2020-03-20
• Subjects: Reinforced membrane -- Fuel cell -- Fracture -- Crack -- Visualization -- X-ray computed tomography; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2020.02.013
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: Composite ionomer membranes with ePTFE reinforcement have been developed to improve operational durability of polymer electrolyte fuel cells by creating a more mechanically robust membrane electrode assembly. The present objective is to determine the morphological damage evolution of a reinforced membrane subjected to pure mechanical degradation by wet/dry cycling in a fuel cell. Identical-location four-dimensional in situ visualization by X-ray computed tomography is used to reveal the progressive degradation stages from initiation via propagation to failure. The observed degradation process is dominated by fatigue driven membrane fracture which is primarily confined under the channel area. When compared to degradation of non-reinforced membranes, the results for the reinforced membrane demonstrate similar non-linear progression of membrane fracture, but at 2-3x lower rate due to the improved fracture resistance of ePTFE reinforcement. Membrane-catalyst layer delamination and catalyst layer cracks are identified as preceding drivers of local membrane fracture, while wet and dry phase in situ imaging demonstrates hydration induced through-plane swelling of 30% and widespread crack closure at advanced degradation states. Overall, these results provide new understanding of mechanical degradation in composite membranes and prospective directions for further durability enhancements. Graphical abstract: Image 1 Highlights: 4D in situ XCT is adopted to track mechanical degradation of reinforced membranes. The in situ process of fatigue crack propagation is revealed. Degradation mechanisms of reinforced and non-reinforced membranes are compared. Catalyst layer cracks and delamination are identified as key drivers of fracture.