Quantitative video-rate hydration imaging of Nafion proton exchange membranes with terahertz radiation

Alves De Lima, Decio and Letizia, Rosa and Degl'Innocenti, Riccardo and Dawson, Richard and Lin, Hungyen (2020) Quantitative video-rate hydration imaging of Nafion proton exchange membranes with terahertz radiation. Journal of Power Sources, 450: 227665. ISSN 0378-7753

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Abstract

Nafion membranes are considered as the industry standard electrolyte material for proton exchange membrane fuel cells. These membranes require adequate hydration in order to reach a high proton conductivity. The relatively high sensitivity of terahertz radiation to liquid water enables contrast to be observed for inspecting water presence in Nafion electrolyte membranes. Utilising a commercially available terahertz source and camera, this paper investigates the feasibility of a compact terahertz imaging system for visualising and quantifying liquid water during an ambient air desorption process for Nafion membranes of a wide range of thicknesses – NRE-212 (50 μm), N-115 (127 μm), N-117 (180 μm) and N-1110 (254 μm). We demonstrate that the terahertz imaging system is able to quantify liquid water in the 25–500 μm thickness range, estimate membrane weight change related to liquid water desorption, which correlated well against simultaneous gravimetric analysis and visualise the room temperature liquid water desorption process of a partially hydrated Nafion N-117 membrane.