Insights into PEMFC Water Management with Different Layer Properties

Abstract

Hydrogen based proton-exchange-membrane fuel cells (PEMFCs) provide a sustainable, potentially decarbonized solution to meet the future energy needs for mobility applications especially heavy-duty vehicles. Water management plays a critical role in determining the performance and efficiency of PEMFCs.1 Low water content in the membrane-electrode assembly (MEA) can lead to membrane dehydration and subsequently increased ohmic overpotentials, while high water content can result in local flooding of the porous media, thereby leading to mass-transport limitations. The structure and properties of the porous media and membrane govern the water transport in the MEA and thus, parameterizing the effect of these properties on the water balance in the MEA is important for the design of next generation materials, a task that mathematical modeling is ideally suited to tackle.In this work, a 2D half-land half-channel MEA model,2 modified to explicitly include gas crossover, is used to study the effect of different layer properties on PEMFC performance. The model is used to examine both impact of membrane thickness in traditional PEMFCs, as well as water management with thicker electrodes and asymmetric diffusion media with non-platinum-group-metal PEMFCs. For the former, the tradeoffs between crossover and water gradients versus ohmic losses is quantified including explicit membrane-thickness-dependent properties.3 For the latter, specific cases of diffusion media with different pore size distributions and permeabilities is explored. Water-balance and voltage-breakdown analysis elucidate the design parameters limiting the PEMFC performance. References A. Z. Weber et al., Journal of The Electrochemical Society, 161, F1254–F1299 (2014).L. M. Pant, S. Stewart, N. Craig, and A. Z. Weber, Journal of The Electrochemical Society, 168, 074501 (2021).X. Luo et al., Journal of The Electrochemical Society, 168, 104517 (2021).