Effect of Hierarchical Pores on the Water Transport in Microporous Layer of Proton Exchange Membrane Fuel Cells

Proton-exchange membrane fuel cells (PEMFCs) are promising energy conversion devices. The design and development of microporous layers (MPLs) is essential to the improvement of water management in PEMFCs. In this study, a two-dimensional (2D) MPL model with hierarchical pores is built, and transient two-phase and steady-state single-phase models are used to simulate the water transport process in the MPL. The influence of the number of macropores and mesopores in the MPL on the water transport is investigated. The numerical modeling results reveal that there is an optimum number of mesopores at which the water transport is promoted in the MPL. Mesopores help connect the macropores, facilitating water transport and water removal from the MPL. An excessive number of mesopores is found to be detrimental to the water removal process, resulting in flooding. A MPL with a macropore-to-mesopore ratio of 1:1 could efficiently improve the water management in PEMFCs. This contribution provides an insight into enhancing water management of MPLs and improving PEMFC performance.