Enhancement of Electrospun Gas Diffusion Layers for PEMFC Using High-Resolution Imaging

Abstract

This study investigates the imaging and structural analysis of gas diffusion layers manufactured by electrospinning (eGDL). Various three-dimensional (3D) acquisition techniques, including focused ion beam scanning electron microscopy (FIB-SEM) and X-ray computed nanotomography (XCT), are employed, along with stochastic numerical generation of structures. Results show close agreement between numerical and real structures, making stochastic numerical methods of structure generation viable for eGDL studies. A dozen electrospun structures have been designed with variable microstructures and imaged using synchrotron X-ray nanotomography at the european synchrotron radiation facility (ESRF) synchrotron, providing unprecedented insights into the intricate morphology of eGDLs. Relationships between porosity, fiber size, and pore size are established, revealing counterintuitive trends: while pore size increases with fiber size, porosity peaks at around 0.95 for fibers of 500 nm. An optimal structure is found to exhibit maximal diffusion and permeability properties, improving by up to 40% for the diffusion and by an order of magnitude for the permeability. Cell testing confirms the superior performance of optimized structures in low humidity conditions (50% RH), nearing that of the tested commercial GDL. eGDLs offer competitive advantages with simpler fabrication processes compared to commercial GDLs. However, in high-humidity conditions, the tested commercial GDL outperforms despite the eGDL optimization.