Modelling water intrusion and oxygen diffusion in a reconstructed microporous layer of PEM fuel cells

• Published in: International journal of hydrogen energy Vol. 39; no. 30; pp. 17222 - 17230
• Main Authors: Zhang, Xiaoxian, Gao, Yuan, Ostadi, Hossein, Jiang, Kyle, Chen, Rui
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 13.10.2014; Elsevier
• Subjects: Alternative fuels. Production and utilization; Applied sciences; Dusty model; Energy; Exact sciences and technology; FIB/SEM tomography; Fuels; Hydrogen; Micro-porous layer; PEM fuel cells; Pore-scale modelling; Saturation; FIB/SEM tomography; PEM fuel cells; Micro-porous layer; Pore-scale modelling; Saturation; Dusty model; Scanning electron microscopy; Hydrogen; Modeling; Fuel cell
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2014.08.027

The hydrophobic microporous layer (MPL) in PEM fuel cell improves water management but reduces oxygen transport. We investigate these conflict impacts using nanotomography and pore-scale modelling. The binary image of a MPL is acquired using FIB/SEM tomography. The water produced at the cathode is assumed to condense in the catalyst layer (CL), and then builds up a pressure before moving into the MPL. Water distribution in the MPL is calculated from its pore geometry, and oxygen transport through it is simulated using pore-scale models considering both bulk and Knudsen diffusions. The simulated oxygen concentration and flux at all voxels are volumetrically averaged to calculate the effective diffusion coefficients. For water flow, we found that when the MPL is too hydrophobic, water is unable to move through it and must find alternative exits. For oxygen diffusion, we found that the interaction of the bulk and Knudsen diffusions at pore scale creates an extra resistance after the volumetric average, and that the conventional dusty model substantially overestimates the effective diffusion coefficient. •We acquired 3D structure of a MPL at resolutions of nanometres.•We investigated the impact of MPL hydrophobicity on liquid water movement.•We developed pore-scale models to calculate effective oxygen diffusion in the MPL.•We proved that the conventional dusty model overestimates diffusion coefficient.