Water and gas transport across the membrane in AEMFC and PEMFC
Time: Wed 2025-06-04 10.00
Location: F3 (Flodis), Lindstedtsvägen 26 & 28, Stockholm
Video link: https://kth-se.zoom.us/webinar/register/WN_YMH0Xz3TQtOn8TOpODOfeQ
Language: English
Subject area: Chemical Engineering
Doctoral student: Nikola Nikolić , Tillämpad elektrokemi
Opponent: Professor Qingfeng Li, Technical University of Denmark (DTU), Danmark
Supervisor: Professor Göran Lindbergh, Tillämpad elektrokemi; Professor Rakel Wreland Lindström, Tillämpad elektrokemi; Professor Carina Lagergren, Tillämpad elektrokemi
QC 20250512
Abstract
Efficient operation and durability of polymer electrolyte fuel cells (PEFCs) depend strongly on thermodynamic conditions and materials selection. This thesis investigates water transport, gas permeability and corrosion of carbon catalyst support under realistic operating conditions in proton exchange membrane fuel cells (PEMFCs) and anion exchange membrane fuel cells (AEMFCs).
Experiments were conducted using real-time humidity sensors, mass spectrometry, and electrochemical methods, supported with numerical modelling in COMSOL Multiphysics.
Interest in PEMFCs which operate at low temperatures (LT, <80 °C) has shifted towards intermediate temperatures (IT, 80-120 °C) for the possibility of reducing size of cooling systems. Although water accumulation was minimized at IT, increased pressure led to the opposite effect, however with performance limitations attributed to reduced oxygen partial pressure (Paper I). Hydrogen crossover was found to increase with temperature, pressure and RH, and a convective component was observed under asymmetric pressure conditions (Paper IV and V).
In AEMFCs, asymmetric inlet humidification and dynamic gas flows were effective in managing hydration. Material properties such as ionomer water uptake and GDL hydrophobicity had a minor impact on water transport but considerably affected peak power output (Paper II and III). AEMs exhibited lower gas crossover than PEMs under all conditions, particularly the reinforced second-generation membranes (Paper V).
Carbon corrosion in PEMFCs was shown to accelerate significantly with both temperature and humidity, becoming the dominant reaction above 1.1 V and almost constant at the most extreme conditions tested (120 °C and 70 % RH, Paper VI).
These findings provide new insights into optimization strategies and limitations for PEFC systems, highlighting the importance of thermodynamic control and robust materials in achieving long-term, high-performance operation.