Analysis of proton exchange membrane fuel cells operated at Intermediate temperatures (IT: 80—120 °C)
Time: Tue 2025-05-27 10.00
Location: F3 (Flodis), Lindstedtsvägen 26 & 28, Stockholm
Video link: https://kth-se.zoom.us/webinar/register/WN_nbT8YAdmQje5AfqVN9hAYw
Language: English
Subject area: Chemical Engineering
Doctoral student: Martina Butori , Tillämpad elektrokemi
Opponent: Professor Erik Kjeang, Simon Fraser University, Kanada
Supervisor: Professor Rakel Wreland Lindström, Tillämpad elektrokemi; Professor Carina Lagergren, Tillämpad elektrokemi; Professor Göran Lindbergh, Tillämpad elektrokemi
QC 20250505
Abstract
Fuel cells convert energy stored in hydrogen into electricity. As a zero-emission technology, they represent a sustainable alternative to conventional combustion engines, particularly for heavy-duty vehicles. Proton exchange membrane fuel cells (PEMFCs) are used in vehicles and typically operate up to 80 °C. To facilitate the cooling of PEMFCs, slightly rising the operating temperature to the range of 80-120 °C, defined as intermediate temperature (IT), would be desirable.
The aim of the thesis is to electrochemically analyze the impact of IT operation on commercially available PEMFC materials. Results show that increasing the temperature has multiple effects on the cell. Increased ionic conductivity, faster reaction kinetics and reduced mass transport resistance are counteracted by a negative shift of the equilibrium potential, enhanced corrosion of the carbon support, and reduced gas barrier properties. Additionally, if the humidity and the cell pressure are constant, the partial pressure of oxygen is reduced at higher temperature, which limits the cell performance. Finally, a higher temperature leads to faster degradation. The ultimate failure is attributed to the formation of pinholes in the membrane, but the polymer conductivity and the catalyst's electrochemical surface area are also negatively affected.
Despite a scarcity of comparable data above 80 °C, the main obstacle for IT-PEMFCs is apparently the lack of stable materials. Current state-of-the-art polymers for PEMFCs are based on perfluorosulfonic acid (PFSA), whose sustainability has recently been questioned. Alternatively, fluorine-free hydrocarbon-based polymers investigated here show comparable results up to 100°C, but cannot tolerate operation at 120 °C. More research is needed to further develop sustainable materials and to allow continuous operation of PEMFCs in the intermediate temperature range.