Abstract
AbstractThe behavior of proton exchange membrane fuel cells (PEMFCs) strongly depends on the operational temperatures. In mobile applications, for instance in fuel cell electric vehicles, PEMFC stacks are often subjected to temperatures as low as −20 °C, especially during cold start periods, and to temperatures up to 120 °C during regular operation. Therefore, it is important to understand the impact of temperature on the performance and degradation of hydrogen fuel cells to ensure a stable system operation. To get a comprehensive understanding of the temperature effects in PEMFCs, this manuscript addresses and summarizes in‐ situ and ex‐ situ investigations of fuel cells operated at different temperatures. Initially, different measurement techniques for thermal monitoring are presented. Afterwards, the temperature effects related to the degradation and performance of main membrane electrode assembly components, namely gas diffusion layers, proton exchange membranes and catalyst layers, are analyzed.
Highlights
The behavior of proton exchange membrane fuel cells (PEMFCs) strongly depends on the operational temperatures
We mainly focus on the low temperature hydrogen fuel cells, where special emphasis is put on the behavior of membrane electrode assembly (MEA) components, namely the gas diffusion layer (GDL), the anode and cathode catalyst layers (ACL and CCL, respectively) and the proton exchange membrane (PEM)
We reviewed the impact of temperature on the performance and durability of PEMFCs
Summary
The local temperature of a PEMFC has an effect on parameters such as current density and reaction kinetics, kinetics of degradation processes, water drag, back diffusion and proton conductivity of the membrane.[10]. An alternative to aforementioned methods is the insertion of thermocouples between the different layers and interfaces of the fuel cell, in order to measure local temperatures This technique is capable of measuring the temperature distributions along the flow field channel direction, as well as perpendicular to the membrane. Accuracies of 5 % of water partial pressure and 2 K for temperature measurements are recorded in literature.[32] The laser beam is directed into the gas phase of two flow field channels of the cathode Results using this technique show a more homogeneous relative humidity along the flow field when the overall cell temperature is increased. ETIS can achieve high temperature resolutions in the range of 5 to 20 μK (1000 s measurement time), compared to 20 mK using thermal imaging and 200 mK using optical sensors.[23,19,33]
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