SoHMuSDaSS – State-of-Health Modeling and Simulation as well as Diagnostics on Fuel Cells, Stacks and Systems

Duration: August 2015 - December 2018
Contracting Authority/ Sponsors: Federal Ministry for Economic Affairs and Energy (BMWi)
Project Partners: Bosch Engineering GmbH, Zentrum für BrennstoffzellenTechnik, Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg
Project Focus:
Labor zur in-situ-Charakterisierung von Brennstoffzellen-Komponenten.
© Fraunhofer ISE
Laboratory for in-situ characterization of fuel cell components.
Die Verluste von Stromdichte und ECSA für zwei Hersteller (schwarz und rot) und drei Katalysatorschichten zeigen den Einfluss der Elektrodenzusammensetzung auf die Alterung.
© Fraunhofer ISE
The loss of limiting current density Iloss@0.1V in relation to the loss in electrochemical surface area (ECSA) of a platinum (Pt) and platinum-cobalt (PtCo) catalyst. The lines for catalyst loadings of 0.4 and 0.25 mgPtcm-2 and two manufacturers (black and red) show the influence of the manufacturing process on the aging.
Schematische Darstellung der Degradationsprozesse in der Katalysatorschicht.
© Fraunhofer ISE
Scheme of the most relevant degradation process in the catalyst layer.

Fuel cells are complex electrochemical energy converters which are subjected to very different influences during operation. The goal of the project is the investigation of ageing effects depending on the operating strategy from the component to the system level.

Automotive fuel cells are subjected to very dynamic operation. That is why the electrochemical energy converters must be able to withstand many potential changes during lifetime which can cause severe degradation. The components undergo different ageing processes depending on the catalyst type and loading as well as the structure of the catalyst layer and operation strategy (gas supply, humidification and load point). These ageing processes were studied in great detail in dependence on the operating conditions. For this purpose, different characterization methods were used, such as polarization character curves, impedance spectroscopy, cyclic voltammetry and limit current density measurements.

The results show that differences in production and/or in material composition can have significant influence in the degradation behaviour. Graph 2 shows that the catalyst layers from two manufacturers can be clearly distinguished regarding their gas diffusion properties even though a manufacturer uses two different catalyst systems with different platinum loadings.

In addition to testing, the analysed ageing processes are modelled in order to make a statement about the durability of fuel cells depending on their operating mode. The model takes the most significant degradation effects into account, such as platinum dissolution and redeposition, platinum agglomeration, platinum oxide formation and separation due to carbon corrosion (Graph 3).