Multi-Physics Simulation Framework of Carbon Support Corrosion during Dynamic Startup and Shutdown: Optimization and Mitigation Strategies
Authors: Randrianarizafy Bolahaga , Schott Pascal , Gerard Mathias , Bultel Yann 
Published: February 2020

The estimation and increase of the lifetime of PEM fuel cell under dynamic conditions is one of a major challenge. Increasing the durability of the fuel cell must be treated by both the development of new material and design but also by optimal strategies and management of the operating conditions of the fuel cell. The startup and shut down phase are important to optimize to reduce the carbon support corrosion [1].x

Based on previous development of a multi-physics modeling framework, combining complex transport such as multicomponent transport in porous media and electrochemistry with the use of local conditions for MEA and channel design optimization [2], two 2D multi-physics models (2D model along the channel and 2D model at the rib/channel scale) are updated. The different reactions (hydrogen oxidation reaction, oxygen reduction reaction and the oxidation of the carbon support) are written in the general form [3-4]. The linking of the two models allows to simulate the transient potentials during startup and shutdown phase in two direction (along the channel and in the section of the MEA). In particular, during the injection of hydrogen in the channel, the reverse current mechanisms that accelerate the carbon support corrosion, is directly simulated without hypothesis. The validated models provide in-silico characterization to better explain the reverse current mechanisms and the interactions between the operating conditions of the cell and the local conditions in the catalyst layer. The CO2 concentration at the outlet of the channel is used as an observer to quantify the degradation of the carbon support.

In a second step, different mitigation strategies are proposed. In particular, some strategies are studied to limit the high potential during the startup and shutdown phase (influence of the catalyst loading in the anode, external electrical resistance). Other strategies decrease the time during the reverse current mechanism (sensitivity of the hydrogen flow rate during the startup (Fig. sensitivity study of the hydrogen flow rate during startup on the cathodic potential and the CO2 production), design optimization of the rib/channel patern). These different strategies are explained and compared. An improvement of the carbon support corrosion is quantified and can be decreased by 50%.

[1] Qiang Shen, Ming Hou, Dong Liang, Zhimin Zhou, Xiaojin Li, Zhigang Shao, and Baolian Yi. Study on the processes of start-up and shutdown in proton exchange membrane fuel cells. Journal of Power Sources, 189(2):1114–1119, 2009.

[2] Bolahaga Randrianarizafy, Pascal Schott, Marion Chandesris, Mathias Gerard, and Yann Bultel. Design optimization of rib/channel patterns in a pemfc through performance heterogeneities modelling. International Journal of Hydrogen Energy, 43(18):8907 – 8926, 2018.

[3] G. Maranzana, A. Lamibrac, J. Dillet, S. Abbou, S. Didierjean, and O. Lottin. Startup (and shutdown) model for polymer electrolyte membrane fuel cells. Journal of the Electrochemical Society, 162(7):F694–F706, 2015.

[4] B. Randrianarizafy. Multi-physics modeling of startup and shutdown of a PEM fuel cell and study of the carbon support degradation: mitigation strategies and design optimization. PhD thesis, Communauté Université Grenoble Alpes, 2018.

Figure 1