Local Impact of Humidification on Degradation in Polymer Electrolyte Fuel Cells

Kurzfassung

Water management represents one of the main challenges in the design and operation of Polymer Electrolyte Fuel Cells (PEFCs). Besides performance, the water level also affects the durability of the cell. Understanding the degradation processes is of vital importance for extending durability of PEFCs by suitable mitigation strategies. In this work, the degradation processes related to operation with fully- and non-humidified gas streams were locally studied. The differences were analyzed using in-situ diagnostic tools, such as segmented cell for local current density measurements, during a 300 h test operating under constant conditions, in combination with local post-test analysis, i.e. SEM/EDX and XPS. The results showed the deep impact of the RH on homogeneity during the degradation process due to the fact that different water distribution influences the chemical environment. Under non-humidified gas streams, the cathode inlet region exhibited increased degradation, whereas with fully humidified gases the bottom of the cell had the higher performance losses. The degradation and the degree of reversibility produced by Pt dissolution, PTFE defluorination, and contaminants such as silicon (Si) and nickel (Ni) were locally evaluated