Impact of air contamination by NOx on the performance of high temperature PEM fuel cells

Kurzfassung

High temperature PEM fuel cells show enhanced tolerances regarding fuel impurities like CO for use in various applications. However, the impact of air impurities like NOx on the cell behavior is not completely understood yet. This study provides systematic investigation during 500 h of operation in presence of cathode air containing 10 ppm NO or NO2. Nitrogen oxides provoke a strongly and linearly decreasing voltage of 245.3 ± 18.5 mV h^-1 and highly comparable damage that verifies similar HT-PEMFC degradation via both oxides. Cyclic voltammetry and electron microscopy reveal the loss of electrochemical catalyst surface by selectively poisoned surface and enforced catalyst particle growth. Impedance spectroscopy reveals besides increased electrode charge transfer resistances an affected proton conductivity. In contrast, SO2/NO2 impurity mixture in real occurring Ratio causes less voltage decay due to a positive SO2 impact through H2SO4 formation causing further shown and discussed effects like nitrate formation and discharge.