In-Situ Detection of Reactive Oxygen Species in PEM Fuel Cells

Preliminary results are presented in this study concerning i) the exsitu identification of reactive oxygen species (ROS) within a model Fe+2/H2O2 solution using fluorescence spectroscopy; and ii) the effect of cerium oxide particle size on its radical scavenging properties and hence on the fluoride emission rate (FER) of composite Nafion (R) /CeO2 membranes. On the degradation diagnostics front, it is demonstrated that fluorescence fiber-optic measurements can sense the ex-situ formation of hydroperoxyl (HOO*) radicals in a Fe+2/H2O2 solution through a decrease in the fluorescence intensity in the presence of the radicals. Work to extend these studies for hydroxyl radicals and to achieve in-situ estimation is ongoing. On the degradation mitigation front, it is seen that lowering the CeO2 particle size leads further reduces the FER from composite membranes by 30-50%.