Detection of OH Radicals Generated in Polymer Electrolyte Membranes of Fuel Cells

OH radicals formed during the PEFC operation of a single cell were detected by means of a fluorescence probe method with coumarin. The coumarin molecules impregnated in the polymer electrolyte membrane react with OH radicals to form a highly fluorescent product, umbelliferone. After PEFC operation under various conditions, the cross section of the membrane for five positions was monitored by a fluorescence microscope and the distribution of the OH radical density in the membrane was evaluated. The difference among the radical densities at the five positions was large for each membrane. The observations suggest that the cross-leak of oxygen gas is a main process of the OH radical formation. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3556103]