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Hydrogen peroxide formation rates in a proton exchange membrane fuel cell (PEMFC) anode and cathode were estimated as a function of humidity and temperature by studying the oxygen reduction reaction (ORR) on a rotating ring disk electrode. Fuel cell conditions were replicated by depositing a film of Pt/Vulcan XC-72 catalyst onto the disk and by varying the temperature, dissolved concentration, and the acidity levels in hydrochloric acid . The acidity was correlated to ionomer water activity and hence fuel cell humidity. The formation rates showed a linear dependence on oxygen concentration and square dependence on water activity. The selectivity in ORR was independent of oxygen concentration but increased with the decrease in water activity (i.e., decreased humidity). Potential dependent activation energy for the formation reaction was estimated from data obtained at different temperatures.
Sethuraman et al. (Mon,) studied this question.