Abstract
The effects of NO2 cathode exposure on the localized performance of high- and low-Pt proton exchange membrane fuel cells (PEMFCs) operated under high power generating conditions were studied and compared. Introduction of 2 ppm NO2 in the cathode feed gas caused a spatial performance distribution and voltage drop of 80 and 130 mV for high- and low-Pt samples, respectively. A full recovery of the cell voltage was observed after stopping the NO2 injection in the air stream only for high-Pt cells, while low-Pt cells had a partial recovery. The performance loss could be attributed to the dissociative adsorption of NO2 on Pt with the formation of NO and its further reduction to N2O via two consecutive electron and proton transfer steps. Cathode exposure to 2–5 ppm NO2 led to a decrease in the electrochemical area (ECA) of 17–18 and 21–23% for the high- and low-Pt samples, respectively, which exceeded the ECA loss in reference tests in pure air. The low-Pt PEMFC performance loss after poisoning by 1–2 ppm NO2 could be recovered applying cyclic voltammetry. However, poisoning by 5 ppm NO2 led to a serious decline in the spatial low-Pt PEMFC performance of 10–70 mV.
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