In-Situ X-ray Absorption Spectroscopy Elucidating Mechanisms in HT-PEM Fuel Cells
X-ray absorption spectroscopy (XAS) is a technique optimally suited to in-situ studies, as neither UHV conditions, nor long-range order in the sample are required. It can be applied to monitor the geometric structure of the catalytically active nanoparticles directly following particle oxidation and growth during operation. With the delta µ XANES method and complementary theoretical FEFF8 calculations  it is possible to identify different adsorbates on small Pt nanoparticles and follow their change in coverage. Phosphoric acid , which is used as electrolyte, or impurities in the fuel gases may strongly adsorb and alter the reaction mechanisms.
In this work the coverage of different adsorbates and possible poisons on the anode and cathode side in H3PO4 imbibed PBI HT PEM fuel cells was investigated. At the cathode side, the adsorption of phosphoric acid and OH on the Pt surface was followed at different temperatures and potentials. At the fuel cell anode, the effect of CO and water was analysed.
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