Investigation of the adsorption of phosphoric acid on platinum at elevated temperature by means of IR spectroscopy combined to electrochemical methods

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The aim of this project is the detailed understanding of the adsorption of phosphoric acid and other phosphate species on platinum surfaces at elevated temperature. These spectroelectrochemical investigations should give information about the state of the adsorbed species. That means for example the adsorption geometry or the degree of protonation at various temperatures and potentials. This information is relevant for understanding the oxygen reduction reaction at platinum catalyst on the cathode of a high temperature polymer electrolyte fuel cell. This reaction is hindered by adsorption of phosphoric acid on electrochemically active surface sites.The establishment of a method, which uses the non-destructive surface sensitive infrared reflection absorption spectroscopy for investigation of the adsorbed phosphoric acid depending on the applied potential and temperature, is planned. For this purpose a potential modulation technique, the subtractively normalized interfacial fourier transform infrared spectroscopy (SNIFTIRS), will be used for monitoring the difference between two potentials. Thus, the potential, where no adsorption of phosphoric acid is present, is used as reference, to show the differences after adsorption. Using this data will lead to a better understanding of the hindrance of the oxygen reduction reaction depending on the temperature.