Temperature dependent formation of multiple adsorption states from ethene at polycrystalline Pt and Pt(111) electrodes studied by differential electrochemical mass spectrometry

The effect of temperature (between 0 and 50 °C) on the adsorption of ethene on a Pt(111) and polycrystalline electrode has been studied by differential electrochemical mass spectrometry (DEMS). The amount of the adsorbate which is hydrogenatively desorbed at low potentials (presumably π or di-σ bound ethene) decreases with increasing adsorption temperature. Contrary to the adsorption in UHV, where the amount of ethylidine increases at a higher temperature at the expense of the associatively (π or di-σ) bound ethene, at the Pt electrode surface, higher temperatures lead to a larger amount of an oxygen containing species formed by simultaneous addition of water and oxidation. The transformation into the oxygen containing adsorbate is also achieved during subsequent heating up to 50 °C after adsorption at 0 °C. The position of the oxidation peaks, but not their relative size, is solely determined by the temperature during oxidation.