Temperature dependence of the COads oxidation process on Pt(111) Pt(100), and Pt(110) electrodes

The influence of temperature variation on the COads oxidative desorption at Pt(1 1 1), Pt(1 0 0), and Pt(1 1 0) electrodes in 0.5 M H2SO4 and 0.1 M HClO4 solutions is examined. A distinct shift of the COads stripping peak towards less-positive potentials is observed as the temperature is increased from 273 to 333 K. Despite the displacement of the desorption peak towards lower potentials, its current density and shape remain unaffected for the Pt(1 1 1) and Pt(1 0 0) electrodes, therefore indicating that the oxidation mechanism for the COads is not influenced by the temperature variation in this particular range. On the other hand, the morphology of the peak on the Pt(1 1 0) electrode changes significantly with the temperature, as a result of the interaction with the oxide formation. The activation energies for the oxidation processes in the two media have been evaluated through the dependence of the peak potential and the voltammetric current of the peak with the temperature. The activation energy obtained in H2SO4 is ca. 15-25 kJ mol(-1) higher than that in HClO4, highlighting the role of the anions in the oxidation process. (C) 2003 Elsevier B.V. All rights reserved.