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Electrochemically Induced Oscillations of C2H4 Oxidation Over Thin Sputtered Rh Catalyst Films
Authors:E A Baranova  A Thursfield  S Brosda  G Fóti  Ch Comninellis  C G Vayenas
Affiliation:(1) Institute of Chemical Sciences and Engineering, école Polythechnique Fédérale de Lausanne, CH-1015, Lausanne, Switzerland;(2) Department of Chemical Engineering, University of Patras, Patras, GR-26504, Greece
Abstract:The electrochemically promoted induction of self-sustained catalytic rate and potential oscillations during C2H4 oxidation was studied over sputtered Rh thin (40 nm catalyst films interfaced with ZrO2 (8 mol% Y2O3). The reaction rate oscillates simultaneously with the catalyst potential, and always in the opposite direction. The electrochemically induced oscillatory rate is typically 60 times larger than the open-circuit catalytic rate and 1000 times larger than the electrochemical rate of O2− supply to the catalyst. The phenomenon is completely reversible and only observed under anodic polarization where the rate oscillates between the values corresponding to metallic Rh and surface Rh2O3. The oscillations are caused by the electrochemically controlled backspillover of O2− to the catalyst surface and the concomitant, via repulsive lateral interactions, decomposition of surface rhodium oxide followed by surface reoxidation to Rh2O3 by gaseous O2.
Keywords:ethylene oxidation  Rh thin film catalysts  electrochemical promotion  Yttria-stabilized zirconia  oscillatory phenomena
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