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A Comparative Study of the Redox Processes of Iodide Ion on Pt, C and Carbon-Polyorthoaminophenol

Safar Kolachaee, Leila | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40016 (03)
  4. University: Sharif University of Technology
  5. Department: chemistry science
  6. Advisor(s): Gobal, Feridon
  7. Abstract:
  8. In this study a systematic effort was made to study and compare electrochemical oxidation behavior of iodide on Pt, carbon and carbon supported polyorthoaminophenol film electrodes. All of the electrochemical experiments were performed in acidic, basic and nuteral aqueous solutions and the applied electrochemical techniques included Chronoamperometry (CA) and Cyclic voltammetry (CV). Effects of concentration and scan rate of potential on the cyclic voltammetry of KI was studied at the previously mentioned electrodes. Current-time and log current-potential curves were analyezed quantitavely in order to determine kinetic parameters. Carbon supported polyorthoaminophenol electrode was prepared through anodic oxidation of 0.1 M monomer solution in sulfuric acid media onto carbon electrode by cycling the potential between -0.2V/SCE to 0.9V/SCE. Electrooxidation of iodide showed a quasiriversible behavior on all the three electrodes. During the anodic oxidation of iodide, the iodine film was formed on the mentioned electrodes surfaces in electroactive form. Experiments showed that iodine was adsorbed more strongly on carbon electrode than the other two ones. Charecterization of the electrodeposition process of iodide was based on quantitative analysis of the potentiostatic current-time curves recorded during deposition. Nucleation and growth rate constants obtained from the fit of the recorded transients to the generalized equations were derived based on Abyaneh and Fleishmann model. It was found that the deposition process for iodide could be well described by a model that involves four contributions: (1) a double layer charging process (I_DL), (2) an instantaneous two-dimensional nucleation and growth (I_2DI), (3) a progressive two-dimensional nucleation and growth (I_2DP) and (4) a progressive three-dimensional nucleation and growth (I_3DP). The suggested mechanism for iodide oxidation on the mentioned electrodes was investigated using chronoamperometry and cyclic voltammetry which is described as:
    1) I^- (aq)→I(ads)+e^-, 2)I(ads)+ I^- (aq)→I_2 (ads)+e^-,
    3) I_2 (ads)+I^-→I_3^- (aq).

  9. Keywords:
  10. Nucleation ; Growth ; Electro-Oxidation ; Orthoaminophenol

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