Mechanistic studies on boron-doped diamond: Oxidation of small organic molecules


Stefanova A., Ayata S., Erem A., Ernst S., Baltruschat H.

ELECTROCHIMICA ACTA, vol.110, pp.560-569, 2013 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 110
  • Publication Date: 2013
  • Doi Number: 10.1016/j.electacta.2013.05.104
  • Journal Name: ELECTROCHIMICA ACTA
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.560-569
  • Keywords: Boron doped diamond (BDD), Waste water treatment, Hexafluoroisopropanol (HFiP), On-line electrochemical mass spectrometry (DEMS), OH radicals, BOND-DISSOCIATION ENERGIES, HYDROXYL RADICALS, AQUEOUS-SOLUTION, ELECTROCHEMICAL OXIDATION, FLUORINATED ALCOHOLS, COUPLING REACTION, ACID OXIDATION, RATE CONSTANTS, ELECTRODE, DEMS
  • Dokuz Eylül University Affiliated: Yes

Abstract

The electro-oxidation of ethanol, acetone, i-propanol, its fluorinated analogue hexafluoroisopropanol (HFiP) and cyclohexane in 1 M HClO4 was studied on a boron doped diamond (BDD) electrode by on-line differential electrochemical mass spectrometry (DEMS), using a dual thin layer cell. One can distinguish two oxidation pathways: at potentials below 2.5 V a direct electron transfer to the BOO takes place, while at potentials above 2.5 V OH radicals are produced and scavenged by the reactants. As a consequence, the oxygen evolution reaction is at least partially suppressed. The direct electron transfer to. the electrode is observed for i-propanol, ethanol and cyclohexane. For acetone and HFiP, only the second, indirect, pathway with the participation of OH radicals is effective. For all the reactants except HFiP CO2 formation was observed generally at 2.5 V or higher, the potential for the oxygen evolution reaction (OER) in the pure supporting electrolyte. Hence OH radicals are instrumental in the cleavage of C-C bonds. For HFiP, the cyclic voltammograms of the supporting electrolyte with and without the reactant are identical. This indicates that the oxidation of HFiP is initiated by OH radicals followed by a further electron transfer to the electrode, similarly to the oxidation of CO (I. Kisacik, A. Stefanova, S. Ernst and H. Baltruschat, PCCP, 15 (2013) 4616). For both pathways, the reactivity follows the same trend as the homogeneous hydrogen abstraction reaction rates with OH radicals. The intermediate radicals formed in the reaction with the electro-generated OH radicals can react with oxygen present in the solution. (C) 2013 Elsevier Ltd. All rights reserved.