A study of the oxidation of phenol at platinum and preoxidized platinum surfaces

Journal Article · Tue Jun 01 04:00:00 EDT 1993 · Journal of the Electrochemical Society; (United States)

DOI:https://doi.org/10.1149/1.2221598· OSTI ID:5983113

Gattrell, M; Kirk, D W ^[1]

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1. Univ. of Toronto, Ontario (Canada). Dept. of Chemical Engineering and Applied Chemistry

The effects of electrode surface oxide on the oxidation reactions of phenol and on Pt electrode passivation by reaction products were investigated using cyclic voltammetry and chronoamperometry. X-ray photoelectron spectrometry was used to detect changes in the nature of the passive film. Phenol reacted at both the inner and outer Helmholtz layers at platinum metal electrodes. Phenol in the inner Helmholtz layer is adsorbed irreversibly and is conductive. Its oxidation involves ring cleavage with a z[sub eff] greater than 18 eq/mol. The outer Helmholtz layer reactions are characterized by rapid simple oxidations involving minimal rearrangement of the reactant molecule. The authors postulate that the bulk of the initial current flow during phenol oxidation is due to the simple fast outer Helmholtz reactions. This initial current continues until the buildup of unreactive products blocks further outer Helmholtz reactions and the slower inner layer reactions predominate. This electrode behavior changed if the electrode was preoxidized producing a platinum oxide coating. The inner layer reactions were greatly reduced at a platinum oxide coated electrode resulting in lower passivated electrode current flow. The onset of passivation however, was delayed at the oxide coated electrode. This is attributed to a weaker adsorption of reaction products at the electrode surface requiring additional reaction to produce a stable passive film. The final resulting passive films at Pt and Pt oxide electrodes were chemically similar based on X-ray photoelectron spectrometric analysis but differed in thickness indicating that the electrode passivation is not due simply to the thickness of the passive film.

• OSTI ID: 5983113
• Journal Information: Journal of the Electrochemical Society; (United States), Journal Name: Journal of the Electrochemical Society; (United States) Vol. 140:6; ISSN 0013-4651; ISSN JESOAN
• Country of Publication: United States
• Language: English

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