A study of electrode passivation during aqueous phenol electrolysis

Journal Article · Thu Apr 01 04:00:00 EST 1993 · Journal of the Electrochemical Society; (United States)

DOI:https://doi.org/10.1149/1.2056225· OSTI ID:6538375

Gattrell, M; Kirk, D W ^[1]

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1. Univ. of Toronto, ON (Canada)

The process of electrode passivation during phenol electrolysis at a platinum electrode was studied in a sulfuric acid electrolyte (pH0-1). Passive film growth and the effects of concentration and potential were investigated using chronoamperometry, x-ray photoelectron spectroscopy, and gel permeation chromatography. The main products of the phenol oxidation are oligomers/polymers with weight-averaged molecular weights typically around 1000 g/mol after a 30 ms anodic pulse. X-ray photoelectron spectroscopy shows that the passivating polymer film is oxidized incompletely with many hydroxyl groups present. Increased potential increased the polymerization rate, but above 1.0 V vs. SCE film decomposition reactions also occurred. Increased phenol concentration increased the charge required to initiate passivation. Potential steps to the open-circuit potential or to mo9re cathodic values can interfere with the passivation process. Chronamperometric results show that the current decay at the passivated electrode is roughly inversely proportional to time and that the currents for a fixed amount of polymerization reaction follow a Tafel relationship. This t;type of decay is not due to a limitation caused b;y reactant diffusion through, nor IR drop across, a growing film but is more characteristic of electron tunneling through a growing insulating barrier layer. The model proposed for the observed behavior involves the formation of a region of high molecular weight, oxidized material at the electrode surface which blocks further reaction at the electrode. The rate-determining step at the passivated electrode is therefore electron tunneling through this unreactive material.

• OSTI ID: 6538375
• Journal Information: Journal of the Electrochemical Society; (United States), Journal Name: Journal of the Electrochemical Society; (United States) Vol. 140:4; ISSN 0013-4651; ISSN JESOAN
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400400* -- Electrochemistry
AMPEROMETRY
AROMATICS
CHEMICAL REACTIONS
CHEMISTRY
CHROMATOGRAPHY
ELECTROCHEMISTRY
ELECTRODES
ELECTROLYSIS
ELECTROLYTES
ELECTRON SPECTROSCOPY
ELEMENTS
FILMS
GEL PERMEATION CHROMATOGRAPHY
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
INORGANIC ACIDS
LYSIS
MANAGEMENT
MATHEMATICAL MODELS
METALS
ORGANIC COMPOUNDS
OXIDATION
PASSIVATION
PHENOL
PHENOLS
PHOTOELECTRON SPECTROSCOPY
PLATINUM
PLATINUM METALS
POLYMERIZATION
PROCESSING
SEPARATION PROCESSES
SPECTROSCOPY
SULFURIC ACID
TITRATION
TRANSITION ELEMENTS
WASTE MANAGEMENT
WASTE PROCESSING
X-RAY SPECTROSCOPY