A study on the effect of potentiostatically grown gold oxide films on the oxidation of phenol in base
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2001-01-01
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Abstract
The general behaviour of potentiostatically grown gold oxide films during the oxidation of phenol in basic solutions has been studied using cyclic voltammetry. No catalytic activity is observed and phenol oxidation is prevented when the oxide film consists of both α- and β-oxides. The depletion of β-oxide is accompanied by rapid electrode passivation, showing that the presence of Au(OH)3 is essential for the oxidation process to take place. A tentative reaction mechanism based on the IHOAM model of electrocatalysis is proposed to account for the participation of the redox mediator couple Au(I)/Au(III). In solutions having high concentrations of KClO4 or KCl and short reaction times chlorination occurs at gold oxide electrode films, without polymerization at temperatures lower than 308 K and 321 K respectively. Oxidation and chlorination reactions occur with apparent activation energies of ca 17 and 70 kJ mol-1 respectively : this indicates that oxidation is favoured at lower concentrations of the additives.