Premonolayer oxidation

Studied. The phenomena observed were explained similarly to other noble metals by the assumption of the role of premonolayer oxidation and formation of hydrous oxides. 

Active low coordination, metastable state of the metal leads to anomalous electrochemical response in which hydrous f) oxide species (Au203 n H2O) are produced in a premonolayer oxidation. In contrast, conventional response yields a monolayer (a) oxide species (AU2O3). Since the activity of the active Au state is variable, the nature of the f oxide is also variable. Burke and Nugent [374] write about at least three forms of that oxide. 

The effect of severe thermal pretreatment of Au wire in an inert gas atmosphere [375] on the anodic behavior of gold was also considered. In some instances, premonolayer oxidation commenced at 0.25 V (SHE). 

The formation of the active surface states of gold was also found in an alkaline solution [376]. Both cathodic and thermal pretreatments were used. As a result, up to five distinct premonolayer oxidation responses in the range O-l.OV(SHE) were observed. In a separate paper, a study of gold electrodes in the metastable states in acid and base solutions was made. The active electrodes were prepared by... 

With nnactivated gold electrodes no dc redox response was evident within the double layer region in either acid or base. However, the more sensitive FT-ac technique showed evidence of premonolayer oxidation, or an active site redox transition, at ca. 0.86 V in acid and ca. 0.80 V in base. After... 

The surface may be deliberately disrupted or superactivated by severe thermal or cathodic pretreatment. Severe thermal activation [38] results in strong promotion of at least one, and probably two, premonolayer oxidation responses in the case of gold in acid at E < 0.6 V. 

Premonolayer oxidation and its role in electrocatalysis, L. D. Burke, Electrochem. Acta, 1994, 39, 1841. 

The essential features of the IHOAM theory are the suggestions that (1) premonolayer incipient hydrous oxide formation commences at noble metal surfaces at approximately the same potential as that at which thick hydrous oxide films are reduced and (2) the resulting oxyspecies function as mediators or inhibitors in many electro-catalytic processes. 

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