The stability of anodic oxide films on gold and the difference between their interfacial capacitance and that at the Au-metal surface

Abstract

In studies of processes at oxidized compared with unoxidized electrode surfaces by transient methods, corrections for double-layer charging are usually required and have often been made by extrapolation of double-layer capacitance (Cdl) data for the metallic surface, e.g. at Au or Pt, into the potential region of oxide-film formation. Voltammetry and impedance spectroscopy provide direct information on Cdl values determined at unoxidized, i.e. metallic, Au surfaces compared with those of anodic oxide films generated potentiostatically to various extents that are stable in time, and characterized by reductive linear-sweep voltammetry. Using Electrochemical Impedance Spectroscopy, Cdl is derived from constant-phase element (CPE) values and the CPE parameter, ϕ, which is found to be near unity for most conditions. In the second part of this thesis, the stability of the compact, so-called alpha-oxide film on gold electrodes in contact with halide solutions was investigated by means of voltammetry coupled with nanogravimetry, using an EQCN. (Abstract shortened by UMI.)