No description available.

A kinetic study on polycrystalline platinum (Pt) in sulphuric acid is presented. An electrochemical kinetic mechanism of Pt oxide reduction and surface oxide structures are proposed. The reduction reaction was studied by cyclic voltammetry (CV) and various potential programs that combine sweep and hold periods by an assembled analog instrumentation. The reduction peak was studied under three surface conditions: same oxide coverage θ and same potential E, different θ and same E, and same θ but different E, to determine the influence of θ and E on the peak potential and peak shape. The double-layer charge measured previously by dynamic electrochemical impedance spectroscopy (dEIS) was used to correct the CV baseline. Differential-equation-based models as a function of θ and E were investigated to simulate the oxide reduction and oxidation, and estimate kinetic parameters. A simple mechanism combining desorption and multi-layer growth mechanisms showed good fit with both the spread-out oxidation peak and the sharp reduction peak. A microscopic surface oxide growth model was proposed to explain the surface oxides reduction mechanism. / Graduate

Thesis (M. Phil.)--University of Hong Kong, 1979.

Thesis (Ph.D)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Kumar, Satish; Committee Member: Cook, Fred L.; Committee Member: Bottomley, Lawrence A.; Committee Member: Carter, William Brent; Committee Member: Yushin, Gleb. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Two objectives are achieved in this thesis: (1) to develop a new method to measure the pH-dependent net surface charge of soils and (2) to determine if, by a combination of the surface charge evaluated by potentiometric titration and ion adsorption, we can separate the permanent charge, generated by the isomorphous substitution, from the variable charge. First, a laboratory procedure, using backtitration, was developed for the measurement of the pH-dependent net surface charge. This method was tested on ten soil horizons from Gleysols and Podzols. It appears that the pH-dependent net surface charge, measured by this technique, shows good agreement with that measured by ion adsorption. It is also possible, with this method, to identify some plateaus and inflection points in the backtitration curve associated with protonation/deprotonation reactions of specific soil components. Secondly, it was demonstrated that it is possible to increase the surface charge of montmorillonite with Al-oxide coatings under specific conditions.

No description available.

No description available.

No description available.

This thesis reports the development of sonoelectrochemistry as a technique for sample analysis. Complementary modelling gives an insight into the mass transport and electrode reaction mechanisms. Separate studies were conducted as follows: - Initially an copper(II) acetate buffer system was used as its speciation can be determined. In order to establish under which conditions analysis could be conducted the effect of speciation was examined. These were applied to the Anodic Stripping Voltammetry (ASV) determination of copper in the acetate solution and to facilitate the use of a traditionally inhospitable electrochemical medium: real ale with minimal pre-treatment. Both gave detection limits of the range (1-100) μg L^-1 and in quantitative agreement with Atomic Absorption Spectroscopy. - The effect of acoustic streaming under mild insonation was studied by modelling Square Wave Voltammetry (SWV) of ASV and was found, when compared to experiment, to be the dominating factor. When the latter is strongly present two distinct mass.transport regimes were identified. Studies of chemical and electrochemical processes suggested that the acoustic streaming model fails under more extreme conditions. - SWV voltammetry was modelled for reversible electrochemical reactions leading to a refinement of existing analytical theory and the ASV modelling extended to account for surface morphology and finite electrode kinetics. Droplets on an electrode surface subjected to a potential sweep give rise to voltammetric traces attributed to charge insertion. Three mechanisms for this are proposed: (i) charge injection at the droplets surface, (ii) charge injection at the three phase boundary and (iii) the droplet is saturated with counter ions and electron transfer occurs at the electrode surface. These are solved numerically and incorporate Regular Solution Theory to account for non-ideal interactions. Comparing with experimental data an approximate model identified the processes occurring for small droplets. A Marangoni-type convection is suggested for larger droplets.

Thesis (PhD)--University of South Australia, 1995