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Thesis (Ph. D.)--University of Adelaide, 1985. / Includes bibliographical references.

This thesis considers the electrochemistry of platinum-iridium electrodes in both sulphate- and chloride-containing electrolytes at 20 - 25°C. Both wire electrodes of appropriate alloy compositions and titanium-substrate electrodes were employed. Polarization curves were obtained, and a technique for measuring the surface area of the electrodes was employed in order to determine the effect of potentiostatic electrolysis on the electrochemically active area. The wire alloy electrodes showed polarization behaviour in 1M NaCl; pH 2 identical to that of platinum electrodes, indicating that iridium is not effective in reducing the passivation of these electrodes even with up to 25% alloy content. The coated electrodes showed irreversible surface area losses in both sulphate and chloride electrolytes, with the latter producing significant reductions after very short polarization times. It is suggested that oxidation of the substrate leading to electrical isolation of coating plates is responsible for the area decay. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Graduation date: 1991

Includes bibliography / 1 v. (various pagings) : ill ; 31 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, 1985

Thesis (M.S.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains vii, 57 p. : ill. Includes abstract. Includes bibliographical references (p. 55-57).

The work presented in this thesis first characterises a high speed channel flow cell and then applies the system to the electro-reduction of nitromethane in aqueous solution. Potential step transient measurements are carried out with the current-time transients simulated using a model based on the absence of axial diffusion. The excellent agreement between theory and experiment confirms the proposed mass transport model and further demonstrates that the combination of current-time transients recorded using the high speed channel flow cell and numerical simulations provide a powerful tool to access homogeneous rate constants of the order 1 x 10⁶s̄¹. The high speed channel flow cell is then used in combination with a range of complementary electrochemical techniques, numerical modelling, in-situ ESR, single crystal experiments and kinetic isotope measurements to infer a mechanistic scheme for the complex electro-reduction pathway of nitromethane in aqueous solution. Platinum, gold, mercury/copper and mercury/gold electrodes are investigated enabling the most conclusive description of the reduction mechanism to date. The reaction pathway is shown to follow an ECEEE type process with the chemical step proceeding at the electrode surface. The heterogeneous rate constant, k_het, describing the chemical step is calculated for each electrode surface. For platinum in the pH range 7.0 - 9.0 this value is 0.3 ± 0.06 cm s̄¹. For mercury/copper it is 0.18 cm s̄¹, for gold/mercury it is 0.06 cm s̄¹ and for Au it is 0.095 cm s̄¹. Consideration of these values shows a surprising independence of the heterogeneous rate constant on the chemical identity of the surface with all of the values being similar to within less than an order of magnitude. The reason for the apparent paradox of the observed surface indifference of the chemical reaction step is explained by a homogeneous H transfer from the carbon to the oxygen of the nitromethane radical anion, formed form the initial electron transfer step, occurring in the layer of solution immediately adjacent to the electrode solution as shown in the scheme below. The resulting species, ^•CH2 N(OH))ˉ then undergoes a rapid irreversible adsorption to the electrode surface and subsequent transformation to the final product the hydroxylamine, CH₃NHOH. It is proposed that if the energy barrier to the adsorption of ^•CH2 N(OH))ˉ is less than that required for the H atom transfer then the reaction rate will be insensitive to the adsorption step and hence the chemical identity of the electrode. This introduces the concept of a whole new electrochemical process: the surface indifferent electrocatalytic reaction.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 60-62). Also available via the Internet.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2003. / Includes bibliographical references. Also available online.

A project report submitted to the faculty of Engineering, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 1994. / South Africa is the largest primary producer of platinum-group metals (PGMs) in the world. It is estimated that only 2.1 per cent of the 153711 kg of total sales for 1993 was beneficiated locally. Potential value added foreign exchange earnings and employment opportunities. therefore. are being forfeited. This study identifies prospective areas of development in the major sectors of application of PGMs namely: autocatalysts; chemical and allied industries; electrical and electronics sectors; jewellery and coinage fabricators. The methodology of intensity of use (IOU) is first discussed. ThIs is followed by an analysts of South Africa's production and sales of PGMs. The body of the report is an empirical study of the IOU of platinum and palladium to establish a world outlook for these metals in their applications. Finally, the more lucrative of these applications are discussed in the light of South Africa's participiltion and competitiveness in the world market. The conclusions are firstly, that the established autocatalyst industry has the best prospect for growth and expansion. Secondly, the electrical application of platinum in fuel cells has potential depending on the level of government funding and support for a R&D programme. The third finding is that the electronics and jewellery industries have development potential on condition that resistance to market entry can be overcome by reduced public policy costs. Possible violation of GATT agreements may be avoided for these applications by world free trade co-operation.