Han, Zuoyan. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 75-81). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

The objective of this research was to design and evaluate an instrumental method for electroanalysis in highly resistive media. A coulostatic detector for high performance liquid chromatography was designed and constructed. Equations were developed to describe the detector's performance under regenerative and nonregenerative experimental conditions. With mobile phases of high resistance, the detector was found to respond to both electroactive and ionic electroinactive species with the magnitude of the observed signal depending on the recent history of the electrode. Thus, the elimination of iR drop by the coulostatic method does not provide a straightforward method for electroanalysis in highly resistive media. At low electrolyte concentrations, double-layer effects become prominent. A method was devised to quantitate the static double-layer effect at solid electrodes.

No description available.

The thin-layer flow-cell incorporated an array of 32 gold strip electrodes in a serial configuration opposite a platinum counter electrode. The cell body was made of Macor glass ceramic. A photolithographic procedure for etching the Macor and a simple method of applying a gold ink was devised. Resistive feedback current-to-voltage converters independently controlled the potential difference between the electrodes of the array and the common counter electrode. A microcomputer and a customized high speed data acquisition interface recorded the current response of each electrode. An expression for the faradaic response of a single electrode within a rectangular flow channel was modified to predict the behavior of the multi-electrode flow-cell. The quinone/hydroquinone redox system was used to evaluate the performance of the detector. Summing the signals from the array when all electrodes were held at the same potential improved the signal-to-noise ratio. Hydrodynamic curves were reconstructed from the currents measured at each electrode when a ramp potential profile was applied to the array.

Fluctuation in the demand for electrical power and the intermittent nature of the supply of energy from renewable sources like solar and wind have made the need for energy storage a dire necessity. Current storage technologies like batteries and supercapacitors fall short either in terms of power output or in their ability to store sufficient energy. Pseudocapacitors combine features of both and offer an alternative to stabilize the power supply. They possess high rates of charge and discharge and are capable of storing much more energy in comparison to a supercapacitor. In the quest for solutions that are economical and feasible, we have investigated Prussian Blue in aqueous electrolytes for its use as a pseudocapacitor. Two different active materials based on Prussian Blue were prepared; one that has just Prussian Blue and the other that contains a mixture of Prussian Blue and carbon nanotubes (CNTs). Four electrolytes differing in the valence of the cation were employed for the study. Cyclic voltammetry and galvanostatic charge-discharge were used to characterize the electrodes. Our experiments have shown specific capacitances of Prussian Blue electrodes in the range of 140-720 F/g and that of Prussian Blue-CNT electrodes in the range of ~52 F/g. The remarkable capacity of charge storage in Prussian Blue electrodes is attributed to its electrochemical activity ensuring surface redox and its tunnel-like structure allowing ease of entry and exit for ions like Potassium. Simple methods of synthesis have yielded specific capacitances of the order of hundreds of Farads per gram showing that Prussian Blue has promise as an electrode material for applications needing high rates of charge-discharge.

No description available.

High temperature proton conducting perovskite oxides are very attractive materials for applications in electrochemical devices, such as solid oxide fuel cells (SOFCs) and hydrogen permeation membranes. A better understanding of the hydrogen oxidation mechanism over the metal/proton conductor interface, is critical for rational design to further enhance the performances of the applications. However, kinetic studies focused on the metal/proton system are limited, compared with the intensively studied metal/oxygen ion conductor system, e.g., Ni/YSZ (yttrium stabilized zirconia, Zr₁-ₓYₓO₂-δ). This work presents an elementary kinetic model developed to assess reaction pathway of hydrogen oxidation/reduction on metal/proton conductor interface. Individual rate expressions and overall hydrogen partial pressure dependencies of current density and polarization resistance were derived in different rate limiting cases. The model is testified by tailored experiments on Pt/BaZr₀.₁Ce₀.₇Y₀.₁Yb₀.₁O₃-δ (BZCYYb) interface using pattern electrodes. Comparison of electrochemical testing and the theoretical predictions indicates the dissociation of hydrogen is the rate-limiting step (RLS), instead of charge transfer, displaying behavior different from metal/oxygen ion conductor interfaces. The kinetic model presented in this thesis is validated by high quantitative agreement with experiments under various conditions. The discovery not only contributes to the fundamental understanding of the hydrogen oxidation kinetics over metal/proton conductors, but provides insights for rational design of hydrogen oxidation catalysts in a variety of electrochemical systems.