Theoretical aspects of selected electrochemical processes: Micromachining, ohmic microscopy and electrocatalysis

There are several applications necessitating a demand for new technologies for the micro fabrication of three dimensional work pieces in several fields including the semiconductor industry and microsystem technology. While lithographic processes can be used in the fabrication of electronic devices with high precision, the produced structures have low aspect ratio making them almost two dimensional. Micro Electrochemical machining with ultra-short voltage pulses (µ-EChM) is a method which allows well-defined machining of 3-dimensional structures with very high precision in the nanometer range. The primary goal of this contribution is to present a first principles theoretical model to account for the essential features of a µ-EChM process. More specifically, and in marked contrast with other work published in the literature, our strategy relies on solving the transient transport differential equations that govern transport of solution phase species in the presence of an electric field together with Poisson's equation to yield self-consistent transient potential and concentration profiles. A model that accounts for the effect of the changing geometry due to the resulting dissolution has also been presented. The overall result is a functional, predictive theoretical model that reproduces the essential features of the observed experimental results which is the high resolution and precision through the localization of the driving overpotential.;This work also provides a quantitative basis for the development of a functional ohmic microscope capable of generating in situ spatially-resolved images of heterogeneous electrode surfaces. This was done through verification of experimentally obtained potential distribution with both analytical and numerical models.;This work also proposes mechanisms to account for unique features observed in polarization curves acquired with a rotating disk electrode for the electrooxidation of hydroxylamine, NH2OH, on Au. A quantitatively predictive EEECE model is presented.;Another electrocatalytic study was also conducted and a qualitatively predictive model is proposed to investigate the electrocatalyitic activity of Hemin adsorbed on glassy carbon towards hydroxylamine.