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Studies Of Nonlinear Kinetic Behaviors In The Electrocatalytic Oxidation Of Small Organic Molecules On Nano-Structured Nickel Hydroxide Film (NNHF) Electrode

Posted on:2006-12-19Degree:MasterType:Thesis
Country:ChinaCandidate:W HuangFull Text:PDF
GTID:2121360155956899Subject:Physical chemistry
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Electrochemical oscillations, a spatiotemporal phenomenon under conditions of keeping far away from equilibrium, have been observed in a number of electrochemical processes, including electrodissolution of metals, electrodeposition of metals, electrocatalytic oxidation of small organic molecules, and so on. The profound study of electrochemical oscillations has important scientific meaning for recognizing the oscillatory phenomena, developing the kinetics of electrode processes, enriching the research content of nonlinear kinetics, and promoting the development of theory and experimental methods concerned in physical chemistry. In this work, we aim at (i) finding new electrochemical oscillators systematically by means of our cyclic-voltammetry-based criterion established recently, and (ii) studying the oscillatory mechanism at the molecular level by in situ spectroelectrochemical methods.As we all know that the study of electrocatalytic oxidation of small organic molecules is significant both for fundamental research as model systems and for potential application in the fuel cells. The study ofoscillatory mechanism is helpful in deepening the whole understanding of the electrocatalytic processes, because a complete electrocatalytic machanism should be also applicable to description of the oscillations. Oscillations on noble metals like Pt have been widely studied for about a half century. However, no reports appear in the literature up to date on oscillations with the electrode of nickel hydroxide, though this electrode is widely used in organic electrosynthesis and electroanalysis.In this thesis, several new oscillators have been found with the help of the cyclic-voltammetry-based criterion in the electrooxidation of various kinds of small organic molecules on a nano-structured nickel hydroxide film (NNHF) electrode, which was deposited on a mechanically roughed nickel disk under cathodic galvanostatic conditions. By taking current or potential scanning, we found that both current and potential oscillations can occur during the oxidation of primary alcohols or amines, while only current oscillations appear in the oxidation of secondary alcohol (isopropanol). We have compared the time series of potential oscillations at different applied currents and analyzed the cause of their difference in oscillatory behaviors for the electrooxidation of primary alcohols. A comparative study was also performed on the behavior of cyclic voltammetry and oscillations for the oxidation of methanol on a Pt electrode. It was found that, instead of surface reactions as on the Pt electrode, the rate-determining step on the NNHF electrode changed into the diffusion mass transfer, mainly due to its higher...
Keywords/Search Tags:electrochemical oscillations, cyclic voltammetry criterion, nano-structured nickel hydroxide film (NNHF) electrode, small organic molecules, in situ Raman spectroscopy, mechanism
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