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Electrochemical Preparation of Functional Micro-nano Materials and the Oscillatory Electrocatalytic Oxidation of Small Bio-organic Molecules

Author: HuangZuo
Tutor: LiZeLin
School: Hunan Normal University
Course: Analytical Chemistry
Keywords: Micro / Nano Functional Nanomaterials Electrochemical preparation Bio / organic molecules Oscillating electro-catalytic oxidation Raman spectroscopy
CLC: O643.3
Type: PhD thesis
Year: 2009
Downloads: 346
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Abstract


Nano-materials due to its special structure and the resulting series of nanometer effect, determine that it has different novel properties of common materials, widely used in energy, chemical, electronics and other fields. At present, it has been able to use a variety of methods to prepare nanomaterials. Among them, electrochemical methods nanomaterials mild reaction conditions, good controllability, wide application, etc., is a promising method for preparing nanomaterials. Meanwhile, bio / electro-oxidation of small organic molecules, not only in the electrochemical desorption study, the surface of the electrochemical reaction process with basic theoretical research value, but also can promote the associated biological analysis, energy conversion and utilization and other aspects of practical application. Nanomaterials on biological / organic small molecules oscillating electro-catalytic oxidation of research, awareness and understanding of nano-materials for the electrode process, rich nonlinear dynamics, are of great scientific significance. This thesis developed a number of novel and convenient electrochemical method for the preparation of such nanoparticles, micro / nano porous metal hydroxides and nano-porous films and other functional materials, discovery and systematic study of nano-porous film electrode material on a variety of bio / organic small sub-oscillation mechanism of electro-catalytic oxidation reaction with. Main contents are as follows: 1. Systematic review of the micro / nano-materials preparation and application, bio / organic small molecules oscillating electrical and electrochemical oxidation of the relevant literature. (2) reported a blank solution in NaOH, by square wave potential pulse technique bright Au substrate surface reconstruction to easily implement multi-dimensional gradient prepared porous Au film the new method. Preparation process involves the oxidation of Au - reduction and strong hydrogen evolution reaction. Au surface oxidation - reduction produces Au nanoparticles, the hydrogen bubble dynamic template assembled under the guiding role of the porous structure. This method is convenient and green economy in the solution does not require the introduction of Au (Ⅲ) species and additives, and need to deal with a template, on the Au surface to build three-dimensional porous structure. Scanning electron microscopy (SEM) to characterize the pore formation and evolution. The three-dimensional porous Au film versatility: ① on ethanol, glucose and ascorbic acid fuel / electro-oxidation of biological molecules exhibit high electrocatalytic activity; ② three-dimensional porous Au film with a strong and stable surface enhanced Raman scattering (SERS) effect, and Raman-active and easy updates; ③ When the thiol monolayer porous membrane surface modification, by the super-hydrophilic into superhydrophobic. 3, with the hydrogen bubble template method directly electrodeposition, precious metals successfully prepared Au, Pd and AuPd alloy porous membrane. NaOH medium high hydrogen bubble stability and strength under the cathode Au (Ⅲ) reduction rate higher species, making a cross-soak method Au electrodeposition, a three-dimensional micro / nano porous structure. In HCl solution, Au, Pd or AuPd way to fill the gap electrodeposition bubbles, forming two-dimensional micro / nano porous structure. Characterized by SEM of the porous structure. X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) discloses a composition of the porous film. Electrochemical tests showed that the porous film has a high noble metal surface area, low-carbon electro-oxidation of alcohols exhibit high electrocatalytic activity. Moreover, the porous membrane surface modification with super hydrophobic mercaptan. 4 developed a use of square wave potential pulse or AC technology in NaOH blank solution dispersed pure Pt wire new electrochemical method of Pt hydrosol prepared. Potential disturbances in the process, Pt surface oxidation - reduction resulting Pt atom rearrangement to form clusters and nanoparticles in hydrogen evolution under the effect of dispersion in the base solution. Using the above strategy, the solution without any precursor ions and a reducing agent, and in mild conditions, to achieve a clean, green Pt particles, simple synthesis. Moreover, the use of two-electrode system implemented on two Pt wire paired electrolysis, which can produce Pt sol. Using SEM, TEM and XRD, Pt nanoparticles were characterized. The prepared Pt nanoparticles on the electrocatalytic oxidation of ethanol is highly active, and have a certain SERS effect. 5 prepared by cathodic electrodeposition of nano-porous Ni (OH) 2 film (NHNF). Systematic study of the porous film amino acids (α-alanine, alanine, lysine, glycine, serine, arginine) and glycylglycine oscillating electro-catalytic oxidation reaction. Time-resolved and the electric potential at the molecular level modulation Raman spectra in situ monitoring of the electro-catalytic process. Experimental results show that: ① NHNF as an effective electron mediator on the biomolecule electro-oxidation has a higher electrocatalytic activity: ② α-amino acid electro-oxidation experiences decarboxylation and amino transformed into nitrile process; ③ The electro-oxidation by diffusion transfer quality control. First observed on the biomolecules in NHNF when electro-oxidation potential and current oscillations. Periodic oscillations generated for oxygen evolution plays a key role, namely limiting diffusion controlled reactant molecules on the electrode surface oxidation induced depletion of oxygen evolution, which has generated convection to the surface concentration of agitation to restore oxygen evolution stopped, so cycle oscillation. 6 prepared in the three-dimensional porous Au film (PGF), and were modified by cathodic deposition Ni or Pt, prepared Ni / PGF or Pt / PGF modified electrode. Were investigated under alkaline Ni / PGF of the three biological molecules (ascorbic acid, glucose and glycine) and acidic under Pt / PGF oscillation for formic acid electro-catalytic oxidation process. The results show that, Ni / PGF electro-oxidation of biological molecules have higher electrocatalytic activity, electro-oxidation by diffusion mass transfer control, and for the first time found that these systems can produce electrical potential oscillations. Among them, glucose and ascorbic acid potential oscillations of small amplitude and large amplitude is divided into two kinds: the first one before oscillations appear in the oxygen evolution, mainly related to the formation of strongly adsorbed intermediates and removal related to the process for the electrochemical reaction with the surface of the coupling type; after accompanied by a periodic oscillation of oxygen evolution, mainly due to the limits of the surface concentration diffusion of oxygen consumption and analysis of surface concentration due to convection recovery, attributed to the electrochemical reaction and diffusion convective mass coupling type. Glycine electro-oxidation occurs only second oscillation. Pt / PGF electrode electrocatalytic activity of formic acid with Pt increased with decreased, mainly involved in the process of surface potential oscillations then becomes easy to occur. This is mainly due to the low amount of formic acid oxidation of Pt direct process-based, poisoning intermediate CO ad formation is inhibited, no significant negative feedback system; high amount of formic acid oxidation of Pt indirect process-based, dissociative adsorption of CO ad poisoning enhanced role of the negative feedback, and with strong positive feedback (CO ad removal) matches in a specific current range of potential oscillations generated . 7 Cross-ring cyclic voltammetry using the criterion of biological molecules observed in Pt, Ag Electrode oxidation oscillation. Wherein the cysteine ??anodic oxidation on Pt, at a lower electric potential range of oscillation occurs. Investigation and analysis of each component of the solution (cysteine, H , Cl - ) concentration on the oscillation effect. Cysteine ??via cysteine ??or cystine oxidation by free radicals free radical oxidation of cysteine ??RSO 3 - and oscillations generate probable source a pair of positive and negative feedback, ie the formation of free radicals in the platinum surface and removal. Certain concentration of Cl - helps to balance the positive and negative feedback oscillation. A variety of biological molecules (methionine, arginine, lysine, ascorbic acid and glucose) on Ag Electrode Electrochemical oxidation also appeared oscillation, and are related to the process with oxygen evolution, suggesting that the oscillation mainly from biological molecules limiting diffusion convection caused by oxidation and oxygen evolution recover. Potential oscillations and oxygen evolution process can change the silver electrode surface morphology, which in turn also have some impact on the oscillation.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic
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