MULTIFUNCTIONAL NANOSTRUCTURED MATERIALS FOR THE DEVELOPMENT OF ELECTROCHEMICAL TECHNOLOGIES FOR THE ENERGY AND THE ENVIRONMENT
Tesi di Dottorato
Data di Pubblicazione:
2014
Citazione:
MULTIFUNCTIONAL NANOSTRUCTURED MATERIALS FOR THE DEVELOPMENT OF ELECTROCHEMICAL TECHNOLOGIES FOR THE ENERGY AND THE ENVIRONMENT / O.c.m. Lugaresi ; tutor: S. Rondinini ; co-tutor: A. Vertova ; coordinatore: D. Roberto. DIPARTIMENTO DI CHIMICA, 2014 Jan 13. 26. ciclo, Anno Accademico 2013. [10.13130/lugaresi-ottavio-carlo-maria_phd2014-01-13].
Abstract:
The environmental protection / remediation and the rational use of energy resources are fundamental topics for the balanced development of civil and industrial activities. In this context, the electrochemical technologies can offer many solutions: from accumulation / generation of energy to the design / implementation of processes with low environmental impact and reduced energy consumption.
Core of a large part of the modern electrochemical systems are nanostructured multifunctional materials; In this context the PhD Thesis is focused on to the development of these materials: their electrocatalytic and functional properties can be modulated through an appropriate design, synthesis and application to the wide areas of green chemistry and energy conversion
The Thesis work was articulated into two main parts, dedicated to silver-based and iridium-based materials, respectively.
Silver-based nanostructured materials have been developed for environmental applications. The challenge represented by the degradation of organic halides (in the various soil, liquid and gaseous environments) have been highlighted and discussed and the electrocatalytic properties of silver as a cathode material for the dehalogenation of several classes of organic halides has been studied. In this work the research interests focus on the preparation methodologies of the Ag-electrode material, both to improve the catalyst performance and reduce the silver content. There is evidence that nano-structured particles exhibit better behaviour than massive silver while allowing a substantial reduction of Ag loading. As for the experimental conditions, the characterization of all prepared materials has been conducted both in aqueous and in organic media. The tests in aqueous media was conducted using a Cavity MicroElectrode (C-ME): this particular electrode is an innovative tool for the study of finely dispersed materials to be adopted in several electrochemical systems. The C-ME allows to (i) minimize the ohmic drop effect thanks to the micrometric size and therefore to the low associated current intensities; (ii) rule out both the contribution of a gluing agent on the electrochemical response and (iii) any contribution from the current collector, i.e. the micro-disk at the base of the cavity, since its surface area is negligible in comparison with the one of the hosted material. For the tests performed in aqueous media, tri-chloromethane was chosen as model substrate used. Analogously, benzylchloride (BzCl) was chosen for the tests in organic media, and specifically in acetonitrile (ACN). The particular attention for BzCl reduction is due to the recent new proposal for the reaction pathway that implies the interaction between the catalytic surface and the organic moieties of the substrate and the reaction intermediates is crucial and explains the extraordinary activity of Ag. Different strategies were adopted for the Ag-nanoparticle syntheses: (i) a polymer-mediated polyol process, that allows for the preparation of silver nanostructures with a number of different well-controlled morphologies (e.g., cubes, rods, wires, and spheres); (ii) the electrochemical synthesis, a facile route that leads to particles of controlled size by the easy adjusting of the current density; (iii) wet synthesis, a chemical reduction from aqueous solutions, this is an effective method for obtaining nano-sized powders and colloidal dispersion of silver. It is common knowledge that the chemical reduction method involves reduction of metal salt in the presence of a suitable protecting agent (organic stabilizer), which is necessary for controlling the growth of metal colloid. The fully characterised Ag-NP’s were supported on carbon matrices and used for the electrochemical dehalogenat
Tipologia IRIS:
Tesi di dottorato
Keywords:
multifunctional nanostructured materials ; silver ; nanoparticles ; FEXRAV ; cavity micro electrodes ; carbon matrix support
Elenco autori:
O.C.M. Lugaresi
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