Estudo experimental e teórico das interações de espécies químicas na superfície do eletrodo de diamante dopado com boro para promover a formação de espécies fortemente oxidantes
Diamond films receive special attention in electrochemistry due to their peculiar properties (low capacitive current, wide potential window in aqueous medium, rapid electron transfer kinetics in multiple redox systems, weak molecular adsorption (low passivation) and corrosion resistance) , especi...
Na minha lista:
| Autor principal: | |
|---|---|
| Outros Autores: | |
| Formato: | doctoralThesis |
| Idioma: | pt_BR |
| Publicado em: |
Brasil
|
| Assuntos: | |
| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/27735 |
| Tags: |
Adicionar Tag
Sem tags, seja o primeiro a adicionar uma tag!
|
| Resumo: | Diamond films receive special attention in electrochemistry due to their peculiar properties
(low capacitive current, wide potential window in aqueous medium, rapid electron transfer
kinetics in multiple redox systems, weak molecular adsorption (low passivation) and
corrosion resistance) , especially when the boron doped diamond surfaces were employed.
Recent studies have demonstrated that the oxidation mechanisms of organic compounds as
well as the formation of strong oxidant species are strongly influenced by the characteristics
of the conducting layer and the substrate properties of diamond anodes. The main objective of
this project is to study by experimental procedures and theoretical calculations the interactions
of different species on the surface of the BDD electrode. The calculations were performed at
theoretical levels MP2 (with the base set of aug-cc-pVTZ (ATZ)) and DFT (with the
functional ones: BHandHLYP, PBE1PBE and X3LYP) implemented in the Gaussian package
09. The solvent was described by two implicit models: PCM and SMD. The reaction of
hydrogen atom release of the oxalic acid molecule by the hydroxyl radical, the reaction
sequence reaches the relatively high energy barrier of about 0.55 eV. The overall degradation
reaction of oxalic acid is exothermic about 7 eV, which should make this a very efficient path.
The theoretical results are basically applicable to any inert electrode in which hydroxyl radical
formation and oxalic acid degradation proceed through the outer sphere mechanism without
adsorption of intermediates. The concentration of sulfate in solution is an important parameter
during the degradation of organic compounds. Solutions in low concentration allowed the
conductivity necessary for the passage of the electric current applied to promote oxidation of
oxalic acid. However, the organic compound molecules were degraded directly on the surface
of the diamond electrode by electron transfer. In addition, the production of hydroxyl radicals
was not sufficient to promote a mediated electrochemical degradation. These behaviors were
evidenced by the polarization curves and the monitoring of the formation of the RNO-●OH
adduct when the hydroxyl radicals were produced in the solution. On the other hand, when the
sulfate concentration was significantly high in the solution (1 × 10 -2 M), the degradation of
the oxalic acid occurs by oxidation mediated by the radical SO4•-. The theoretical calculations were obtained in a solvent, predominantly of water molecules, with sufficient conductivity to allow the development of electrochemical reactions on the surface. |
|---|