Highlighting Charge Transfer Phenomena in Photo-catalytic Compounds Using Optical and X-ray Techniques

Rossi, Giacomo (2018) Highlighting Charge Transfer Phenomena in Photo-catalytic Compounds Using Optical and X-ray Techniques, [Dissertation thesis], Alma Mater Studiorum Università di Bologna. Dottorato di ricerca in Fisica, 30 Ciclo. DOI 10.6092/unibo/amsdottorato/8398.
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Abstract

The best way to obtain significant results in science is to combine sophisticated experimental techniques and innovative samples. The aim of this thesis is to report an operative method to be used for the characterization of charge transfer phenomena in photo-active samples. This kind of analysis is extremely important for the doped TiO2 samples analyzed. These doped systems are promising photo-catalysts for hydrogen production from water splitting and pollutants degradation. Doping is an efficient method to decrease the energy needed to trigger the excitation of the photo-catalyst, otherwise possible only in the UV range. Identifying the role of dopants when the sample is excited is a mandatory step to understand the effects of dopants on the photo-catalytic properties of the systems. Both X-ray and optical techniques were used to characterize the samples and to follow those charge transfer phenomena induced by a visible excitation. Exploiting the unique characteristics of X Ray Absorption Fine Structure (XAFS) it was possible to determine the local structure of dopants inside the TiO2 matrix. With a differential illumination High Resolution Fluorescence Detected (HERFD) XAFS experiment an atomistic description of the light-induced charge transfer phenomena in V-doped TiO2 systems was obtained. The same physical process was also indirectly highlighted using optical ultrafast transient absorption spectroscopy. With this technique the inter-band transitions triggered by a visible light excitation were followed in real time. The combination of the two kinds of techniques made possible a complete description of the role of V dopants that, injecting charge carriers, lower the energy needed to trigger the photo-generation and surface trapping of charge carriers fundamental for the photo-catalytic processes.

Abstract
Tipologia del documento
Tesi di dottorato
Autore
Rossi, Giacomo
Supervisore
Dottorato di ricerca
Ciclo
30
Coordinatore
Settore disciplinare
Settore concorsuale
Parole chiave
X-Ray Absorption Spectroscopy, XAFS, XANES, Ultrafast Transient Absorption Spectroscopy, TiO2,
URN:NBN
DOI
10.6092/unibo/amsdottorato/8398
Data di discussione
24 Aprile 2018
URI

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