The photocatalytic behavior of an extended series of NH4F-doped TiO2 photocatalysts (D series) has been recently investigated in both thermodynamically down-hill reactions, such as the degradation of formic and acetic acid in aqueous suspension and the gas phase mineralization of acetaldehyde, and in a thermodynamically up-hill reaction for solar fuels production, i.e. hydrogen production from methanol–water vapor mixtures. Focusing in particular into the possible activation of these doped materials under visible light, the photocatalytic oxidation of acetic acid was also investigated as a function of the irradiation wavelength, by collecting so-called action spectra. A comparison between the shapes of these latter and those of the absorption spectra of the investigated photocatalysts allowed us to clearly distinguish between inactive light absorption and effective photoactivity. In order to clarify the wavelength-dependent effects produced by nitrogen and/or fluorine on the UV-vis photoactivity of these materials, we investigated three series of doped TiO2 photocatalysts, prepared by sol-gel synthesis either employing HF as dopant source, or co-doped with boron and fluorine, or with boron only. Both the dopant amount and the calcination temperature (500 - 700 °C) were varied within each series. A detailed comparison between the photoefficiency in acetic acid decomposition as a function of the irradiation wavelength with the absorption spectra of doped materials demonstrates that fluorine, and not nitrogen, is responsible for the photoactivity increase in the UVA region observed with doped TiO2 calcined at high temperature. Besides by well established characterization tools (XRPD, BET, XPS, DR analyses), a systematic analysis of the doped materials has been performed by time-resolved photoluminescence spectroscopy in the picosecond range, to get more information about the effects that doping TiO2 with p-block has on the dynamical properties of the charge carries photogenerated on the semiconductors’ surface, in comparison with their photocatalytic activity. Results indicating a correlation between the relaxation dynamics of the photo-emission properties and the photocatalytic activity of the TiO2-based materials will be presented.

TiO2 doped with p-block elements: photocatalytic activity vs. time-resolved photo-luminescence / M.V. Dozzi, C. D'Andrea, G. Valentini, E. Selli. ((Intervento presentato al 41. convegno Congresso Nazionale di Chimica Fisica tenutosi a Alessandria nel 2013.

TiO2 doped with p-block elements: photocatalytic activity vs. time-resolved photo-luminescence

M.V. Dozzi
Primo
;
E. Selli
Ultimo
2013

Abstract

The photocatalytic behavior of an extended series of NH4F-doped TiO2 photocatalysts (D series) has been recently investigated in both thermodynamically down-hill reactions, such as the degradation of formic and acetic acid in aqueous suspension and the gas phase mineralization of acetaldehyde, and in a thermodynamically up-hill reaction for solar fuels production, i.e. hydrogen production from methanol–water vapor mixtures. Focusing in particular into the possible activation of these doped materials under visible light, the photocatalytic oxidation of acetic acid was also investigated as a function of the irradiation wavelength, by collecting so-called action spectra. A comparison between the shapes of these latter and those of the absorption spectra of the investigated photocatalysts allowed us to clearly distinguish between inactive light absorption and effective photoactivity. In order to clarify the wavelength-dependent effects produced by nitrogen and/or fluorine on the UV-vis photoactivity of these materials, we investigated three series of doped TiO2 photocatalysts, prepared by sol-gel synthesis either employing HF as dopant source, or co-doped with boron and fluorine, or with boron only. Both the dopant amount and the calcination temperature (500 - 700 °C) were varied within each series. A detailed comparison between the photoefficiency in acetic acid decomposition as a function of the irradiation wavelength with the absorption spectra of doped materials demonstrates that fluorine, and not nitrogen, is responsible for the photoactivity increase in the UVA region observed with doped TiO2 calcined at high temperature. Besides by well established characterization tools (XRPD, BET, XPS, DR analyses), a systematic analysis of the doped materials has been performed by time-resolved photoluminescence spectroscopy in the picosecond range, to get more information about the effects that doping TiO2 with p-block has on the dynamical properties of the charge carries photogenerated on the semiconductors’ surface, in comparison with their photocatalytic activity. Results indicating a correlation between the relaxation dynamics of the photo-emission properties and the photocatalytic activity of the TiO2-based materials will be presented.
giu-2013
Settore CHIM/02 - Chimica Fisica
TiO2 doped with p-block elements: photocatalytic activity vs. time-resolved photo-luminescence / M.V. Dozzi, C. D'Andrea, G. Valentini, E. Selli. ((Intervento presentato al 41. convegno Congresso Nazionale di Chimica Fisica tenutosi a Alessandria nel 2013.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/221862
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