Photocatalytic activity and charge carrier dynamics of TiO2 powders with a binary particle size distribution

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Sieland, F.; Schneider, J.; Bahnemann, D.W.: Photocatalytic activity and charge carrier dynamics of TiO2 powders with a binary particle size distribution. In: Physical Chemistry Chemical Physics 20 (2018), Nr. 12, S. 8119-8132. DOI: https://doi.org/10.1039/c8cp00398j

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Abstract: 
The effects of the particle size distribution on the charge carrier dynamics and the photocatalytic activity of mixed titanium dioxide (TiO2) powder samples were investigated in this work. Instead of the synthesis of the small semiconductor particles, the binary particle size distributions of the powders were obtained by mixing commercially available TiO2 powders with different particle sizes. The pure anatase samples (average diameters: 7, 20, and 125 nm, respectively) were created via ultrasound treatment and discreet drying. The photocatalytic activity of the powder samples was assessed by the degradation of nitric oxide (NO) and acetaldehyde in the gas phase. Furthermore, the charge carrier kinetics was determined using transient absorption spectroscopy following pulsed laser excitation. Importantly, a recently published model based on fractal dimensions was used to fit the transient signals of the photo generated charge carriers in the TiO2 powder samples. The effects of the particle size on the acetaldehyde degradation could be explained by the formation of agglomerates, which reduce the available surface area of smaller particles. The fast oxidation of acetaldehyde on the surface of TiO2 by direct hole transfer was further independent of the observed charge carrier lifetimes on the microsecond time scale. The photocatalytic NO degradation, on the other hand, increased for samples containing larger amounts of small particles. The corresponding photonic efficiencies correlated well with the charge carrier lifetimes determined by the time-resolved studies. Hence, it was concluded that a long charge carrier lifetime generally leads to higher fractional conversions of NO. The employed fractal fit function was proved to be beneficial for the kinetic analysis of charge carrier recombination in TiO2, in direct comparison with a second order fit function. © 2018 the Owner Societies.
License of this version: CC BY-NC 3.0 Unported
Document Type: article
Publishing status: publishedVersion
Issue Date: 2018
Appears in Collections:Naturwissenschaftliche Fakultät

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pos. country downloads
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1 image of flag of Germany Germany 73 79.35%
2 image of flag of United States United States 8 8.70%
3 image of flag of Korea, Republic of Korea, Republic of 2 2.17%
4 image of flag of France France 2 2.17%
5 image of flag of Spain Spain 2 2.17%
6 image of flag of South Africa South Africa 1 1.09%
7 image of flag of Lithuania Lithuania 1 1.09%
8 image of flag of Hungary Hungary 1 1.09%
9 image of flag of Czech Republic Czech Republic 1 1.09%
10 image of flag of China China 1 1.09%

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