title: Preparation by high-energy milling, characterization, and catalytic properties of nanocrystalline TiO2.
abstract: Titanium dioxide (TiO2) is widely used for applications in heterogeneous photocatalysis. We prepared nanocrystalline powders of the anatase as well as the rutile modification by high-energy ball milling of the coarse grained source materials for up to 4 h. The resulting average grain size was about 20 nm. The morphology of the powders was investigated with transmission electron microscopy, X-ray powder diffraction, and BET surface area determination. Measurements of the catalytic activity reveal a maximum as a function of the milling time at about 40 min. This maximum could be explained by a superposition of two counteracting effects. The first one is the increase of the specific surface area resulting in an increase of the catalytic activity, and the second one is a change of the electronic structure at the surface of the TiO2 particles corresponding to a reduction of the surface. The latter one was confirmed by light absorption experiments, X-ray photoelectron spectroscopy, and electron paramagnetic resonance spectroscopy.
authors.affiliation: Institut für Physikalische Chemie und Elektrochemie, Universität Hannover, Callinstrasse 3-3A, 30167 Hannover, Germany. indris@pci.uni-hannover.de
authors.forename: Sylvio
authors.initials: S
authors.lastname: Indris
authors.forename: Roger
authors.initials: R
authors.lastname: Amade
authors.forename: Paul
authors.initials: P
authors.lastname: Heitjans
authors.forename: Mina
authors.initials: M
authors.lastname: Finger
authors.forename: Andreas
authors.initials: A
authors.lastname: Haeger
authors.forename: Diethard
authors.initials: D
authors.lastname: Hesse
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Grünert
authors.forename: Alexander
authors.initials: A
authors.lastname: Börger
authors.forename: Klaus Dieter
authors.initials: KD
authors.lastname: Becker