Ozone Activation on TiO2 Studied by IR Spectroscopy and Quantum Chemistry

The adsorption of different isotopic ozone mixtures on TiO2 at 77K was studied using FTIR spectroscopy and DFT calculations of cluster models. In addition to weakly bound ozone with band positions close to those of free or dissolved molecules, the spectrum of chemisorbed species was observed. The splitting of the nu(1+3) combination band to eight maxima due to different isotopomers testified to the loss of molecule symmetry. The frequencies of all the isotopic modifications of the ozone molecules which form monodentate or bidentate complexes with four- or five-coordinated titanium atoms were calculated and compared with those of experimentally observed spectra. The four considered complexes adequately reproduced the splitting of the nu(1+3) vibration band and the lowered anharmonism of chemisorbed O-3. The energetically most favorable monodentate complex with four-coordinated titanium atoms showed good agreement with the observed spectra, although a large difference between the frequencies of nu(1) and nu(3) modes was found. For better coherence with the experiment, the interaction of the molecule with adjacent cations must be considered.