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International Journal of Photoenergy
Volume 6, Issue 1, Pages 35-41

Adsorption and reactions of CH2Br2 on TiO2: Effects of H2O and O2

Department of Chemistry, National Cheng Kung University, Tainan, Taiwan

Copyright © 2004 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The adsorption, thermo- and photo-reactions of CH2Br2 on powdered TiO2 as well as the effects of H2O and/or O2 have been studied by Fourier-transform infrared spectroscopy. CH2Br2 is adsorbed molecularly on the surface at 35C, interacting with the surface OH groups. It is completely desorbed or decomposes to form CH3O(a) and HCOO(a) in a vacuum by 250C, probably via dioxymethylene (-OCH2O-). The presence of adsorbed H2O accelerates the formation of CH3O(a) and HCOO(a) from CH2Br2 dissociation. Adsorbed CH2Br2 decomposes to form CO(a), HCOO(a), CO3(a), and/or CO2(a) under 400 nm irradiation, depending on whether the presence of H2O and/or O2. The presence of O2 increases the photoreaction rate of CH2Br2(a) and the photodecomposition is further accelerated with addition of H2O.