Computational modeling of the adsorption and •OH initiated photochemical and photocatalytic primary oxidation of nitrobenzene
The adsorption and primary oxidation step for the photodegradation of nitrobenzene (NB) have been studied computationally using MSINDO SCF MO method. The method performs efficiently for extended surface models such as Ti36O90H36. Molecular dynamics simulations have revealed that NB is linked to TiO2 surface at the titanium ion via the oxygen atoms of NO2 group. In addition, the computed vibrational density of states for the adsorbed NB molecule is in reasonably good agreement with the available experimental data and theoretical results. In order to identify the primary photochemical and photocatalytic •OH initiated photooxidation intermediates, we have employed two different theoretical approaches, frontier orbital theory and Wheland localization theory. It has been found that the meta- hydroxynitrocyclohexadienyl radical is energetically more favored than para- and ortho-hydroxynitrocyclohexadienyl radicals for the photochemical photolysis, whereas in the case of photocatalysis, the •OH radical attack is unselective and all three possible isomers have comparable stabilities.
KeywordsAdsorption Model calculations Nitrobenzene Photooxidation Semiempirical method Titanium oxide
One of the authors (H. S. Wahab) warmly thanks the Greek Ministry of Education and Religious Affairs for the award of a research fellowship and the International Institute of Education/SRF for supporting a postdoctoral stay. The work was partially supported by the Research Account of the University of Athens, under the grant KA: 70/4/6482.
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