An ONIOM and DFT study of water and ammonia adsorption on anatase TiO2 (001) cluster

Density functional theory (DFT) calculations at ONIOM DFT B3LYP/ 6‐31G**‐MD/UFF level are employed to study molecular and dissociative water and ammonia adsorption on anatase TiO₂ (001) surface represented by partially relaxed Ti₂₀O₃₅ ONIOM cluster. DFT calculations indicate that water molecule is dissociated on anatase TiO₂ (001) surface by a nonactivated process with an exothermic relative energy difference of 58.12 kcal/mol. Dissociation of ammonia molecule on the same surface is energetically more favorable than molecular adsorption of ammonia (?37.17 kcal/mol vs. ?23.28 kcal/mol). The vibration frequency values also are computed for the optimized geometries of adsorbed water and ammonia molecules on anatase TiO₂ (001) surface. The computed adsorption energy and vibration frequency values are comparable with the values reported in the literature. Finally, several thermodynamical properties (ΔH°, ΔS°, and ΔG°) are calculated for temperatures corresponding to the experimental studies. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011