Publication Catalysis 2011
A. R. Almeida, M. Calatayud, F. Tielens, J. A. Moulijn, G. Mul, J. Phys. Chem. C 2011, 115, 14164.
The adsorption of cyclohexanone on different planes ((100), (101), and (001)) of anatase TiO2, with variable level of hydration, was evaluated by d. functional theory (DFT) calcns. Surface hydration was found to affect the cyclohexanone adsorption enthalpy and the calcd. IR absorption frequencies of the preferred adsorbed configurations considerably. A good correlation was found between two exptl. obsd. absorption frequencies at 1694 and at 1681 cm-1 of cyclohexanone adsorbed on TiO2, detd. by attenuated total reflection FTIR (ATR-FTIR), and frequencies calcd. for conformations of cyclohexanone interacting with the (101) surface with low and intermediate levels of hydration, resp.
The corresponding adsorption enthalpies of these adsorbed conformations amt. to -23.5 and -37.0 kJ/mol, resp. DFT calcns. show that cyclohexanone physisorption on hydrated (100) yields an adsorption enthalpy of -89.4 kJ/mol. This might be a conformation contributing to irreversible adsorption of cyclohexanone known to occur exptl. after photocatalytic activation of TiO2. Other phenomena of relevance to irreversible adsorption are also briefly discussed.