A density functional theory method was used to investigate the adsorption of acetic acid and its fluorinated derivatives on (1 0 0) and (1 0 1) surfaces of anatase TiO2. It was found that while the adsorption of acetic acid and its fluorinated derivatives on the (1 0 0) surface of TiO2 does not proceeds via a proton transfer process but surprisingly adsorption on (1 0 1) surface occurred via a complete proton transfer reaction. The calculated interaction energies for adsorption on (1 0 0) surface are -19.22, -18.36, -15.73, and -60.68 kcal/mol for acetic, fluoroacetic, difluoroacetic, and trifluoroacetic acid, respectively. Similar trend observed for absorption on (1 0 1) surface and calculated interaction energies are -25.35, -23.16, -23.02, and -69.47 kcal/mol, respectively. Structurally, calculations show that when the number of fluorine substituent increases, the length of hydrogen bonding between OH group and neighboring oxygen positioned 2c (O-2c) atom is diminished. The HOMO, LUMO and HOMO-LUMO energy gap varies for the adsorption of acetic acid derivatives on both (1 0 0) and (1 0 1) surfaces changed in comparison with clean TiO2 surface. The Fermi levels were also changed after adsorption of acetic acid derivatives. (C) 2015 Elsevier B.V. All rights reserved.