title: A density functional tight binding study of acetic acid adsorption on crystalline and amorphous surfaces of titania.
abstract: We present a comparative density functional tight binding study of an organic molecule attachment to TiO2 via a carboxylic group, with the example of acetic acid. For the first time, binding to low-energy surfaces of crystalline anatase (101), rutile (110) and (B)-TiO2 (001), as well as to the surface of amorphous (a-) TiO2 is compared with the same computational setup. On all surfaces, bidentate configurations are identified as providing the strongest adsorption energy, Eads = -1.93, -2.49 and -1.09 eV for anatase, rutile and (B)-TiO2, respectively. For monodentate configurations, the strongest Eads = -1.06, -1.11 and -0.86 eV for anatase, rutile and (B)-TiO2, respectively. Multiple monodentate and bidentate configurations are identified on a-TiO2 with a distribution of adsorption energies and with the lowest energy configuration having stronger bonding than that of the crystalline counterparts, with Eads up to -4.92 eV for bidentate and -1.83 eV for monodentate adsorption. Amorphous TiO2 can therefore be used to achieve strong anchoring of organic molecules, such as dyes, that bind via a -COOH group. While the presence of the surface leads to a contraction of the band gap vs. the bulk, molecular adsorption caused no appreciable effect on the band structure around the gap in any of the systems.
authors.affiliation: Department of Mechanical Engineering, National University of Singapore, Block EA #07-08, 9 Engineering Drive 1, Singapore 117576, Singapore. mpemanzh@nus.edu.sg.
authors.forename: Sergei
authors.initials: S
authors.lastname: Manzhos
authors.affiliation: Department of Chemical System Engineering, School of Engineering, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan. giacomo@tcl.t.u-tokyo.ac.jp.|CREST-JST, 7 Gobancho, Chiyoda-ku, Tokyo 102-0076, Japan. giacomo@tcl.t.u-tokyo.ac.jp.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Giorgi
authors.affiliation: Department of Chemical System Engineering, School of Engineering, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan. yamasita@chemsys.t.u-tokyo.ac.jp.|CREST-JST, 7 Gobancho, Chiyoda-ku, Tokyo 102-0076, Japan. yamasita@chemsys.t.u-tokyo.ac.jp.
authors.forename: Koichi
authors.initials: K
authors.lastname: Yamashita
mesh_terms: D019342:Acetic Acid / Q000737:chemistry*; D000327:Adsorption; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: C009495:titanium dioxide; D014025:Titanium; D019342:Acetic Acid