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Open AccessArticle

A Density Functional Tight Binding Study of Acetic Acid Adsorption on Crystalline and Amorphous Surfaces of Titania

1
Department of Mechanical Engineering, National University of Singapore, Block EA #07-08, 9 Engineering Drive 1, Singapore 117576, Singapore
2
Department of Chemical System Engineering, School of Engineering, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
3
CREST-JST, 7 Gobancho, Chiyoda-ku, Tokyo 102-0076, Japan
*
Author to whom correspondence should be addressed.
Academic Editor: Derek J. McPhee
Molecules 2015, 20(2), 3371-3388; https://doi.org/10.3390/molecules20023371
Received: 4 January 2015 / Revised: 12 February 2015 / Accepted: 13 February 2015 / Published: 17 February 2015
(This article belongs to the Special Issue Molecular Engineering for Electrochemical Power Sources)
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. View Full-Text
Keywords: titanium dioxide; anatase; rutile; (B)-TiO2; amorphous TiO2; acetic acid; adsorption; dye-sensitized solar cells; density functional tight binding titanium dioxide; anatase; rutile; (B)-TiO2; amorphous TiO2; acetic acid; adsorption; dye-sensitized solar cells; density functional tight binding
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MDPI and ACS Style

Manzhos, S.; Giorgi, G.; Yamashita, K. A Density Functional Tight Binding Study of Acetic Acid Adsorption on Crystalline and Amorphous Surfaces of Titania. Molecules 2015, 20, 3371-3388.

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