Probing water and CO2 interactions at the surface of collapsed titania nanotubes using IR spectroscopy

Kaustava Bhattacharyya, Weiqiang Wu, Eric Weitz*, Baiju K. Vijayan, Kimberly A. Gray

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

Collapsed titania nanotubes (cTiNT) were synthesized by the calcination of titania nanotubes (TiNT) at 650 °C, which leads to a collapse of their tubular morphology, a substantial reduction in surface area, and a partial transformation of anatase to the rutile phase. There are no significant changes in the position of the XPS responses for Ti and O on oxidation or reduction of the cTiNTs, but the responses are more symmetric than those observed for TiNTs, indicating fewer surface defects and no change in the oxidation state of titanium on oxidative and/or reductive pretreatment. The interaction of H2O and CO2 with the cTiNT surface was studied. The region corresponding to OH stretching absorptions extends below 3000 cm-1, and thus is broader than is typically observed for absorptions of the OH stretches of water. The exchange of protons for deuterons on exposure to D2O leads to a depletion of this extended absorption and the appearance of new absorptions, which are compatible with deuterium exchange. We discuss the source of this extended low frequency OH stretching region and conclude that it is likely due to the hydrogen-bonded OH stretches. Interaction of the reduced cTiNTs with CO2 leads to a similar but smaller set of adsorbed carbonates and bicarbonates as reported for reduced TiNTs before collapse. Implications of these observations and the presence of proton sources leading to hydrogen bonding are discussed relative to potential chemical and photochemical activity of the TiNTs. These results point to the critical influence of defect structure on CO2 photoconversion.

Original languageEnglish (US)
Pages (from-to)15469-15487
Number of pages19
JournalMolecules
Volume20
Issue number9
DOIs
StatePublished - Sep 1 2015

Keywords

  • CO adsorption
  • Collapsed titania nanotubes
  • Defect sites
  • FTIR
  • OH stretches

ASJC Scopus subject areas

  • Analytical Chemistry
  • Chemistry (miscellaneous)
  • Molecular Medicine
  • Pharmaceutical Science
  • Drug Discovery
  • Physical and Theoretical Chemistry
  • Organic Chemistry

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