Paper NS+AS+EM-MoA2
Impact of Crystallinity, Chemical Environment and Electronic Structure of TiO2 Nanotube Arrays for Photocatalysis
Monday, October 28, 2013, 2:20 pm, Room 203 B
| Session: |
Nanowires and Nanotubes |
| Presenter: |
J. Liu, Northeastern University |
| Authors: |
J. Liu, Northeastern University
P.M. Hosseinpour, Northeastern University
S. Luo, Brookhaven National Laboratory and SUNY Stony Brook
D. Arena, Brookhaven National Laboratory
L.H. Lewis, Northeastern University
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| Correspondent: |
Click to Email |
The photocatalytic ability of TiO2 nanostructures to remove organic pollutants in waterwaste has attracted considerable attention [1]. Understanding the influence of crystallinity, chemical environment and electronic structure of TiO2 nanotubes on the photocatalytic activity is very important in optimizing this functionality. In this work, TiO2 nanotube arrays with an average tube length of 25 μm were prepared by the electrochemical anodization of Ti foil, followed by thermal treatment in O2 (oxidizing), Ar (inert), and H2 (reducing) environments at 350 °C to induce crystallization. The nanotube structure-property correlations were examined with x-ray diffraction (XRD), scanning electron microscopy (SEM) and x-ray absorption spectroscopy (XAS). The photocatalytic properties of the TiO2 nanotubes (as-anodized and annealed) were evaluated using degradation of methyl orange (a model dye compound of water pollution) in an aqueous solution under UV-visible light irradiation. The Ti L3,2-edge and O K-edge x-ray absorption spectra provide the information concerning the near-surface (~5 nm) local bonding environment and electronic structure of the nanotubes. The XAS results show that while the as-anodized amorphous TiO2 nanotubes were partially transformed to anatase phase via thermal treatment, variations in crystallinity and surface defects were observed to depend on the type of annealing atmospheres. Characteristics of anatase were more evident in both the Ti L3,2-edge and the O K-edge XAS spectra of TiO2 nanotubes annealed in O2 than in those annealed in H2 and Ar, which indicate relatively higher local order and less local defects in O2 annealed nanotubes. Nanotubes annealed in H2 exhibited a higher photodegradation rate of methyl orange than those annealed in Ar and O2. These results can be correlated with the different electronic structures that reflect the different degrees of crystallinity and the varied nature of the surface defects (i.e., oxygen vacancies) of TiO2 nanotubes that result from different processing conditions.
[1] Paramasivam, H. Jha, N. Liu and P. Schmuki, Small (2012), 8, 3073-3013.
Research supported by the National Science Foundation under Grants No. DMR-0906608 and DMR-0908767, and by the U.S. Department of Energy, Division of Materials Science, Office of Basic Energy Sciences under Contract No. DE-SC0005250. Use of the National Synchrotron Light Source, Brookhaven National Laboratory, was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886. This work was also financed by the U.S. Department of Energy, Office of Basic Energy Sciences under Contract DE-AC02-98CH10086.