Synthesis of Nanostructured TiO2 with Large Surface Area
Chien-Cheng Tsai, Chun-Chi Chen and Hsisheng Teng*
(Department of Chemical Engineering, National Cheng Kung University)
ABSTRACT
Titania nanotube aggregates with different
porosities were prepared from hydrothermal
treatment on commercial TiO2 particles in NaOH
followed by HCl washing. Adding perchloric acid or
sulfuric acid into TiCl4 solution was conducted to
selectively synthesize phase-pure rutile or anatase
TiO2 nanoparticles. Both methods described above
are able to synthesize nanostructured TiO2 with large
surface area.
RESULTS AND DISCUSSION
Figure 1a shows the pore size distributions of TiO2
nanotube aggregates from hydrothermal treatment in
NaOH at different temperatures. The treatment was
followed by 1 L of 0.1 N HCl washing for several
times until pH < 7.Figure 1b shows the pore size
distributions of TiO2 nanotube aggregates from
rinsing with HCl solutions of different concentrations.
Before rinsing, the hydrothermal treatment in NaOH
was conducted at 130°C.
INTRODUCTION
Titania (or TiO2), a wide band gap semiconductor,
can generate powerful oxidants (valence-band holes)
and reductants (conduction-band electrons) by
absorbing photon energies.1 Because of this feature
and its durability, TiO2 has been extensively studied
for applications in photoelectrochemical systems,
such as dye-sensitized TiO2 electrodes for
photovoltaic solar cells and water-splitting catalysts
for hydrogen generation.2 In addition to the
photon-related processes, TiO2 also has many
important applications as a conventional catalyst or
support of catalysts for the elimination of pollutants
in gas or liquid phases.3 To achieve high activity,
nanostructured TiO2 with large surface area is
required.
EXPERIMENTAL
The synthesis method for the TiO2 nanotubes and
particles are summarized as Schemes 1 and 2.
Scheme 1. Synthesis of TiO2 nanotubes.
Scheme 2. Synthesis of TiO2 particles.
Figure 1 Pore size distributions of TiO2 nanotube
Figure 2 shows the TEM images of TiO2 after
hydrothermal treatment in NaOH at 130°C. TiO2 in
the form of lamellar sheets can be seen. Nanotubes
are formed after treating the sheets with HCl, as
confirmed by the TEM image in Figure 2b. The tube
size, judged from the TEM image, ranges between 10
and 30 nm, in agreement with the results evaluated
from the BJH method.
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Figure 2 TEM images of TiO2 after NaOH
treatment (a) and that with subsequent HCl wash
Figure 3 shows the XRD patterns of the TiO2
nanoparticles from TiCl4 solution. The XRD results
show that the sample from treatment with H2SO4
(Figure 3a) is pure anatase and that with HClO4
(Figure 3b) is pure rutile. The crystalline size of the
sample from H2SO4 treatment can be of ca. 3 nm and
a BET surface area as high as 280 m2/g can be
achieved.
CONCLUSION
The pore structures of TiO2 nanotube aggregates
prepared from NaOH treatment on commercial
nanopartice P25 can be regulated by adjusting either
the treatment temperature or the concentration of
neutralization HCl solutions.
A simple route has been proposed to selectively
synthesize phase-pure anatase or rutile nanoparticles
at relatively low costs.
The present study has shown how effective the
hydrothermal method is in regulating the
morphology and crystalline phase of TiO2.
Figure 3 XRD patterns of TiO2 nanoparticles from
H2SO4 (a) and HClO4 (b) treatments.
REFERENCES AND NOTES
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D. W. Chem. Rev. 1995, 95, 69. (b) Stone V. F.; Davis
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942.
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Park N. G.; Lagemaat J.; Frank A. J.; J. Phys. Chem. B
2000, 104, 8989. (c) Khan S. U. M.; Al-Shahry M.;
Ingler W. B.; Science 2002, 297, 2243.
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Kochubei D. I.; Odegova G. V.; Kriventsov V. V.;
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