Visible light responsive electrospun TiO2 fibers embedded with WO3 nanoparticles

Article abstract of DOI:10.1246/cl.2011.1161

TiO₂WO₃ composite fibers were prepared by electrospinning. The fibers have an average diameter of 1.0 μm. The XRD pattern of the TiO₂WO₃ composite fibers indicates the presence of anatase and rutile phases of TiO₂ and an orthorhombic phase of WO₃. The photocatalytic degradation of acetaldehyde under visible light was achieved with the TiO₂WO₃ composite fibers.

Full text of DOI:10.1246/cl.2011.1161

doi:10.1246/cl.2011.1161
Published on the web September 28, 2011
1161
Visible Light Responsive Electrospun TiO2 Fibers Embedded with WO3 Nanoparticles
Kazuya Nakata,*1,2 Baoshun Liu,1 Yuri Goto,1,3 Tsuyoshi Ochiai,1,2 Munetoshi Sakai,1
Hideki Sakai,3 Taketoshi Murakami,1 Masahiko Abe,2,3 and Akira Fujishima*1,2
1Photocatalyst Group, Kanagawa Academy of Science and Technology,
KSP Building East 412, 3-2-1 Sakado, Takatsu-ku, Kawasaki, Kanagawa 213-0012
2Research Institute for Science and Technology, Energy and Environment Photocatalyst Research Division,
Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601
3Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510
(Received July 14, 2011; CL-110607; E-mail: pg-nakata@newkast.or.jp)
TiO2-WO3 composite fibers were prepared by electro-
spinning. The fibers have an average diameter of 1.0 ¯m. The
XRD pattern of the TiO2-WO3 composite fibers indicates the
presence of anatase and rutile phases of TiO2 and an
orthorhombic phase of WO3. The photocatalytic degradation
of acetaldehyde under visible light was achieved with the TiO2-
WO3 composite fibers.
Photocatalysis based on TiO2 is widely used for many
applications such as air and water purification, self-cleaning and
antibacterial surfaces.1-3 A current effort in photocatalysis is the
improvement of the photocatalytic performance of TiO2, which
is only able to use UV light (<400 nm) comprising 3% of the
solar spectrum. Thus, it is very important to develop efficient
photocatalysts that can be driven by visible light comprising
about 42% of the energy of the solar spectrum. TiO2-WO3
composites have been shown to be efficient photocatalysts
driven by visible light because of the combination of the narrow
band gap of WO3 and charge separation at the interface of TiO2
and WO3.4-7
Another approach to improve the efficiency of TiO2 is the
introduction of a micro- or nanostructure because micro- or
nanostructured materials have a larger surface area and a
stronger adsorption capacity, which favors photocatalytic per-
formance. Electrospinning is a significant process because it
allows for the preparation of fibers with facility and versatil-
ity.8-10 The electrospun fibers can be treated as self-standing film
and have 3-D open structure, which is an advantage for
photocatalytic reaction.
In this work, the preparation, characterization, and evalua-
tion of the photocatalytic performance of a TiO2-WO3 compo-
site fiber prepared by electrospinning was examined.
The preparation of the TiO2-WO3 composite fiber was
carried out as follows: poly(vinylpyrrolidone) (PVP) was
Figure 1. SEM images of the TiO2-WO3 composite fiber
(a) before and (b) after calcination.
dissolved in a mixed solution containing EtOH (13 mL) and
acetic acid (1.9 mL) followed by stirring for 1 h. The obtained
solution was added to titanium tetraisopropoxide (6.3 mL). After
further stirring for 1 h the solution was added to WO3 particles
(1.0 g, Aldrich). The as-prepared solution was loaded into a
syringe and the nozzle, which was connected to a positive
electrode from a high voltage generator, and a metallic plate
covered with a piece of aluminum foil was used as a collecting
substrate; this was grounded. The voltage was set at 15 kV and
the working distance was 15 cm. The electrospun fiber was
calcined at 600 °C for 2 h in air to remove the PVP and to
crystallize it.
Figure 1 shows SEM images of the as-spun and calcined
TiO2-WO3 composite fibers. The fibers had an average diameter
of 1.2 ¯m before calcination. It seems that the fibers contain
WO3 particles. After the calcination the average diameters of the
fibers decreased slightly (ca. 1.0 ¯m) because the organic
component, PVP, was selectively removed by combustion and
the inorganic components became crystallized.
Figure 2 shows an XRD pattern for the TiO2-WO3
composite fibers after calcination. The TiO2-WO3 composite
Chem. Lett. 2011, 40, 1161-1162
© 2011 The Chemical Society of Japan
www.csj.jp/journals/chem-lett/

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Figure 2. XRD pattern of the TiO2-WO3 fibers.
Figure 4. Photodecomposition of acetaldehyde and the pro-
duction of CO2 on the TiO2-WO3 composite fibers after
calcination as a function of visible light irradiation time.
reached 78 ppm after 90 min. Based on the degradation reaction
of acetaldehyde, the production of CO2 will be twice (200 ppm)
that of the initial concentration of acetaldehyde.8 In this case, the
concentration of CO2 was lower than expected for this experi-
ment because of the generation of the intermediate product,
acetic acid, during the degradation process instead of CO2,11
which is similar to the case that pristine WO3 showed
uncompleted photocatalytic degradation for acetaldehyde.12
In conclusion, a TiO2-WO3 composite fiber was prepared
by electrospinning. The composite fiber shows visible light
absorption. The photocatalytic degradation of acetaldehyde
under visible light was achieved for the TiO2-WO3 composite
fibers.
This work was supported by a Grant-in-Aid for Scientific
Research (B) from the Ministry of Education, Culture, Sports,
Science and Technology of Japan.
Figure 3. UV-visible absorption spectra of the TiO2 and
TiO2-WO3 composite fibers.
References
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fibers contain an anatase phase and a rutile phase of TiO2 and an
orthorhombic phase of WO3.
2
UV-vis spectra for the TiO2 and TiO2-WO3 composite
fibers are shown in Figure 3. A significant increase in the
absorption at wavelengths shorter than 400 nm is assigned to the
intrinsic band gap absorption of TiO2. The absorption spectrum
of the TiO2-WO3 composite fibers indicates the absorption of
more visible light than that of pristine TiO2 fibers, which is
attributed to the fact that WO3 has a narrow band gap.
We investigated the photocatalytic decomposition of acet-
aldehyde and the simultaneous production of CO2 under visible
light (>420 nm) using the TiO2-WO3 composite fiber after it
was calcined, as shown in Figure 4. After reaching equilibrium
in the dark over 1 h the concentration of acetaldehyde decreased
to 70 ppm from an initial concentration of 100 ppm, and this was
due to the physical adsorption of acetaldehyde on the surface of
the TiO2-WO3 composite fiber. Upon irradiation by visible light
at an intensity of 6000 lx, the concentration of the acetaldehyde
decreased whereas that of CO2 increased; its concentration
3
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Chem. Lett. 2011, 40, 1161-1162
© 2011 The Chemical Society of Japan
www.csj.jp/journals/chem-lett/