Vol. 33, No. 5
TITANIA FILMS
801
3
ϩ
centers in anatase is unknown, work by Gratzel and Howe [16] suggests that the Fe ions
4
ϩ
are substitutionally located in Ti lattice sites. Of course, the substitutional procedure is
3
ϩ
expected to influence the placement of the Fe ions within the TiO lattice. It is possible that
2
3
ϩ
3ϩ
the low reactivity of Fe -doped films may have been due to the fact that Fe ions acted as
charge carrier recombination sites.
Nevertheless, the photocatalytic materials reported in this work hold promise for such
applications as environmental remediation, self-cleaning materials, and controlled synthesis.
Further work into other TiO -mediated photocatalytic reactions is necessary before some of
2
the properties of the TiO -based multilayered photocatalysts reported in this study can be
2
conclusively demonstrated.
CONCLUSIONS
Porous films synthesized in this work had several unique features: (1) high surface area to
volume ratios, (2) high optical transparency, (3) a novel way of separating the reductive sites
from the oxidative sites, and (4) possible molecular sieve properties. The separation of
reductive sites from oxidative sites was achieved through a prudent arrangement of TiO
2
3
ϩ
layers, Pt electrode, and the porous silica–alumina base. Doping with Fe
detrimental to the overall rate of acetic acid decomposition.
ions was
ACKNOWLEDGMENTS
P.S. thanks UNESCO/MONBUSHO for the award of a research fellowship.
REFERENCES
1
.
D.F. Ollis, E. Pelizzetti, and N. Serpone, in Photocatalysis: Fundamentals and Applications, ed.
N. Serpone and E. Pelizzetti, Chap. 18, Wiley-Interscience, New York (1989).
M.A. Fox and M.T. Dulay, Chem. Rev. 93, 341, (1993).
A. Mills, R.H. Davies, and D. Worsley, Chem. Soc. Rev. 22, 417 (1993).
M.R. Hoffmann, S.T. Martin, W. Choi, and D.W. Bahnemann, Chem. Rev. 95, 69 (1995).
Y. Paz, Z. Luo, L. Rabernberg, and A. Heller, J. Mater. Res. 10, 2842, (1995).
A. Fujishima, Chem. J. Chinese Univ. 16, 7 (1995).
A. Hagfeldt and M. Gratzel, Chem. Rev. 95, 49 (1995), and references therein.
F. Cao, G. Oskam, P.C. Searson, J.M. Stipkala, T.A. Heimer, F. Farzad, and G.J. Meyer, J. Phys.
Chem. 99, 11974 (1995).
2
3
4
5
6
7
8
.
.
.
.
.
.
.
9
.
B.R. Weinberger and R.B. Garber, Appl. Phys. Lett. 66, 2409 (1995).
1
1
1
1
1
0. N. Negishi, T. Iyoda, K. Hashimoto, and A. Fujishima, Chem. Lett. 841 (1995).
1. B. Kraeutler and A.J. Bard, J. Am. Chem. Soc. 100, 5985 (1978).
2. F. Babonneau, A. L e´ austic, and J. Livage, Mater. Res. Soc. Symp. Proc. 121, 317 (1988).
3. H.P. Klug and L.E. Alexander, X-ray Diffraction Procedures, Chap. 9, Wiley, New York (1954).
4. A.H. Clark, in Polycrystalline and Amorphous Thin Films and Devices, ed. L.L. Kazmerski,
Chap. 4, Academic Press, New York (1980).
1
1
5. N.N. Greenwood and A. Earnshaw, Chemistry of the Elements, Chap. 21, Pergamon, Oxford
(1984).
6. M. Gratzel and R.F. Howe, J. Phys. Chem. 94, 2566 (1990).