Res. Chem. Intermed.
, Vol. 31, No. 4–6, pp. 521–527 (2005)
Also available online - www.vsppub.com
Role of d electrons in oxide semiconductor CoTa
on photocatalytic and photophysical properties
, YAN-FENG CHEN
and ZHI-GANG ZOU
Eco-Materials and Renewable Energy Research Center (ERERC), Nanjing University,
Nanjing 210093, China
Photoreaction Control Research Center (PCRC), National Institute of Advanced Industrial Science
and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
Received 5 April 2004; accepted 25 June 2004
photocatalyst was synthesized by a solid-state reaction method. The photophys-
ical and photocatalytic properties of the photocatalyst were investigated. The experimental results
revealed out that H
could be photocatalytically evolved from aqueous CH
OH solution with Pt-
loaded photocatalyst powder and O
from aqueous AgNO
solution under visible light irradiation
(λ>420 nm). The average evolution rates of H
were 0.91 and 1.14 µmol/h, respectively.
The crystal and electron structures of the photocatalyst are discussed with respect to its photocatalytic
Keywords: Photocatalyst; cobalt tantalum oxide; visible light; water decomposition.
Over the past few years there has been a rapid increase in the number of investiga-
tions on the photocatalytic decomposition of water with an oxide semiconductor as
the catalyst [1–3]. Theoretically, if the conduction band potential level of a semi-
conductor is more negative than that of hydrogen evolution, and the valence band
potential level is more positive than that of oxygen evolution, it is possible to de-
compose water into H
. However, it is very difﬁcult to split water even using
the photocatalysts having such a band structure as mentioned above [3–5]. There
are other two factors in addition, i.e., concentration and mobility of charge, which
directly affect the photocatalytic and photophysical properties of the photocatalysts.
It is known that the d-electronic orbital structure of transition metals in oxide
semiconductor plays a crucial role in determining concentration and mobility of
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