Soft-chemical method for fabrication of SnO-TiO 2 nanocomposites with enhanced photocatalytic activity
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Zhihong Liub) Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, China (Received 13 November 2012; accepted 24 April 2013)
The present work reports a soft-chemical pathway for preparing SnO–TiO2 composite nanocrystallites as photocatalyst through co-hydrolysis of tetrabutyl titanate and tin (II) chloride followed by acidic peptization of the hydrolysate under mild conditions. The procedure is simple and straightforward, from which a well-dispersed semitransparent hydrosol sample is obtained. The freestanding nanocrystallites observed in the as-prepared composite show diameters of 3–5 nm. TiO2 nanoparticles have almost entirely transformed into anatase phase, and the trace amounts of Sn in existence are mainly found in SnO crystals with tetragonal structure. The photocatalytic activity of the SnO–TiO2 composites is confirmed through the photodegradation of methyl blue dye under visible light irradiation (k . 420 nm). As a p-type semiconductor, the incorporated SnO effectively improves the photocatalytic activity of TiO2 through promoting the separation of photo-generated charge carriers, inhibiting their recombination, and facilitating the reduction of O2 by the photo-generated electrons.
I. INTRODUCTION
Nano-sized titanium dioxide (TiO2) has gained growing interest because of its wide applications as photocatalysts, electrode materials, gas sensors, and photovoltaic materials.1–3 In the photoinduced systems, oxidation and reduction simultaneously take place at the surface of TiO2 particles, which in turn give rise to corresponding products. However, this process has an inherent and significant drawback, i.e., it always suffers from the recombination of photo-generated charge carriers (hole-electron pairs), which inevitably leads to the decrease of photoactivity. Therefore, to increase the photoactivity of TiO2, the photogenerated charge carriers are to be efficiently separated from each other. In the past decade, considerable efforts have been made to achieve this purpose. Choi et al.4 carried out a systematic investigation to study the photoreactivity of 21 metal ions doped into TiO2. The different effects of metal ions result from their abilities to trap and transfer electrons/holes.4,5 Compared to cations, anions (N, F, C, S etc.) less likely form recombination centers, which are more effective to enhance the photocatalytic activity.6,7 Besides, surface modifications for the improvement of the photoacitivity for TiO2 have also been reported widely. Coupling TiO2 with other semiconductor Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2013.135 1862
J. Mater. Res., Vol. 28, No. 13, Jul 14, 2013
http://journals.cambridge.org
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materials (ZnO, WO3, CdS, SnO2, etc.) has been proved as a potential way for charge-carrier separation, and the patterned photocatalysts have exhibited high activity in gas-phase and
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