Porous-ZnO-Nanobelt Film as Recyclable Photocatalysts with Enhanced Photocatalytic Activity
© The Author(s) 2010
Received: 30 April 2010
Accepted: 20 July 2010
Published: 6 August 2010
In this article, the porous-ZnO-nanobelt film was synthesized by oxidizing the ZnSe-nanobelt film in air. The experiment results show that the porous-ZnO-nanobelt film possesses enhanced photocatalytic activity compared with the ZnO-nanobelt film, and can be used as recyclable photocatalysts. The enhanced photocatalytic activity of the porous-ZnO-nanobelt film is attributed to the increased surface area. Therefore, turning the 1D-nanostructure film into porous one may be a feasible approach to meet the demand of photocatalyst application.
In the past decade, some oxide semiconductors have been widely used as photocatalysts for the degradation of organic pollutants in water [1, 2]. Based on the viewpoint of application, high photocatalytic activity and recyclability are two major factors which should be regarded. Considering that photocatalytic reaction occurs at the surface of catalysts, great efforts have been focused on nanoparticles because high photocatalytic activity can be achieved owing to their large surface area in a relative small volume (high surface–volume ratio) [3–5]. Unfortunately, however, these nanoparticle photocatalysts are generally suspended in solution, which limits the practical application due to the difficulty in their recycle . In order to avoid this problem, some works have suggested that 1D-nanostructure film adhered to a rigid substrate as photocatalysts [6–9]. However, 1D-nanostructure photocatalysts have relatively low photocatlytic activity because of their lower surface-to-volume ratio compared to nanoparticles. In a word, it seems to be impossible to realize both high photocatalytic activity and recyclability for semiconductor photocatalysts.
The porous 1D nanostructures, namely, nanoparticle chains, in which nanoparticles connect each other and constitute 1D nanostructure, have the speciality of both nanoparticles and 1D nanostructures. Here, we propose that turning 1D-nanostructure film into porous one is a feasible approach to realize both high photocatlytic activity and recyclability and thus to meet the demand of photocatalyst application. Our results reveal that the as-synthesized porous-ZnO-nanobelt film (PZNF) by oxidizing the ZnSe-nanobelt film can be used as recyclable photocatalysts with enhanced photocatalytic activity compared to the ZnO-nanobelt film (ZNF).
ZnSe nanobelts were prepared on Si substrate using H2-assisted thermal evaporation method. They were synthesized at 950°C for 30 min with the carrier gas of high-purity Ar mixed with 5% H2. PZNF was obtained by oxidizing the ZnSe-nanobelt film on Si substrate in air at 1,000°C for 2 min. In order to make a comparison of photocatalytic activity, ZNF was prepared using the Au film as catalyst by vapor phase transport method, the growth process is similar to  The substrates before and after deposition were weighed to obtain the weight of the as-prepared samples.
In order to examine the photocatalytic activity of samples, the methyl orange was chosen for photodecomposition study. Five milliliter methyl orange solution with a concentration of 1.0 × 10−5 M/L was added into two quartz cells. The PZNF and ZNF with identical mass (1.6 mg) on Si substrates were immersed into the solution. They were irradiated by light with a wavelength of 365 nm produced from a 125 W mercury lamp. The UV–vis absorption spectra of the solutions, before and after irradiation interval of 40 min, were recorded using a Cary 5E UV–Vis–NIR spectrophotometer.
Samples collected from the silicon substrates were characterized by a field-emission scanning electron microscopy (FE-SEM, Sirion 200), high-resolution transmission electron microscopy (HRTEM, JEOL-2010), and X-ray diffraction (XRD, Philips X’pert PRO).
Results and Discussion
In summary, we propose that oxidizing 1D-nanostructure film into porous one is a feasible approach to realize both high photocatalytic activity and recyclability. Our results reveal that the as-synthesized porous-ZnO-nanobelt film by oxidizing the ZnSe-nanobelt film can be used as recyclable photocatalysts with enhanced photocatalytic activity compared to the ZnO-nanobelt film. Furthermore, the method may be applied to obtain other porous materials.
This work was supported by the National Natural Science Foundation of China (Nos. 50671099, 50172048, 10374090 and 10274085), Ministry of Science and Technology of China (No.2005CB623603), and Hundred Talent Program of Chinese Academy of Sciences.
This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.
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