Elsevier

Materials Letters

Volume 63, Issue 28, 30 November 2009, Pages 2442-2444
Materials Letters

Preparation of B-doped titania hollow sphere and its photocatalytic activity under visible light

https://doi.org/10.1016/j.matlet.2009.08.031Get rights and content

Abstract

In this study, B-doped titania hollow spheres were prepared using hydrothermally prepared carbon spheres as template. The photocatalytic activity of as-prepared hollow titania spheres was determined by degradation of Reactive Brilliant Red dye X-3B (C.I. reactive red 2) under visible light irradiation, and was compared to commercial P25 titania. It was revealed that the photocatalytic activity of the hollow titania spheres enhanced a lot. The apparent rate constant of the hollow titania spheres was almost 22 times as that of P25 titania. A photocurrent–time spectrum was also applied to investigate the efficiency of electron transfer in the process of photocatalysis reactions by different samples.

Introduction

In the past several decades, a promising method as an alternative to conventional methods for wastewater treatment is represented by titania photocatalysis due to its high efficiency, low cost, and long-term stability against photo-corrosion [1]. However, its technological application seems limited by several factors, among which the most restrictive one is the need of using an ultraviolet (UV), wavelength (λ) < 387 nm, as excitation source due to its wide band-gap (3.2 eV for anatase) [2]. Doping with non-metallic elements has received much attention for extending of its light absorption into visible region [3], [4], [5], [6], [7]. Asahi et al. [3] reported the preparation of nitrogen-doped TiO2 with visible light sensitivity. Hattori et al. [5] found a significant enhancement on photocatalytic activity of titania by doping with F ions. More recently, TiO2 doped with boron has received a lot of attention [8], [9], [10], [11], [12]. They found that the absorption edge was red-shifted and photocatalytic efficiency was enhanced.

On the other hand, fabrication of titania hollow microspheres has recently attracted enormous attention because of their low density, high surface area, good surface permeability as well as large light-harvesting efficiencies [13]. However, the preparation of hollow titania with visible responsive activity has not been investigated until to now. Therefore, we prepared B-doped titania hollow spheres in the present work by a simple method. Furthermore, we investigated the photocatalytic activity of the as-prepared B-doped titania hollow spheres under visible light irradiation.

Section snippets

Preparation of carbon spheres

6 g of glucose was firstly dissolved in 40 ml of water. The solution was then sealed in a 50 ml Teflon-lined autoclave and maintained at 170 °C for 5 h. The products were then washed by alcohol and water for five cycles, respectively. The carbon spheres were then dried at 80 °C for 2 h under vacuum.

Preparation of B-doped titania

B-doped titania was prepared as follows: 50 ml Ti (OBu)4 diluted with 16 ml (i-PrOH) was dropwise added into NaBH4 aqueous solution, whose acidity was adjusted with HNO3 (pH = 2). After Ti (OBu)4 was hydrolyzed

Characterization of BTH

Fig. 1 compares the UV–visible diffuse reflectance spectra of BTH and TH. The results indicated that doped boron by this method can give rise to a clear red-shift in the optical response of the titania hollow spheres. Furthermore, high visible absorbance (400–550 nm) was observed for B-doped samples. The XRD pattern of BTH is shown in the inset of Fig. 1. As shown in the figure, the particles had formed anatase phase since the characteristic diffraction peaks of anatase (major peaks: 25.4°,

Summary

A green and simple method was reported to prepare B-doped titania hollow spheres. The photocatalytic activity of as-prepared hollow titania spheres was determined by degradation of X-3B under visible light irradiation, and compared to commercial P25 titania. The apparent rate constant of the hollow titania spheres was almost 22 times as that of P25 titania. Photoelectrochemical results illustrate that B-doped titania hollow spheres behave enhanced photocatalytic activity for enhancing

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