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Improved photocatalytic activity of Bi2O3 composites derived from a layered precursor Jian Song • Weijie Yang • Feipeng Jiao • Jingang Yu

Received: 10 May 2013 / Accepted: 21 July 2013 / Published online: 6 August 2013 Ó Akade´miai Kiado´, Budapest, Hungary 2013

Abstract ZnO/Al2O3/Bi2O3 mixed-metal oxide (ZnAlBi-MMO) has been successfully prepared by the coprecipitation method and controllable calcination. Powder X-ray diffraction, high-resolution transmission electron microscopy and UV–Vis diffuse reflectance spectra confirmed the structure of as-synthesized solids. The results reveal that the synthetic methods can provide the heterostructure of MMO. The photocatalytic activity of ZnAlBi-MMO was evaluated by the photodegradation of methylene blue (MB) under visible light irradiation. Factors that may affect the photodegradation behavior were studied such as calcination temperature, catalyst dose and pH. Furthermore, the stability of synthesized photocatalysts was investigated by studying the photocatalytic ability of reclaimed ZnAlBi-MMO. The results showed the removal efficiency of MB was higher than 83 % even after four successive photoreactions, demonstrating the great potential of layered double hydroxides as catalyst supports. The possible mechanism underlying the enhanced photocatalytic activity of Bi2O3 was also discussed. Keywords Bi2O3  Photocatalysts  Visible light  Dye degradation  Layered double hydroxides

Introduction Bi2O3 has shown promise as a novel photocatalyst with a direct band gap 2.8 eV [1], which can be excited by visible light. Unfortunately, the photocatalytic activity is not high for the fast recombination of photogenerated electron–hole pairs. A variety of approaches have been explored to enhance the photocatalytic activity of J. Song  W. Yang  F. Jiao (&)  J. Yu College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China e-mail: [email protected]

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Reac Kinet Mech Cat (2013) 110:529–541

Bi2O3, including phase/morphological control [2], metal loading [3] and coupled semiconductors [4]. A semiconductor composite, which constructs a heterojunction interface, can facilitate the interfacial charge transfer and enhance the separation of photoinduced charges. Recently, a series of semiconductor heterojunctions based on Bi2O3 have been reported including Bi2O3/Cu2O [5], Bi2O3/BaTiO3 [6], Bi2O3/ TeO2/V2O5 [7], CeO2/Bi2O3 [8], Bi2O3/MgO [9]. Various methods have been developed for the preparation of composites based on bismuth oxides. Thin films can be fixed and reclaimed easily. However, due to the low melting point (1,097 K), the volatility of bismuth, and the variation of valence states of bismuth (II, III, and V), it is very difficult to obtain stoichiometric Bi2O3 ultrathin films with good crystallinity [10]. Bi2O3 hollow microspheres were successfully prepared by a templated method [11] and exhibited obviously enhanced photocatalytic activity. However, the use of templates can bring new pollution in the preparation. In addition, the hydrot