AgBr-Ag-Bi2WO6 nanojunction system: A novel and efficient photocatalyst with double visible-light active components

A semiconductor-based photocatalyst system, consisting of two visible-light-driven (VLD) components and one electron-transfer system. has a great potential to efficiently photocatalytically degrade pollutants. In this paper, we have reported a simple strategy for constructing an all-solid-state AgBr-AgBi2WO6 nanojunction by a facile deposition-precipitation method with Bi2WO6 as the substrate. Two visible-light active components (AgBr, Bi2WO6) and the electron-transfer system (Ag) are spatially fixed in this nanojunction system. Due to the presence of double visible-light active components, such a AgBr-Ag-Bi2WO6 nanojunction system has the broadened visible-light photo-response range, and it also exhibits higher photocatalytic activity than photocatalysts containing single visible-light active component, such as Bi2WO6, Ag-Bi2WO6 and AgBr-Ag-TiO2 composite, for the degradation of the azo dye, Procion Red MX-5B and colorless pollutant pentachlorophenol, In addition, the initial dye concentration and pH value could greatly affect its photocatalytic activity, and the recycling experiments confirm that it is essentially stable during the photocatalytic process. In particular, the photocatalytic activity of AgBr-Ag-Bi2WO6 nanojunction is superior to the sum of the activities of two individual photocatalysts (AgBr-Ag-TiO2 and Bi2WO6) that contain the same weight of AgBr or Bi2WO6, indicating the presence of a synergic effect between two visible-light active components in AgBr-Ag-Bi2WO6 nanojunction. On the basis of the photocatalytic results and energy band diagram, the photocatalytic process that may have occurred on the AgBr-Ag-Bi2WO6 nanojunction system is proposed; the vectorial electron transfer driven by the two-step excitation of both VLD components (AgBr and Bi2WO6) contributes to its high photocatalytic activity. Therefore, this work provides some insight into the design of novel and efficient photocatalysts with multi-visible-light active components for enhancing VLD photocatalytic activity. (C) 2009 Elsevier B.V. All rights reserved.