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N4/Bi2WO6 heterojunction photocatalysts were successfully synthesized using consecutive hydrothermal and calcination processes. These photocatalysts were characterized using x-ray diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet-visible diffuse reflectance spectroscopy, x-ray photoelectron spectroscopy, and photoluminescence measurements. The results of these measurements indicated that the Bi2WO6 nanoparticles were approximately 30–50 nm and uniformly distributed on the surface of C3N4 lamellar structures. The 20% C3N4/Bi2WO6 displayed enhanced visible-light absorption from 432 nm to 468 nm. Photocatalytic tests also revealed that the 20% C3N4/Bi2WO6 photocatalyst exhibited significantly enhanced photocatalytic activity compared to that of pure C3N4 and Bi2WO6 under irradiation by visible light (k . 420 nm). Furthermore, the excellent photocatalytic efficiency of the 20% C3N4/Bi2WO6 photocatalyst was determined to be related to the formation of C3N4/Bi2WO6 heterojunctions, and their presence was found to be generally beneficial for the separation of photogenerated electron–hole pairs. I. INTRODUCTION

Semiconductor photocatalysts have attracted much attention, because of their potential applications in the remediation of environmental pollutants. Photocatalysts can degrade pollutants into small inorganic molecules. This chemical remediation strategy is advantageous because it is environmentally friendly, requires low reaction temperatures, and is highly stable. Photocatalysts can also be used for solar energy applications.1–5 Moreover, compared to traditional wide band gap photocatalysts such as TiO2 (3.2 eV) and ZnO (3.2 eV), visible-light-driven (VLD) photocatalysts have considerable performance advantages. Recently, bismuth tungstate (Bi2WO6), which has a relatively narrow band gap (2.6–2.8 eV) and, therefore, is a strong absorber in the visible region of spectrum (k . 420 nm), has attracted considerable attention. Bi2WO6 has shown great potential as a VLD photocatalyst.6–9 Bi2WO6 is an important layered Aurivillius oxide. Its crystal structure consists of alternating layers of bismuth oxide (Bi2O2)21 and (WO4)2
octahedrons. Furthermore, the (WO4)2
layers in Bi2WO6 are composed of linked

Contributing Editor: Xiaobo Chen Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2016.72

(WO4)2
octahedral vertices, resulting in potential photocatalytic activity toward the degradation of dyes under irradiation by visible light.10 However, there are still some disadvantages to the use of Bi2WO6 as a photocatalyst including its high recombination rate of photogenerated electron–hole pairs. Many recent attempts have been made to improve the photocatalytic activity of Bi2WO6 by creating Bi2WO6 nanostructures, doping with nonmetals or metals, and building Bi2WO6 heterostructures. Of these approaches, the combination of Bi2WO6 with other semiconductors to build heterostructures was an effective route toward improving its