Surface decoration of Bi2WO6 superstructures with Bi2O3 nanoparticles: an efficient method to improve visible-light-driven photocatalytic activity

Abstract

Bi₂WO₆ superstructures have attracted extensive attention in the photocatalytic field, but their practical application has been limited by drawbacks such as an unsatisfactory visible-light photoresponse range. To address these drawbacks, we have developed a simple strategy by surface decoration of Bi₂WO₆ superstructures with Bi₂O₃ nanoparticles through a dip-coating–anneal method. The characterization results confirm robust construction of nanojunctions in the Bi₂WO₆ superstructure decorated with Bi₂O₃ nanoparticles (abbreviated as: Bi₂WO₆ SS–D–Bi₂O₃ NP) nanojunction system. Interestingly, this Bi₂WO₆ SS–D–Bi₂O₃ NP nanojunction system exhibits a broad-spectrum photoabsorption from the UV to visible-light region with an edge at ca. 650 nm, indicating a red shift of photoabsorption range compared with that of Bi₂WO₆ superstructures (edge at ca. 450 nm), nanoscale Bi₂O₃ powder (ca. 470 nm) and Bi₂O₃–Bi₂WO₆ composite microspheres (ca. 440 nm) prepared through a one-step hydrothermal route. Furthermore, by using Bi₂WO₆ SS–D–Bi₂O₃ NP as visible-light-driven (VLD) photocatalyst, the photodegradation efficiency of Rhodamine B (RhB) reaches 86% which is about 2.7 times as that (32.3%) by Bi₂WO₆ SS and 1.3 times that (64.4%) by Bi₂O₃–Bi₂WO₆ composite microspheres, in 20 min of reaction. Besides that, this nanojunction can still efficiently degrade the colorless pollutant parachlorophenol. In particular, the photocatalytic activity of the nanojunction is superior to the sum of the activities of two individual photocatalysts with the same weight of components (Bi₂WO₆ SS and Bi₂O₃ NP). Based on the above results and energy band diagram, two possible reasons have been proposed for the higher photocatalytic activity of Bi₂WO₆ SS–D–Bi₂O₃ NP nanojunction: (1) substantial broadening of the photoabsorption range and (2) efficient separation of photogenerated electron–hole pairs. This work provides some insight into the design of novel and efficient nanojunction photocatalysts with broadened photoabsorption range for enhancing VLD photocatalytic activity.