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.