Synthesis of a luminescent g-C3N4–WO3–Bi2WO6/SrAl2O4:Eu2+,Dy3+ nanocomposite as a double z-scheme sunlight activable photocatalyst

Abstract

In this paper, a novel sunlight activable photocatalyst system based on the synergistic effect between a double Z-scheme g-C₃N₄–WO₃–Bi₂WO₆ nanocomposite and long-lasting phosphorescent SrAl₂O₄:Eu²⁺,Dy³⁺ nanoparticles has been designed, synthesized and successfully applied for the removal of environmental pollutants. It is especially suitable for removing dye pollutants under cloudy weather similar to the conditions in the United Kingdom and Iranian north provinces. The developed photocatalyst system in this work is based on the following important factors; the first factor is applying the double z-scheme structure of the g-C₃N₄–WO₃–Bi₂WO₆ photocatalyst to prevent fast electron–hole recombination and hence, enhance the photocatalytic efficiency of the proposed system. The second factor is applying long-lasting phosphorescent SrAl₂O₄ nanoparticles in the photocatalyst composition and hence, enhancing the population of the excited electrons on the photocatalyst surface. The emitted photons from SrAl₂O₄ nanoparticles are absorbed by the g-C₃N₄–WO₃–Bi₂WO₆ photocatalyst particles, increasing the photo absorption efficiency of the photocatalyst. This effect enhances the population of the excited electrons on the photocatalyst surface, increasing the photocatalytic reaction speed. In addition, applying phosphorescent SrAl₂O₄ nanoparticles also retains the photocatalytic activity of the photocatalyst during the night or when the light sources are off, because the phosphorescence of these nanoparticles can last up to 10 hours. These nanoparticles play the role of tiny lamps for excitation of the photocatalyst particles during the night or during cloudy weather. The proposed system was able to remove up to 98% of the environmental pollutants such as dyes in less than 20 min. In addition, its advantages for removing dye pollutants under simulated cloudy weather were confirmed.