Synthesis of g-C3N4/Bi2O3/TiO2 composite nanotubes: enhanced activity under visible light irradiation and improved photoelectrochemical activity

Abstract

g-C₃N₄ and Bi₂O₃ were successfully incorporated into TiO₂ nanotubes (TiO₂-NT) to produce a composite nanotube material designated as g-C₃N₄/Bi₂O₃/TiO₂. The photoelectrochemical (PEC) activity under visible light irradiation with respect to bleaching of methylene blue (MB) and degradation of phenol were determined. The UV-vis absorption spectrum of the composite material, g-C₃N₄/Bi₂O₃/TiO₂-NT, was red-shifted toward a narrower band gap energy (E_g). The valence band (VB) of g-C₃N₄/Bi₂O₃/TiO₂-NT was shifted to a more positive potential resulting in an increased driving force for water oxidation. The photocurrent generated by g-C₃N₄/Bi₂O₃/TiO₂-NTs was approximately 15 times higher and the incident photon-to-current efficiency (IPCE at λ = 400 nm) was higher than that of the naked TiO₂-NTs. This response is attributed to increasing the lifetimes of photo-generated electron–hole pairs. A significantly higher PEC response in terms of the bleaching of MB was observed on g-C₃N₄/Bi₂O₃/TiO₂-NT. The roles of improved charge separation and subsequent higher electron-transfer efficiencies for in g-C₃N₄/Bi₂O₃/TiO₂-NT electrodes were examined.