Entrapment of Bi2O3 nanoparticles in TiO2 nanotubes for visible light-driven photocatalysis

In this study, we prepared nanoparticles of the visible light-responsive photocatalyst, Bi2O3 entrapped in anatase TiO2 nanotubes (Bi2O3-in-TNTs) via a vacuum-assisted precursor-filling process followed by annealing. Owing to the unique tubular electronic structure of TiO2 nanotubes, the interior of the nanotube is in an electron-deficient state, which was confirmed by XPS spectra and H-2-TPR. Electrochemical impedance studies showed that the Bi2O3-in-TNTs demonstrated a more efficient separation of photogenerated carriers than when Bi2O3 nanoparticles were deposited on the outer wall of TiO2 nanotubes (Bi2O3-out-TNTs). Due to the confinement effect of TiO2 nanotubes, which inhibits photogenerated carriers' recombination, the Bi2O3-in-TNTs exhibited a better photocatalytic performance for the photo-degradation of methyl orange under visible light compared to Bi2O3-out-TNTs.