Nb2O5/TiO2 heterojunctions: Synthesis strategy and photocatalytic activity

In the present study, in situ hydrolysis-loading of ultra-fine niobium oxide nanoparticles on the surface of rutile TiO2 is developed as a new strategy to synthesize Nb2O5/TiO2 heterojunctions. The physico-chemical properties of Nb2O5/TiO2 heterojunctions are fully characterized by X-ray diffraction, Raman, UV–vis, X-ray photoelectron spectroscopy and transmission electron microscopy. The separation efficiency of photo-generated electron–hole pairs on Nb2O5/TiO2 heterojunctions under irradiation is investigated by photoluminescence and electron spin resonance spectroscopy. The activity of Nb2O5/TiO2 heterojunctions is examined in the selective photocatalytic oxidation of α-phenylethanol and the photocatalytic reforming of methanol. In both reactions, Nb2O5/TiO2 heterojunctions exhibit distinct higher photocatalytic activity than pure rutile TiO2 or Nb2O5. The photocatalytic activity of Nb2O5/TiO2 heterojunctions is relevant with Nb/Ti ratio and the optimal activity is obtained at Nb/Ti = 0.12 with the highest separation efficiency of photo-generated electron–hole pairs. Integrating the physico-chemical and photocatalytic properties, the factors controlling the photocatalytic activity of Nb2O5/TiO2 heterojunctions are discussed in detail.