One-step solvothermal preparation of visible light-driven N-modified Nb2O5 photocatalyst using nitric acid as the nitrogen source

• N-modified Nb2O5 was prepared by one-step solvothermal method using HNO3 as N source.
• Strong and wide absorption of visible light.
• High photocatalytic activity in the reduction of aqueous Cr6+ under visible light.
• Nb2O5 prepared using NH3·H2O had no visible light-driven photocatalytic activity.

This letter reports the preparation of visible light-driven N-modified Nb2O5 photocatalyst by an alternative one-step solvothermal route, which employs nitric acid as the nitrogen source. N-modified Nb2O5 nanoparticles (which were abbreviated as Nb2O5–HNO3) were prepared directly through the solvothermal reactions of NbCl5, nitric acid (14.36–15.16 mol/L) and absolute ethanol at 200 °C for 15 h. The composition, structure and photoabsorption feature of Nb2O5–HNO3 were characterized by X-ray photoelectron spectroscopy, transmission electron microscopy, N2 adsorption/desorption isotherms and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of Nb2O5–HNO3 was examined in the reduction of aqueous Cr(VI) under visible light (λ>420 nm) irradiation, and compared with that of Nb2O5–NH3 (which denoted the sample prepared when 13.32–14.44 mol/L ammonia water replaced nitric acid). It was observed that Nb2O5–HNO3 displayed distinct absorption of visible light and high photocatalytic activity in the reduction of aqueous Cr(VI) under visible light (λ>420 nm) irradiation, whereas Nb2O5–NH3 exhibited no visible light-absorbing ability and no visible light-driven photocatalytic activity. This work suggests that nitric acid is an alternative nitrogen source for one-step solvothermal preparation of visible light-driven N-modified Nb2O5 photocatalyst.