A facile method for synthesis of N-doped TiO2 nanooctahedra, nanoparticles, and nanospheres and enhanced photocatalytic activity

► N-doped TiO2 nanooctahedra, nanoparticles and nanospheres were successfully synthesized through nitrification of the corresponding TiO2 nanostructures in the presence of ammonia gas at 700 °C for 30 min. ► UV-vis absorption results show that all the as-synthesized N-doped TiO2 samples present red-shift absorption up to ∼410 nm, which can be ascribed to the addition energy level between TiO2 valence and conducion band. ► Amongst as-synthesized samples, the N-doped TiO2 nanooctahedra show the best behavior under UV-vis and visible light irradiation due to the exposed {1 0 1} facets. ► Therefore, N-doped TiO2 nanooctahedra can be a promising photocatalyst in photodegradation for organic compounds, photoredox for carbon oxide and so on under UV-vis irradiation.