Synthesis of nitrogen and terbium co-doped TiO2 nanocrystals with enhanced photocatalytic activity for AO7 degradation under visible-light radiation

Doping of TiO2 with metals and/or non-metals is an effective strategy for increasing its inherently low photocatalytic activity. In this work, TiO2 nanocrystals co-doped with nitrogen (N) and terbium (Tb) were prepared using a controlled hydrolysis method with water generated in situ via esterification of acetic acid and n-butanol. Compared with undoped TiO2 nanocrystals, co-doped TiO2 nanocrystals exhibited enhanced visible-light absorption and improved charge-carrier separation efficiency due to the synergy between N and Tb. In addition, they also had larger surface area and stronger interaction with the azo-dye acid orange 7 (AO7) compared with undoped TiO2 nanocrystals, giving rise to catalytic activity which was ca. 2× better than undoped TiO2 nanocrystals for photocatalytic degradation of AO7 under visible-light irradiation. For the given N loading, the optimal Tb doping for co-doped TiO2 nanocrystals to achieve the maximum activity was 1%, at which complete decolorization of AO7 was achieved after 5 hours of visible-light irradiation.