Ni-doped rutile TiO2 nanoflowers: low-temperature solution synthesis and enhanced photocatalytic efficiency

Easily recoverable photocatalysts with high activities are desirable in photocatalytic wastewater treatment. In this paper, we reported a low-temperature solution synthesis of Ni-doped flower-like rutile TiO2, which possessed an activity four times that of the commercial Degussa P25 TiO2 nanoparticles when utilized to assist photodegradation of rhodamine B in water under the illumination of a Xe lamp. More importantly, the micrometer-sized aggregations facilitate the subsequent recovery from the slurry. Hydrogen titanate nanowires were firstly achieved by interactions between metallic Ti and a H2O2 aqueous solution at 80 degrees C. A subsequent immersing at 80 degrees C of the titanate nanowires in a H2SO4 aqueous solution containing NiSO4 transformed the nanowires to rutile TiO2 nanoflowers, which were assembled by single-crystalline nanorods. The transformation proceeded through dissolution-precipitation in the acidic environment, which in sequence led to the growth of rutile nanorods that assemble the nanoflowers, via an oriented attachment mechanism. When utilized to assist photodegradation of rhodamine B in water under Xe lamp illumination, the Ni-free rutile TiO2 nanoflowers exhibited an activity double that of P25. The appropriate doping of Ni further improved the efficiency to four times that of P25. The enhanced photocatalytic activity can be attributed to both the high specific surface area of ca. 118 m(2) g(-1), and the appropriate Ni-doping that favors both the light harvesting and the charge separation.