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

Abstract

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 °C. A subsequent immersing at 80 °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 m² g⁻¹, and the appropriate Ni-doping that favors both the light harvesting and the charge separation.