Solvothermal synthesis of hierarchical TiO₂ nanostructures with tunable morphology and enhanced photocatalytic activity

Graphical abstract: - Highlights: • Hierarchical anatase TiO₂ nanostructures with enhanced photocatalytic activity are synthesized by solvothermal method. • A mechanism for enhanced photocatalytic activity of chrysanthemum-like hierarchical TiO₂ nanostructures is proposed. • A possible formation mechanism is suggested to explain the transformation from rose-like to chrysanthemum-like, and to sea-urchin-like. - Abstract: This paper presents controllable growth and photocatalytic activity of TiO₂ hierarchical nanostructures by solvothermal method at different temperatures. It is revealed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) that the morphology of TiO₂ can be effectively controlled as rose-like, chrysanthemum-like and sea-urchin-like only changing solvothermal temperature. BET surface area analysis confirms the presence of a mesoporous network in all the nanostructures, and shows high surface area at relatively high temperature. The photocatalytic activities of the photocatalysts are evaluated by the photodegradation of RhB under UV light irradiation. The TiO₂ samples exhibit high activity on the photodegradation of RhB, which is higher than that of the commercial P25. The enhancement in photocatalytic performance can be attributed to the synergetic effect of the surface area, crystallinity, band gap and crystalline size.