Three-dimensional sea urchin-like TiO2 synthesized via facile hydrothermal method: Its properties and solar photocatalytic activity

• Facile EG-assisted hydrothermal method was used to fabricate 3D sea urchin-like TiO2.
• NaOH promoted TBOT precipitation while EG served as template.
• The photocatalytic activity was studied under natural sunlight irradiation.
• Sea urchin-like TiO2 superstructures show excellent photocatalytic activity.
• Micro-sized sea urchin-like TiO2 is easy to be separated in liquid by sedimentation.

Three-dimensional (3D) sea urchin-like TiO2 (SUT) superstructures were fabricated via one-pot ethylene glycol (EG)-assisted hydrothermal treatment at 180 °C for 12 h. As revealed by the scanning electron microscopic images at various hydrothermal reaction time, EG served as a template in the formation of SUT under hydrothermal conditions. EG is a relatively green solvent, has high boiling point, high water solubility, low toxicity, and low cost. At 350 °C calcination in air, SUT with high specific surface area (∼197 m2/g), pure anatase TiO2 crystallite phase, and high photocatalytic efficiency under natural sunlight was obtained. The solar photocatalytic degradation of 20 mg L−1 methylene blue (MB) aqueous solution showed that the performance of as-synthesized SUT-350 was comparable with the commercially available Degussa (Evonik) P25 and Wako anatase TiO2. Mineralization of MB after the treatment was confirmed by the reduction in chemical oxygen demand (COD). Moreover, it was found that micro-sized SUT settled faster than the nano-sized powders of Degussa (Evonik) P25 and Wako anatase TiO2, which means that the as-synthesized SUT is easier to be separated from the liquid phase after the treatment. With these results, SUT synthesized via EG-assisted hydrothermal method, exhibited great potential for eco-friendly and energy-efficient photocatalytic water treatment.

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