Three-dimensional sea-urchin-like hierarchical TiO2 microspheres synthesized by a one-pot hydrothermal method and their enhanced photocatalytic activity

Novel three-dimensional sea-urchin-like hierarchical TiO2 superstructures were synthesized on a Ti plate in a mixture of H2O2 and NaOH aqueous solution by a facile one-pot hydrothermal method at a low temperature, followed by protonation and calcination. The results of series of electron microscopy characterizations suggested that the hierarchical TiO2 superstructures consisted of numerous one-dimensional nanostructures. The microspheres were approximately 2–4 μm in diameter, and the one-dimensional TiO2 nanostructures were up to 600–700 nm long. A two-stage reaction mechanism, i.e., initial growth and then assembly, was proposed for the formation of these architectures. The three-dimensional sea-urchin-like hierarchical TiO2 microstructures showed excellent photocatalytic activity for the degradation of Rhodamine B aqueous solution under sunlight irradiation, which was attributed to the special three-dimensional hierarchical superstructure, and increased number of surface active sites. This novel superstructure has promising use in practical aqueous purification.

SEM images of the samples synthesized at different hydrothermal temperatures for 8 h: (a) 75; (b) 100; (c) 120; and (d) 140°C, followed by calcination at 450 °C for 2 h.Figure optionsDownload as PowerPoint slideHighlights
► Effects of calcination temperature on the phase transformation were studied.
► Effects of hydrothermal temperature and time on the morphology growth were studied.
► A two-stage reaction mechanism for the formation was presented.
► The photocatalytic activity was evaluated under sunlight irradiation.
► Effects of calcination temperature on the photocatalytic activity were studied.