Directed synthesis of hierarchical nanostructured TiO₂ catalysts and their morphology-dependent photocatalysis for phenol degradation

Nanostructured TiO₂ with different hierarchical morphologies were synthesized via a warmly hydrothermal route. The properties of the products were characterized by scanning electron microscopy, transmission electron microscopy. X-ray diffraction, N₂ adsorption, UV-vis spectroscopy, etc. Two of the products, TiO₂ 1D nanorods (one-dimensional rutile TiO₂ nanorods) and TiO₂ 3D_0D microspheres (three-dimensional anatase TiO₂ nanopatticle-assembled microspheres) exhibited superior photocatalytic effects on phenol degradation under UV illumination, compared with TiO₂ 3D_1D microspheres (three-dimensional rutile TiO₂ nanorods-assembled microspheres). Moreover, TiO₂ 3D_0D was superior to TiO₂ 1D, as indicated by a 30% higher mineralization of dissolved phenol. Dihydroxybenze, 4,4′-dihydroxybiphenyl, benzoquinone, maleic anhydride, etc. were identified as the degradation intermediates. The excellent catalytic effect was attributed to the structural features of TiO₂ 1D nanorods and TiO₂ 3D_0D microspheres, that is, a larger amount of surface active sites and a higher band gap energy resulted in more efficient decomposition of organic contaminants.