Sodium titanate nanowires as a stable and easily handled precursor for the shape controlled synthesis of TiO2 and their photocatalytic performance

Abstract

Sodium titanate nanowires (STNWs), a stable and easily handled precursor, were used for the shape controlled synthesis of TiO₂. By varying the composition of the reaction solutions, the morphology of TiO₂ could be readily controlled by the hydrothermal treatment of the STNWs. Three different shapes of TiO₂: nanospindles, hollow microspheres, and one dimensional chain-like aggregates, were prepared without using any templates by adding a small volume of HF (1 mL) or (and) H₂O₂ (5 mL) to the hydrothermal solutions. The structures, textures, morphologies, optical properties, adsorption capacities, and photocatalytic activities of the samples were carefully investigated. Chain-like TiO₂ aggregates showed the highest photocatalytic performance for the degradation of methyl orange. A “dissolution–nucleation” process was proposed for the transformation of STNWs to nanospindles and hollow microspheres, while a topochemical reaction process was described for the formation of the chain-like TiO₂ aggregates. The dissolution of STNWs, and the nucleation and growth of TiO₂ were affected by the additions of H₂O₂ and HF. H₂O₂ benefits the crystallization of TiO₂, while HF favors the formation of plate-like particles and surface fluorination. The impact of these roles on the morphologies, surface structures, and photocatalytic behaviors of the prepared TiO₂ samples was prospectively interpreted based on the characterization results and reported references.