Enlarging the application of potassium titanate nanowires as titanium source for preparation of TiO2 nanostructures with tunable phases

One-dimensional (1D) structured sodium titanate (Na-titanate) derived from the NaOH treatment of TiO2 nanoparticles under highly basic conditions are widely used as precursors to prepare TiO2 with various crystalline phases, shapes, sizes or exposed facets. However, potassium ions in the potassium titanate (K-titanate) structure couldn't be fully exchanged by protons, therefore only a few studies have been conducted on the preparation of pure TiO2 from K-titanate precursor. In this paper, we report that K-titanate could be fully transferred to pure TiO2 through hydrothermal reaction in acidic solution. As a result, pure phase and mixtures of four TiO2 polymorphs (anatase, rutile, brookite, and TiO2(B)) could be controllably obtained. The transformation mechanism from K-titanate to TiO2 counterparts was proposed. In addition, the photocatalytic activities of TiO2 nanocrystals with different crystalline-phase composition have been investigated, and the mixed-phase samples showed much higher photocatalytic activity than either of the pure component phases.