Self-induced synthesis of phase-junction TiO₂ with a tailored rutile to anatase ratio below phase transition temperature

The surface phase junction of nanocrystalline TiO₂ plays an essential role in governing its photocatalytic activity. Thus, facile and simple methods for preparing phase-junction TiO₂ photocatalysts are highly desired. In this work, we show that phase-junction TiO₂ is directly synthesized from Ti foil by using a simple calcination method with hydrothermal solution as the precursor below the phase transition temperature. Moreover, the ratio of rutile to anatase in the TiO₂ samples could be readily tuned by changing the ratio of weight of Ti foil to HCl, which is used as the hydrothermal precursor, as confirmed by the X-ray diffraction analysis. In the photocatalytic reaction by the TiO₂ nanocomposite, a synergistic effect between the two phases within a certain range of the ratio is clearly observed. The results suggest that an appropriate ratio of anatase to rutile in the TiO₂ nanocomposite can create more efficient solid-solid interfaces upon calcination, thereby facilitating interparticle charge transfer in the photocatalysis.