Synthesizing mixed-phase TiO₂ nanocomposites using a hydrothermal method for photo-oxidation and photoreduction applications

Mixed-phase titanium dioxide (TiO₂) materials, such as Degussa P25, show high photocatalytic activity due largely to the synergistic effect between anatase and rutile phases, in which spatial charge separation hinders charge recombination. Our previous studies indicate that a particular nanostructured assembly of anatase and rutile crystallites is necessary for the synergy. In this paper, we apply this structure-function understanding to the synthesis of highly active TiO₂ nanocomposite photocatalysts. Using simple synthetic procedures, we demonstrate an ability to design a highly active nanocomposite that shows enhanced photoactivity in both oxidative and reductive chemistry. Studies by electron paramagnetic resonance spectroscopy indicate the existence of the critical nanostructured assembly and thus the optimization of charge transfer between anatase and rutile phases in the synthesized nanocomposite. These results illustrate the potential of rationally designing photocatalysts for energy applications.