Mixed-phase nano-structured TiO2 composite photocatalyst for energy and energy efficiency applications
INVENTION: Northwestern scientists chemists have designed, synthesized and tested a highly active mixed-phase nano-structured titanium dioxide (TiO2) composite, which shows significantly enhanced photoactivity
ADVANTAGES: The mixed-phase TiO2 nanocomposite showed higher photoactivity than its individual components (commercial anatase and sol-gel rutile), and is also more active than Degussa P25, in both oxidation and reduction chemistry.
SUMMARY: Mixed-phase titanium dioxide (TiO2) materials, such as Degussa P25, show enhanced photoactivity largely due to the synergistic interaction between anatase and rutile phases, in which spatial charge separation hinders charge recombination. Previous results suggest that a particular nano-structured assembly of anatase and rutile nanocrystallites is necessary for the synergy to effectively occur.
Based on the structure-function understanding, an anatase-rutile nanocomposite was prepared via a simple and robust hydrothermal method, followed by sintering at 773K. A proper HCl/Ti molar ratio and low water content are key factors for the synthesis process.
The photooxidation of methylene blue under UV illumination and photoreduction of CO2 under UV/visible light illumination were used to evaluate the activity of the synthesized photocatalyst. The synthesized mixed-phase TiO2 nanocomposite demonstrated the highest photoactivity in both oxidative and reductive reactions among the TiO2 structures tested (Figure 1).
Studies by electron paramagnetic resonance spectroscopy indicated the existence of the critical nanostructured assembly and thus, optimization of charge transfer between anatase and rutile phases in the synthesized nanocomposite. These results illustrate the potential of rationally designing photocatalysts for a wide range of environmental, catalytic, energy and sensing applications.
Kimberley A. Gray, Gonghu Li
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