Graphene Wrapped TiO2 Based Catalysts with Enhanced Photocatalytic Activity

Reduced graphene oxide (RGO) wrapped titanium dioxide nanocrystals (TiO2 NCs@RGO) with oxygen vacancies (Vo) and Ti3+ defects have been synthesized by electrostatically wrapping GO around TiO2 NCs followed by thermal annealing at 400 degrees C. Transmission electron microscope observations have shown that TiO2 NCs@RGO has a unique crystalline core/crystalline shell structure, which is different from the original amorphous TiO2 covered TiO2 NCs. Raman spectroscopy, X-ray photoelectron spectroscopy, and electron paramagnetic resonance have demonstrated that Vo-Ti3+ species are more readily formed in TiO2 NCs@RGO than in TiO2 NCs. As a result, TiO2 NCs@RGO exhibits enhanced optical absorption in a wide wavelength range from visible light to near IR and red-shifted absorption edge. In the photocatalytic degradation reaction of methyl orange, the photodegradation rate constant for TiO2 NCs@RGO is 2.4 times higher than that of TiO2 NCs. The enhanced photocatalytic performance can be attributed to the improved charge separation at the interface of TiO2 NCs and RGO layer and the enhanced optical absorption in visible light region due to the donor levels of the defects such as Vo-Ti3+ species. This work establishes a new method for preparing Vo defect contained TiO2 catalysts.