Graphene Wrapped TiO₂ Based Catalysts with Enhanced Photocatalytic Activity

Abstract

Reduced graphene oxide (RGO) wrapped titanium dioxide nanocrystals (TiO 2 NCs@RGO) with oxygen vacancies (Vo) and Ti 3+ defects have been synthesized by electrostatically wrapping GO around TiO 2 NCs followed by thermal annealing at 400 °C. Transmission electron microscope observations have shown that TiO 2 NCs@RGO has a unique crystalline core/crystalline shell structure, which is different from the original amorphous TiO 2 covered TiO 2 NCs. Raman spectroscopy, X‐ray photoelectron spectroscopy, and electron paramagnetic resonance have demonstrated that Vo‐Ti 3+ species are more readily formed in TiO 2 NCs@RGO than in TiO 2 NCs. As a result, TiO 2 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 TiO 2 NCs@RGO is 2.4 times higher than that of TiO 2 NCs. The enhanced photocatalytic performance can be attributed to the improved charge separation at the interface of TiO 2 NCs and RGO layer and the enhanced optical absorption in visible light region due to the donor levels of the defects such as Vo‐Ti 3+ species. This work establishes a new method for preparing Vo defect contained TiO 2 catalysts.