Preparation of visible light photocatalytic graphene embedded rutile titanium(IV) oxide composite nanowires and enhanced NOx removal

The quest for developing highly efficient TiO₂-based photocatalysts is continuing and, in particular, evolving a new strategy is an important aspect in this regard. In general, much effort has been devoted to the anatase TiO₂ modifications, despite there being only a few recent studies on rutile TiO₂ (rTiO₂). To the best of our knowledge, studies on the preparation and characterization of the photocatalysts based on the intentional inclusion of graphene (G) into rTiO₂ nanostructures have not been reported yet. Herein, we develop a new type of TiO₂-based photocatalyst comprising of G included pure rTiO₂ nanowire (abbreviated as rTiO₂(G) NW) with enhanced visible light absorption capability. To prepare rTiO₂(G) NW, the G incorporated titanate electrospun fibers were obtained by electrospinning and subsequently heat treated at various temperatures (500 to 800 °C). Electrospinning conditions were optimized for producing good quality rTiO₂(G) NW. The rTiO₂(G) NW and their corresponding samples were characterized by appropriate techniques such as X-ray diffraction (XRD), scanning electron microscopy, high-resolution transmission electron microscopy and UV-vis diffuse reflectance spectroscopy to ascertain their material characteristics. XRD results show that the lattice strain occurs upon inclusion of G. We present here the first observation of an apparent bandgap lowering because of the G inclusion into TiO₂ NW. While anatase TiO2 NW exhibited poor visible light photocatalysis towards NOx removal, the rTiO₂(G) NW photocatalyst witnessed a significantly enhanced (~67%) photocatalytic performance as compared to anatase TiO₂(G) NW. We concluded that the inclusion of G into rTiO₂ nanostructures enhances the visible light photoactivity. A plausible mechanism for photocatalysis is suggested.