Graphene-Based Single Crystal TiO2 Composites with Exposed Catalytic Interfaces for Efficient Photocatalytic Degradation

Three types of graphene–single crystal titanium dioxide composite (GR–TiO2SCs) were prepared using the hydrothermal method, employing TiF4 and graphite as raw materials with hydrofluoric acid serving as the morphology-directing agent. The phase composition and morphological features of the resultant composites were systematically characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and X-ray diffraction. These complementary characterization results clearly demonstrate that graphene and TiO2 single crystals have been successfully hybridized to form a well-defined heterostructure, rather than a simple physical mixture. Photocatalytic performances were evaluated by monitoring the photodegradation behaviors of methylene blue, rhodamine B, and methyl orange solutions under simulated light irradiation, with real-time concentration variations recorded by UV–visible absorption spectroscopy. The composite sample in which TiO2SCs were in situ grown and uniformly anchored onto graphene oxide substrates effectively suppressed the self-stacking and agglomeration of individual crystallites, thus delivering the best photocatalytic response. Increased exposure of the active catalytic interfaces of TiO2SCs was found to play a key role in elevating the overall photocatalytic activity. The hierarchical assembly protocol developed in this work provides a feasible pathway for the rational design of functional composites with controllable microstructures and tailored properties, which can be further extended to the development of advanced sensing materials.