Graphene promoted triphasic N/Ti3+-TiO2 heterostructures: In-situ hydrothermal synthesis and enhanced photocatalytic performance

Graphene promoted triphasic N/Ti3+-TiO2 (GNTT) heterostructures with different weight addition ratios of graphene have been assembled by a facile in-situ hydrothermal treatment of TiN and graphene oxide. The obtained GNTT photocatalysts are characterized by a collection of techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), UV–visible spectroscopy, and photoluminescence (PL), etc. It is demonstrated that graphene modified N/Ti3+ codoped TiO2 with ternary phases mixture of brookite, anatase and rutile can be obtained. Furthermore, the GNTT heterostructure photocatalysts exhibit an enhanced photoactivity for photocatalytic degradation of methyl blue, levofloxacin, and rhodamine B as compared with TiO2, N-doped TiO2, and N/Ti3+ codoped TiO2 (NTT). The reason for the improved photoactivity can be listed as follows: i) N and Ti3+ doping can severally form N2p impurity level above valance band (VB) and local states below the conduction band (CB) of TiO2, which contribute to the visible light response of TiO2; ii) the ternary heterophase junction can efficiently transfer and separate photogenerated electron-hole pairs; iii) graphene acts as an electron reservoir to trap and transport the electrons photogenerated from TiO2. The synergistic effect of these factors accounts for the photoactivity advancement of GNTT photocatalysts. This study develops a novel approach to improve the visible light utilization of TiO2 and facilitates their applications in the environment and energy issues.