Graphene and TiO2 co-modified flower-like Bi2O2CO3: A novel multi-heterojunction photocatalyst with enhanced photocatalytic activity

In this paper, graphene (GR) and titania co-modified flower-like Bi2O2CO3 multi-heterojunction composite photocatalysts were prepared by a simple and feasible two step hydrothermal process. The prepared samples were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectrometry (DRS), photoluminescence (PL), N2 adsorption–desorption isotherm, and photo-induced current. The photocatalytic activity was investigated by the degradation of MO under UV light irradiation. The as prepared multi-heterojunction GR/Bi2O2CO3/TiO2 composites exhibited much higher photocatalytic activity than pure Bi2O2CO3, TiO2 and GR–Bi2O2CO3. The higher performance of GR/Bi2O2CO3/TiO2 can be ascribed to the formation of multi-heterojunctions, which promote the effective separation of photo-induced electron–hole pairs. Moreover, the higher photocatalytic activity can also be ascribed to the high surface area of GR and TiO2, which offers more active sites for the photodegradation reaction. Furthermore, the photocatalytic activity of GR/Bi2O2CO3/TiO2 remained without striking decrease after five cycles, which indicates the excellent stability of GR/Bi2O2CO3/TiO2 composites. This work would pave a way to the design of high efficient multi-heterojunction photocatalysts.