Heterojunctions in g-C3N4/TiO2(B) nanofibres with exposed (001) plane and enhanced visible-light photoactivity

The formation of heterojunctions is an efficient strategy to extend the light response range of TiO2-based catalysts to the visible light region. In addition to the bandgap edge match between the narrow bandgap semiconductors and the TiO2 substrate, a stable phase interface between the sensitiser and TiO2 is crucial for the construction of heterojunctions, since it acts as a tunnel for the efficient transfer of photogenerated charges. Herein, the coincidence site density (1/Sigma) of graphite-like carbon nitride (g-C3N4) nanoflakes and two types of TiO2 nanofibres [anatase and TiO2(B)] was calculated by near coincidence site lattice (NCSL) theory. It was found that the coincidence site density of g-C3N4 and TiO2(B) nanofibre with an exposed (001) plane is 3 times of that of the g-C3N4 and anatase nanofibre with exposed (100) plane. This indicated that the g-C3N4 nanoflakes are more favoured to form stable heterojunctions with TiO2(B) nanofibres. As expected, a stable phase interface was formed between the plane of (22-40) of g-C3N4 and the plane (110) of TiO2(B) which had same d-spacing of 0.35 nm and the same orientation. Under visible light irradiation, the photogenerated electrons could efficiently migrate to the TiO2(B) nanofibres from the g-C3N4 through the heterojunctions. So the g-C3N4/TiO2(B) system exhibited better photodegradation ability for sulforhodamine B (SRB) dye than the g-C3N4/anatase system, although the photoactivity of the anatase nanofibres was much better than that of the TiO2(B) nanofibres.