Heterojunctions in g-C sub(3)N sub(4)/TiO sub( 2)(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 TiO sub(2)-based catalysts to the visible light region. In addition to the bandgap edge match between the narrow bandgap semiconductors and the TiO sub(2) substrate, a stable phase interface between the sensitiser and TiO sub(2) 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/ capital sigma ) of graphite-like carbon nitride (g-C sub(3)N sub(4)) nanoflakes and two types of TiO sub(2) nanofibres [anatase and TiO sub(2)(B)] was calculated by near coincidence site lattice (NCSL) theory. It was found that the coincidence site density of g-C sub(3)N sub(4) and TiO sub(2)(B) nanofibre with an exposed (001) plane is 3 times of that of the g-C sub(3)N sub(4) and anatase nanofibre with exposed (100) plane. This indicated that the g-C sub(3)N sub(4) nanoflakes are more favoured to form stable heterojunctions with TiO sub(2)(B) nanofibres. As expected, a stable phase interface was formed between the plane of (22-40) of g-C sub(3)N sub(4) and the plane (110) of TiO sub(2)(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 TiO sub(2)(B) nanofibres from the g-C sub(3)N sub(4) through the heterojunctions. So the g-C sub(3)N sub(4)/TiO sub( 2)(B) system exhibited better photodegradation ability for sulforhodamine B (SRB) dye than the g-C sub(3)N sub(4)/anatase system, although the photoactivity of the anatase nanofibres was much better than that of the TiO sub(2)(B) nanofibres.