Highly efficient solar photocatalytic degradation of a textile dye by TiO2/graphene quantum dots nanocomposite.

Herein, two sunlight responsive photocatalysts including TiO2 nanoparticles (NPs) and TiO2/graphene quantum dots (GQDs) nanocomposite for degrading a textile dye, Reactive Black 5 (RB5), were prepared. The results showed that 100% of 50 ppm RB5 could be degraded by TiO2 NPs and TiO2/GQDs within 60 and 30 min sunlight irradiation, respectively. Hence, much better photocatalytic activity in degradation of RB5 was achieved by TiO2/GQDs under sunlight irradiation compared with pure TiO2 NPs due to its lower band gap (2.13 eV) and electron/hole recombination rate. The photocatalytic degradation mechanism of RB5 by TiO2 NPs was elucidated by adding some scavengers to the solution. The main reactive species contributing to RB5 degradation were surface hydroxyl radicals. The first-order solar degradation rate constant of RB5 for TiO2/GQDs is greater than that of TiO2 NPs under sunlight illumination.