Graphene Quantum Dots Decorated Titania Nanosheets Heterojunction: Efficient Charge Separation and Enhanced Visible-Light Photocatalytic Performance

Graphical Joining the dots : Oxygen-functionalized graphene quantum dots (GQDs) are encapsulated into flocculated flexible titania nanosheets (TNSs) to form GQDs/TNSs composite photocatalyst through a facile electrostatic flocculation route. GQDs/TNSs exhibit high photocatalytic activity for the degradation of Rhodamine B under visible light irradiation owing to promoted charge separation. Titania nanosheets (TNSs) are of importance for photocatalytic application owing to the unique two-dimensional (2D) morphology, high crystallinity and plentiful surface charge. However, the large band gap prohibited the efficient utilization of sun light. Herein, we employed graphene quantum dots (GQDs) as green photocatalytic promoter to decorate TNSs during the electrostatic flocculation. The obtained GQDs/TNSs heterojunction was systematically characterized, and the results demonstrated that the composite exhibited an intimate coupling of GQDs and TNSs, a markedly visible light absorption and therefore the enhanced separation efficiency of photogenerated charges. This composite photocatalyst shows enhanced photocatalytic performance for the photodegradation of Rhodamine B (RhB) under visible light irradiation in comparison with pure restacked TNSs (rs-TNSs) and GQDs. Furthermore, this composite exhibited a superior reusability, and a high degradation ratio about 90 % was still achieved in the 5 th cycle. Moreover, a possible mechanism was proposed and superoxide radicals, holes and hydroxyl radicals were determined as the active species.