Direct Z-scheme construction of g-C3N4 quantum dots / TiO2 nanoflakes for efficient photocatalysis

[Display omitted] •TiO2 nanoflakes/g-C3N4 QDs were prepared by a facile calcination process.•g-C3N4 QDs were intimately hybridized with the giant TiO2 nanoflakes.•Mechanism of charge transfer and separation in Z-scheme heterojunction discussed.•High photocatalytic degradation and H2 evolution activity were realized. The rapid recombination rate of photogenerated carriers in TiO2 has been limiting the photocatalytic performance. Herein, TiO2 thin flakes modified by g-C3N4 quantum dots (g-C3N4 QDs) were fabricated successfully through a facile thermal treatment of restacked single-layer nanosheets of Ti1.73O41.07- in the presence of urea as a source of g-C3N4 QDs. Characterizations showed that g-C3N4 QDs with a size of ~10 nm were homogeneously deposited on the surface of TiO2 thin flakes. Quenching experiments of •OH radicals and the detection of radicals by EPR certified the direct Z-scheme heterojunctions between g-C3N4 QDs and TiO2 flakes. The TiO2 nanoflakes/g-C3N4 QDs hybrid exhibited excellent activity for the photocatalytic hydrogen evolution from a methanol solution and the degradation of RhB due to the enhanced charge separation efficiency and improved light absorption in the direct Z-scheme heterojunctions. This study demonstrates that the rational design of heterojunction is effective for attaining the superior photocatalytic performance.