TiO₂/Graphitic Carbon Nitride Nanosheets for the Photocatalytic Degradation of Rhodamine B under Simulated Sunlight

Surface-fluorinated ultrathin anatase TiO2 nanosheets with exposed (001) crystal planes were synthesized via a relatively low temperature solvothermal route. These two-dimensional (2D) TiO2 nanosheets demonstrated higher photocatalytic activity for degrading Rhodamine B (RhB) under simulated sunlight illumination than the corresponding sample with less fluorine ions (F–) content, which indicates the positive effect of F– on the enhanced photocatalytic performance of TiO2 nanosheets. Furthermore, 2D/2D TiO2/g-C3N4 nanosheet heterojunctions were fabricated through a solvent evaporation process. The photocatalysis test showed that TiO2/g-C3N4 exhibited higher photocatalytic performance for degrading RhB under simulated solar light illumination than pure g-C3N4 and TiO2 nanosheets. Based on free radical trapping experiments, superoxide radicals (·O2–) and photoinduced holes (h+) were determined to be the predominant active species for photodegrading RhB. A direct Z-scheme charge transfer mechanism is proposed to understand the enhanced photocatalytic activity in TiO2/g-C3N4 nanosheet heterojunctions.