Graphitic carbon nitride nanosheets anchored with BiOBr and carbon dots: Exceptional visible-light-driven photocatalytic performances for oxidation and reduction reactions.

The aim of this work is the fabrication of very efficient visible-light-driven photocatalysts through anchoring carbon dots and BiOBr over nanosheets of graphitic carbon nitride. Hence, a series of g-CN nanosheets/Carbon dots/BiOBr (denoted as CNNS/CDs/BiOBr) nanocomposites with different amounts of BiOBr were synthesized by refluxing route. The resultant photocatalysts were characterized by XRD, EDX, SEM, TEM, HRTEM, AFM, XPS, FT-IR, UV-vis DRS, TGA, BET, and PL instruments. Among the photocatalysts, the CNNS/CDs/BiOBr (20%) nanocomposite exhibited the highest photocatalytic performance for degradations of RhB, MB, and MO under visible light, which is about 129, 29.8, and 20.5 times as superior as the CN powder, respectively. Also, photoreduction of Cr(VI) to Cr(III) over the ternary nanocomposite with 20% of BiOBr showed high photoactivity, which was 21.7-folds higher than that of the pristine CN. Reactive species trapping experiments revealed that superoxide anion radicals and hydroxyl radicals played significant role in degradation reaction of RhB. The utilized photocatalyst was recycled with negligible loss in the activity, which is important in photocatalytic processes. Finally, by studying the electrochemical behavior, the band alignments of the semiconductors were obtained and the preliminary mechanism was suggested as a direct Z-scheme system for the enhanced interfacial charge separation and transfer, which leads to the exceptional photocatalytic performance.