Microstructure driven charge carrier separation in superior thin g-C3N4 nanosheets towards enhanced photocatalytic activities

Abstract

The performance of graphic carbon nitride (g-C3N4) depended strongly on solar energy harvesting and photogenerated charge carrier separation and transfer. Defect engineering (local component and crystallinity adjustment) helps g-C3N4 to improve photocatalytic activity. In this paper, superior thin g-C3N4 nanosheets with typical microstructures were created using a two-step thermal polymerization at high temperature by adjusting precursors. g-C3N4 nanosheets obtained using melamine revealed fine crystallinity compared with that created using dicyandiamide even though related flat microstructure observed for two samples. In contrast, a wrinkled microstructure with self-assembled amorphous/crystalline junctions was created by urea. Interestingly, the wrinkled one revealed the fastest degradation for RhB which was degraded over within 5 min and a high H2 generation rate of 3473 μmol·g−1·h−1 compared with other samples. This performance is ascribed that wrinkle ultra-thin g-C3N4 nanosheets with amorphous-crystalline junctions significantly improved light harvesting ability and photogenerated carrier separation and transport efficiencies. Furthermore, almost no H2 was generated using molten-salt (NaCl and KCl) assisted porous g-C3N4 nanosheets. These results suggest that increased active sites generated by defect engineering were crucial for the photocatalytic performance of g-C3N4. The detailed discussion on microstructure formation provides an important platform for the construction of highly efficient g-C3N4 based photocatalysts.