Alkaline metal derived secondary thermal polymerization for superior thin g-C3N4 nanosheets with efficient photocatalytic performance

Abstract

The thermal polymerization controlled the thickness and composition of graphic carbon nitride (g-C3N4) to affect the photocatalytic performance. In this paper, potassium and sodium ions were firstly incorporated in bulk g-C3N4 prepared using melamine through a mechano-chemical pre-reaction. After a two-step thermal polymerization treatment at 500 and 550 °C, respectively, superior thin g-C3N4 nanosheets were created because K or Na ions implanted between g-C3N4 layers, in which activated cites were remained in the nanosheets. The results revealed that potassium or sodium ion doping revealed an important impact on the photocatalytic activity of g-C3N4. With an optimized K loading of 3%, the hydrogen evolution rate of potassium doped g-C3N4 superior thin nanosheets was 18.1 times of that of bulk g-C3N4. For the degradation of the degradation rate of Rhodamine B (Rh B), K-doped g-C3N4 sample revealed 3.8 times increase compared with pure g-C3N4. To indicate the role of alkaline metal ions, Na-doped samples were also used for H2 generation and Rh B degradation. Meanwhile, the hydrogen generation and Rh B degradation rate of sodium doped g-C3N4 nanosheets improved to 3.6 and 1.75 times higher than those of pure g-C3N4, respectively. The result suggested a mechano-chemical pre-treatment helped K and Na ions to improve the microstructure of g-C3N4 nanosheets and increase activated cites for photocatalysis.