The synergistic effect of potassium ions and nitrogen defects on carbon nitride for enhanced photocatalytic hydrogen evolution.

Ion doping is an effective method to improve the photocatalytic activity of graphitic carbon nitride (g-C 3 N 4) by providing a photocarriers transfer channel. But limited by the bonds in heptazine rings, photoelectrons are still trapped in the structure. Therefore, both potassium ions and nitrogen defects were successfully introduced into g-C 3 N 4 by high temperature calcination to accelerate the charges transfer between both interlayers and intralayer of g-C 3 N 4. The results showed that the hydrogen production rate of g-C 3 N 4 modified simultaneously by nitrogen defects and potassium ions reaches 1722.4 μmol·g−1·h−1, which is 8 times that of pristine g-C 3 N 4. Based on various characterization techniques and DFT calculations, we attributed the enhanced photocatalytic hydrogen evolution to the improved light adsorption, more delocalized HOMO-LUMO, and stronger interlayer interactions. This work will provide a promising way to enhance photocatalytic hydrogen evolution of g-C 3 N 4 and a possible mechanism was proposed. Synopsis. This work developed a valid and efficient strategy to modify graphitic carbon nitride and significantly enhance photocatalytic hydrogen evolution. [Display omitted] • K@C 3 N 4-x was successfully synthesized by a simple polymerization and nitric acid treatment. • Hydrogen evolution rate of K@C 3 N 4-x is approximately 8 times higher than that of pristine carbon nitride. • Horizontal and vertical charge transfer channels were constructed to improve the photocatalytic performance of g-C 3 N 4. [ABSTRACT FROM AUTHOR]