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-C3N4) 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-C3N4 by high temperature calcination to accelerate the charges transfer between both interlayers and intralayer of g-C3N4. The results showed that the hydrogen production rate of g-C3N4 modified simultaneously by nitrogen defects and potassium ions reaches 1722.4 μmol·g−1·h−1, which is 8 times that of pristine g-C3N4. 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-C3N4 and a possible mechanism was proposed.