Alkali metal-modified crystalline carbon nitride for photocatalytic nitrogen fixation.

Alkali metal chlorides have been used as molten salts for further preparing crystalline carbon nitride, but the effect of alkali metal types on the properties of crystalline carbon nitride has not been systematically studied. Therefore, in this paper, a series of crystalline carbon nitride samples doped with different alkali metals were successfully prepared using LiCl-KCl, KCl-NaCl, LiCl-KCl-NaCl and LiCl-NaCl as molten salts: LK-HTCN (Li-K co-doping), KN-HCN (K-Na co-doping), LKN-HTCN (Li-K-Na co-doping) and LN-HTCN (Li-Na co-doping). The experimental results show that KN-HCN contains only the heptazine unit structure, while the other samples contain heptazine and triazine unit structures.