Crystallinity and thickness modulation of polymeric carbon nitride by dual-functional lithium ions for boosting photocatalytic H₂O₂ production

The production of H₂O₂ through photocatalysis is a green and economical alternative to conventional methods. Here, we prepared poly (heptazine imide) (PHI) phase polymeric carbon nitrides (Li-PCN) by facile lithium ions-assistant post-condensation method. Lithium ions not only can optimize condensation process, but also exfoliate and tailor PCN, resulting in higher crystallinity, excellent photo-absorption range, which enhance surface adsorption of dioxygen, and increase the number of electron transfers in the reaction. Based on the above advantages, the Li-PCN exhibits excellent photocatalytic H₂O₂ (2680 μmol g^-1h⁻¹) production activity under visible light, which was about 35.7 times higher than that of PCN. Besides, we have increased the concentration of H₂O₂ through changing reaction solution to a final content of 4.8613 mM. Furtherly, the homemade H₂O₂ production was used to degrade methyl orange pollution by Fenton reaction. This work provides a new synthetic route to PHI and highlights the function of lithium ions, which can promote the development of more efficient photocatalysts for H₂O₂ production.