Sustainable one-step synthesis of nanostructured potassium poly(heptazine imide) for highly boosted photocatalytic hydrogen evolution

Regulating bulk polymeric carbon nitride (PCN) into nanostructured PCN (NPCN) has long been proved effective to improve its photocatalytic activity, which is applicable to crystalline carbon nitride: potassium poly (heptazine imide) (K-PHI). Currently, simplifying the synthesis of nanostructured K-PHI (NK-PHI) is challenging and has drawn widespread attention. This work demonstrated the one-step concise and sustainable synthesis of NK-PHI by a steam-assisted method. The NK-PHI exhibited a highly boosted visible-light photocatalytic hydrogen evolution activity, which is 38.4, 4.4 and 3.4 times to that of PCN, NPCN and K-PHI. The improvement of photocatalytic activity mainly benefitted from increased active sites and highly facilitated photoinduced charges transfer and separation. Moreover, the sustainability of this approach was proved by recycling the structure-directing agents (KCl) and steam source (Mg(OH)2) to repeatedly synthesize high-quality NK-PHI.