Ultrathin porous graphitic carbon nitride from recrystallized precursor toward significantly enhanced photocatalytic water splitting

Structure regulation (including electronic structure and morphology) for graphitic carbon nitride (g-C₃N₄) is an effective way to promote the photocatalytic activity. Herein, an ultrathin porous g-C₃N₄ (BCN-HT100) was synthesized by calcination of biuret hydrate. Hydrothermal treatment induced biuret recrystallization to form biuret hydrate precursor with regular morphology and large crystal size, thus promoting the polymerization of melem to form g-C₃N₄ network. Accordingly, BCN-HT100 possessed ultrathin nanosheet structure, higher polymerization degree, larger surface area and more pores than biuret-derived g-C₃N₄. BCN-HT100 behaved high-efficiency photocatalytic H₂-productin activity with an apparent quantum yield (AQY) of 58.7% at 405 nm due to the enhanced utilization efficiency for photo-generated charge carriers and abundant reactive sites. Furthermore, Pt-NiCo₂O₄ dual cocatalysts were employed on BCN-HT100 for achieving photocatalytic overall water splitting, and the AQY reached 4.9% at 405 nm. This work provides a meaningful reference to designing g-C₃N₄ to achieve efficient solar energy conversion into hydrogen.