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-CN) is an effective way to promote the photocatalytic activity. Herein, an ultrathin porous g-CN (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-CN network. Accordingly, BCN-HT100 possessed ultrathin nanosheet structure, higher polymerization degree, larger surface area and more pores than biuret-derived g-CN. BCN-HT100 behaved high-efficiency photocatalytic H-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-NiCoO 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-CN to achieve efficient solar energy conversion into hydrogen.