Rational synthesis of ultrathin graphitic carbon nitride nanosheets for efficient photocatalytic hydrogen evolution

Graphitic carbon nitride (g-C3N4) nanosheets with unique structural and electronic properties have received much attention in photocatalysis, yet the direct synthesis of ultrathin g-C3N4 is still a big challenge. Herein, high-performance g-C3N4 nanosheets were firstly prepared by directly thermal calcination of the hydrothermally pretreated melamine as precursor. Multiple techniques were carried out to characterize the as-prepared samples. Results shown that the morphologies, microstructures, and physicochemical properties of as-synthesized samples are strongly depended on the hydrothermal temperature. The desired g-C3N4 nanosheets with a thickness of around 3 nm could be synthesized through an optimized 200 degrees C hydrothermal pretreatment. Compared to the bulk g-C3N4, the ultrathin g-C3N4 nanosheets possessed high specific surface area, large electronic band structure, and fast photoinduced electron-hole separation capability. As a consequence, the resultant nanosheets exhibited excellent visible-light-driven photocatalytic water splitting performance for hydrogen evolution (503 mmol h(-1) g(-1)), which is over 6 times higher than the bulk powder. This work highlights a feasible but simple strategy for the production of ultrathin graphite-like nanosheets and develops an efficient metal-free nanomaterial for application in energy conversion. (C) 2017 Published by Elsevier Ltd.