Porous sheet-like carbon nitride with high porosity for efficient visible-light-driven hydrogen evolution reaction

Carbon nitride (CN) has emerged as a promising metal-free photocatalyst; however, its practical application remains severely hindered by insufficient active sites and rapid charge recombination. Herein, we report a facile three-step synthetic strategy to construct porous sheet-like CN (PSCN) with high porosity. Specifically, urea and melamine were dissolved in hot water (100 °C) and evaporated to dryness under stirring to afford a homogeneous precursor, which was subsequently calcined in a muffle furnace to form tubular CN (TCN). A further thermal treatment in air using a tube furnace then triggered the structural transformation from the tubular to porous sheet-like morphology, thereby endowing the catalyst with an enlarged specific surface area, abundant porous channels, and efficient charge separation. Benefiting from these structural merits, the as-obtained PSCN exhibits significantly enhanced photocatalytic hydrogen evolution activity under visible light irradiation (λ ≥ 420 nm), achieving a H₂ production rate of 1278 µmol g^-1 h^-1, which is about 5 times higher than that of TCN. This work offers a simple and scalable approach to tailor the morphology and electronic structure of CN, thus holding great promise for high-performance photocatalytic energy conversion.