Synergistic effect of n-π electronic transitions in porous ultrathin graphitic carbon nitride nanosheets for efficient photocatalytic hydrogen production

Porous twisted graphitic carbon nitride nanosheets with n-π* electronic transitions were successfully synthesized to boost photocatalytic hydrogen production. [Display omitted] •Porous twisted GCN nanosheets with n-π* electronic transition were successfully synthesized.•The strategy not only expands optical absorption capacity but also activates the n-π* electronic transition.•Such the unique structure of PCN-0.3 extends the light absorption edge to 650 nm, which significantly increases the separation of photogenerated charges.•The photocatalytic H2 productionrate by PCN-0.3 is 8.8 folds higher than that of pristine GCN. The visible light absorption capacity and active sites of graphitic carbon nitride (GCN) are crucial roles for photocatalytic hydrogen (H2) production. However, the fabrication of ultrathin GCN nanosheets with enhanced light absorption via n-π* electronic transitions remain challenging. Here, we report on the successful preparation of porous ultrathin GCN nanosheets with activating n-π* electronic transitions simultaneously by microwave heating the mixture of urea and ammonium chloride (NH4Cl) compression strategy. Such the unique structure of GCN is composed of a curved porous thin layer and has numerous wrinkles that not only largely expand visible light absorption range to ∼ 650 nm but also significantly enhance the unmber of active sites and the mobility of photoexcited charges. The highest photocatalytic H2 production rate reached 99.1 μmol h−1 under visible light irradiation (λ > 420 nm), which is 8.8 folds higher than that of pristine GCN (11.2 μmol h−1). This work presents a promising and effective strategy for the engineering of GCN, which fully utilizes n-π* electronic transitions to largely expand the visible light absorption while enhancing the active sites.