Interlayer interaction in ultrathin nanosheets of graphitic carbon nitride for efficient photocatalytic hydrogen evolution

Two-dimensional graphitic carbon nitride (g-C3N4) nanosheets (CNNS) have attracted intense interest in photocatalysis, given their small thickness and high specific surface area favoring charge transfer and surface reactions. Herein, a facile strategy of breaking and following repolymerizing the heptazine units in bulk g-C3N4 (BCN) is developed to synthesize ultrathin CNNS with thickness of 1 nm in relatively high product yield (similar to 24%). The as-prepared 1 nm-thick CNNS show significantly enhanced photocatalytic performance for hydrogen evolution than BCN and even the 3 nm-thick CNNS acquired by thermal oxidation etching of BCN. It is evidenced that the disordered layer structure of the obtained ultrathin CNNS causes strong interlayer C-N interaction, tunneling electron transport between the C-N layers. Meanwhile, the broken in-plane C-N bonds create more unsaturated N sites in the 1 nm-thick CNNS, facilitating the electron excitation from the occupied states in g-C3N4 to its unoccupied states for water reduction reaction. (C) 2017 Elsevier Inc. All rights reserved.