Gas exfoliation of graphitic carbon nitride to improve the photocatalytic hydrogen evolution of metal-free 2D/2D g-C3N4/graphdiyne heterojunction

Abstract Metal-free photocatalysts have received increasing attention as nonmetal elements are abundant in the earth and friendly to the environment. Graphitic carbon nitride (g-C3N4) as a typical two-dimensional (2D) metal-free photocatalysts for water splitting has attracted increasing interest due to its economic production and environmentally friend features. However, the high photocarriers recombination rate constraint its catalytic activity. Combining the single- or few-layered g-C3N4 nanosheets with other 2D functional materials to form efficient metal-free heterojunction photocatalysts is one of the effective strategies to improve the photocarriers separation. Herein, we introduce a simple and efficient method to scalable preparation few-layered g-C3N4 nanosheets using gas exfoliation of bulk g-C3N4 in liquid nitrogen. Then we introduce the g-C3N4 nanosheets into construct a 2D/2D heterojunction of g-C3N4/graphdiyne by π-π interaction, where graphdiyne (GDY) as a new 2D carbon allotrope, has excellent holes transfer nature. We find that the 2D/2D g-C3N4/GDY photocatalyst with 1% GDY is the optimum condition, with the highest H2 evolution rate of 454.28 μmol h−1. The superior photocatalytic performance may be attributed to the excellent photocarriers separation in g-C3N4 under the built-in field, where GDY can rapid transport holes from g-C3N4 to the sacrificial agents.