In-Situ construction of metal-free 1D/2D PCHO/PCN Z-scheme heterojunction towards enhanced photocatalytic H2 evolution.

• A novel Metal-free 1D/2D PCHO/PCN heterojunction is fabricated. • The PCHO/PCN heterojunction shows improved photocatalytic activity and stability. • The photogenerated carrier separation efficiency is significantly improved. • The superior PHE activity derives from the formed Z-Scheme mechanism. In order to achieve the sustainable production of hydrogen fuel, the heterogeneous photocatalysts with inimitable structure are always desired for the high-efficiency and stable H 2 production reaction from water splitting owing to the perfect structure–activity relationship. In this study, a novel metal-free one-dimensional/two-dimensional (1D/2D) heterojunction is constructed by a series of dissolution and diffusion, recrystallization and in-situ growth, and self-assembly process of 1-pyrene carboxaldehyde (PCHO) nanoribbons on the surface of polymeric carbon nitride (PCN) nanosheets. The obtained 1D/2D heterojunction can realize fast carrier transport along 1D nanoribbons to prevent the recombination of photogenerated carriers at the interface. Furthermore, the intrinsic Z-scheme reaction mechanism within the heterostructure also effectively inhibits electron-hole recombination and isolates the reduction and oxidation sites of the photocatalytic reaction. As a result, the dramatically enhanced photocatalytic hydrogen evolution (PHE) activity is achieved over the 1%-PCHO/PCN sample, the optimal PHE rate of which is approximately 5.4 times that of pure PCN. This work provides the deep insight into the design and exploitation of metal-free heterojunction with unique structure applied in the photocatalytic energy conversion field. [ABSTRACT FROM AUTHOR]