Self-assembly synthesis of phosphorus-doped tubular g-C3N4/Ti3C2 MXene Schottky junction for boosting photocatalytic hydrogen evolution

Establishing highly effective charge transfer channels in carbon nitride (g-C3N4) to enhance its photocatalytic activity is still a challenging issue. Herein, the delaminated 2D Ti3C2 MXene nanosheets were employed to decorate the P-doped tubular g-C3N4 (PTCN) for engineering 1D/2D Schottky heterojunction (PTCN/TC) through electrostatic self-assembly. The optimized PTCN/TC exhibited the highest hydrogen evolution rate (565 mmol h-1 g-1), which was 4.3 and 2.0-fold higher than pristine bulk g-C3N4 and PTCN, respectively. Such enhancement may be primarily attributed to the phosphorus heteroatom doped and unique structure of 1D/2D g-C3N4/Ti3C2 Schottky heterojunction, enhancing the light-harvesting and charges' separation. One-dimensional pathway of g-C3N4 tube and built-in electric field of interfacial Schottky effect can significantly facilitate the spatial separation of photogenerated charge carriers, and simultaneously inhibit their recombination via Schottky barrier. In this composite, metallic Ti3C2 was served as electrons sink and photons collector. Moreover, ultrathin Ti3C2 flake with exposed terminal metal sites as a co-catalyst exhibited higher photocatalytic reactivity in H2 evo-lution compared to carbon materials (such as reduced graphene oxide). This work not only proposed the mechanism of tubular g-C3N4/ Ti3C2 Schottky junction in photocatalysis, but also provided a feasible way to load ultrathin Ti3C2 as a co-catalyst for designing highly efficient photocatalysts. (c) 2021 Institute of Process Engineering, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Com-munications Co., Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Automated summary

Delaminated 2D Ti3C2 MXene nanosheets were used to decorate P-doped tubular g-C3N4, forming a 1D/2D Schottky heterojunction. The optimized composite showed significantly enhanced photocatalytic activity for hydrogen evolution compared to pristine g-C3N4 and PTCN. The enhancement was attributed to the phosphorus doping, unique structure of the heterojunction, and the separation and inhibition of charge carriers. Metallic Ti3C2 acted as an electron sink and photon collector, while the ultrathin Ti3C2 flake served as a co-catalyst for higher reactivity.