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 μmol 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 evolution 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.