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

Abstract 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/g), 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, 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.