Construction of 2D/2D BCNS/Ti3C2 heterojunction with boron-doped g-C3N4 and Ti3C2 MXene for enhanced photocatalytic water splitting

Graphitic carbon nitride (g-C3N4) has attracted great interest in photocatalytic water splitting. However, the poor photogenerated charge carriers transfer and the insufficient driving force for oxygen evolution reaction limit its practical application. In this work, boron-doped g-C3N4 nanosheets (BCNS) have been synthesized by calcining a mixture of g-C3N4 and NaBH4. The synthesized BCNS were then combined with Ti3C2 MXene using electrostatic self-assembly to construct a 2D/2D BCNS/Ti3C2 heterojunction. The resultant BCNS retained the original framework of g-C3N4, while the optimized band structure of BCNS induced prominently enhanced visible light absorption, accelerated charge carriers separation, and the increased driving force for water oxidation compared to pure g-C3N4. Density functional theory further proved that BCNS can enhance the driving force for photocatalytic O2 evolution. Moreover, the construction of 2D/2D face-to-face BCNS/Ti3C2 heterojunction was carried out to further enhance photocatalytic performance due to the intimate contact interface and the accelerated separation and transfer of photogenerated charge carriers. As a result, the 2D/2D BCNS/Ti3C2 hetrojunction exhibited a dramatically improved photocatalytic water-splitting performance compared to pristine g-C3N4. This integrated engineering strategy, involving non-metal element doping and 2D/2D heterojunction construction, might provide a unique paradigm for the rational design of efficient photocatalysts for photocatalytic water splitting.