Engineering nanoscale p-n junction via the synergetic dual-doping of p-type boron-doped graphene hybridized with n-type oxygen-doped carbon nitride for enhanced photocatalytic hydrogen evolution

In this study, an effective 2D-2D heterojunction composite was formulated by hybridizing oxygen doped graphitic carbon nitride (O-gC₃N₄) with boron doped reduced graphene oxide (B-rGO) using a combined sonication-assisted electrostatic self-assembly approach. Pristine gC₃N₄ possesses a negative surface charge, which later transforms into a positive charge upon doping with elemental oxygen. This reversal of surface charge, which occurred on top of doping, established the opportune electrostatic coupling of positively charged O-gC₃N₄ and negatively charged B-rGO. Moreover, the concerted dual doping of both O-gC₃N₄ and B-rGO, which exhibited n-type and p-type conductivity, respectively, allowed the construction of a nanoscale p-n heterojunction system at the interface, warranting a more effective and rapid charge separation and in turn bolstering the photocatalytic hydrogen performance. In particular, the optimal loading content of B-rGO was found to be 2 wt% with a corresponding H₂ production rate of 1639 μmol g^-1 after 6 h, which is a remarkable 4-fold photocatalytic improvement as compared to that of O-gC₃N₄. In brief, this study highlights that the dual doping of both gC₃N₄ and rGO and their hybridization present a powerful strategy to increase the photoactivity of the composite since doping could remarkably modulate their interaction at the heterointerface.