Collaborative enhancement in charge separation and photon harvesting of 2D/2D heterojunction photocatalysts by horizontal loading of SnS₂ nanosheets on g-CN films

Highly efficient photocatalysts based on van der Waals 2D type heterojunctions were fabricated by horizontal loading of ultrathin hexagonal SnS₂ nanosheets on the surface of a g-CN film via spin coating followed by annealing treatment. As evidenced by micrographs and further confirmed by the first-principles calculations, a large contact area was realized in the heterojunction interface by synthesizing sheet-like structures consisting of these two semiconductors, facilitating considerably enhanced charge separation under visible light illumination. In particular, the g-CN/SnS₂ heterojunction annealed at 400 °C favors the bonding of Sn–N and C–S resulting in reduction of the bandgap by lowering the conduction band edge and in turn yields ideal electronic structures for photoelectrochemical hydrogen production. Such a heterojunction exhibits significantly improved photoinduced current density in sharp contrast to its isolated parent parts, namely g-CN and SnS₂, by a factor of 5 and 4, respectively. The photocurrent response, together with Mott–Schottky plots and photoluminescence spectroscopy, demonstrates the photo synergetic effect of the g-CN/SnS₂ heterojunction which strongly boosts the photoinduced interfacial charge transfer, enhancing the charge separation during the reaction and lowering the recombination rate.