Characterization of Type I/II g‑C₃N₄/MoS₂ van der Waals Heterostructures: A New Theoretical Insight

The charge transfer mechanism of the g-C₃N₄/MoS₂ heterojunction is still disputed. Some regard it as a type I pathway, some regard it as a type II pathway, and still some regard it as a Z-scheme pathway. Especially, the results obtained by density functional theory (DFT) calculations are not totally in agreement. Here, we constructed four g-C₃N₄/MoS₂ heterojunctions on the basis of the aperture alignment modes of g-C₃N₄ and MoS₂. Their morphology and photocatalytic activity were investigated via first-principles and excited state dynamics simulations. By systemically comparing the interfacial binding energy and electronic structure (e.g., band structure, electrostatic potential, and band edge positions) of g-C₃N₄/MoS₂ heterojunctions, we found that both type I and type II band alignment structures could be obtained. Moreover, the calculated lifetimes of interlayer photogenerated electrons and holes show that type II g-C₃N₄/MoS₂ tends to favor a general type II pathway rather than a Z-scheme pathway. This study could provide a deep understanding of the photocatalytic mechanism of g-C₃N₄/MoS₂ van der Waals heterostructures, which will be of great use for applications in photocatalysis.