Photocatalytic enhancement mechanisms for novel g-C₃N₄/PVK nanoheterojunction

The interactions between monolayer graphitic carbon nitride (g-C₃N₄) and conjugated polymer poly(9-vinylcarbazole) (PVK) have been explored. We investigated the enhanced photocatalytic mechanisms for the novel g-C₃N₄/PVK nanoheterojunction covering the state-of-the-art of DFT by performing rigorous DFT calculations combined with van der Waals corrections (GGA + vdW). The calculated band alignment between g-C₃N₄ monolayer and PVK monomer clearly reveals that the conduction band minimum and the valence band maximum of g-C₃N₄ monolayer are higher than those of the conjugated polymer PVK. This predicted band alignment ensures the photogenerated electrons easily migrate from the g-C₃N₄ monolayer to the PVK monomer, and will lead to high hydrogen-evolution reaction activity. The charge transfer between g-C₃N₄ monolayer and PVK results in a polarized field within the interface region, which will benefit the separation of photogenerated carriers. The calculated density of electronic states, Lowdin charge transfer and charge density difference certify that this proposed layered nanoheterojunction is an excellent light-harvesting semiconductor. These findings indicate that the conjugated polymer PVK is a promising candidate as a non-noble metal co-catalyst for g-C₃N₄ photocatalysis. It also provides useful information for understanding the observed enhanced photocatalytic mechanisms in experiments.