Evidence of direct Z-scheme g-C3N4/WS2 nanocomposite under interfacial coupling: First-principles study

Abstract

Understanding is far from satisfactory on the high photocatalytic performances of g-C3N4/WS2 nanocomposites which are experimentally reported. Here, we investigate systematically for the first time the interfacial interactions and electronic properties of triazine-based g-C3N4/WS2 nanocomposites by first-principles calculations. The results confirm the reasonable existence of vdW interaction and typical direct Z-scheme mechanism based on the prominent interfacial binding energies and the energy level lineup at interface. Both energy band structures and work functions show that the conduction and valence band edges of the g-C3N4 layer are more negative than those of the WS2 layer after their intimate contact, respectively. Meanwhile, the interfacial interaction makes WS2 with negative charges and g-C3N4 with positive charges, forming a built-in electric field from g-C3N4 to WS2. Thus, photogenerated e––h+ pairs are separated to different places with prolonged lifetime and high redox potential. This work shines some lights on a direct Z-scheme mechanism for the g-C3N4/WS2 heterostructured photocatalyst.