Two-dimensional SnS2/ZrSi2N4 van der Waals heterojunction as a spontaneously enhanced hydrogen evolution photocatalyst

Photocatalytic water splitting driven by photon excitation is a promising method for generating clean energy. This study focuses on designing a two-dimensional van der Waals heterojunction photocatalyst, created by vertically stacking SnS2 and ZrSi2N4. The intrinsic mechanisms and hydrogen evolution potential of this system were systematically investigated using first-principles calculations. The results demonstrate that the SnS2/ ZrSi2N4 heterojunction is a type II heterojunction with an indirect band gap, and the staggered energy bands effectively separate the photogenerated carriers and enhance photocatalytic efficiency. Additionally, the near- ideal band gap of 2.30 eV ensures good light absorption while providing sufficient driving force for water decomposition. The band-edge positions of the heterojunction span the redox potential of water, which means that, in aqueous solutions with a pH range of 0-4, the external potential generated by photogenerated electrons is adequate to spontaneously drive hydrogen evolution through water splitting. Simultaneously, the Gibbs free energy (Delta G =-0.11 eV) being close to zero indicates that this heterojunction can effectively facilitate the hydrogen evolution reaction (HER). Furthermore, the exceptional electron mobility (2048.38 cm2 & sdot;V- 1 & sdot; S- 1 ), hole mobility (4299.49 cm2 & sdot;V- 1 & sdot; S- 1 ), and solar-to-hydrogen conversion efficiency of up to 17.92 % underscore its immense potential as an effective photocatalyst. This work offers innovative approaches for achieving efficient photocatalytic water decomposition, advancing the development of clean energy solutions.