MoSSe/Hf(Zr)S 2 heterostructures used for efficient Z-scheme photocatalytic water-splitting.

Direct Z-scheme water-splitting is a promising route to enhancing the photocatalytic performance due to the effective separation of photogenerated carriers while simultaneously preserving the strong oxidation activity of holes and reduction activity of electrons. In this work, the MoSSe/XY ₂ (X = Hf, Zr; S, Se) heterostructures (HSs) with different contacts are proposed for Z-scheme photocatalytic water-spitting by first principles calculation. The separation of photogenerated carriers for HfSe ₂ /SMoSe and ZrSe ₂ /SMoSe HSs is limited by the type-I band alignment, while the hydrogen production ability of HfSe ₂ /SeMoS and ZrSe ₂ /SeMoS HSs is limited by the lower conduction band edge positions relative to the water reduction potential. The HfS ₂ /SMoSe, HfS ₂ /SeMoS, ZrS ₂ /SMoSe, and ZrS ₂ /SeMoS HSs are direct Z-scheme water-splitting photocatalysts with the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) occurring at the Hf(Zr)S ₂ layer and MoSSe layer, respectively. More excitingly, the S (or Se) vacancies effectively lower the HER overpotentials. Besides, the solar-to-hydrogen efficiencies are 6.1%, 5.9%, 6.4%, and 6.3% for HfS ₂ /SMoSe, HfS ₂ /SeMoS, ZrS ₂ /SMoSe, and ZrS ₂ /SeMoS HSs, respectively. This work paves the way for designing highly efficient overall water-splitting photocatalysts using 2D materials.