Direct Z-scheme β-SnSe/HfS2 heterostructure for photocatalytic water splitting: High solar-to-hydrogen efficiency and excellent carrier mobility

Constructing directly stacked Z-scheme van der Waals (vdW) heterostructures of different two-dimensional (2D) monolayers is one effective approach to developing highly efficient photocatalysts. In this study, a β-SnSe/HfS2 heterostructure is designed, and its electronic properties and photocatalytic water splitting performance are systematically investigated through first-principles calculations. The charge density difference and work function indicate the presence of an electric field within the heterostructure, further demonstrating its characteristic direct Z-scheme heterostructure. The heterostructure exhibits excellent photocatalytic activity with higher light absorption coefficients of up to 6.67 × 105 cm−1 in the visible and ultraviolet regions compared to the two monolayers alone. The heterostructure possesses high electron mobility in the x direction (2405.86 cm2s−1V−1) and high hole mobility in the y direction (537.56 cm2s−1V−1), facilitating the separation of electron-hole pairs. According to Gibbs free energy, the heterostructure can split water spontaneously overall in acidic settings and only needs an extra potential of 0.64 eV to do so in neutral situations. It is anticipated that the heterostructure have a solar-to-hydrogen (STH) efficiency of up to 14.29%. Because of this, the β-SnSe/HfS2 heterostructure possesses a significant amount of promise for use as a photocatalyst in the generation of hydrogen through the process of water splitting.