The type-II PtSe2/WS2 van der Waals heterostructure: A high efficiency water-splitting photocatalyst

In this paper, we comprehensively research the structural stability, electronic property, charge transfer and optical absorption of the free-standing PtSe2, WS2 monolayers and the PtSe2/WS2 heterostructure through first-principles calculations based on density functional theory. The optimized interlayer distances of 3.17, 3.19 and 3.20 Å, respectively for the patterns H1, H2 and H3 of the PtSe2/WS2 heterostructure indicate a typical van der Waals (vdW) interaction between constituted PtSe2 and WS2 monolayers. The negative binding energies show the formations of the PtSe2/WS2 vdW heterostructures are energetically favorable, especially the pattern H1 with the lowest value of -7.26 eV. The valence band maximum and conduction band minimum donated by WS2 and PtSe2 monolayers, respectively represent the PtSe2/WS2 heterojunction is a type-II heterojunction. The Bader charge analysis indicates that approximately 0.0338 |e| electrons transfer from WS2 to PtSe2 monolayer, resulting in a built-in electric field from WS2 to PtSe2 monolayer and thus suppresses the recombination of photogenerated carriers. The optical absorption analysis shows the PtSe2/WS2 heterostructure can efficiently capture solar energy and has good photocatalytic activity in the ultra violet and visible light regions.