Strain engineering the electronic and photocatalytic properties of WS2/blue phosphene van der Waals heterostructures

Abstract

The effects of −8–8% in-plane uniaxial and biaxial strains on the electronic and photocatalytic activity of tungsten disulfide/blue phosphene (WS₂/BlueP) are investigated within the framework of first-principles calculations. The most energetically stable configuration of WS₂/BlueP exhibits type I band alignment with a direct band gap of 1.779 eV. Compared with WS₂ and BlueP, WS₂/BlueP has the strongest absorption in the entire visible light region with a red-shifted absorption edge. The in-plane −8–8% uniaxial and biaxial strains cause elastic deformation of the heterostructures. The strains can affect the band gap, band edge arrangement, band type (type-I, type-II, Z-scheme) and electron transition type (direct, indirect) of WS₂/BlueP. The −2% uniaxial (or biaxial) strain can engineer the band gap to reach the maximum and achieve full water decomposition. At pH = 0, only the −2% and −4% uniaxial and −2% biaxial strained WS₂/BlueP (Z-scheme) heterostructures are thermodynamically feasible, while at pH = 7, all the strained heterostructures are viable for photocatalytic water decomposition. The −2% uniaxial and biaxial strained WS₂/BlueP heterostructures at pH = 0 and pH = 7 are proved to be potential candidates for achieving full water decomposition. The lower potential determining step, higher electro-chemical driving forces and lower effective mass of carriers can promote the transition performance and improve the photocatalytic efficiency. Therefore, the in-plane uniaxial and biaxial strains can effectively adjust the electronic and photocatalytic performances of the heterostructures.