Efficient photocatalyst for overall water-splitting hydrogen generation using a direct Z-scheme MoTe2/SnS2 van der Waals heterostructure

Abstract

In order to solve the problems of environmental pollution and energy crisis, searching an efficient photocatalyst is very important to transfer the solar energy to hydrogen energy. The MoTe₂/SnS₂ heterojunction is constructed in this paper and the structural, electronic, optical and photocatalytic properties are investigated by first-principles calculation. The small lattice mismatch of 3.31 % makes it experimental fabricable. The thermodynamics and thermal stabilities are verified from the binding energy and AIMD simulation. A 0.149 |e| Bader charge is transferred from MoTe₂ side to SnS₂ side and thus a built-in electric field is formed with direction from MoTe₂ side to SnS₂ side as well as an electrostatic potential drop of 6.48 eV of the MoTe₂ layer than the SnS₂ layer. Three actions of the built-in electric field, the band bending and smaller band gap of 0.66 eV than 1.66 eV and 2.36 eV for MoTe₂ and SnS₂ layers respectively make the photogenerated carriers transfer through a direct Z-scheme mechanism. The photogenerated electrons are accumulated on the MoTe₂ CB and the photogenerated holes on the SnS₂ VB both with strong overpotentials to participate HER and OER and to generate H₂ and O₂ respectively. The broader and stronger optical absorption, higher STH efficiency of 29.13 %, and the stronger catalytic activity under acidic, neutral and weak alkaline $\left(\text{pH}<9\right)$ conditions confirm the potential application of the MoTe₂/SnS₂ heterostructure in photocatalytic overall water-splitting.