Electronic properties and applications of MoSSe/MoSTe heterostructure in photocatalytic water splitting

Monolayer material's electronic properties can be controlled by constructing heterostructures, such as transition metal dichalcogenides (TMDCs) heterostructures. Among them, heterostructures with a new direct Z-scheme electronic band structure are promising solar-driven water splitting photocatalysts. In this work, the first principle calculation based on Density functional theory (DFT) was used to study the structure, electrical properties and optical properties of MoSSe/MoSTe heterostructures. By vertically stacking MoSSe and MoSTe monolayers and via lattice relaxation, 12 different MoSTe/MoSSe heterostructure models have been constructed. Model 1 (TeMoS/SeMoS) and model 2 (SMoTe/SMoSe) are novel direct Z-scheme heterostructure and traditional type II band configurations, respectively. Compared to type II heterostructures, direct Z-scheme arrangement can achieve more efficient spatial separation of photogenerated carriers, increase the lifetime of minority carriers while retaining the redox ability of internal carriers. And compared to monolayer materials, MoSTe/MoSSe heterostructures exhibit stronger and broader optical absorption. Additionally, the conduction band edge potential of MoSTe in the heterostructure is negative to the H+/H2O electrode potential, and the valence band edge potential of MoSSe is positive to the O2/H2O electrode potential. It can be inferred that MoSTe/MoSSe heterostructure has strong reduction and oxidation capabilities, and can achieve total water-splitting reaction. Further Gibbs free energy calculation found that the MoSSe/MoSTe heterostructure can spontaneously conduct thermodynamic water splitting under the light in both acidic and neutral environments, and the theoretical hydrogen production efficiency is 16.7 %.