Rational design of MoS2/MoSe2 lateral heterostructure with optimal component ratio used for high-efficient photocatalytic overall water splitting

Abstract

The design of high-efficient photocatalysts is desirable for overall water splitting. In this work, the first-principles calculations are implemented to investigate the component ratio effects on the photocatalytic water splitting of MoS₂/MoSe₂ lateral heterostructure. MoS₂/MoSe₂ lateral heterostructure shows a decreased band-gap from 1.84 to 1.61 eV as component ratio n increases, and its band-edge alignments straddle the redox potential of H₂O, only with the precondition of n < 0.5. According to the work function difference between the isolated monolayers, a significant charge separation appears across the stitching area, with the maximal charge transfer being 0.187 e/unit from MoSe₂ to MoS₂ side, and thereby induces a built-in electric field of 0.25∼0.29 eV/unit, promoting the separation of HER and OER. MoS₂/MoSe₂ lateral heterostructure possesses considerable hole (electron) mobility of about 150 (50) cm²V^-1s^-1, facilitating the charge-transfer and aggregation in the surface reactions. The absorption shows an obvious red-shift, sufficiently improving photon utilization. Additionally, MoS₂/MoSe₂ lateral heterostructure with n < 0.50 exhibits the reduced energy barriers in both the HER and OER. The strain and pH effects show that MoS₂/MoSe₂ lateral heterostructure with n < 0.5 behaves enhanced photocatalytic performance under tensile strain, and the heterostructure with n > 0.5 can also possesses suitable band-edge alignments by increasing pH value. These results provide theoretical support for developing efficient photocatalyst by adjusting component ratio in MoS₂/MoSe₂ lateral heterostructure.