Universality of electronic characteristics and photocatalyst applications in the two-dimensional Janus transition metal dichalcogenides

Due to mirror symmetry breaking, two-dimensional Janus transition metal dichalcogenides M X Y (M =Mo,W ; X ,Y =S,Se,Te ) present charming electronic properties. However, there have not been many related studies as of yet, and the intrinsic physical pictures are unclear. Here, we use first-principles calculations to explore the universality of electronic characteristics and photocatalyst applications of Janus M X Y , finding that the induced dipole moment, vibrational frequency, Rashba parameters, and direct-indirect band transition of monolayer M X Y are deeply associated with the atomic radius and electronegativity differences of chalcogen X and Y elements. The internal electric field renders Janus M X Y the ideal photocatalysts. Moreover, the stacking-dependent on/off switch of the dipole moment further confirms that asymmetric Janus M X Y serves as a promising candidate for highly efficient photocatalysts within a broad range from infrared, visible, to ultraviolet light.