Pristine and Janus monolayers of vanadium dichalcogenides: potential materials for overall water splitting and solar energy conversion

Emerging two-dimensional (2D) transition metal dichalcogenides with admirable optoelectronic and electrochemical properties can be used in many practical applications like photocatalysis. In this study, through first-principles calculations, a zealous effort has been devoted to investigating the electronic, photocatalytic, and optical properties of pristine and Janus monolayers of vanadium dichalcogenides. Binding energies and elastic constants indicate the structural and mechanical stability of these layers. Pristine and Janus monolayers show band gaps in a range of 0.4 to 1.6 eV. Band gap alignments by using empirical and DFT approach indicate that VS₂, VSe_2, and VSeS have large enough kinetic overpotentials for photocatalytic overall water splitting. Additionally, biaxial strain displays that the band gap decreases with the variation of strain from -3% to + 3%. In the case of an electric field (E_ext), band gap decreases linearly when varied from -0.8 VÅ⁻¹ to + 0.8 VÅ⁻¹. All pristine and Janus monolayers exhibit a high absorption coefficient ~ 10⁵ cm⁻¹. The results of this study suggest that pristine and Janus monolayers of vanadium dichalcogenides are potential candidates for photocatalytic water splitting and optoelectronic device applications.