Comparative study of the electronic and photocatalytic properties of bulk and monolayer MX2: A TB-mBJ study

Abstract

The electronic band structure and photocatalytic activity of six transition metal dichalcogenides (TMDCs) MX2 [M = Mo and W; X = S, Se and Te] are illustrated by Tran Blaha modified Becke Johnson (TB-mBJ) potential. Interestingly, a lower recombination rate has been observed for bulk MX2 in comparison to the monolayer. However, the calculated band edge positions indicate that only MoS2 and WS2 monolayers have appropriate band alignment with water redox potentials. The redox potentials are tuned by varying the pH value of the medium to verify the suitability of TMDCs as a photocatalyst. At pH = 7, MoSe2 monolayer and bulk WS2 exhibited proper band alignment for water splitting while WSe2 monolayer required a basic solution (pH = 11). Our result suggests that bulk WS2 could be a potential photocatalyst owing to its proper band alignment, lower carrier recombination rate and high absorption coefficient (105 cm−1) in the visible region.