The unexpected effect of vacancies and wrinkling on the electronic properties of MoS₂ layers

We report a combined experimental/theoretical approach to study the connection of S-vacancies and wrinkling on MoS₂ layers, and how this feature produces significant changes in the electronic structure and reactivity of this 2D material. The MoS₂ material, when used as a catalyst in operative conditions, was found to be mainly composed of thin and short 1-5 layer sheets instead of a poorly crystalline structure, as it was previously assumed. Notably wrinkled structures with S-vacancies were also found through transmission electron microscopy. Atomistic simulations revealed a natural connection between sulfur-vacancies, wrinkling and folding. Density functional calculations further revealed that such curved structures present a lower electronic band-gap and a higher reactivity towards thiophene compared to the planar MoS₂ counterpart.