Towards a Comprehensive Understanding of the Reaction Mechanisms Between Defective MoS2 and Thiol Molecules.

Sulfur vacancies (SVs) inherent in MoS2 are generally detrimental for carrier mobility and optical properties. Thiol chemistry has been explored for SV repair and surface functionalization. However, the resultant products and reaction mechanisms are still controversial. Herein, a comprehensive understanding on the reactions is provided by tracking potential energy surfaces and kinetic studies. The reactions are dominated by two competitive mechanisms that lead to either functionalization products or repair SVs, and the polarization effect from decorating thiol molecules and thermal effect are two determining factors. Electron-donating groups are conducive to the repairing reaction whereas electron-withdrawing groups facilitate the functionalization process. Moreover, the predominant reaction mechanism can be switched by increasing the temperature. This study fosters a way of precisely tailoring the electronic and optical properties of MoS2 by means of thiol chemistry approaches.