They are therefore widely used to modify the surfaces of materials for sensors, electrodes, catalysts and others . They were first used to functionalize glassy carbon by Pinson et al. in 1992, which then opened up the prospect of surface modification of other materials using aryl diazonium salts . Recent reports have shown the importance in functionalizing MoS2 in enhancing their properties for hydrogen evolution reaction (HER), electronic and sensing applications . However, 2H-MoS2 is typically inert to chemical functionalization because its Mo atoms are saturated with chalcogen atoms and thus 2H-MoS2 is difficult to functionalize directly . As a consequence, the recent reports on the functionalization of 2H-MoS2 include pretreatment of the flakes prior to functionalization. For example, Benson et al. reported functionalization of MoS2 for applications in HER by firstly changing the phase of MoS2 from 2H to 1T through chemical exfoliation using n-butyllithium, followed by a functionalisation with aryl diazonium salts . Although functionalization in this way is successful, it results in losses of desired properties of 2H-MoS2 such as the semiconducting electronic structure . synthesized diazonium functionalized MoS2 by bombarding the MoS2 with Ar plasma in order to create S-vacancies, which enhanced the functionalization . Nevertheless, this may lead to unwanted defects on the basal planes which could be detrimental to desired properties.