Unravelling the phase transition of 2H-MoS2 to 1T-MoS2 induced by the chemical interaction of Pd with molybdenum disulfide-graphene hybrids

Hybrids of transition metal dichalcogenides (TMDs) nanoparticles on carbon-based materials have attracted considerable attention because of their remarkable physical and catalytic properties and potential applications in future electronic devices because of their high electrical conductivity and increased active sites. The most studied among them are the MoS2 - graphene hybrids. Nowadays, interest arises from introducing a variety of atoms into the layered MoS2 with sulfur excess. In this study, Pd was step wisely deposited on MoS2 and MoS2-rGO (reduced graphene oxide) substrates as well as on MoSx and MoSx-rGO (x >= 2) with different MoSx and rGO ratios for both hybrids. To unravel the chemical interaction and the morphology of Pd on molybdenum disulphide and molybdenum disulphide -graphene composites, characterization with synchrotron radiation and X-ray photoelectron spectroscopies has been employed. These techniques enable non-destructive analysis of the depth profile. This work evaluates the interaction of Pd with S atoms with unsaturated electronic structures, the formation of PdSx surface compounds and Pd substitutional doping, leading to phase transition from the semiconducting 2HMoS2 to metallic 1T-MoS2 state. The understanding of the interaction of Pd with MoSx-graphene hybrids is essential to develop TMD-graphene-based functional materials and related devices.