XAFS Study of MoS₂ Intercalation Compounds

Abstract
MoS₂ intercalated with Mn, Co, Ni, and Ru species, prepared from single layer MoS₂ dispersions in water, were studied by x-ray absorption spectroscopy. M. K-edge EXAFS results (M = Mn, Co, Ni) are consistent with an alternating MoS₂-M(OH)₂ layered structure. For the Mn and Co intercalates the MoS₂ layers were found to be very similar to that of the parent crystalline MoS₂ with trigonal prismatic coordination of the Mo atoms. For the Ni and Ru intercalates, Mo K edge EXAFS revealed structural rearrangement of MoS₂ layers similar to that observed for MoS₂ single layers, with octahedral coordination of Mo. S K edge XANES spectra reveal that the rearrangement is coupled with a change in the electronic structure of the S atoms in the matrix. 'Ihese changes can be associated with charge transfer between 'host' and 'guest' layers. In addition, SO₄^2- and Mo⁶⁺ were detected in some of the intercalated materials, presumably due to exposure to air, suggesting that transition metal intercalation may increase the susceptibility of the MoS₂ layers to oxidation.