Structural Characterization and Thermal Stability of MoS₂Intercalation Compounds

Abstract

The intercalation of MoS 2 with Co and Fe complexes has been accomplished via exfoliation of Li x MoS 2 by reaction with water, followed by flocculation in the presence of cationic guest species. The resulting self-assembled compounds have been characterized by X-ray absorption spectroscopy, electron diffraction, powder X-ray diffraction, and magnetic measurements. The 2H-type (undistorted) MoS 2 undergoes a structural distortion to 1T-type MoS 2 during the Li intercalation, which is partially maintained upon exfoliation and flocculation. A structural model of 1T-MoS 2 is proposed on the basis of X-ray absorption spectroscopy and electron diffraction, in which the unit cell has P 3 symmetry with lattice parameters a = 6.52(5) Å, c = 6.14 Å. The Mo atoms are shifted approximately 0.5 Å from their positions in 2H-MoS 2 to form trigonal clusters in 1T-MoS 2, with a concomitant change in coordination geometry from trigonal prismatic to distorted octahedral. Layers of Co(OH) 2 were intercalated between the distorted and/or undistorted layers of MoS 2 when either Co 2+ or Co 3+ complexes were used as the flocculating ion. Flocculation of exfoliated MoS 2 with (η 5 -C 5 H 5 ) 2 M + (M = Fe, Co) resulted in intercalation of monolayers of the metallocenium cations between the partially negatively charged MoS 2 sheets.