Exfoliated and restacked MoS2 and WS2: Ionic or neutral species? Encapsulation and ordering of hard electropositive cations

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Abstract

The relationship between charge and structure in restacked MS2 (M = Mo, W) has been probed by cation encapsulation and chemical oxidation and characterized by elemental analysis, electron diffraction, X-ray diffraction, and Differential Scanning Calorimetry. Alkali cations have been encapsulated in MoS2 and WS2 without the presence of a co-intercalated counterion, suggesting a negative charge in the 0.15-0.25 electrons per M atom range. Electron diffraction studies show ordering of these cations between the layers. Chemical oxidation with I2 or Br2 results in a change in the structure of restacked MoS2, giving rise to a √3a x √3a superlattice, whereas no change is observed in the structure of restacked WS2. Differential Scanning Calorimetry studies show that the irreversible exothermic transition to 2H-MS2 shifts to lower temperature with oxidation. The observed structural distortion and residual negative charge uniquely explain the thermopower measurements, which indicate that restacked MoS2 and WS2 are p-type metallic conductors.

Original languageEnglish
Pages (from-to)11720-11732
Number of pages13
JournalJournal of the American Chemical Society
Volume121
Issue number50
DOIs
Publication statusPublished - Dec 22 1999

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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