XAFS studies of soft-heavy-metal-ion-intercalated MxMoS2 (M = Hg2+, Ag+) solids

XAFS studies were performed on two new soft-heavy-metal-ion-intercalated materials MxMoS2 (M = Hg2+, Ag+). For the compound Hg0.32MoS2, EXAFS results show an average Hg coordination environment consisting of approximate to2 S atoms at 2.38 Angstrom and approximate to0.2 (+/- 35%) Kg atoms at 2.55 Angstrom. Along with Hg XANES analysis, these data indicate that the Hg atoms in this compound are present as a mixture of mercuric and mercurous ions. Ag EXAFS analysis of the compound Ag0.61MoS2 indicates a Ag coordination environment consisting of approximate to2 S atoms at 2.43 Angstrom. Ag EXAFS and XANES results for heat-treated Ag0.61MoS2 indicate that the Ag coordination environment has changed to that nearly identical for silver metal with several Ag-Ag interactions detected. The results suggest that heat treatment of Ag0.61MoS2 facilitates the chemical reduction of the intercalated silver ions to elemental silver. In addition, Mo EXAFS and XANES analyses indicate that both the Hg- and Ag-intercalated compounds have significant amounts of the 1T-phase of MoS2 in them. Prolonged exposure of both of these materials to an aerobic atmosphere does not affect their Mo EXAFS. Comparison of these results with those for exfoliated and restacked MoS2 suggests that different intercalated guest ions afford different oxidative stabilities to the host MoS2 layers. This hypothesis is used to rationalize some inconsistencies in previous reports of MxMoS2 XAFS studies.