Effect of Bi intercalation on phase stability and defect passivation in 3R-MoS2

Abstract

A hydrothermal approach was employed to achieve bismuth intercalation into rhombohedral 3R-MoS₂, offering a viable strategy for engineering the structural, electronic, and surface characteristics of the MoS₂ polytype. X-ray diffraction confirms retention of the 3R phase with a systematic leftward shift in 2θ and c-axis expansion (18.42 to 18.89 Å), along with a 50% reduction in microstrain, indicating lattice relaxation induced by Bi³⁺ intercalation. FE-SEM reveals a transformation to a hierarchical microsphere morphology with filamentous projections, while HR-TEM confirms an expanded interlayer spacing (0.68–0.72 nm). EDS and XPS demonstrate uniform Bi³⁺ distribution, sulphur-vacancy passivation, and partial oxidation states. TGA-DTG displays a modified two-stage decomposition, reflecting enhanced thermal resilience. Most notably, BET analysis reveals a 6.6-fold increase in surface area (1.60–10.58 m²/g), a ~3.7- to 4.7-fold increase in pore volume, and pore diameter refinement (47.37 nm to 19.19 nm) within the mesopore regime. Room-temperature I-V measurements reveal a transition from non-ohmic to nearly ohmic behaviour, attributed to expanded interlayer spacing and improved surface accessibility. This work systematically analyses the effect of Bi³⁺ intercalation in 3R-MoS₂, providing new insights into defect passivation and phase stability. Altogether, these results establish Bi-MoS₂ as a promising multifunctional material with promising avenues for energy storage, catalysis, and adsorption applications.