Influence of Humidity on the Dielectric Properties of Two-Dimensional Microsized Molybdenum Disulfide Powders

Abstract

Changes in the dielectric properties of two-dimensional (2D) microsized molybdenum disulfide powders in response to ambient air humidity at room temperature were studied (impedance spectroscopy, 1 Hz–20 MHz). The microsized 2H-MoS₂ powders were found to absorb significant amounts of moisture (0.43–2.88 wt.%, 3.5 h, relative air humidity of 45–100%). According to impedance spectroscopy data, reversible water intercalation/deintercalation processes led to significant changes in the dielectric properties (total, active, and reactive (capacitive) resistance, capacitance, loss tangent, and real component of relative permittivity) of 2H-MoS₂ powders until equilibrium was reached. In equilibrium, the dielectric properties depended on humidity and frequencies. The dielectric properties of microsized 2H-MoS₂ powders are dynamic functional characteristics that can be effectively controlled over wide ranges by varying the humidity and frequency levels. It is assumed that changes in the dielectric properties of microsized 2H-MoS₂ powders are due to the formation of 2D nanosized MoO_3–x/MoO₃/H⁺_x(H₂O)_yMoS₂ heterostructures on the surface of the intercalated H⁺_x(H₂O)_yMoS₂ phase particles. These findings can be used to improve nanotechnologies that use aqueous environments, optimize the semiconductor, tribological, and catalytic properties of 2H-MoS₂, and develop multifunctional 2D nanomaterials (humidity sensors, sorbents, and photocatalysts for water purification and electro(photo)catalysts for hydrogen production by water electrolysis).