Insights into the Structural Evolution of MoS2 from the Semiconductive 2H to Metallic 1T Phase

Molybdenum disulfide (MoS2) possesses distinct electrochemical and electronic properties, as a unique material, and raises a growing amount of interest in both its synthesis and application. Compared with the most stable and widely existing triangle prismatic (2H) phase of MoS2, 1T-MoS2, a metallic octahedral but metastable crystal phase, occupies a more important position within the application in electrochemical reactions, photoelectron catalysis, photodetectors, photothermal agents, energy storage devices, and biosensors. In this article, an exploration of the key reasons for the different stabilities of 1T- and 2H-MoS2 is conducted via density functional theory (DFT) calculations. Meanwhile, simple but facile bonding patterns of valence orbits in 1T- and 2H-MoS2 are proposed with an emphasis on their properties and stability. Consequently, the electron count and density of state (DOS) unification of MoS2 are considered as the secrets for the 2H-to-1T phase transition, where the most reported manners for obtaining 1T-MoS2 can be well explained. The finding here has a profound hint for the phase engineering of MoS2 and promotes the development of crystal material nowadays.