# Phase‐Pure 1T’ Molybdenum Disulfide Synthesis and Stabilization

## TL;DR

A new method stabilizes the 1T’ phase of molybdenum disulfide, preventing degradation and enabling long-term use in applications.

## Contribution

A self-intercalation method is introduced to synthesize and stabilize phase-pure 1T’ MoS2 with long-term stability.

## Key findings

- The self-intercalation method produces phase-pure 1T’ MoS2 with 100% purity even after 750 °C annealing or 1-year aging.
- K2S intercalation lowers the formation energy, making the metastable 1T’ phase stable.
- The method is versatile for various 1T’ TMDs using alkali metal chalcogenides intercalation.

## Abstract

Metastable‐phase transition metal dichalcogenides (TMDs) show distinct structures and properties compared with the well‐studied thermodynamically stable phase. The phase impurity and degeneration are two critical challenges for the research and applications of metastable 1T’‐phase MoS2. Here, a self‐intercalation method is demonstrated to synthesize and stabilize the phase‐pure 1T’ MoS2. The K2S intercalation and 1T’ MoS2 synthesis are simultaneously done in only one step, leading to uniform intercalation and 1T’ phase purity. This engineered intercalation structure achieves stabilization of 1T’ MoS2 without changing its in‐plane structure. It keeps 1T’ phase structure and 100% phase purity even after 750 °C annealing or 1‐year aging exposed to air, while 1T’ MoS2 transforms to 2H phase gradually, or instantly over 97 °C. The theory calculation results show that the K2S intercalation lowers the formation energy and makes metastable 1T’ phase become stable. As a result, this stabilization method prevents gradual degeneration of applications performance that is inevitable in the past. This mass‐production‐available method has been successfully proved versatile for various 1T’ TMDs with numerous alkali metal chalcogenides intercalation. It eliminates a significant disadvantage of 1T’ TMDs, which can facilitate the investigation of novel properties and the development of fresh applications.

The synthesis and stabilization of phase‐pure 1T’ MoS2 or other transition metal dichalcogenides (TMDs) are achieved by a self‐intercalation method. During this mass‐production‐available process, intercalation and formation of 1T’ TMDs are conducted simultaneously, leading to uniform defect‐free intercalation without changing in‐plane structure, and phase purity. The intercalation lowers the formation energy and makes metastable 1T’ TMDs become stable.© 2025 WILEY‐VCH GmbH