Department of Energy Engineering (Energy Engineering)Two Dimensional (2D) materials such as transition metal chalcogenides (TMDs) has been studied, but several problems still remain as disturbance for application to energy materials like electrocatalyst. In this work, we present a phase engineering of TMDs for electrocatalyst via highly reactive molten Potassium (K) metal intercalation. The 2H to 1T phase transition of TMDs has been exploited for application of the 1T phase with metallic property to applications such as electrocatalysts. However, the improving stability of thermodynamically metastable 1T TMDs remains an important challenge to overcome for using 1T phase properties. In addition, scalable synthesis methods of 1T TMDs, which are necessary for a wide range of applications, have to be developed. In this work, we presented a synthesis method of 1T phase MoS2 using molten K metal intercalation suitable for scalable method and confirmed the sucessfully phase transition 2H to 1T phase and improvement of 1T phase stability by K atom doping in the MoS2 basal plane. Furthermore, K atoms are doped in MoS2 basal plane, which can donate electron continuously to MoS2, which achieved long-term stability, thermal stability, and high power laser stability. Furthermore, we applied K doped 1T MoS2 to the hydrogen evolution reaction (HER) electrocatalyst and confirmed the improved HER performance owing to high electrical conductivity and basal plane activation of K-doped 1T MoS2 compared to 2H MoS2 and 1T MoS2 (n-BuLi), and high phase stability of K-doped 1T MoS2 exhibits high HER stability.clos
