Scalable Bottom-Up Synthesis of High-Purity 1T-MoS Assisted by NaSO Template.

MoS is a promising layered material for energy storage fields owing to its phase-dependent physicochemical properties. However, the scalable synthesis of 1T-MoS is challenging due to the inherently high generation energy. Inspired by alkali-metal-induced phase transitions of 2H-MoS₂, we developed a sodium-mediated synthesis strategy using NaSO as the phase transition inducer, growth template and S source for the bottom-up synthesis of 1T-MoS. Theoretical calculations showed that the distortion of Mo─Mo and Mo─S bonds and the change of the formation energy of 2H- and 1T-MoS caused by the adsorption of electron donating Na were the fundamental reasons for the formation and stability of octahedral 1T-MoS. In situ analysis confirmed that NaSO guided the epitaxial growth of MoS by slowly releasing HS, and the formation of intermediates NaMoO and NaMoS were the key to the generation of 1T phase. Systematic optimization identified 16-18 vol% hydrogen concentration as the critical parameter for achieving high-phase-purity metallic MoS₂. As a catalyst for hydrogen evolution reaction, the overpotential and Tafel slope of 1T-MoS is 37.4 mV and 32.2 mV/dec, respectively. This preparation strategy enables large-scale production of metastable MoS while maintaining exceptional crystallinity and phase purity, providing new opportunities for phase engineering of transition metal dichalcogenide.