Scalable Bottom-Up Synthesis of High-Purity 1T-MoS₂ Assisted by Na₂SO₄ Template

MoS₂ is a promising layered material for energy storage fields owing to its phase-dependent physicochemical properties. However, the scalable synthesis of 1T-MoS₂ 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 Na₂SO₄ as the phase transition inducer, growth template and S source for the bottom-up synthesis of 1T-MoS₂. Theoretical calculations showed that the distortion of Mo─Mo and Mo─S bonds and the change of the formation energy of 2H- and 1T-MoS₂ caused by the adsorption of electron donating Na were the fundamental reasons for the formation and stability of octahedral 1T-MoS₂. In situ analysis confirmed that Na₂SO₄ guided the epitaxial growth of MoS₂ by slowly releasing H₂S, and the formation of intermediates NaMoO_x and NaMoS_x 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-MoS₂ is 37.4 mV and 32.2 mV/dec, respectively. This preparation strategy enables large-scale production of metastable MoS₂ while maintaining exceptional crystallinity and phase purity, providing new opportunities for phase engineering of transition metal dichalcogenide.