Synthesis of Stable 1T′-MoS ₂ with Hexagonal Star Morphology for Efficient Hydrogen Evolution

Metallic two-dimensional (2D) molybdenum disulfide in the 1T′ phase (1T′-MoS2) has emerged as a highly promising electrocatalyst for the hydrogen evolution reaction (HER), owing to its catalytically active basal plane and exceptional electronic conductivity. However, metastable 1T′-MoS2 has poor stability, and its synthesis continues to pose significant challenges due to its high intrinsic formation energy and the limited availability of synthetic strategies for precise morphological control. Here, we demonstrate a KCl-assisted thermal deposition method for the controlled synthesis of hexagonal star-shaped MoS2 with tunable phases (1T′, 2H, and 1T′/2H heterostructures). The introduced KCl facilitates phase stability and promotes the formation of defined hexagram morphologies with abundant edge sites. Comprehensive structural and spectroscopic analyses confirm high phase purity and exceptional environmental stability. As a HER electrocatalyst, the 1T′-MoS2 exhibits outstanding performance, achieving a low overpotential of 122 mV at 10 mA cm–2 and a Tafel slope of 45.2 mV dec–1, alongside maintaining operational stability for 35 h. Density functional theory (DFT) calculations reveal a near-optimal hydrogen adsorption free energy on the S-edge (|ΔGH| = 0.018 eV) and the basal plane of 1T′-MoS2 (|ΔGH| = 0.060 eV). This high intrinsic activity, combined with the maximized exposure of edge sites enabled by the hexagonal star-shaped architecture, accounts for the superior HER activity. This work offers a scalable route for designing high-performance MoS2-based electrocatalysts.