Fast One‐Step Microwave Synthesis of 2H–1T MoS ₂ for Efficient Hydrogen Evolution

The mechanisms of MoS 2 formation and the effect of processing parameters in microwave‐assisted (MW) synthesis are still unclear, limiting reproducibility and optimization. Here, MoS 2 nanoflakes were grown in a MW hydrothermal reactor, and synthesis conditions were optimized for rapid hydrogen evolution reaction (HER) catalyst production. In operando camera monitoring tracked synthesis progression, while UV–vis and XPS analyses revealed precursor consumption and the presence of superficial MoO x S y species. XRD showed crystal phase evolution over synthesis time. The optimized method produces carbon‐supported MoS 2 with mixed 2H–1T seeds, on which pure 1T MoS 2 nanoflakes form, achieving −0.22 and −0.34 V at −10 mA cm −2 in acidic and alkaline electrolytes. The synthesis requires no postsynthesis treatment and is completed in only 15 min. However, maintaining at least a stoichiometric S:Mo precursor ratio of 14.2:1 was demonstrated to be essential to ensure complete sulfurization of Mo and, consequently, full optimization of the material using MW‐assisted synthesis.