Symmetry-broken MoS2 nanotubes through sequential sulfurization of MoO2 nanowires.

Transition metal dichalcogenide (TMD) nanotubes are emerging quantum materials with distinctive symmetry-breaking properties, offering significant potential for energy conversion technologies. However, the direct synthesis of crystalline MoS2 nanotubes remains challenging due to limited understanding of their high-temperature growth mechanisms. Here, we present a robust and controllable strategy for the direct growth of crystalline MoS2 nanotubes with well-defined tubular morphology and high structural uniformity. This approach features two key innovations: first, the controlled introduction of hydrogen reduces MoO3 into one-dimensional (1D) tetragonal MoO2 (space group I4/m) chains via a vapor-liquid-solid (VLS) mechanism; second, precise temperature zoning ensures timely sulfur vapor infusion for complete sulfurization. The intermediate MoO2 phase, with its singular crystallographic orientation, acts as an ideal template for nanotube formation. Tellurium (Te) serves as a fluxing mediator to promote the formation of uniform MoO2 nanowires, which are subsequently converted into MoS2 nanotubes. By systematically tuning the hydrogen concentration, we reveal its critical role in directing product morphology. The resulting MoS2 nanotubes exhibit pronounced symmetry breaking and significant bulk photovoltaic performance, achieving a photoresponsivity of 510 A cm-2 under 1.88 × 104 W cm-2 illumination. This work advances both the fundamental understanding of nanotube growth and the development of symmetry-engineered optoelectronic materials.