Anion Extraction-Induced Polymorph Control of Transition Metal Dichalcogenides

Controlled phase conversion in polymorphic transition metal dichalcogenides (TMDs) provides a new synthetic route for realizing tunable nanomaterials. Most conversion methods from the stable 2H to metastable 1T phase are limited to kinetically slow cation insertion into atomically thin layered TMDs for charge transfer from intercalated ions. Here, we report that anion extraction by the selective reaction between carbon monoxide (CO) and chalcogen atoms enables predictive and scalable TMD polymorph control. Sulfur vacancy, induced by anion extraction, is a key factor in molybdenum disulfide (MoS 2 ) polymorph conversion without cation insertion. Thermodynamic MoS 2 –CO–CO 2 ternary phase diagram offers a processing window for efficient sulfur vacancy formation with precisely controlled MoS 2 structures from single layer to multilayer. To utilize our efficient phase conversion, we synthesi…