In-plane defect engineering on MoS2 through a novel two-phase hydrothermal synthesis.

In this work, we proposed a two-phase hydrothermal synthesis approach to fabricate high-curvature bulk surface with engineered in-plane defects. Organic or supercritical solvents were introduced as a second immiscible media to alter MoS 2 hydrothermal growth. Two mixing scenarios, depending on the ratio of organic solvent to aqueous solution. In the case of the organic solvent isolated by aqueous solution, the growing slabs change its original direction when getting contact with the organic droplets. In the scenario that aqueous droplets dispersed in organic solvent, MoS 2 slabs grow along the curved interfaces of aqueous droplets. Experimental results showed that the curved basal planes were generated in the two cases and more curvatures were introduced in the second phase under adequate mixing energy. Higher curvature degree led to a better catalytic performance. Compared to decalin, supercritical heptane that can facilitate the dispersion of the precursor-containing aqueous solution into homogeneous nano-size reaction cells, showed a great capacity to generate highly curved slabs. MoS 2 synthesized with supercritical solvent exhibits the highest activity among the investigated catalysts. The catalysts were characterized by SEM, XRD, XAFS, TPR and nitrogen adsorption analysis. The results were proved by the theoretical calculations that the formation energy (E form) of sulfur vacancy (V S) on curly structure possesses a reduction of 0.19 eV comparing with planar MoS 2 monolayer. The curved structure can facilitate the surface V S generation by depopulating the occupied bonding states of corresponding Mo-S bonds. This work provides an effective approach to create basal defects on the MoS 2 to promote its catalyst activity. [Display omitted] • In-plane defects were fabricated by a novel two-phase hydrothermal synthesis. • More defects (curvatures) are created when organic solvent is in majority. • Compared to organic solvent, supercritical solvent generates more curly structure. • The formation energy of sulfur vacancy on curly structure is lower than planar MoS 2. • MoS 2 synthesized with supercritical solvent exhibits the highest activity. [ABSTRACT FROM AUTHOR]