Design of XS 2 (X = W or Mo)-Decorated VS 2 Hybrid Nano-Architectures with Abundant Active Edge Sites for High-Rate Asymmetric Supercapacitors and Hydrogen Evolution Reactions.

Two-dimensional layered transition metal dichalcogenides have emerged as promising materials for supercapacitors and hydrogen evolution reaction (HER) applications. Herein, the molybdenum sulfide (MoS 2 )@vanadium sulfide (VS 2 ) and tungsten sulfide (WS 2 )@VS 2  hybrid nano-architectures prepared via a facile one-step hydrothermal approach is reported. Hierarchical hybrids lead to rich exposed active edge sites, tuned porous nanopetals-decorated morphologies, and high intrinsic activity owing to the strong interfacial interaction between the two materials. Fabricated supercapacitors using MoS 2 @VS 2  and WS 2 @VS 2  electrodes exhibit high specific capacitances of 513 and 615 F g - 1 , respectively, at an applied current of 2.5 A g - 1  by the three-electrode configuration. The asymmetric device fabricated using WS 2 @VS 2  electrode exhibits a high specific capacitance of 222 F g - 1  at an applied current of 2.5 A g - 1  with the specific energy of 52 Wh kg - 1  at a specific power of 1 kW kg - 1 . For HER, the WS 2 @VS 2  catalyst shows noble characteristics with an overpotential of 56 mV to yield 10 mA cm - 2 , a Tafel slope of 39 mV dec -1 , and an exchange current density of 1.73 mA cm - 2 . In addition, density functional theory calculations are used to evaluate the durable heterostructure formation and adsorption of hydrogen atom on the various accessible sites of MoS 2 @VS 2  and WS 2 @VS 2  heterostructures.