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MoS2 based materials are considered the most reliable alternative catalysts for the hydrogen evolution reaction (HER), where engineering of active sites has emerged as an acceptable approach to tune their HER activity. In this approach, the dispersion of bulk MoS2 in the aqueous phase was increased with a surfactant (sodium dodecyl sulfate), which reduced the exfoliation time and enhanced the exfoliation ability to produce layered MoS2 nanosheets. During the hydrothermal treatment, the nanosheets were further scissored into small nanocrystals. Nanocrystals have attractive properties with stable dispersion and high-water solubility. Our method provides a scalable, eco-friendly, easy, and low-cost strategy for designing other HER catalysts. Such ultra-small MoS2 nanocrystals with rich Mo vacancies were used as catalysts for HER, which showed excellent electrocatalytic activity with a low overpotential (95 mV) and small Tafel slope (41 mV/dec) in 0.5M H2SO4 electrolyte. The design and synthesis of the HER catalyst in this work presents a promising path for preparing active and stable electrocatalysts to replace costly metal-based catalysts for hydrogen production. [ABSTRACT FROM AUTHOR]

To improve the production rate of MoS 2 nanosheets as an excellent supercapacitor (SC) material and enhance the performance of the MoS 2 -based solid-state SC, a liquid phase exfoliation method is used to prepare MoS 2 nanosheets on a large scale. Then, the MnO 2 nanowire sample is synthesized by a one-step hydrothermal method to make a composite with the as-synthesized MoS 2 nanosheets to achieve a better performance of the solid-state SC. The interaction between the MoS 2 nanosheets and MnO 2 nanowires produces a synergistic effect, resulting in a decent energy storage performance. For practical applications, all-solid-state SC devices are fabricated with different molar ratios of MoS 2 nanosheets and MnO 2 nanowires. From the experimental results, it can be seen that the synthesized nanocomposite with a 1:4 M ratio of MoS 2 nanosheets and MnO 2 nanowires exhibits a high Brunauer-Emmett-Teller surface area (∼118 m 2 /g), optimum pore size distribution, a specific capacitance value of 212 F/g at 0.8 A/g, an energy density of 29.5 W h/kg, and a power density of 1316 W/kg. Besides, cyclic charging-discharging and retention tests manifest significant cycling stability with 84.1% capacitive retention after completing 5000 rapid charge-discharge cycles. It is believed that this unique, symmetric, lightweight, solid-state SC device may help accomplish a scalable approach toward powering forthcoming portable energy storage applications., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)