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The ability to efficiently evolve hydrogen via electrocatalysis at low overpotentials holds tremendous promise for clean energy. Hydrogen evolution reaction (HER) can be easily achieved from water if a voltage above the thermodynamic potential of the HER is applied. Large overpotentials are energetically inefficient but can be lowered with expensive platinum based catalysts. Replacement of Pt with inexpensive, earth abundant electrocatalysts would be significantly beneficial for clean and efficient hydrogen evolution. Towards this end, promising HER characteristics have been reported using 2H (trigonal prismatic) XS2 (where X = Mo or W) nanoparticles with a high concentration of metallic edges as electrocatalysts. The key challenges for HER with XS2 are increasing the number and catalytic activity of active sites. Here we report atomically thin nanosheets of chemically exfoliated WS2 as efficient catalysts for hydrogen evolution with very low overpotentials. Atomic-resolution transmission electron microscopy and spectroscopy analyses indicate that enhanced electrocatalytic activity of WS2 is associated with high concentration of strained metallic 1T (octahedral) phase in the as-exfoliated nanosheets. Density functional theory calculations reveal that the presence of strain in the 1T phase leads to an enhancement of the density of states at the Fermi level and increases the catalytic activity of the WS2 nanosheet. Our results suggest that chemically exfoliated WS2 nanosheets could be interesting catalysts for hydrogen evolution.
Chemically and mechanically exfoliated MoS$_2$ single-layer samples have substantially different properties. While mechanically exfoliated single-layers are mono-phase (1H polytype with Mo in trigonal prismatic coordination), the chemically exfoliate
We report piezoelectric response in liquid phase exfoliated MoS2 nanosheets with desired structure and morphology. The piezoelectric effect in liquid phase exfoliated few layers of MoS2 flakes is interesting as it may allow the scalable fabrication o
Monolayers of Transition Metal Dichalcogenides (TMDs) are atomically thin two-dimensional crystals with attractive optoelectronic properties, which are promising for emerging applications in nanophotonics. Here, we report on the extraordinary spatial
Laterally large (~3 micrometers), atomically-thin two-dimensional (2D) Bi2O2CO3 nanosheets (2D bismuth oxycarbonate, 2D bismutite) are fabricated via sonochemically-assisted template-free synthesis. Key to the synthesis of the freestanding, laterally
Single- and few-layered InSe flakes are produced by the liquid-phase exfoliation of beta-InSe single crystals in 2-propanol, obtaining stable dispersions with a concentration as high as 0.11 g/L. Ultracentrifugation is used to tune the morphology, i.