Low dimensional materials have been examined as electrocatalysts for the hydrogen evolution reaction (HER). Among them, two-dimensional Transition Metal Dichalcogenides (2D-TMDs) such as MoS 2 have been identified as potential candidates. However, the performance of TMDs towards HER in both acidic and basic media remains inferior to that of noble metals such as Pt and its alloys. This calls for investigating the influence of controlled defect engineering of 2D Hydrothermal synthesis 6.5ű0.04

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We compare the main feature of the measured Raman scattering spectra from single layer graphene with a bilayer in which the two layers are arbitrarily misoriented. The profiles of the 2D bands are very similar having only one component, contrary to the four found for commensurate Bernal bilayers. These results agree with recent theoretical calculations and point to the similarity of the electronic structures of single layer graphene and misoriented bilayer graphene. Another new aspect is that the dependance of the 2D frequency on the laser excitation energy is different in these two latter systems.

Nanolaminate membranes made of two-dimensional materials (2D) such as graphene oxide (GO) are promising candidates for molecular sieving via size-limited diffusion in the 2D capillaries, but high hydrophilicity makes these membranes unstable in water. Here, we 25 report a nanolaminate membrane based on covalently functionalized molybdenum disulfide (MoS 2 ) nanosheets. The functionalized MoS 2 membranes demonstrate >90% and ~ 87% rejection for micropollutants and NaCl respectively when operating under reverse osmotic conditions. The sieving performance and water flux of the functionalized MoS 2 membranes are attributed to both control of the capillary widths of the nanolaminates and 30 control of the surface chemistry of the nanosheets. We identified small hydrophobic 20 12 References

Hexagonal boron nitride is a model lamellar compound where weak, non-local van der Waals interactions ensure the vertical stacking of two-dimensional honeycomb lattices made of strongly bound boron and nitrogen atoms. We study the isotope engineering of lamellar compounds by synthesizing hexagonal boron nitride crystals with nearly pure boron isotopes (B and B) compared to those with the natural distribution of boron (20 at%B and 80 at% B). On the one hand, as with standard semiconductors, both the phonon energy and electronic bandgap varied with the boron isotope mass, the latter due to the quantum effect of zero-point renormalization. On the other hand, temperature-dependent experiments focusing on the shear and breathing motions of adjacent layers revealed the specificity of isotope engineering in a layered material, with a modification of the van der Waals interactions upon isotope purification. The electron density distribution is more diffuse between adjacent layers inBN than in BN crystals. Our results open perspectives in understanding and controlling van der Waals bonding in layered materials.

We perform transmission electron microscopy, electron diffraction, and Raman scattering experiments on an individual suspended double-walled carbon nanotube (DWCNT). The first two techniques allow the unambiguous determination of the DWCNT structure: (12,8)@(16,14). However, the low-frequency features in the Raman spectra cannot be connected to the derived layer diameters d by means of the 1/d power law, widely used for the diameter dependence of the radial-breathing mode of single-walled nanotubes. We discuss this disagreement in terms of mechanical coupling between the layers of the DWCNT, which results in collective vibrational modes. Theoretical predictions for the breathing-like modes of the DWCNT, originating from the radial-breathing modes of the layers, are in a very good agreement with the observed Raman spectra. Moreover, the mechanical coupling qualitatively explains the observation of Raman lines of breathing-like modes, whenever only one of the layers is in resonance with the laser energy.

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We carried out a complete study (magnetic, electronic, dielectric, dynamic, and elastic properties) of the nickel hydroxide [Ni(OH)2] from first-principles calculations based on density functional theory. No theoretical investigations of these physical properties have been previously reported in literature. Our work supports that Ni(OH)2 is an A-type antiferromagnetic material. In addition, it is negative uniaxial and semiconducting with a direct band gap at the Γ point around 3 eV. By contrast to its electronic dielectric tensor, its static tensor is strongly anisotropic in the plane orthogonal to its optical axis. This anisotropy is mainly governed by a highly polar phonon centered around 510 cm−1 and assigned as a rotational Eu mode. Both Raman and infrared spectra have been computed to clarify the longstanding debate on the assignment of the Ni(OH)2 phonon modes reported in literature. All these theoretical results are fruitfully compared to the experimental ones obtained on large Ni(OH)2 "pseudosingle" crystals when available