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(39) Production(s) de l'année 2019
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Role of Sulfur Vacancies and Undercoordinated Mo Regions in MoS 2 Nanosheets toward the Evolution of Hydrogen
Auteur(s): Li Lei, Qin Zhaodan, Ries Lucie, Hong Song, Michel T., Yang Jieun, Salameh Chrystelle, Bechelany Mikhael, Miele Philippe, Kaplan Daniel, Chhowalla Manish, Voiry Damien
(Article) Publié:
Acs Nano, vol. 13 p.6824-6834 (2019)
Texte intégral en Openaccess :
Ref HAL: hal-02394936_v1
DOI: 10.1021/acsnano.9b01583
WoS: 000473248300066
Exporter : BibTex | endNote
70 Citations
Résumé: 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 MoS2 have been identified as potential candidates. However, the performance of TMDs toward 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 TMDs on their performance toward hydrogen production. Here, we explored the HER activity from defective multilayered MoS2 over a large range of surface S vacancy concentrations up to 90%. Amorphous MoS2 and 2H MoS2 with ultrarich S vacancies demonstrated the highest HER performance in acid and basic electrolytes, respectively. We also report that the HER performance from multilayered MoS2 can be divided into two domains corresponding to "point defects" at low concentrations of surface S vacancies (Stage 1) and large regions of undercoordinated Mo atoms for high concentrations of surface S vacancies (Stage 2). The highest performance is obtained for Stage 2 in the presence of undercoordinated Mo atoms with a TOF of similar to 2 s(-1) at an overpotential of 160 mV in 0.1 M KOH which compares favorably to the best results in the literature. Overall, our work provides deeper insight on the HER mechanism from defected MoS2 and provides guidance for the development of defect-engineered TMD-based electrocatalysts.
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Chirality manifestation in elastic coupling between the layers of double-walled carbon nanotubes
Auteur(s): Rochal Sergei, Levshov D., Avramenko Marina, Arenal Raul, Cao Thi Thanh, Nguyen van Chuc, Sauvajol J.-L., Paillet M.
(Article) Publié:
Nanoscale, vol. 11 p.16092-16102 (2019)
Texte intégral en Openaccess :
Ref HAL: hal-02373559_v1
DOI: 10.1039/c9nr03853a
WoS: WOS:000483691300033
Exporter : BibTex | endNote
1 Citation
Résumé: A search for new relatively easy physicochemical methods for structural identification of carbon nanotubes represents a key challenge. Here, analyzing the experimental data on double-walled carbon nanotubes (DWCNTs) obtained by us and taken from literature, we have expressed the magnitude of elastic coupling between two tubular walls forming a DWCNT as a simple function dependent not only on DWCNT diameters but also on the difference between the chirality angles of the constituent nanotubes. To get this quite unexpected result, which allows us to relate more precisely the structural parameters of a DWCNT with frequencies of its radial breathing-like modes (RBLM), we have developed a new model for the RBLM dynamics that takes into account a possible deposition of water molecules from ambient air onto the DWCNT surface. The comparison between theoretical and experimental RBLM frequencies allows the evaluation of the handedness-dependent contribution in elastic coupling between the layers suggesting that, in the formation of DWCNTs, the layers with the same handedness are privilegeted. Application of the results for identification of DWCNTs is also considered.
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Correction to: Surface and porous textural properties of silica-wollastonite composites prepared by sol-gel process (vol 90, pg 113, 2019)
Auteur(s): Larreal de Hernandez Lismarihen, Anez-Borges Liz, Woignier Thierry, Alaoui Adil Hafidi, Etienne-Calas S., Despetis F., Bonnet L., Colaiocco B., Tahir S., Dieudonne-George P.
(Article) Publié:
Journal Of Sol-Gel Science And Technology, vol. 90 p.126-126 (2019)
Texte intégral en Openaccess :
Ref HAL: hal-02367687_v1
DOI: 10.1007/s10971-019-04952-1
WoS: WOS:000466160600014
Exporter : BibTex | endNote
Résumé: Silica-wollastonite xerogel composites (xerocomposites) with different wollastonite filler content were obtained after classical drying of silica-wollastonite gels. Two different silica precursors were used, TEOS and colloidal LUDOX, for composites named TW and LW, respectively. We utilized SAXS experiments, N2 adsorption-desorption, and SEM techniques to determine the textural and structural properties of these porous materials. For both the TW and LW composites, it was shown that a macroporosity and a mesoporosity coexist. We argue that the proportion of macroporosity directly depends on the proportion of wollastonite fillers in the composite. We propose a unique two-stage drying mechanism to explain the formation of macropores. We additionally found that the surface of wollastonite fillers was covered by a dense multilayer packing of silica colloids in LUDOX LW xerocomposites. We believe that these surface-modified wollastonite fillers could improve the carbonation kinetics of wollastonite when used as a precursor for aqueous mineral carbonation, a promising route for safe and durable carbon sequestration.
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Layering Transition in Superfluid Helium Adsorbed on a Carbon Nanotube Mechanical Resonator
Auteur(s): Noury A., Vergara-Cruz Jorge, Morfin Pascal, Plaçais Bernard, Gordillo Maria, Boronat Jordi, Balibar Sebastien, Bachtold Adrian
(Article) Publié:
Physical Review Letters, vol. 122 p. (2019)
Texte intégral en Openaccess :
Ref HAL: hal-02318660_v1
PMID 31075030
DOI: 10.1103/PhysRevLett.122.165301
WoS: 000466439100004
Exporter : BibTex | endNote
10 Citations
Résumé: Helium is recognized as a model system for the study of phase transitions. Of particular interest is the superfluid phase in two dimensions. We report measurements on superfluid helium films adsorbed on the surface of a suspended carbon nanotube. We measure the mechanical vibrations of the nanotube to probe the adsorbed helium film. We demonstrate the formation of helium layers up to five atoms thickness. Upon increasing the vapor pressure, we observe layer-by-layer growth with discontinuities in both the number of adsorbed atoms and the speed of the third sound in the adsorbed film. These hitherto unobserved discontinuities point to a series of first-order layering transitions. Our results show that helium multilayers adsorbed on a nanotube are of unprecedented quality compared to previous works. They pave the way to new studies of quantized superfluid vortex dynamics on cylindrical surfaces, of the Berezinskii-Kosterlitz-Thouless phase transition in this new geometry, and perhaps also to supersolidity in crystalline single layers as predicted in quantum Monte Carlo calculations.
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Enhanced sieving from exfoliated MoS2 membranes via covalent functionalization
Auteur(s): Ries Lucie, Petit Eddy, Michel T., Diogo Cristina Coelho, Gervais Christel, Salameh Chrystelle, Bechelany Mikhael, Balme Sébastien, Miele Philippe, Onofrio Nicolas, Voiry Damien
(Article) Publié:
Nature Materials, vol. 18 p.1112-1117 (2019)
Texte intégral en Openaccess :
Ref HAL: hal-02310531_v1
DOI: 10.1038/s41563-019-0464-7
WoS: 000486618800021
Exporter : BibTex | endNote
35 Citations
Résumé: Nanolaminate membranes made of two-dimensional materials such as graphene oxide are promising candidates for molecular sieving via size-limited diffusion in the two-dimensional capillaries, but high hydrophilicity makes these membranes unstable in water. Here, we report a nanolaminate membrane based on covalently functionalized molybdenum disulfide (MoS2) nanosheets. The functionalized MoS2 membranes demonstrate >90% and similar to 87% rejection for micropollutants and NaCl, respectively, when operating under reverse osmotic conditions. The sieving performance and water flux of the functionalized MoS2 membranes are attributed both to control of the capillary widths of the nanolaminates and to control of the surface chemistry of the nanosheets. We identify small hydrophobic functional groups, such as the methyl group, as the most promising for water purification. Methyl- functionalized nanosheets show high water permeation rates as confirmed by our molecular dynamic simulations, while maintaining high NaCl rejection. Control of the surface chemistry and the interlayer spacing therefore offers opportunities to tune the selectivity of the membranes while enhancing their stability
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