Oscillations of the Spacing between van Hove Singularities Induced by sub-Ångstrom Fluctuations of Interlayer Spacing in Graphene Superlattices

We report the thermal stability of spherically shaped cobalt-promoted molybdenum disulfide (Co/MoS2) nano-catalysts from in-situ heating under electron irradiation in the scanning transmission electron microscope (STEM) from room temperature to 550 °C ± 50 °C with aid of Fusion® holder (Protochip©, Inc.). The catalytic nanoparticles were synthesized via a hydrothermal method using sodium molybdate (Na2MoO4·2H2O) with thioacetamide (CH3CSNH2) and cobalt chloride (CoCl2) as promoter agent. The results indicate that the layered molybdenum disulfide structure with interplanar distance of ~0.62 nm remains stable even at temperatures of 550 °C, as observed in STEM mode. Subsequently, the samples were subjected to catalytic tests in a Robinson Mahoney Reactor using 30 g of Heavy Crude Oil (AGT-72) from the golden lane (Mexico’s east coast) at 50 atm using (ultrahigh purity) UHP hydrogen under 1000 rpm stirring at 350 °C for 8 h. It was found that there is no damage on the laminar stacking of Co/MoS2 with temperature, with interlayer spacing remaining at 0.62 nm; these sulfided catalytic materials led to aromatics rise of 22.65% and diminution of asphaltenes and resins by 15.87 and 3.53%, respectively.

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Broadening of van Hove Singularities Measured by Photoemission Spectroscopy of Single- and Mixed-Chirality Single-Walled Carbon Nanotubes

The Journal of Physical Chemistry C ◽

10.1021/acs.jpcc.9b07975 ◽

2019 ◽

Vol 123 (43) ◽

pp. 26683-26694

Author(s):

Cameron J. Shearer ◽

LePing Yu ◽

Adam J. Blanch ◽

Ming Zheng ◽

Gunther G. Andersson ◽

...

Keyword(s):

Carbon Nanotubes ◽

Single Walled Carbon Nanotubes ◽

Photoemission Spectroscopy ◽

Van Hove Singularities ◽

Single Walled Carbon ◽

Walled Carbon Nanotubes

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Free-standing reduced graphene oxide (rGO) membrane for salt-rejecting solar desalination via size effect

Nanophotonics ◽

10.1515/nanoph-2020-0396 ◽

2020 ◽

Vol 9 (15) ◽

pp. 4601-4608 ◽

Cited By ~ 1

Author(s):

Pengyu Zhuang ◽

Hanyu Fu ◽

Ning Xu ◽

Bo Li ◽

Jun Xu ◽

...

Keyword(s):

Graphene Oxide ◽

Reduced Graphene Oxide ◽

Conversion Efficiency ◽

High Salinity ◽

Interlayer Spacing ◽

Structural Instability ◽

Solar Thermal ◽

Free Standing ◽

Solar Desalination ◽

Reduced Graphene

AbstractInterfacial solar vapor generation has revived the solar-thermal-based desalination due to its high conversion efficiency of solar energy. However, most solar evaporators reported so far suffer from severe salt-clogging problems during solar desalination, leading to performance degradation and structural instability. Here, we demonstrate a free-standing salt-rejecting reduced graphene oxide (rGO) membrane serving as an efficient, stable, and antisalt-fouling solar evaporator. The evaporation rate of the membrane reaches up to 1.27 kg m−2 h−1 (solar–thermal conversion efficiency ∼79%) under one sun, out of 3.5 wt% brine. More strikingly, due to the tailored narrow interlayer spacing, the rGO membrane can effectively reject ions, preventing salt accumulation even for high salinity brine (∼8 wt% concentration). With enabled salt-antifouling capability, flexibility, as well as stability, our rGO membrane serves as a promising solar evaporator for high salinity brine treatment.

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Nitration of Jharia basin coals, India: a study of structural modifications by XRD and FTIR techniques

International Journal of Coal Science & Technology ◽

10.1007/s40789-021-00422-8 ◽

2021 ◽

Author(s):

Prabal Boral ◽

Atul K. Varma ◽

Sudip Maity

Keyword(s):

Acetic Acid ◽

Nitric Acid ◽

Linear Relationship ◽

Glacial Acetic Acid ◽

Vitrinite Reflectance ◽

Aqueous Media ◽

Interlayer Spacing ◽

Acetic Acid Medium ◽

X Ray ◽

The Media

AbstractFour coal samples from Jharia basin, India are treated with nitric acid in glacial acetic acid and aqueous media to find out the chemical, petrographic and spatial structure of the organic mass by X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) techniques. X-ray parameters of coal like interlayer spacing (d002), crystallite size (Lc), aroamticity (fa), average number of aromatic layers (Nc), and coal rank (I26/I20) have been determined using profile-fitting software. Considerable variation is observed in treated coals in comparison to the demineralized coals. The d002 values of treated coals have increased in both the media showing increase in disordering of organic moieties. A linear relationship has been observed between d002 values with the volatile matter of the coals. Similarly, the d002 values show linear relationship with Cdmf contents for demineralized as well as for the treated coals in both the media. The Lc and Nc values have decreased in treated coals corresponding to demineralized coals. The present study shows that nitration in both the media is capable of removing the aliphatic side chains from the coals and aromaticity (fa) increases with increase in rank and shows a linear relationship with the vitrinite reflectance. The corresponding I26/I20 values are least for treated coals in glacial acetic acid medium followed by raw and then to treated coals in aqueous medium. FTIR studies show that coal arenes of the raw coals are converted into nitro-arenes in structurally modified coals (SMCs) in both the media, the corresponding bands at 1550–1490 and 1355–1315 cm−1 respectively. FTIR study confirms that nitration is the predominant phenomenon, though, oxidation and nitration phenomena takes place simultaneously during treatment with nitric acid to form SMCs. In comparison to raw coals, the SMCs show higher aromaticity and may be easily converted to coal derived products like activated carbon and specialty carbon materials.

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Enhanced Reversible Zinc Ion Intercalation in Deficient Ammonium Vanadate for High-Performance Aqueous Zinc-Ion Battery

Nano-Micro Letters ◽

10.1007/s40820-021-00641-3 ◽

2021 ◽

Vol 13 (1) ◽

Author(s):

Quan Zong ◽

Wei Du ◽

Chaofeng Liu ◽

Hui Yang ◽

Qilong Zhang ◽

...

Keyword(s):

High Performance ◽

Coulombic Efficiency ◽

Specific Capacity ◽

Interlayer Spacing ◽

Zinc Ion ◽

Carbon Cloth ◽

High Specific Capacity ◽

Irreversible Reaction ◽

Ammonium Vanadate ◽

Structure Degradation

AbstractAmmonium vanadate with bronze structure (NH4V4O10) is a promising cathode material for zinc-ion batteries due to its high specific capacity and low cost. However, the extraction of $${\text{NH}}_{{4}}^{ + }$$ NH 4 + at a high voltage during charge/discharge processes leads to irreversible reaction and structure degradation. In this work, partial $${\text{NH}}_{{4}}^{ + }$$ NH 4 + ions were pre-removed from NH4V4O10 through heat treatment; NH4V4O10 nanosheets were directly grown on carbon cloth through hydrothermal method. Deficient NH4V4O10 (denoted as NVO), with enlarged interlayer spacing, facilitated fast zinc ions transport and high storage capacity and ensured the highly reversible electrochemical reaction and the good stability of layered structure. The NVO nanosheets delivered a high specific capacity of 457 mAh g−1 at a current density of 100 mA g−1 and a capacity retention of 81% over 1000 cycles at 2 A g−1. The initial Coulombic efficiency of NVO could reach up to 97% compared to 85% of NH4V4O10 and maintain almost 100% during cycling, indicating the high reaction reversibility in NVO electrode.

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Spin–valley Hall phenomena driven by Van Hove singularities in blistered graphene

npj Computational Materials ◽

10.1038/s41524-020-00470-9 ◽

2020 ◽

Vol 6 (1) ◽

Author(s):

M. Umar Farooq ◽

Arqum Hashmi ◽

Tomoya Ono ◽

Li Huang

Keyword(s):

First Principles ◽

Opposite Sign ◽

Spin Splitting ◽

First Principles Calculations ◽

Van Hove Singularities ◽

Spin Degree ◽

Hall Effects ◽

Back Scattering ◽

Structural Deformations ◽

Spin Momentum

AbstractUsing first-principles calculations, we investigate the possibility of realizing valley Hall effects (VHE) in blistered graphene sheets. We show that the Van Hove singularities (VHS) induced by structural deformations can give rise to interesting spin–valley Hall phenomena. The broken degeneracy of spin degree of freedom results in spin-filtered VH states and the valley conductivity have a Hall plateau of ±e2/2h, while the blistered structures with time-reversal symmetry show the VHE with the opposite sign of $$\sigma _{xy}^{K/K^{\prime}}$$ σ x y K / K ′ (e2/2h) in the two valleys. Remarkably, these results show that the distinguishable chiral valley pseudospin state can occur even in the presence of VHS induced spin splitting. The robust chiral spin–momentum textures in both massless and massive Dirac cones of the blistered systems indicate significant suppression of carrier back-scattering. Our study provides a different approach to realize spin-filtered and spin-valley contrasting Hall effects in graphene-based devices without any external field.

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