Increase In Interlayer Distance Research Articles

Thin Polyamide Layer Cross-Linked Graphene-Oxide based Ceramic Membranes for Efficient Separation of the Surfactant Stabilized Oil-In-Water Emulsions

Thin Polyamide Layer Cross-Linked Graphene-Oxide based Ceramic Membranes for Efficient Separation of the Surfactant Stabilized Oil-In-Water Emulsions

Robust construction of polyvinyl alcohol intercalated graphene oxide nanofiltration membrane for desalination via pervaporation

The construction and modification of a Graphene Oxide (GO) membrane, incorporating polyvinyl alcohol (PVA) cross-linked with maleic acid (MA) and supported by a nylon membrane, have been successfully completed. Systematic variations in PVA and MA concentrations were conducted to achieve membranes with favorable characteristics, stability, and excellent desalination performance. Optimization studies utilizing the Central Composite Design (CCD) revealed that the most optimal desalination results were obtained with 10 mL of PVA (0.1 mg mL−1) and 0.9 M of MA (GO-MA0.9-PVA10/Nylon membrane). Experimental findings demonstrated that the inclusion of PVA and MA resulted in an increased interlayer distance of GO and enhanced membrane stability. The addition of PVA increases GO membrane hydrophilicity, while the addition of MA reduces membrane hydrophilicity. The GO-MA0.9-PVA10/Nylon membrane exhibited the highest desalination performance, boasting a rejection value exceeding >99.9% and a permeance of 18.76 kg m−2.h−1 under 1% NaCl feed at a temperature of 50 °C. This membrane demonstrated consistent desalination performance stability over an extended period of up to 70 h. Moreover, it exhibited durability through 8 cycles of 24-h usage with washing treatment. In conclusion, the GO-MA0.9-PVA10/Nylon membrane is strongly recommended for practical applications, outperforming other membrane options based on the comprehensive evaluation of its stability and desalination efficiency.

Unravelling K intercalation on graphene and its variants through two-dimensional cluster expansion modeling

In this study, we investigate K ordering and its impact on K intercalation and storage capacity in graphite, bilayer and single-layer graphene through two-dimensional cluster expansion implemented in first-principles calculations with van der Waals corrections. For graphite, similar to the Li counterpart, K intercalation exhibits a multistage feature as the K concentration increases from C2 to KC8. However, beyond KC8, K atoms become crowded in graphite, resulting in a negative discharge voltage. For bilayer and single-layer graphene, a noticeable displacement of K from original hexagonal sites occurs at higher K concentrations compared to graphite. K intercalation in graphite after the initial segment (from C2 to KC8) leads to an increase in interlayer distance, while in bilayer graphene causes much larger elongation in interlayer distance. The calculated overpotential for K intercalation on bilayer and single-layer graphene is found to be 0.17 and 0.13 V, respectively, which is lower than the overpotential (0.86 V) observed on graphite. The charge redistribution between K and carbon layers indicates that bilayer and single-layer graphene offer pseudo-capacitance, facilitating faster charge transfer and higher K capacity. The above observation suggests the graphene structures have a superior K-storage capacity compared to graphite.

Studies on thermoelectric properties of sonochemically exfoliated MoS2

2D transition metal dichalcogenides (TMDs) have gained immense attention as energy materials in the past decade owing to their unique structure and properties. As the need for energy is increasing at a great pace, the search for new and sustainable technologies and materials for them has increased. Thermoelectric electricity generation is one such sustainable solution as waste heat can be utilized to create electricity. Here in this article, the thermoelectric behaviour of MoS2 is studied which was exfoliated in mild/friendly solvents in a simple manner using the ultrasound energy. Such 2D materials have been studied for thermoelectric behaviour but their performance is restricted by the poor electrical conductivity. Hence, thermoelectric performance of MoS2 is often enhanced by preparing hybrids with other materials such as graphene, carbon fibre or by metal doping. However, herein the overall power factor was highly increased via a simple method attributing to the increased interlayer distance and phase change which was seen in XRD, Raman and XPS. MoS2 exfoliated in water resulted in power factor of 68.34 μW m−1K−2 at room temperature and highest power factor was obtained in case of exfoliation in DMF (310 μW m−1K−2). The cross-plane thermal conductivity also reduced about 5 times as compared to the bulk material.

Extreme Thermal Insulation and Tradeoff of Thermal Transport Mechanisms between Graphene and WS2 Monolayers.

Controlling and understanding the heat flow at a nanometer scale are challenging, but important for fundamental science and applications. Two-dimensional (2D) layered materials provide perhaps the ultimate solution for meeting these challenges. While there have been reports of low thermal conductivities (several mW m-1 K-1) across the 2D heterostructures, phonon-dominant thermal transport remains strong due to the nearly-ideal contact between the layers. Here, this work experimentally explores the heat transport mechanisms by increasing the interlayer distance from perfect contact to a few nanometers and demonstrates that the phonon-dominated thermal conductivity across the WS2/graphene interface decreases further with the increasing interlayer distance until the air-dominated thermal conductivity increases again. This work finds that the resulting tradeoff of the two heat conduction mechanisms leads to the existence of a minimum thermal conductivity at 2.11nm of 1.41×10-5W m-1 K-1, which is two thousandths of the smallest value reported previously. This work provides an effective methodology for engineering thermal insulation structures and understanding heat transport at the ultimate small scales.

Polyaniline spaced MoS2 nanosheets with increased interlayer distances for constructing high-rate dual-ion batteries

Dual-ion batteries (DIBs) have attracted great attention due to their affordable prices, environmental friendliness, and high operating voltage. However, the conventional graphite anode in DIBs has drawbacks such as unsatisfactory capacity and worrying safety. MoS2 is considered to be a competitive anode material that exhibits large capacity due to its unique layered structure for cation insertion/extraction. Nevertheless, the sluggish reaction kinetics of MoS2 does not match the cathode side, which makes the constructed full DIBs show poor rate ability. Here, a flower-like MoS2/ polyaniline composite electrode (MoS2-PANI) where PANI was grown in situ between layers of MoS2 nanosheets was designed. In this design, the inserted PANI can broaden the layer distance of MoS2 to facilitate cation diffusion and prevent the restacking of nanosheets. Furthermore, PANI is also expected to increase the conductivity and relieve the volume changes during repeated charge/discharge cycles. Benefiting from that, the MoS2-PANI electrode delivered a reversible capacity of 561.91 mA h g–1 at 5 A g–1 in half-cell test. Moreover, when coupled with a mildly expanded graphite (MEG) cathode, the obtained MEG//MoS2-PANI DIB shows excellent rate ability with a reversible discharge capacity of 86.62 mA h g–1 and a desirable energy density of 308.83 W h kg–1 at 20 C. These results provide some inspiration for the design of high-rate DIBs.

Large interlayer spacing enabling long life vanadium-based aqueous zinc battery in zinc sulfate electrolyte

Layered vanadium oxides (V2O5) as cathode for aqueous zinc-ion batteries (ZIBs) have attracted a lot of interest due to their large theoretical capacity. However, V2O5 cathode suffers from the collapse of layered structure after long cycles in ZnSO4 electrolyte due to the repeated intercalation/deintercalation of large-size hydrated Zn2+. Herein, we design V2O5 @Phenylbutylamine (V2O5 @PBA) with large interlayer spacing for inexpensive ZnSO4 electrolytes. Between the V-O layers, a remarkable increase in interlayer distance (16.4 Å) can be constructed, providing a path for facile hydrated Zn2+ diffusion. The V2O5 @PBA cathode exhibits high specific capacity (387 mAh g−1), superior rate performance and long cycle life (retention of 64 % after 3000 cycles) in ZnSO4 electrolytes, which is much better than that of layered V2O5 cathode (interlayer distance: 11.5 Å). These results show that increasing the large interlayer spacing strategy is an effective way to improve the electrochemical performance of vanadium oxide cathode in ZnSO4 electrolyte.

Ionic transport through a bilayer nanoporous graphene with cationic and anionic functionalization.

Understanding the ionic transport through multilayer nanoporous graphene (NPG) holds great promise for the design of novel nanofluidic devices. Bilayer NPG with different structures, such as nanopore offset and interlayer space, should be the most simple but representative multilayer NPG. In this work, we use molecular dynamics simulations to systematically investigate the ionic transport through a functionalized bilayer NPG, focusing on the effect of pore functionalization, offset, applied pressure and interlayer distance. For a small interlayer space, the fluxes of water and ions exhibit a sudden reduction to zero with the increase in offset that indicates an excellent on-off gate, which can be deciphered by the increasing potential of mean force barriers. With the increase in pressure, the fluxes increase almost linearly for small offsets while always maintain zero for large offsets. Finally, with the increase in interlayer distance, the fluxes increase drastically, resulting in the reduction in ion rejection. Notably, for a specific interlayer distance with monolayer water structure, the ion rejection maintains high levels (almost 100% for coions) with considerable water flux, which could be the best choice for desalination purpose. The dynamics of water and ions also exhibit an obvious bifurcation for cationic and anionic functionalization. Our work comprehensively addresses the ionic transport through a bilayer NPG and provides a route toward the design of novel desalination devices.

Converting the Bulk Transition Metal Dichalcogenides Crystal into Stacked Monolayers via Ethylenediamine Intercalation.

We report the synthesis of ethylenediamine-intercalated NbSe2 and Li-ethylenediamine-intercalated MoSe2 single crystals with increased interlayer distances and their electronic structures measured by means of angle-resolved photoemission spectroscopy (ARPES). X-ray diffraction patterns and transmission electron microscopy images confirm the successful intercalation and an increase in the interlayer distance. ARPES measurement reveals that intercalated NbSe2 shows an electronic structure almost identical to that of monolayer NbSe2. Intercalated MoSe2 also returns the characteristic feature of the monolayer electronic structure, a direct band gap, which generates sizable photoluminescence even in the bulk form. Our results demonstrate that the properties and phenomena of the monolayer transition metal dichalcogenides can be achieved with large-scale bulk samples by blocking the interlayer interaction through intercalation.

Synthesizing Conducting Poly(Aniline-co-Aminoacetophenone) Nanocomposites based on Polyhydroxy Iron Cation–modified Clay

Abstract: Conductive clay–polymer nanocomposites were prepared via the in situ polymerization of aminoacetophenone and/or aniline monomers (at initial “aminoacetophenone:aniline”) in the presence of polyhydroxy iron cation–modified montmorillonite (MMT-PIC). Fourier transform infrared spectroscopy analysis demonstrated the characteristic bands of the MMT-PIC polymers/copolymers. The morphological properties analyzed and imaged through X-ray diffraction and scanning electron microscopy, respectively, displayed an increasing interlayer distance with the mass loading of PIC and poly(aminoacetophenone-co-aniline) (poly(AAP-co-ANI)), affording intercalated nanocomposites. Energy-dispersive X-ray spectroscopy measurements revealed that the clay experienced a cation exchange of sodium by the PIC, and poly(AAP-co-ANI) was present in large amounts on the nanocomposite surface. The electrical conductivity of the obtained nanocomposites was 5.760 × 10−5 S⋅cm−1. Moreover, the electrochemical behavior of the polymers extracted from the nanocomposites was studied via cyclic voltammetry; the redox processes indicated that the polymerization into activated carbon produced electroactive polymers.

Drag resistivity in double-layer gapped graphene structures

We study the frictional drag phenomenon in a double-layer system made of two parallel gapped graphene layers by calculating the Coulomb drag resistivity. The random-phase approximation is employed to determine the polarizability functions of layers and the frequency-dependent dielectric function of the structure. Our computations illustrate that the Coulomb drag resistivity in double-layer gapped graphene systems show some interesting different features, compared to that in other double-layer ones. Coulomb drag resistivity in the system steadily increases as temperature increases but quickly decreases with the increase in interlayer distance. With small interlayer separations, the drag resistivity behaves as a smoothly increasing function of the bandgap. Nevertheless, with sufficiently large separations, the Coulomb drag resistivity increases with small bandgaps but decreases with larger ones. We observe that a finite bandgap has remarkable contributions to the frictional drag phenomenon, therefore it is necessary to take into account this factor in calculations to make better agreements with experimental works.

Mechanochemical Pretreated Mn+1AXn (MAX) Phase to Synthesize 2D-Ti3C2Tx MXene Sheets for High-Performance Supercapacitors.

Two-dimensional (2D) MXenes sheet-like micro-structures have attracted attention as an effective electrochemical energy storage material due to their efficient electrolyte/cation interfacial charge transports inside the 2D sheets which results in ultrahigh rate capability and high volumetric capacitance. In this article, Ti3C2Tx MXene is prepared by a combination of ball milling and chemical etching from Ti3AlC2 powder. The effects of ball milling and etching duration on the physiochemical properties are also explored, as well as the electrochemical performance of as-prepared Ti3C2 MXene. The electrochemical performances of 6 h mechanochemically treated and 12 h chemically etched MXene (BM-12H) exhibit an electric double layer capacitance behavior with an enhanced specific capacitance of 146.3 F g-1 compared to 24 and 48 h treated samples. Moreover, 5000-cycle stability tested sample's (BM-12H) charge/discharge show increased specific capacitance due to the termination of the -OH group, intercalation of K+ ion and transformation to TiO2/Ti3C2 hybrid structure in a 3 M KOH electrolyte. Interestingly, a symmetric supercapacitor (SSC) device fabricated in a 1 M LiPF6 electrolyte in order to extend the voltage window up to 3 V shows a pseudocapacitance behavior due to Li on interaction/de-intercalation. In addition, the SSC shows an excellent energy and power density of 138.33 W h kg-1 and 1500 W kg-1, respectively. The ball milling pre-treated MXene exhibited an excellent performance and stability due to the increased interlayer distance between the MXene sheets and intercalation and deintercalation of Li+ ions.

Improving the Cycling Stability of Aqueous Zinc-Ion Batteries by Preintercalation of Polyaniline in Hydrated Vanadium Oxide.

This paper reports the synthesis and characterization of hydrated vanadium oxide (VOH) and chemically preintercalated polyanilines in VOH, labeled as PAVO-H as the cathode material for aqueous zinc-ion batteries. Synthesized PAVO-H has a high surface area and rod-shaped morphology. PAVO-H has an increased interlayer distance of 13.36 Å. PAVO-H offers high specific capacities of 330 and 225 mAh g-1 at 50 mA g-1 and 4 A g-1 of current densities, respectively, with a 92% capacity retention rate of over 3000 cycles. The preintercalation of polyaniline is likely to catalyze the redox reaction and facilitate and simplify transport kinetics. It is also possible that the preintercalation of polyaniline permits the insertion of large hydrated Zn ions and reduces the formation of zinc basic salts.

Mechanical Properties of Graphene Networks under Compression: A Molecular Dynamics Simulation.

Molecular dynamics simulation is used to study and compare the mechanical properties obtained from compression and tension numerical tests of multilayered graphene with an increased interlayer distance. The multilayer graphene with an interlayer distance two-times larger than in graphite is studied first under biaxial compression and then under uniaxial tension along three different axes. The mechanical properties, e.g., the tensile strength and ductility as well as the deformation characteristics due to graphene layer stacking, are studied. The results show that the mechanical properties along different directions are significantly distinguished. Two competitive mechanisms are found both for the compression and tension of multilayer graphene-the crumpling of graphene layers increases the stresses, while the sliding of graphene layers through the surface-to-surface connection lowers it. Multilayer graphene after biaxial compression can sustain high tensile stresses combined with high plasticity. The main outcome of the study of such complex architecture is an important step towards the design of advanced carbon nanomaterials with improved mechanical properties.

Modelling the structural disorder in trigonal-prismatic coordinated transition metal dichalcogenides.

Trigonal-prismatic coordinated transition metal dichalcogenides (TMDCs) are formed from stacked (chalcogen)-(transition metal)-(chalcogen) triple layers, where the chemical bond is covalent within the triple layers and van der Waals (vdW) forces are effective between the layers. Bonding is at the origin of the great interest in these compounds, which are used as 2D materials in applications such as catalysis, electronics, photoelectronics, sensors, batteries and thermoelectricity. This paper addresses the issue of modelling the structural disorder in multilayer TMDCs. The structural model takes into account stacking faults, correlated displacement of atoms and average crystallite size/shape, and is assessed by simulation of the X-ray diffraction pattern and fitting to the experimental data relative to a powdered sample of MoS2 exfoliated and restacked via lithiation. From fitting, an average crystallite size of about 50 Å, nearly spherical crystallites and a definite probability of deviation from the fully eclipsed atomic arrangement present in the ordered structure are determined. The increased interlayer distance and correlated intralayer and interlayer atomic displacement are attributed to the presence of lithium intercalated in the vdW gap between triple layers (Li/Mo molar ratio of about 0.06). The model holds for the whole class of trigonal-prismatic coordinated TMDCs, and is suitably flexible to take into account different preparation routes.

Enhancing cation storage performance of layered double hydroxides by increasing the interlayer distance.

Layered double hydroxides (LDH) can be transformed from alkaline supercapacitor material into metal-cation storage cathode working in neutral electrolytes through electrochemical activation. However, the rate performance for storing large cations is restricted by the small interlayer distance of LDH. Herein, the interlayer distance of NiCo-LDH is expanded by replacing the interlayer nitrate ions with 1,4-benzenedicarboxylic anions (BDC), leading to the enhanced rate performance for storing large cations (Na+, Mg2+, and Zn2+), whereas almost the unchanged one for storing small-radius Li+ ions. The improved rate performance of the BDC-pillared LDH (LDH-BDC) stems from the reduced charge-transfer and Warburg resistances during charge/discharge due to the increased interlayer distance, as revealed by in situ electrochemical impedance spectra. The asymmetric zinc-ion supercapacitor assembled with LDH-BDC and activated carbon presents high energy density and cycling stability. This study demonstrates an effective strategy to improve the large cation storage performance of LDH electrodes by increasing the interlayer distance.

Sodium Diffusion in Hard Carbon Studied by Small- and Wide-Angle Neutron Scattering and Muon Spin Relaxation

Hard carbon is the most common anode material for Na-ion battery. The structure of the hard carbon and the dynamics of Na-ion in hard carbon were studied with small- and wide-angle neutron scattering and muon spin relaxation technique. The neutron scattering revealed the increase of interlayer distance between graphenes and decrease of the size of nanopores with increasing sodium intercalation in hard carbon. The muon spin relaxation revealed that a systematic increase in the field fluctuation rate with increasing temperature evidenced a thermally activated sodium diffusion. Assuming the two-dimensional diffusion of Na-ion in the graphene layers, the self-diffusion coefficient of Na-ion was estimated to be 2.6 × 10−11 cm2/s at 310 K, with a thermal activation energy of 39(7) meV.

Microstructures of Starch Granules with Different Amylose Contents and Allomorphs as Revealed by Scattering Techniques.

In this study, as-is (ca. 12% moisture by mass) and hydrated (50% water by mass) granules of waxy potato (WP), waxy wheat (WW), waxy maize, normal maize, and high-amylose maize (HAM) starches were investigated by using small-angle neutron and X-ray scattering (SANS and SAXS), wide-angle X-ray scattering, and ultra-small-angle neutron scattering. The SANS and SAXS data were fitted using the two-phase stacking model of alternating crystalline and amorphous layers. The partial crystalline lamellar structures inside the growth rings of granules were analyzed based on the inter-lamellar distances, thicknesses of the crystalline lamellae and amorphous layers, thickness polydispersities, and water content in each type of layer. Despite having a longer average chain length of amylopectin, the WP and HAM starches, which had B-type allomorph, had a shorter inter-lamellar distance than the other three starches with A-type allomorph. The WP starch had the most uniform crystalline lamellar thickness. After hydration, the amorphous layers were expanded, resulting in an increase of inter-layer distance. The low-angle intensity upturn in SANS and SAXS was attributed to scattering from interfaces/surfaces of larger structures, such as growth rings and macroscopic granule surfaces. Data analysis methods based on model fitting and 1D correlation function were compared. The study emphasized─owing to inherent packing disorder inside granules─that a comprehensive analysis of different parameters was essential in correlating the microstructures with starch properties.

A facile single‐step approach to achieve in situ expanded g‐C3N4 for improved photodegradation performance

AbstractImproved graphitic carbon nitride (g‐C3N4) was synthesized through a unique one‐step cost‐effective technique involving a dynamic gas bubbling phenomenon using ammonium chloride (NH4Cl) as a bubbling agent. An extensive investigation was carried out to optimize the weight ratio of NH4Cl and melamine during the thermal pyrolysis process. Here, we report an improved form of g‐C3N4 namely “expanded g‐C3N4” with increased interlayer distance and remarkable volume expansion. The surface area of this improved version has notably increased leading to higher photocatalytic efficiency as compared with its counterpart, an synthesized without adding NH4Cl. Synthesized photocatalyst materials were further used to study the Rhodamine B photodegradation under visible light. It was observed that the expanded g‐C3N4 showed a 2.4 times higher photodegradation rate than its counterpart and degraded 94% of the dye in just 30 min.

A note on using expanded graphite for achieving energy‐ and time‐efficient production of graphene nanoplatelets via liquid phase exfoliation

AbstractAlthough easily scalable, the production of graphene nanoplatelets (GNP) by the means of liquid‐phase exfoliation of graphite flakes (GF) remains an energy‐ and time‐intensive process. In this work, we demonstrate that significant time and energy can be saved in GNP production when employing expanded graphite (EG) in a surfactant‐assisted liquid phase exfoliation process. Owing to its increased interlayer distance, the exfoliation of EG can be accomplished in a much shorter time (<30 min) compared to GF (approximately 7 h in the present case). Moreover, the energy required for the EG exfoliation is close to 80‐fold lower than that for GF exfoliation. Monitoring of the mean lateral dimension, specific surface area, and graphite flake‐to‐GNP transition during exfoliation was performed experimentally using several analytical techniques. The EG‐derived GNPs are produced much faster and require less energy for exfoliation compared to GF, thus making it a more efficient alternative technique.