Interlayer Expansion Research Articles

Enhanced photocatalytic degradation of perfluorooctanoic acid by Ti3C2 MXene-derived heterojunction photocatalyst: Application of intercalation strategy in DESs

In-situ construction of heterojunction photocatalyst on two-dimensional (2D) Ti3C2 MXene substrate has been proved to be a feasible method to enhance the photocatalytic degradation of organic pollutants. However, the limited interlayer spacing of 2D Ti3C2 hinders the in-situ growth of TiO2 photocatalyst. Herein, the intercalation strategy was developed in deep eutectic solvents (DESs) method to achieve interlayer expansion of Ti3C2 and improve Ti3C2-derived photocatalyst performance. Because of the intercalation of choline cations, the DESs method synthesized Ti3C2 (Ti3C2-DES) had the larger c-lattice parameter than that of traditional HF method synthesized Ti3C2 (Ti3C2-HF). The interlayer space of Ti3C2-DES could be intercalated with more water molecule for oxidization of the Ti atoms, which remarkably promoted the in-situ growth of TiO2 crystals. The formed heterojunction between (001) and (101) facets enhanced carriers separation. The Ti3C2 substrate with excellent conductivity further promoted carriers transfer. As a result, Ti3C2/TiO2 photocatalyst exhibited superior perfluorooctanoic acid (PFOA) removal performance (almost 100% removal efficiency and 49% defluorination efficiency within 16 h) compared with the traditional Ti3C2-HF/TiO2 (22% removal efficiency and 12% defluorination efficiency within 16 h). This study provides a feasible strategy for enhancing photocatalytic degradation of PFOA by Ti3C2 MXene-derived heterojunction photocatalyst.

MoS2-Carbon Inter-overlapped Structures as Effective Electrocatalysts for the Hydrogen Evolution Reaction.

The ability to generate hydrogen in an economic and sustainable manner is critical to the realization of a future hydrogen economy. Electrocatalytic water splitting into molecular hydrogen using the hydrogen evolution reaction (HER) provides a viable option for hydrogen generation. Consequently, advanced non-precious metal based electrocatalysts that promote HER and reduce the overpotential are being widely researched. Here, we report on the development of MoS2-carbon inter-overlapped structures and their applicability for enhancing electrocatalytic HER. These structures were synthesized by a facile hot-injection method using ammonium tetrathiomolybdate ((NH4)2MoS4) as the precursor and oleylamine (OLA) as the solvent, followed by a carbonization step. During the synthesis protocol, OLA not only plays the role of a reacting solvent but also acts as an intercalating agent which enlarges the interlayer spacing of MoS2 to form OLA-protected monolayer MoS2. After the carbonization step, the crystallinity improves substantially, and OLA can be completely converted into carbon, thus forming an inter-overlapped superstructure, as characterized in detail using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). A Tafel slope of 118 mV/dec is obtained for the monolayer MoS2-carbon superstructure, which shows a significant improvement, as compared to the 202 mV/dec observed for OLA-protected monolayer MoS2. The enhanced HER performance is attributed to the improved conductivity along the c-axis due to the presence of carbon and the abundance of active sites due to the interlayer expansion of the monolayer MoS2 by OLA.

Accommodation of a Large Amount of Lithium Ions in Silsesquioxane-pillared Carbon: A Potential Anode of an All-solid-state Lithium Ion Battery

More than 25 weight percent of lithium ions were accommodated in silsesquioxane-pillared carbon with very small interlayer expansion. It delivered reversible capacity of 1023 mAh/g with a relatively high first columbic efficiency of 67% and good cycling property as an anode of an all-solid-state lithium ion battery.

Generalized Methodology for Inserting Metal Heteroatoms into the Layered Zeolite Precursor RUB-36 by Interlayer Expansion

The incorporation of metal heteroatoms into zeolites is an effective modification strategy for enhancing their catalytic performance. Herein, for the first time we report a generalized methodology for inserting metal heteroatoms (such as Sn, Fe, Zn, and Co) into the layered zeolite precursor RUB-36 via interlayer expansion by using the corresponding metal acetylacetate salt. Through this generalized methodology, Sn-JHP-1, Fe-JHP-1, Zn-JHP-1 and Co-JHP-1 zeolites could be successfully prepared by the reaction of RUB-36 and corresponding metal acetylacetate salt at 180 °C for 24 h in the presence of HCl solution. As a typical example, Sn-JHP-1 and calcined Sn-JHP-1 (Sn-JHP-2) zeolite is well characterized by the X-ray diffraction (XRD), diffuse reflectance ultraviolet-visible (UV-Vis), inductively coupled plasma (ICP), N2 sorption, temperature-programmed-desorption of ammonia (NH3-TPD) and X-ray photoelectron spectroscopy (XPS) techniques, which confirm the expansion of adjacent interlayers and thus the incorporation of isolated Sn sites within the zeolite structure. Notably, the obtained Sn-JHP-2 zeolite sample shows enhanced catalytic performance in the conversion of glucose to levulinic acid (LA) reaction.

Interlayer-expanded MoS2 nanosheets/nitrogen-doped carbon as a high-performance anode for sodium-ion batteries

Abstract Sodium-ion batteries (SIBs) are considered promising energy storage devices owing to the abundant reserve and low-cost accessibility of Na resources. However, such batteries suffer from poor electrochemical performance due to the larger diameter of Na ions (0.106 nm). In this study, nitrogen-doped carbon-coating interlayer-expanded MoS2 porous nanosheets (MoS2@N–C) were synthesized, and their structural, morphological, and electrochemical properties were characterized. The XPS and EDS indicated the successful introduction of carbon into the MoS2 nanosheets. The interlayer spacing for (002) plane was increased from 0.62 nm to 0.78 nm corresponding to the shift toward lower angles shown in XRD. The MoS2@N–C exhibited an impressively high reversible capacity of 352 mAh/g at a current density of 100 mA/g after 200 cycles; this capacity is five times higher than that of bare MoS2. Moreover, MoS2@N–C showed excellent rate performance due to the boosted diffusion of Na ions. The observed improvement in the electrochemical performance of MoS2@N–C demonstrates that the combination of suitable composite materials and interlayer expansion are effective strategies for battery technologies based on the storage of large ions.

New zeolite-like RUB-5 and its related hydrous layer silicate RUB-6 structurally characterized by electron microscopy.

This study made use of a recently developed combination of advanced methods to reveal the atomic structure of a disordered nanocrystalline zeolite using exit wave reconstruction, automated diffraction tomography, disorder modelling and diffraction pattern simulation. By applying these methods, it was possible to determine the so far unknown structures of the hydrous layer silicate RUB-6 and the related zeolite-like material RUB-5. The structures of RUB-5 and RUB-6 contain the same dense layer-like building units (LLBUs). In the case of RUB-5, these building units are interconnected via additional SiO4/2 tetrahedra, giving rise to a framework structure with a 2D pore system consisting of intersecting 8-ring channels. In contrast, RUB-6 contains these LLBUs as separate silicate layers terminated by silanol/sil-oxy groups. Both RUB-6 and RUB-5 show stacking disorder with intergrowths of different polymorphs. The unique structure of RUB-6, together with the possibility for an interlayer expansion reaction to form RUB-5, make it a promising candidate for interlayer expansion with various metal sources to include catalytically active reaction centres.

Retraction of "Structurally Engineered Hollow Graphitized Carbon Nanocages as High-Performance Anodes for Potassium Ion Batteries".

Graphite is an attractive anode with high capacity and low cost for potassium ion batteries (PIBs), but suffers from poor cycle performance due to the large interlayer expansion during potassiation/depotassiation process. Here, we propose structurally engineered hollow graphitized carbon nanocages (HGCNs) as efficient anode materials for PIBs. The HGCNs were synthesized using a one-pot, self-template and self-graphitization approach where direct pyrolysis of nickel citrate converts citrate chains into carbon-shell and simultaneously reduces Ni2+ to form Ni metal core. This nickel core serves as not only a hard-template to create hollow-cage structure but also a catalyst to facilitate the graphitization of carbon-shell. The HGCNs synthesized at 1000 ºC (HGCN-1000), with its highly graphitized carbon-cage and developed porosity, exhibited an impressive K-storage capacity of 402.2 mAh g-1 at a current density of 30 mA g-1. The synergic combination of hollow morphology with graphitized carbon layers configured a stable structure capable of enduring extreme deformation, endowing HGCN-1000 a robust cyclic stability with a capacity retention of 95.9% over 2000 cycles at 1 A g-1. The proposed strategy provides an efficient route to combat the bottleneck cycling instability issue of graphitic carbon with hollow-graphitized carbon nanocages as promising anode materials for PIBs.

Hydrothermal-treatment desorption of cesium from clay minerals: The roles of organic acids and implications for soil decontamination

The adsorption and desorption of cesium (Cs) on clays of contaminated soil in a rhizosphere zone can be greatly affected by various biogeochemical processes, the timespans of which are usually months to years. Herein, we present several representative scenarios of the binding of Cs on diverse sites of vermiculitized biotite by controlled Cs adsorption to particles of different sizes. We investigated whether and how the fixed Cs in the different scenarios is desorbed by ambient and hydrothermal treatments with several low-molecular-weight organic acids (LMWOAs). The results showed that the sorbed Cs was discriminatively retained in the un-collapsed, partially collapsed, and thoroughly collapsed structures of vermiculites. The desorption of the sorbed Cs by hydrothermal LMWOAs extractions was easily realized in the un-collapsed structure, but was limited or minimal in the partially collapsed and thoroughly collapsed structures. The Cs desorption varied in accord with the LMWOA species applied and increased with the acid concentration, temperature, and number of treating cycles. The analysis of Cs-desorbed specimens confirmed their partial destruction and interlayer expansion, suggesting that the underlying mechanism of Cs removal by LMWOAs involves not only acid dissolution and complexation but also the accelerated weathering of clays within a short time under hydrothermal conditions. Our findings contribute novel insights into the mobility, bioavailability, and fate of Cs in contaminated soils and its removal from these soils for environmental restorations.

Understanding Powder X-ray Diffraction Profiles from Layered Minerals: The Case of Kaolinite Nanocrystals.

Powder X-ray diffraction (PXRD) techniques are widely used to characterize the nature of stacking of submicrometer-wide nanometer-thick layers that form layered mineral nanocrystals, but application of these methods to infer the in-plane configuration of the layers is difficult. Line-profile-analysis algorithms based on the Bragg equation cannot describe the broken periodicity in the stacking direction. The Debye scattering equation is an alternative approach, but it is limited by the large-scale atomistic models required to capture the multiscale nature of the layered systems. Here, we solve the Debye scattering equation for kaolinite nanocrystals to understand the contribution of different layer-stacking defects to PXRD profiles. We chose kaolinite as a case study because its approximately constant composition and lack of interlayer expansion ensure that interstitial cations and/or molecules and substitutional ions can be ignored. We investigated the structure factor change as a function of crystal structural and microstructural features such as layer structure in-plane misorientation and shift (in or out of the 2D plane) and the diameter, number, and lateral indentation of the layers. Perfect and turbostratic stacking configurations bounded the range of intensity variation for hkl and 00l reflections, as well as for any scattering angle. A unique degree of disorder was computed by the average deviation from such limiting cases, and multivariate analysis was used to interpret the observed diffraction profiles. Analysis of the data for KGa-1, KGa-2, and API-9 standard kaolinites demonstrated that the estimated densities of different stacking defects are highly correlated. In addition, analysis of API-9 particle-size fractions revealed a dispersion of four or more components in the standard sample. The results illustrate that the use of a distribution of sizes, defects, and even individual kaolinite components is necessary to accurately characterize any sample of natural kaolinite.

Diamine decorated graphene oxide film on quartz crystal microbalance for humidity-sensing analysis

Graphene oxide (GO) materials using various synthetic processes and amination were deposited on quartz crystal microbalance (QCM) device for humidity sensor application. Characteristics of various GO materials including surface morphology and functional groups were investigated by SEM images equipped with EDX, Fourier transform infrared spectra (FTIR) and Raman spectra. Hydrophilic property was identified by contact angle measurement. Mechanism of humidity-sensing performance are were adopted to analyze the moisture sensitivity of GO loaded QCM sensors ranging from 23% to 92% relative humidity. In this study, GO produced by strong reductant (NaNO3) and temperature control combined with amination process could generate much intercalate functional groups and high hydrophilic property. High adsorption of water molecules in graphene oxide produce large interlayer expansion of GO layers, resulting in crystal motional resistance increase, energy loss and broaden peak pattern. In humidity-sensing property, amine GO exhibits quick humidity response/recovery (10 s/11 s) sensitivity and high Q-factor, thus amination of GO film can be a candidate for future humidity sensor material.

Vanadium-doping in interlayer-expanded MoS2 nanosheets for the efficient electrocatalytic hydrogen evolution reaction

Synergistic modulations of vanadium doping, interlayer expansion and hybrid 1T&2H phases of few-layered MoS2 nanosheets are realized to gain structural and electronic benefits for enhanced hydrogen evolution reaction performance.

Metal–Semiconductor Phase Twinned Hierarchical MoS2 Nanowires with Expanded Interlayers for Sodium‐Ion Batteries with Ultralong Cycle Life

Sodium-ion batteries (SIBs) are considered a prospective candidate for large-scale energy storage due to the merits of abundant sodium resources and low cost. However, a lack of suitable advanced anode materials has hindered further applications. Herein, metal-semiconductor mixed phase twinned hierarchical (MPTH) MoS2 nanowires with an expanded interlayer (9.63 Å) are engineered and prepared using MoO3 nanobelts as a self-sacrificed template in the presence of a trace amount of (NH4 )6 Mo7 O24 ·4H2 O as initiator. The greatly expanded interlayer spacing accelerates Na+ insertion/extraction kinetics, and the metal-semiconductor mixed phase enhances electron transfer ability and stabilizes electrode structure during cycling. Benefiting from the structural merits, the MPTH MoS2 electrode delivers high reversible capacities of 200 mAh g-1 at 0.1 A g-1 for 200 cycles and 154 mAh g-1 at 1 A g-1 for 2450 cycles in the voltage range of 0.4-3.0 V. Strikingly, the electrode maintains 6500 cycles at a current density of 2 A g-1 , corresponding to a capacity retention of 82.8% of the 2nd cycle, overwhelming the all reported MoS2 cycling results. This study provides an alternative strategy to boost SIB cycling performance in terms of reversible capacity by virtue of interlayer expansion and structure stability.

Rose-like MoS2 nanostructures with a large interlayer spacing of ∼9.9 Å and exfoliated WS2 nanosheets supported on carbon nanotubes for hydrogen evolution reaction

In this study, we report a rose-like MoS2 and in-situ exfoliated WS2 nanoarchitecture supported on carbon nanotube networks for enhanced hydrogen evolution reaction. The interlayer expansion of MoS2 was carried out during in-situ exfoliation of WS2 nanosheets under a solvothermal process based on the ethanol-water mixture of sodium molybdate dihydrate and organosulfur chelating agent. Then, the MoS2-WS2 nanostructures are attached with carbon nanotubes (CNTs) to obtain the MoS2-WS2-CNTs nanoarchitectures where the interlayer expanded rose-like MoS2 nanostructures and the delaminated WS2 nanosheets are strongly associated with the electrically conductive carbon nanotubes, leading to a strong synergistic interaction among MoS2, WS2, and CNTs. Hence, the fabricated MoS2-WS2-CNTs nanoarchitectures delivered superior electrocatalytic activity towards the hydrogen evolution reaction (HER), yielding a current density of 10 mA cm−2 at a low overpotential of ∼212 mV with a Tafel slope of 50 mV dec−1. Such superior HER electrocatalytic activity is due to the existence of abundant catalytic active sites in the both rose-like MoS2 nanostructures with large interlayer spacing of ∼9.9 Å and exfoliated WS2 nanosheets with more edge sites, and facile electron transfer between conductive substrate and electrocatalytically active MoS2/WS2 materials through CNTs conducting channel.

Synergy of interlayer expansion and capacitive contribution promoting sodium ion storage in S, N-Doped mesoporous carbon nanofiber

Heteroatoms doping is proved to be an effective strategy to improve the electrochemical performance of carbon materials by adjusting its physical and chemical properties. In this work, sulfur, nitrogen co-doped carbon nanofiber (SNCNF) is prepared by electrospinning technique with the following heat and hydrothermal treatment route. Benefiting from the S, N co-doping, SNCNF demonstrates perfect pseudocapacitance characteristic improving rate performance (N-doping) and large interlayer distances promoting reversible insertion/extraction of Na+ (S-doping). SCNNF displays high charge-discharge specific capacity (290.3 mA h g−1 at 0.1 A g−1), superior cycling stability (247.4 mA h g−1 and 98.2% retention at 0.5 A g−1 over 600 cycles) and ultra-long circulation characteristics at high current rate (160.2 mA h g−1 at 10.0 A g−1 after 10,000 cycles), which can be served as a very promising material as anode for sodium ion batteries.

Interlayer-expanded and binder-free VS2 nanosheets assemblies for enhanced Mg2+ and Li+/Mg2+ hybrid ion storage

Magnesium ion batteries (MIBs) and magnesium/lithium hybrid ion batteries (MLIBs) are promising candidates for next-generation energy storage, due to the large capacity, abundant magnesium reserves, and safe operation. Nevertheless, the use of MIBs and MLIBs is limited by sluggish Mg2+ kinetics and Li+-dependent storage in cathode materials, respectively. Herein, an efficient interlayer expansion strategy is employed to deal with the problems in both MIBs and MLIBs based on VS2. The interlayer spacing of VS2 is enlarged to 1.0 nm by octylamine intercalations via one-pot solvothermal reaction, generating dramatically enhanced electrochemical performance in MIBs and MLIBs. Moreover, various ex situ methods are used to confirm a Li+/Mg2+ co-intercalation in the expanded VS2, with most of the capacity controlled by pseudo-capacitance. This work expands the application of interlayer expansion strategy to enhance magnesium ion and lithium/magnesium hybrid ion storage.

Ultrafast Intercalation Enabled by Strong Solvent–Host Interactions: Understanding Solvent Effect at the Atomic Level

AbstractSolvents play an essential role in many areas of chemistry and is the cornerstone of understanding reactivity in solution‐phase reactions. Solvent effects have been widely observed in intercalation reactions; however, understanding of the influence of solvents on the thermodynamics and kinetics remains largely elusive in intercalation chemistry. Now, the solvent‐dependent kinetics of ferrocene intercalation into a layered vanadyl phosphate (VOPO4⋅2 H2O) host is presented, with a special focus on primary alcohols. From methanol to 1‐hexnaol, the intercalation rate peaks in 1‐propanol (80 times faster than the slowest case in methanol). Similar kinetics of exfoliation are also found in these solvents without ferrocene. The correlation between intercalation and exfoliation is understood at atomic level by DFT calculations, which reveal the role of pre‐intercalated solvent molecules play in intralayer interactions, interlayer expansion, and layer sliding.

Ultrafast Intercalation Enabled by Strong Solvent-Host Interactions: Understanding Solvent Effect at the Atomic Level.

Solvents play an essential role in many areas of chemistry and is the cornerstone of understanding reactivity in solution-phase reactions. Solvent effects have been widely observed in intercalation reactions; however, understanding of the influence of solvents on the thermodynamics and kinetics remains largely elusive in intercalation chemistry. Now, the solvent-dependent kinetics of ferrocene intercalation into a layered vanadyl phosphate (VOPO4 ⋅2 H2 O) host is presented, with a special focus on primary alcohols. From methanol to 1-hexnaol, the intercalation rate peaks in 1-propanol (80 times faster than the slowest case in methanol). Similar kinetics of exfoliation are also found in these solvents without ferrocene. The correlation between intercalation and exfoliation is understood at atomic level by DFT calculations, which reveal the role of pre-intercalated solvent molecules play in intralayer interactions, interlayer expansion, and layer sliding.

Localized High‐Concentration Electrolytes Boost Potassium Storage in High‐Loading Graphite

AbstractReversible intercalation of potassium‐ion (K+) into graphite makes it a promising anode material for rechargeable potassium‐ion batteries (PIBs). However, the current graphite anodes in PIBs often suffer from poor cyclic stability with low coulombic efficiency. A stable solid electrolyte interphase (SEI) is necessary for stabilizing the large interlayer expansion during K+ insertion. Herein, a localized high‐concentration electrolyte (LHCE) is designed by adding a highly fluorinated ether into the concentrated potassium bis(fluorosulfonyl)imide/dimethoxyethane, which forms a durable SEI on the graphite surface and enables highly reversible K+ intercalation/deintercalation without solvent cointercalation. Furthermore, this LHCE shows a high ionic conductivity (13.6 mS cm−1) and excellent oxidation stability up to 5.3 V (vs K+/K), which enables compatibility with high‐voltage cathodes. The kinetics study reveals that K+ intercalation/deintercalation does not follow the same pathway. The potassiated graphite exhibits excellent depotassiation rate capability, while the formation of a low stage intercalation compound is the rate‐limiting step during potassiation.

High-voltage aqueous asymmetric pseudocapacitors based on methyl blue-doped polyaniline hydrogels and the derived N/S-codoped carbon aerogels

The energy density of aqueous-electrolyte supercapacitors based on nanostructured carbon materials is usually limited by relatively narrow operating voltage window (about 1 V in acid aqueous electrolyte), due to the existence of overpotential. We report a novel N/S-codoped carbon aerogel (NS-CAG) derived from a methyl blue-doped polyaniline hydrogel (MB-PHG) with 3D interconnected supramolecular architecture through polymerization and carbonization. The obtained NS-CAG shows a high active nitrogen content along with simultaneous interlayer expansion, probably attributed to the MB-enabled supramolecular architecture of MB-PHG precursor, in favor of improving its pseudocapacitance and electrolyte ion diffusion. The assembled asymmetric pseudocapacitors based on the graphite fiber-supported NS-CAG and MB-PHG electrodes, can break through the overpotential barrier to an ultrahigh operating voltage window of 2.0 V in 1 M H2SO4, resulting in the excellent energy density of 59.7 Wh kg−1 at 1 kW kg−1. This high-energy asymmetric pseudocapacitor can open up an exciting route to extend the operating voltage window for aqueous-electrolyte energy storage.

Homo- and Heterosolvent Modifications of Hofmann-Type Flexible Two-Dimensional Layers for Colossal Interlayer Thermal Expansions.

Two-dimensional Hofmann-type coordination polymers of type Mn(H2O)2[Pd(CN)4]·xH2O (1·xH2O; x = 0, 1, and 4), Mn(H2O)(MeOH)[Pd(CN)4]·2MeOH (2·2MeOH), and Mn(MeOH)2[Pd(CN)4]·MeOH (3·MeOH) have been synthesized. The homosolvent-bound 1·4H2O, 1·H2O, and 3·MeOH polymers consist of undulating layer structures, whereas the structure of heterosolvent-bound 2·2MeOH consists of "Janus-like" flat layers in which water-bound and MeOH-bound-sides are present. 1·4H2O and 1·H2O exhibited anisotropic two-dimensional thermal expansions involving structural transformations of the undulating layers; one layer axis expands while the other contracts. 2·2MeOH exhibits anisotropic thermal expansion in which the flat layers shift sideways as the temperature is increased, with colossal interlayer expansion occurring (αc = +200 MK-1 over 140-180 K, αc = +165 MK-1 over 200-280 K). 3·MeOH also showed colossal interlayer expansion (αc = +216 MK-1) together with expansion of the undulating layers.