Aqueous Ion Trapping and Transport in Graphene-Embedded 18-Crown-6 Ether Pores

We use all-atom molecular dynamics simulations informed by density functional theory calculations to investigate aqueous ion transport across sub-nanoporous monolayer molybdenum disulfide (MoS 2 ) membranes subject to varying tensile strains. Driven by a transmembrane electric field, highly mechanosensitive permeation of both anions and cations is demonstrated in membranes featuring certain pore structures. For pores that are permeable when unstrained, we demonstrate ion current modulation by a factor of over 20 in the tensile strain range of 0 -4%. For unstrained pores that are impermeable, a clear strain-induced onset of permeability is demonstrated within the same range of strains. The underlying mechanism is shown to be a strain-induced reduction of the generally repulsive ion-pore interactions resulting from the ions' short-range interactions with the atoms in the pore interior and desolvation effects. The mechanosensitive pores considered in this work gain their electrostatic properties from the pore geometries and in principle do not require additional chemical functionalization. Here we propose the possibility of a new class of mechanosensitive nanoporous materials with permeation properties determined by the targeted engineering of vacancy defects.

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“…A more detailed description of the methodology used to obtain the PMFs in Fig. 3, as well as in our earlier works, 5,25 is presented in Ref. 24.…”

Section: Resultsmentioning

confidence: 99%

Mechanosensitive Ion Permeation across Subnanoporous MoS₂ Monolayers

2019

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“…Smolyanitsky et al addressed this point by theoretically calculating that 18‐Crown‐6 pores embedded in graphene could be used for selectively trapping cation within the pore and sieving cations. [ 31 ] They also simulated the stability of crown ether pore–cation complexes; however, it is challenging to materialize crown ether pores embedded in graphene. In addition, one of the main problems in taking advantage of 18‐Crown‐6 molecules lies in the fact that they can be easily dissolved away in water during permeation test due to its hydrophilic property.…”

Section: Introductionmentioning

confidence: 99%

Design of Sub‐Nanochannels between Graphene Oxide Sheets via Crown Ether Intercalation to Selectively Regulate Cation Permeation

Bang

Bahamón²,

Vega³

et al. 2020

Adv Materials Inter

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development and human activities, giving rise to the need for a method to obtain clean water resources. Membrane filtration, one of the processes to separate contaminants and salts from water, has attracted much attention as a way to secure clean water in an energy efficient manner. [2,3] As a result, various kinds of membrane materials, especially polymers, [4] have been widely studied for desalination and water purification. [5][6][7][8] However, the availability of polymer membranes in a large-scale process is unsuitable due to a poor mechanical and chemical stability, along with fouling issues. [9] It is crucial to find other potential material candidates to tackle these problems.Graphene derivatives are emerging candidates for efficient water treatment membranes, attributed to their unique nanochannel network [10] as well as the robust chemical and mechanical stability; [11][12][13] these chemical and physical stability are originated from their graphitic structure. [14,15] In particular, graphene oxide (GO) is regarded as a versatile platform for separating ions or contaminants due to its tunability and scalability. Furthermore, the distinctive nanochannel of the GO membranes formed by vacuum-filtration allows the GO membrane not only to block unwanted solutes, but also to achieve a high water permeability. However, it is extremely difficult to maintain the rejection performance of the GO membrane in a long term since the oxygen functional groups interact with water molecule via hydrogen bonding, resulting in membrane swelling in aqueous solution. For instance, Zheng et al. found that the d-spacing of a GO membrane significantly increased in an aqueous solution compared to its dry state-swelling up to 7 nm at equilibrium-while limiting the mobility of water molecules. [16] Additionally, to explain and predict the separation performance of multilayered GO membrane, several research groups have studied the water flow through such graphene-based layers and the influence of the degree of oxidation using molecular simulations. [17][18][19][20][21][22][23] They observed a swelling effect depending on the oxygen functional groups and an irregular structure of water molecules when passing through GO nanochannels.In order to effectively suppress the permeation of ions through the membrane for desalination, it is necessary not only to design the GO nanopathway more precisely, but also to maintain the fine nanochannels over a long period of time.Graphene-based membranes are a promising candidate for separating pollutants and ions. In particular, graphene oxide (GO) membranes are widely studied due to their unique nanochannels. The characteristic nanochannels of GO membranes can be manipulated via intercalation of cations, inhibiting the transport of other ions in the diffusion process. To maintain the tailored nanochannel during a pressure-assisted filtration procedure, it is essential to retain such inserted cations. Here, dibenzo-18-Crown-6 molecules (DB18C6) tightly binding to potassium ions are intercalated into G...

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“…[27][28][29][30] Note that due to the preferential adsorption by defects, the Al 2 O 3 content in the hybrid formed is very low (5.3 wt%), but the nanoclusters effectively prevent direct contact between the defects and the electrolyte solution. The 3D structure of a PGM assembled from rGO avoids the aggregation of rGO nanosheets (NSs) and ensures their high surface utilization.…”

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confidence: 99%

Deactivating Defects in Graphenes with Al₂O₃ Nanoclusters to Produce Long‐Life and High‐Rate Sodium‐Ion Batteries

Lin

Zhang

Kong

et al. 2018

Advanced Energy Materials

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LIBs), delivers very limited reversible capacity in SIBs due to its inability to form stable low-stage graphite intercalation compounds (GICs). [4,5] Thus, most research has turned to nongraphitic carbons including nanocarbons and hard carbons, [6][7][8][9][10] whose capacities are significantly higher than graphite. It has been found that the structure could be well controlled to realize the high efficiency and reversibility. Our group has reported that the commercial carbon molecular sieves with abundant ultrasmall (0.3-0.5 nm) pores can achieve high efficiency and reversible capacity. [11] Intensive researches have also revealed that the nongraphitic carbons with low specific surface areas (SSA) exhibit a high electrochemical stability. [12][13][14][15][16] However, these carbons show limited rate capability and relatively low capacity. Thus, it is desired to improve the SSA to enhance the rate performance and capacity. Unfortunately, nongraphitic carbons with large SSA and a large number of defects typically exhibit an extremely low initial Coulombic efficiency (ICE) and unsatisfactory cyclic stability because of uncontrollable electrolyte decomposition and ineffective formation of a solid electrolyte interphase (SEI). In a previous report, we used reduced graphene oxide (rGO) as a model anode and found that an ether-based electrolyte can greatly suppress the Carbon materials are the most promising anodes for sodium-ion batteries (SIBs), but low initial Coulombic efficiency (ICE) and poor cyclic stability hinder their practical use. It is shown herein, that an effective but simple remedy for these problems can be achieved by deactivating defects in the carbon with Al 2 O 3 nanocluster coverage. A 3D porous graphene monolith (PGM) is used as the model material and Al 2 O 3 nanoclusters around 1 nm are grown on the defects of graphene. It is shown that these Al 2 O 3 nanoclusters suppress the decomposition of conductive sodium salt in the electrolyte, resulting in the formation of a thin and homogenous solid electrolyte interphase (SEI). In addition, Al 2 O 3 nanoclusters appear to reduce the detrimental etching of the SEI by hydrogen fluoride (HF) and improve its stability. Therefore, after the introduction of Al 2 O 3 nanoclusters, the ICE, cyclic stability, and rate capability of the PGM are greatly improved. A higher ICE (70.2%) and capacity retention (82.9% after 500 cycles at 0.5 A g −1 ) than those of normally reported for large surface area carbons are achieved. This work indicates a new way to deactivate defects and modify the SEI of carbon materials, and hopefully accelerate the commercialization of carbon materials as anode materials for SIBs.

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Aqueous Ion Trapping and Transport in Graphene-Embedded 18-Crown-6 Ether Pores

Cited by 59 publications

References 39 publications

Mechanosensitive Ion Permeation across Subnanoporous MoS₂ Monolayers

Mechanosensitive Ion Permeation across Subnanoporous MoS₂ Monolayers

Design of Sub‐Nanochannels between Graphene Oxide Sheets via Crown Ether Intercalation to Selectively Regulate Cation Permeation

Deactivating Defects in Graphenes with Al₂O₃ Nanoclusters to Produce Long‐Life and High‐Rate Sodium‐Ion Batteries

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Aqueous Ion Trapping and Transport in Graphene-Embedded 18-Crown-6 Ether Pores

Cited by 59 publications

References 39 publications

Mechanosensitive Ion Permeation across Subnanoporous MoS2 Monolayers

Mechanosensitive Ion Permeation across Subnanoporous MoS2 Monolayers

Design of Sub‐Nanochannels between Graphene Oxide Sheets via Crown Ether Intercalation to Selectively Regulate Cation Permeation

Deactivating Defects in Graphenes with Al2O3 Nanoclusters to Produce Long‐Life and High‐Rate Sodium‐Ion Batteries

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Product

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Mechanosensitive Ion Permeation across Subnanoporous MoS₂ Monolayers

Mechanosensitive Ion Permeation across Subnanoporous MoS₂ Monolayers

Deactivating Defects in Graphenes with Al₂O₃ Nanoclusters to Produce Long‐Life and High‐Rate Sodium‐Ion Batteries