Graphene Oxide Laminates Research Articles

Effectively Sieving Alkali Metal Ions Using Functionalized Graphene Oxide Membranes by Exploiting Water-Repellent Interactions.

Sieving membranes capable of discerning different alkali metal ions are important for many technologies, such as energy, environment, and life science. Recently, two-dimensional (2D) materials have been extensively explored for the creation of sieving membranes with angstrom-scale channels. However, because of the same charge and similar hydrated sizes, mostly laminated membranes typically show low selectivity (<10). Herein, we report a facile and scalable method for functionalizing graphene oxide (GO) laminates by dually grafting cations and water-repellent dimethylsiloxane (DMDMS) molecules to achieve high selectivities of ∼50 and ∼20 toward the transport of Cs+/Li+ and K+/Li+ ion pairs, surpassing many of the state-of-the-art laminated membranes. The enhanced selectivity for alkali metal ions can be credited to a dual impact: (i) strong hydrophobic interactions between the incident cations' hydration shells and the water-repellent DMDMS; (ii) the efficient screening of electrostatic interactions that hamper selectivity.

Elucidating the role of double-confined effect in hollow MOFs/GO catalytic membrane for deep arsenic pollution treatment

The significance of addressing arsenic contamination is huge, given its widespread environmental impact and detrimental effects on human health. Herein, we developed a double-confined catalytic membrane capable of activating peroxymonosulfate (PMS) by integrating hollow Prussian blue analogues (H-PBA) with a unique void-confinement effect into graphene oxide (GO) laminates. This delicately designed H-PBA/GO membrane displayed 98.8 % p-arsanilic acid (p-ASA) removal with a 9.03 s retention time, surpassing most reported studies. Our experiments underscored that the dual-confined architecture not only drove mass transfer but also bolstered reactant concentration, thereby multiplying catalytic activities. Remarkably, this double-confinement conduced to a sustained dominance of surface-radicals (SO4−) and singlet oxygen (1O2), bolstering p-ASA degradation across a broad pH spectrum and numerous aqueous realms, inclusive of high salinity waters pertinent to desalination pre-treatment processes. Crucially, the H-PBA/GO membrane demonstrated over 90 % degradation of p-ASA and immobilized total As, unfaltering over 80 h of continuous operation. This signified an evolution in membrane technology, promising enhanced and steadfast performance. This innovation bore profound implications for devising double-confined efficacious and robust catalysts, poised to revolutionize advanced wastewater treatment, notably augmenting desalination systems by fortifying pre-treatment and safeguarding reverse osmosis membranes from organic and arsenic fouling.

Development of large-scale laminar-structure nanofiltration membranes for high dye rejection and enhanced robustness: Utilizing potassium ion-crosslinked graphene oxide and polyethyleneimine surface coating

Laminar graphene oxide (GO) membranes are at the forefront of groundbreaking research as a prospective advanced solution for nanofiltration. Both physical and computational experiments have showcased the exceptional efficacy of these GO membranes. However, scalability and robustness issues still remain significant hurdles for the practical implementation of GO membranes. In this study, to address these issues concurrently, we employed tape-casting of GO hydrogel induced by potassium ion crosslinking alongside polyethyleneimine crosslinking between the tape-casted laminar GO layers and the porous support layer. Through this approach, we successfully crafted a scalable laminar GO membrane encompassing an area of 900 cm², characterized by good uniformity. The GO membranes achieved excellent rejection efficiencies of 99.22 %, 99.42 %, and 99.27 % for methylene blue, methyl orange, and rhodamine B, respectively, with 0.77 LMH/bar of pure water permeability. Furthermore, the GO membranes demonstrated enhanced stability, validated by both long-term operation and testing under harsh conditions.

Laminated graphene oxide and hydrotalcite membranes via alternating spray-deposition with stable desalting performance

Laminated graphene oxide (GO) membrane has great potential for desalination, but achieving good stability in salt retention and water permeation is still a challenge. The “compact” sieving structure and the “loose” permeating structure of the GO membranes offer synergetic effects for high-performance desalination. Here, a composite desalination membrane involving two two-dimensional layered nanomaterials with opposite charges has been reported. The multi-layered GO (MLGO) and hydrotalcite (HT) were then alternated in a spray-coating on a PDA-modified substrate to construct multiple structures. Different assembly regions were identified by in-situ morphology monitoring, which showed that MLGO and HT were connected by electrostatic attractions. Also, the composite membrane showed high salt retention, permeability and long-term performance stability. The water flux of the composite membrane increased from 2.8 L m−2 h−1 bar−1 to 3.6–5.2 L m−2 h−1, which was due to the increases in the interlayer spacing distances and the introduction of new permeable spaces. After a 400 h continuous filtration test, the Na2SO4 retention remained stable. The water fluxes were in the range of 2.0–3.0 L m−2 h−1 bar−1, which corresponded to an increase by 42.9 %–114.3 % in comparison with the pure MLGO membrane. As compared with the MLGO membrane, molecular dynamics (MD) simulations revealed that more water molecules passed through the MLGO-HT membrane with a shorter pathway length and higher speed than MLGO membrane. The present study demonstrated the potential of a composite with 2D materials for desalination applications.

Distinct ion transport behavior between graphene oxide and UV-irradiated reduced graphene oxide membranes

Graphene oxide (GO) membranes are promising materials for achieving selective ion permeation in aqueous solutions. However, the swelling of GO laminates, caused by the affinity of water molecules for oxygen-containing groups (OCGs) on GO, significantly limits the practical prospects of GO membranes for selective ion transport and separation applications. Selectively removing OCGs from GO has been shown to decrease the interlayer distance between individual GO sheets, thereby improving the ability of laminate membranes to discriminate between different ions based on a size-exclusion mechanism. In this work, GO reduced through exposure to ultraviolet light (UV-rGO) is shown to display ion transport behavior that raises questions about size-exclusion as the dominant mechanism determining selective ion transport in GO membranes. Notably, smaller monovalent Li+ cations are found to permeate more slowly through UV-rGO membranes than larger divalent metal cations such as Ca2+ and Mg2+. This unexpected behavior results in a 3 – 4 fold improvement in the separation selectivity between these representative cations with UV-rGO compared to pristine GO membranes. Through a joint experimental and theoretical study, we identified the factors influencing selective ion transport through the nanochannels in UV-rGO membranes. We demonstrate that the selective removal of hydroxyl (–OH) groups from the basal planes of GO enhances the interactions of metal cations with functional groups located at the edges of GO, thereby resulting in a lower ratio of free Li+ in solution, rather than stationary Li+ adsorbed onto the surface GO, compared to Ca2+ cations. Based on these results, we propose a separation mechanism analogous to chromatography, which emphasizes the crucial role of different OCGs on GO surfaces in controlling selective ion transport through GO membranes.

Comparative Retention Analysis of Intercalated Cations Inside the Interlayer Gallery of Lamellar and Nonlamellar Graphene Oxide Membranes in Reverse Osmosis Process: A Molecular Dynamics Study.

Over the past decade, multilayered graphene oxide (GO) membranes have emerged as promising candidates for desalination applications. Despite their potential, a comprehensive understanding of separation mechanisms remains elusive due to the intricate morphology and structural arrangement of interlayer galleries. Moreover, a critical concern of multilayered GO membranes is their susceptibility to swelling within aqueous environments, which hinders their practical implementation. Therefore, this study introduces cation intercalation within GO laminates to elucidate the underlying factors governing swelling behavior and subsequently mitigate it. Moreover, this study performed nonequilibrium molecular dynamics simulations on the cation (Mg2+ or K+)-intercalated lamellar and nonlamellar GO membranes to understand the effect of the arrangement of GO sheets on the retention time of intercalated cations within GO layers, water permeance, and salt rejection mechanism in the reverse osmosis process using cation-intercalated GO membranes. Our results highlight that lamellar GO membranes exhibit higher water permeance, attributed to their well-defined interlayer gallery structure. On the other hand, nonlamellar GO membranes display superior salt rejection due to their complex interlayer gallery structure that impedes salt permeation. Moreover, the structural complexity of nonlamellar GO membranes contributes to greater stability by retention of the more intercalated cations for a longer time within the layers. Furthermore, it is observed that a higher percentage of Mg2+ cations remained inside the GO laminates as compared to K+ cations, hence resulting in the greater stability of the Mg2+-intercalated GO membrane in the aqueous environment.

Tunable Release of Ions from Graphene Oxide Laminates for Sustained Antibacterial Activity in a Biomimetic Environment.

Silver has long been recognized for its potent antimicrobial properties, but achieving a slow and longer-term delivery of silver ions presents significant challenges. Previous efforts to control silver ion dosages have struggled to sustain release for extended periods in biomimetic environments, especially in the presence of complex proteins.This challenge is underscored by the absence of technology for sustaining antimicrobial activity, especially in the context of orthopedic implants where long-term efficacy, extending beyond 7days, is essential. In this study, the tunable, slow, and longer-term release of silver ions from the two-dimensional (2D) nanocapillaries of graphene oxide (GO) laminates incorporated with silver ions (Ag-GO) for antimicrobial applications are successfully demonstrated. To closely mimic a physiologically relevant serum-based environment, a novel in vitro study model using 100% fetal bovine serum (FBS) is introduced as the test medium for microbiology, biocompatibility, and bioactivity studies. To emulate fluid circulation in a physiological environment, the in vitro studies are challenged with serum exchange protocols on different days. The findings show that the Ag-GO coating can sustainably release silver ions at a minimum dosage of 10µgcm-2day-1, providing an effective and sustained antimicrobial barrier for over ten days.

Nanochannel Stability of Chemically Converted Graphene Oxide Membranes.

Chemically converted graphene oxide laminate membranes, which exhibit stable interlayered nanochannels in aqueous environments, are receiving increasing attention owing to their potential for selective water and ion permeation. However, how the molecular properties of conversion agents influence the stabilization of nanochannels and how effectively nanochannels are stabilized have rarely been studied. In this study, mono-, di-, and tri-saccharide molecules of glucose (Glu), maltose (Glu2), and maltotriose (Glu3) are utilized, respectively, to chemically modify graphene oxide (GO). The aim is to create nanochannels with different levels of stability and investigate how these functional conversion agents affect the separation performance. The effects of the property differences between different conversion agents on nanochannel stabilization are demonstrated. An agent with efficient chemical reduction of GO and limited intercalation in the resulting nanochannel ensures satisfactory nanochannel stability during desalination. The stabilized membrane nanochannel exhibits a permeance of 0.69 L m-2 h-1 bar-1 and excellent Na2SO4 rejection of 96.42%. Furthermore, this optimized membrane nanochannel demonstrates enhanced stability under varying external conditions compared to the original GO. This study provides useful information for the design of chemical conversion agents for GO nanochannel stabilization and the development of nanochannel membranes for precise separation.

Ion-retention properties of graphene oxide/zinc oxide nanocomposite membranes at various pH and temperature conditions

Laminar graphene oxide (GO) is a promising candidate material for next-generation highly water-permeable membranes. Despite extensive research, there is little information known concerning GO's ion-sieving properties at high acidic/basic pH and temperatures. In this study, the ion-blockage properties of the pristine GO and GO/zinc oxide (ZnO) nanocomposite membranes were tested using a non-pressure-driven filtration setup over a wide range of pH and temperatures. The ZnO nanoparticles within the composite membranes were synthesized via the room-temperature oxidation of zinc acetate and zinc acrylate precursors and were uniformly distributed across the composite membrane. It is observed that partially replacing the zinc acetate precursor with zinc acrylate improves the blockage performance of the composite membranes under extreme basic conditions by 42%. Moreover, photocatalytically-reduced composite membranes blocked copper sulfate ions 28% more than as-prepared composite membranes. Further, it was discovered that the composition of the membrane plays a vital role in its ion blockage performance at higher temperatures.

High-efficiency water-transport channels using the synergistic effect of superhydrophilic PA layer and robust BU cross-linked GO laminates

Graphene oxide (GO) membranes show immense promise in nanofiltration separation for water purification and recycling of water resources. However, pristine GO membranes often suffer from insufficient membrane stability due to swelling and low water permeance under high operation pressure, which severely limits the real-world utilization of GO membranes. Herein, a strategy involving surface modification of GO membrane with superhydrophilic polyamide (PA) layer combined with cross-linking with biurea (BU) amine, is proposed to fabricate highly permeable and robust GO membranes for dye removal from aqueous solution. The PA layer is prepared onto BU cross-linked GO membrane by in-situ interfacial polymerization, which results in superhydrophilic and negative-charged membrane surface. Moreover, the low reactivity of 2,5-diaminobenzenesulfonic acid (DBS) monomer contributes to low cross-linking degree and loose network of PA layer. The BU cross-linked GO laminates possess multi-level interlayer spacings and sufficient covalent interaction between GO interlayer due to crosslinking with BU, which offer large and robust transport channels for water molecules. PA@BU/GO hybrid membrane shows the optimum pure water permeability of 140.2 L·m−2·h−1·bar−1, with water permeance and TB rejection rate of 67.4 L·m−2·h−1·bar−1 and 99.9 %, respectively. Moreover, the membrane exhibits impressive dye/salt selectivity (the dye/NaCl separation factor is up to 873), long-term operation stability and good anti-fouling property, which makes it a potential candidate for the fractionation of dye/salts in textile wastewater. This work provides a promising idea for the development of high-performance 2D membranes with high-efficiency water transport channels using the synergistic effect of superhydrophilic PA Layer and robust BU cross-linked GO laminates.

Graphene oxide composited with different size of organic molecules for hydrogen isotopic water separation in membrane distillation

Developing an efficient light water/tritiated water (H2O/HTO) separation process to meet environmental regulations is important in the nuclear energy field. The membrane distillation processes for the separation of H2O/D2O (deuteriated water), which is usually served as the laboratory model process for H2O/HTO separation, showed good separation performance with graphene oxide (GO)-based membranes. Here, the approach to enhance the H2O/D2O separation performance was explored through regulating interlayer spacing and physicochemical properties of membranes, for which two types of GO membranes were prepared and applied in air-gap membrane distillation: (i) small molecules of urea (UR) or ethanediamine (EDA) were cross-linked with GO platelets to obtain GO-framework (GOF) membranes designated as GO-UR or GO-EDA with varied interlayer spacing. The GO-EDA membrane with a permeation flux of 0.95 L·m−2·h−1 gave higher separation performance than the pristine GO membrane; (ii) macromolecules of hydrophilic polyvinyl alcohol (PVA) or hydrophobic polymethyl methacrylate (PMMA) were intercalated into GO laminates to adjust interlayer spacing and physicochemical properties of membranes. The resultant GO-PVA membrane exhibited a higher permeation flux of 0.94 L·m−2·h−1 and similar separation factor compared with the pristine GO membrane. Moreover, long-term process stability of H2O/D2O separation in membrane distillation was demonstrated using GO-EDA membrane for a 28-h process. Therefore, the results demonstrated that regulating interlayer spacing and physicochemical properties of membranes can provide a facile route to improve performance of GO-based membrane distillation processes for the separation of H2O/D2O, which may be applied to H2O/HTO separation process needed for the treatment of tritiated water in the nuclear energy field.

Tunable Sieving of Ions Using Graphene Oxide: Swelling Peculiarities in Free-Standing and Confined States.

The paper describes a comparative study of swelling processes in free-standing graphene oxide (GO) membranes and GO laminates encapsulated with epoxy glue. For free-standing graphene oxide membranes, a huge variation in d-spacing in the range of 8-12 Å depending on the ambient humidity and from 12 to >30 Å depending on the electrolyte type and its concentration was revealed using direct in situ and in operando XRD studies. Limited swelling at various humidity levels as well as in electrolyte solution with low constriction/expansion of epoxy-encapsulated GO is counterposed to that of free-standing graphene oxides. The swelling suppression was explained by both physical constriction and the intercalation of amines into GO laminates, which was proved by local EDX studies. This results in ion diffusivity variation for over 2 orders of magnitude in free-standing and constrained graphene oxide membranes and provides factual evidence for tunable sieving of ions with confined graphene oxides.

Size-dependent water transport in laminar graphene oxide membranes: An interplay between interlayer spacing versus tortuosity of transport pathway

Graphene oxide membranes (GOMs), consisting of graphene oxide (GO) laminar microstructures, offer great potential as nanofiltration membranes due to their unique laminar nanochannelled galleries created between the stacked GO flakes. Recently, GOMs made from smaller GO flakes (S-GOMs) were favored for the reason that the less tortuous transport pathways could render better water permeability. Here, we found that this may not necessarily be true. We designed experiments, which suggested that the interlayer spacing between GO flakes may be a more important factor affecting the water permeability than the tortuosity of the water pathway, especially when the two-dimensional nanochannels were smaller than expected under a pressurized filtration setting. Notably, our results showed that as the GO flakes were fragmented into smaller pieces by high-power probe sonication, they underwent a thermal reduction that decreased the size of the interlayer spacing. Coupled with a less wrinkled microstructure that caused tighter compaction under a 3-bar transmembrane pressure, the overall water transport through the S-GOM was reduced despite a less tortuous pathway that was 2.5 times shorter based on theoretical calculation. This led to S-GOM showing 3.3 times lower water permeability than that of GOM made from large GO flakes. On the whole, our results unveil the interplay between the two most important parameters governing the water permeability of GOMs, which will help researchers with more instructional support when developing better performing GOMs for nanofiltration application.

Confined intercalating sulfonated graphene quantum dots into GO laminates for fast alkali recovery

Graphene oxide (GO) membranes with uniform sub-nanometer interlayer channels have shown great promise in the ion sieving field. However, the lack of ion-transporting sites on the GO nanosheets usually leads to inferior ion permeation and selectivity. Although the intercalation of molecules with ionic groups into GO laminates is easily achieved to incorporate ion exchange sites, this approach inevitably enlarges the interlayer spacing, reducing the ionic sieving capacity. Thus, current methods are limited in breaking the permeation and selectivity “trade-off”. Herein, we report a confined intercalation strategy to inject ample sulfonic acid groups into GO laminates using sulfonated graphene quantum dots (SGQD) as intercalators. SGQD with abundant ion exchange sites assembles on the sp2 domains of GO via π-π interactions and confers the GO membranes with continuous ion conduction pathways. Meanwhile, benefiting from the ultra-small size SGQD as well as its sheet morphology, it can well accommodate in the GO laminates. This strategy fulfills the incorporation of ionic sites without expanding channel width and destructing the two-dimensional (2D) regularity for GO laminates, resulting in simultaneous improvements in ion permeability and selectivity. Correspondingly, the resulting membranes show synergistically improving OH- dialysis coefficients of 3.5 × 10−3-8.2 × 10−3 m h−1 and OH-/WO42- separation factors of 56–116 compared with the GO membrane (0.9 × 10−3 m h−1 and 8.4) for separating simulated NaOH/Na2WO4 alkaline effluents. We believe the confined intercalating regulation can act as a versatile and fine way to modify 2D membranes for intensifying ion separation.

Electrodepositing MOFs into laminated graphene oxide membrane for CO2 capture

Due to increased CO2 emissions from the combustion of fossil fuels, considerable efforts have been made in CO2 capture. The preparation of a membrane with higher mechanical qualities and large CO2 adsorption capacity, however, remains the main obstacle. Here, using an in-situ anodic electrodeposition approach, we grow HKUST-1 MOFs into the graphene oxide (GO) two-dimensional (2D) nanochannels. A three-stage mechanism for the confined growth of MOFs during electrodeposition has been proposed. Through the inventive layer-by-layer confinement structural growth, MOFs@GO composite membranes with hierarchical pore structure were prepared. An extremely high CO2 adsorption capacity of 194.1 cm3/g and CO2/N2 adsorption ideal selectivity of 276.5 were achieved at 273 K and atmospheric pressure because of the synergistic effect of nanoconfined HKUST-1 and GO. The composite membrane prepared by electrodeposition method can expose more metal active sites in the presence of hierarchical porous structures, thus enhancing the CO2 adsorption capacity. In addition, incorporating the HKUST-1 into GO nanochannels demonstrates 50.6% and 138.13% improvement in hardness and elastic modulus over pristine GO membrane, respectively. This provides a promising method for developing high-performance CO2 capture membrane system under normal temperature and pressure conditions. It is also generally applicable for growing other MOFs@GO composite membranes, such as Cu-BDC@GO and Cu-BDC-NH2@GO membranes, respectively, and more suitable for large-scale industrial production.

Side-Chain-Dependent Functional Intercalations in Graphene Oxide Membranes for Selective Water and Ion Transport.

Subnanometer interlayer space in graphene oxide (GO) laminates is desirable for use as permselective membrane nanochannels. Although the facile modification of the local structure of GO enables various nanochannel functionalizations, precisely controlling nanochannel space is still a challenge, and the roles of confined nanochannel chemistry in selective water/ion separation have not been clearly defined. In this study, macrocyclic molecules with consistent basal plane but varying side groups were used to conjunct with GO for modified nanochannels in laminates. We demonstrated the side-group dependence of both the angstrom-precision tunability for channel free space and the energy barrier setting for ion transport, which challenges the permeability-selectivity trade-off with a slightly decreased permeance from 1.1 to 0.9 L m-2 h-1 bar-1 but an increased salt rejection from 85% to 95%. This study provides insights into the functional-group-dependent intercalation modifications of GO laminates for understanding laminate structural control and nanochannel design.

A Combined Gas and Water Permeances Method for Revealing the Deposition Morphology of GO Grafting on Ceramic Membranes.

The adhesion enhancement of a graphene oxide (GO) layer on porous ceramic substrates is a crucial step towards developing a high-performance membrane for many applications. In this work, we have achieved the chemical anchoring of GO layers on custom-made macroporous disks, fabricated in the lab by pressing α-Al2O3 powder. To this end, three different linkers, polydopamine (PDA), 3-Glycidoxypropyltrimethoxysilane (GPTMS) and (3-Aminopropyl) triethoxysilane (APTMS), were elaborated for their capacity to tightly bind the GO laminate on the ceramic membrane surface. The same procedure was replicated on cylindrical porous commercial ZrO2 substrates because of their potentiality for applications on a large scale. The gas permeance properties of the membranes were studied using helium at 25 °C as a probe molecule and further scrutinized in conjunction with water permeance results. Measurements with helium at 25 °C were chosen to avoid gas adsorption and surface diffusion mechanisms. This approach allowed us to draw conclusions on the deposition morphology of the GO sheets on the ceramic support, the mode of chemical bonding with the linker and the stability of the deposited GO laminate. Specifically, considering that He permeance is mostly affected by the pore structural characteristics, an estimation was initially made of the relative change in the pore size of the developed membranes compared to the bare substrate. This was achieved by interpreting the results via the Knudsen equation, which describes the gas permeance as being analogous to the third power of the pore radius. Subsequently, the calculated relative change in the pore size was inserted into the Hagen-Poiseuille equation to predict the respective water permeance ratio of the GO membranes to the bare substrate. The reason that the experimental water permeance values may deviate from the predicted ones is related to the different surface chemistry, i.e., the hydrophilicity or hydrophobicity that the composite membranes acquire after the chemical modification. Various characterization techniques were applied to study the morphological and physicochemical properties of the materials, like FESEM, XRD, DLS and Contact Angle.

Constructing low-friction mass transfer channel in laminar graphene oxide membrane for efficient molecular separation with enhanced permeability

In recent years, graphene oxide (GO) has attracted increasing interest in fabricating next-generation separation membranes. The perm-selectivity of laminar GO membrane is generally determined by their interlayer nanochannel structure. Herein, we used a new molecule called 5, 5′-diamine-2, 2′-biphenol (BIPOL-NH2) as the intercalator of laminar GO-based membrane to construct low-friction interlayer mass transfer channels. The aromatic BIPOL-NH2 molecules act as hydrophobic side walls of the mass transfer channels between adjacent GO nanosheets, reducing the interaction between water molecules and channel structure, thereby enhancing water permeability of GO membranes. This was confirmed by the further molecular dynamics simulation. Compared with pristine GO membrane, the BIPOL-GO membrane showed a water permeability increase by a factor of about 3 (up to 72.4 L m-2h−1 bar−1), which was consistent with our simulation results. Also, it represented excellent dye/salt separation performance (the selectivity of NaCl/CR is more than 117.2) and good structural stability. Overall, our work provides a novel and efficient approach to modify GO-based membranes for enhanced permeability.

Manipulating gas transport channels in graphene oxide membrane with swift heavy ion irradiation

Graphene oxide (GO), a prominent two-dimensional (2D) material, has established itself as an ideal building block for separation membranes, owing to its unique laminar structures and tunable physicochemical properties. While the ultrathin nature of GO membranes is anticipated to minimize transport resistance, the convoluted mass transport pathways within laminar GO membranes generally yield moderate permeance. Here, for the first time, we explored using swift heavy ion irradiation to incorporate through transport channels in GO membranes with highly enhanced gas permeation properties. After 129Xe irradiation, characteristic ion tracks were discerned within the GO membrane cross-section. The irradiation process created disorder regions and nanopores within the laminates, and meanwhile facilitated cross-linking between the oxygen-containing groups of GO, thereby reducing the interlayer spacing and enhancing molecular sieving capabilities. The irradiated GO membranes surpassed the H2/CO2 performance upper-bound, with H2 permeance exhibiting a remarkable three-order-of-magnitude increase. This work demonstrates the feasibility of applying heavy ion irradiation to create and tune interlayer channels based on physical and chemical interactions.

Confined and mediated intercalation of nanoparticles in graphene oxide membrane to fine-tune desalination performance

Multilayered graphene oxide (GO) membranes with interlayered sub-nanometer channels have attracted considerable interest for selective water and ion transport. However, the tortuous transport pathways and water-swelling characteristics of GO laminates hinder the desalination performance of such membranes. Modifying the interlayer through nanoparticle intercalation is one of the most prevalently employed methods of enlarging the nanochannels for rapid transport. However, this generally results in significantly reduced separation precision. In this study, we develop a confined interlayer with mediated nanoparticle intercalation to precisely modulate GO membranes. Enhanced water transport and high ion retardation were simultaneously achieved. We investigated the roles of confinement and mediation in the intercalation modification of GO laminates and highlighted their indispensability in realizing an efficient and effective desalination process. This strategy may also be applicable to the fine-structure control of other two-dimensional laminates.