Uniform Nanopores Research Articles

Nanoporous Aramid Nanofiber Separators with High Modulus and Thermal Stability for Safe Lithium-Ion Batteries.

Developing high-safety separators is a promising strategy to prevent thermal runaway in lithium-ion batteries (LIBs), which stems from the low melting temperatures and inadequate modulus of commercial polyolefin separators. However, achieving high modulus and thermal stability, along with uniform nanopores in these separators, poses significant challenges. Herein, the study presents ultrathin nanoporous aramid nanofiber (ANF) separators with high modulus and excellent thermal stability, enhancing the safety of LIBs. These separators are produced using a microfluidic-based continuous printing strategy, where the flow thickness can be meticulously controlled at the micrometer scale. This method allows for the continuous fabrication of nanoporous ANF separators with thicknesses ranging from 1.6 ± 0.1µm to 2.7 ± 0.1µm. Thanks to the double-side solvent diffusion, the separators exhibit controllably uniform pore sizes with a narrow distribution, spanning from 40 ± 5nm to 105 ± 9nm, and a high modulus of 3.3 ± 0.5GPa. These nanoporous ANF separators effectively inhibit lithium dendrite formation, resulting in a high-capacity retention rate for the LIBs (80% after 240 cycles). Most notably, their robust structural and mechanical stability at elevated temperatures significantly enhances LIB safety under transient thermal abuse conditions, thus addressing critical safety concerns associated with LIBs.

Prolonging rechargeable aluminum batteries life with flexible ceramic separator

Rechargeable aluminum batteries (RABs) are attracting significant attention for their high theoretical capacity and abundant reserves. However, the poor mechanical performance of glass fiber (GF) separators and the formation of Al dendrite severely hinder the practical cycle life of these batteries. Herein, a flexible ceramic separator was developed with simple coating technique, effectively improving the cycling stability of RABs. Compared with the commercial GF separator, this flexible ceramic separator has less thickness and superior electrolyte wettability, resulting in improved interfacial compatibility and minimized interfacial resistance. Moreover, its exceptional flexibility and toughness (stress of 39.34 MPa) coupled with uniform nanopore structure, which can effectively resist the penetration of dendrites. As expected, this ceramic flexible separator facilitates stable cycling of the symmetric battery for over 1762 h at 2 mA/cm2 and 2 mAh/cm2. It also permits the pouch Al//flake graphite full battery to achieve a coulombic efficiency of up to 90% even after 115 cycles. Apparently, this work developed the simple separator manufacturing strategy that provides an effective method to improve the cycling stability of RABs and extends the application to other types of batteries.

Self-extinguishing polyimide sandwiched separators for high-safety and fast-charging lithium metal batteries

Developing fast-charging lithium metal battery (LMB) with high specific capacity arouses enormous attentions. Unfortunately, during the operation of fast-charging LMB, substantial amount of Joule heat generated within battery often induces inhomogeneous heat accumulation that concomitantly deteriorates the lithium dendrite growth issues, resulting in rapid capacity fading and potentially fatal thermal runaway. It is critically essential to develop advanced separator that possesses high ionic conductivity, effective dendrite inhibition and self-extinguishing property for fast-charging LMB with high-safety. Here, we report a facile approach to fabricate polyimide composite separator (denoted as PIFAP), where the polyimide fiber (PIF) membrane is sandwiched by aerogel layers of polyimide/ammonium polyphosphate composite. Notably, compared with PIF, the PIFAP features significant enhancement in flame retardance, electrolyte affinity, electrolyte adsorption and ionic conductivity. Moreover, beneficiating from the aerogel layers with uniform nanopores of ∼100 nm, the optimized PIFAP separator can enable homogeneous lithium deposition, achieving a dendrite-free lithium deposition on the surface of anode for over 1600 h, superior to the PIF and Celgard separators. The resulting “LiFePO4/PIFAP/Li” cell can exhibit a remarkably high cycling stability with 99.1 % of capacity retention after long-term cycling at a current density of 10 C.

Tailoring separation performance of nanofiltration membranes by construction of Tin(II)-α-diimine coordination bonds in polyimides

Polyimide nanofiltration (NF) membranes with customizable chemical structures and excellent overall performance have attracted great interest in desalination and wastewater treatment. This work introduced novel Tin(II)-α-diimine coordination interactions to tailor the separation performance of polyimide NF membranes. Microstructural analysis confirmed the successful construction of coordination sites between Tin(II) and the diimine moieties. As expected, the resulting coordinated NF membranes exhibited uniform nanopores and reduced absolute negative charges on their surfaces, facilitating outstanding NF separation. The optimal coordinated polyimide NF membranes exhibited a high rejection rate of over 98 % for methylene blue (MB) and a low rejection rate of less than 2 % for NaCl and Na2SO4, demonstrating significant potential for application in dye desalination. Additionally, the obtained NF membranes demonstrate better long-term separation stability. As a preliminary study, this work provides a new strategy to modulate the microstructure and surface electric charge of NF membranes, potentially leading to greater application potential in dye desalination, seawater desalination, etc.

Surfactant-assisted synthesis of NiCo alloy with specific nanopore architecture as a bifunctional electrocatalyst for rechargeable zinc-air batteries

Designing the effective active sites and reaction areas of catalytic materials is important for the development of bifunctional electrocatalysts for zinc-air batteries (ZABs). In this paper, a catalyst with a uniform nanopore structure (noted as NiCo-PS) was one-pot synthesized by using transition metals nickel and cobalt as catalytic active components, sucrose as a carbon source, and triblock copolymers as a soft template. The N2 absorption and desorption isotherms curves show that the pore size distribution of NiCo-PS modified by surfactant is mainly in 3.6 nm range. NiCo-PS exhibits exceptional bifunctional electrocatalysis due to its effective triple-phase reaction interface from its mesoporous structure, with a positive half-wave potential of 0.758 V for ORR and a low overpotential of 390 mV at 10 mA ⋅ [Formula: see text] for OER. Furthermore, the rechargeable ZABs with the NiCo-PS catalyst exhibit a high open-circuit voltage of 1.31 V, a significant peak power density of 105 mA ⋅ [Formula: see text] at 0.56 V, and good stability throughout 270 h testing. This result offers valuable insights for designing catalysts that enhance the active region of the reaction within the cathodes of ZABs and hold significant promise for practical applications.

Characterization of Nanoporous Poly(Lactic Acid) Microfibers Using a Simplified Centrifugal Spinning Method

In recent years, great attention has been paid to the development of porous materials with excellent reactivity and absorbency. The poly(lactic acid) (PLA) microfibers with uniform nanopores were successfully prepared by rotary centrifugal spinning using PLA/chloroform solution. Previous research showed that PLA microfibers have extremely high oil absorbing capacity. In this study, the changes in fiber diameter and nanopore diameter of nanoporous PLA microfibers under different fabrication conditions and the adsorption capacity of Prussian blue nanoparticles were systematically evaluated. The results showed that the fiber diameter increased with increasing PLA/chloroform solution concentration. Furthermore, it was found that the amount of adsorbed Prussian blue nanoparticles increased with the increase in fiber diameter. Prussian blue nanoparticles are known to adsorb radioactive materials such as cesium, and are expected to be applied to the recovery of cesium diffused in the atmosphere and ocean.

Nano‐Confined Electrolyte for Sustainable Sodium‐Ion Batteries

AbstractSodium‐ion batteries (SIBs) are considered as a promising candidate for large‐scale electrochemical energy storage devices due to their low cost, abundant upstream resources, and compatible manufacturing processes with lithium‐ion batteries. However, the highly active free solvent molecules in the liquid electrolyte trigger continuous interfacial side reactions between electrodes and electrolyte, which degrades the cycling performance of SIBs. Herein, a Cu‐based metal‐organic framework (MOF) with a uniform nanoporous channel of 1.1 nm is exploited to confine the electrolyte. Benefiting from the highly‐aggregated solvation configuration, the MOF‐confined electrolyte possesses superior chemical/electrochemical and thermal stability, which guarantees its interface compatibility and flame retardancy. As a result, the batteries with the nano‐confined electrolyte and Na3V2(PO4)3 cathode show an ultra‐long lifetime of 3000 cycles with 93% capacity retention and decent high‐temperature performance (600 cycles with 90% capacity retention). This work presents a viable method for fabricating sustainable SIBs and also provides guidance for solving the side reactions between electrolytes and electrodes in electrochemical energy storage systems.

Superspreading-Based Fabrication of Thermostable Nanoporous Polyimide Membranes for High Safety Separators of Lithium-Ion Batteries.

The development of thermally stable separators is a promising approach to address the safety issues of lithium-ion batteries (LIBs) owing to the serious shrinkage of commercial polyolefin separators at elevated temperatures. However, achieving controlled nanopores with a uniform size distribution in thermostable polymeric separators and high electrochemical performance is still a great challenge. In this study, nanoporous polyimide (PI) membranes with excellent thermal stability as high-safety separators is developed for LIBs using a superspreading strategy. The superspreading of polyamic acid solutions enables the generation of thin and uniform liquid layers, facilitating the formation of thin PI membranes with controllable and uniform nanopores with narrow size distribution ranging from 121±5nm to 86±6nm. Such nanoporous PI membranes display excellent structural stability at elevated temperatures up to 300°C for at least 1h. LIBs assembled with nanoporous PI membranes as separators show high specific capacity and Coulombic efficiency and can work normally after transient treatment at a high temperature (150°C for 20min) and high ambient temperature, indicating their promising application as high-safety separators for rechargeable batteries.

Constructing Highly Emissive Covalent Organic Frameworks for Fe3+ Ion Detection via Wall Function.

Covalent organic frameworks (COFs) represent a new type of crystalline porous polymers that possess pre-designed skeletons, uniform nanopores, and ordered π structure. These attributes make them well-suited for the design of light-emitting materials. However, the majority of COFs exhibits poor luminescence due to aggregation-caused quenching (ACQ), resulting from the strong interaction between adjacent layers. To break the limitation, the building units with three methoxy groups on the walls are used to construct TM-OMe-EBTHz-COF, which suppresses the ACQ effects to improve light-emitting activity of COF. The TM-OMe-EBTHz-COF exhibits a notable emission of yellow-green luminescence in the solid state, with a remarkably high absolute quantum yield of 21.1%. The methoxy groups and hydrazine linkage form three coordination sites, contributing to excellent performance in metal ions sensing. The TM-OMe-EBTHz-COF demonstrates high sensitivity and selectivity to Fe3+ ion. Importantly, the low detection limit is below 150 nanomolar, ranking it among the best-performing Fe3+ sensor systems.

Glycerol-tailored asymmetric polyethersulfone membranes with uniform ion transport for stable lithium metal batteries

Advancing the performance and stability of lithium metal batteries is crucial for future energy storage devices. One of the major challenges for practical applications of Li metal batteries is to mitigate the formation of Li dendrites during cycling. In this work, we prepared a series of asymmetrically structured polyethersulfone (PES) membranes, consisting of a nanoporous skin layer and a bulk with macrovoids, by incorporating different amounts of glycerol during membrane preparation. Under optimal conditions, the asymmetric PES membrane made with 1.2 wt% of glycerol (PES-G1.2) possesses a thin skin layer with a uniform nanopore distribution, which is ideal for regulating the ion flux near the Li anode surface, thus suppressing Li dendrite formation. Our results demonstrate that the PES-G1.2 possesses exceptional ionic conductivity of 1.76 mS cm−1, Li+ transference number of 0.52, and high compatibility with Li electrode. Additionally, the Li/PES-G1.2/LiFePO4 cells also present a remarkable rate capability with specific capacity of 150 mAh g−1 at 0.2 C and 81 mAh g−1 at 10 C, respectively, and 90 % of capacity can be retained after 100 charge-discharge cycles under 0.2 C. These findings shed light on the unique properties of asymmetric porous membrane as well as its promising potential for applications in lithium metal batteries.

Additive Manufacturing of Transparent Multi-Component Nanoporous Glasses.

Fabrication of glass with complex geocd the low resolution of particle-based or fused glass technologies. Herein, a high-resolution 3D printing of transparent nanoporous glass is presented, by the combination of transparent photo-curable sol-gel printing compositions and digital light processing (DLP) technology. Multi-component glass, including binary (Al2 O3 -SiO2 ), ternary (ZnO-Al2 O3 -SiO2 , TiO2 -Al2 O3 -SiO2 ), and quaternary oxide (CaO-P2 O5 -Al2 O3 -SiO2 ) nanoporous glass objects with complex shapes, high spatial resolutions, and multi-oxide chemical compositions are fabricated, by DLP printing and subsequent sintering process. The uniform nanopores of Al2 O3 -SiO2 -based nanoporous glasses with the diameter (≈6.04nm), which is much smaller than the visible light wavelength, result in high transmittance (>95%) at the visible range. The high surface area of printed glass objectives allows post-functionalization via the adsorption of functional guest molecules. The photoluminescence and hydrophobic modification of 3D printed glass objectives are successfully demonstrated. This work extends the scope of 3D printing to transparent nanoporous glasses with complex geometry and facile functionalization, making them available for a wide range of applications.

Confined amphipathic ionic-liquid regulated anodic aluminum oxide membranes with adjustable ion selectivity for improved osmotic energy conversion

To attain carbon neutrality and carbon peaking, there is an urgent need to convert the vast amount of blue energy present between seawater and river water into usable electricity. Reverse electrodialysis based on ion-exchange membranes is a promising way to efficiently achieve osmotic energy conversion. Anodic aluminum oxide (AAO) membranes are frequently used for osmotic energy harvesting because of their uniform nanopore channels, high flux, and excellent stability. However, the existing surface modification methods are complex and inefficient. In this study, an amphiphilic ionic liquid was selected to modify a porous anodic alumina membrane via simple capillary insertion. Due to the abundance of pH-dependent amphiphilic OH groups on the surface of AAO pore channels, the ionic liquids not only provide abundant surface charge but can also intelligently adjust its surface charge to different environments. In addition, it fills the AAO nanochannels to provide a continuous ion transport network. The modified hybrid membrane achieves efficient and stable osmotic energy conversion performance. This simple and feasible strategy paves the way for further improvements in commercial membranes.

Suppressed Size Effect in Nanopillars with Hierarchical Microstructures Enabled by Nanoscale Additive Manufacturing.

Studies on mechanical size effects in nanosized metals unanimously highlight both intrinsic microstructures and extrinsic dimensions for understanding size-dependent properties, commonly focusing on strengths of uniform microstructures, e.g., single-crystalline/nanocrystalline and nanoporous, as a function of pillar diameters, D. We developed a hydrogel infusion-based additive manufacturing (AM) technique using two-photon lithography to produce metals in prescribed 3D-shapes with ∼100 nm feature resolution. We demonstrate hierarchical microstructures of as-AM-fabricated Ni nanopillars (D ∼ 130-330 nm) to be nanoporous and nanocrystalline, with d ∼ 30-50 nm nanograins subtending each ligament in bamboo-like arrangements and pores with critical dimensions comparable to d. In situ nanocompression experiments unveil their yield strengths, σ, to be ∼1-3 GPa, above single-crystalline/nanocrystalline counterparts in the D range, a weak size dependence, σ ∝ D-0.2, and localized-to-homogenized transition in deformation modes mediated by nanoporosity, uncovered by molecular dynamics simulations. This work highlights hierarchical microstructures on mechanical response in nanosized metals and suggests small-scale engineering opportunities through AM-enabled microstructures.

Nasschemische Bottom‐up Synthese von Graphen‐Nanostreifen mit atompräzisen Nanoporen

AbstractDie Inkorporation von Nanoporen in Graphen‐Nanostrukturen wurde als effiziente Methode zur Anpassung der Bandlücke und elektronischen Struktur dieser Materialien demonstriert. Allerdings ist die atomgenaue Einbettung uniformer Nanoporen in Graphen‐Nanostreifen (GNS, engl. GNR) auf atomarer Ebene durch Mangel an effizienten Synthesestrategien bislang unterentwickelt. Wir berichten hier vom ersten lösungschemisch dargestellten, vollständig durch Scholl‐Reaktion konjugierten porösen GNS (pGNS), welchen wir durch das atomgenau dargestellte Polyphenylen P1 mit vorinstallierten hexagonalen Makrozyklen zugänglich machen konnten. pGNS enthält periodische Poren im sub‐Nanometerbereich (0.6 nm) mit einem Abstand von 1.7 nm zueinander. Um unsere Synthesestrategie zu untermauern, wurden zwei poröse Modellverbindungen (1 a, 1 b) mit einer zu pGNS identischen Pore erfolgreich dargestellt. Die chemische Struktur und photophysikalischen Eigenschaften von pGNS wurden durch verschiedene spektroskopische Methoden untersucht. Die eingebetteten periodischen Nanoporen vermindern die π‐Konjugation und damit die Interaktion zwischen den Nanostreifen, verglichen mit nicht porösen GNS von ähnlicher Breite. pGNS zeigt demzufolge eine erhöhte Bandlücke und eine verbesserte nasschemische Prozessierbarkeit.

Bottom-up Solution Synthesis of Graphene Nanoribbons with Precisely Engineered Nanopores.

The incorporation of nanopores into graphene nanostructures has been demonstrated as an efficient tool in tuning their band gaps and electronic structures. However, precisely embedding the uniform nanopores into graphene nanoribbons (GNRs) at the atomic level remains underdeveloped especially for in-solution synthesis due to the lack of efficient synthetic strategies. Herein we report the first case of solution-synthesized porous GNR (pGNR) with a fully conjugated backbone via the efficient Scholl reaction of tailor-made polyphenylene precursor (P1) bearing pre-installed hexagonal nanopores. The resultant pGNR features periodic subnanometer pores with a uniform diameter of 0.6 nm and an adjacent-pores-distance of 1.7 nm. To solidify our design strategy, two porous model compounds (1 a, 1 b) containing the same pore size as the shortcuts of pGNR, are successfully synthesized. The chemical structure and photophysical properties of pGNR are investigated by various spectroscopic analyses. Notably, the embedded periodic nanopores largely reduce the π-conjugation degree and alleviate the inter-ribbon π-π interactions, compared to the nonporous GNRs with similar widths, affording pGNR with a notably enlarged band gap and enhanced liquid-phase processability.

Fabrication of Fullerene-Pillared Porous Graphene and Its Water Vapor Adsorption

Porous carbons with large pore volumes and surface areas provide high performance in gas separation, water purification, and storage. Carbon composites comprising nanocarbons can offer uniform pore structures with unique adsorption properties. In this work, we prepared fullerene-pillared porous graphene by bottom-up processing and demonstrated its water vapor adsorption properties both experimentally and through the grand canonical Monte Carlo simulations. Fullerene-pillared porous graphene with 4% fullerene slightly adsorbed water vapor, and the adsorption amount decreased on highly laminated fullerene-pillared porous graphene with 5% fullerene owing to nanopore collapse. Fullerene-pillared porous graphene with 25 ± 8% fullerene had the largest water vapor adsorption capacity at 40% relative humidity. On the contrary, fullerene-pillared porous graphene with 50% fullerene showed reduced water vapor adsorption, consistent with the simulation results showing that inadequate nanospaces prevented water cluster formation because of excess fullerene molecules. Therefore, the best candidate with high adsorption capacity and uniform nanopores was found to be the fullerene-pillared porous graphene with a 25 ± 8% fullerene filling ratio.

Assembling Triphenylene-Based Metal-Organic Framework Nanosheets at the Air/Liquid Interface: Modification by Tuning the Spread Solution Concentration.

Metal-organic frameworks (MOFs)─crystalline coordination polymers─with unique characteristics such as structural designability accompanied by tunable electronic properties and intrinsic uniform nanopores have become the platform for applications in diverse scientific areas ranging from nanotechnology to energy/environmental sciences. To utilize the superior features of MOF in potential applications, the fabrication and integration of thin films are of importance and have been actively sought. Especially, downsized MOFs into nanosheets can act as ultimately thin functional components in nanodevices and potentially display unique chemical/physical properties rarely seen in bulk MOFs. Assembling nanosheets by aligning amphiphilic molecules at the air/liquid interface has been known as the Langmuir technique. By utilizing the air/liquid interface as a reaction field between metal ions and organic ligands, MOFs are readily formed into the nanosheet state. The expected features in MOF nanosheets including electrical conduction largely depend on the nanosheet characteristics such as lateral size, thickness, morphology, crystallinity, and orientation. However, their control has not been achieved as yet. Here, we demonstrate how changing the concentration of a ligand spread solution can modify the assembly of MOF nanosheets, composed of 2,3,6,7,10,11-hexaiminotriphenylene (HITP) and Ni2+ ions (HITP-Ni-NS), at the air/liquid interface. A systematic increase in the concentration of the ligand spread solution leads to the enlargement of both the lateral size and the thickness of the nanosheets while retaining their perfect alignment and preferred orientation. On the other hand, at much higher concentrations, we find that unreacted ligand molecules are included in HITP-Ni-NS, introducing disorder in HITP-Ni-NS. These findings can develop further sophisticated control of MOF nanosheet features, accelerating fundamental and applied studies on MOFs.

Molecular modeling of gaseous mercury species adsorption and transport in nanoporous silica membranes

The separation of Hg and HgO from industrial flue gas is an issue of much interest in the control of heavy metal emissions, and its feasibility for kinetic and equilibrium separation of Hg and HgO from N2 using disordered silica is theoretically investigated here using a combination of pore level transport modelling and effective medium theory. It is found that the classical Knudsen model generally leads to considerable over-prediction of the effective diffusion coefficient in the nanoporous silica compared to the more accurate Oscillator model that considers fluid–solid interaction. It is seen that nanoporous silica membranes are kinetically selective to nitrogen, the major component of flue gas, relative to Hg and HgO. Nevertheless, the kinetic selectivity for N2 is low, and only about 2–3, indicating that the kinetic separation of mercury species from flue gas is not practically feasible. On the other hand, the equilibrium selectivity of HgO over N2 is over 50 at 0.75 nm modal radius, while that for Hg exceeds 30 at 0.3 nm radius, suggesting this method of separation to be appropriate. Narrow pore silica materials of uniform nanopore size of about 0.3–0.75 nm are found to be optimal for the removal of mercury species.

Non-Stop Switching Separation of Superfine Solid/Liquid Dispersed Phases in Oil and Water Systems Using Polymer-Assisted Framework Fiber Membranes.

Fabricating filtration membranes with wide applicability and high efficiency is always a challenge in the precise separation of small colloidal particles under mild conditions. For this purpose, a strategy mixing supramolecular framework fiber with polymer is adopted. The fibrous assembly in the gel state provides uniform nanopores for both channel and interception and controlled wettability for lyophilic/lyophobic switching. The used polymer fills the gaps between fiber assemblies and improves the mechanical property. The composite membrane shows both under-oil superhydrophobic and underwater superoleophobic nature, which allows the conversions via in situ modulation of joystick solvents. Based on surface wetting and size-sieving, ultrafine hard nanoparticles dispersing in both hydrophobic organic solvents and water are selectively sieved. In addition, on-demand separation of water-in-oil and oil-in-water microemulsions without and with surfactants as systems containing soft droplets are realized. The smallest cut-off size of ≈3nm is achieved for both hard and soft emulsions, while separation efficiency maintains during sustained in situ reversible switches.

Supramolecular framework membrane for precise sieving of small molecules, nanoparticles and proteins

Synthetic framework materials have been cherished as appealing candidates for separation membranes in daily life and industry, while the challenges still remain in precise control of aperture distribution and separation threshold, mild processing methods, and extensive application aspects. Here, we show a two-dimensional (2D) processible supramolecular framework (SF) by integrating directional organic host-guest motifs and inorganic functional polyanionic clusters. The thickness and flexibility of the obtained 2D SFs are tuned by the solvent modulation to the interlayer interactions, and the optimized SFs with limited layers but micron-sized areas are used to fabricate the sustainable membranes. The uniform nanopores allow the membrane composed of layered SF to exhibit strict size retention for substrates with the rejection value of 3.8 nm, and the separation accuracy within 5 kDa for proteins. Furthermore, the membrane performs high charge selectivity for charged organics, nanoparticles, and proteins, due to the insertion of polyanionic clusters in the framework skeletons. This work displays the extensional separation potentials of self-assembled framework membranes comprising of small-molecules and provides a platform for the preparation of multifunctional framework materials due to the conveniently ionic exchange of the counterions of the polyanionic clusters.