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Abstract Selective ion transport underpins fundamental biological processes for efficient energy conversion and signal propagation. Mimicking these ‘ionics’ in synthetic nanofluidic channels has been increasingly promising for realizing self-sustained systems by harvesting clean energy from diverse environments, such as light, moisture, salinity gradient, etc. Here, we report a spatially nanoconfined ion separation strategy that enables harvesting electricity from CO2 adsorption. This breakthrough relies on the development of Nanosheet-Agarose Hydrogel (NAH) composite-based generators, wherein the oppositely charged ions are released in water-filled hydrogel channels upon adsorbing CO2. By tuning the ion size and ion-channel interactions, the released cations at the hundred-nanometer scale are spatially confined within the hydrogel network, while ångström-scale anions pass through unhindered. This leads to near-perfect anion/cation separation across the generator with a selectivity (D-/D+) of up to 1.8 × 106, allowing conversion into external electricity. With amplification by connecting multiple as-designed generators, the ion separation-induced electricity reaching 5 V is used to power electronic devices. This study introduces an effective spatial nanoconfinement strategy for widely demanded high-precision ion separation, encouraging a carbon-negative technique with simultaneous CO2 adsorption and energy generation.

Abstract Covalent modification is commonly used to tune the channel size and functionality of 2D membranes. However, common synthesis strategies used to produce such modifications are known to disrupt the structure of the membranes. Herein, we report less intrusive yet equally effective non-covalent modifications on Ti3C2T x MXene membranes by a solvent treatment, where the channels are robustly decorated by protic solvents via hydrogen bond network. The densely functionalized (-O, -F, -OH) Ti3C2T x channel allows multiple hydrogen bond establishment and its sub-1-nm size induces a nanoconfinement effect to greatly strengthen these interactions by maintaining solvent-MXene distance and solvent orientation. In sub-1-nm ion sieving and separation, as-decorated membranes exhibit stable ion rejection, and proton-cation (H+/Mn+) selectivity that is up to 50 times and 30 times, respectively, higher than that of pristine membranes. It demonstrates the feasibility of non-covalent methods as a broad modification alternative for nanochannels integrated in energy-, resource- and environment-related applications.

Abstract Engineering different two-dimensional materials into heterostructured membranes with unique physiochemical properties and molecular sieving channels offers an effective way to design membranes for fast and selective gas molecule transport. Here we develop a simple and versatile pyro-layering approach to fabricate heterostructured membranes from boron nitride nanosheets as the main scaffold and graphene nanosheets derived from a chitosan precursor as the filler. The rearrangement of the graphene nanosheets adjoining the boron nitride nanosheets during the pyro-layering treatment forms precise in-plane slit-like nanochannels and a plane-to-plane spacing of ~3.0 Å, thereby endowing specific gas transport pathways for selective hydrogen transport. The heterostructured membrane shows a high H2 permeability of 849 Barrer, with a H2/CO2 selectivity of 290. This facile and scalable technique holds great promise for the fabrication of heterostructures as next-generation membranes for enhancing the efficiency of gas separation and purification processes.

The fabrication of synthetic nanochannels for ion separation is challenging. Here, the authors synthesize angstrom-scale ion channels featuring one-dimensional to three-dimensional pore configurations by growing metal‒organic frameworks into nanochannels; the structure of the pore influences the ion transport performance.

Top-down exfoliation is one of the most promising approaches for the scalable production of 2D materials, but the current techniques are limited by low yield of monolayers. Here, the authors report the exfoliation of graphene and other layered materials via viscous-polymer-assisted ball-milling, leading to a production of graphene products with monolayer percentage up to 97.9% at a yield of 78.3%.

While renewable H2 production offers a promising route for clean energy production, there is an urgent need to improve catalyst performances. Here, authors design a Pt-containing complex oxide that utilizes atomic-scale hydrogen spillover to promote H2 evolution electrocatalysis in acidic media.

Dense ceramic membranes with H+ or O2− conductivity have been widely used for fuel production through electro-hydrogenation/dehydrogenation or electro-oxygenation/deoxygenation. Electrochemical conversion processes demonstrate advantages over conventional redox reaction processes in terms of capital cost, energy savings, process intensification and product selectivity. Intermittent renewable power (e.g., solar and wind power) can be used to drive electrochemical processes so that renewable energy is stored in fuels as energy carriers, including hydrogen, ammonia, syngas, methane and ethylene. This review summarizes the pathways to store renewable energy via ion-conducting membrane reactors and discusses the commercialization progress and prospects of these energy technologies.

Excessive fluoride anions in drinking water are toxic to the health of human beings. In this article, an effective fluoride removal adsorbent on the basis of amino-functionalized porous polydivinylbenzene (PDVB) was prepared through low cost processes, which included solvothermal preparation of porous PDVB and subsequent surface amino-functionalization. The obtained amino-functionalized porous PDVB (A-PDVB) has high surface area of 443 m2 g−1 and high adsorption capacity towards fluoride anion up to 105.9 mg g−1. Considering adsorbents surface area, the adsorption capacity per unit surface area of A-PDVB is 0.24 mg m−2 which is more than 4 times of porous PDVB (0.058 mg m−2). The enhanced adsorption performance of A-PDVB was due to amino groups electrostatic interaction coupled with hydrogen bond binding with fluoride anions. In addition, the amino-functionalized porous PDVB could be regenerated in high efficiency under alkaline conditions. This work not only exhibits the possibility of A-PDVB for application as an environment-friendly adsorbent for fluoride removal but also gives an insight into understanding mechanism of the fluoride anions adsorption onto amino-functionalized porous PDVB.

Graphene based nanosheets have been widely used as building blocks for fabrication of superior separation membrane for water processing. In particular, membranes made of reduced graphene oxide (rGO) show better stability compared with graphene oxide (GO). However, densely stacked of rGO often results in low water flux. In this study, cellulose nanofibers (CNFs) were incorporated into the rGO laminates by vacuum filtration of dilute GO/CNF solution and thermal reduction at 150 °C for 1.5 h. The resulting rGO/CNF membrane was treated with oxygen plasma for 1–4 min to create nanopores on the membrane surface for the purpose of enhancing nanofiltration performance. The results showed that the optimum membrane performance was obtained by using the equal amount of GO (31.83 mg m-2) and CNFs accompanied by 3 min of plasma treatment, exhibiting a pure water permeance of 37.2 ± 3.9 L m-2 h-1 bar-1 maintaining a rejection above 90% for Acid Fuchsin (1.2×1.1 nm), Rose Bengal (1.5×1.2 nm) and Brilliant Blue (2.2×1.7 nm).

Membranes are widely used in separation processes due to their low energy requirement, small footprint and simplicity. New membranes have been developed based on novel materials and fabrication techniques to address separation challenges in the field of membrane science. In the case of liquid phase separations, ion-ion separation and chiral resolution using membranes have attracted growing interest for their applications such as in high-value mineral extraction and pharmaceutical manufacturing. Furthermore, reverse osmosis operation favors ultra-high-pressure range for treating feed with higher salinity with higher water recovery. Herein we highlight the latest development and design approaches of single species-selective membranes and pressure-resistant membranes and discuss the current limitations of membrane separation in the liquid phase. We subsequently review recent advancement in the fabrication techniques that enable the making of these membranes from emerging materials.

Efficient electrocatalysts are crucial for the sustainable hydrogen production as an alternative clean fuel. Here, the authors explore a single-phase perovskite oxide as a high-performance hydrogen evolution electrocatalyst via super-exchange induced atomic scale synergistic active sites.

Metal-organic frameworks are promising for a range of applications, but architectural control is challenging. Here the authors use solvent-assisted ligand exchange to access a variety of metal-organic framework nanomaterials for precursors of nanoporous carbon with sodium ion storage properties.

While biological fluoride ion channels display excellent F− conductivity and selectivity, designing synthetic analogues remains highly challenging. Here the authors show that zirconium-based metal–organic frameworks with F− binding sites and sub-1-nanometer channels exhibit ultrahigh F− conductivity and selectivity.

Code obfuscation built upon code virtualization technology is one of the viable means for protecting sensitive algorithms and data against code reverse engineering attacks. Code virtualization has been successfully applied to programming languages like C, C++, and Java. However, it remains an outstanding challenge to apply this promising technique to JavaScript, a popular web programming language. This is primarily due to the open visibility of JavaScript code and the expensive runtime overhead associated with code virtualization. This paper presents JSPro, a novel code virtualization system for JavaScript. JSPro is the first JavaScript code obfuscation tool that builds upon the emerging WebAssembly language standard. It is designed to provide more secure code protection but without incurring a significant runtime penalty, explicitly targeting numerical JavaScript kernels. We achieve this by first automatically translating the target JavaScript code into WebAssembly and then performing code obfuscation on the compiled WebAssembly binary. Our design has two advantages over existing solutions: (1) it increases the code reverse entering complexity by implementing code obfuscation at a lower binary level and (2) it significantly reduces the performance impact of code virtualization over the native JavaScript code by using the performance-tuned WebAssembly language. We evaluate JSPro on a set of numerical JavaScript algorithms widely used in many applications. To test the performance, we apply JSPro to four mainstream web browsers running on three distinct mobile devices. Compared to state-of-the-art JavaScript obfuscation tools, JSPro not only provides stronger protection but also reduces the runtime overhead by at least 15% (up to 38.2%) and the code size by 28.2% on average.

To protect programs from unauthorized analysis, virtualize the code based on Virtual Machine (VM) technologies is emerging as a feasible method for accomplishing code obfuscation. However, in some State-of-the-art VM-based protection approaches, the set of virtual instructions and bytecode interpreters are fixed across the whole programs. This means an experienced attacker could extract the mapping information between virtual instructions and native code from programs, and use this knowledge to uncover the mapping relationships in similar protecting applications. To address this problem, we present CoDiver (Code Virtualization Protection with Diversity), a novel VM-based code obfuscation system in this paper. The main idea of our approach is to obfuscate the mapping between the opcodes of bytecode instructions and their semantics. To achieve this goal, we first turn every protected code region into multiple parts by partition proceeding, randomize the mapping of opcodes and their semantics of each part. By this way, we could translate the bytecode instruction into different native code in different sections of the obfuscated code. This method could increase the diversity of program behavior significantly. As a result, it will be useless to learn the mapping relationship between bytecode and native code of some other programs, then migrate it into a new program. We build a prototype of CoDiver and tested it on a set of real-world applications. Experimental results show that as compared with two state-of-the-art VM-based code obfuscation approaches, our approach is more effective and could provide stronger protection with comparable runtime overhead and code size.

Water may serve as a renewable hydrogen fuel source to replace fossil fuels, although such electrolysis requires highly active catalysts. Here, authors explore Ruddlesden−Popper oxides as hydrogen evolution electrocatalysts that feature an unusual synergistic effect to promote high activity.

Abstract Emerging anionic redox chemistry presents new opportunities for enhancing oxygen evolution reaction (OER) activity considering that lattice‐oxygen oxidation mechanism (LOM) could bypass thermodynamic limitation of conventional metal‐ion participation mechanism. Thus, finding an effective method to activate lattice‐oxygen in metal oxides is highly attractive for designing efficient OER electrocatalysts. Here, we discover that the lattice‐oxygen sites in Ruddlesden‐Popper (RP) crystal structure can be activated, leading to a new class of extremely active OER catalyst. As a proof‐of‐concept, the RP Sr3(Co0.8Fe0.1Nb0.1)2O7‐δ (RP‐SCFN) oxide exhibits outstanding OER activity (eg, 334 mV at 10 mA cm−2 in 0.1 M KOH), which is significantly higher than that of the simple SrCo0.8Fe0.1Nb0.1O3‐δ perovskite and benchmark RuO2. Combined density functional theory and X‐ray absorption spectroscopy studies demonstrate that RP‐SCFN follows the LOM under OER condition, and the activated lattice oxygen sites triggered by high covalency of metal‐oxygen bonds are the origin of the high catalytic activity.

Summary: Effective design of bifunctional catalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is important but remains challenging. Herein, we report a three-dimensional (3D) hierarchical structure composed of homogeneously distributed Ni-Fe-P nanoparticles embedded in N-doped carbons on nickel foams (denoted as Ni-Fe-P@NC/NF) as an excellent bifunctional catalyst. This catalyst was fabricated by an anion exchange method and a low-temperature phosphidation of nanotubular Prussian blue analogue (PBA). The Ni-Fe-P@NC/NF displayed exceptional catalytic activity toward both HER and OER and delivered an ultralow cell voltage of 1.47 V to obtain 10 mA cm−2 with extremely excellent durability for 100 h when assembled as a practical electrolyser. The extraordinary performance of Ni-Fe-P@NC/NF is attributed to the abundance of unsaturated active sites, the well-defined hierarchical porous structure, and the synergistic effect between multiple components. Our work will inspire more rational designs of highly active non-noble electrocatalysts for industrial energy applications. : Catalysis; Materials Chemistry; Nanomaterials; Energy Materials Subject Areas: Catalysis, Materials Chemistry, Nanomaterials, Energy Materials

Carbon nanotubes (CNTs) were incorporated into alumina/polyethersulfone hollow fibre membranes to enhance the mechanical property and the efficiency of water treatment. Results show that the incorporation of CNTs can greatly limit the formation of large surface pores, decrease the void size in support layers and improve the porosity and pore connectivity of alumina/polyethersulfone membranes. As a result of such morphology change and pore size change, both improved flux and rejection were achieved in such CNTs/alumina/polyethersulfone membranes. Moreover, the CNTs/alumina/PES membranes show higher antifouling ability and the flux recoveries after being fouled by bovine serum albumin (BSA) and humic acid were improved by 84.1% and 53.2% compared to the samples without CNT incorporation. Besides the improvement in water treatment performance, the incorporation of CNTs enhanced the tensile properties of inorganic/polymer membranes. Therefore, such CNTs/alumina/PES hollow fiber membranes are very promising candidates for good filter media in industry, considering their high efficiency and high mechanical properties.

Internal concentration polarization (ICP) in forward osmosis (FO) process is a characteristic problem for asymmetric thin-film composite (TFC) FO membrane which leads to lower water flux. To mitigate the ICP effect, modification of the substrates’ properties has been one of the most effective methods. A new polyethersulfone-based ultrafiltration membrane with increased surface porosity and high water flux was recently produced by incorporating Zn2GeO4 nanowires. The composite membrane was used as a substrate for the fabrication of TFC FO membrane, by coating a thin layer of polyamide on top of the substrate. The substrate and the nanowires were characterized by a range of techniques such as SEM, XRD, and contact angle goniometry. The water permeability and molecular weight cut-offs (MWCO) of the substrate; and the FO performance of the TFC membrane were also determined. The Zn2GeO4-modified membrane showed ~45% increase in water permeability and NaCl salt rejection of 80% under RO mode. In FO mode, the ratio of water flux to reverse solute flux was also improved. However, lower FO flux was obtained which could be due to ICP. The result shows that Zn2GO4 nanowire may be used as a modifier to the substrate to improve the quality of the polyamide layer on the substrate to improve the flux and selectivity, but not as effective in reducing ICP. This work demonstrates that the incorporation of nanomaterials to the membrane substrate may be an alternative approach to improve the formation of polyamide skin layer to achieve better FO performance.

Metal-organic frameworks (MOFs) are superior ion adsorbents for selectively capturing toxic ions from water. Nevertheless, they have rarely been reported to have lithium selectivity over divalent cations due to the well-known flexibility of MOF framework and the similar physiochemical properties of Li+ and Mg2+. Herein, we report an ion-sieving adsorption approach to design sunlight-regenerable lithium adsorbents by subnanoporous MOFs for efficient lithium extraction. By integrating the ion-sieving agent of MOFs with light-responsive adsorption sites of polyspiropyran (PSP), the ion-sieving adsorption behaviors of PSP-MOFs with 6.0, 8.5, and 10.0 Å windows are inversely proportional to their pore size. The synthesized PSP-UiO-66 with a narrowest window size of 6.0 Å shows high LiCl adsorption capacity up to 10.17 mmol g−1 and good Li+ / Mg2+ selectivity of 5.8 to 29 in synthetic brines with Mg/Li ratio of 1 to 0.1. It could be quickly regenerated by sunlight irradiation in 6 min with excellent cycling performance of 99% after five cycles. This work sheds light on designing selective adsorbents using responsive subnanoporous materials for environmentally friendly and energy-efficient ion separation and purification. [ABSTRACT FROM AUTHOR]

Super-glassy polymer membranes have suffered from the trade-off relationship between permeability and selectivity for gas separation applications, despite the fact that membrane technology exhibits remarkable energy efficiency advantages over other separation methods. Polymers of intrinsic microporosity such as PIM-1 offer high fractional free volume (FFV) and intermediate gas selectivity, with permeability several orders of magnitude higher than conventional glassy polymers. The methods of producing mixed matrix membranes (MMM) by incorporating nanoparticles into a polymer matrix, or crosslinking, have been widely studied to improve membrane selectivity. While crosslinking and nanoparticle incorporation often increase selectivity or permeability, respectively, this is typically at the expense of the other, limiting transport properties to the Robeson upper bound. Porous aromatic frameworks such as PAF-1 have been shown to significantly increase the permeability of PIM membranes. Here, this nanoparticle additive is coupled with post UV irradiation treatment resulting in a membrane with both significantly improved membrane selectivity (i.e., 16-fold improvement for H2/CH4 selectivity, from 5.4 to 90) and high permeability (i.e., P(H2) = 4800 Barrer). Characterisation of the dual-enhanced membrane revealed that the synergetic performance is caused by a combination of the selective skin layer formed upon UV photo-oxidation with the additional permeable gas transport channels introduced to the bulk matrix by PAF-1. As a result of this dual-approach to membrane enhancement, the PIM-1 MMM exhibited better gas separation performance, surpassing the 2015 upper bounds for H2/N2 and H2/CH4 as well as 2008 upper bounds for H2/CO2 and CO2/CH4. Aging studies confirmed that PAF-1 addition, UV irradiation, and both modifications slowed physical aging rate compared to the pure PIM-1 membrane. The performance of this membrane was also investigated at a range of thicknesses, revealing its potential as a candidate for other membrane forms at scale. [ABSTRACT FROM AUTHOR]

1D nanochannels modified with responsive molecules are fabricated to replicate gating functionalities of biological ion channels, but gating effects are usually weak because small molecular gates cannot efficiently block the large channels in the closed states. Now, 3D metal–organic framework (MOF) sub‐nanochannels (SNCs) confined with azobenzene (AZO) molecules achieve efficient light‐gating functionalities. The 3D MOFSNCs consisting of a MOF UiO66 with ca. 9–12 Å cavities connected by ca. 6 Å triangular windows work as angstrom‐scale ion channels, while confined AZO within the MOF cavities function as light‐driven molecular gates to efficiently regulate the ion flux. The AZO‐MOFSNCs show good cyclic gating performance and high on–off ratios up to 17.8, an order of magnitude higher than ratios observed in conventional 1D AZO‐modified nanochannels (1.3–1.5). This work provides a strategy to develop highly efficient switchable ion channels based on 3D porous MOFs and small responsive molecules. [ABSTRACT FROM AUTHOR]

A new strategy to construct a hierarchically structured separation layer on a porous substrate using large titanate nanofibers and smaller boehmite nanofibers is presented. This approach helps to design next generation of ceramic membranes with high fluxes.

The novel oriented electrospun nanofiber membrane composed of MOFs and SPPESK has been synthesized for proton exchange membrane fuel cell operating at high temperature and anhydrous conditions. It is clear that the oriented nanofiber membrane displays the higher proton conductivity than that of the disordered nanofiber membrane or the membrane prepared by conventional solvent-casting method (without nanofibers). Nanofibers within the membranes are significantly oriented. The proton conductivity of the oriented nanofiber membrane can reach up to (8.2 ± 0.16) × 10-2 S cm-1 at 160°C under anhydrous condition for the highly orientation of nanofibers. Moreover, the oxidative stability and resistance of methanol permeability of the nanofibers membrane are obviously improved with an increase in orientation of nanofibers. The observed methanol permeability of 0.707 × 10-7 cm2 s-1 is about 6% of Nafion-115. Consequently, orientated nanofibers membrane is proved to be a promising material as the proton exchange membrane for potential application in direct methanol fuel cells. [ABSTRACT FROM AUTHOR]

Zeolitic imidazolate frameworks (ZIFs), a subclass of metal organic frameworks, are built of tetrahedral metal ions bridged by imidazolates. They have permanent porosity and relatively high thermal and chemical stability, which make them attractive candidates for many industrial applications. In recent years, significant progress has been made in developing ZIFs into membranes and thin films for gas separation, liquid separation (pervaporation) and functional devices. Various techniques, such as direct synthesis, secondary synthesis, reactive seeding and functional chemicals as linkers, and contra-diffusion synthesis, have been reported for the fabrication of ZIF membranes and films. As ZIFs have good compatibility with polymers, they have been incorporated into polymers with high loadings to form mixed matrix membranes. The resulting symmetric dense or asymmetric composite membranes exhibit good performance in gas separation and liquid separation via pervaporation. The recent developments of ZIF membranes/films, ZIF-polymer mixed matrix membranes and their applications are reviewed in this article. [ABSTRACT FROM AUTHOR]

A new MnO[sub 2]@Co[sub 3]O[sub 4] hybrid with small-sized Co[sub 3]O[sub 4] nanoparticles grown on Ω-MnO[sub 2] nanotubes was prepared from a low concentration precursor solution by a facile two-step hydrothermal synthesis method, and its charge storage properties were investigated by cyclic voltammetry and galvanostatic charge-discharge measurements. Due to their hybrid structure, the well-dispersed Co[sub 3]O[sub 4] nanoparticles not only facilitated the charge and ion transfer, but also hindered the dissolution of Mn species; this type of hybrid maximized the electroactivity of both components. The hybrid exhibited a specific capacitance of 234 F g[sup -1], which was greater than those of pristine Ω-MnO[sub 2] nanotubes and a physical mixture of Ω-MnO[sub 2] nanotubes and Co[sub 3]O[sub 4] nanoparticles at a current density of 200 mA g[sup -1]. The hybrid also showed good rate capacity and long-term cycling performance. [ABSTRACT FROM AUTHOR]

Brittleness is the main obstacle for commercial implementation of ceramic hollow fiber membranes. Here we report the reinforcement of porous alumina hollow fiber membranes by using commercial SiC nanofibers. The SiC reinforced alumina hollow fiber membranes were produced by the polymer-assisted phase inversion method and subsequent removal of the polymer and sintering at high temperatures. The effects of the amounts of SiC nanofibers (2.5-10.0 wt%) on the mechanical strength, microstructure and water flux of the hollow fiber membranes were investigated. The results showed that without addition of SiC nanofibers, the maximum bending strength was about 154 MPa for the porous alumina hollow fiber sintered at 1510 °C However, the maximum bending strength of the reinforced membrane reached 218 MPa, in which 5 wt% SiC was incorporated and sintered at 1450 °C; in other words, a 40% improvement in bending strength was achieved. After being sintered at 1450 °C, the 5% SiC reinforced membrane exhibits a porosity of 41.7% and a peak pore size of 1.35 μm whereas the pure alumina membrane has a porosity of 37.5% and a peak pore size of 1.25 μm; the former shows a water permeability of 7.99 L m-2 h[sup -1] kPa-1, which is 3.3 times higher than that of the latter. Therefore, the ceramic nanofiber reinforcement is promising for the development of high-performance ceramic hollow fiber membranes for practical applications. [ABSTRACT FROM AUTHOR]

Highly crystalline perovskite ceramics were templated by an eggshell membrane (ESM) viastrong metal-protein bonding. Templated Sm0.5Sr0.5CoO3(SSC) ceramics retained an interwoven fibrous structure at a temperature up to 1000 °C. The use of citric acid-assisted sol–gel coating in the template synthesis greatly enhanced the crystallininty of the ceramic because the sol–gel process ensured the stoichiometric adsorption of ceramic precursors, and it also affected ceramic morphology. The highly crystalline SSC ceramic was used as a cathode material of solid oxide fuel cell (SOFC), and the cathode properties were compared with those prepared with the ceramic synthesized viaa conventional combustion method. The maximum power density of the cell made with the templated SSC was 44.5% and 29.8% higher than that made with the combusted SSC at 600 °C and 500 °C, respectively, because the highly porous cathode constructed with the templated SSC reduced the cell concentration polarization and cathode polarization resistance. This study suggests high-performance perovskite ceramic for SOFC was produced viathe template synthesis. [ABSTRACT FROM AUTHOR]

Polymers have attracted considerable attention in the synthesis of zeolites with controllable structures and morphologies (sizes and shapes) because of their three-dimensional networks, abundant functional groups and designed molecular sizes. Polymer networks can function as a space-confinement additive, a mesopore-forming agent, etc., and significantly affect zeolite nucleation and growth processes. This paper highlights the preparation of hollow/core-shell structures, zeolite nanocrystals, zeolite crystals with tunable shapes and mesoporous structure. [ABSTRACT FROM AUTHOR]

In this work we study the structural response of silicalite based MFI type zeolite powder to the presence of water and cations commonly found in sea salts including Na+, K+, Ca2+, and Mg2+. MFI zeolite powder was exposed to different solutions (3.8 wt% TDS (total dissolved solids) seawater (SW), or 1 M NaCl, or 0.05 M KCl), and their effects on the structure of the zeolite powder were characterized. The results obtained from ion adsorption testing and synchrotron X-ray powder diffraction showed that the zeolite powder interacted with water, monovalent and divalent cations, and these interactions altered the crystal dimensions of the zeolite. Most exposures to ions and water led to increases in crystal volumes of <0.1%, but exposure to KCl solution was observed to make the biggest contribution to crystal expansion, at 0.59%, particularly in the a- and c-directions as determined by Rietveld refinement. Upon closer inspection of SW exposed silicalite, a rapid exchange of Na+and K+was observed within 1 h, but after 8 h, these monovalent cations were gradually exchanged with divalent ions. Ca2+was especially observed to adsorb into the zeolite at 8 h. N2adsorption and positron annihilation lifetime spectroscopy (PALS) measurements were made on SW exposed zeolites. PALS showed that the silicalite powder has mesopores (2.6 nm) and micropores (1.0 nm), which are both attributed to intercrystalline spaces. The intrinsic intracrystalline zeolite pore size was measured as 0.33 nm. Both N2adsorption and PALS showed that the relative amount of micropores to total pores decreased with seawater exposure which was attributed to ion adsorption and ion exchange. The mesopore size and number increase due to exposure, and although mesopores represent defects in crystalline zeolites, their expansion on exposure to seawater is important for membrane stability and diffusion properties and warrants further investigation. The intrinsic zeolite pore size was smaller in zeolites exposed to seawater (∼0.29 nm), and the changes observed by PALS lead us to conclude that most of the ion activity observed is attributed to the intercrystalline micropores and mesopores. No other changes were observable by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) due to SW exposure. Results indicate that the interaction between silicalite and the water and ions in SW causes a change in structure and porosity expected to affect diffusion properties of these materials when used as membranes for desalination. [ABSTRACT FROM AUTHOR]

Reverse osmosis (RO) desalination is one of the main technologies for producing fresh water from seawater and other saline water sources. The membrane properties greatly affect the water productivity and energy costs in the reverse osmosis desalinatin processes. Recent years have seen significant research efforts devoted to developing high-performance RO membranes. This article reviews recent activities in the development of RO membranes with improved flux and salt rejection, chlorine tolerance, fouling resistance and thermal stability. In particular, this review mainly focuses on the modification of current polymeric membrane materials, and synthesis and separation performance of new polymer membranes, inorganic membranes and mixed matrix membranes. [ABSTRACT FROM AUTHOR]

A facile synthesis method was developed to form a nanoporous metal oxide layer using poly(furfuryl alcohol) (PFA) as a thermosetting polymer template. A nanoporous Ce0.8Sm0.2O1.9(SDC) layer with high sinterability was prepared on an anode-supported electrolyte film at 900 °C, and used as a sinter-active layer in cell fabrication to improve the interface between the inert electrolyte surface and the cathode layer of a solid oxide fuel cell (SOFC). The resulting saw-like interface improved the maximum powder density of the cell by 51% at 600 °C and 162% at 500 °C compared with that of the unmodified cell. The cell with the saw-like electrolyte–cathode interface exhibited lower electrode polarization resistance than those reported in the literature, and such improvement was much more significant at reduced operating temperatures (400–500 °C). Our study shows that the operating temperature of solid oxide fuel cells can be substantially lowered by simply improving the electrode–electrolyte interfaces. [ABSTRACT FROM AUTHOR]

A new drying-free colloidal casting method was developed for shape forming of ceramics with controllable microstructure. A polymerizable solvent such as furfuryl alcohol (FA) was employed to disperse ceramic particles to form a colloidal ceramic suspension with good fluidity. After casting, the solvent was polymerized into a polymer, resulting in solidification of the colloidal suspension. For the purpose of demonstrating this casting method, three types of ceramic powders (NiO/YSZ, Al2O3and YSZ) were used to fabricate a NiO/YSZ ceramic tube, an Al2O3ceramic part with a hexagonal screw nut shape, and a YSZ thin film. Our study shows that the microstructure (pore size and porosity) of ceramics can be readily tuned by adjusting the amount of FA, and the drying-free casting method offers better controllability over the shape forming of a wide variety of ceramic materials. [ABSTRACT FROM AUTHOR]