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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]