Anisotropic Self-Assembly of Asymmetric Mesoporous Hemispheres with Tunable Pore Structures at Liquid-Liquid Interfaces.

Asymmetric materials have attracted tremendous interest because of their intriguing physicochemical properties and promising applications, but endowing them with precisely controlled morphologies and porous structures remains a formidable challenge. Herein, a facile micelle anisotropic self-assembly approach on a droplet surface is demonstrated to fabricate asymmetric carbon hemispheres with a jellyfish-like shape and radial multilocular mesostructure. This facile synthesis follows an interface-energy-mediated nucleation and growth mechanism, which allows easy control of the micellar self-assembly behaviors from isotropic to anisotropic modes. Furthermore, the micelle structure can also be systematically manipulated by selecting different amphiphilic triblock copolymers as a template, resulting in diverse novel asymmetric nanostructures, including eggshell, lotus, jellyfish, and mushroom-shaped architectures. The unique jellyfish-like hemispheres possess large open mesopores (∼14 nm), a high surface area (∼684 m2 g-1), abundant nitrogen dopants (∼6.3 wt %), a core-shell mesostructure and, as a result, manifest excellent sodium-storage performance in both half and full-cell configurations. Overall, our approach provides new insights and inspirations for exploring sophisticated asymmetric nanostructures for many potential applications.

Printing Porous Carbon Aerogels for Low Temperature Supercapacitors.

Maintaining fast charging capability at low temperatures represents a significant challenge for supercapacitors. The performance of conventional porous carbon electrodes often deteriorates quickly with the decrease of temperature due to sluggish ion and charge transport. Here we fabricate a 3D-printed multiscale porous carbon aerogel (3D-MCA) via a unique combination of chemical methods and the direct ink writing technique. 3D-MCA has an open porous structure with a large surface area of ∼1750 m2 g-1. At -70 °C, the symmetric device achieves outstanding capacitance of 148.6 F g-1 at 5 mV s-1. Significantly, it retains a capacitance of 71.4 F g-1 at a high scan rate of 200 mV s-1, which is 6.5 times higher than the non-3D printed MCA. These values rank among the best results reported for low temperature supercapacitors. These impressive results highlight the essential role of open porous structures for preserving capacitive performance at ultralow temperatures.

High Energy Capacitors Based on All Metal-Organic Frameworks Derivatives and Solar-Charging Station Application.

High energy and efficient solar charging stations using electrochemical capacitors (ECs) are a promising portable power source for the future. In this work, two kinds of metal-organic framework (MOF) derivatives, NiO/Co3 O4 microcubes and Fe2 O3 microleaves, are prepared via thermal treatment and assembled into electrochemical capacitors, which deliver a relatively high specific energy density of 46 Wh kg-1 at 690 W kg-1 . In addition, a solar-charging power system consisting of the electrochemical capacitors and monocrystalline silicon plates is fabricated and a motor fan or 25 LEDs for 5 and 30 min, respectively, is powered. This work not only adds two novel materials to the growing categories of MOF-derived advanced materials, but also successfully achieves an efficient solar-ECs system for the first time based on all MOF derivatives, which has a certain reference for developing efficient solar-charge systems.

Achieving Exceptional Volumetric Desalination Capacity Using Compact MoS2 Nanolaminates.

Capacitive deionization (CDI) has emerged as a promising technology for freshwater recovery from low-salinity brackish water. It is still inapplicable in specific scenarios (e.g., households, islands, or offshore platforms) due to too low volumetric adsorption capacities. In this study, a high-density semi-metallic molybdenum disulfide (1T'-MoS2) electrode with compact architecture obtained by restacking of exfoliated nanosheets, which achieve high capacitance up to ≈277.5 F cm-3 under an ultrahigh scan rate of 1000 mV s-1 with a lower charge-transfer resistance and nearly tenfold higher electrochemical active surface area than the 2H-MoS2 electrode, is reported. Furthermore, 1T'-MoS2 electrode demonstrates exceptional volumetric desalination capacity of 65.1 mgNaCl cm-3 in CDI experiments. Ex situ X-ray diffraction (XRD) reveal that the cation storage mechanism with the dynamic expansion of 1T'-MoS2 interlayer to accommodate cations such as Na+, K+, Ca2+, and Mg2+, which in turn enhances the capacity. Theoretical analysis unveils that 1T' phase is thermodynamically preferable over 2H phase, the ion hydration and channel confinement also play critical role in enhancing ion adsorption. Overall, this work provides a new method to design compact 2D-layered nanolaminates with high-volumetric performance for CDI desalination.

Monomicellar assembly to synthesize structured and functional mesoporous carbonaceous nanomaterials.

The large pores of functional mesoporous carbonaceous nanomaterials have broad accessibility, making them efficient substrates for the mass transport of chemicals in biomedical applications, gas separation, catalysis, sensing, and energy storage and conversion. Recently, the assembly of monomicelles has been used to control the nanostructure and mesoporosity of carbonaceous nanomaterials, where the structure-oriented unit is a single micelle made up of block copolymers/surfactants and of precursor species (via hydrogen bonds, Coulombic and/or other noncovalent interactions). Each monomicelle then represents a template for a single mesopore, and multiple monomicelles can be stacked like LEGO blocks. After polymerization of the precursor species (in this case dopamine), carbonization results in the carbonaceous nanomaterial. The micellar size, structure and shape can be easily tuned by altering the synthetic conditions, providing a high degree of control over the structure of the final product, which can therefore be shaped into original nanostructures otherwise difficult to synthesize using conventional templating methods. Here we provide a detailed procedure for the preparation of the monomicelles, the monomicellar assembly into mesostructured polymeric samples and the conversion of polymeric samples to carbonaceous frameworks. We describe the functional characterization of two mesoporous carbonaceous nanomaterials that demonstrate excellent sodium-ion storage performance and oxygen reduction reactivity, respectively. The monomicellar assembly process for the synthesis of the ordered mesoporous polymers requires ~5 h; the synthesis, including subsequent centrifugation, freeze drying and carbonization, requires 2 d, whereas the entire procedure, including the characterization of the nanomaterials, requires ~4 d.

One-dimensionally oriented self-assembly of ordered mesoporous nanofibers featuring tailorable mesophases via kinetic control.

One-dimensional (1D) nanomaterials have sparked widespread research interest owing to their fascinating physicochemical properties, however, the direct self-assembly of 1D porous nanomaterials and control over their porosity still presents a grand challenge. Herein, we report a monomicelle oriented self-assembly approach to fabricate 1D mesoporous nanostructures with uniform diameter, high aspect ratio and ordered mesostructure. This strategy features the introduction of hexamethylenetetramine as a curing agent, which can subtly control the monomicelle self-assembly kinetics, thus enabling formation of high-quality 1D ordered mesostructures. Meanwhile, the micellar structure can be precisely manipulated by changing the reactant stoichiometric ratio, resulting in tailorable mesophases from 3D cubic (Im-3m) to 2D hexagonal (p6mm) symmetries. More interestingly, the resultant mesoporous nanofibers can be assembled into 3D hierarchical cryogels on a large scale. The 1D nanoscale of the mesoporous nanofibers, in combination with small diameter (~65 nm), high aspect ratio (~154), large surface area (~452 m2 g-1), and 3D open mesopores (~6 nm), endows them with excellent performances for sodium ion storage and water purification. Our methodology opens up an exciting way to develop next-generation ordered mesoporous materials for various applications.

Rational Design of LLZO/Polymer Solid Electrolytes for Solid-State Batteries.

Hybrid composite electrolytes incorporate polymer matrixes and garnet filler attract the focus of concern for all-solid-state batteries, which possess high ionic conductivity, superior electrochemical stability, and wide electrochemical window of ceramic electrolyte advantages, and exhibit excellent flexibility and tensile shear strength from polymer electrolyte benefits. Hence, the unique structure design of solid-state electrolytes resolves the existing defects that the use of either single garnet or polymer electrolytes implemented into battery devices. This review summarizes Li7 La3 Zr2 O12 (LLZO)/polymer solid composite electrolytes (SCEs), comprising LLZO/polymer SCEs with various structures and different ratios of LLZO fillers, LLZO/polymer with different kinds of polymers matrix and hybrid lithium-salt, and Li+ transport pathways within the LLZO/polymers SCEs interface. The purpose here is to propose the viewpoints and challenges of LLZO/polymer SCEs to promote the development of next-generation solid electrolytes.

Simultaneous Electrochemical Exfoliation and Covalent Functionalization of MoS2 Membrane for Ion Sieving.

Transition metal dichalcogenide membranes exhibit good antiswelling properties but poor water desalination property. Here, a one-step covalent functionalization of MoS2 nanosheets for membrane fabrication is reported, which is accomplished by simultaneous exfoliating and grafting the lithium-ion-intercalated MoS2 in organic iodide water solution. The lithium intercalation amount in MoS2 is optimized so that the quality of the produced 2D nanosheets is improved with homogeneous size distribution. The lamellar MoS2 membranes are tested in reverse osmosis (RO), and the functionalized MoS2 membrane exhibits rejection rates of >90% and >80% for various dyes (Rhodamine B, Crystal Violet, Acid Fuchsin, Methyl Orange, and Evans Blue) and NaCl, respectively. The excellent ion-sieving performance and good water permeability of the functionalized MoS2 membranes are attributed to the suitable channel widths that are tuned by iodoacetamide. Furthermore, the stability of the functionalized MoS2 membranes in NaCl and dye solutions is also confirmed by RO tests. Molecular dynamics simulation shows that water molecules tend to form a single layer between the amide-functionalized MoS2 layers but a double layer between the ethanol-functionalized MoS2 (MoS2 -ethanol) layers, which indicates that a less packed structure of water between the MoS2 -ethanol layers leads to lower hydrodynamic resistance and higher permeation.

Spiral self-assembly of lamellar micelles into multi-shelled hollow nanospheres with unique chiral architecture.

Functional carbon nanospheres are exceptionally useful, yet controllable synthesis of them with well-defined porosity and complex multi-shelled nanostructure remains challenging. Here, we report a lamellar micelle spiral self-assembly strategy to synthesize multi-shelled mesoporous carbon nanospheres with unique chirality. This synthesis features the introduction of shearing flow to drive the spiral self-assembly, which is different from conventional chiral templating methods. Furthermore, a continuous adjustment in the amphipathicity of surfactants can cause the packing parameter changes, namely, micellar structure transformations, resulting in diverse pore structures from single-porous, to radial orientated, to flower-like, and to multi-shelled configurations. The self-supported spiral architecture of these multi-shelled carbon nanospheres, in combination with their high surface area (~530 m2 g−1), abundant nitrogen content (~6.2 weight %), and plentiful mesopores (~2.5 nm), affords them excellent electrochemical performance for potassium-ion storage. This simple but powerful micelle-directed self-assembly strategy offers inspiration for future nanostructure design of functional materials.

Jump method for optical thin film design.

This paper proposes a method called Jump method for optimization of optical thin films. The method is the combination of local search strategy using modified Coordinate-Wise Algorithm and global search strategy using modified Evolutionary Algorithm. Jump method can evolve the designs of optical thin films for good performances. The design of a dielectric beam splitter and an edge filter as examples is carried out and the results indicate that Jump method is a very robust algorithm for optical thin film designs.

Insight into the Kinetic Influence of Oxygen Vacancies on the WO3 Photoanodes for Solar Water Oxidation.

Improvements to solar water oxidation performance for WO3 photoanodes due to oxygen vacancies have in general been ascribed to thermodynamic effects. Detailed insights into the water oxidation kinetics for WO3 photoanodes with oxygen vacancies are still lacking. Here, our experimental and computational investigations revealed that the water oxidation pathway on WO3 photoanodes with oxygen vacancies is more inclined to follow the four-hole pathway. This finding reasonably explained the common observations of higher faradaic efficiency for oxygen evolution, better stability, and faster kinetics for water oxidation usually achieved on the WO3 photoanodes with oxygen vacancies.

Carbon-incorporated NiO/Co3O4 concave surface microcubes derived from a MOF precursor for overall water splitting.

Carbon-incorporated NiO/Co3O4 concave surface microcubes (denoted as NCMC) are successfully developed from a precursor of Ni3[Co(CN)6]2 for the first time. The NCMC exhibits excellent electrocatalytic activity for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in potassium hydroxide solution, affording a current density of 10 mA cm-2 at 169.5 mV for the HER and 290 mV for the OER, respectively. This communication describes a rational design of MOF-derived mixed metal oxides as electrocatalysts for overall water splitting, promoting the further development of MOF materials in the field of energy conversion.

In†Situ Growth of Zeolitic Imidazolate Framework-67-derived Nanoporous Carbon@K0.5 Mn2 O4 for High-Performance 2.4†V Aqueous Asymmetric Supercapacitors.

Aqueous asymmetric supercapacitors (ASCs) with a wide voltage window can effectively improve energy storage capacity of energy storage devices. Zeolitic imidazolate framework-67 (ZIF-67) was used as a precursor to prepare nanoporous carbon (NC), and K0.5 Mn2 O4 nanosheets were subsequently grown on the NC surface through a facile in situ redox process (denoted as NCMO). The electrode potential window of NCMO was extended to 1.2 V in a three-electrode system and the value of the potential window was higher than that of most reported manganese oxides. To assemble the asymmetric supercapacitor with a high voltage range, the as-prepared NCMO and NC (with a potential window of -1.2-0 V) were used as the positive and negative electrode, respectively. A 2.4 V NCMO//NC aqueous ASC was constructed and displayed a large energy density of 60 Wh kg-1 at a power density of 1200 W kg-1 and excellent rate performance (41 Wh kg-1 even at a specific power density of 12.3 kW kg-1 ) as well as good cycling stability (92.6 % capacitance retention over 10 000 cycles at 10 A g-1 ). This work provides new opportunities for the development of high voltage ASCs with a high energy density for further practical application.