Fabrication of Swellable Organic-Inorganic Hybrid Polymers for CO2-Assisted Hydration of Propylene Epoxide.

Swelling is a very common phenomenon in organic substances. However, the swelling behaviors of inorganic substances had rarely been reported. In this study, a new type of swellable organic-inorganic hybrid polymer (PIL@CHT) was designed and successfully synthesized through free-radical copolymerization of polymerizable phosphonium ionic liquid monomer and vinyl-functionalized hydrotalcite (CHT). The swelling behaviors of PIL@CHT in various solvents with a wide range of Hansen solubility parameters (δT) were investigated, and PIL@CHT exhibited excellent swellable capacity in the solvents with δT > 24.4 MPa1/2. The swollen state of the hybrid PIL@CHT in water presented a network structure with a diameter of approximately 8-12 µm, and CHT particles were well dispersed to the channel of PIL. PIL@CHT was applied to catalyze the CO2-assisted hydration of propylene oxide (PO), in which a cascade reaction including the cycloaddition of CO2 and PO and the subsequent hydrolysis of propylene carbonate (PC) occurred. PIL@CHT, combining the active sites of PIL and CHT, synergistically catalyzed this cascade reaction and achieved a high yield (93.0%) and selectivity (98.2%) of 1,2-propanediol (1,2-MPG) under a low H2O/PO ratio of 1.5/1. Moreover, the catalyst could be recycled seven times without any significant loss of catalytic activities and had good substrate generality.

Synthesis of Triblock Polycarboxylate Superplasticizers with Well-Defined Structure and Its Dispersing Performance in ß-Hemihydrate Gypsum.

In this work, a novel AaBAb-type triblock polycarboxylate superplasticizers (PCEs) with well defined molecular structures were designed and synthesized, firstly, by reversible addition-fragmentation chain transfer (RAFT) polymerization, to explore the structure-property relationship PCEs in the ß-hemihydrate gypsum (ß-HH) system. Three PCEs with the same molecular weight and different structure were obtained by changing the feed ratio of the RAFT agent, initiator, and monomer. The effect of the chemical structure of PCEs on their dispersing property and water reduction capacity were assessed in gypsum by measuring the flowability of pastes and the adsorption ability of PCEs on gypsum. Results showed that among three PCEs, when the monomer ratio is 5:1 and a:b = 1:1, PCE-1 exhibited a higher working efficiency, verifying the contribution of regulating structural parameters to the improvement in performances of gypsum paste, because PCE-1 showed the strongest binding capacity with calcium ions due to the relatively equal amount of carboxyl groups at both ends. The AaBAb-type PCEs provide a special advantage over the conventional comb polymer to understand the relation between the structure and property of PCEs, and a direction for further development of PCEs of high performance.

Interlaminar Shear Characteristics of Typical Polyurethane Mixture Pavement.

Polyurethane (PU) can be used as a road material binder, and its mechanical properties, durability, temperature stability, and other road performance metrics are good. However, the interlayer bonding between PU mixtures and asphalt mixtures is poor. The influence of the pavement structure, interlayer treatment scheme, load, and environmental factors on the interlayer shear characteristics of PU mixture composite pavement is analysed. Further, dynamic modulus, Hamburg rutting, accelerated loading, and inclined shear tests were conducted, and the typical PU mixture pavement shear stress was calculated. The interlaminar shear stress of double layer PU mixture pavement, polyurethane-asphalt composite pavement, and typical asphalt pavement were calculated. The results showed that the PU mixture has a low rutting deformation rate, stable mechanical properties, and strong resistance to the coupled action of temperature, water, and loading. The double-layer PU mixture structure has good water-temperature stability and fatigue resistance; however, freeze-thaw and accelerated loading cause great damage to the double-layer PU mixture structure. The residual shear strength ratio after freeze-thaw cycles and accelerated loading is only 50.3% and 35.6%, respectively, while the influence on the double-layer asphalt mixture structure is less. The theoretical calculation results of different pavement structures show that when the temperature increases from 10 °C to 50 °C, the interlaminar shear stress of polyurethane-asphalt composite pavement increases by about 20%. Additionally, the shear stress of pavement PU mixture pavement and typical asphalt pavement is mainly affected by load, and the temperature changes have an obvious effect on the interlayer shear stress of polyurethane-asphalt composite pavement. The calculated maximum shear stress of the three pavement structures with different working conditions is less than the interlaminar shear strength measured by the inclined shear test, indicating that the interlaminar treatment scheme of composite specimens can meet the shear resistance requirements of the three typical pavement structure types.

Hybrid Lithographic Arbitrary Patterning of TiO2 Nanorod Arrays.

In this work, we report a hybrid lithographic method that combines the top-down soft lithography and the bottom-up hydrothermal approach for growing single-crystalline TiO2 nanorod arrays with arbitrary patterns. The arbitrary patterns of TiO2 seeds were obtained through the microcontact printing of the TiO2 seed precursor onto Si substrates using prepatterned poly(dimethylsiloxane) (PDMS) as stamps, followed by a baking process. Afterward, TiO2 nanorod arrays were selectively grown on patterned TiO2 seeds through conventional hydrothermal methods. By controlling the TiO2 seed precursor concentration, the hydrothermal reaction time and temperature and the patterns, the morphology and density of the TiO2 nanorods can be tuned in a controllable manner. Overall, this work provides a new strategy for the low-cost and facile preparation of patterned TiO2 nanorod arrays that has potential applications in micro-nano-optoelectronic devices and other fields.

Unraveling the electronegativity-dominated intermediate adsorption on high-entropy alloy electrocatalysts.

High-entropy alloys have received considerable attention in the field of catalysis due to their exceptional properties. However, few studies hitherto focus on the origin of their outstanding performance and the accurate identification of active centers. Herein, we report a conceptual and experimental approach to overcome the limitations of single-element catalysts by designing a FeCoNiXRu (X: Cu, Cr, and Mn) High-entropy alloys system with various active sites that have different adsorption capacities for multiple intermediates. The electronegativity differences between mixed elements in HEA induce significant charge redistribution and create highly active Co and Ru sites with optimized energy barriers for simultaneously stabilizing OH* and H* intermediates, which greatly enhances the efficiency of water dissociation in alkaline conditions. This work provides an in-depth understanding of the interactions between specific active sites and intermediates, which opens up a fascinating direction for breaking scaling relation issues for multistep reactions.

Synthesis, Characterizations and Applications of Fluoroazaphosphatranes.

Haloazaphosphatranes are the halogenated parents of proazaphosphatranes, also known as Verkade's superbase. While the synthesis of iodo-, bromo- and chloroazaphosphatranes was reported more than thirty years ago by J. G. Verkade, the first synthesis of fluoroazaphosphatranes was only described in 2018 by Stephan et al. Currently, no common and versatile procedure exists to access fluoroazaphosphatranes platform with different structural characteristics. In this report, a new and simple synthesis of this class of compounds was developed based on the nucleophilic attack of the fluoride anion on chloroazaphosphatrane derivatives with good to high isolated yields for the corresponding fluoroazaphosphatranes (70-92%). The scope of the reaction was widened to fluoroazaphosphatranes bearing various substituents and X-ray molecular structures of two of them are reported. The stability of fluoroazaphosphatranes toward nucleophilic solvents like water has been investigated. As they revealed much more robust cations than their chloroazaphosphatrane parents, their chloride salts were tested as organocatalysts for the formation of cyclic carbonates from epoxides and CO2 . Fluoroazaphosphatranes proved to be both efficient and stable catalytic systems for CO2 conversion with catalytic activities similar to those of azaphosphatranes, and no decomposition of the cation was observed at the end of reaction.

Effects of Valence States of Working Cations on the Electrochemical Performance of Sodium Vanadate.

Supercapacitors have received much attention as large-scale energy storage devices for high power density and ultralong cycling life. In this work, sodium vanadate Na0.76V6O15/poly(3,4-ethylenedioxythiophene) (PEDOT) nanocables with deficient bridge oxygen at the interface (denoted Vo••-PNVO) have been tailored for supercapacitors through the in situ polymerization of 3,4-ethylenedioxythiophene and studied using three different electrolytes. Experiments and theoretical calculations reveal that all Na+, Zn2+, and Al3+ ions appear as hydrates in aqueous solutions but insert into the crystal structure as Na+ ions and Zn2+-H2O and Al3+-H2O hydrates, respectively. In comparison with the Zn2+-H2O and Al3+-H2O hydrates, Na+ ions with a smaller radius diffuse more quickly in Vo••-PNVO. Thus, Vo••-PNVO delivers better charge storage capability and stability when an electrolyte with Na+ ions is used. The results strongly suggest that an electrostatic interaction is significant in determining transport properties and storage capacities, rather than hydrate radii or valence states.

A Concentration Gradients Tunable Generator with Adjustable Position of the Acoustically Oscillating Bubbles.

It is essential to control concentration gradients at specific locations for many biochemical experiments. This paper proposes a tunable concentration gradient generator actuated by acoustically oscillating bubbles trapped in the bubble channels using a controllable position based on the gas permeability of polydimethylsiloxane (PDMS). The gradient generator consists of a glass substrate, a PDMS chip, and a piezoelectric transducer. When the trapped bubbles are activated by acoustic waves, the solution near the gas-liquid interface is mixed. The volume of the bubbles and the position of the gas-liquid interface are regulated through the permeability of the PDMS wall. The tunable concentration gradient can be realized by changing the numbers and positions of the bubbles that enable the mixing of fluids in the main channel, and the amplitude of the applied voltage. This new device is easy to fabricate, responsive, and biocompatible, and therefore has great application prospects. In particular, it is suitable for biological research with high requirements for temporal controllability.

Reaction Mechanism of CO2 and Styrene Oxide Catalyzed by Ionic Liquids: A Combined DFT Calculation and Experimental Study.

Bioactive compound 3-aryl-2-oxazolidinone could be synthesized by a green method mixing carbon dioxide, aniline, and ethylene oxide. Our group previously proposed a parallel mechanism for this conversion catalyzed by ionic liquids. Recently, a new study on a similar reaction system of styrene oxide, carbon dioxide, and aniline under the catalysis of K3PO4 gave a different serial mechanism. In order to explore the mechanism of reaction, we conducted a combined theoretical and experimental study on a one-pot conversion of styrene oxide, carbon dioxide, and aniline. In experiments, two isomer products, 3,5-diphenyl-l,3-oxazolidin-2-one and 3,4-diphenyl-l,3-oxazolidin-2-one, were observed. The computational results show that the parallel mechanism is more favored in thermodynamics and in kinetics due to the instability of isocyanate and hardness of its generation. Hence, we believe the previous parallel mechanism is more reasonable under our catalysts and conditions.

Synthesis of Metal Oxide/Carbon Nanofibers via Biostructure Confinement as High-Capacity Anode Materials.

For applications in energy storage and conversion, many metal oxide (MO)/C composite fibers have been synthesized using cellulose as the template. However, MO particles in carbon fibers usually experience anomalous growth to a size of >200 nm, which is detrimental to the overall performance of the composite. In this paper, we report the successful development of a generic approach to synthesize a fiber composite with highly dispersed MO nanoparticles (10-80 nm) via simple swelling, nitrogen doping, and carbonization of the cellulose microfibril. The growth of the MO nanoparticles is confined by the structure of the microfibrils. Density functional theory calculation further reveals that the doped N atoms supply ample nucleation sites for size confinement of the nanoparticles. The encapsulation structure of small MO nanoparticles in the conductive carbon matrix improves their electrochemical performance. For example, the formed SnOx/carbon nanocomposite exhibits high specific capacities of 1011.0 mA h g-1 at 0.5 A g-1 and 581.8 mA h g-1 at 5 A g-1. Moreover, the fiber-like nanocomposite can be combined with carbon nanotubes to form a flexible binder-free electrode with a capacity of ∼10 mA h cm-2, far beyond the commercial level. The process developed in this study offers an alternative approach to sophisticated electrospinning for the synthesis of other fiber-like MO/carbon nanocomposites for versatile applications.

In situ interfacial engineering of nickel tungsten carbide Janus structures for highly efficient overall water splitting.

Regulating chemical bonds to balance the adsorption and disassociation of water molecules on catalyst surfaces is crucial for overall water splitting in alkaline solution. Here we report a facile strategy for designing Ni2W4C-W3C Janus structures with abundant Ni-W metallic bonds on surfaces through interfacial engineering. Inserting Ni atoms into the W3C crystals in reaction progress generates a new Ni2W4C phase, making the inert W atoms in W3C be active sites in Ni2W4C for overall water splitting. The Ni2W4C-W3C/carbon nanofibers (Ni2W4C-W3C/CNFs) require overpotentials of 63 mV to reach 10 mA cm-2 for hydrogen evolution reaction (HER) and 270 mV to reach 30 mA cm-2 for oxygen evolution reaction (OER) in alkaline electrolyte, respectively. When utilized as both cathode and anode in alkaline solution for overall water splitting, cell voltages of 1.55 and 1.87 V are needed to reach 10 and 100 mA cm-2, respectively. Density functional theory (DFT) results indicate that the strong interactions between Ni and W increase the local electronic states of W atoms. The Ni2W4C provides active sites for cleaving H-OH bonds, and the W3C facilitates the combination of Hads intermediates into H2 molecules. The in situ electrochemical-Raman results demonstrate that the strong absorption ability for hydroxyl and water molecules and further demonstrate that W atoms are the real active sites.

Thermal conductivity of V2O5 nanowires and their contact thermal conductance.

Vanadium pentoxide (V2O5)-based composites show outstanding performances as cathode materials in lithium-ion batteries. However, their inferior thermal conductivity restricts the heat dissipation through the cathode electrode. In this study, we measured the thermal conductivity of V2O5 nanowires using the thermal bridge method and found that their thermal conductivity is 3.84 ± 0.38 W m-1 K-1 at T = 300 K. The contact thermal resistance between two nanowires with the same size was measured to be up to 50%-80% of the total thermal resistance in the measured samples, indicating that their contact is the bottleneck for thermal dissipation.

Recent Advances in MEMS-Based Microthrusters.

With the development of micro/nano satellites and formation flying, more advanced spatial propulsion technology is required. In this paper, a review of microthrusters developments that based on micro electromechanical systems (MEMS) technology adopted in microthrusters is summarized. The microthrusters in previous research are classified and summarized according to the types of propellants and the working principles they utilized. The structure and the performance including the thrust, the impulse and the specific impulse of various microthrusters are compared. In addition, the advantages and the disadvantages of these microthrusters presented in the paper are discussed.

Low-Electronegativity Vanadium Substitution in Cobalt Carbide Induced Enhanced Electron Transfer for Efficient Overall Water Splitting.

Developing highly efficient electrocatalysts while revealing the active site and reaction mechanism is essential for electrocatalytic water splitting. To overcome the number and location limitations of defects in the electrocatalyst induced by conventional transition-metal atom (e.g. Fe, Co, and Ni) surface doping, we report a facile strategy of substitution with lower electronegative vanadium in the cobalt carbide, leading to larger amounts of defects in the whole lattice. The self-supported and quantitatively substituted VxCo3-xC (0 ≤ x ≤ 0.80) was one-step synthesized in the electrospun carbon nanofibers (CNFs) through the solid-state reaction. Particularly, the V0.28Co2.72C/CNFs exhibit superior hydrogen evolution reaction and oxygen evolution reaction activity and deliver a current density of 10 mA cm-2 at 1.47 V as the alkaline electrolyzer, which is lower than the values for the Pt/C-Ir/C couple (1.60 V). The operando Raman spectra and density functional theory calculations show that the enhanced electron transfer from V to the orbit of the Co atom makes Co a local negative charge center and leads to a significant increase in efficiency for overall water splitting.

Mechanistic Studies of CO2 Cycloaddition Reaction Catalyzed by Amine-Functionalized Ionic Liquids.

The homogeneous cycloaddition reaction of CO2 and epichlorohydrin catalyzed by amine-functionalized ionic liquid (AFIL) to yield cyclic carbonate is reported in this study. The AFIL has the dual function of ionic liquid and organic base. The experimental study indicates that AFIL can efficiently catalyze the conversion of CO2 and epichlorohydrin to the product 3-chloro-1,2-propylene. The mechanistic study based on DFT calculations reveals that the imidazolium ring in AFIL primarily catalyzes the ring-opening reaction of epichlorohydrin, while the protonated amine group is responsible for stabilizing the Br- anion in the nucleophilic attack. This study provides a deep insight into the catalytic roles of AFIL and also inspires us to design efficient dual function catalysts for CO2 utilization.

Decreasing Ion-Diffusion Barrier Enables Superior Na-Ion Storage by Synergizing Hierarchical Architecture and Lattice Distortion.

Compared with nanosized materials, the long-pathway isolation of the interior part from the electrolyte for bulk electrode materials may result in high ionic diffusion barrier, leading to the poor rate behavior. Either the modification of lattice or the construction of a porous structure is generally effective to decrease the ion-diffusion barrier; however, achieving these multiscaled modulations simultaneously via a facile approach is still a challenge. Herein, we manipulate a bifunctional dopant to prepare micron-sized Na3V2(PO4)3 with extraordinary synergy of hierarchical architecture and lattice distortion. The cations Zn2+ not only substitute partial V3+ to enhance the solid-phase ion diffusivity but also stabilize the lattice structure due to the pillar effect. Additionally, the anions CH3COO- also participate in the reaction to modulate the porous architecture. The analysis results of galvanostatic intermittent titration technique, cyclic voltammetry, and electrochemical impedance spectroscopy demonstrate that the rational design of morphology and structure compounding lowers the ion-diffusion barrier and strengthens the Na+ migration kinetics. When evaluated as the cathode electrode, the optimal composite exhibits improved Na+ ion transport kinetics and superior rate behaviors of 72.2 and 58.7 mAh g-1 at 100 and 200C, respectively.

Interface Engineering V2 O5 Nanofibers for High-Energy and Durable Supercapacitors.

A local electric field is induced to engineer the interface of vanadium pentoxide nanofibers (V2 O5 -NF) to manipulate the charge transport behavior and obtain high-energy and durable supercapacitors. The interface of V2 O5 -NF is modified with oxygen vacancies (Vö) in a one-step polymerization process of polyaniline (PANI). In the charge storage process, the local electric field deriving from the lopsided charge distribution around Vö will provide Coulombic forces to promote the charge transport in the resultant Vö-V2 O5 /PANI nanocable electrode. Furthermore, an ≈7 nm porous PANI coating serves as the external percolated charge transport pathway. As the charge transfer kinetics are synergistically enhanced by the dual modifications, Vö-V2 O5 /PANI-based supercapacitors exhibit an excellent specific capacitance (523 F g-1 ) as well as a long cycling lifespan (110% of capacitance remained after 20 000 cycles). This work paves an effective way to promote the charge transfer kinetics of electrode materials for next-generation energy storage systems.

Tailoring Energy and Power Density through Controlling the Concentration of Oxygen Vacancies in V2O5/PEDOT Nanocable-Based Supercapacitors.

Oxygen vacancies (Vö) play a crucial role in energy storage materials. Oxygen-vacancy-enriched vanadium pentoxide/poly(3,4-ethylenedioxythiophene) (Vö-V2O5/PEDOT) nanocables were prepared through the one-pot oxidative polymerization of PEDOT. PEDOT is used to create tunable concentrations of Vö in the surface layer of V2O5, which has been confirmed by X-ray absorption near edge structure (XANES) analysis and X-ray photoelectron spectroscopy (XPS) measurements. Applied as electrode materials for supercapacitors, the electrochemical performance of Vö-V2O5/PEDOT is improved by the synergistic effects of Vö in V2O5 cores and PEDOT shells with rapid charge transfer and fast Na+ ion diffusion; however, it is compromised subsequently by excessive Vö in consuming more V5+ cations for Faradic reactions. Consequently, the specific capacitance and the energy density of Vö-V2O5/PEDOT nanocables are significantly enhanced when the overall concentration of Vö is 1.3%. The migration of Vö renders an increased capacitance (105% retention) after 10 000 cycles, which is verified and corroborated with density functional theory simulations and XANES analysis. This work provides an illumination for the fabrication of high-performance electrode materials in the energy storage field through Vö.

[Qualitative analysis of compositions of anthraquinone series working solution by gas chromatography-mass spectrometry].

A method for the qualitative analysis of compositions of anthraquinone working solution (WS)/hydrogenated working solution (HWS) by gas chromatography-mass spectrometry (GC-MS) was developed. The composition of ethylanthraquinone (eAQ) WS/HWS was identified by GC-MS. Then the samples of amylanthraquinone (AAQ) WS/HWS were analyzed by GC-MS. Combined with the reaction mechanism, the composition of AAQ WS/HWS was inferred. The list of the degradation as well as the intermediate products in the industrial synthesis of H2O2 in anthraquinone WS was generated, and the information obtained regarding the composition of the anthraquinone WS/HWS was helpful in identifying and removing the unacceptable degradation products.

Swelling Poly(ionic liquid) Supported by Three-Dimensional Wire Mesh for Oil/Water Separation.

A kind of oil/water separation membrane, combining poly(ionic liquid) (PIL) and three-dimensional (3D) wire mesh, was designed and prepared via one-step photopolymerization of an ionic liquid monomer 1,8-triethylene glycoldiyl-3,3'-divinylimidazolium dibromide ([DVIm-(EG)3]Br2) with acrylic acid in the mesh. The composite membrane (PIL@Mesh) had the advantages of anti-oil-adhesion property and high mechanical strength simultaneously. The morphology of PIL@Mesh characterized by scanning electron microscopy (SEM) and Cryo-SEM demonstrated that PIL swelled in water to construct microscale 3D networks. The 3D networks of swelling PIL were capable of forming a hydration layer and endowed PIL@Mesh with superhydrophilicity, which made the membrane to transport water but to intercept oil. PIL@Mesh showed excellent separation efficiency (above 99.9%) for various oil/water mixtures, large water flux (47 L·m-2·s-1), and high intrusion pressure (1.2 kPa). Meanwhile, it performed well in recyclability and corrosion-resistant under harsh conditions, such as acid, alkaline, and salty environments.