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Abstract: In this study MnO2 nanorodes (MNR) were fabricated on reduced graphene oxide (rGO) sheets using a facile hydrothermal synthesis route. As prepared binder free MNR-rGO electrodes exhibited promising electrochemical performance. A similar approach was employed to prepare V2O5 nanowire (VNW) on rGO electrodes as anodes for supercapacitor applications. The VNW-rGO anode and MNR-rGO cathode were combined to form a novel hybrid supercapacitor. The hybrid supercapacitor exhibited excellent electrochemical performance reflecting the synergistic effect of combining the MNR-rGO electrode and VNW-rGO electrode. This novel hybrid supercapacitor delivered an energy density of ~15Wh/kg with a specific capacitance of 36.9F/g. These results suggest that the binder free flexible MNR-rGO electrode is a promising cathode material for asymmetric supercapacitors and also for hybrid devices, which incorporate metal oxide anodes. [Copyright &y& Elsevier]

Abstract: Carbon nanofibers (CNFs) were fabricated by thermal treatment of electrospun nanofibers obtained from precursor blends of polybenzimidazole (PBI) and Matrimid®. The microcarbon structures of CNFs obtained from PBI, and the 50:50 and 75:25 blends were studied using XRD and Raman spectra. Nitrogen adsorption/desorption measurements revealed that surface area and porosity of CNFs increased with an increase in Matrimid® content. Electrochemical performance of these CNF electrodes was studied for their application in energy storage devices. The CNFs from the PBI/Matrimid® (75:25)-precursor blend showed the lowest electrochemical impedance, and highest specific capacitance (111F/g) and energy and power densities of 24 and 6kW/kg, respectively. Steam activation and annealing further enhanced the performance resulting in a specific capacitance of 126F/g, and energy and power densities of 49 and 7kW/kg, respectively. [Copyright &y& Elsevier]

Thermally sensitive tetramethylammonium oxalate (TMAO) is incorporated as an in situ porogen into freestanding nonwoven nanofibers of polyacrylonitrile (PAN) produced by electrospinning. Supercapacitor electrode materials are prepared by a series of thermal treatments on these fibers, including stabilization followed by a single step carbonization and CO 2 activation. The specific surface areas of the resultant carbon nanofibers (CNFs) are controlled by varying the amounts of TMAO in the precursor fibers. The electrochemical properties of the carbon nanofibers are characterized by cyclic voltammetry and galvanostatic charge–discharge tests. The highest surface area (2663 m 2 g −1 ) and best electrochemical performance are obtained from PAN containing 0.1 wt% of TMAO (T10), which gives a maximum specific capacitance of 140 F g −1 at a scan rate of 10 mV s −1 in comparison to CNFs from PAN alone, which yielded only 90 F g −1 . At a discharge current density of 1 A g −1 , the obtained energy and power densities are 68 Wh kg −1 and 1.7 W kg −1 , respectively, with capacitance retention of 80% after 1000 cycles. [ABSTRACT FROM AUTHOR]

The MIL-53 metal-organic framework (MOF) is known to change reversibly from an open-pore framework (MIL-53-ht) to a closed-pore framework (MIL-53-lt) depending on the temperature, pressure, or guest molecules absorbed. Three frameworks of the additive, MIL-53-as synthesized (MIL-53-as), MIL-53-ht, and MIL-53-lt, were prepared, characterized, and combined with Matrimid® to form mixed-matrix membranes (MMMs) for gas separations. The MIL-53-ht/Matrimid® MMMs exhibited higher values of permeability compared to Matrimid® as well as an increased CO 2 /CH 4 selectivity suggesting that the open-pore MIL-53 framework was maintained in the polymer matrix. In addition to higher permeability values, MIL-53-as/Matrimid® MMMs showed higher selectivity for gas pairs with kinetic diameters differing by ⩾0.5 Å, including H 2 /O 2 , CO 2 /CH 4 , H 2 /CH 4 , and H 2 /N 2 , suggesting the presence of excess benzene dicarboxylic acid molecules within the pores that reduced its diameter enabling the material to discriminate between smaller and larger gases. MIL-53-lt did not retain its closed-pore form in the MMM. Rather, it irreversibly converted to the open-pore form (MIL-53-ht) due to the exchange of water present in the MIL-53 pores with chloroform solvent molecules during membrane casting and to pore penetration and confinement by Matrimid® polymer chains. This finding, that a polymer matrix stabilizes a MOF pore architecture within an MMM, is significant in that the desired selectivity of a MOF-MMM system may be achievable. [ABSTRACT FROM AUTHOR]

Crystals of highly soluble metal-organic polyhedra 18 (MOP-18) were synthesized and used as additives in Matrimid® 5218 to form mixed-matrix membranes. The MOP-18 linker was functionalized with long alkyl chains to help the crystals dissolve in common organic solvents. Scanning electron microscopy images revealed that the MOP-18 molecules do not aggregate into large particles even at loadings as high as 80wt%, and the absence of polymer veins or polymer rigidification at the MOP-18/polymer interface was attributed to the improved dispersion of the MOP-18 molecules in the polymer matrix. The increase in the modulus of the membranes from 1.4GPa for the pure polymer to 2.4GPa upon incorporation of MOP-18 was attributed to the strong affinity of the polymer chains for the alkyl chains of MOP-18. Gas permeation results showed that the membranes became more permeable as the temperature was increased from 35 to 70°C and that CO2 plasticization, which occurred at 35°C and 8bar, was minimized when the membranes were heated to 70°C owing to an increase in the plasticization pressure to 21bar. At 70°C, the H2/CO2 selectivity remained constant when the transmembrane pressure was increased from 3 to 30bar. The permeability and solubility data at high pressure and high temperature showed that the pore, core, and alkyl chains of MOP-18 introduced new sorption sites that significantly affected the gas transport properties of the membranes. The results also demonstrated that the MOP-18/polymer interface was mechanically stable at high pressure. [ABSTRACT FROM AUTHOR]

Vanadium Nitride (VN) is attractive for energy storage due to its high conductivity (1.6 × 106 S/m) and specific capacitance (1350 F/g) but limited to alkaline electrolytes for redox. In contrast, V 2 O 3 is redox active but not very conductive. In these hybrids a mixture of VN and vanadium oxide (V 2 O 3) were encapsulated in electrospun carbon-nanofibers. A combination of VN and V 2 O 3 takes advantage of the high conductivity from VN and the redox activity from V 2 O 3. Additionally, having the vanadium encapsulated within the carbon can help with the stability as the electrolyte will not have direct interaction with the surface. These hybrids were made by in-situ nitridation of the encapsulated V 2 O 5 followed by ex-situ activation with carbon dioxide. The hybrids were characterized by XPS and Raman spectroscopy. Hybrids of VN/V 2 O 3 -CNF showed increased capacitance of 245 Fg−1 with energy and power densities of 70.2 Wh kg−1 and 1751 W kg−1 in ionic liquid electrolyte. The devices showed good cycle stability with ∼90 % retention after 10,000 cycles at a current density of 1 Ag−1. These findings highlight the potential of VN/V 2 O 3 -CNF hybrids as high-performance supercapacitor electrodes. The combination of high conductivity and redox activity, along with encapsulation within CNFs, opens promising avenues for advanced energy storage. [ABSTRACT FROM AUTHOR]

Abstract: Polyacrylonitrile/poly(methyl methacrylate) (PMMA) fibers containing graphene are prepared by the electrospinning method, and hierarchical porous carbon nanofibers (CNFs) are obtained after subsequent heat treatment. The hierarchical porous CNFs have an improved structure and properties because of the increased surface area, unique nanotexture and increased electrical conductivity due to the dispersion of graphene. The carbonized fiber exhibits a high surface area (over 500m2 g−1) as result of the narrow ultramicro- and mesopore size distributions (centered at approximately 0.7 and 3.7nm, respectively), and a broad mesopore size distribution ranging from 10 to 50nm. The hierarchical pore structures are introduced by the evolution of small gas molecules during the decomposition of the PMMA during heat treatment. The highest specific capacitance of the CNFs is 128Fg−1, and the energy densities are 16.0–21.4Whkg−1 in an aqueous solution and 75.0–58.2Whkg−1 in an organic electrolyte over a power density range of 400–20,000Wkg−1. Under constant current charging/discharging at 1mAcm−2 for 100 cycles, the stability of the CNFs in a 6M KOH aqueous electrolyte decreases by ∼17% compared with the initial specific capacitance value. [Copyright &y& Elsevier]

Abstract: A microporous metal-organic framework Cu–4,4′-bipyridine–hexafluorosilicate (Cu–BPY–HFS), having a surface area of 2000m2/g, was combined with Matrimid® polymer to form free standing films. The permeability properties of Cu–BPY–HFS–Matrimid® mixed-matrix membranes were tested for the pure gases H2, N2, O2, CH4, and CO2 and the gas mixtures CO2/CH4, H2/CO2 and CH4/N2. The ideal selectivity of CH4/N2 increased from 0.95 to 1.21, which suggests that Cu–BPY–HFS has a strong affinity towards CH4 and favors its permeation. The higher solubility of CH4 in the membranes leads to higher selectivity for CH4/N2. The enhanced CH4 transport is also apparent in the case of ideal selectivity for CO2/CH4 and H2/CH4. For CH4/N2 gas mixtures, the selectivity increased from 0.95 to 1.7. The Cu–BPY–HFS''s affinity towards CH4, and its large surface area increased the solubility of CH4 in the mixed-matrix membranes, which led to higher selectivity towards CH4. [Copyright &y& Elsevier]

Abstract: Mesoporous benzene silica (MBS) composites were synthesized and their physical properties were investigated. Three different MBS samples were prepared using octadecyltrimethylammonium chloride, vitamin E TPGS, and Pluronic 123 block copolymer as structure directing agents, respectively. The template extracted MBS samples were heat treated to 1000°C under argon to carbonize the benzene rings in the pore walls to form a graphitic structure. These carbon/SiO2 composites were treated with HF to dissolve the SiO2. The materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption. The MBS samples 1–3 had pore sizes of 2.73, 3.35, and 5.52nm, respectively. The carbon materials CBS samples 1–3 prepared in this study were microporous (<1.4nm) with high surface areas in the range of 950–1250m2/g. [Copyright &y& Elsevier]

Abstract: Electrospinning has been used to produce mesoporous metal oxide fibers with diameters in the nanometer to submicron range. The mesoporous metal oxide fibers include TiO2, Ta2O5, TaNbO5 as well as the crystalline Nb2O5 and VTiO2. The structure directing agents Pluronic P-123 [(EO)20–(PO)70–(EO)20] and Brij 76 [C18H37(OCH2OCH2)10OH], were used to generate the mesopores in the fibers. The fibers were characterized by XRD, scanning electron microscopy and surface area analysis. In the case of TiO2 and Ta2O5 the first examples of mesoporous molecular sieve papers were generated. The papers and fibers remain intact even after heating to 900°C. [Copyright &y& Elsevier]

Abstract: Mesoporous SBA-15/polyaniline composites were synthesized and their physical properties were investigated. The polyaniline was polymerized inside the pores of the mesoporous material by a post-synthesis process as well as an in one step process during the preparation of the molecular sieve. These materials were characterized by X-ray diffraction, scanning electron microscopy and nitrogen adsorption. The composite polyaniline/SBA-15 was electrically insulating (dc conductivity ∼10−8 S/cm) and produced proton conductivities of up to 10−2 S/cm when doped with HCl. [Copyright &y& Elsevier]

The process of electrospinning has been applied for the first time in the production of mesoporous molecular sieve fibers. Different organic templates and silica sources were used to reproducibly obtain a high density of SBA-15 and DAM-1 fibers with diameters in the range of a micron to a few hundred nanometers. [Copyright &y& Elsevier]

Although propylene/propane separation remains a challenge for industrial processes, carbon molecular sieve membranes (CMSMs) have the potential to replace traditional separation methods. A high molecular weight crosslinkable polyimide was utilized to fabricate CMSMs, which showed pure gas permeabilities in excess of 400 barrers with propylene/propane selectivities as high as 25. Mixed gas (C 3 H 8 :C 3 H 6 50:50) measurements yielded a propylene permeability of 257 barrers and a selectivity of 20. CMSMs from thermally precrosslinked polymer precursors demonstrated a 98% propylene permeability retention after aging for 20 days under vacuum. Active gas flow conditions resulted in slightly lower permeability retention (92.5%) after 15 days of testing. • Deprotonation of carboxylic acid in DABA improves molecular weight of 6FDA-DABA. • 6FDA-DABA can be completely thermally crosslinked at 450 °C. • Precrosslinked carbon membranes showed a higher graphitic carbon content. • Higher graphitic carbon contents resulted in higher propylene solubility. • Precrosslinked carbon membrane exhibited superior aging resistance. [ABSTRACT FROM AUTHOR]

Abstract: We have developed a novel approach for compatibilizing immiscible polymer blends using metal organic frameworks (MOFs). For the first time we demonstrated that the droplet diameter of the dispersed phase in a 1:1 immiscible polymer blend composed of 6FDA-DAM:DABA [copolymer of 4,4-hexafluoroisopropylidene diphthalic anhydride (6FDA), 2,4,6-trimethyl-1,3-phenylenediamine and 3,5-diaminobenzoic acid (DABA)], and polybenzimidazole (PBI), is dramatically reduced obtaining a uniform microstructure with the incorporation of as low as 5% (w/w) of the zeolitic imidazolate framework-8 (ZIF-8). This indicates a large improvement in the compatibility of the immiscible polymers with the inclusion of ZIF-8. As the ZIF-8 loading was further increased to 10% (w/w), the droplet diameter further decreased resulting in even higher compatibility. The compatibilizing effect can be attributed to a reduction in the interfacial energy of the immiscible polymers due to the interfacial localization of ZIF-8. This MOF based compatibilization of immiscible polymer blends can open up opportunities for the combination of different properties of polymers in membrane-based separations and in more applications. [Copyright &y& Elsevier]

Abstract: Exfoliated graphite nanoplatelet (xGnP) and V2O5 nanotube (VNT) composite electrodes were fabricated and tested as electrodes for supercapacitors. Enhancement of the electrochemical performance of the composite over its component materials was demonstrated using cyclic voltammetry (CV), constant current charge/discharge testing and electrochemical impedance spectroscopy in aqueous and organic electrolytes. The calculated specific capacitance of the composite was 35Fg−1 in the aqueous electrolyte and 226Fg−1 in the organic electrolyte at a scan rate of 10mVs−1 using a three-electrode system. Asymmetric coin cell devices were fabricated using activated carbon cloth as the positive electrode and xGnP–VNT composite as the negative electrode. The energy and power densities in 1M LiTFSI were 28Whkg−1 and 303Wkg−1, respectively, at a discharge current density of 250mAg−1. [Copyright &y& Elsevier]

Abstract: Mixed-matrix membranes were prepared from Matrimid® and mesoporous ZSM-5 nanoparticles containing crystalline ZSM-5. The ideal selectivity for H2/N2 separation increased from 79.6 for pure Matrimid® to 143 at 10% loading, while the selectivity of O2/N2 increased from 6.6 for pure Matrimid® to 10.4 at 20% loading. The ideal H2/CH4 separation factor increased from 83.3 to 169 at 20% loading. The results suggest that the mesopores of the ZSM-5 material provide good contact between the nanoparticles and the polymer, since the polymer chains can penetrate into the mesopores. The micropores of ZSM-5 crystals provide size and shape selectivity. [Copyright &y& Elsevier]

Abstract: Novel proton-conducting membranes comprising polymer/inorganic materials based on linear polyethyleneimine (LPEI)/SiO2 nanocomposites synthesized through sol–gel processing have been prepared. 3-Glycidyloxypropyl-trimethoxysilane (GLYMO) has been used to cross-link the LPEI to afford improved heat resistance. The addition of trifluoromethanesulfonimide (HTFSI) during membrane processing doped the amine groups of LPEI to form immobilized Brønsted acid–base pairs, which provide the hybrid membrane''s proton conductivity. The resulting membranes show a proton conductivity as high as 1×10−2 S/cm at 90°C, 100% relative humidity and 5.6×10−5 S/cm at high temperatures (≥130°C) under anhydrous conditions. The effects of temperature, humidity and mobility of active groups on the conductivity are discussed. [Copyright &y& Elsevier]

Abstract: Tungstosilicate mesoporous materials (WMM) were synthesized using the ionic surfactant cetyltrimethylammonium bromide (C16H33N+(CH3)3Br−, CTMABr) and non-ionic surfactants, including C12H25(OCH2CH2)10OH (Brij 22, C12EO10OH), C16H33(OCH2CH2)10OH (Brij 56, C16EO10OH), and C18H37(OCH2CH2)10OH (Brij 76, C18EO10OH). Using CTMABr, the highest W/Si ratio achieved for the molecular sieve product was 0.03. The proton conductivity ranged from 0.5 to 2.2×10−2 S/cm, where the highest conductivity was observed with the H3PO4 based preparation. Non-ionic surfactants produced materials with a W/Si ratio as high as 0.05 without any dense WO3 impurities. These samples showed thicker pore walls (39Å), higher thermal stability, and higher proton conductivity (4.0×10−2 S/cm). The WMMs were also employed to make a composite membrane with linear polyethyleneimine (PEI)-3-glycidoxypropyl-trimethoxysilane (GLYMO)-bis(trifluoromethanesulfonyl)imide (HTFSI). At 100°C and 100% relative humidity, the composite membrane with 30wt.% calcined (at 500°C) WMM showed the highest conductivity of 6.1×10−2 S/cm. At 130°C and 20% relative humidity, the highest conductivity of 6.4×10−3 S/cm was obtained for the composite membrane with 30wt.% as-synthesized WMM. [Copyright &y& Elsevier]

There is growing interest in new ways to configure titanium dioxide (TiO2) as new applications emerge such as in photovoltaics and catalysis. A method has been developed for the preparation of mesoporous TiO2 fibers using electrostatic deposition. The mesoporous metal oxide fibers were prepared using Pluronic 123 as the template. The fibers contain anatase crystallized in the pore walls which transforms to rutile upon calcination above 800 °C. The electrospun fibers were evaluated for the photodecomposition of phenol and formic acid. [Copyright &y& Elsevier]

Abstract: The electrospinnability of pitch was improved by blending in a solution of polyacrylonitrile (PAN) resulting in the reduction of the average fiber diameter from 2000 to 750nm. The compositions showing good spinnability are proposed within the soluble concentrations in the ternary phase diagram of the PAN–pitch-solvent, which contains lower concentration of the pitch. Activated carbon fibers were derived by stabilization, carbonization and steam activation at 700, 800, 900 and 1000°C of the PAN/pitch electrospun fibers. The Brunauer, Emmett, Teller (BET) specific surface area ranged from 732 to 1877m2/g. [Copyright &y& Elsevier]