Self-discharge in positively charged polypyrrole–cellulose composite electrodes

Self-discharge is one of the most critical issues to address to allow for industrialization of conducting polymer (CP) based electric energy storage devices. The present work investigates the underlying cause of self-discharge in positively charged polypyrrole (PPy), which is one of the most frequently studied CPs for such devices. The analyzed material is a composite of PPy and cellulose from Cladophora sp. algae forming a free standing paper-like material. From the time dependence of the potential decay as well as from independent spectroelectrochemical investigations the decay was attributed to a kinetically limiting Faradaic reaction, intrinsic to the polymer, forming a reactive intermediate that irreversibly reacts with its surroundings in a kinetically non-limiting following reaction. As such, nucleophilic addition of electrolyte nucleophiles is not found to be rate-determining. These results provide insight into the self-discharge phenomenon in p-doped CPs, and information regarding the potential range in which CPs can operate with insignificant self-discharge.     

Synthesis of magnetic hybrid magnetite—gold nanoparticles

Methods for the synthesis of hybrid nanoparticles, consisting in the simultaneous modification of the magnetic core and reduction of gold on the surface using various reagents, were proposed and developed. Depending on synthesis conditions, various hybrid nanoparticles were obtained, namely, hybrid nanoparticles decorated with gold nuclei and hybrid nanoparticles of the core—shell type. The obtained products can be used as promising materials for catalytic and biomedical applications.

     

Synthesis and characterization of sol–gel derived CNSL based hybrid anti-corrosive coatings

Thermally cured cashew nut shell liquid based hybrid coatings have been successfully developed using three step processes of malenization, silane modification and subsequent hydrolysis and condensation with tetra ethyl orthosilicate for corrosion protection of mild steel. The synthesized precursor was then characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy (¹H-NMR, ¹³C-NMR and ²⁹Si-NMR) for structural elucidation. Four different coating formulations were developed on the basis of silane content (5, 10, 15 and 20 %) in the coating and cured with hexabutoxymethylmelamine at 120 °C for 1 h. The completely cured coatings were evaluated for mechanical properties, solvent resistance, chemical resistance, hydrolytic stability and accelerated weathering properties. Scanning electron microscope/energy dispersive spectroscopy was used to analyse the morphological behaviour and elemental distribution of the coating. Results revealed that 20 % silane modification showed better overall properties as compared to other formulations due to formation of more metal–oxygen–silicon covalent bond at metal-coating interface.     

Synthesis and characterization of bimetallic Pt–Fe/polypyrrole–carbon catalyst as DMFC anode catalyst

A novel synthesis route, concerning in situ interfacial polymerization of pyrrole on carbon black and following co-deposition of Pt and Fe on polypyrrole–carbon support, is developed to prepare the bimetallic Pt–Fe/polypyrrole–carbon catalyst. In this synthesis process, ferrous precursor simultaneously functions as an oxidant for the polymerization of pyrrole. The Pt–Fe/polypyrrole–carbon catalyst shows improved catalytic activity towards methanol oxidation compared to commercial Pt/C catalyst, which may be of great potential in direct methanol fuel cells.     

Electrochemical capacitance performance of polypyrrole–titania nanotube hybrid

In this study, the polypyrrole–titania nanotube hybrid has been synthesized for an electrochemical supercapacitor application. The highly ordered and independent titania nanotube array is fabricated by an electro-oxidation of titanium sheet through an electrochemical anodization process in an aqueous solution containing ammonium fluoride, phosphoric acid and ethylene glycol. The polypyrrole–titania nanotube hybrid is then prepared by electrodepositing the conducting polypyrrole into well-aligned titania nanotubes through a normal pulse voltammetry deposition process in an organic acetonitrile solution containing pyrrole monomer and lithium perchlorate. The morphology and microstructure of polypyrrole–titania nanotube hybrid are characterized by scanning electron microscopy, infrared spectroscopy and Raman spectroscopy. The electrochemical capacitance performance is determined by cyclic voltammetry and charge/discharge measurement. It indicates that the polypyrrole film can been uniformly deposited on both surfaces of titania nanotube walls, demonstrating a heterogeneous coaxial nanotube structure. The specific capacitance of polypyrrole–titania nanotube hybrid is determined to be 179?F?g^?1 based on the polypyrrole mass. The specific energy and specific power are 7.8?Wh?kg^?1 and 2.8?kW?kg^?1 at a constant charge/discharge current of 1.85?mA?cm^?2, respectively. The retained specific capacitance still keeps 85% of the initial capacity even after 200 cycle numbers. This result demonstrates the satisfying stability and durability of PPy–TiO₂ nanotube hybrid electrode in a cyclic charge/discharge process. Such a composite electrode material with highly ordered and coaxial nanotube hybrid structure can contribute high energy storage for supercapacitor applications.     

Biodegradable and biocompatible inorganic–organic hybrid materials. I. Synthesis and characterization

The hydroxyl or vinyl end-groups of linear or three-arm star-shaped poly(ε-caprolactone) (PCL) chains have been derivatized into triethoxysilane groups reactive in the sol-gel process. New transparent hybrid materials that combine tetraethylorthosilicate (TEOS) and PCL known for biodegradability and biocompatibility have accordingly been prepared. The sol-gel process is, however, limited by the early vitrification of the reactive system. However, thermal posttreatment can overcome these diffusional and/or kinetic limitations as assessed by a set of analytical methods. The thermal stability of PCL is improved by incorporation into the silica network. Conversely, the thermal stability of the ceramer depends on the effective PCL content. The extent of PCL incorporation into the silica network depends on PCL molecular weight, number, and reactivity of the PCL functional groups. IR spectroscopy has shown that hydrogen bonding occurs between the ester groups of PCL and residual OH groups of the silicate component. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2295–2309, 1997     

Synthesis and characterization of cobalt acrylate–melamine co-crystals

A new co-crystal of tetraaqua acrylato cobalt (II) complex and melamine, [Co(acr)₂(H₂O)₄]·4MA·2DMF (acr = acrylate, MA = melamine, DMF = dimethylformamide), has been synthesized and characterized using IR, UV-Vis, thermogravimetric analysis, and single-crystal X-ray diffraction. The complex contains discrete unities of [Co(acr)₂(H₂O)₄], melamine, and DMF linked by hydrogen bonds. Investigations evidenced that Co(II) has an octahedral stereochemistry and both acrylate ions present unidentate coordination mode. Thermal decomposition occurs in four steps and denotes that melamine is lost at high temperatures, and this indicates a greater stability that may be associated with the presence of hydrogen bonds network.

     

Paper-like free-standing polypyrrole and polypyrrole–LiFePO4 composite films for flexible and bendable rechargeable battery

Highly flexible, paper-like, free-standing polypyrrole and polypyrrole–LiFePO₄ composite films were prepared using the electropolymerization method. The films are soft, lightweight, mechanically robust and highly electrically conductivity. The electrochemical behavior of the free-standing films was examined against lithium counter electrode. The electrochemical performance of the free-standing pure PPy electrode was improved by incorporating the most promising cathode material, LiFePO₄, into the PPy films. The cell with PPy–LiFePO₄ composite film had a higher discharge capacity beyond 50 cycles (80 mA h/g) than that of the cell with pure PPy (60 mA h/g). The free-standing films can be used as electrode materials to satisfy the new market demand for flexible and bendable batteries that are suitable for the various types of design and power needs of soft portable electronic equipment.     

Synthesis and characterization of amantadinium iodoacetatobismuthate,a hybrid compound with mixed iodide–carboxylate anions

The amantadinium iodoacetatobismuthate(III) [C₁₀H₁₅NH₃·(CH₃)₂CO]₂[BiI_3.67(CH₃COO)_1.33] is a new hybrid halometallate with iodide ions partially replaced by oxygen-containing acetates to form stronger interaction between the anionic and cationic substructures. The title compound as well-shaped orange-red crystals was synthesized by a facile reaction in acetone solution in the presence of glacial acetic acid. The crystal structure of the compound consists of the infinite anionic chains [BiI_3.67(CH₃COO)_1.33]^2– and the countercations [C₁₀H₁₅NH₃·(CH₃)₂CO]+; according to the optical absorption data, the test compound is a semiconductor with a band gap of 2.06 eV.     

Synthesis and characterization of sol–gel alumina nanofibers

Abstract Alumina nanofibers of high aspect ratio with surface area of >300 m² g⁻¹ has been prepared successfully in bulk quantities by the sol–gel method. The synthesis parameters including the binary water–alcohol solvent system to aluminium isopropoxide ratio, pH, type of solvent and aging temperature affect the uniformity and formation of nanofibers. It is proposed that alumina nanofibers were formed by the curling of the nanosheets upon condensation after the hydrolysis. The phase evolution of alumina nanofibers from pseudoboehmite to α phase has been shown by XRD and FTIR. ²⁷Al NMR investigations show that the Al atoms are six and four coordinated. The morphology of the alumina nanofibers does not change much as the calcination temperature was increased. In addition, the average pore size increases and the BET surface area decreases as a function of calcination temperature. The thermal behavior of alumina nanofibers was investigated by TGA. Graphical Abstract      

Synthesis and characterization of two new inorganic–organic hybrid cobalt molybdenum(V) phosphates

Two new inorganic–organic hybrid cobalt phosphomolybdates (Hdien)₂[Co(dien)]₂[Co(dien)(H₂O)]₂[CoMo₁₂O₂₄(HPO₄)₂(H₂PO₄)₂(PO₄)₄(OH)₆]?···?5H₂O (1) and (H₂dien)₂[Co(dien)]₂[Co(H₂O)₂]₂[CoMo₁₂O₂₄(HPO₄)₄(PO₄)₄(OH)₆]?···?7H₂O (2) (dien?=?diethylenetriamine), involving molybdenum in the V oxidation state and covalently bonded transition metal complexes, have been prepared under mild hydrothermal conditions and structurally characterized by elemental analyses, IR spectra, TG analyses, and single-crystal X-ray diffraction. Compound 1 exhibits a one-dimensional (1D) chain framework, in which dien molecules adopt two kinds of coordination modes. Compound 2 shows a two-dimensional (2D) layer framework with three types of unusual tunnels. To the best of our knowledge, it is the first time [Co(dien)] units are directly incorporated into 1D and 2D skeletons of reduced molybdenum phosphates. The electrochemical properties of the two compounds were studied via the method of bulk-modified carbon paste electrodes. Furthermore, the magnetic properties of compound 2 are reported.     

Synthesis and characterization of titania/MQ silicone resin hybrid nanocomposite via sol–gel process

Inorganic–organic hybrid materials were prepared via an aqueous sol–gel technique from tetra-n-butyl titanate as the precursor of titania, in the presence of MQ silicone resin. The samples were characterized by FT–IR, UV–Vis, DSC, TGA, SEM and XRD. It was illustrated that the Ti–O–Si covalent bonds had formed in the hybrid nanocomposite which were highly transparent in visible light region, and yet had high absorption in UV light range. The thermal stability of the hybrid materials was gradually improved with the increase of titania content. It was concluded that the hybrid material which particle size was around 50 nm were amorphous when the crystallization of titania was retarded by MQ silicone resin.     

Synthesis and characterization of CeO<Subscript>2</Subscript>–graphene composite

The synthesis and characterization of graphite oxide (GO), graphene (GS), and the composites: GS–CeO₂ and GO–CeO₂ are reported. This synthesis was carried out by mixing aqueous solutions of CeCl₃·7H₂O and GO, which yields the oxidized composite GO–CeO₂. GO–CeO₂ was hydrothermally reduced with ethylene glycol, at 120 °C, yielding the reduced composite GS–CeO₂. GO, GS ,and the composites with CeO₂ were characterized by CHN, TG/DTG, BET, XRD, SEM microscopy, FTIR, and Raman spectroscopy. The estimation of crystallite size of CeO₂ anchored on GO and on GS by Raman, XRD, and SEM agreed very well showing diameters about 5 nm. The role of particles of CeO₂ coating carbon sheets of GO and GS was discussed.     

Synthesis and characterization of two novel organic–inorganic hybrid solids from Keggin ions and metal coordination complexes

Two new hybrid compounds, [Co(4,4′-bpy)₂(H₂O)₄][(4,4′-bpyH₂]₂[CoW₁₂O₄₀]·8H₂O (1) and [Fe(2,2′-bpy)₃]₃[H₂W₁₂O₄₀]·6H₂O (2), (4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine) have been hydrothermally synthesized. These solids were characterized by elemental analysis, thermogravimetric analysis, UV–Vis spectroscopy and X-ray diffraction. The hydrogen-bonding interactions in 1 lead to the formation of a three dimensional network consisting of [CoW₁₂O₄₀]⁶⁻ anionic clusters, [Co(4,4′-bpy)₂(H₂O)₄]²⁺ cations and lattice water molecules, while the discrete Keggin ion [H₂W₁₂O₄₀]⁶⁻ in compound 2 is surrounded by 14 [Fe(2,2′-bpy)₃]²⁺ complexes through CH?O interactions (2.24–2.56 Å).     

Synthesis and properties of zinc–nickel–carbon nanotube composite coatings

Composite electrochemical coatings modified with carbon nanotubes were produced on the basis of the zinc–nickel alloy. The functional properties (friction coefficient, protective capacity) of the composite coatings were studied in comparison with zinc–nickel alloys without a dispersed phase. It was found that, upon inclusion of carbon nanotubes particles into zinc–nickel deposits, their sliding friction coefficient decreases by a factor of 1.3–1.4 and the range of passive-state potentials becomes two times wider.     

Synthesis and characterization of hollow Si–SiC composite nanospheres from hollow SiO2/C nanospheres

Journal of Sol-Gel Science and Technology - Hollow SiO2 nanospheres were fabricated by a modified Stöber method. Hollow Si–SiC composite nanospheres were firstly prepared by reducing the...     

Synthesis and characterization of a novel organic–inorganic hybrid supramolecular recognition material and its selective adsorption for cesium

To separate Cs(I) from highly active liquid waste, a macroporous silica-based 25, 27-bis(iso-propyloxy)calix[4]arene-26,28-crown-6 (BiPCalix[4]C6) supramolecular recognition material, BiPCalix[4]C6/SiO₂–P, was synthesized and characterized by SEM, FT-IR, and TG-DSC. The adsorption properties of BiPCalix[4]C6/SiO₂–P and a macroporous polymer-based supramolecular recognition composite, BiPCalix[4]C6/XAD-7, were compared. It was found that BiPCalix[4]C6/SiO₂–P exhibited better adsorption ability and faster adsorption dynamics than BiPCalix[4]C6/XAD-7. The adsorption isotherm of Cs(I) onto BiPCalix[4]C6/SiO₂–P was studied at 298 K and it was well described by Langmuir isotherm model. The complex composition between BiPCalix[4]C6/SiO₂–P and Cs(I) was determined as 1:1 type by investigating the effect of the concentrations of BiPCalix[4]C6, Cs(I), and H⁺ on the adsorption. Meanwhile, the selectivity of BiPCalix[4]C6/SiO₂–P towards Na(I), K(I), Rb(I), Cs(I), Sr(II), Ba(II), Ru(III), Mo(VI), La(III), and Y(III) was investigated.     

Synthesis and characterization of poly（methyl methacrylate-co-polyhedral oligomeric silsesquioxane） hybrid nanocomposites

A novel poly(methyl methacrylate-co-polyhedral oligomeric silsesquioxane) hybrid nanocomposite was synthesized by free radical polymerization and characterized by ~1H NMR,~(29)Si NMR,and TGA technologies.Compared with PMMA homopolymer, the nanocomposite has better thermal stability.