Search

In this work, the reducing action of four reducing agents—ascorbic acid, inorganic salt, sodium hydrosulfite and polysaccharide—was investigated. Some reducing agents, in addition to being environmentally friendly, are good substitutes for dangerous chemicals used industrially. Graphene oxide (GO) was synthesized by the modified Hummers method and was reduced with ascorbic acid (RGO-AA), inorganic salt (RGO-SI), sodium hydrosulfite (RGO-HS) and polysaccharide (RGO-PS). The microstructural, morphological, optical, electrochemical and thermal properties of GO, RGO-AA, RGO-SI, RGO-HS and RGO-PS were characterized by x-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy/attenuated total reflectance (FTIR-ATR), x-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM)/energy-dispersive x-ray spectroscopy (EDS), field-emission scanning electron microscopy (FEG-SEM), UV–Vis, zeta potential, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The conclusive results showed that the four agents demonstrated reducing capability. It was observed that the reducing agent derived from inverted sugar (polysaccharide) was the most efficient because it presented a reduction in GO with fewer microstructural defects, a lower number of sheets, and electrochemical and thermal properties superior to the properties obtained from conventional reducing agents. Therefore, with these impressive results obtained with polysaccharide, it was concluded that an effective GO reducing agent was obtained using this green and ecological product, resulting in a reduced graphene oxide (RGO) with few sheets and fewer defects and, consequently, with greater supercapacitor application potential. [ABSTRACT FROM AUTHOR]

As a cheaper alternative to the industrial Pt electrode used in quantum-sensitized solar cells, the electrophoresis process is employed to create the low-cost FTO/PbS cathode. For structural cubic and sizes ranging from 40 nm to 200 nm, structure and morphology were investigated using high-resolution scanning electron microscopy and X-ray diffraction. The conversion efficiency of solar cells is significantly impacted by the calcination temperatures of cathodes at 100 ℃, 150 ℃, 200 ℃, and 300 ℃ under vacuum. The FTO/PbS cathode electrode was therefore calcined at 150 ℃ with a maximum efficiency of 3.938%. This happens as a result of the complete fusion of PbS nanoparticles with crystal at 150 ℃, which reduces resistance and increases electron lifetime compared to other temperature combinations.

In this study, WO3:Co thin films with different percentages of cobalt concentration were deposited by spray pyrolysis on glass substrates at T = 400 °C and annealed at T = 500 °C for 1 h in the furnace. Tungsten oxide thin films with cobalt impurity are deposited by adding the cobalt chloride with different percentages of 0–5–10–15–20% and 30% to the initial solution and the effect of Co–doping on structural, morphological, optical, and electrochromic properties were studied. Then, structural, optical, morphology, and electrochemical properties of the films were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), UV-Vis spectroscopy, and cyclic voltammetry (I–V). The X-ray diffraction results of WO3:Co thin films showed that the structure of the thin films before annealing is amorphous. After annealing, the thin films are polycrystalline with monoclinic and hexagonal WO3 phases, and a combined phase of CoWO4 and W17O49 unstable phase. The bandgap was also calculated using the UV-Vis spectrum. Also, the electrochromatic properties of the thin films are analyzed by cyclic voltammetry analysis. The results of the electrochromatic cycles showed that the WO3 sample with a 20% cobalt impurity has a significant color variation. [ABSTRACT FROM AUTHOR]

To improve the performance of lithium-ion batteries, the functional separators were developed by coating water-based polyvinylidene fluoride (PVDF) powder particles solution using polyvinyl alcohol as the binder on both sides of a conventional polypropylene (PP) microporous membrane by means of simple dipping. The electrochemical performance was tested and compared with that of pure PP membrane. It was found that the PVDF powder particles accumulated and scattered on the surface of PP membrane. Many voids existed among the powder particles. The thermal shrinkage percent tested at 130 °C for 1 h was decreased from 59.4% to 12.7%, whereas the electrolyte uptake was increased from 80% to 140%. The separator coated with 10% solid content of PVDF particles exhibited the best electrochemical performance, including the cycling performance and rate capability. The coated PVDF component not only decreased the interface resistance but also increased the ionic conductivity, owing to the high strong affinity of PVDF toward polar solvents and the voids among the PVDF particles to afford the passage for Li-ions. [ABSTRACT FROM AUTHOR]

A new type of semi-IPN gel electrolyte was prepared by thermal polymerization in this article. At first, the crosslinkable PEG200 (MXPEG) was prepared by condensation reaction, then the crosslinkable components were blent with PMMA and heated under vacuum to form polymer blends with semi-IPN fabric. Differential scanning calorimetry and X-ray diffraction spectroscopy were used to investigate the thermal properties and crystalline/amorphous structure of the prepared polymer blends. With semi-IPN fabric, they present amorphous absolutely. For semi-IPN gel electrolyte, the mechanical and the electrochemical properties are varied with the quantity of absorbed liquid electrolyte. Ion-conductivity behavior for semi-IPN gel electrolyte measured by means of AC impedance spectrum showed that the best data was 1.62 × 10−3S cm−1 at room temperature, and Arrhenius-type relationship was obeyed in the temperature dependence of ionic conductivity. In addition, the electrochemical stability window of the semi-IPN gel electrolyte was 4.6 V. All the properties showed that the prepared semi-IPN gel electrolyte was expected to have applications of electrolyte for lithium-ion polymer secondary batteries. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Abstract: Two new Keggin polyoxometalate-based compounds, [Ag4(phnz)6(SiW12O40)] (phnz=phenazine) (1) and [Ag(phnz)1.5][Ag(phnz)(pz)][{Ag2(phnz)(pz)(H2O)}(SiW12O40)] (2) (pz=pyrazine), have been hydrothermally synthesized. Compound 1 is a discrete cluster in which the [SiW12O40]4− (SiW12) anion symmetrically connects two dinuclear Ag2(phnz)3 fragments. All AgI in 1 adopt a trigonal geometry. By introducing the secondary bridging ligand “pz” into the above system, compound 2 was obtained. Compound 2 contains three kinds of silver complex subunits: [Ag2(phnz)(pz)(H2O)]2+, [Ag2(phnz)3]2+ and [Ag(phnz)(pz)]+. The first one extends to a wave-like chain with SiW12 anions as bi-dentate suspenders, and the last two are counter cations. Furthermore, AgI ions in 2 exhibit three kinds of coordination modes. Their electrochemistry properties have also been studied. [ABSTRACT FROM AUTHOR]

Abstract: By employing different organic amines as structure-directing agents, two new distinct 3D porous inorganic frameworks based on molybdenum(V) phosphates and MnII, (H2en)2{[Mn(H2O)]2[MnMo12O24(OH)6(H2PO4)2(HPO4)4(PO4)2]}·7H2O (en=ethylenediamine) (1) and (H3dien)2{[Mn(H3O)2][Mn3Mo12O24(OH)6(HPO4)2(PO4)6]}·5H2O (dien=diethylenetriamine) (2), have been hydrothermally synthesized, and characterized by routine physical methods. In compound 1, MnII all adopt octahedral coordination mode and each sandwich cluster Mn[Mo6P4O31]2 (abbreviated as Mn[Mo6P4]2) acts as an octa-dentate ligand linking eight MnII, which result in a 3D inorganic (4, 8)-connected framework with the (46)(410·612·86) topology. Compound 2 shows a 3D (4, 10)-connected framework with the (31·44·61)(34·49·57·617·74·84) topology, in which MnII ions exhibit both tetrahedral and octahedral coordination modes, and each Mn[Mo6P4]2 links ten MnII. Interestingly, there exist channels along the a and b axes in 1, while along the a and c axes in 2. The differences between the two compounds should be ascribed to the distinctions of the organic amines. Primary de-/rehydration behaviors and electrochemistry properties have also been studied for the two compounds. [Copyright &y& Elsevier]

Abstract: Citrate capped gold nanoparticle (AuNP) (∼15nm) array with 20–50nm spaces supported with amino-groups activated boron-doped diamond (BDD) film (AuNPs–BDD) has been fabricated through a self-assembly process. Surface states of BDD were characterized by XPS spectra and the topography of the AuNPs–BDD electrode was monitored with SEM images. The assembly kinetics of gold nanoparticle on the amino-groups activated BDD surface was also studied. Moreover, the basic electrochemical properties of as-grown BDD electrode, gold macroelectrode and AuNPs–BDD electrode were compared. Our result indicates that the AuNPs–BDD electrode shows much lower background current density comparing with gold macroelectrode. For the electrochemical response of , the signal-to-background ratio (S/B) is adjustable by controlling the AuNPs coverage on BDD surface. Furthermore, the electrochemical responses to electrolyte pH dependences for different types of redox couples, and Ru on AuNPs–BDD electrode were also studied. The results suggest that the electron exchange rate between out-sphere type redox ions and AuNPs–BDD electrode is adjustable by changing the electrolyte pH. [Copyright &y& Elsevier]