Effect of Al2O3 nanoparticles on the electrochemical characteristics of P(VDF-HFP)-based polymer electrolyte

Alumina (Al₂O₃) nanoparticles have been used as fillers in the preparation of poly(vinylidenefluoride-co-hexafluorpropylene) (P(VDF-HFP))-based porous polymer electrolyte. The degree of crystallization of polymer film filled with Al₂O₃ nanoparticles decreases with increase of the mass fraction of Al₂O₃ nanoparticles and the amorphous phases of polymer film expand accordingly. The Al₂O₃ nanoparticles play the role of solid plasticizer for polymer matrix. Nevertheless that excessive Al₂O₃ nanoparticles existing in polymer matrix leads to micro-phase separation between polymer matrix and fillers. As a result, both ionic conductivity and lithium ions transference number reduces whereas the activation energy for ions transport increases. When the polymer film is filled with 10% of the mass fraction of Al₂O₃ nanoparticles, polymer electrolyte possesses the ionic conductivity up to 1.95 × 10⁻³ S cm⁻¹ and the lithium ions transference number to 0.73 while the activation energy for ions transport of them falls to 5.6 kJ mol⁻¹. Effect of Al₂O₃ on the electrochemical properties of polymer electrolyte has been investigated in this paper. Analysis of FTIR spectra shows that there is the interaction between Al₂O₃ nanoparticles and polymer chains.     

Effect of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Nanofiller on ion conductivity,transmittance, and glass transition temperature of PEI:LiTFSI:PC:EC polymer electrolytes

In the present study, ion conductivity, optical properties, and glass transition temperatures are characterized for polymer electrolytes composed of poly(ethyleneimine) (PEI), lithium bis(trifluoromethane)sulfonylimide (LiTFSI) salt, propylene carbonate (PC), and ethylene carbonate (EC). It was doped with nanoceramic particles in different ratio (0–15 wt.%) to see the effect of ceramic particles. The salt concentration was fixed as 1.04 mol.kg^?1. Although valuable improvement in ion conductivity could not be achieved due to nano-Al₂O₃ fillers, ion conductivity results are placed between 10^?2 and 10^?4 S/cm. Differential scanning calorimetry (DSC) measurements and optical measurements of all electrolytes were performed between ?80 and 140 °C, in the wavelength range between 400 and 700 nm for sample with 80 μm thickness, respectively. The results showed that transmittance of electrolytes decreased monotonically for increasing Al₂O₃ contents. In particular, its transmittance value at 550 nm where human sight is at its greatest sensitivity went from 100% without nanoparticles to 50% for 15 wt% of Al₂O₃.     

Catalytic cracking of isobutane over HZSM-5, FeHZSM-5 and CrHZSM-5 catalysts with different SiO<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> ratios

Several systems of HZSM-5, FeHZSM-5 and CrHZSM-5 zeolite catalysts with different ratios of SiO₂/Al₂O₃ (25,38,50,80, and 150) were prepared and they were characterized by means of X-ray diffraction (XRD), UV–Vis, NH₃-TPD and BET techniques. The results indicated that, compared with uncalcined HZSM-5 zeolites, the total acid amounts, acidic site density and acidic strength of HZSM-5, FeHZSM-5 and CrHZSM-5 zeolite catalysts obviously decreased, while those of weak acid amounts obviously enhanced with the decrease of SiO₂/Al₂O₃ molar ratio. When the ratio of SiO₂/Al₂O₃ is less than 50, the three systems of HZSM-5, FeHZSM-5 and CrHZSM-5 zeolite catalysts with same ratio of SiO₂/Al₂O₃ gave similar and high isobutane conversions. However, when the ratio of SiO₂/Al₂O₃ was equal to or greater than 80, these three systems of catalysts possessed different altering tendencies of isobutane conversions, thus their isobutene conversions were different. High yields of light olefins were obtained over the FeHZSM-5 and CrHZSM-5 zeolite catalysts with high ratio of SiO₂/Al₂O₃ (≥80). The ratio of SiO₂/Al₂O₃ has large effects on the surface area, and acidic characteristics of HZSM-5, FeHZSM-5 and CrHZSM-5 zeolites catalysts, and thus further affect their catalytic performances for isobutane cracking. That is the nature of SiO₂/Al₂O₃ ratio effect on the catalytic performances.     

Effect of nano-porous Al2O3 on thermal, dielectric and transport properties of the (PEO)9LiTFSI polymer electrolyte system

Thermal, electrical conductivity and dielectric relaxation measurements have been performed on (PEO)₉LiTFSI+10 wt.% Al₂O₃ nano-porous polymer electrolyte system. It is observed that the conductivity enhances substantially due to the presence of the filler particles with different surface groups. The highest enhancement is found for the filler particles with acidic groups followed by basic, neutral, and weakly acidic. The results reveal that the filler particles do not interact directly with poly(ethelene) oxide (PEO) chains indicating that the main chain dynamics governing the ionic transport has not significantly affected due to the filler. The results are consistent with the idea that the conductivity enhancement is due to the creation of additional sites and favourable conduction pathways for ionic transport through Lewis acid-base type interactions between the filler surface groups and the ionic species. This is reflected as an increase in the mobility rather than an increase in the number of charge carriers. A qualitative model has been proposed to explain the results.     

Synthesis of Heterogeneous Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> Nanostructured Anodes with Long-Term Cycle Stability

The 0D-1D Lithium titanate (Li₄Ti₅O₁₂) heterogeneous nanostructures were synthesized through the solvothermal reaction using lithium hydroxide monohydrate (Li(OH)·H₂O) and protonated trititanate (H₂Ti₃O₇) nanowires as the templates in an ethanol/water mixed solvent with subsequent heat treatment. A scanning electron microscope (SEM) and a high resolution transmission electron microscope (HRTEM) were used to reveal that the Li₄Ti₅O₁₂ powders had 0D-1D heterogeneous nanostructures with nanoparticles (0D) on the surface of wires (1D). The composition of the mixed solvents and the volume ratio of ethanol modulated the primary particle size of the Li₄Ti₅O₁₂ nanoparticles. The Li₄Ti₅O₁₂ heterogeneous nanostructures exhibited good capacity retention of 125 mAh/g after 500 cycles at 1C and a superior high-rate performance of 114 mAh/g at 20C.     

Performance of Ni catalyst supported on La-hexaaluminate in CO<Subscript>2</Subscript> reforming of CH<Subscript>4</Subscript>

CO₂ reforming of CH₄ was performed using Ni catalyst supported on La-hexaaluminate which has been an well-known material for high-temperature combustion. La-hexaaluminate was synthesized by sol-gel method at various conditions where different amount of Ni (5–20 wt%) was loaded. Ni/La-hexaaluminate experienced 72 h reaction and its catalytic activity was compared with that of Ni/Al₂O₃, Ni/La-hexaaluminate shows higher reforming activity and resistance to coke deposition compared to the Ni/Al₂O₃ model catalyst. Coke deposition increases proportionally to Ni content. Consequently, Ni(5)/La-hexaaluminate(700) is the most efficient catalyst among various Ni/La-hexaaluminate catalysts regarding the cost of Ni in Ni(X)/La-hexaaluminate catalysts. BET surface area, XRD, EA, TGA and TPO were performed for surface characterization. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Impact of “Super Acid” like filler on the properties of a PEGDME/LiClO4 system

Composite polymer electrolyte based on a new class of filler added to a PEGDME/LiClO₄ model system has been investigated. “Ceramic super acids” used consist of grafted SO₄²⁻ groups on Al₂O₃ particles surface obtained by calcinations route. Conductivity, DSC and FT-IR measurements performed on such composite electrolytes, when compared to the model PEGDME/LiClO₄ electrolyte, showed only slight improvement of their inner characteristics. In contrary, Li/Li symmetric cells study, by means of impedance spectroscopy, has presented a spectacular decrease of the interfacial resistance compare to the model electrolyte. This result opens a new pathway of investigation to master the lithium metal/polymer electrolyte interface.     

Effects of preparation methods for V<Subscript>2</Subscript>O<Subscript>5</Subscript>-TiO<Subscript>2</Subscript> aerogel catalysts on the selective catalytic reduction of NO with NH<Subscript>3</Subscript>

A series of V₂O₅-TiO₂ aerogel catalysts were prepared by the sol-gel method with subsequent supercritical drying with CO₂. The main variables in the sol-gel method were the amounts of V₂O₅ and when the vanadium precursor was introduced. V₂O₅-TiO₂ xerogel and V₂O₅/TiO₂ (P-25) were also prepared for comparison. The V₂O₅-TiO₂ aerogel catalysts showed much higher surface areas and total pore volumes than V₂O₅-TiO₂ xerogel and impregnated V₂O₅/TiO₂ (P-25) catalysts. The catalysts were characterized by N₂ physisorption, X-ray diffraction (XRD), FT-Raman spectroscopy, temperature-programmed reduction with H₂ (H₂-TPR), and temperature-programmed desorption of ammonia (NH₃-TPD). The selective catalytic reduction of NOx with ammonia in the presence of excess O₂ was studied over these catalysts. Among various V₂O₅-TiO₂ catalysts, V₂O₅ supported on aerogel TiO₂ showed a wide temperature window exhibiting high NOx conversions. This superior catalytic activity is closely related to the large amounts of strong acidic sites as well as the surface vanadium species with characteristics such as easy reducibility and monomeric and polymeric vanadia surface species. This work was presented at the 7 ^th Korea-China Workshop on Clean Energy Technology held at Taiyuan, Shanxi, China, June 26–28, 2008.     

Side-by-Side In(OH)<Subscript>3</Subscript> and In<Subscript>2</Subscript>O<Subscript>3</Subscript> Nanotubes: Synthesis and Optical Properties

A simple and mild wet-chemical approach was developed for the synthesis of one-dimensional (1D) In(OH)₃ nanostructures. By calcining the 1D In(OH)₃ nanocrystals in air at 250 °C, 1D In₂O₃ nanocrystals with the same morphology were obtained. TEM results show that both 1D In(OH)₃ and 1D In₂O₃ are composed of uniform nanotube bundles. SAED and XRD patterns indicate that 1D In(OH)₃ and 1D In₂O₃ nanostructures are single crystalline and possess the same bcc crystalline structure as the bulk In(OH)₃ and In₂O₃, respectively. TGA/DTA analyses of the precursor In(OH)₃ and the final product In₂O₃ confirm the existence of CTAB molecules, and its content is about 6%. The optical absorption band edge of 1D In₂O₃ exhibits an evident blueshift with respect to that of the commercial In₂O₃ powders, which is caused by the increasing energy gap resulted from decreasing the grain size. A relatively strong and broad purple-blue emission band centered at 440 nm was observed in the room temperature PL spectrum of 1D In₂O₃ nanotube bundles, which was mainly attributed to the existence of the oxygen vacancies.     

Properties of unsupported MoS<Subscript>2</Subscript> species produced in the preparation of MoS<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> using a sonochemical method

Unsupported MoS₂ particles, which were produced in the preparation of MoS₂/Al₂O₃ using a sonochemical method, were successfully separated from the prepared sample catalyst by adding oleylamine as an agent for dispersing the unsupported particles. The fraction of the unsupported MoS₂, which was estimated based on Mo balance, varied between 0.03 and 0.4, independent of the Mo loading levels investigated (6–54 wt% of Mo). The activity of the unsupported MoS₂ for the hydrodesulfurization of dibenzothiophene was nearly the same as that of the Al₂O₃-supported MoS₂, indicating that the activity of the prepared catalyst was not affected by the presence of the unsupported MoS₂ particles.     

Structure and electrochemical characterization of LiNi<Subscript>0.3</Subscript>Co<Subscript>0.3</Subscript>Mn<Subscript>0.3</Subscript>Fe<Subscript>0.1</Subscript>O<Subscript>2</Subscript> cathode for lithium secondary battery

A lithium insertion material having the composition LiNi_0.3Co_0.3Mn_0.3Fe_0.1O₂ was synthesized by simple sol-gel method. The structural and electrochemical properties of the sample were investigated using X-ray diffraction spectroscopy (XRD) and the galvanostatic charge-discharge method. Rietvelt analysis of the XRD patterns shows that this compound can be classified as α-NaFeO₂ structure type (R3m; a=2.8689(5) Å and 14.296(5) Å in hexagonal setting). Rietvelt fitting shows that a relatively large amount of Fe and Ni ion occupy the Li layer (3a site) and a relatively large amount of Li occupies the transition metal layer (3b site). LiNi_0.3Co_0.3Mn_0.3Fe_0.1O₂ when cycled in the voltage range 4.3–2.8 V gives an initial discharge capacity of 120 mAh/g, and stable cycling performance. LiNi_0.3Co_0.3Mn_0.3Fe_0.1O₂ in the voltage range 2.8–4.5 V has a discharge capacity of 140 mAh/g, and exhibits a significant loss in capacity during cycling. Ex-situ XRD measurements were performed to study the structure changes of the samples after cycling between 2.8–4.3 V and 2.8–4.5 V for 20 cycles. The XRD and electrochemical results suggested that cation mixing in this layered structure oxide could be causing degradation of the cell capacity.     

Preparation and characterization of gel polymer electrolyte based on PVA-K2CO3

ABSTRACT

In this study, electrolyte materials were synthesized by mixing a highly conducting salt (K₂CO₃) with the poly(vinyl alcohol) (PVA) in different proportions (from 10 to 50 wt.%). The synthesized electrolyte was characterized using Fourier transform infrared (FTIR) spectroscopy, field-emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV) for their functional groups, morphology, thermal stability, glass transition temperature (T_g ), ionic conductivity, and potential window, respectively. Characterization results show that the complex formation between PVA and K₂CO₃ salt has been established by FTIR spectroscopic study, which indicates the detailed interaction between PVA and the salts in PVA-K₂CO₃ composites while the amorphous nature of the electrolyte after incorporation of the salts has been confirmed by FESEM analysis. Similarly, TGA and DSC analysis revealed that both decomposition temperature and T_g of the synthesized electrolytes decrease with the addition of K₂CO₃ due to the strong plasticizing effect of the salt. The results confirm that the electrolytes have sufficient thermal stability for supercapacitor operation, as well as an amorphous phase to effectively deliver high ionic conductivity. The highest ionic conductivity of 4.53 × 10^?3 S cm^?1 at 373 K and potential window of 2.7 V was exhibited by PK30 (30 wt.% K₂CO₃), which can be considered as high value for solid-state electrolytes which are superior to those electrolytes from PVA salts earlier reported. The results similarly show that the prepared electrolyte is temperature-dependent as conductivity increase with increase in temperature. Based on these properties, it can be imply that the PVA-K₂CO₃ gel polymer electrolyte (GPE) could be a promising electrolyte candidate for EDLC applications. The results indicate that the PVA-K₂CO₃ as a new electrolyte material has great potential in practical applications of portable energy-storage devices.     

Characterization of (PVDF + LiFePO<Subscript>4</Subscript>) solid polymer electrolyte

LiFePO₄ nanopowders (50 nm) were prepared through a simple hydrothermal process. Poly vinylidene fluoride (PVDF): LiFePO₄ complex membranes as solid polymer electrolytes were characterized. X-ray diffraction (XRD) and differential scanning calorimetric (DSC) studies show a decrease in crystalline size and crystallinity of the polymer PVDF with increasing LiFePO₄ concentration. Scanning electron micrographs show smaller spherical domains in the dry film with increased LiFePO₄ nanopowder content. Impedance measurements suggest that the ionic conductivity of (PVDF + LiFePO₄) increases with increased temperature and lithium powder concentration.     

Maximization of total surface area of Pt-SnO<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst by the Taguchi method

The maximization of the total surface area of Pt-SnO₂/Al₂O₃ catalyst was studied by using the Taguchi method of experimental design. The catalysts were prepared by sol-gel method. The effects of HNO₃, H₂O and aluminum nitrate concentrations and the stirring rate on the total surface area were studied at three levels of each. L₉ orthogonal array leading nine experiments was used in the experimental design. The parameter levels that give maximum total surface area were determined and experimentally verified. In the range of conditions studied it was found that, medium levels of HNO₃ and H₂O concentration and lower levels of aluminum nitrate concentration and stirring rate maximize the total surface area.     

Structural and AC impedance studies on nanocomposite polymer electrolytes based on poly(ε‐caprolactone)

Nanocomposite polymer electrolyte (NCPE) films of [75 wt % poly(ε‐caprolactone) : 25 wt % zinc triflate] + x wt % nanofiller Al₂O₃ (x = 1, 3, 5, 7) were prepared by solution cast technique. Such NCPE films were characterized using Fourier transform infrared and AC impedance spectroscopic techniques. Complexation of polymer with salt and nanofiller was revealed from FTIR analysis. On the other hand, an apparent increase in the number density of charge carriers upto 5 wt % loading of the nanofiller was also confirmed. Furthermore, AC impedance spectroscopic studies have shown that ionic conductivity increases with the addition of Al₂O₃ and reaches a maximum of 2.5 × 10^?5 S cm^?1 at room temperature for 5 wt % loading of nanofiller. The dielectric behavior of all the synthesized samples has also been analyzed and presented. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40524.     

Synergism Between Pt/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and Au/TiO<Subscript>2</Subscript> in the Low Temperature Oxidation of Propene

CO impedes the low temperature (<170 °C) oxidation of C₃H₆ on supported Pt. Supported Au catalysts are very effective in the removal of CO by oxidation, although it has little propene oxidation activity under these conditions. Addition of Au/TiO₂ to Pt/Al₂O₃ either as a physical mixture or as a pre-catalyst removes the CO and lowers the light-off temperature (T ₅₀) for C₃H₆ oxidation compared with Pt catalyst alone by ~54 °C in a feed of 1% CO, 400 ppm C₃H₆, 14% O₂, 2% H₂O.     

Electrochemical studies of electrospun organic/inorganic hybrid nanocomposite fibrous polymer electrolyte for lithium battery

Poly(vinylidene fluoride-co-hexafluoropropylene) P(VdF-co-HFP)/magnesium aluminate (MgAl₂O₄) hybrid fibrous nanocomposite polymer electrolyte membranes were newly prepared by electrospinning method. The as-prepared electrospun pure and nanocomposite fibrous polymer membranes with various MgAl₂O₄ filler contents were characterized by X ray diffraction, differential scanning calorimetry and scanning electron microscopy techniques. The fibrous nanocomposite polymer electrolytes were prepared by soaking the electrospun membranes in 1 M LiPF₆ in EC:DEC (1:1, v/v). The fibrous nanocomposite polymer electrolyte membrane with 5 wt.% of MgAl₂O₄ show high electrolyte uptake, enhanced ionic conductivity is found to be 2.80 × 10⁻³ S cm⁻¹ at room temperature and good electrochemical stability window higher than 4.5 V. Electrochemical performance of commercial celgard 2320, fibrous pure and nanocomposite polymer electrolyte (PE, NCPE) membranes with different MgAl₂O₄ filler content is evaluated in Li/celgard 2320, PE, NCPE/LiCoO₂ CR 2032 coin cells at current density 0.1 C-rate. The NCPE with 5 wt.% of MgAl₂O₄ delivers an initial discharge capacity of 158 mAhg⁻¹ and stable cycle performance compared with the other cells containing celgard 2320 separator and pure membrane.     

Fabrication and properties of crosslinked poly(propylene carbonate maleate) gel polymer electrolyte for lithium‐ion battery

The poly(propylene carbonate maleate) (PPCMA) was synthesized by the terpolymerization of carbon dioxide, propylene oxide, and maleic anhydride. The PPCMA polymer can be readily crosslinked using dicumyl peroxide (DCP) as crosslinking agent and then actived by absorbing liquid electrolyte to fabricate a novel PPCMA gel polymer electrolyte for lithium‐ion battery. The thermal performance, electrolyte uptake, swelling ratio, ionic conductivity, and lithium ion transference number of the crosslinked PPCMA were then investigated. The results show that the T_g and the thermal stability increase, but the absorbing and swelling rates decrease with increasing DCP amount. The ionic conductivity of the PPCMA gel polymer electrolyte firstly increases and then decreases with increasing DCP ratio. The ionic conductivity of the PPCMA gel polymer electrolyte with 1.2 wt % of DCP reaches the maximum value of 8.43 × 10⁻³ S cm⁻¹ at room temperature and 1.42 × 10⁻² S cm⁻¹ at 50°C. The lithium ion transference number of PPCMA gel polymer electrolyte is 0.42. The charge/discharge tests of the Li/PPCMA GPE/LiNi_1/3Co_1/3Mn_1/3O₂ cell were evaluated at a current rate of 0.1C and in voltage range of 2.8–4.2 V at room temperature. The results show that the initial discharge capacity of Li/PPCMA GPE/LiNi_1/3Co_1/3Mn_1/3 O₂ cell is 115.3 mAh g⁻¹. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of ZnGa<Subscript>2</Subscript>O<Subscript>4</Subscript> Hierarchical Nanostructure by Au Catalysts Induced Thermal Evaporation

In this paper, ZnGa₂O₄ hierarchical nanostructures with comb-like morphology are fabricated by a simple two-step chemical vapor deposition (CVD) method: first, the Ga₂O₃ nanowires were synthesized and employed as templates for the growth of ZnGa₂O₄ nanocombs; then, the as-prepared Ga₂O₃ nanowires were reacted with ZnO vapor to form ZnGa₂O₄ nanocombs. Before the reaction, the Au nanoparticles were deposited on the surfaces of Ga₂O₃ nanowires and used as catalysts to control the teeth growth of ZnGa₂O₄ nanocombs. The as-prepared ZnGa₂O₄ nanocombs were highly crystallized with cubic spinel structure. From the photoluminescence (PL) spectrum, a broad band emission in the visible light region was observed of as-prepared ZnGa₂O₄ nanocombs, which make it promising application as an optical material.     

SiO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/SiN<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript> multilayers for photovoltaic and photonic applications

Microstructural, electrical, and optical properties of undoped and Nd³⁺-doped SiO _x /SiN _y multilayers fabricated by reactive radio frequency magnetron co-sputtering have been investigated with regard to thermal treatment. This letter demonstrates the advantages of using SiN _y as the alternating sublayer instead of SiO₂. A high density of silicon nanoclusters of the order 10¹⁹ nc/cm³ is achieved in the SiO _x sublayers. Enhanced conductivity, emission, and absorption are attained at low thermal budget, which are promising for photovoltaic applications. Furthermore, the enhancement of Nd³⁺ emission in these multilayers in comparison with the SiO _x /SiO₂ counterparts offers promising future photonic applications.