共查询到20条相似文献,搜索用时 31 毫秒
1.
Lenka Musilov Ale Mr
ek Vra Kaprkov Antonín Minaík Artur J. M. Valente Eduarda F. G. Azevedo Luis M. P. Veríssimo M. Melia Rodrigo Miguel A. Esteso Ana C. F. Ribeiro 《International journal of molecular sciences》2021,22(4)
Tracer diffusion coefficients obtained from the Taylor dispersion technique at 25.0 °C were measured to study the influence of sodium, ammonium and magnesium salts at 0.01 and 0.1 mol dm−3 on the transport behavior of sodium hyaluronate (NaHy, 0.1%). The selection of these salts was based on their position in Hofmeister series, which describe the specific influence of different ions (cations and anions) on some physicochemical properties of a system that can be interpreted as a salting-in or salting-out effect. In our case, in general, an increase in the ionic strength (i.e., concentrations at 0.01 mol dm−3) led to a significant decrease in the limiting diffusion coefficient of the NaHy 0.1%, indicating, in those circumstances, the presence of salting-in effects. However, the opposite effect (salting-out) was verified with the increase in concentration of some salts, mainly for NH4SCN at 0.1 mol dm−3. In this particular salt, the cation is weakly hydrated and, consequently, its presence does not favor interactions between NaHy and water molecules, promoting, in those circumstances, less resistance to the movement of NaHy and thus to the increase of its diffusion (19%). These data, complemented by viscosity measurements, permit us to have a better understanding about the effect of these salts on the transport behaviour of NaHy. 相似文献
2.
Ana C.F. Ribeiro Artur J.M. Valente Damien O. Costa Rui F.P. Pereira Miguel A. Esteso 《Electrochimica acta》2010,55(15):4483-4487
Mutual diffusion coefficients (interdiffusion coefficients) and molar electrical conductivities have been measured for cobalt chloride aqueous solutions in the absence and the presence of saccharose at different concentrations (from 0.01 to 0.3 mol dm−3) and 298.15 K. The diffusion coefficients were measured by using the conductimetric method. For these aqueous solutions, limiting molar conductivity values have been calculated. The value of λ0(Co2+) = 105.36 × 10−4 S m2 mol−1, obtained at 298.15 K in pure water solution, agrees well with that reported in the literature. The Nernst diffusion coefficient values derived from diffusion (1.301 × 10−9 m2 s−1) and from conductance (1.295 × 10−9 m2 s−1) are also in good agreement.The dependence of diffusion coefficients and electrical conductivity of CoCl2 on the concentration of saccharose is discussed by considering the effect of the carbohydrate on the electrolyte dehydration, as well as on the ion-pairs and complexes (CoCl2-saccharose and ions-saccharose) formation. 相似文献
3.
The present study reveals the formation of porous anodic films on titanium at an increased growth rate in hot phosphate/glycerol electrolyte by reducing the water content. A porous titanium oxide film of 12 μm thickness, with a relatively low content of phosphorus species, is developed after anodizing at 5 V for 3.6 ks in 0.6 mol dm−3 K2HPO4 + 0.2 mol dm−3 K3PO4/glycerol electrolyte containing only 0.04% water at 433 K. The growth efficiency is reduced by increasing the formation voltage to 20 V, due to formation of crystalline oxide, which induces gas generation during anodizing. The film formed at 20 V consists of two layers, with an increased concentration of phosphorus species in the inner layer. The outer layer, comprising approximately 25% of the film thickness, is developed at low formation voltages, of less than 10 V, during the initial anodizing at a constant current density of 250 A m−2. The pore diameter is not significantly dependent upon the formation voltage, being ∼10 nm. 相似文献
4.
A gel polymer electrolyte based on poly(acrylonitrile-co-styrene) as polymer matrix and N-methyl pyridine iodide salt as I− source was prepared. Controlling the concentration of polymer matrix of poly(acrylonitrile-co-styrene) at 17.5 wt.%, mixing the binary organic solvents mixture ethylene carbonate and propylene carbonate with 6:4 (w/w), and the concentration of N-methyl pyridine iodide and iodine with 0.5 and 0.05 M, respectively, the gel polymer electrolyte attains the maximum ionic conductivity (at 30 °C) of 4.63 mS cm−1. Based on the gel polymer electrolyte, a quasi-solid state dye-sensitized solar cell was fabricated and its overall energy conversion efficiency of light-to-electricity of 3.10% was achieved under irradiation of 100 mW cm−2. 相似文献
5.
Seok Kim 《Electrochimica acta》2009,54(14):3775-1117
The effects of room-temperature molten salt addition on the micro-structure and electrochemical properties of composite electrolytes (CEs) based on poly(ethylene oxide) (PEO)/ethylene carbonate (EC)/LiBF4 were studied. Additional salt, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4), was found to influence the crystalline structure and heterogeneous morphology, resulting in changes to the ionic conductivity of the CE. The CE containing 0.2 mol of EMIBF4 showed a small crystallinity, 27.9%. These CEs showed the highest ion conductivity, 3.1 × 10−4 S/cm, five times higher than that of the pristine PEO/EC/LiBF4. This enhanced conductivity originated from the decreased crystallinity and improved ion transference due to a Lewis acid-base interaction. The CE containing 0.3 mol of EMIBF4 showed decreased conductivity due to the lower mobility, reflecting the high viscosity of the molten salt. 相似文献
6.
Hyperbranched network-based gel copolymer electrolytes are synthesized by in situ free radical polymerization. This research is separated into two parts: the first is an investigation of modified bismaleimide oligomer (MBMI) as a free volume additive, and the second investigates the salt concentration effect on high power application. A polymer electrolyte with MBMI additive provided more free volume space, and the ionic conductivity of gel copolymer electrolytes was measured as a function of the salt concentration of lithium hexafluorophosphate (LiPF6). The highest ionic conductivity and the lowest activation energy of hyperbranched-network gel copolymer electrolytes were determined to be 7.72 × 10−3 S/cm at 23 °C and 5.41 kJ/mol, respectively. Furthermore, the MBMI additive and the optimal concentration of lithium salt increased the free space for carrier ions and contributed to increasing capacity and working voltage at a high rate discharge (8C). The reliability and cycling ability of lithium polymer batteries are as good as lithium ion batteries for potential electric vehicle (EV) application. 相似文献
7.
Charge and discharge behavior of a graphite electrode for rechargeable lithium-ion batteries was successfully improved by pretreatment of graphite powders with A2CO3 (A = Li, Na, and K) aqueous solutions. In the process of the pretreatment, graphite powders were simply dispersed in the aqueous solutions, and then filtered and dried to modify the surface of graphite powder with solid alkali carbonate. With the optimum concentration of each carbonate, 1 wt.% Li2CO3, 5 wt.% Na2CO3, and 1 wt.% K2CO3, the irreversible reaction at the initial cycle was suppressed by the pretreatment which was capable of modifying the solid electrolyte interphase formed on the graphite electrode surface. Furthermore, the rate capability was improved by the surface modification, that is, the reversible discharge capacities at 175 mA g−1 increased with adequate capacity retention in a 1 mol dm−3 LiClO4 ethylene carbonate:diethyl carbonate electrolyte solution because of the kinetics enhancement of lithium-ion transfer at the interface. 相似文献
8.
Thidarat Wongsawa Niti Sunsandee Ura Pancharoen Anchaleeporn Waritswat Lothongkum 《Chemical Engineering Research and Design》2014
Hollow fiber supported liquid membrane (HFSLM) is a favorable technique for the pertraction of metal ions, especially at very low metal concentration. In this work, the pertraction of silver ions from acidic pharmaceutical wastewater via HFSLM was investigated. Pharmaceutical wastewater containing 30 mg/dm3 of silver ions and 120 mg/dm3 of ferric ions was subjected to HFSLM as a feed solution. LIX 84-I dissolved in organic solvent together with Na2S2O3·5H2O solution was selected for use as a liquid membrane and a receiving solution, respectively. The influence of ferric ions on the pertraction of silver ions was studied firstly using wastewater with normal ferric ion concentration and secondly using wastewater with ferric ion precipitation by phosphoric acid solution. The highest pertraction of silver ions was achieved by using 0.1 M of LIX 84-I and 0.5 M of Na2S2O3·5H2O solution at pH of feed and receiving solutions of 3.5 and 2. The flow rates of feed and receiving solutions were 0.2 dm3/min. 0.6 mg/dm3 of silver ions that remained in the wastewater was below the mandatory discharge limit. No effect of normal ferric ion concentration in the wastewater on silver ion pertraction was observed. The crucial parameters were defined to confirm the efficiency and reliability of the system. Finally, the controlling transport regime of silver ion pertraction across HFSLM was determined by the diffusion flux and reaction flux models. 相似文献
9.
Yuta IbusukiHajime Kunigo Yoshihiro Hirata Soichiro SameshimaNaoki Matsunaga 《Journal of the European Ceramic Society》2011,31(14):2663-2669
Fuel Cell performance was measured at 792-1095 K for Ni-GDC (Gd-doped ceria) anode-supported GDC film (60 μm thickness) with a (La0.8Sr0.2)(Co0.8Fe0.2)O3 cathode using H2 fuel containing 3 vol% H2O. A maximum power density, 436 mW/cm2, was obtained at 1095 K. The electrical conductivity of GDC electrolyte in N2 atmosphere of 10−15-100 Pa oxygen partial pressures (Po2) at 773-1073 K was independent of Po2, which indicated the diffusion of oxide ions. The conductivity of GDC in H2O/H2 atmosphere increased because of the further formation of electrons due to the dissociation of hydrogen in GDC (H2 → 2H+ + 2e−). The hole conductivity was observed at 873 K in Po2 = 100-104 Pa. The key factors in increasing power density are the increase of open circuit voltage and the suppression of H2 fuel dissolution in GDC electrolyte. These are controlled by the cathode material and Gd-dopant composition. 相似文献
10.
We report diffusion rates and equilibrium concentrations of water in a polyelectrolyte SPEES/PES film using ATR/FTIR spectroscopy. The data for water obtained by fitting spectral intensities to a dual mode diffusion model in the presence of different counter ions (at 0.2 mol dm−3) follow the order Li+>Cs+>Na+>Ca2+>K+. Diffusion is progressively slower for higher concentrations of NaCl (0.2-0.85 mol dm−3) and the NO3− counter anion leads to a faster diffusion rate than for Cl− at the same concentration. Both water uptake and diffusion rates are broadly consistent with expectations based on the differential degrees of swelling, caused by changes in the SO3−/SO3− interpolymer chain repulsive forces leading to a decrease in volume diffusion compared with the value for pure water. Direct spectral measurements of the degree of swelling confirm that the process does occur, although the order of the swelling amounts does not map directly onto that of the diffusion rates. This is probably because the interfacial dissociation processes are hydration dependent. 相似文献
11.
The electrodeposition of tin at a (0.28 cm2) copper surface from 0.014 mol dm−3 SnSO4 and 12.5 vol.% methanesulfonic acid (MSA 1.93 mol dm−3) at 296 K was studied. Hydroquinone concentrations of 0.005, 0.05 and 0.5 mol dm−3 (corresponding to a molar concentration ratio of hydroquinone to stannous ions of 0.36, 3.6 and 36, respectively) were used. Cyclic and linear sweep voltammetry served to characterise the electrochemical behaviour of tin deposition and stripping. The effects of potential sweep rate and electrode rotation speed on the voltammetry were studied. The stability of the electrolyte with storage time was quantified by changes in the limiting current density for tin deposition at a smooth rotating disc electrode and the peak current density at a static disc electrode. The influence of hydroquinone on mass transport controlled tin deposition and suppression of hydrogen evolution was evaluated. 相似文献
12.
Zonghai Chen 《Electrochimica acta》2006,51(16):3322-3326
LiPF6/LiBOB blend salt-based electrolytes were investigated as potential candidates for high-power lithium-ion batteries, especially for transportation applications. It was demonstrated that both the power capability and the cycling performance of the lithium-ion cells could be attenuated by controlling the concentration of LiBOB in blend salt electrolytes. The power capability of the lithium-ion cells decreases with the concentration of LiBOB, while the capacity retention of the cells at 55 °C increases with the LiBOB concentration. When electrolytes with no more than 0.1 M LiBOB was used, the MCMB/LiMn1/3Ni1/3Co1/3O2 cells have excellent capacity retention at 55 °C, while their impedance meets the requirement set by the FreedomCar Partnership. The similar performance improvement on the MCMB/LiMn2O4 cells was also observed with the blend salt electrolyte. 相似文献
13.
A systematic investigation of the influence of Ti/[IrO2-Nb2O5] electrode composition ([IrO2]=40, 45 and 50 mol%) on electrochemical ozone production (EOP), was conducted in 3.0 mol dm−3 H2SO4 in the presence and absence of 0.03 mol dm−3 KPF6. “In situ” characterisation revealed all oxide layer presented similar structures, except for the 50 mol% IrO2 nominal composition which showed a higher porosity/roughness. The introduction of KPF6 in the electrolyte resulted in an inhibition of the oxygen evolution reaction (OER) at high current densities, improving ozone generation efficiency at i > 0.4 A cm−2, while reducing overpotential for OER. When normalised for the area, the ozone current efficiency presented a good performance of the system. However, improvement of the electrode service life is necessary in order to support the drastic conditions observed during EOP. 相似文献
14.
In this study, we prepare a kind of solid polymer electrolyte (SPE) based on N-ethyl-N′-methyl imidazolium tetrafluoroborate (EMIBF4), LiBF4 and poly(vinylidene difluoride-co-hexafluoropropylene) [P(VdF-HFP)] copolymer. The resultant SPE displays high thermal stability above 300 °C and high room temperature ionic conductivity near to 10−3 S cm−1. Its electrochemical properties are improved with incorporation of a zwitterionic salt 1-(1-methyl-3-imidazolium)propane-3-sulfonate (MIm3S). When the SPE contains 1.0 wt% of the MIm3S, it has a high ionic conductivity of 1.57 × 10−3 S cm−1 at room temperature, the maximum lithium ions transference number of 0.36 and the minimum apparent activation energy for ions transportation of 30.9 kJ mol−1. The charge-discharge performance of a Li4Ti5O12/SPE/LiCoO2 cell indicates the potential application of the as-prepared SPE in lithium ion batteries. 相似文献
15.
A gel polymer electrolyte based on the blend of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and fully cyanoethylated cellulose derivative (DH-4-CN) was prepared and characterized. Thermal, mechanical, swelling, liquid electrolyte retention and electrochemical properties, as well as microstructures of the prepared polymer electrolytes, were investigated using thermogravimetric analysis, electrochemical impedance spectroscopy, linear sweep voltammetry, and scanning electron microscopy. The results showed that the addition of DH-4-CN could obviously improve the conductivity of PVDF-HFP based electrolyte. The maximum ionic conductivity of 4.36 mS cm−1 at 20 °C can be obtained for PVDF-HFP/DH-4-CN 14:1 in the presence of 1 M LiPF6 in EC and DMC (1:1, w/w). The dry blend membranes exhibit excellent thermal behavior. All the blend electrolytes are electrochemically stable up to about 4.8 V vs. Li/Li+ for all compositions. The results reveal that the composite polymer electrolyte qualifies as a potential application in lithium-ion battery. 相似文献
16.
Organic-inorganic hybrid electrolytes based on di-ureasil backbone structures by reacting poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) bis(2-aminopropyl ether) (ED2000) with 3-(triethoxysilyl)propyl isocyanate (ICPTES), followed by co-condensation with methoxy(polyethylenoxy)propyl trimethoxysilane (MPEOP) in the presence of LiClO4 were prepared and characterized by a variety of techniques. The hybrid electrolytes showed good resistance to crystallization and excellent conductivity for use in lithium-ion batteries, as determined by differential scanning calorimetry (DSC) and impedance measurements, respectively. The temperature dependence of the ionic conductivity exhibited a VTF (Vogel-Tamman-Fulcher)-like behavior for all the compositions studied and a maximum ionic conductivity value of 6.9 × 10−5 S cm−1, a relatively high value for solid polymer electrolytes, was achieved at 30 °C for the hybrid electrolyte with a [O]/[Li] ratio of 16. A microscopic view of the dynamic behavior of the polymer chains (13C) and the ionic species (7Li) was provided by the 1H and 7Li line widths measured from 2D 1H-13C WISE (Wideline Separation) and variable temperature 7Li static NMR, respectively, to elucidate the influence of the mobility of the polymer chains and the charge carriers on the observed ionic conductivity. The present salt-free hybrid electrolyte after plasticization with 1 M LiClO4 in EC/PC solution exhibited a swelling ratio of 275% and reached an ionic conductivity value up to 8.3 × 10−3 S cm−1 at 30 °C, which make it a good candidate for the further development of advanced rechargeable lithium-ion batteries. 相似文献
17.
Chien-Ping Tien 《Electrochimica acta》2008,53(13):4505-4511
Using a gel electrolyte for electric double layer capacitors usually encountered a drawback of poor contact between the electrolyte and the electrode surface. A gel electrolyte consisting of poly(ethylene oxide) crosslinked with poly(propylene oxide) as a host, propylene carbonate (PC) as a plasticizer, and LiClO4 as a electrolytic salt was synthesized for double layer capacitors. Diglycidyl ether of bisphenol-A was blended with the polymer precursors to enhance the mechanical properties and increase the internal free volume. This gel electrolyte showed an ionic conductivity as high as 2 × 10−3 S cm−1 at 25 °C and was electrochemically stable over a wide potential range (ca. 5 V). By sandwiching this gel-electrolyte film with two activated carbon cloth electrodes (1100 m2 g−1 in surface area), we obtained a capacitor with a specific capacitance of 86 F g−1 discharged at 0.5 mA cm−2, while the capacitance was 82 F g−1 for a capacitor equipped with a liquid electrolyte of 1 M LiClO4/PC. The capacitance decrease with the current density was less significant for the gel-electrolyte capacitor. We found that the less restricted ion diffusion near the electrolyte/electrode interface led to the smaller overall resistance of the gel-electrolyte capacitor. The high performance of the gel-electrolyte capacitor has demonstrated that the developed polymer network not only facilitated ion motion in the electrolyte bulk phase but also gave an intimate contact with the carbon surface. The side chains of the polymer in the amorphous phase could stretch across the boundary layer at the electrolyte/electrode interface to come into contact with the carbon surface, thus improving transport of Li+ ions by the segmental mobility in polymer. 相似文献
18.
Xiao-Guang Sun 《Electrochimica acta》2005,50(5):1139-1147
Comb-shaped single ion conductors have been synthesized by (1) sulfonation of small molecule chloroethyleneglycols, which, after ion exchange to the Li+ salt were then converted to the acrylate by reaction with acryloyl chloride and copolymerized with polyethylene glycol monomethyl ether acrylate (Mn = 454, n = 8) (PAE8-co-E3SO3Li); (2) sulfonation of chloride end groups grafted on to prepolymers of polyacrylate ethers (PAE8-g-EnSO3Li, n = 2, 3). The highest conductivity at 25 °C of 2.0 × 10−7 S cm−1 was obtained for the PAE8-co-E3SO3Li with a salt concentration of EO/Li = 40. The conductivity of PAE8-g-E3SO3Li is lower than that of PAE8-co-E3SO3Li at similar salt concentrations, which is related to the incomplete sulfonation of the grafted polymer that leads to a lower concentration of Li+. The addition of 50 wt.% of plasticizer, PC/EMC (1/1, v/v), to PAE8-g-E2SO3Li increases the ambient conductivity by three orders of magnitude, which is due to the increased ion mobility in a micro-liquid environment and an increase concentration of free ions as a result of the higher dielectric constant of the solvent. A symmetrical Li/Li cell with an electrolyte membrane consisting of 75 wt.% PC/EMC (1/1, v/v) was cycled at a current density of 100 μA cm−2 at 85 °C. The cycling profile showed no concentration polarization after a break-in period during the first few cycles, which was apparently due to reaction of the solvent at the lithium metal surface that reacted with lithium metal to form a stable SEI layer. 相似文献
19.
The characteristics of a divided, industrial scale electrochemical reactor with five bipolar electrodes (each having a projected area of 0.72 m2) were examined in terms of mass transport, pressure drop and flow dispersion. Global mass transport data were obtained by monitoring the (first order) concentration decay of dissolved bromine (which was generated in situ by constant current electrolysis of a 1 mol dm−3 NaBr(aq)). The global mass transport properties have been compared with those reported in the literature for other electrochemical reactors. The pressure drop over the reactor was calculated as a function of the mean electrolyte flow velocity and flow dispersion experiments showed the existence of slow and fast phases, two-phase flow being observed at lower velocities. 相似文献
20.
Few data are available for diffusion coefficients measured in industrial copper electrolytes. In the present work the influence
of copper concentration (19.9–58.1 g dm−3), temperature (20–60°C) and concentrations levelling agents i.e. animal glue (0–5 mg dm−3) and thiourea (0–5 mg dm−3) on diffusion coefficients of copper was studied in industrial copper refinery electrolytes. Chronoamperometry at ultramicroelectrodes
was used as an electrochemical technique. Apparent bulk diffusion coefficients were calculated on the basis of the theory
of electrochemical nucleation on disc-shaped ultramicroelectrodes. Increasing copper concentration decreased the apparent
bulk diffusion coefficient of copper and diffusion coefficients followed the Arrhenius temperature relationship. The experimental
activation energy was 26.8 kJ mol−1. The influence of levelling agents on diffusion coefficients was not strong in the studied concentration range of animal
glue and thiourea. 相似文献