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1.
J. C. Castro R. M. Antoniassi R. R. Dias M. Linardi E. V. Spinacé A. Oliveira Neto 《Ionics》2012,18(8):781-786
PtSnRh/C-Sb2O5·SnO2 electrocatalysts with different Pt/Sn/Rh atomic ratios (90:05:05, 70:25:05, and 50:45:05) were prepared by an alcohol reduction process using H2PtCl6·6H2O, SnCl2·2H2O, RhCl3·xH2O as metal sources, ethylene glycol as solvent and reducing agent, and a physical mixture of Vulcan XC72 (85?wt%) and Sb2O5·SnO2 (15?wt%) as support. The electrocatalysts were characterized by X-ray diffraction and transmission electron microscopy. The electro-oxidation of ethanol was studied by cyclic voltammetry and chronoamperometry at 25 and 50?°C and in single direct ethanol fuel cell (DEFC) at 100?°C. The diffractograms of PtSnRh/C-Sb2O5·SnO2 electrocatalysts showed the peaks characteristic of Pt face-centered cubic structure and several others peaks associated with ·SnO2 and Sb2O5·SnO2. Transmission electron micrographs of PtSnRh/C-Sb2O5·SnO2 electrocatalysts showed the metal nanoparticles distributed on the supports with particle sizes of about 2?C3?nm. The electrochemical measurements and the experiments in a single DEFC showed that PtSnRh/C-Sb2O5·SnO2 (90:05:05) and PtSnRh/C-Sb2O5·SnO2 (70:25:05) electrocatalysts exhibited higher performance for ethanol oxidation in comparison with PtSnRh/C electrocatalyst. 相似文献
2.
PtSn/C and PtSnSb/C electrocatalysts (20 wt.% metal loading) were prepared by an alcohol reduction process using H2PtCl6.6H2O, SnCl2.2H2O, and Sb(OOCCH3) as metal sources, ethylene glycol as solvent and reducing agent, and Vulcan XC72 as carbon support. The
electrocatalysts were characterized by energy dispersive X-ray analysis, X-ray diffraction, and transmission electron microscopy,
while that the performance for ethanol oxidation was investigated by cyclic voltammetry and chronoamperommetry (chrono) at
room temperature. The diffractograms of the PtSn/C and PtSnSb/C electrocatalysts showed four peaks associated to Pt face-centered
cubic structure and two peaks that were related to a SnO2 phase. For PtSb/C and PtSnSb/C electrocatalysts, no Sb (antimony) peaks corresponding to a metallic antimony or antimony
oxide phases were observed. Transmission electron microscopy images showed that the metal particles were homogeneously distributed
over the support. The PtSnSb/C (50:45:05) electrocatalyst showed an increase of performance for ethanol oxidation in relation
to PtSn/C electrocatalyst at room temperature. In the tests at 100 °C on a single cell of a direct ethanol fuel cell, the
maximum power density of PtSnSb/C (50:45:05) electrocatalyst was slightly higher than that of PtSn/C electrocatalyst. 相似文献
3.
R. M. S. Rodrigues M. M. Tusi M. H. Chikasawa C. A. L. G. O. Forbicini M. Linardi E. V. Spinacé A. Oliveira Neto 《Ionics》2011,17(2):189-193
PtRu/C (100% C) and PtRu/C-CeO2, PtRu/C-La2O3, PtRu/C-Nd2O3, and PtRu/C-Er2O3 (85% C and 15% rare earth) electrocatalysts were prepared in a single step by an alcohol-reduction process using H2PtCl6 6H2O and RuCl3 xH2O as metal sources, ethylene glycol as solvent and reducing agent, Vulcan XC72 and rare earth (RE) as support. The electrocatalysts
were characterized by energy dispersive X-ray, X-ray diffraction, and transmission electron microscopy. The performance for
ethanol oxidation was investigated by cyclic voltammetry and chronoamperommetry at room temperature, and studies on the direct
ethanol fuel cell were carried at 100 °C. The Pt:Ru atomic ratios were similar to the nominal used in preparation, and the
average particle sizes were in the range of 2.0–3.0 nm. All PtRu/C-RE electrocatalysts showed an increase of performance for
ethanol oxidation at room temperature and also on a single direct ethanol fuel cell tests in relation to PtRu/C electrocatalyst
at 100 °C. 相似文献
4.
J. Nandenha R. F. B. De Souza M. H. M. T. Assumpção E. V. Spinacé A. O. Neto 《Ionics》2013,19(9):1207-1213
Pd/C-Sb2O5·SnO2 and PdAu/C-Sb2O5·SnO2 electrocatalysts with different PdAu atomic ratio (90:10, 70:30, and 50:50) were prepared by borohydride reduction method, and characterized by X-ray diffraction, transmission electron microscopy, cyclic voltammetry, chronoamperommetry, and performance test on direct formic acid fuel cell at 100 °C. X-ray diffraction showed for Pd/C-Sb2O5·SnO2 the presence of Pd face-centered cubic (fcc) system, while for PdAu/C-Sb2O5·SnO2 it showed the presence of Pd fcc phase, PdAu fcc alloys and a segregated phases fcc Pd-rich and Au-rich phases. TEM micrographs and histograms for all electrocatalysts showed that the nanoparticles where not well dispersed on the support and some agglomerates were present. The electrochemical studies showed that PdAu/C-Sb2O5·SnO2 (70:30) had superior performance for formic acid electro-oxidation at 25 °C compared to others electrocatalysts prepared while PdAu/C-Sb2O5·SnO2 (90:10) showed superior performance in direct formic acidic fuel cell at 100 °C. These results indicated that the addition of 10–30 % Au to Pd favor the electro-oxidation of formic acid. This effect could be attributed to the synergy between the constituents of the electrocatalyst (metallic Pd and Au, SnO2, and Sb2O5·SnO2). 相似文献
5.
J.L. Crisp S.E. Dann M. Edgar C.G. Blatchford 《Solid state nuclear magnetic resonance》2010,37(3-4):75-81
The polymorphic forms of lactose in alcoholic suspensions have been determined by 13C CP-MAS NMR spectroscopy, employing hand-made glass inserts. Suspensions of alpha lactose monohydrate (Lα·H2O) with particle size between 2 and 200 μm were prepared by 24 h reflux or by storage for 28 d in anhydrous ethanol without agitation. These suspensions were compared to an ethanolic sub-micron lactose suspension provided by a 3 M Health Care (Loughborough). The 13C CP-MAS NMR spectra indicated that Lα·H2O dehydrated to stable anhydrous alpha lactose polymorph (LαS) whilst suspended in ethanol. In addition, strong ethanol 13C resonances were observed for some samples, indicating a liquid–solid interaction between the ethanol and lactose surface. Replacement of ethanol with anhydrous methanol, n-butanol and 3-methylbutan-2-ol implied that the solvent mediated dehydration of Lα·H2O to LαS occurs as a result of sterically controlled interactions. 相似文献
6.
A new strategy, epoxide-assisted precipitation route presented in this work, allows the shape control synthesis of Co3O4 nanoparticles. The shape of the nanoparticles is determined by the nature of the precursor cobalt salts (Co(NO3)2 · 6H2O, CoCl2 · 6H2O) used for the preparation of the particles. The different reaction dynamics of the two salts in ethanolic and aqueous solutions
with propylene oxide result in precursor particles with different structures, which lead to the formation of oxide nanoparticles
with different shapes during the heat treatment. Spherical particles of about 20 nm are obtained from the ethanolic solution
of Co(NO3)2 · 6H2O; cubic-shaped particles of about 30 nm can be prepared from the ethanolic solution of CoCl2 · 6H2O; whereas platelet-like particles of more than 100 nm are synthesized from the aqueous solution of the mixture of Co(NO3)2 · 6H2O and CoCl2 · 6H2O. 相似文献
7.
S. C. Mailley A. Kelaidopoulou A. Siddle A. L. Dicks P. Holtappels C. E. Hatchwell M. Mogensen 《Ionics》2000,6(5-6):331-339
Mixed conducting oxide anodes are being considered for the direct utilisation of natural gas in high temperature fuel cells.
This work refers to the electrochemical characterization of the pyrochlore Gd2Ti0.6Mo1.2Sc0.2O7-δ (GTMS) as anode in a solid oxide fuel cell running in low humidity hydrogen or methane.
The electro-oxidation reaction was investigated using impedance spectroscopy, potentiostatic measurements and cyclic voltammetry.
Kinetic data were obtained for different fuels in the temperature range 845–932 °C. In a methane-fuelled cell, steam reforming
appears to be the rate-limiting step. The overall polarisation resistance of the anode under open circuit conditions at 932
°C was 6.86 Ω·cm2 in 97% H2/3% H2O, and 43 Ω·cm2 in 97% CH4/3% H2O. For a 97% fuel-3% H2O/GTMS//YSZ-Al2O3//Pt/air cell, the maximum power output at 932 °C was 9.5 mW/cm2 and 1.8 mW/cm2 in hydrogen and methane, respectively. First investigations on this type of electrode material show unidentified peaks on
XRD spectra after electrochemical test, which indicate GTMS instability under experimental conditions.
Paper presented at the 7th Euroconference on Ionics, Calcatoggio, Corsica, France, Oct. 1–7, 2000. 相似文献
8.
E. V. Spinacé Ricardo R. Dias Michele Brandalise Marcelo Linardi Almir Oliveira Neto 《Ionics》2010,16(1):91-95
PtRh/C (90:10), PtRh/C (50:50), PtSn/C (50:50), and PtSnRh/C (50:40:10) electrocatalysts were prepared by an alcohol-reduction
process using ethylene glycol as solvent and reduction agent and Vulcan Carbon XC72 as supports. The electrocatalysts were
characterized by energy-dispersive X-ray analysis, X-ray diffraction, and transmission electron microscopy. The electro-oxidation
of ethanol was studied by cyclic voltammetry chronoamperometry at room temperature and on a single cell of a direct ethanol
fuel cell at 100 °C. Cyclic voltammetry and chronoamperometry experiments showed that PtSnRh/C and PtSn/C electrocatalysts
have similar performance for ethanol oxidation at room temperature, while the activity of PtRh/C electrocatalysts was very
low. At 100 °C on a single cell, PtSnRh/C showed superior performance compared to PtSn/C and PtRh/C electrocatalysts. 相似文献
9.
In the present work, carbon-supported Pt–Sn, Pt–Ru, and Pt–Sn–Ru electrocatalysts with different atomic ratios were prepared by alcohol-reduction method to study the electro-oxidation of ethanol in membraneless fuel cells. The synthesized electrocatalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) analyses. The prepared catalysts had similar particle morphology, and their particle sizes were 2–5 nm. The electrocatalytic activities were characterized by cyclic voltammetry (CV) and chronoamperometry (CA). The electrochemical results obtained at room temperature showed that the addition of Sn and Ru to the pure Pt electrocatalyst significantly improved its performance in ethanol electro-oxidation. The onset potential for ethanol electro-oxidation was 0.2 V vs. Ag/AgCl, in the case of the ternary Pt–Sn–Ru/C catalysts, which was lower than that obtained for the pure Pt catalyst (0.4 V vs. Ag/AgCl). During the experiments performed on single membraneless fuel cells, Pt ? Sn ? Ru/C (70:10:20) performed better among all the catalysts prepared with power density of 36 mW/cm2. The better performance of ternary Pt–Sn–Ru/C catalysts may be due to the formation of a ternary alloy and the smaller particle size. 相似文献
10.
Weizhong Lv Zhongkuan Luo Hui Yang Bo Liu Wenjiang Weng Jianhong Liu 《Ultrasonics sonochemistry》2010,17(2):344-351
Nanosized copper aluminate (CuAl2O4) spinel particles have been prepared by a precursor approach with the aid of ultrasound radiation. Mono-phasic copper aluminate with a crystallite diameter of 17 nm along the (3 1 1) plane was formed when the products were synthesized using Cu(NO3)2·6H2O and Al(NO3)3·9H2O as starting materials, with urea as a precipitation agent at a concentration of 9 M. The reaction was carried out under ultrasound irradiation at 80 °C for 4 h and a calcination temperature of 900 °C for 6 h. The synthesized copper aluminate particles and the effect of different processing conditions such as the copper source, precipitation agents, sonochemical reaction time, calcination temperature and time were analyzed and characterized by the techniques of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and Fourier transformation infrared spectroscopy (FT–IR). 相似文献
11.
PtSn/C electrocatalysts (Pt:Sn atomic ratios of 50:50 and 60:40) were prepared using citric acid as reducing agent, and the
pH of the reaction medium was varied by the addition of OH− ions. The obtained electrocatalysts were characterized by energy dispersive X-ray analysis, X-ray diffraction, and transmission
electron microscopy. The electrocatalysts were tested on the direct ethanol fuel cell (DEFC) at 90 °C. The obtained PtSn/C
electrocatalysts showed the presence of a face-centered cubic, Pt, and SnO2 phases. In DEFC studies, the PtSn/C electrocatalysts showed a superior performance compared to a commercial PtSn/C and Pt/C
electrocatalysts from E-TEK. 相似文献
12.
P. C. Fannin C. N. Marin I. Malaescu N. Stefu P. Vlăzan S. Novaconi S. Popescu 《Journal of nanoparticle research》2011,13(1):311-319
Zn/Fe oxide compound powders were obtained by the hydrothermal method using ferric nitrate Fe(NO3)3·9H2O and zinc nitrate Zn(NO3)2·6H2O at 200 °C and different precursor molar ratios x = Fe3+/Zn2+ equal to 2.8/0.2, 2.5/0.5, 1.8/1.2 and 1.5/1.5. The samples were characterized by X-ray diffraction (XRD) and scanning electron
microscopy/energy dispersive X-ray analysis (SEM–EDAX). Room temperature measurements of the frequency dependence of the complex
magnetic permeability and complex dielectric permittivity, over the frequency range from 0.1 to 6 GHz, were performed. For
precursor molar ratios x = 2.8/0.2, x = 1.8/1.2 and x = 1.5/1.5 the obtained samples showed a ferromagnetic-like resonance behaviour. This behaviour was assigned to the prevalent
compounds in the obtained samples, Fe2O3 (for x = 2.8/0.2) and ZnFe2O4 (for x = 1.8/1.2 and x = 1.5/1.5). Based on the magnetic and dielectric measurements, the microwave absorbent properties of the four samples were
analysed, and the sample containing mostly of ZnFe2O4 (for x = 1.8/1.2) was found to be the best electromagnetic absorber in the frequency range 1.36–6 GHz. 相似文献
13.
《Solid State Ionics》2006,177(15-16):1335-1339
Electrochemical characteristics of lithium ruthenate (LixRuO2+0.5x·nH2O) for electrochemical capacitors' electrode material were first examined in this paper by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge–discharge tests. Results show that LixRuO2+0.5x·nH2O has electrochemical capacitive characteristic within the potential range of − 0.2–0.9 V (vs. SCE) in 1 M Li2SO4 solution. The capacitance mainly arises from pseudo-capacitance caused by lithium ions' insertion/extraction into/out of the LixRuO2+0.5x·nH2O electrode. The specific capacitance of 391 F g− 1 can be delivered at 1 mA charge–discharge current for LixRuO2+0.5x·nH2O electrode with an energy density of 65.7 W h kg− 1. This material also exhibits an excellent cycling performance and there is no attenuation of capacitance over 600 cycles. 相似文献
14.
15.
《Solid State Ionics》1988,26(2):63-69
Layered phosphonate salts of divalent metal ions (Mg, Ca and Mn) are prepared by combining solutions of soluble metal salts and alkyl- or arylphosphonic acids. In this way the compounds Mg(O3PCnH2n+1)·H2O (n=1−12), Mg(O3PC6H5)·H2O, Mg(HO3PCH(C6H5)2)2·8 H2O, Mn(O3PCH3)·H2O, Mn(O3PC6H5)·H2O, Ca(O3PCnH2n+1)·H2O (n⩽5), Ca(HO3PC6H5)2 and Ca(HO3PCnH2n+1)2 (n⩾6) were prepared. The M(O3PC6H5)·H2O compounds show good thermal stability, losing lattice water at 250–300°C without further decomposition below 550°C. Compounds derived from alkylphosphonic acids decompose at lower temperatures. The Mg(O3PCnH2n+1)·H2O series, Mg(O3PC6H5)·H2O, and Mn(O3PC6H5)·H2O group Pmn21; for the latter compound unit cell dimensions (Å) are a=5.733, b=14.298, c=4.931. The structure consists of roughly coplanar layers of metal atoms coordinated by phenylphosphonate groups above and below. Each metal atom is coordinated by five phosphonate oxygens and one lattice water molecule. Mg(O3PCnH2n+1·H2O adopts a similar structure; infrared spectra indicate all-trans alkyl chains. In Mg(HO3PCH(C6H5)2)2·8 H2O, Mg(H2O)2+6 ions and lattice water lie in hydrogen-bonded sheets; the benzhydryl groups lie above and below and make van-der-Waals contacts between layers. 相似文献
16.
《Current Applied Physics》2008,8(5):535-541
In this paper, we reported a method to prepare monodisperse magnetite nanoparticles at mild temperature using cheap and non-toxic precursors. It overcomes the shortages of chemical co-precipitation method and thermal decomposition method and combines the advantages of facile, cheap, large-scale, monodisperse, nanosize, and low synthesis temperature and low toxic. In this method, FeCl3 · 6H2O, FeCl2 · 4H2O and sodium oleate were mixed in toluene/ethanol/water mixture solvent and refluxed at 74 °C to prepare magnetite nanoparticles directly. The nanoparticles were characterized by transmission electron microscopy, dynamic light scattering, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometer and thermogravimetric analysis. The magnetic properties of nanoparticles were measured by superconducting quantum interference device. The results showed that the nanoparticles are well-monodisperse with about 4–5 nm of average diameter. The nanoparticles were proved to be superparamagnetic with saturated magnetization 23.6 emu/g and blocking temperature 24.4 K. A possible formation mechanism of monodisperse magnetite nanoparticles was presented at the same time. 相似文献
17.
Six new lanthanide(III) complexes (i.e., [Ln(L)2(NA)1.5]·3H2O, where Ln=La(III), Pr(III), Nd(III), Sm(III), Gd(III), and Ce(III) and L and NA indicate N2H4 and C10H6(1-O)(2-COO), respectively) with 1-hydroxy-2-naphthoic acid [C10H6(1-O)(2-COOH)] and hydrazine (N2H4) as co-ligands were characterized by elemental, FTIR, UV-visible, and XRD techniques. In the FT-IR spectra, the N-N stretching frequency in the range of 981–949 cm−1 demonstrates evidence of the presence of coordinated N2H4, indicating the bidentate bridging nature of hydrazine in the complexes. These complexes show symmetric and asymmetric COO− stretching from 1444 to 1441 cm−1 and 1582 to 1557 cm−1, respectively, indicating bidentate coordination. TG-DTA studies revealed that the compounds underwent endothermic dehydration from 98 to 110 °C. This was followed by the exothermic decomposition of oxalate intermediates to yield the respective metal oxides as the end products. From SEM images, the average size of the metal oxide particles prepared by thermal decomposition of the complexes was determined to be 39–42 nm. The powder X-ray and SEM coupled with energy dispersive X-ray (EDX) studies revealed the presence of the respective nano-sized metal oxides. The kinetic parameters of the decomposition of the complexes were calculated using the Coats-Redfern equation. 相似文献
18.
A cobalt(II) complex of 6-methylpicolinic acid, [Co(6-Mepic)2(H2O)2]·2H2O, was prepared and fully determined by single crystal X-ray crystal structure analysis as well as FT-IR, FT-Raman. UV–vis spectra were recorded within different solvents, to illustrate electronic transitions and molecular charge transfer within complex 1. The coordination sphere of complex 1 is a distorted octahedron according to single crystal X-ray results. Moreover, DFT (density functional theory) calculations with HSEH1PBE/6-311 G(d,p) level were carried out to back up the experimental results, and form base for future work in advanced level. Hyperconjugative interactions, intramolecular charge transfer (ICT), molecular stability and bond strength were researched by the using natural bond orbital (NBO) analysis. X-ray and NBO analysis results demonsrate that O−H···O hydrogen bonds between the water molecules and carboxylate oxygen atoms form a 2D supramolecular network, and also adjacent 2D networks connected by C−H···π and π···π interactions to form a 3D supramolecular network. Additionally, the second− and third−order nonlinear optical parameters of complex 1 were computed at DFT/HSEH1PBE/6-311 G(d,p) level. The refractive index (n) was calculated by using the Lorentz−Lorenz equation in order to investigate polarization behavior of complex 1 in different solvent polarities. The first−order static hyperpolarizability (β) value is found to be lower than pNA value because of the inversion symmetry around Co (II). But the second−order static hyperpolarizability (γ) value is 2.45 times greater than pNA value (15×10−30 esu). According to these results, Co(II) complex can be considered as a candidate to NLO material. Lastly molecular electrostatic potential (MEP), frontier molecular orbital energies and related molecular parameters for complex 1 were evaluated. 相似文献
19.
Ming Wen Kejia E Haiquan Qi Lujiang Li Juan Chen Ying Chen Qingsheng Wu Tao Zhang 《Journal of nanoparticle research》2007,9(5):909-917
Dispersed-well FePt nanoparticles with particle size ~5 nm have been prepared by hydrazine hydrate reduction of H2PtCl6·6H2O and FeCl2·4H2O in ethanol–water system. By employing as-synthesized FePt nanoparticles, the monolayer can be formed by LB Technique. The
structural, magnetic properties and electrochemical properties of FePt monolayer were respectively studied by XRD, TEM, VSM
and CHI 820 electrochemical workstation. The as-synthesized particle has a chemically disordered fcc structure and can be
transformed into chemically ordered fct structure after annealing treatment above 400°C. The coercivity of ordered fct FePt
phase can be up to 2515Oe. CVs of 0.5 M H2SO4/0.5M CH3OH on GCE modified with FePt nanoparticles monolayer films illustrate that the as-synthesized FePt is a kind of active electrochemical
catalyst. 相似文献
20.
In the present work policrystals of α − Al2O3 doped with terbium were synthesized using the solvent evaporation method. The samples were prepared using Al(NO3)3·9H2O and Tb(NO3)3·5H2O reagents, with Tb concentrations between 1 and 5 mol% and thermally treated at high temperature above ∼1400 °C. X-ray diffraction measurements showed the α-phase formation of samples. TL glow curve presented an intense peak at ∼190 °C and two other with low intensity at 290 and 350 °C after gamma irradiation. The best doping concentration which presented high luminescence was the sample doped with 3 mol% of Tb. TL spectra and fluorescence measurements showed similar luminescence spectra with lines attribute to Tb3+ ions. A linear behavior to gamma dose between 1 and 20 Gy was observed in TL, using 190 °C peak as well as in OSL signal, this last carried out using 532 nm wavelength stimulation. 相似文献