SrCe0.95Er0.05O3-α固体电解质的导电性

SrCe_0.95Er_0.05O_3-α ceramic of a single orthorhombic phase of perovskite-type SrCeO₃ was prepared by high-temperature solid state reaction. Using the ceramic as solid electrolyte and porous platinum as electrodes, the measurements of conductivities and ionic transport numbers on SrCe_0.95Er_0.05O_3-α ceramic were performed by using electrochemical methods in the temperature range of 600～1 000 ℃ in wet hydrogen, dry air and wet air, respectively. The results indicate that the sample is a pure protonic conductor with a maximal conductivity of 0.01 S·cm^-1 in wet hydrogen, a mixed conductor of oxide-ion and hole in dry air, and a mixed conductor of proton, oxide-ion and hole in wet air.     

Oxygen permeability and CO2-tolerance of Ce0.8Gd0.2O2-δ-Ln BaCo2O5+δ dual-phase membranes

A series of oxygen permeable dual-phase composite oxides 60 wt% Ce0.8Gd0.2O2-δ-40 wt% Ln Ba Co2O5+δ(CGO-LBCO, Ln = La, Pr, Nd,Sm, Gd and Y) were synthesized through a sol-gel route and effects of the Ln3+cations on their phase structure, oxygen permeability and chemical stability against CO2 were investigated systemically by XRD, SEM, TG-DSC and oxygen permeation experiments. XRD patterns reveal that the larger Ln3+cations(La3+, Pr3+and Nd3+) successfully stabilized the double-layered perovskite structure of sintered LBCO,while the smaller ones(Sm3+, Gd3+, and Y3+) resulted in the partial decomposition of LBCO with some impurities formed. CGO-PBCO yields the highest oxygen permeation flux, reaching 2.8×10-7mol s-1 cm-2at 925?C with 1 mm thickness under air/He gradient. The TG-DSC profiles in 20 mol% CO2/N2 and oxygen permeability experiments with CO2 as sweep gas show that CGO-YBCO demonstrates the best chemical stability against CO2, possibly due to its minimum basicity. The stable oxygen permeation flux of CGO-YBCO under CO2 atmosphere reveals its potential application in the oxy-fuel combustion route for CO2 capture.     

Structure and dielectric properties of 80%Pb(Zn1/3Nb2/3)O3–20%PbTiO3 thin films prepared by modified sol–gel process

80%Pb(Zn_1/3Nb_2/3)O₃–20%PbTiO₃ (PZN–PT) thin films have been prepared on Pt/Ti/SiO₂/Si substrates using a modified sol–gel method. In our method, niobium pentaoxide is used as a substitution instead of niobium ethoxide which is moisture-sensitivity and much more expensive. Microstructure and electrical properties of PZN–PT thin films have been investigated. X-ray diffraction analysis shows that proper annealing temperature of PZN–PT thin films is 600 °C. The PZN–PT thin films annealed at 600 °C are polycrystalline with (111)-preferential orientations. Field-emissiom scanning electron microscope analysis revealed PZN–PT thin films possess well-defined and crack-free microstructure. The thickness of thin films is 290 nm. The Pt/PZN–PT/Pt capacitors have been fabricated and it presents ferroelectric nature. The remanent polarization (Pr), spontaneous polarization (Ps), and the coercive electric field (Ec) are 8.71 μC/cm², 43.06 μC/cm², and 109 kV/cm at 1 MHz, respectively. The dielectric constant (ε_r) and the dissipation factor (tan δ) are about 500.3 and 0.1 at 1 kHz, respectively.     

Ionic Conduction and Fuel Cell Performance of Ba0.98Ce0.8Tm0.2O3-α Ceramic

The perovskite-type oxide solid solution Ba_0.98Ce_0.8Tm_0.2O_3-α was prepared by high tem-perature solid-state reaction and its single phase character was confirmed by X-ray diffrac-tion. The conduction property of the sample was investigated by alternating current impedance spectroscopy and gas concentration cell methods under different gases atmo-spheres in the temperature range of 500-900 oC. The performance of the hydrogen-air fuel cell using the sample as solid electrolyte was measured. In wet hydrogen, the sample is a pure protonic conductor with the protonic transport number of 1 in the range of 500-600 oC, a mixed conductor of proton and electron with the protonic transport number of 0.945-0.933 above 600 oC. In wet air, the sample is a mixed conductor of proton, oxide ion, and elec-tronic hole. The protonic transport numbers are 0.010-0.021, and the oxide ionic transport numbers are 0.471-0.382. In hydrogen-air fuel cell, the sample is a mixed conductor of proton, oxide ion and electron, the ionic transport numbers are 0.942-0.885. The fuel cell using Ba_0.98Ce_0.8Tm_0.2O_3-α as solid electrolyte can work stably. At 900 oC, the maximum power output density is 110.2 mW/cm², which is higher than that of our previous cell using Ba_0.98Ce_0.8Tm_0.2O_3-α (x≤1, RE=Y, Eu, Ho) as solid electrolyte.     

钙钛矿型Ba0.97Ca0.03Sn0.08Ti0.92O3-δ作为多硫化物固定剂在锂硫电池中的应用

制备具有氧空位的钙钛矿结构的Ba_0.97Ca_0.03Sn_0.08Ti_0.92O_3-δ（BCST）材料并将其作为多硫化物的固定剂,通过强的化学键合作用抑制多硫化物（LiPS）穿梭。作为促进LiPS转化的催化剂,BCST/KB/S （KB为科琴黑）正极在0.1C下提供了1 164.3 mAh·g^-1的初始放电容量,以及优异的循环稳定性。经过800次的充放电循环后,平均每次循环的容量衰减率仅为0.052%。     

Effect of Mo loading on transesterification activities of MoO3/γ-Al2O3 catalysts prepared by conventional and slurry impregnation methods

Summary The effect of Mo loadings and preparation methods, slurry and conventional impregnation, on the performances of alumina-supported MoO₃ catalysts in transesterification of dimethyl oxalate (DMO) with phenol was investigated. Slurry prepared MoO₃/-Al₂O₃ catalyst exhibited higher activity and dispersion capacity than conventional one. Slurry MoO₃/water was used instead of an ammonium heptamolybdate solution. Highly dispersed amorphous Mo catalysts were obtained, closely related to the catalytic activities without calcination, waste solutions, and calcining nitrogenous gases.     

钙钛矿型 Ba0.97Ca0.03Sn0.08Ti0.92O3-δ作为多硫化物固定剂在锂硫电池中的应用

制备具有氧空位的钙钛矿结构的Ba_0.97Ca_0.03Sn_0.08Ti_0.92O_3-δ(BCST)材料并将其作为多硫化物的固定剂,通过强的化学键合作用抑制多硫化物(LiPS)穿梭。作为促进LiPS转化的催化剂,BCST/KB/S(KB为科琴黑)正极在0.1C下提供了1 164.3 mAh·g^-1的初始放电容量,以及优异的循环稳定性。经过800次的充放电循环后,平均每次循环的容量衰减率仅为0.052%。     

Partial oxidation of methane in Ba0.5Sr0.5Co0.8Fe0.1Ni0.1O3-δ ceramic membrane reactor

Ba0.5Sr0.5Co0.8Fe0.1Ni0.1O3δ(BSCFNiO) perovskite oxides were synthesized using a combined EDTA-citrate complexation method,and then pressed into disk and applied in a membrane reactor.The performance of the BSCFNiO membrane reactor was studied for partial oxidation of methane over Ni/α-Al 2 O 3 catalyst.The time dependence of oxygen permeation rate and catalytic performance of BSCFNiO membrane during the catalyst initiation stage were investigated at 850 C.In unsteady state,oxygen permeation rate,methane conversion and CO selectivity were closely related to the state of the catalyst.After 300 min from the initial time,the reaction condition reached to steady state and oxygen permeation rate were obtained about 11.7cm 3 cm 2 min 1.Also,the performance of membrane reactor was studied at the temperatures between 750 and 950 C.The results demonstrated good performance for the membrane reactor,as CH 4 conversion and CO selectivity permeation rate reached 98% and 97.5%,respectively,and oxygen permeation rate was about 14.5 cm 3 cm 2 min 1 which was 6.8 times higher than that of air-helium gradient.Characterization of membrane surface by SEM after reaction showed that the original grains disappeared on both surfaces exposed to the air and reaction side,but XRD profile of the polished surface membrane indicated that the membrane bulk preserved the perovskite structure.     

The ionic conductivity, thermal expansion behavior, and chemical compatibility of La0.54Sr0.44Co0.2Fe0.8O3-δ as SOFC cathode material

In this paper, the ionic conductivities of La_0.54Sr_0.44Co_0.2Fe_0.8O_3-δ and La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ were measured by electron-blocked alternating current impedance analysis technique. The results show that the oxygen ion conductivity of La_0.54Sr_0.44Co_0.2Fe_0.8O_3-δ is nearly five times higher than that of La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ, which makes La_0.54Sr_0.44Co_0.2Fe_0.8O_3-δ cathode more conductive than YSZ electrolyte. Consequently, the electrochemical reaction region is extended from the interface between the cathode and the electrolyte to the whole surface of the cathode grains, with a result of the cathode polarization overpotential being decreased and the cell electrical performance being improved. Besides, the XRD results show that both La_0.54Sr_0.44Co_0.2Fe_0.8O_3-δ and La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ begin to react with 8YSZ([Y₂O₃]_0.08·[ZrO₂]_0.92) at 850 °C, but La_0.54Sr_0.44Co_0.2Fe_0.8O_3-δ with a faster reaction rate. The thermal expansion experiments manifest that the two LSCFs have approximate thermal expansion coefficients, being about 14 × 10⁻⁶–15 × 10⁻⁶ K⁻¹ from 500 °C to 700 °C, which is moderately higher than that of 8YSZ.     

On the preparation of asymmetric CaTi0.9Fe0.1O3−δ membranes by tape-casting and co-sintering process

Commercial deployment of membrane-based technology for high temperature gas separation requires the development of reliable processing of thin supported ceramic membranes. The asymmetric membranes should also demonstrate high oxygen flux in long term operation often encountered in stringent conditions. These requirements may be fulfilled by designing thin membrane films of chemically and mechanically strong CaTi_0.9Fe_0.1O_3−δ oxide material, as prepared in this work. The supported membranes were produced by means of a versatile manufacturing protocol with potential for mass production. It makes use of tape-casting, co-lamination and co-sintering of green laminates. The porosity of the mechanical supports was tailored through the addition of different pore formers, like corn starch and ammonium oxalate, in order to form a well-connected porous network. As-produced 30-μm thin supported CaTi_0.9Fe_0.1O_3−δ membranes were thoroughly characterized to establish relationships between manufacturing parameters and membrane microstructure. The oxygen permeation rates under air/argon gradient in the temperature range 800–1050 °C were investigated. It is concluded that pressure drop resistance in supports strongly contributed to reduce the oxygen flux. Appropriate selection of pore former type and content reduced this effect yielding increased oxygen flux, which became under control of bulk diffusion.     

Characteristics of La-modified Ni-Al2O3 and Ni-SiO2 catalysts for COx-free hydrogen production by catalytic decomposition of methane

Hydrotalcite precursors of La modified Ni-Al2O3 and Ni-SiO2 catalysts prepared by co-precipitation method and the catalytic activities were examined for the production of COx-free H2 by CH4 decomposition. Physico-chemical characteristics of fresh, reduced and used catalysts were evaluated by XRD, TPR and O2 pulse chemisorptions, TEM and BET-SA techniques. XRD studies showed phases due to hydrotalcite-like precursors in oven dried form produced dispersed NiO species upon calcination in static air above 450 C. Raman spectra of deactivated samples revealed the presence of both ordered and disordered forms of carbon. Ni-La-Al2O3catalyst with a mole ratio of Ni : La : Al = 2 : 0.1 : 0.9 exhibited tremendously high longevity with a hydrogen production rate of 1300 molH2 mol 1 Ni. A direct relationship between Ni metal surface area and hydrogen yields was established.     

Structure, magnetic, and electric properties of bismuth niobates doped with d -Elements: VI. Magnetic behavior of Bi3Nb3?3 x Ni3 x O15?δ solid solutions

Magnetic susceptibility of nickel-containing solid solutions with layered perovskite-like structure of bismuth niobate, Bi₅Nb₃O₁₅, was studied. High-spin nickel atoms, Ni(III), were present at low concentrations of the solid solutions. The formation of exchange-bonded aggregates (dimers) of nickel(II) atoms with antiferromagnetic type of exchange was found in the solid solutions. The parameters of exchange interactions in the dimer clusters and the distribution of monomers and dimers of nickel atoms were calculated as a function of the solid solution concentration. Original Russian Text ? N.A. Zhuk, I.V. Piir, N.V. Chezhina, 2008, published in Zhurnal Obshchei Khimii, 2008, Vol. 78, No. 3, pp. 393–399. For communication V, see [1].     

A simple and easy one-step fabrication of thin BaZr0.1Ce0.7Y0.2O3−δ electrolyte membrane for solid oxide fuel cells

A green BaZr_0.1Ce_0.7Y_0.2O_3−δ (BZCY) electrolyte layer was deposited on porous anode substrate (BZCY:NiO = 35:65, in weight ratio) by a suspension spray. In this process, the suspension was prepared by directly ball-milling the mixed BaCO₃, CeO₂, ZrO₂ and Y₂O₃ powders in ethanol for 24 h. Then the bi-layers were co-sintered at 1400 °C for 5 h in air to obtain dense and uniform electrolyte membrane in the thickness of 10 μm. With Nd_0.7Sr_0.3MnO_3−δ cathode, a fuel cell was assembled. It was tested from 600 °C to 700 °C using humid hydrogen as fuel and air as oxidant. The cell at 700 °C exhibited 1.02 V for open circuit voltage (OCV), 450 mW/cm² for peak output and 0.18 Ω cm² for electrode polarizations under open circuit conditions, respectively. The results indicate that it is feasible to fabricate thin electrolyte membrane for solid oxide fuel cells (SOFCs) by this simple, cost-effective and efficient technique.     

Dopant effects on the structural, low temperature Raman scattering and electrical transport properties in SrTi1?xFexO3 nanoparticles synthesized by sol-gel method

We investigate effects of Fe dopant concentration on the structure, as well as low temperature Raman scattering and electrical transport properties in SrTi_1−x Fe _x O₃ (x = 0.00, 0.10, 0.20, 0.30, 0.40) nanoparticles prepared by sol-gel method. The results show an average particle size of powder is about 30 nm, and the lattice parameters decrease as increasing the Fe content. In the Raman spectra, a broad structure in the region 200–500 cm⁻¹ is almost absent and the peaks in the region 600–800 cm⁻¹ show different weights with respect to SrTiO₃, relating to structural changes with increasing dopant concentration in conjunction with increasing grain boundary contribution to the impedance. The abrupt change in Raman peak position as function of temperature suggests a phase transition in our samples in the range of 110–150 K. These results indicate that the Fe ion has replaced the site of Ti in unit cell. These results also demonstrate the feasibility of synthesizing the compound with low annealing temperature.     

Investigation of Ba fully occupied A-site BaCo0.7Fe0.3−xNbxO3−δ perovskite stabilized by low concentration of Nb for oxygen permeation membrane

BaCo_0.7Fe_0.3−xNb_xO_3−δ (BCFN, x = 0–0.2) were prepared by the conventional solid state reaction process. The crystal structure, electrical conductivity and oxygen desorption property were studied by X-ray diffraction (XRD), different thermal analysis (DTA), four-terminal direct current conductivity and oxygen temperature programmed desorption (O₂-TPD), respectively. At x = 0.08–0.20, BCFN have a cubic perovskite structure, while it exhibits the hexagonal structure for x = 0.00 and the mixed phases of cubic perovskite with trace amount of hexagonal for x = 0.05. BCFN shows good structure stability in 5%H₂ + Ar reducing atmosphere, and it is enhanced with the increased Nb-doping content. The electrical conductivity of BCFN increases with increasing temperature and decreases with the Nb substitution content for iron. BCFN exhibits a p-type semiconductor and obeys the thermally activated small polarons hopping mechanism. The oxygen fluxes increase with the working temperature and the COG flow rate, but decrease with increasing Nb content. The flux of BCFN (x = 0.08) with 1.0 mm thickness membrane reaches 25.77 ml min⁻¹ cm⁻² at 875 °C, higher than most of the reported materials.     

Ca and Sr co-doping induced oxygen vacancies in 3DOM La2-xSrxCe2-yCayO7-δ catalysts for boosting low-temperature oxidative coupling of methane

It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM) at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_2-xSr_xCe_2-yCa_yO_7-δ(A₂B₂O₇-type) catalysts with disordered defective cubic fluorite phased structure were successfully prepared by a colloidal crystal template method.3DOM structure promotes the accessibility of the gaseous rea...     

X-ray photoelectron (XPS) and Diffuse Reflectance Infra Fourier Transformation (DRIFT) study of Ba0.5Sr0.5CoxFe1−xO3−δ (BSCF: x=0-0.8) ceramics

The X-ray photoelectron spectra (XPS) of sintered BSCF ceramics (Ba_0.5Sr_0.5Co_xFe_1-xO_3-δ,0≤x≤0.8) were measured at room temperature (RT). Peak areas of Fe_2p1, Fe_2p3, Fe_3p and Co_3p increased systematically with increasing cobalt concentration, while their binding energies (BEs) remained the same (723.3, 710.0, 55.0 and 60.9 eV, respectively). However, the BEs of lattice oxygen in O_1s (528.1 eV) and Ba_4d for the BaO bond (87.9V and 90.2 eV) increased with increasing cobalt concentration. The shoulder peak of Ba_3d/Co_2p increased from 778.0 to 778.7 eV, which implies that this peak can be attributed to another Ba XPS peak (described as Ba_2nd in this study) due to the overlapping area between barium cations and oxygen anions. The overall peak areas of Ba_4d increased up to x=0.4, and then decreased, which coincides with the behavior of the Diffuse Reflectance Infrared Fourier Transform (DRIFT) bands representing adsorbed CO₃²⁻ (νCO₃²⁻) and structurally bonded CO₃²⁻ (ν₂, ν₃) (800-1200 and 862/1433 cm⁻¹, respectively).     

Electrical and electrochemical characteristics of La<Subscript>0.6</Subscript>Sr<Subscript>0.4</Subscript>CoO<Subscript>3-δ</Subscript> cathode materials synthesized by a modified citrate-EDTA sol-gel method assisted with activated carbon for proton-conducting solid oxide fuel cell application

The electrical conductivity and electrochemical performance of a La_0.6Sr_0.4CoO_3-δ (LSC) cathode produced by a modified citrate-EDTA sol-gel method assisted with activated carbon are characterized for a proton-conducting solid oxide fuel cell (H⁺??SOFC) application at intermediate temperature. Thermogravimetric analysis revealed that the decomposition of the unrequired intermediate compounds in the precalcined powder was completed at 800?°C. A single LSC perovskite phase was formed at a calcination temperature of 900?°C, as confirmed by X-ray diffraction analysis. The particle size, crystallite size, and BET-specific surface area of the powder are 219–221?nm, 18?nm, and 9.87?m²?g^?1, respectively. The high index value of the extent of agglomeration (5.53) showed that the powder was barely agglomerated. Bulk LSC sintered at 1200?°C for 2?h showed the highest direct-current electrical conductivity (σ_d.c) compared to that of bulk LSC sintered at 1000?°C and 1100?°C. The value of σ_d.c was affected by the density and porosity of the sintered samples. The area specific resistance (ASR) of screen-printed LSC working on a proton conductor of BaCe_0.54Zr_0.36Y_0.1O_2.95 (BCZY) decreased from 5.0?Ω?cm²–0.06?Ω?cm² as the temperature increased from 500?°C to 800?°C with an activation energy of 1.079?eV. Overall, in this work, the LSC material produced with the aid of activated carbon meet the requirements for the application as a cathode in an intermediate temperature H⁺-SOFC.

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