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1.
Fuel cells are proposed as a future energy conversion technology that will reduce greenhouse gas emissions at the point of operation due to their ability to produce electrical energy from non-hydrocarbon fuel sources. The Solid Oxide Fuel Cell (SOFC) is amongst the most efficient fuel cell types, however, due to the high cell operating temperature cation diffusion occurs between the different components of the cell, resulting in rapid degradation of the power output. In this paper we investigate cation migration between the promising intermediate temperature-SOFC cathode La1−xSrxCo1−yFeyO3−δ (LSCF) and a fluorite type electrolyte Ce1−xPrxO2−δ (CPO). The crystallographic structure evolution and degradation of the materials were studied by neutron diffraction in-situ under pseudo-operating conditions, i.e. at 600 °C under air and under electrical polarisation. The lattice parameter and cation occupancy evolution were analysed by Rietveld refinement as a function of time and applied potential. The materials were found to be stable, as no impurity formation, lattice parameter or site occupancy evolution was observed during the experiment. However La migration prior to the experiment from LSCF to CPO was observed as well as B-site vacancies in LSCF. 相似文献
2.
M. Ali HaiderAaron J. Capizzi Mitsuhiro MurayamaSteven McIntosh 《Solid State Ionics》2011,196(1):65-72
La0.6Sr0.4CoxFe1−xO3−δ (LSCF), La0.6Sr0.4Cu0.2Fe0.8O3−δ, Ba0.5Sr0.4Co0.8Fe0.2O3−δ and LaFeO3−δ nanoparticles were synthesized by a reverse micelle procedure. Controlling the size of the micelles through the water:oil phase ratio enabled synthesis of phase pure perovskite particles with average sizes from 14 nm to 50 nm. Small amounts of an impurity phase, likely cobalt oxide, were detected in the XRD spectrum of high cobalt content samples of LSCF (x = 0.8). La0.6Sr0.4Co0.2Fe0.8O3−δ nanoparticles were utilized to coat the surface of a dense thin-film La0.6Sr0.4Co0.2Fe0.8O3−δ solid oxide fuel cell cathode. The polarization resistance of the nanoparticle coated electrode, measured at open circuit in air at 973 K, was 20% lower than an equivalent un-coated electrode. 相似文献
3.
固体氧化物燃料电池LSCF-SDC 纳米复合阴极制备及性能研究 总被引:1,自引:0,他引:1
利用硝酸盐溶液一次浸渗工艺在La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF)表面涂覆Sm0.2Ce0.8O2(SDC)纳米颗粒,制备了LSCF-SDC纳米结构复合阴极。微观结构分析显示SDC纳米颗粒在LSCF表面均匀分布并且颗粒大小均一。界面阻抗图谱表明SDC浸渗极大的降低了LSCF阴极的界面极化阻抗,在750和650℃仅为0.074,0.44Ω.cm2。LSCF-SDC复合阴极的表观活化能为1.42 eV,略小于纯LSCF阴极。与混合法制备的LSCF-GDC复合电极相比,采用浸渗工艺制备的LSCF-SDC纳米结构复合阴极也显示出良好的电化学催化活性。 相似文献
4.
Anke Hagen Marie Lund Traulsen Wolff‐Ragnar Kiebach Bjoern Sejr Johansen 《Journal of synchrotron radiation》2012,19(3):400-407
Solid oxide fuel cells (SOFCs) are able to produce electricity and heat from hydrogen‐ or carbon‐containing fuels with high efficiencies and are considered important cornerstones for future sustainable energy systems. Performance, activation and degradation processes are crucial parameters to control before the technology can achieve breakthrough. They have been widely studied, predominately by electrochemical testing with subsequent micro‐structural analysis. In order to be able to develop better SOFCs, it is important to understand how the measured electrochemical performance depends on materials and structural properties, preferably at the atomic level. A characterization of these properties under operation is desired. As SOFCs operate at temperatures around 1073 K, this is a challenge. A spectroelectrochemical cell was designed that is able to study SOFCs at operating temperatures and in the presence of relevant gases. Simultaneous spectroscopic and electrochemical evaluation by using X‐ray absorption spectroscopy and electrochemical impedance spectroscopy is possible. 相似文献
5.
Nicolas Droushiotis Mohd Hafiz Dzarfan Othman Uttam Doraswami Zhentao Wu Geoff Kelsall Kang Li 《Electrochemistry communications》2009,11(9):1799-1802
Novel CGO/NiO–CGO dual-layer hollow fibres (HFs) have been fabricated in a single-step co-extrusion and co-sintering process. LSCF–CGO cathodes layers were then deposited onto the dual-layer HFs to construct micro-tubular SOFCs. The NiO in the micro-tubular HF–SOFCs was reduced at 550 °C using hydrogen gas to form Ni anodes. Scanning electron microscope images showed that the dual-layer HFs have porous anodes and dense electrolyte layers. Preliminary measurements with a HF–SOFC fed with H2 and atmospheric oxygen, produced maximum power densities of 420 W m−2 and 800 W m−2 at 450 °C and 550 °C, respectively. 相似文献
6.
Nicolas Hildenbrand Bernard A. BoukampPieter Nammensma Dave H.A. Blank 《Solid State Ionics》2011,192(1):12-15
The electrochemical performance of porous La0.6Sr0.4Co0.2Fe0.8O3 − δ (LSCF) cathodes is improved by inserting a dense LSCF layer. A 200 nm thin layer is deposited on the electrolyte substrate by pulsed laser deposition, prior to the screen printing process. This procedure enhances the adherence of the porous cathode layer to the electrolyte and allows a lower sintering temperature, which reduces grain growth during sintering. In air a decrease in polarization resistance with a factor of 3 is observed for electrodes sintered at 1100 °C. The apparent electrolyte resistance is also reduced with the dense PLD layer. A remarkable change in Po2 dependence is observed for the Gerischer parameters that describe part of the electrode impedance, indicating a possible change in the oxygen transfer mechanism. 相似文献
7.
In this paper, the ionic conductivities of La0.54Sr0.44Co0.2Fe0.8O3-δ and La0.6Sr0.4Co0.2Fe0.8O3-δ were measured by electron-blocked alternating current impedance analysis technique. The results show that the oxygen ion conductivity of La0.54Sr0.44Co0.2Fe0.8O3-δ is nearly five times higher than that of La0.6Sr0.4Co0.2Fe0.8O3-δ, which makes La0.54Sr0.44Co0.2Fe0.8O3-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 La0.54Sr0.44Co0.2Fe0.8O3-δ and La0.6Sr0.4Co0.2Fe0.8O3-δ begin to react with 8YSZ([Y2O3]0.08·[ZrO2]0.92) at 850 °C, but La0.54Sr0.44Co0.2Fe0.8O3-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. 相似文献
8.
Effects of SO2 in ambient air on the performance and durability of solid oxide fuel cell(SOFC) cathode were evaluated by galvanostatic measurement. Comparison between two cathode materials was made to consider the cathode degradation mechanisms. The degradation performance is associated with a slow decomposition of the La0.6Sr0.4Co0.2Fe0.8O3(LSCF) due to the segregation of strontium oxide. Negligible deterioration for (La0.7Sr0.3)MnO3 (LSM) cathode was caused by SO2 poisoning under a current density of 200 mA/cm2. Metal sulphate formation may explain a slight deterioration under increasing high the concentration of SO2. It was verified that the poisoning mechanism for the two cathode materials resulted from the gradual decomposition of the cathode materials. 相似文献
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10.
The time-dependent degradation of the oxygen exchange kinetics of the solid oxide fuel cell cathode material La0.58Sr0.4Co0.2Fe0.8O3 − δ (LSCF) is investigated at 600 °C. Special emphasis is placed on systematic long-term dc-conductivity relaxation measurements (t > 1000 h) in dry as well as in humidified atmospheres in order to obtain representative trends for the application of LSCF in intermediate-temperature SOFCs. The determination of the chemical surface exchange coefficient kchem of oxygen is combined with investigations of the elemental surface compositions and depth profiles of fresh and degraded samples by X-ray photoelectron spectroscopy (XPS), providing further insight into the mechanisms of degradation. The slow decrease of kchem by a factor of 2 during exposure of the sample to a dry O2-Ar reference atmosphere for 1000 h at 600 °C can be ascribed to an enrichment of La and Sr in correlation with an elevated oxygen concentration within about 30-35 nm depth. The interpretation of the XPS core level spectra indicates the formation of SrO and La2O3 secondary phases in this zone. The subsequent treatment in a humidified atmosphere for 1000 h results in a pronounced initial decrease of kchem by an additional factor of 10, followed by a time dependent decay of about 15% kh− 1. A Sr-rich silicate layer of about 10 nm thickness is identified by XPS as the major cause of the degradation in humidified atmosphere. The evidence of Si-poisoning over the whole sample surface could also be confirmed by post-test SEM analysis. In addition, indications of a re-structuring of the sample surface during the degradation are shown. These results indicate, that with LSCF as a cathode in ambient (humid) air in SOFC stacks containing various Si-sources, such as glass or glass-ceramic seals, and thermal insulation materials a significant decrease of the surface oxygen exchange coefficient can occur, even at temperatures as low as 600 °C. In order to prevent a severe Si-induced degradation, dry air should be used as an oxidant. However, even in dry atmosphere a minor decrease of kchem can occur during long-term operation due to changes in the relative cation and oxygen content at the surface. 相似文献