| 1. |
- Tang, Z. G., et al.
(författare)
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SDC-LiNa carbonate composite and nanocomposite electrolytes
- 2010
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 35:7, s. 2970-2975
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Tidskriftsartikel (refereegranskat)abstract
- Structural and A.C. impedance analyses were conducted for various ceria-based composite systems. Structural studies showed that the ceria-carbonate composites are two-phase materials, where carbonates were often amorphous. Two phases of ceria and carbonates are mixed at different particle size levels depending on the preparation techniques, especially, employing the NANOCOFC (nanocomposites for advanced fuel cell technology) approach to prepare ceria-LiNaCO3 nanocomposites. General observations from structural analyses are that different preparation techniques resulted in two-phase composite particles in different particle sizes varying from micrometer level to nano-level accompanying also different homogeneity. General observations from impedance analyses are that for the nanocomposites (particle size at nano-scale) more complex grain boundary interface effects are observed compared to that for samples with grains of the micrometer level, but nanocomposites showed enhanced conductivities at the low temperatures. Interfaces and interfacial conduction mechanism can be concluded for such conductivity enhancement. Crown Copyright (C) 2009 Published by Elsevier Ltd on behalf of Professor T. Nejat Veziroglu. All rights reserved.
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| 2. |
- Abbas, Ghazanfar, et al.
(författare)
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Preparation and characterization of nanocomposite calcium doped ceria electrolyte with alkali carbonates (NK-CDC) for SOFC
- 2010
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Ingår i: ASME 2010 8th International Conference on Fuel Cell Science, Engineering and Technology, FUELCELL 2010. - : ASME Press. - 9780791844052 ; , s. 427-432
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Konferensbidrag (refereegranskat)abstract
- The entire world's challenge is to find out the renewable energy sources due to rapid depletion of fossil fuels because of their high consumption. Solid Oxide Fuel Cells (SOFCs) are believed to be the best alternative source which converts chemical energy into electricity without combustion. Nanostructured study is required to develop highly ionic conductive electrolyte for SOFCs. In this work, the calcium doped ceria (Ce0.8Ca0.2O 1.9) coated with 20% molar ratio of two alkali carbonates (CDC-M: MCO3, where M= Na and K) electrolyte was prepared by co-precipitation method in this study. Ni based electrode was used to fabricate the cell by dry pressing technique. The crystal structure and surface morphology was characterized by X-Ray Diffractometer (XRD), Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM). The particle size was calculated in the range of 10-20nm by Scherrer's formula and compared with SEM and TEM results. The ionic conductivity was measured by using AC Electrochemical Impedance Spectroscopy (EIS) method. The activation energy was also evaluated. The performance of the cell was measured 0.567W/cm2 at temperature 550°C with hydrogen as a fuel.
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| 3. |
- Chen, Mingming, et al.
(författare)
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Carbon anode in direct carbon fuel cell
- 2010
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 35:7, s. 2732-2736
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Tidskriftsartikel (refereegranskat)abstract
- Direct carbon fuel cell (DCFC) is a kind of high temperature fuel cell using carbon materials directly as anode. Electrochemical reactivity and surface property of carbon were taken into account in this paper. Four representative carbon samples were selected. The most suitable ratio of the ternary eutectic mixture Li2CO3-K2CO3-Al2O3 was determined at 1.05:1.2:1(mass ration). Conceptual analysis for electrochemical reactivity of carbon anode shows the importance of (1) reactive characteristics including lattice disorder, edge-carbon ratio and the number of short alkyl side chain of carbon material, which builds the prime foundation of the anodic half-cell reaction; (2) surface wetting ability, which assures the efficient contact of anode surface with electrolyte. It indicates that anode reaction rate and DCFC output can be notably improved if carbon are pre-dispersed into electrolyte before acting as anode, due to the straightway shift from cathode to anode for CO32- provided by electrolyte soaked in carbon material.
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| 4. |
- Di, J., et al.
(författare)
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Low temperature solid oxide fuel cells with SDC-carbonate electrolytes
- 2010
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Ingår i: Chinese Ceramics Communications. - : Trans Tech Publications Inc.. - 0878492755 - 9780878492756 ; , s. 687-690
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Konferensbidrag (refereegranskat)abstract
- Composites consisting of Ce0.8Sm0.2O1.9 (SDC)-carbonate were developed as electrolytes for low temperature solid oxide fuel cells (LTSOFC). The SDC power was prepared by sol-gel method. The carbonates were binary eutectics of (Li/Na)2CO3, (Li/K)2CO3 and (K/Na)2CO3. Conductivity measurements showed that the conductivities were depended on the type of carbonates. Discontinuities were found in the Arrhenius plots for both SDC-(Li/Na)2CO3 and SDC-(Li/K)2CO3. For SDC-(Na/K)2CO3 composite electrolyte, the conductivity increased as temperature rose following one slope. Single cells based on various composites were fabricated by a uniaxial die-press method and tested at 450-600 °C. The results showed all cells exhibited improved performances upon that of pure SDC-based cell. The best power density of 532 mW cm -2 at 600 °C was achieved for LTSOFC using composite of SDC and (Li/Na)2CO3. Conductivity mechanism was also discussed.
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| 5. |
- Di, Jing, et al.
(författare)
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Samarium doped ceria-(Li/Na)(2)CO3 composite electrolyte and its electrochemical properties in low temperature solid oxide fuel cell
- 2010
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 195:15, s. 4695-4699
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Tidskriftsartikel (refereegranskat)abstract
- A composite of samarium doped ceria (SDC) and a binary carbonate eutectic (52 mol% Li2CO3/48 mol% Na2CO3) is investigated with respect to its morphology, conductivity and fuel cell performances. The morphology study shows the composition could prevent SDC particles from agglomeration. The conductivity is measured under air, argon and hydrogen, respectively. A sharp increase in conductivity occurs under all the atmospheres, which relates to the superionic phase transition in the interface phases between SDC and carbonates. Single cells with the composite electrolyte are fabricated by a uniaxial die-press method using NiO/electrolyte as anode and lithiated NiO/electrolyte as cathode. The cell shows a maximum power density of 590 mW cm(-2) at 600 degrees C, using hydrogen as the fuel and air as the oxidant. Unlike that of cells based on pure oxygen ionic conductor or pure protonic conductor, the open circuit voltage of the SDC-carbonate based fuel cell decreases with an increase in water content of either anodic or cathodic inlet gas, indicating the electrolyte is a co-ionic (H+/O2-) conductor. The results also exhibit that oxygen ionic conductivity contributes to the major part of the whole conductivity under fuel cell circumstances. (C) 2010 Elsevier B.V. All rights reserved.
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| 6. |
- Lapa, C. M., et al.
(författare)
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Synthesis and characterization of composite electrolytes based on samaria-doped ceria and Na/Li carbonates
- 2010
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 35:7, s. 2953-2957
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Tidskriftsartikel (refereegranskat)abstract
- Samaria-doped ceria-based composites with a 2:1 addition of Li and Na carbonates (or simple Na carbonate as admixture) were prepared mixing nanosized powders of the ceramic phase with the remaining constituents. Samples fired at relatively low temperatures (below 700 degrees C) were characterized by X-ray diffraction, scanning electron microscopy combined with energy dispersive spectroscopy and impedance spectroscopy in air. These composites showed a complex but homogeneous distribution of both phases, with one ceramic skeleton of bonded nanosized grains surrounded by the carbonate-based phase. Impedance spectroscopy data was used to confirm the impressive electrical conductivity of these materials, but also to put into evidence the complex nature of the charge transport process, clearly deviating from classical electrolytes.
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| 7. |
- Liu, Qinghua, et al.
(författare)
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Theoretical description of superionic conductivities in samaria doped ceria based nanocomposites
- 2010
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 97:18, s. 183115-
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Tidskriftsartikel (refereegranskat)abstract
- Superionic conductivity becomes true based on recent developments on ceria-based nanocomposites as electrolytes with application for low temperature (300-600 degrees C) solid oxide fuel cells. We theoretically describe the superionic conductivity phenomena in samaria doped ceria nanocomposites. An improved effective-medium model was used to determine the ionic conductivity of the materials focusing on a core-shell structure of the as-prepared samaria doped ceria based composite particles. This work reveals the enhancement of ionic conductivity by interface proton and oxygen ion transportation in the composites, which agrees well with the experimental results.
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| 8. |
- Ma, Ying, et al.
(författare)
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Samarium-doped ceria nanowires : Novel synthesis and application in low-temperature solid oxide fuel cells
- 2010
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 22:14, s. 1640-1644
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Tidskriftsartikel (refereegranskat)abstract
- Samarium-doped ceria (SDC) nanowires are synthesized by a novel, template-, surfactant-free and cost-effective method, using citric acid as precipitating/complexing agent for formation of citrate precursor nanowires. The single SOFC based on SDC nanowires/Na2CO3 nanocomposites as electrolyte is fabricated and the maximum power densities of 417 and 522 mW cm-2 at 550 and 600°C are achieved, showing great potential for low-temperature SOFCs.
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| 9. |
- Ma, Ying, et al.
(författare)
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Thermal stability study of SDC/Na2CO3 nanocomposite electrolyte for low temperatur SOFCs
- 2010
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 35:7, s. 2580-2585
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Tidskriftsartikel (refereegranskat)abstract
- The novel core-shell nanostructured SDC/Na2CO3 composite has been demonstrated as a promising electrolyte material for low-temperature SOFCs. However, as a nanostructured material, stability might be doubted under elevated temperature due to their high surface energy. So in order to study the thermal stability of SDC/Na2CO3 nanocomposite, XRD, BET, SEM and TGA characterizations were carried on after annealing samples at various temperatures. Crystallite sizes, BET surface areas, and SEM results indicated that the SDC/Na2CO3 nanocomposite possesses better thermal stability on nanostructure than pure SDC till 700 °C. TGA analysis verified that Na2CO3 phase exists steadily in the SDC/Na2CO3 composite. The performance and durability of SOFCs based on SDC/Na2CO3 electrolyte were also investigated. The cell delivered a maximum power density of 0.78 W cm-2 at 550 °C and a steady output of about 0.62 W cm-2 over 12 h operation. The high performances together with notable thermal stability make the SDC/Na2CO3 nanocomposite as a potential electrolyte material for long-term SOFCs that operate at 500-600 °C.
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| 10. |
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