Investigation of the influence at temperature, oxygen partial pressure and cathode polarization on solid oxide fuel cell cathode lattice parameters in situ measurement
conditions
The solid oxide fuel cell cathode electrodes have been studied using electrochemical characterisation and in situ X-ray diffraction analysis methods at various electrode potentials, temperatures and oxygen partial pressures.
Analysis of x-ray diffraction data confirm that the La1-xSrxCoO3-x (LSC), La
1-xSrxMnO3-x (LSM) ja Gd1-xSrxCoO3-x (GSC) electrode materials have perovskite structure and very good crystallinity. Also, any unwanted phases (for example carbonates) were not detected. For LSC and GSC, electrochemical in situ X-ray diffraction data show that temperature, oxygen partial pressure and negative electrode potential have noticeable and nearly reversible influence on the crystallographic cell volume of perovskite-type cathode materials. The crystallographic unit cell volume increases with the increase of negative electrode potential at fixed oxygen partial pressure and temperature. This effect is more expressed at lower oxygen partial pressure value. At lower oxygen partial pressure in cathode compartment, the influence of negative potential of cathode is more remarkable, which could be explained by lower oxygen chemical potential at lower oxygen partial pressures in gas phase and because of that more expressed release of oxygen from lattice is possible. For LSC and GSC, the increase of ionic radius of cobalt cation during reduction from Co4+ to Co3+ supports the increase of the unit cell size. For GSC cathode the kinetic measurements indicate that much longer time after exchange of applied potential is needed for achieving a new stable structure. It can be caused by Gd ion crystallographic parameters because Gd ion is heavier and smaller than La ion. There are no remarkable changes in LSM structure applying different electrode polarizations under in situ XRD conditions.
The electrochemical measurements show that most active cathode material is LSC. GSC is less active and LSM cannot be compared with two others, because LSM catalytic activity is low and it’s activity expressed only at higer temperatures.
Impedance spectroscopy data show that low and high frequency region processes rate depends on temperature.
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KASUTATUD KIRJANDUS
1. NEMA Standard, Publ. no. CV 1-1986, National Electrical MFgs. Assoc., New York 1986
2. S. C. Singhal, K. Kendall, High temperature solid oxide fuel cells: Fundamentals, design and applications / edited by Subhash C. Singhal and Kevin Kendall, Elsevier Ltd, Oxford, 2003, lk 1 design and applications / edited by Subhash C. Singhal and Kevin Kendall, Elsevier Ltd, Oxford, 2003, lk 5
6. J. M. Andujar, F. Segura, Fuel cells: History and updating. A walk along two centuries. Renewable and Sustainable Energy Reviews 13 (2009) 2309-2322
7. A. Weber, E. Ivers-Tiffée, Materials and concepts for solid oxide fuel cells (SOFCs) in stationary and mobile applications. Journal of Power Sources 127 (2004) 273-283 8. Fergus W J, Hui R, Li X, Wilkinson D P, Zhang J, Solid Oxide Fuel Cells: Materials, Properites and Performance, Green Chemistry and Chemical Engineering, CRC Press, New York, 2009, lk 133-149
9. S. C. Singhal, K. Kendall, High temperature solid oxide fuel cells: Fundamentals, design and applications / edited by Subhash C. Singhal and Kevin Kendall, Elsevier Ltd, Oxford, 2003, lk 98-99
13. A. Lasia, Electrochemical Impedance Spectroscopy and Its Applications in Modern Aspects of Electrochemistry, B. E. Conway, J. Bockris, and R.E. White, Edts., Kluwer Academic/Plenum Publishers, New York, 1999, Vol. 32, lk 143-248
36
14. N. P. Bansal, Z. Zhong, Combustion synthesis of Sm0.5Sr0.5CoO3-x and La0.6Sr0.4CoO3-x nanopowders for solid oxide fuel cell cathodes. Journal of Power Sources 158 (2006) 148-153
15. I. Kivi, E. Anderson, P. Möller, G. Nurk, E. Lust, Influence of Microstructural Parameters of LSC Cathodes on the Oxygen Reduction Reaction Parameters. Journal of the Electrochemical Society 159(11) (2012) F743-F750
16. V. G. Sathe, A. V. Pimpale, V. Siruguri, S. K. Paranjpe, Neutron diffraction studies of provskite-type compounds La1-xSrxCoO3 (x = 0.1, 0.2, 0.3, 0.4, 0.5). Journal of electroreduction kinetics. Electrochemistry Communications 10 (2008) 1455-1458 20. E. Lust, G. Nurk, S. Kallip, I. Kivi, P. Möller, Electrochemical characteristics of Ce0.8Gd0.2O1.9|La0.6Sr0.4CoO3-δ + Ce0.8Gd0.2O1.9 half-cell. Journal of Solid State Electrochemistry 9(10) (2005) 674-683
21. E. Lust, P. Möller, I. Kivi, G. Nurk, S. Kallip, P. Nigu, K. Lust, Optimization of the cathode composition for the intermediate-temperature SOFC. Journal of the Electrochemical Society 152(12) (2005) A2306-A2308
22. I. Kivi, J. Aruväli, K. Kirsimäe, A. Heinsaar, G. Nurk, E. Lust, Oxygen stoichiometry in La0.6Sr0.4CoO3−δ and La0.6Sr0.4Co0.2Fe0.8O3−δ cathodes under applied potential as a function of temperature and oxygen partial pressure, measured by novel electrochemical in situ high-temperature XRD method. Journal of the Electrochemical Society 160(9) (2013) F1022-F1026
23. M. M. Kuklja, E. A. Kotomin, R. Merkle, Yu. A. Mastrikov, J. Maier, Combined theoretical and experimental analysis of processes determining cathode performance in solid oxide fuel cells, Phys. Chem. Chem. Phys. 15 (2013) 5443
24. R. D. Shannon, Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides, Acta Cryst. A32 (1976) 751
25. E. Lust, P. Möller, I. Kivi, G. Nurk, S. Kallip, Electrochemical characteristics of La0.6Sr0.4CoO3−δ, Pr0.6Sr0.4CoO3−δ, Gd0.6Sr0.4CoO3−δ, Ce0.85Sm0.15O0.1925 electrolyte.
Journal of Solid State Electrochemistry 9 (2005), 882-889
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26. A. Feldhoff, J. Martynczuk, M. Arnold, M. Myndyk, I. Bergmann, V. Šepelak, W.
Gruner, U. Vogt, A. Hähnel, J. Woltersdorf, Spin-state transition of iron in (Ba0.5Sr0.5)(Fe0.8Zn0.2) O3−δ perovskite. Journal of Solid State Chemistry 182 (2009) 2961-2962
Lihtlitsents lõputöö reprodutseerimiseks ja lõputöö üldsusele kättesaadavaks tegemiseks
Mina ALAR HEINSAAR____________________________
(autori nimi)
(sünnikuupäev: 22.02.1992 )
1. annan Tartu Ülikoolile tasuta loa (lihtlitsentsi) enda loodud teose
„Erinevate tahkeoksiidkütuseelemendi katoodide võreparameetrite sõltuvus potentsiaalist, hapniku osarõhust ja temperatuurist in situ mõõtmistingimustel“
(lõputöö pealkiri)
mille juhendaja on INDREK KIVI____________________________, (juhendaja nimi)
1.1. reprodutseerimiseks säilitamise ja üldsusele kättesaadavaks tegemise eesmärgil, sealhulgas digitaalarhiivi DSpace-is lisamise eesmärgil kuni autoriõiguse kehtivuse tähtaja lõppemiseni;
1.2. üldsusele kättesaadavaks tegemiseks Tartu Ülikooli veebikeskkonna kaudu, sealhulgas digitaalarhiivi DSpace´i kaudu alates 31.12.2016 kuni autoriõiguse kehtivuse tähtaja lõppemiseni.
2. olen teadlik, et nimetatud õigused jäävad alles ka autorile.
3. kinnitan, et lihtlitsentsi andmisega ei rikuta teiste isikute intellektuaalomandi ega isikuandmete kaitse seadusest tulenevaid õigusi.
Tartus
25.05.2015