Ternary alkali carbonate composition-oxygen solubility relationship under atmospheric and pressurized conditions – a utility model for MCFC
Tóm tắt
The effect of O2/CO2 = 90/10 gas mixtures under pressurized conditions on the diffusion resistance during oxygen reduction was investigated in carbonate melts of variable composition ranging from the eutectics Li–K, Li–Na to ternary Li–Na–K carbonate melts. It was found that pressurization reduced the diffusion resistance of the reactant species in all compositions investigated. This was ascribed to the increase in concentration of the reactive species in the electrolyte. Reaction order plots of Warburg coefficient versus the total pressure in binary melts showed that: (i) mixed diffusion of superoxide ions and CO2 prevails in lithium rich carbonates, and (ii) mixed diffusion of peroxide ions and CO2 predominates in potassium rich carbonates. By means of a computerized statistical analysis of the results, a partial cubic model was found to describe the relationship between alkali carbonate compositions, pressure, and Warburg coefficient. The optimum alkali carbonate compositions are: (i) 0.283Li–0.373Na–0.344 K with σapp equal to 137.68 Ω cm2s−0.5 at atmospheric conditions, and (ii) 0.390Li–0.355 Na–0.255 K with σapp 87.53 Ω cm2 s−0.5 and 4.2 atm under pressurized conditions.
Tài liệu tham khảo
J.R. Selman, ‘Fuel Cell Systems’ (Plenum Press, New York, 1993).
L. Plomp, E.F. Sitters, J.P. Hujismans and S.B. van der Molen, in Proceedings of the Second Symposium on ‘Molten Carbonate Fuel Cell Technology’, PV 90-16, The Electrochemical Society, Pennington, NJ (1990), p. 247.
L. Plomp, J.B.J. Veldhuis, E.F. Sitters and S.B. Van der Molen, J. Power Sources 39 (1992) 369.
L. Giorgi, M. Carewska, E. Simonetti, S. Scaccia, F. Croce and A. Pozio, Molten Salt Forum 1–2 (1993/94) 285.
K-K. Young and Y-B. Young, Electrochim. Acta 43 (1998) 3343.
L. Giorgi, A. Moreno, A. Pozio and E. Simonetti, in Proceedings the Fifth Symposium on ‘Molten Carbonate Fuel Cell Technology’, PV 99-20, The Electrochemical Society, Pennington, NJ (1999), p. 265.
C. Belhomme, E. Gourba, M. Cassir and C. Tessier, J. Electroanal. Chem. 503 (2001) 69.
M. Mohamedi, Y. Hisamitsu, K. Kihara, T. Kudo, T. Itoh and I. Uchida, J. Alloys Comp. 315 (2001) 224.
K. Ota, S. Mistushima, S. ato, H. Yoshitake and N. Kamiya, J. Electrochem. Soc. 139 (1992) 667.
J.R. Selman and H.C. Maru, in G. Mamantov and J. Braunstein (Eds), ‘Advances in Molten Salt Chemistry’, Vol. 4 (Plenum Press, New York, 1981), p. 159.
H. Mohn and H. Wendt, Z. Physik. Chem. 192 (1995) 101.
T. Nishina, I. Uchida and J.R. Selman, J. Electrochem. Soc. 141 (1994) 1191.
M. Mohamedi, Y. Hisamitsu, Y. Ono, T. Itoh and I. Uchida, J. Appl. Electrochem. 30 (2000) 1397.
I. Uchida, T. Nishina, Y. Mugikura and K. Itaya, J. Electroanal. Chem. 206 (1986) 229.
I. Uchida, Y. Mugikura, T. Nishina and K. Itaya, J. Electroanal. Chem. 206 (1986) 241.
I. Uchida, T. Nishina, Y. Mugikura and K. Itaya, J. Electroanal. Chem. 209 (1986) 125.
A.J. Appleby and S.B. Nicholson, J. Electroanal. Chem. 112 (1980) 71.
K. Yamada, T. Nishina, I. Uchida and J.R. Selman, Electrochim. Acta 38 (1993) 2405.
G.B. Dunks and D. Stelman, Inorg. Chem. 22 (1983) 2168.
R. Makkus, Doctoral thesis, Delft University of Technology, Delft (1991).
T. Itoh, Y. Hisamitsu, M. Mohamedi, M. Nishizawa, T. Abe, P. Tomczyk and I. Uchida, Chem. Lett. (1999) 1115.
G.E.P. Box, W.G. Hunter and J.S. Hunter, ‘Statistics for Experimenters’ (Wiley & Sons, New York, 1978).