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Effect of Ionic Transport and Separation on the Meniscus in Molten Carbonate Electrolyte
Author(s) -
Hsieh P. H.,
Chen C. C.,
Selman J. R.
Publication year - 2012
Publication title -
fuel cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.485
H-Index - 69
eISSN - 1615-6854
pISSN - 1615-6846
DOI - 10.1002/fuce.201100125
Subject(s) - surface tension , wetting , electrolyte , meniscus , dewetting , adsorption , polarization (electrochemistry) , chemical physics , chemistry , ionic bonding , cationic polymerization , chemical engineering , materials science , thermodynamics , electrode , ion , analytical chemistry (journal) , composite material , chromatography , organic chemistry , optics , physics , incidence (geometry) , engineering
Migrational separation due to differences in cationic mobility is commonly observed during current passage in molten carbonate mixtures, and this might be responsible for the improved wetting observed upon polarization, as found experimentally according to the literature. To check this, a 2D transport model based on concentrated‐solution theory was applied to analyze the movement of ions in and near the meniscus. The effect of differences in cationic mobility and of ionic transport in general on current distribution, reaction rate, and electrolyte composition in the meniscus region was quantified, and corresponding surface tension gradients over the meniscus surface predicted. The resulting surface tension gradients were found to be too small to account for the experimentally observed meniscus rise. It is, therefore, concluded that the polarization effect on electrode wetting is not due to the gradient of surface tension caused by cationic separation. A plausible alternative explanation is that a gradient of the S/L interfacial tension exists but that this is due to specifically adsorbed intermediate reaction products, in particular oxides. Such a current density dependent adsorption layer would be in dynamic equilibrium with the local melt composition, and, thereby, drive the wetting/dewetting of the electrode surface that is experimentally observed.