Complex formation during dissolution of metal oxides in molten alkali carbonates

Qingfeng Li, Flemming Borup, Irina Petrushina, Niels Bjerrum

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    Dissolution of metal oxides in molten carbonates relates directly to the stability of materials for electrodes and construction of molten carbonate fuel cells. In the present work the solubilities of PbO, NiO, Fe2O3,and Bi2O3 in molten Li/K carbonates have been measured at 650 degrees C under carbon dioxide atmosphere. It is found that the solubilities of NiO and PbO decrease while those of Fe2O3 and Bi2O3 remain approximately constant as the lithium mole fraction increases from 0.43 to 0.62 in the melt. At a fixed composition of the melt, NiO and PbO display both acidic and basic dissolution as the partial pressure of carbon dioxide varies. By combination of solubility and electromotive force measurements, a model is constructed assuming the dissolution involves complex formation. The possible species for lead are proposed to be [Pb(CO3)(2)](-2) and/or [Pb(CO3)(3)](-4). A similar complex chemistry for nickel oxide dissolution might be expected. (C) 1999 The Electrochemical Society. S0013-4651(98)11-017-0. All rights reserved.
    Original languageEnglish
    JournalJournal of The Electrochemical Society
    Issue number7
    Pages (from-to)2449-2454
    Publication statusPublished - 1999

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    Copyright The Electrochemical Society, Inc. [1999]. All rights reserved. Except as provided under U.S. copyright law, this work may not be reproduced, resold, distributed, or modified without the express permission of The Electrochemical Society (ECS).

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