Complex Formation during Dissolution of Metal Oxides in Molten Alkali Carbonates

Abstract

Dissolution of metal oxides in molten carbonates is of importance because of its relationship to the stability of the electrode and construction materials for molten carbonate fuel cells (MCFC).The earlier investigations on MCFC, up to 1970s, were concentrated on silver for both anode and cathode. It was shown, however, that silver was unsuitable for long-term use due to its high solubility in the carbonate melt under cathode-side conditions. 1,2 NiO, in the lithiated form for high conductivity, still seems to be the most promising material for the MCFC cathode. It is, however, unlikely to attain a lifetime more than 40,000 h because of its solubility in the carbonate melt. Several investigations have been carried out to measure the solubility of NiO in individual alkali carbonates, 3 binary mixtures, 4-7 ternary mixtures, 8,9 and alkali/alkaline earth carbonate mixtures. 10,11 In order to obtain other materials as possible substitutes for the lithiated NiO cathode, extensive research has been conducted. Among the numerous candidates of pervoskite-type compounds and mixed metal oxides, the chemistry of CuO,

Recent Developments on Molten Salt Synthesis of Inorganic Nanomaterials: A Review

“…Solubility of metal oxides in molten salts depends on the closeness in various physicochemical properties between solute and solvent such as electronegativity, polarizability, nature of bonding, common ion effect, etc . Solubility of various metal oxides in molten salts has been investigated previously using several thermodynamic and potentiometric methods. − …”

Flux-mediated crystal growth of metal oxides: synthetic tunability of particle morphologies, sizes, and surface features for photocatalysis research

“…The solubilities of metal oxides in molten fluxes have been previously studied using thermodynamic and potentiometric determination methods. [43][44][45][46][47][48][49][50][51][52] The use of fluxes with the same cations as the desired metal-oxide typically yields phase-pure crystals as a result of the similar chemical bonding, coordination site preference electronegativity, and crystal radii. As a general guideline, the hard-soft acid-base (HSAB) theory can be used to predict the solubility of inorganic reactants in molten-salt fluxes.…”

High solubility pathway for the carbon dioxide free production of iron

“…Furthermore, the solubility was reported as an invariant of the fraction of Li 2 CO 3 and K 2 CO 3 in these lithium/potassium carbonate mixtures. 7 These low solubility studies, of interest to the optimization of molten carbonate fuel cells, have likely discouraged research into the electrowinning of iron metal from ferric oxide in molten lithium carbonate.…”