Polarization Effects on Meniscus Characteristics in Molten Carbonate

Abstract

Meniscus heights on a gold flag electrode partially submerged in Li/K carbonate (62/38 mole percent) at 650~ have been determined under a variety of O=-CO= gas mixtures at atmospheric pressure. The meniscus height as a function of electrode potential shows a characteristic minimum for each gas composition and a relatively steep increase with increasing cathodic polarization. Analysis of the near-equilibrium data, assuming electrocapillary effects only, shows that this is consistent with specific adsorption of oxide ion on the electrode. At appreciable polarization, mass-transfer effects as well as adsorption appear to play a role, and the approach to steady-state conditions following a disturbance is slow.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-06-13 to IP

Electrowetting of Molten Carbonate Electrolytes

“…This equation is derived from the condition of mechanical equilibrium between the interfacial tension (capillary) forces and the force associated with the hydrostatic pressure. This equation has been applied by Selman and co-workers [3,4,7] to analyse the meniscus height data at potentials very close to the equilibrium potential (open circuit potential, OCP), where nearequilibrium in the thermodynamic sense may be assumed.…”

“…Matsumura and Selman [3] used optical observation of the meniscus rise on vertical plate to study the effects of current passage and gas composition on wetting and spreading at a gold electrode. Mugikura and Selman [4] measured the contact angle values under oxidant and reducing atmospheres and used these results to estimate the change of electrolyte distribution in the MCFC under load.…”

“…Tanimoto et al [10][11][12] observed that the addition of alkaline earth carbonate effectively reduces the solubility of NiO in the electrolyte and improves the endurance of the fuel cell. From small cell testing, the lifetime was increased 15-20% by a 9 mol.% addition of CaCO 3 or BaCO 3 to a Li/Na eutectic melt under pressurised conditions. Scaccia [13] reported that the addition of 3 mol.% of (SrCO 3 -BaCO 3 ) to Li/Na eutectic carbonate reduced the solubility by half compared to that obtained without additives.…”

Wetting of polarized materials by molten carbonate

“…Similarly as in such curves, the potential of maximum contact angle (potential of zero charge) does not coincide with the open circuit potential. As discussed earlier [3], only the part near the OCV can be interpreted as an electrocapillary curve.…”

“…In all cases, the dependence of the contact angle on polarization was examined and analyzed, over a range of temperatures. In earlier publications from this laboratory [1,3,4] extensive data on the wetting characteristics of simple alkali carbonate eutectics have been reported.…”