Wetting Kinetics of Molten Carbonate on Carbon

Abstract

The wettability of molten carbonate on carbon determines the electrochemical performances of high-temperature direct carbon fuel cells (DCFCs). However, a universal method to measure the high-temperature wettability of molten carbonate is absent and the wetting kinetics is not well understood. Herein, we develop a dispensed drop (DD) method to measure the wetting kinetics of molten carbonate (Li 2 CO 3 −Na 2 CO 3 −K 2 CO 3 , 43.5:31.5:25.0, molar ratio) on the carbon substrate at 450−750 °C under controlled atmospheres (100%Ar, 100%CO 2 , and 1% O 2 −99%N 2 ). The measured contact angles under different conditions reveal that increasing the O 2− concentration in the gas−liquid−solid (GLS) interface decreases the contact angle. In addition, elevating the temperature, introducing O 2 in the gas atmosphere, or pretreating the carbon substrate can enhance the wetting kinetics of molten carbonates. The molten carbonate completely wets the carbon substrate in 150 min in Ar gas atmosphere and in 30 min in 1%O 2 −99%N 2 gas atmosphere at 600 °C. Further, it takes only 30 min to completely wet the pretreated carbon substrate in Ar atmosphere at 600 °C. Overall, this paper offers the DD method to study the wettability of molten carbonate on the carbon substrate, which is helpful to understand the underlying wetting mechanism and engineer the electrode design for DCFCs.

Wetting Kinetics of Lithium–Sodium Orthoborate on Nickel and Stainless Steel under CO2-Lean and Saturated Conditions

“…Mugikura and Selman reported on the influence of the oxide-ion activity on the contact angle in carbonate melts, mentioning a selective adsorption of O 2– on metallic surfaces, resulting in the adherence of the melt to the metal and thereby a decrease in the observed contact angle. − The importance of the oxide-ion activity in the wetting kinetics of molten carbonates has also been brought up elsewhere . Following these studies, the behavior observed in Figure can be better understood.…”

Influencing Factors and Challenges on the Wettability of Electrode in Molten Salt

“…Therefore, interface wetting is a reaction-induced dynamic wetting process. 69 Chen et al used graphite rods as working electrode to study the wetting behavior of carbon in the DCFC anode environment in molten carbonate and CO 2 atmospheres. Since graphite is more polarized in ionic liquids, the molten carbonate will not wet the original carbon surface.…”

“…Schematic of the wetting mechanism of the molten ternary carbonate on the carbon surface in different gas atmospheres. 69 using components to predict the surface tension of a single or multicomponent liquid metal becomes possible, which is mentioned in 3.1.2.…”

“…Figure9. Schematic of the wetting mechanism of the molten ternary carbonate on the carbon surface in different gas atmospheres 69. …”

Total exfoliation of graphite in molten salts

“…The various microstructures, obtained due to salt impregnation into the graphite, are driven by the molten salt wettability thermodynamics at high temperature, while the salt is in molten state. 70,71 The molten salts that were characterized by low values of surface tension and small contact angles (CsCl and KCl, Fig. 1) formed dense homogeneous composites (Fig.…”