Wetting Kinetics of Molten Carbonate on Carbon

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 (Li₂CO₃-Na₂CO₃-K₂CO₃, 43.5:31.5:25.0, molar ratio) on the carbon substrate at 450-750 °C under controlled atmospheres (100%Ar, 100%CO₂, and 1%O₂-99%N₂). 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 O₂ 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%O₂-99%N₂ 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.