Heat and mass transfer of molten carbonates at charged electrode interface and its anisotropic behavior: A molecular dynamics study

Abstract

Molten carbonates are broadly used in fuel cells with potential applications in reducing CO2 emission, while their heat and mass transfer properties near a charged electrode surface are less well understood. Using molecular dynamics (MD) simulations, the heat and mass transfer properties of molten Na2CO3-K2CO3 salts at charged nickel surfaces are revealed in this study. Simulation results indicates that when surface charge density increases, molten salt’s thermal transport exhibit anisotropic behavior: the interfacial thermal resistance show strong dependence on the surface charge while heat transfer parallel to surface is not sensitive to the surface charge. As for interfacial mass transfers, the shear viscosity of the carbonate tends to rise with external electric field, while the corresponding ion diffusion does not vary very much and exhibit position-dependent behavior. To further explore this, we find that the anisotropy of this heat and mass transfer properties is primarily attributed to the nonuniform ion distribution in the direction perpendicular to nickel surface with the increasing of charge, while the interatomic correlation does not vary much as surface charge increases. These results have suggested that the anisotropy of heat and mass transport properties of molten salt near electrode, which should be taken care of when modelling the macroscopic heat and mass transport of molten carbonate fuel cells in particular.