Carbon Species Solvated in Molten Carbonate Electrolyser Cell from First-Principles Simulations

We study the solvation of molecules and ions that are key in the context of Molten Carbonate Electrolyser Cells using first-principles simulations. Focusing on the electroreduction of CO2 to CO in a molten carbonate medium, we investigate the solvation of both the reactant CO2 and the product CO in the eutectic LiKCO3, (containing 62 % Li2CO3, 38 % K2CO3,). CO2 is found to spontaneously react with the carbonate ions to form the transient pyrocarbonate species, C2O52-. To investigate the similar reaction that could occur with CO and CO32- to form an oxalate, we simulated that species and found it to be stable in the melt, supporting this hypothesis. We further present the solvation of O2-, finding that it shows preferential formation of a complex with four lithium cations in a tetrahedral arrangement. Estimates of the diffusion coefficients of these species are then reported, showing that CO has the faster diffusion of all the molecules and ions studied.