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, C2O2-5 . To investigate the similar reaction that could occur with CO and CO23 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. 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. ? 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

First-principles simulations were used to study the solvation of molecules and ions in molten carbonate electrolysis cells, focusing on CO2 and CO reactions. CO2 was found to form a pyrocarbonate species, while CO could form a stable oxalate species with CO23. O2- was observed to preferentially form a complex with four lithium cations, and CO showed the fastest diffusion among the studied species.