Modeling Ion Adsorption in Microporoux Carbons – MAICANANO

This program aims to bring the scientific and mathematical bases necessary for the understanding and the prediction of the mechanisms of transport and the adsorption of the ions of the electrolyte in confined nanopores, i.e., under conditions where the double electrochemical layer theory is no longer applicable.

The main objective is to depict the behavior of liquid electrolytes in a confined environment. A realistic atomic picture of such systems is of primary importance to explain the unexpected properties recently reported in the literature like the partial desolvation of the ions or the increase in the charge storage capability in pores of size lower than the nanometer. More generally, the results will impact all scientific and technical areas where ion transport in porous membranes with pore sizes equal or less to 2 nm plays a crucial role. Ion exchange membranes used for sea water desalination or organic membranes in human body are example among other that will be undirectly concerned.

To successfully conclude this work, we have chosen to treat this subject through the anomalous increase in charge storage capacitance in carbon nanopores, which was discovered by one of the consortium member. Therefore, the consortium combines a laboratory expert in syntheses and electrochemical characterizations of nanoporous carbons (CIRIMAT) to two laboratories specialized in molecular modelling (PECSA and IFP).

in a first step, we will model the transport of the ions in porous carbon structures with pore sizes equal or less than 1 nanometer, which are only accessible upon (partial) desolvation of these ions, to understand the desolvation mechanism and to explain the associated increase in the storage capacitance. From real experimental results obtained with model materials (CDCs, carbon nanotubes and Ionic Liquids) , molecular modeling will help in a) explaining the accessibility of the ions in the nanometer pores through the calculations of the relevant thermodynamic properties, and b) determining the ion size as well as its environment in these pores that can only be accessed by (partly) desolvation ions. Finally, the diffusive properties of the ions in the presence and the absence of an applied electric potential will also be determined, allowing for optimization of the charge / discharge time of the ECs.

The reliability of the coupled experimental /theoretical approach will be tested through the use of the models previously developed to define porous carbon structure with exalted charge storage capability. We will use the molecular simulations to select the carbon porous structures that are most adequate to achieve the highest capacitance by ion adsorption. These materials will then be prepared and tested.