Virtual voids method to generate low-density microporous carbon structures using quenched molecular dynamics simulation

Abstract

The creation and properties of porous carbons are of extreme importance for optimizing the performance of battery and supercapacitor electrodes, as well as vehicular hydrogen storage. Atomistic simulation methods with reactive potentials have shown promise to create realistic porous carbon structures. However, such models have been unable to reproduce low-density microporous carbon structures due to clustering of atoms in high density regions, resulting in a small number of mesopores. Here we present a new method using virtual voids, generating excluded volume by a soft repulsive potential which is progressively decoupled from the carbon atoms. This allows us to prevent densification and to create disordered carbon models with porosities up to 90%. We vary the size and density of the virtual voids and show that the mean of the pore size distribution and the accessible surface area can be controlled. By choosing the desired porosity and virtual void size, we create amorphous carbon models with mean pore sizes ranging from 10 to 32 Å, which agree favorably with experimental pore sizes for low-density microporous carbons.