Electrical Conductivity of Nanoscale Hydrophobic Porous Media: Surface Charge Density and Heterogeneous Pore Structure

TL;DR

This study develops a predictive model for the electrical conductivity of nanoscale hydrophobic porous media considering surface charge and pore heterogeneity, validated through molecular dynamics and effective medium theory.

Contribution

It introduces a combined approach using MD simulations, MPB model, and EMA to accurately predict nanoscale HPM conductivity with heterogeneous pore structures.

Findings

Surface charge density influences ionic density profiles.

Conductance increases with larger pore size and higher coordination number.

Conductance saturation occurs at very low electrolyte molarity.

Abstract

Electrical conductivity is an inherent property of a hydrophobic porous media (HPM) and has critical applications. This research aims to provide a solution for predicting the electrical conductivity of nanoscale HPM with heterogeneous pore structure. Molecular dynamics (MD) simulations are compared with the modified Poisson-Boltzmann (MPB) model for understanding ionic charge density distributions in nanopores. The effective medium approximation (EMA) participates in calculating the effective conductance and conductivity of the nanoscale HPM. The results show that the surface charge density affects the ionic density profiles in the hydrophobic nanopores. As the pore size increases, the conductance increases. As the molarity of the aqueous electrolyte solution (AES) decreases, the conductance decreases. A phenomenon related to the conductance saturation occurred when the molarity of AES is very low. The effective conductance of an HPM increase as the coordination number increases. Finally, based on the calculated effective conductance and the heterogeneous pore structure parameters, the electrical conductivity of a nanoscale HPM is calculated.