A Generalized Theory of Ion Conductivity in Nanoporous Media

Ion conductivity in nanoporous media underpins energy storage, water purification, materials characterization, and subsurface sensing, yet classical transport theories fail at the nanoscale by neglecting interfacial phenomena. Using high-throughput non-equilibrium molecular dynamics with a reduced-complexity surface-chemistry model, we systematically vary pore size, surface charge, and ion affinity, and apply an electric field to probe nanoscale ion dynamics from zero-field diffusion to strongly driven conduction. This reveals three distinct dynamical regimes: confinement-driven linear response in charge-neutral pores, trap-and-hop nonlinear response in charged nanopores, and an interfacial superionic regime characterized by collective ion migration along percolation networks. We propose an extended Nernst-Einstein relation that unifies these diverging transport regimes through dimensional homogeneity, validated against all-atom simulations and experimental data. This development links interfacial physics to emergent ion-transport properties, thereby providing physics-based constitutive relations for nanoporous media.