Theory of ion and water transport in electron-conducting membrane pores with pH-dependent chemical charge

Abstract

In this work, we develop an extended uniform potential (UP) model for a membrane nanopore by including two different charging mechanisms of the pore walls, namely by electronic charge and by chemical charge. These two charging mechanisms will generally occur in polymeric membranes with conducting agents, or membranes made of conducting materials like carbon nanotubes with surface ionizable groups. The electronic charge redistributes along the pore in response to the gradient of electric potential in the pore, while the chemical charge depends on the local pH via a Langmuir-type isotherm. The extended UP model shows good agreement with experimental data for membrane potential measured at zero current condition. When both types of charge are present, the ratio of the electronic charge to the chemical charge can be characterized by the dimensionless number of surface groups and the dimensionless capacitance of the dielectric Stern layer. The performance of the membrane pore in converting osmotic energy from a salt concentration difference into electrical power can be improved by tuning the electronic charge.

arXiv comment11 figures

References in corpus (6)

• The Charge of Glass and Silica Surfaces
• Analysis of electrolyte transport through charged nanopores
• Analysis of ionic conductance of carbon nanotubes
• Flow-induced surface charge heterogeneity in electrokinetics due to Stern-layer conductance coupled to reaction kinetics
• Induced Charge Capacitive Deionization: The electrokinetic response of a porous particle to an external electric field
• AC-Driven Electro-Osmotic Flow in Charged Nanopores