Ion transport in a non-isothermal electrokinetic energy conversion system

Abstract

Membranes with charged micro/nano pores are adopted widely to serve as a platform for extracting renewable energy from nature. Since almost all the physicochemical properties of the associated system are temperature-dependent, adopting a non-isothermal system, with energy needed coming from, for example, waste heat, has the potential to improve its performance. In this study, the ionic transport in a cylindrical nanopore subject to simultaneously applied pressure and temperature gradients is investigated, taking account of the surface reactions of the nanopore. Three non-isothermal models are compared with their streaming current and membrane potential. We show that the surface charge density of a nanopore is influenced appreciably by the temperature profile, which induces an electric field inside the nanopore that affects significantly the ionic transport. In the most general model, where both the heat transfer of membrane material and the surface reactions are considered, applying temperature and pressure gradients with opposite directions yields larger streaming current and membrane potential, that is, a better energy conversion performance.