Electrochemical study of ion transfer across the polypyrrole membrane between two electrolyte solutions

Abstract

In this paper, the electrochemical behaviour of the transfer of monovalent cations across the polypyrrole membrane (PPM) between two electrolyte solutions has been investigated by cyclic voltammetry with a four-electrode system, and the apparent ionic permeability through the membrane for some cations such as H⁺, Na⁺, K⁺ and NH⁺₄ has been found. The transfer process depends on ion size, ionic charge and surface characteristics of the membrane. The polarized membrane in a fixed direction is capable of controlling the ionic permeability and the ion transfer across the membrane is directional. The charged PPM acts as a one-way ion switch. When the switchable potential is reached, considerable ion transfer occurs and the electrochemical behaviour behaves as a totally irreversible process observed at the metal electrode/electrolyte solution interface. The effect of the membrane and solution resistances on the ion transfer behaviour is discussed and the transfer mechanism through the polypyrrole membrane is suggested. An asymmetrical ion-channel model can be used to explain the ion-transfer phenomenon at the PPM between two electrolyte solutions.