Current-voltage curves of bipolar membranes

Abstract

Bipolar membranes consist of a layered ion‐exchange structure composed of a cation selective membrane joined to an anion selective membrane. They are analogous to semiconductorp‐n devices as both of them present current‐voltage curves exhibiting similar rectificationproperties. In this article, we present some current‐voltage curves obtained for different bipolar membranes at several temperatures. The results can be interpreted in terms of a simple model for ion transport and field‐enhanced waterdissociation previously developed. The mechanism responsible for water splitting is assumed to be a catalyticproton transferreaction between the charged groups and the water at the membrane interface. The effects of temperature are taken into account by introducing an Arrhenius‐type relationship for the dependence of the forward rate constant of the reaction on temperature. Finally, comparison between theory and experiments provides reasonable values for the parameters introduced in the theoreticalmodel. The analysis aims at developing a better physical understanding of a process in which chemical reactions and transport phenomena are coupled in such a way that the potential technological applications depend strongly on this coupling.