Transport and Conductive Mechanisms in Anion Exchange Membranes

Anion exchange membranes (AEMs) represent the key components in AEM fuel cell devices that generate clean power from H 2 /O 2 by using earth-abundant electrocatalysts. A significant research development has been focused on the material design and operability of AEMs for fuel cells and various other electrochemical devices like water electrolyzers and batteries. In fuel cell devices, the critical parameters for AEMs are their OH − ion conductivity and alkaline stability over a long period of time. In this chapter, a critical analysis of the OH − ion-conductive properties and the transport mechanism in AEMs, which is supported by theoretical model developments is provided. One of the main challenges in AEM fuel cells is to minimize the carbonation process which limits OH − conductivity of membranes. Although the chemical mechanisms in which carbonation lead to voltage loss in fuel cells are well known, little is understood in how those mechanisms are related to the properties of AEMs. Here, we present an overview on the dynamics of the carbonation process in AEMs along with the different methods to control the carbonation effects and determine the real OH − ion conductivity. The use of in situ electrochemical impedance spectroscopy for monitoring the changes in ionic conductive behavior of AEMs vs stability during fuel cell operations is thoroughly assessed. From a design perspective, various strategies to enhance the OH − conductivity are presented laying out the future research directions for the development of novel, high-performance AEMs for fuel cells and related technologies.