The First Durable Imidazolium-Based Radiation Grafted Anion Exchange Membranes for Alkaline Fuel Cells: The Impact of Water Management

Abstract

Recently, Radiation grafted anion exchange membranes (AEM) gained increasing interest for alkaline fuel cell applications due to their high performance such as the highest power density ever reported for alkaline fuel cells (>2W/cm2). 1 However, their durability under operating fuel cell conditions still the biggest challenge.2 In our group, several radiation grafted AEMs, having several imidizalium-based graft-polymers consisting of N-vinyl (NVIm), 2-methyl-1-vinyl- (NVMIm), 2-methyl-4-vinyl- (4VMIm), and 2-(4-ethenylphenyl)-imidazolium (2StIm) graft-polymers, have been developed.3,4 In this work, the durability of the membrane-electrode-assembly (MEA) consisting imidazolium based radiation grafting AEMs under the supply of H2 and O2 at 60 °C was investigated in comparison to the MAE with common benzyl trimethylammonium (BTMA) based membranes. The core of this study is to investigate the effect of water management and specifically the dew point of the flow gas at anode and cathode sides on the performance and durability of imidazolium based membranes. For example, by tuning the due points for NVMIm-AEM the maximum power density increased from 115 to 200 mW/cm2. On the other hand, In spite of the low durability of 4VMIm membranes under in-situ alkaline durability in solution,5 the 4VMIm retained 75 % of the initial voltage after 240 h under fuel cell conditions, that was more durable than BTMA-based MEA (Figure 1). This study reveals the main role of water management of AEMs not only on the performance but also on the membrane durability. The study discloses an alternative durable AEMs for the new generation of alkaline fuel cells and other energy applications.