Polymer Electrolyte Membranes from Microporous Troger’s Base Polymers for Fuel Cells

Abstract

Fuel cells (FCs) have attracted much attention because of their high energy conversion efficiency and cleanliness. However, polyelectrolytes are a key component of FCs, and their cost and performance are not ideal at present, which is an obstacle to the development of FCs. Polymers of intrinsic microporosity (PIM) have attracted much attention as a class of membrane materials due to their three-dimensional pore structure, which can provide channels for ion transport. However, it remains challenging to prepare PIM membranes due to their poor solubility and brittleness. A novel soluble Troger’s base (TB)-PIM polymer is proposed in this paper. The prepared TB-based membranes with rigid and contorted backbones exhibit excellent dimensional stability (<8% swelling ratio at 60 °C), mechanical properties, and thermal stability and form subnanometer cavities to allow rapid ion transport. Therefore, the proton conductivity of the 4-(2-hydroxyethoxy)-1,3-phenylenediamine dihydrochloride (HEPD)/4,4′-diamine-3,3′-dimethyl-biphenyl (DMBP)-TB membrane is 58.3 mS/cm at 80 °C. The OH– conductivity of the HEPD/DMBP-QTB anion exchange membrane (AEM) is 105.9 mS/cm at 80 °C. Moreover, the single cell assembled with an HEPD/DMBP-QTB AEM showed a peak power density of 76.6 mW/cm2 in H2 air (CO2-free) at 60 °C.