Facilitating hydroxide transport in anion exchange membranes via hydrophilic grafts

Abstract

Alkaline exchange membranes (AEMs) are a promising class of polyelectrolytes whose alkaline operating environment enables the use of non-precious metal catalysts in low-temperature fuel cells. However, their poor ionic conductivities, which are often an order of magnitude lower than traditional acidic membranes (e.g., Nafion), have limited their practicality. The performance problem can partially be ascribed to the poorly-defined morphologies of typical random copolymer AEMs, leading to tortuous ion transport pathways. Here, we show the ability to form nanoscale (5 to 10 nm diameter) anion transport channels by grafting hydrophilic poly(ethylene glycol) side-chains along a model benzyltrimethylammonium polysulfone-based AEM. Concomitant with the structure formation is a 100% increase in the IEC-normalized hydroxide conductivity from 20.2 mS g cm À1 mmol À1 to 40.3 mS g cm À1 mmol À1 as well as a 50% increase in the peak power density from 118 mW cm À2 to 180 mW cm À2 when incorporated into a fuel cell.

Configuring Anion‐Exchange Membranes for High Conductivity and Alkaline Stability by Using Cationic Polymers with Tailored Side Chains

“…The OH − conductivity at 60 °C increased from 40 mS cm −1 , for the non‐PEG functionalized AEM, to 48 and 63 mS cm −1 after the introduction of 12 wt% PEG side chains of 350 and 750 g mol −1 , respectively. All the AEMs degraded rapidly under alkaline conditions at 60 °C and the PEG side chains had only a marginal effect on the stability …”

Bicarbonate and chloride anion transport in anion exchange membranes

“…Fig. 3 demonstrates a surface with a cluster/island-like structures [28], where the islands represent the backbone of the membrane, and the surrounding represents the hydrophilic channels. These hydrophilic regions, with approximate diameter of 5-20 nm (see Fig.…”

Characterization of Anion Exchange Membrane Containing Epoxy Ring and C–Cl Bond Quaternized by Various Amine Groups for Application in Fuel Cells

“…The quaternized membranes were kept in 1 M KOH solution for 24 h and washed thoroughly with deionized water. Membranes were stored in a glass bottle filled with nitrogen gas and deionized water because hydroxide anions can transform into carbonate and bicarbonate species when they come into contact with carbon dioxide in the atmosphere [19]. Figure 1.…”