Poly(phenylene oxide)-based membranes in anion exchange membrane fuel cellsE4. Materials for Energy Harvesting and Conversion
1 Applied Electrochemistry, KTH Royal Institute of Technology, Stockholm, Sweden
2 Department of Chemistry, Lund University, Lund, Sweden
Introduction/Purpose: Anion exchange membrane fuel cells (AEMFCs) are promising as potentially low-cost energy converters in a carbon neutral future. One of the key components in AEMFCs is the polymer electrolyte membrane. The purpose of this study is to extend the understanding of important in-situ membrane properties such as water flux, water permeability, in-situ conductivity and overall fuel cell performance of poly(phenylene oxide)(PPO)-based polymers with varying side chain and functional groups.
Methods: The electrochemical performance was studied using potentiodynamic sweeps and electrochemical impedance spectroscopy at saturated and 90% RH conditions, using in-house electrodes  and solvent cast membranes . The water transport properties were evaluated using humidity sensors and studied both in humidified inert gases and at fuel cell conditions under load .
Results: The results shown in Fig. 1, show the general performance of the cells under fully humidified conditions. The thin membrane with long side chain (PPO5) and high IEC 1.9 has superior performance. It was shown that the difference in performance cannot be fully explained either by water flux properties or cell resistance. However, both high back-diffusion and high conductivity enhance performance, especially for polymers with a longer side chain (PPO5) that have high water uptake. The results indicate that the interaction between electrode and membrane materials affect more than just increasing the cell resistance.
Conclusions: The results show that the PPO-membranes have comparable conductivity and water transport properties as the commercial Tokuyama membrane during AEMFC operation. However, further studies are needed to understand which membrane properties are most important for improved performance.
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