Water – A key parameter in the stability of anion exchange membrane fuel cells

Anion exchange membrane fuel cells can potentially revolutionize energy storage and delivery; however, their commercial development is hampered by the chemical decomposition of the anion exchange membranes during operation. The hydroxide anions, while transported from the cathode to the anode, attack the positively charged functional groups in the polymer membrane, neutralizing it and suppressing its anion-conducting capability. In recent years, several new quaternary ammonium salts have been proposed to address this challenge, but while they perform well in ex-situ chemical studies, their performance is very limited in real fuel cell studies. While cation chemistry dictates the intrinsic chemical stability of the anion conducting ionomeric materials, it was recently shown that chemical degradation is significantly influenced by the hydration level at which the fuel cell operates. Understanding the principles governing the chemical degradation under fuel cell operation, and its critical relationship with the hydration levels in the operating fuel cell electrodes will facilitate the path to overcome the challenge and finally develop and demonstrate highly stable AEMFC devices.