On the origin of permanent performance loss of anion exchange membrane fuel cells: Electrochemical oxidation of phenyl group

• Published in: Journal of power sources 2019-10, Vol.436 (C), p.226866, Article 226866
• Main Authors: Maurya, Sandip, Lee, Albert S., Li, Dongguo, Park, Eun Joo, Leonard, Daniel P., Noh, Sangtaik, Bae, Chulsung, Kim, Yu Seung
• Format: Article
• Language: English
• Subjects: Alkaline; Durability; Fuel cells; Oxidation; Phenol formation
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2019.226866

The durability of alkaline anion exchange membrane fuel cells (AEMFCs) is a critical requirement for implementing this technology in cost-effective energy conversion. However, the lifetime of current AEMFCs is short, ca. < 1000 h and the cause of the performance loss over time is poorly understood. Here, we investigate the origin of AEMFC unrecoverable performance loss. We diagnosed the recoverable performance loss induced by carbonation and anode flooding during an extended-term test with transient operating conditions. Multiple extended-term tests under current densities and the electrochemical and analytical analyses suggest that the most prominent permanent performance loss of AEMFCs occurs by phenol formation as a result of electrochemical phenyl oxidation of cathode ionomeric binder. The produced phenol is acidic and neutralizes the quaternary ammonium group to lower the local pH. Finally, the impact of this degradation pathway is discussed to explain the reported lifetime performance of current AEMFCs. [Display omitted] •Explained the degradation behavior of anion exchange membrane fuel cells.•Provided spectroscopic evidence of phenyl oxidation at the ORR potential.•Identified the origin of permanent performance loss of AEMFCs: phenol formation.•Suggested possible mitigation strategies to prevent undesirable phenol formation.