On the origin of deactivation of reversal-tolerant fuel cell anodes under voltage reversal conditions

• Published in: Journal of power sources Vol. 472; p. 228439
• Main Authors: Joo, Taigyu, Hu, Leiming, Hong, Bo Ki, Oh, Jong-Gil, Litster, Shawn
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2020
• Subjects: Carbon corrosion; Fuel cell durability; Hydrogen starvation; Reversal-tolerant anode; Reversal-tolerant anode; Carbon corrosion; Hydrogen starvation; Fuel cell durability
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2020.228439

Over the past decade, extensive efforts have been carried out to increase the durability of polymer electrolyte fuel cells (PEFCs) under voltage reversal conditions primarily caused by hydrogen starvation. One common strategy is the use of reversal tolerant anodes (RTAs) that incorporate oxygen evolution reaction (OER) catalysts (e.g., IrO2) to promote harmless water electrolysis over carbon oxidation and delay severe carbon support degradation. The present study investigates the RTA catalyst deactivation mechanism under hydrogen starvation conditions and the relative humidity (RH) dependence of the OER and carbon oxidation reactions to understand the relatively quick failure of an RTA at a high RH. The comparison of the OER durability of membrane electrode assemblies with and without carbon under hydrogen starvation conditions shows that the presence of carbon deactivates the OER catalyst through carbon oxidation species poisoning. The catalytic activity of IrO2 measured by the current density response shows a linear dependence on RH, while the rate of carbon oxidation reactions increases exponentially with RH, suggesting that the decreased durability of RTAs is related to the exponentially increased rate of carbon oxidation reactions. These findings can be used to design more robust electrodes for automotive fuel cells under hydrogen starvation conditions. [Display omitted] •IrO2 is chemically deactivated by carbon oxidation species.•Catalytic activity of IrO2 shows a linear dependence on relative humidity.•Carbon oxidation reactions increase exponentially with relative humidity.•Fast carbon oxidation reactions in water-excess conditions reduce IrO2 performance.