The Fe3+ role in decreasing the activity of Nafion-bonded IrO2 catalyst for proton exchange membrane water electrolyser.

Fe3+ is a common ion contaminant for the proton exchange membrane water electrolyser (PEMWE). In this work, three-electrode-system was employed to study the effect of Fe3+ on Nafion-bonded IrO 2 catalyst which is conventional anode catalyst for PEMWE. Study results showed that Fe3+ contamination decreased IrO 2 catalytic activity significantly only when the following two conditions were both satisfied: 1) Nafion resin exists in working electrode; 2) working electrode potential was over 1.471 V (vs. NHE) which is around the initial voltage of oxygen evolution reaction (OER). Besides, the contaminated working electrode activity was recovered to about 16% by being immersed into 3 M H 2 SO 4 solution, but it was recovered to about 59% by ethanol washing method. These study results revealed that Fe3+ plays a role of catalyst for H 2 O 2 production during OER process, which leads to Nafion resin decomposition. The degradation products covered working electrode surface, and thus decreased effective active sites of IrO 2. Nafion degradation was further confirmed by analyzing 1) F− content in anode water and 2) FTIR of contaminated Nafion membrane. • Fe3+ reduces IrO 2 activity significantly only when Nafion exists and E > 1.471 V. • Contaminated IrO 2 -Nafion WE was recovered to 16.1% by being immersed in 3M H 2 SO 4. • Contaminated IrO 2 -Nafion WE was recovered to 59% by ethanol washing method. • Nafion degradation products cover working electrode (WE) and reduce IrO 2 activity. • Fe3+ catalyzes the production of H 2 O 2 during OER process. [ABSTRACT FROM AUTHOR]