Microscopic insights on the degradation of a PEM water electrolyzer with ultra-low catalyst loading

The present work aims for a comprehensive understanding of the degradation of proton exchange membrane water electrolyzer (PEMWE) with a low catalyst loading of 0.3 mg cm−2 Pt and 0.08 mg cm−2 Ir after a long-term test of 4500 h at 1.8 A cm−2. For the first time, the mechanism of cathode degradation is proposed using established physical models from two aspects: (1) Pt dissolution from nanoparticles and (2) Pt dissolution due to rapid Pt oxide reduction at the start of operation. As Ir dissolves and migrates through the membrane, Pt-Ir precipitates are formed in the membrane. Furthermore, iridium dissolution and subsequent re-deposition on the cathode constitute a major portion (42%) of the anode catalyst loss. The overall picture of degradation mechanisms and the distribution of platinum and iridium across the membrane electrode assembly (MEA) are provided.