Disentangling Degradation Mechanisms of Noble Metal-Coated Titanium Porous Transport Layers for Water Electrolyzers.

The shift toward a carbon-neutral society hinges on efficient green hydrogen production through proton exchange membrane water electrolysis. While noble metal (especially platinum (Pt))-coated titanium (Ti)-based porous transport layers (PTLs) offer superior robustness, the Pt coating remains unstable under harsh operating conditions. We established a three-electrode evaluation platform that enables precise control over potential, temperature, and pH, allowing a systematic investigation on PTL. Electrochemical and surface analyses reveal that degradation behavior varies with temperature and pH following three mechanisms: (i) defect-induced physical detachment, (ii) Pt particle agglomeration, and (iii) Pt surface passivation. Degradation proceeds most rapidly when passivation and corrosion occur in a balanced manner, with potential pulses of 5 s duration inducing the most severe deterioration. Furthermore, we highlight that short- and long-term degradation follow distinct mechanisms. This study provides a comprehensive understanding of noble metal-coated Ti PTL degradation, presenting essential design principles for developing highly durable electrolyzer components.