Compression-induced hysteresis and degradation of titanium porous transport layers in PEM water electrolysers

• A novel compression hysteresis test for PEM water electrolyzers is introduced and validated. • The influence of PTL structure and Pt-coating on mechanical and electrochemical hysteresis is revealed. • A comprehensive degradation analysis is performed using µ-CT, SEM, contact angle, and EIS. The porous transport layer (PTL) in proton exchange membrane water electrolysis (PEMWE) accounts for approximately 17–25% of total stack cost and its durability and structural stability are crucial for system performance and lifetime. Due to the harsh conditions on the anode, corrosion-resistant titanium fiber or sintered PTLs are required. However, the mechanical behavior of these materials under compression and in particular under varying conditions, remains insufficiently understood. In this study, a mechanistic understanding of compression-induced performance hysteresis in titanium PTLs through in-situ stress tests and ex-situ mechanical and structural characterization is acquired. Fiber-based and sintered Ti-PTLs, with and without Pt coating, were subjected to cyclic compression during PEMWE operation to evaluate the evolution of contact behavior, performance, and morphology. Results show a compression-induced performance hysteresis and irreversible deformation and degradation. Fiber PTLs show greater initial performance but are more prone to permanent compaction, while sintered PTLs maintain structural rigidity but exhibit less adaptive contact formation. Platinized PTLs generally demonstrate higher resistance to mechanical fatigue. This work provides practical guidance for PEMWE stack assembly and PTL selection and thereby enables the definition of compression boundaries and PTL architecture recommendations. This allows to minimize mechanical fatigue and extend PEMWE operational durability, therefore supporting more cost-effective and robust clean hydrogen production.