Proton exchange membrane water electrolysis (PEMWE) is one of the most promising technologies for green hydrogen production, although the long-term durability of membrane–electrode assemblies (MEAs) remains a major barrier to large-scale deployment. In this work, degradation behavior in PEMWE assemblies is comparatively discussed based on recent studies using Nafion™ N1110 and Nafion™ N115 membranes under controlled potentiostatic and galvanostatic operation at 60 °C (Tejera et al., 2024; Tejera et al., 2026). For the N1110-based MEA, assembled with Pt black at both electrodes, degradation during 168 h potentiostatic holds at 2.0 V was associated with a progressive decrease in current density, an increase in ohmic resistance, and longer electrochemical time constants, revealing deterioration in charge-transfer and transport processes. After regeneration in 1 M H₂SO₄, the MEA partially recovered its initial performance, and the degradation rate became approximately six times lower than before regeneration, suggesting that reversible contamination was a dominant contributor to the observed temporary performance losses (Tejera et al., 2024). For the N115-based MEA, which employed Pt black at the cathode and IrRuOx at the anode, potentiostatic operation at 2.0 V led to a current decay that stabilized near 204 μA h⁻¹ cm⁻², while galvanostatic operation required an additional ~50 mV over 168 h to sustain the target current, confirming progressive resistive degradation. Acid regeneration again produced partial recovery, but subsequent degradation accelerated to ~860 μA h⁻¹ cm⁻², indicating that regeneration could not prevent the accumulation of irreversible structural damage (Tejera et al., 2026). Overall, both studies demonstrate that PEMWE degradation results from a combination of reversible contamination and irreversible structural deterioration. While acid treatment can temporarily restore performance, the long-term response depends strongly on membrane–catalyst configuration and on the balance between interfacial, ohmic, and mass-transport degradation pathways (Tejera et al., 2024; Tejera et al., 2026).