Synergistic effect of flow field and porous transport layer matching on mass transfer and early-stage degradation mitigation in PEMWE under high operating current densities

• The matching of FF and PTL significantly influenced mass transfer efficiency and early-stage stability of PEMWE. • The accumulation of bubbles in the electrolyzer led to reversible voltage losses. • The irreversible voltage loss was attributed to structural changes in ACL. • M−S250 showed the best initial performance (1.808 V) at current density of 3 A/cm 2 . • S-S250 exhibited the lowest degradation rate of −108 µV/h after 168 h of stability test at current density of 3 A/cm 2 . Proton-exchange membrane water electrolysis (PEMWE) experiences mass transfer limitations at high current densities, resulting in an increase in voltage. To mitigate these losses, this study presents a comprehensive investigation into the synergistic effect of flow field (FF) and porous transport layer (PTL) matching on mass transport, as well as early-stage degradation, in PEMWE operating at high current densities. Six electrolyzers are constructed by matching the serpentine flow field (SFF) and titanium mesh flow field (TMFF) with three types of PTLs, including titanium felts with varying thicknesses and porosities, as well as sintered titanium. These electrolyzers are evaluated for initial performance and early-stage stability over 168 h at a current density of 3 A/cm 2 . The results demonstrate that the matching of the FF and PTL significantly alters the mass transport pathway and the degree of bubble accumulation inside the electrolyzer, contributing to a rise in reversible mass transfer voltage losses. A severe bubble accumulation could disrupt the structure of the anode catalyst layer (ACL), leading to irreversible voltage losses. The M−S250 (TMFF/sintered titanium) exhibits the best initial performance (1.808 V@3 A/cm 2 ), however, the accumulation of bubbles within the FF and PTL during operation leads to a degradation rate of 42 µV/h. In contrast, the S-S250 (SFF/sintered titanium) demonstrates superior performance with a minimal degradation rate of −108 µV/h, attributed to favorable topology and a shorter mass transfer pathway. These findings provide valuable insights into the design of PEMWE electrolyzers, with an emphasis on achieving “low degradation and high stability” under high operating current densities.