Effect of operating conditions under wet and dry cathode feeding on aged anion exchange membrane water electrolyzer: Electrochemical insights from impedance and distribution of relaxation time

Anion exchange membrane water electrolysers (AEMWE) are a promising technology for hydrogen production. While most studies focus on catalysts and membrane development, the influence of operating conditions and water feeding strategies remains less explored, particularly in aged systems where degradation affects performance. To address this, an aged (>100 h, including 48 h under AST) 5 cm2 single cell AEMWE using a Ni-Fe-Co spinel anode, an Aemion (R) membrane, and a Pt/C cathode, was systematically tested and evaluated to determine optimal operating conditions. For the aged cell, the wet cathode configuration (WCC) exhibits a slightly lower cell voltage than the dry cathode configuration (DCC). To explain this result, distribution of relaxation times (DRT) analysis was performed, revealing five distinct processes associated with different physicochemical phenomena, further assigned using SEM and half-cell measurements. It is shown that the improved performance of WCC arises from enhanced hydrogen evolution reaction (HER) kinetics due to improved cathode hydration, whereas DCC promotes the oxygen evolution reaction (OER) through greater electrolyte availability at the anode. Despite exhibiting higher ohmic resistance, WCC achieves a lower overall cell voltage, indicating that kinetic benefits outweigh resistive losses, although with greater sensitivity to variations in operating conditions compared to DCC.