Analysis of performance degradation during steady-state and load-thermal cycles of proton exchange membrane water electrolysis cells

A membrane-electrode assembly based on a 90 ?m short-side-chain Aquivion® proton exchange membrane and containing low catalyst loadings, 0.4 mg IrRuOx cm and 0.1 mg Pt cm at anode and cathode, respectively, is investigated for combined thermal and load cycling at high current density (3 A cm) in water electrolysis cell. Durability tests under steady-state and load-thermal cycles are compared to evaluate the efficiency losses under specific operating conditions. Ac-impedance spectra and post-operation analyses are carried out to investigate the degradation mechanism. Catalyst degradation occurs more rapidly under cycled operation whereas mass transfer issues are relevant especially under steady-state mode. Membrane thinning appears to be affected by the uptime hours at high current density. The overall cell voltage increase is slightly larger for the cycled operation compared to the steady-state mode. However, this is essentially related to a compensation effect associated to a larger decrease of series resistance during the steady-state durability test. The dynamic electrolysis mode at high current density does not exacerbate significantly the degradation issues of low catalyst loading MEAs compared to a steady-state operation. This confirms the proper dynamic characteristics of the polymer electrolyte membrane electrolyser.