The poisoning effects of Ti-ion from porous transport layers on the membrane electrode assembly of proton exchange membrane water electrolyzers

The performance degradation of proton exchange membrane (PEM) electrolyzers has posed a challenge for their commercial applications. Herein, the long-term performance of a PEM electrolyzer with a sintered titanium fiber felt as the porous transport layer (PTL) at the anode side has been examined. The distribution of relaxation times (DRT) calculation reveals that the degradations mainly come from the increased ohmic resistance and polarization resistances related to proton transfer and charge transfer at the cathode. For the first time, Ti-ion has been found to accumulate in the cathode catalyst layer, as a result of Ti-PTL corrosion at the anode and subsequent Ti ion migration under the electric field. After continuously removing the foreign ions in the water loop with ion exchange resin, the degradation rate decreased by 71%. On the other hand, the increase in anode potential is primarily attributed to the rise in contact resistance of the Ti-PTL. The anode performance has almost fully recovered after the installation of a new Ti-PTL.