Dissolution of the Ti porous transport layer in proton exchange membrane water electrolyzers

The titanium porous transport layer (PTL) is a key component in proton exchange membrane water electrolyzers (PEMWEs), facilitating efficient water supply to the catalyst layer while rapidly removing oxygen bubbles. However, in the highly anodic operating environment of PEMWEs, the Ti PTL suffers from degradation, limiting the lifetime of the device. To gain deeper insights into Ti PTL degradation, here we monitor the potential/time-resolved Ti dissolution rates by coupling a PEMWE with an online inductively coupled plasma-mass spectrometer (ICP-MS). The results show that the dissolution of the Ti PTL is a complex and dynamic (electro)chemical event. Initiated by the decreased interfacial pH (even at pH < 1) due to proton accumulation during PEMWE operation, Ti dissolution intensifies with increasing bias potential. However, the dissolved Ti ions are simultaneously hydrolyzed, forming surface Ti oxides that slow down the dissolution rate. Coating the Ti PTL surface with Pt and IrO2 effectively reduces Ti dissolution, albeit at a higher cost, but they are also susceptible to dissolution during operation. Interestingly, the dissolution profiles of Pt and IrO2 deposited on the Ti PTL differ significantly from their conventional behavior, which requires further investigation for reliable prediction and optimization of new PTL designs for practical implementation in PEMWEs.