In-plane Mass Transport in Polymer Electrolyte Membrane Electrolyzer Porous Transport Layers with Through Pores

The mass transport in porous transport layers (PTLs) with pores exclusively in the through-plane direction was investigated using in operando X-ray radiography and electrochemical performance analysis. We observed via synchrotron X-ray imaging that through pores that are under the lands are inaccessible by liquid water. We thereby observed the limited in-plane mass transport that takes place in PTLs with pores exclusively in the through-plane direction. Additionally, a thicker layer of gas was observed with the use of the PTL with through pores under both the channels and the lands (PTLCh,L) when compared to the PTL with through pores only under the channels (PTLCh). This corresponded to the PTLCh,L exhibiting a higher mass transport overpotential than the PTLCh. Finally, the limited in-plane mass transport in the PTL with through pores led to a relatively dehydrated catalyst layer and higher ionic resistance with increasing current density.