In-Plane Transport in Water 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 concurrent in operando X-ray radiography and electrochemical performance analysis. We observed via synchrotron X-ray imaging that through pores situated under the lands are inaccessible to 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 higher content of product gas was observed with the use of the PTL with through pores under both the channels and the lands (PTL_Ch,L) when compared to the PTL with through pores only under the channels (PTL_Ch). This oxygen gas accumulation behaviour corresponded to the higher mass transport overpotential of the PTL_Ch,L compared to the PTL_Ch. Finally, the limited in-plane mass transport in the PTL with through pores led to a relatively dehydrated catalyst layer, which was exhibited through higher ionic resistances as a function of increasing current density.