Influence of the Porous Transport Layer Surface Structure on Overpotentials in PEM Water Electrolysis

The engineering of porous transport layer (PTL)–catalyst layer (CL) interfacial architecture plays a critical role in optimizing the performance of proton exchange membrane water electrolyzers (PEMWEs). Particularly, at the PTL-CL interface, our results reveal that anode catalyst loadings affect the modulation of the PTL surface structure on the overpotentials of PEMWEs. Under high anode catalyst loadings, the magnitude of overpotentials is predominantly governed by the electronic conductivity and mass transport resistance within the CL, where the modifying effects of PTL-CL interfacial contact characteristics become negligible. However, when the catalyst loading is reduced, the PTL-CL interfacial contact characteristics become critical for electron conduction, mass transport, and kinetic reaction. Under low catalyst loadings, the etched PTL demonstrates a maximum reduction of 59 mV compared to the pristine PTL at 4 A/cm2, with the former exhibiting a 10 mΩ·cm2 reduction. Meanwhile, the etched PTL integrated with a cell demonstrates superior performance in both mass transport and kinetic overpotentials compared to a pristine PTL. This clearly indicates that the surface structure of the PTL plays an increasingly significant role in regulating the overpotentials of PEMWEs as the catalyst loadings decrease.