Conductive Mechanism of Low-Pt-Coated Porous Transport Layers at Key Interfaces in Proton Exchange Membrane Water Electrolyzers.

Proton exchange membrane water electrolyzers (PEMWEs) are key for renewable hydrogen production, featuring two critical charge transport interfaces: porous transport layer/catalyst layer (PTL/CL) and PTL/flow field (PTL/FF). To study interface charge transport, three Pt-loaded PTL anodes were combined with a normal or low-loading membrane electrode. Normal loading: optimized Pt boosts catalyst use; low loading: thinnest coating removes PTL/CL passivation. Notably, at low loading and low current density (<0.3 A cm-2), when charge barriers exist at the PTL/CL interface, an uneven Pt coating fails to improve PTL/FF conductivity and instead introduces additional barriers─an effect that diminishes with optimized coating or increased current density. The charge barrier at the PTL/CL interface amplifies the negative effects at the PTL/FF interface; this effect can be mitigated by applying a uniform coating or increasing the current. These findings provide guidance for optimizing platinum-coated PTLs and for studying charge transport at the PTL/FF interface.