Porosity‐Zoned Porous‐Transport Layer for Proton‐Exchange Membrane Water Electrolysis by High‐Velocity Flame Spraying

The porous‐transport layer (PTL) is a crucial component in proton‐exchange membrane water electrolyzers (PEMWE) enabling water and gas transport as well as electrically contacting the catalyst layer (CL). To reduce the overall costs of PTLs, a fabrication method by high‐velocity oxy‐fuel (HVOF) spraying is introduced. Free‐standing PTLs are obtained via the application of a titanium coating onto a substrate and its subsequent separation and thermal treatment. The obtained PTLs feature two sides of different roughness and porosity as analyzed and visualized by X‐ray microscopy. This way, the side with decreased porosity (21%) is intended to function as a microporous layer, improving the contact with the CL. The presented fabrication process promises decreased costs compared to vacuum plasma spraying, a simplified, chemical‐free mechanical separation of the PTL from the substrate, and a high scale‐up suitability. In the results, it is demonstrated that HVOF can produce titanium PTLs with low oxygen content. Additionally, PEMWE single‐cell tests demonstrate that the sprayed PTLs perform on par with a commercially available PTL material.