Chloride‐Induced Morphology Control of Pt Coatings on Titanium Porous Transport Layers for Proton Exchange Membrane Water Electrolyzers

Platinum coatings are widely applied on titanium porous transport layers (PTLs) to mitigate passivation and interfacial resistance in proton exchange membrane water electrolyzers (PEMWEs). However, with the commonly used electrodeposition process, it is still a challenge to form a uniform coating structure. In this work, chloride ions are introduced during the electrodeposition process to control the morphology of Pt coating on Ti felt. Distinct nanostructures of platinum are obtained by the addition of KCl, ranging from rose structure in chloride‐free electrolyte to cauliflower‐like clusters at low concentration, dense nanoflakes at moderate concentration, and stacked agglomerates at high concentration. The Pt nanoflake coating shows higher surface coverage and significantly reduced interfacial contact resistance and enhanced corrosion resistance, delivering superior voltage efficiency in the PEMWE single‐cell test compared to the commercial Pt‐coated PTL. Mechanistic insights are also explored to provide practical guidelines for the design of durable, high‐performance PTLs in water electrolysis.