Effects of Electrochemical Activation Methods on the Restructuring and Oxygen Reduction Performance of PtNi x “Core–Shell” Carbon‐Nitride/Carbon Supported Electrocatalysts

This work presents hierarchical PtNi 10 ‐CN l 900/H d electrocatalysts (ECs) for the oxygen reduction reaction (ORR), where “l” denotes low N (<5 wt%), “900” the final pyrolysis temperature in °C, and “H d ” the 1:1 Gr/C support. Their “core–shell” architecture combines defective graphene nanoplatelets (Gr) and Vulcan XC‐72R carbon black (C), exploiting complementary functions, with a carbon nitride (CN) “shell” coordinating PtNi x active sites. The common precursor P derives from a 3D‐crosslinked zeolitic inorganic‐organic polymer electrolyte (Z‐IOPE) embedding the nanocomposite carbon “core” and contains Ni‐rich, sub‐micrometric PtNi 10 domains. A flow‐through electrochemical setup activates P through reversible‐potential‐sweep (RS), constant‐potential (CP), and constant‐current (CC) methods. These elementary profiles are investigated as modular building blocks for specific EC systems. The recovered powders undergo extensive conventional physicochemical characterization and are incorporated into membrane‐electrode assemblies (MEAs) using conventional procedures. “Ex ‐situ” analyses demonstrate extensive Ni removal and restructuring toward Pt‐rich nanostructures, while rotating ring–disk electrode (RRDE) measurements reveal markedly higher ORR activity than Pt/C. Single‐cell proton‐exchange membrane fuel cell (PEMFC) testing reveals method‐dependent differences under transport‐sensitive high‐current conditions. CP provides the most favorable overall compromise and remains the most promising building block for custom, potentially scalable activation methods.