Tandem Catalysis for pH‐Universal Hydrogen Oxidation in Fuel Cells

ABSTRACT Minimizing platinum‐group metal (PGM) usage in anion‐exchange membrane fuel cells (AEMFCs) and proton‐exchange membrane fuel cells (PEMFCs) is essential for cost reduction. However, achieving power densities exceeding 1 W cm −2 requires high PGM loadings at the anode, particularly in AEMFCs (>0.1 mg cm −2 ), to sustain hydrogen oxidation reaction (HOR) kinetics. Nickel‐based catalysts offer a low‐cost alternative but are typically limited by poor activity and oxidative instability. Here, we address these limitations by developing a core–shell nanoreactor comprising Ni nanoparticles (NPs) encapsulated by N‐doped graphitic carbon (NC) that is embedded with atomic Ru and Ni species. With an ultralow Ru loading of 1 µg cm −2 , anodes using this catalyst deliver peak power densities of 2.36 and 3.26 W cm −2 in AEMFC and PEMFC, respectively, with negligible structure change after 200 h of continuous operation at 1 A cm −2 in both devices. Mechanistic studies in alkaline media reveal a tandem catalytic pathway in which NPs shielded from the electrolyte dissociate H 2 to H*, and adjacent atomic metal species enable H* spillover across the NC shell to react with surface‐anchored OH*. This work provides a general strategy for designing tandem electrocatalysts for multi‐step catalytic processes.