Tandem Catalysis for pH-Universal Hydrogen Oxidation in Fuel Cells

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 H₂ 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.