Spin-Polarized PdCu-Fe 3 O 4 In-Plane Heterostructures with Tandem Catalytic Mechanism for Oxygen Reduction Catalysis.

Alloying has significantly upgraded the oxygen reduction reaction (ORR) of Pd-based catalysts through regulating the thermodynamics of oxygenated intermediates. However, the unsatisfactory activation ability of Pd-based alloys toward O ₂ molecules limits further improvement of ORR kinetics. Herein, the precise synthesis of nanosheet assemblies of spin-polarized PdCu-Fe ₃ O ₄ in-plane heterostructures for drastically activating O ₂ molecules and boosting ORR kinetics is reported. It is demonstrated that the deliberate-engineered in-plane heterostructures not only tailor the d-band center of Pd sites with weakened adsorption of oxygenated intermediates but also endow electrophilic Fe sites with strong ability to activate O ₂ molecules, which make PdCu-Fe ₃ O ₄ in-plane heterostructures exhibit the highest ORR specific activity among the state-of-art Pd-based catalysts so far. In situ electrochemical spectroscopy and theoretical investigations reveal a tandem catalytic mechanism on PdCu-Fe ₃ O ₄ ─Fe sites that initially activate molecular O ₂ and generate oxygenated intermediates being transferred to Pd sites to finish the subsequent proton-coupled electron transfer steps.
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