Interstitial Cobalt in Pt Shell of Pd@Pt Mesoporous Core–Shell Nanospheres with Strong d–d Orbital Hybridization for Enhanced Electrocatalytic Ammonia Oxidation

Ammonia oxidation reaction (AOR) is critical for efficient ammonia utilization as a hydrogen carrier, yet state-of-the-art Pt-based catalysts suffer significant activity loss due to strong ^*NO_x species (^*NO, ^*NO₂) adsorption. Herein, Pd@Pt mesoporous core-shell nanospheres with interstitial Co in Pt shell (Pd@Pt-Co MCSN) are demonstrated as an excellent AOR electrocatalyst, which achieves a mass activity of 293.6 A g^-1 at 0.7 V versus RHE, 4.8-fold higher than commercial Pt/C. The interstitial Co dopant tunes the d-d orbital hybridization state, optimizes the Pt d-band center position, and facilitates electron transfer from Co to Pt, which effectively weakens the adsorption of toxic ^*NO_x and lowers the energy barrier for N-N coupling. When integrated into a Zn-NH₃ battery, the catalyst enables efficient NH₃-to-H₂ conversion with a Faradaic efficiency of 96.8% and stable operation for 30 hours at 12 mA cm^-2. The work may provide a new design concept to develop advanced electrocatalysts for AOR.