Terracing Oxyphilic Platinum Sustains High‐Rate Ammonia Electrolysis and Fuel Cells

The sluggish kinetics and catalyst poisoning of the ammonia oxidation reaction (AOR) pose technical barriers to adopting ammonia as a distributable carrier for green hydrogen and electricity. Herein, a class of PtIrRh nanowires (NWs, ≈1 nm diameter) is report with abundant terraces and oxyphilic doping for enhanced AOR electrocatalysis. It is first unravel, through size-dependent AOR activity, that well-coordinated terraces outperform under-coordinated steps on platinum, guiding the rational design of 1D architecture. The compositionally-optimized Pt₈₆Ir₅Rh₉ NWs achieve a mass activity of 324 A g^-1 _PGM at 0.6 V, alongside an on-set potential (E_on-set) of 0.41 V. Electrochemical studies coupling in situ attenuated total reflection Fourier transform infrared spectra establish voltammetry-accessible descriptors: surface oxyphilicity governs the E_on-set, while nitrogenous adsorption strength dictates peak current density (j_peak). In a membrane electrode assembly, the Pt₈₆Ir₅Rh₉ NWs enable ammonia electrolysis at 1 A cm^-2 with a cell voltage of 0.63 V-1 V lower than the typical value of water electrolysis, and drive a direct ammonia fuel cell to 339 mW cm^-2 at 0.4 V. The findings redefine Pt-based AOR catalyst design and advance ammonia-mediated hydrogen economy toward practicality.