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

Abstract 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 Pt 86 Ir 5 Rh 9 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 Pt 86 Ir 5 Rh 9 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.