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 (Eon-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 Eon-set, while nitrogenous adsorption strength dictates peak current density (jpeak). 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.