Driving Adsorbate Evolution via Oxygenated Surface Species Modulation for Ammonia Electrooxidation

The electrochemical ammonia oxidation reaction (eAOR) to dinitrogen offers a promising pathway for sustainable nitrogen cycles and hydrogen generation. However, despite mechanistic insights into *NH_x dehydrogenation and OH⁻-mediated proton-coupled electron transfer, conventional metal catalysts, including Pt and Pt-Ir alloys, still suffer from sluggish kinetics and poor stability. Here, we report that controlling oxygenated co-adsorbates steers the adsorbate-evolution pathway of the eAOR to N₂. An exsolved Pt₃Ni alloy on a perovskite scaffold selectively stabilizes *OOH and strengthens *NH₂ binding via interfacial charge redistribution (elevated surface potential) and a raised Pt d-band center. In situ Fourier transform infrared spectroscopy combined with density functional theory reveals that both the *NH_x-to-*N dehydrogenation and *OOH formation steps critically affect the rate-determining process via the N₂H₄ pathway of the Gerischer–Maurer (G–M) mechanism. Benefiting from (oxy)hydroxide-assisted eAOR, the catalyst delivers mass activity up to 862 A g_Pt⁻¹, surpassing the state-of-the-art benchmarks. When deployed in a solar-driven ammonia electrolyzer, the catalyst achieves 13.7 mA at cell voltage of 1.0 V, and stable solar-driven hydrogen production at 394 L kWh⁻¹ (NH₃ removal rate of 62 mg/day) in landfill leachate-like wastewater conditions. These findings establish an absorbate-assisted mechanism design approach for developing advanced N-species electrocatalysis.