Mechanistic Similarity in Catalytic N₂Production from NH₃and NO₂–at Pt(100) Thin Films: Toward a Universal Catalytic Pathway for Simple N-Containing Species, and Its Application toin SituRemoval of NH₃Poisons

Understanding of the NH 3 oxidation poisoning mechanism at Pt(100) is key to tackling a drawback of a reaction important to wastewater decontamination, electrochemical NH 3 sensors, and NH 3 fuel cells. Here we present a detailed study of poisoning adsorbates generated by NH 3 at Pt(100) thin films and identify new key species (1) by comparison to NO 2 – reduction adsorbates and (2) using literature FTIR and DEMS (differential electrochemical mass spectrometry) data. We show that NH 3 and NO 2 – generate identical intermediates at the same electrochemical potentials, suggesting that reactions as disparate as NH 3 oxidation and NO 2 – reduction follow a universal catalytic pathway for N-containing compounds at Pt(100). This represents a significant paradigm shift from 45 years of thought that suggested the two pathways were completely separate. We then use the behavior of poisoning, adsorbed intermediates to develop an in situ cleaning procedure that allows improvements in performance and lifetime for NH 3 electro-oxidation technologies. The in situ cleaning procedure, demonstrated for 1200 cleaning cycles over 2 h, required neither H 2 production nor Pt oxide formation. The latter trait allowed the employment of Pt(100) films without risk of immediate catalyst deorientation to a polycrystalline state.