Linking Surface Reconstructions to Catalytic Selectivity on Pt(100) during Ammonia Oxidation

This study addresses the longstanding challenge of optimizing platinum catalysts for industrial ammonia oxidation─a reaction central to nitrogen-based chemical synthesis─by uncovering the dynamic link between surface structure and selectivity under realistic conditions. Using a combination of operando surface X-ray diffraction, crystal truncation rod analysis, and near-ambient pressure X-ray photoelectron spectroscopy, we exposed Pt(100) to reaction conditions and observed the formation of an epitaxial Pt 3 O 4 (001) phase during initial oxidation, followed by distinct (10 × 10) and hexagonal surface reconstructions as active phases, dictated by the p O 2 / p NH 3 pressure ratio. Critically, surface roughness emerged as a key descriptor: smooth surfaces under low oxygen conditions drive N 2 selectivity, while roughened surfaces at high oxygen favored NO production, revealing how structural evolution governs catalytic behavior. These insights not only advance fundamental understanding of structure–function relationships in platinum catalysis but also provide a framework for designing industrially robust catalysts through precise surface engineering.