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Catalytic Oxidation of CO on a Curved Pt(111) Surface: Simultaneous Ignition at All Facets through a Transient CO-O Complex*.

Fernando Garcia-MartinezCarlos García-FernándezJuan Pablo SimonovisAdrian HuntAndrew WalterIradwikanari WaluyoFlorian BertramLindsay R MerteMikhail ShipilinSebastian PfaffSara BlombergJohan ZetterbergJohan GustafsonEdvin LundgrenDaniel Sánchez-PortalFrederik SchillerJosé Enrique Ortega
Published in: Angewandte Chemie (International ed. in English) (2020)
The catalytic oxidation of CO on transition metals, such as Pt, is commonly viewed as a sharp transition from the CO-inhibited surface to the active metal, covered with O. However, we find that minor amounts of O are present in the CO-poisoned layer that explain why, surprisingly, CO desorbs at stepped and flat Pt crystal planes at once, regardless of the reaction conditions. Using near-ambient pressure X-ray photoemission and a curved Pt(111) crystal we probe the chemical composition at surfaces with variable step density during the CO oxidation reaction. Analysis of C and O core levels across the curved crystal reveals that, right before light-off, subsurface O builds up within (111) terraces. This is key to trigger the simultaneous ignition of the catalytic reaction at different Pt surfaces: a CO-Pt-O complex is formed that equals the CO chemisorption energy at terraces and steps, leading to the abrupt desorption of poisoning CO from all crystal facets at the same temperature.
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