Catalytic Oxidation of CO on a Curved Pt(111) Surface: Simultaneous Ignition at All Facets through a Transient CO-O Complex** |
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Authors: | Fernando Garcia-Martinez Dr Carlos García-Fernández Dr Juan Pablo Simonovis Adrian Hunt Dr Andrew Walter Dr Iradwikanari Waluyo Dr Florian Bertram Dr Lindsay R Merte Dr Mikhail Shipilin Sebastian Pfaff Dr Sara Blomberg Dr Johan Zetterberg Dr Johan Gustafson Prof Edvin Lundgren Prof Daniel Sánchez-Portal Dr Frederik Schiller Prof J Enrique Ortega |
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Institution: | 1. Centro de Física de Materiales CSIC/UPV-EHU-, Materials Physics Center, Manuel Lardizabal 5, 20018 San Sebastian, Spain;2. National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973 USA;3. Department of Physics, Lund University, 221 000 Lund, Sweden;4. Department of Chemical Engineering, Lund University, 221 000 Lund, Sweden |
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Abstract: | 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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Keywords: | CO oxidation curved surfaces ignition near-ambient pressure photoemission subsurface oxygen |
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