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

Abstract

The catalytic oxidation of CO on transition metals, such as Pt, is commonly viewed as asharp transition from the CO-inhibited surface to the active metal, covered with O. However,w ef ind that minor amounts of Oa re present in the CO-poisoned layer that explain why,surprisingly,COdesorbs at stepped and flat Pt crystal planes at once,r egardless of the reaction conditions.Using near-ambient pressure X-ray photoemission and ac urved Pt(111) crystal we probe the chemical composition at surfaces with variable step density during the CO oxidation reaction. Analysis of Cand Ocore levels across the curved crystal reveals that, right before light-off,subsurface Ob uilds up within (111) terraces.T his is key to trigger the simultaneous ignition of the catalytic reaction at different Pt surfaces:aCO-Pt-O complex is formed that equals the CO chemisorption energy at terraces and steps,l eading to the abrupt desorption of poisoning CO from all crystal facets at the same temperature.

A ferromagnetic Eu–Pt surface compound grown below hexagonal boron nitride

“…4). This curved Pt surface was cleaned by Ar ion sputtering (room temperature) and temperature annealing (1000 K) as well as by occasional oxygen heating (2 × 10 −8 mbar O 2 , 950 K) followed by a flash in UHV to 1050 K. This standard procedure, as described elsewhere, 51,52 leads to sharp LEED patterns where the typical step splitting was observed.…”