Item

Abstract

The activation of molecular oxygen is a fundamental step in almost all catalytic oxidation reactions.We have studied
this topic and the role of surface vacancies for Co₃O₄(100)
films with a synergistic combination of experimental and theoretical methods. We show that the as-prepared surface is Blayer terminated and that mild reduction produces oxygen single and double vacancies in this layer. Oxygen adsorption experiments clearly reveal different superoxide species below
room temperature. The superoxide desorbs below ca. 120 K from a vacancy-free surface and is not active for CO oxidation while superoxide on a surface with oxygen vacancies is stable
up to ca. 270 K and can oxidize CO already at the low temperature of 120 K. The vacancies are not refilled by oxygen
from the superoxide, which makes them suitable for long-term operation. Our joint experimental/theoretical effort highlights the relevance of surface vacancies in catalytic oxidation
reactions.