Ultra-Low-Temperature Ozone Abatement on α-MnO2(001) Facets with Down-Shifted Lowest Unoccupied Orbitals

Abstract

Extraordinary catalytic performance at ultralow temperatures is energetically desirable for ozone converters equipped on commercial passenger aircrafts, but it remains a great challenge to achieve it. Here we synthesized sheet-shaped α-MnO2 exposing a large percentage of reactive (001) facets, on which low-valence surface manganese ions and abundant surface oxygen vacancies act as catalytic sites. Compared with α-MnO2 rods, α-MnO2 sheets exhibited exceptional catalytic activity in ozone decomposition even at −55 °C due to the abundant catalytic sites. By using Mn L3-edge absorption spectroscopy and the frontier orbital theory, we found that α-MnO2 sheets have down-shifted lowest unoccupied Mn 3d orbitals with respect to β-MnO2, which enables electrons to transfer from peroxide intermediates to catalytic sites more easily, thus accelerating the reaction rate even at very low temperatures in the stratosphere.