Insights into the roles of surface oxygen species of manganese oxides
for the ozone elimination at ambient temperature
Abstract
Manganese oxides with varied Mn valance states but identical morphology
were synthesized. Their behaviors of ozone decomposition were
investigated following the order of Mn3O4 < Mn2O3 <
MnO2 < MnO2-H-200. It was deduced that the superior O3
decomposition capacity for MnO2-H-200 was strongly associated with
abundant oxygen vacancies. Among Mn3O4, Mn2O3 and MnO2, the difference
on O3 decomposition efficiency was dependent on divergent nature of
oxygen vacancy. DFT calculation revealed that Mn3O4 and MnO2 possessed
lower formation energy of oxygen vacancy, while MnO2 had the minimum
desorption energy of peroxide species (O2*), suggesting that the
promotion of the O3 decomposition capability was attributed to the
easier O2* desorption. The insights on the deactivation mechanism for
MnO2-H-200 further validated the assumptions. As the reaction proceeded,
adsorbed oxygen species accumulated on the catalyst surface, and a
portion of them were transformed to lattice oxygen.