Crystal structure-determined oxygen vacancy content in MnOx directs synergistic ozone–formaldehyde co-purification efficiency

Abstract

Manganese oxides have been extensively utilised in the context of purifying indoor pollutants, including ozone and formaldehyde. The effect of the structure of manganese oxides on the catalytic performance remains to be elucidated. In this study, we have investigated the structures of MnO, Mn₃O₄, Mn₂O₃, and MnO₂, with a view to analyse the effect of the manganese oxide structure on oxygen vacancy generation. In manganese oxides with varying structures, the distinct coordination geometries of oxygen atoms influence the bonding energy of the Mn–O bond, thereby modulating the formation of oxygen vacancies. In manganese dioxide, oxygen atoms coordinate with up to three manganese atoms, resulting in lower Mn–O bond energy compared to other manganese oxides. This increases surface oxygen vacancy concentrations, promoting the conversion of intermediate products and enhancing catalytic activity. MnO₂ exhibited higher activity with the removal efficiencies of O₃ and HCHO maintained at 100% and 76%, respectively. This study offers novel insights into the design of highly efficient manganese-based catalysts for indoor pollutant removal.