Mn3O4 doped with highly dispersed Zr species: a new non-noble metal oxide with enhanced activity for three-way catalysis

Abstract

In this article, zirconium-doped manganese oxides have been synthesized through a one-step solvothermal method and used in three-way catalysis. Zr⁴⁺ was introduced into the lattice of Mn₃O₄ and was shown to be highly dispersed in the Mn₃O₄ matrix, as confirmed by XPS, Raman spectroscopy and EDS-Mapping. Appropriate Zr⁴⁺ doping resulted in lattice distortion, leading to the exposure of more oxygen vacancies and a better oxygen storage capacity (OSC: 658.8 μmol g⁻¹) than pure Mn₃O₄ (163.2 μmol g⁻¹). As non-noble metal three-way catalysts (TWCs) for a CO + NO + C₂H₆ model reaction, the catalytic activities of the as-synthesized samples were evaluated. Notably, the catalytic tests showed that the activities of the zirconium-doped samples are higher than that of pure Mn₃O₄. Furthermore, the ZM-2 sample (with a 20% Zr/Mn molar ratio) shows the best complete conversion of CO at 228 °C, NO at 334 °C and C₂H₆ at 400 °C (nearly 100 °C lower than those of pure Mn₃O₄) and excellent anti-high temperature performance. Our work will reduce the use of precious metals and provide a feasible route to prepare economical catalysts for exhaust emission control.