Enhancement of soot oxidation activity of manganese oxide (Mn₂O₃) through doping by the formation of Mn_1.9M_0.1O_3–δ (M = Co, Cu, and Ni)

The current work describes the catalytic soot oxidation activity of metal-doped manganese oxide (Mn_1.9M_0.1O_3–δ; M = Co, Cu, and Ni) materials, synthesized by coprecipitation method. All the fabricated materials were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Brunauer–Emmett–Teller surface area analysis, and X-ray photoelectron spectroscopy (XPS). XRD analysis confirmed the formation of solid solution Mn_1.9M_0.1O_3–δ (M = Co, Cu, and Ni). M-doped samples exhibited different morphology when compared with pure Mn₂O₃ as evidenced by FESEM analysis, and Co-doped Mn₂O₃ possessed the highest specific surface area. XPS analysis revealed the presence of multiple oxidation states of Mn (+4, +3, and +2) and Co (+2 and +3). Soot oxidation activity tests, performed using thermogravimetric analysis, showed that Mn_1.9Co_0.1O_3–δ exhibited better catalytic performance (T₅₀ = 390°C) when compared with pure Mn₂O₃ (T₅₀ = 490°C). The incorporation of dopants greatly enhanced the oxygen vacancies and redox properties of Mn₂O₃.