Effect of 5% Ag on the morphology and toluene oxidation of MnO₂ nanorod and sea urchin microspheres

MnO₂ nanorod and sea urchin microspheres were prepared using the hydrothermal method, and Mn-Ag composite oxides were prepared by in-situ doping with 5% Ag. The as-prepared samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), BET, Raman and other characterization techniques, and the removal performance of different catalysts for toluene was investigated. It was found that the amount of (NH₄)₂S₂O₈ would affect MnO₂ morphology. MnO₂ nanorods were formed when (NH₄)₂S₂O₈ was 2.28 g, while MnO₂ sea urchin microspheres were formed when (NH₄)₂S₂O₈ was 6.84 g. There was no morphology change of MnO₂ nanorods after 5% Ag doping. However, the nanowires on the surface of MnO₂ sea urchin microspheres increased when 5% Ag was doped, and the entanglement phenomenon occurred, forming a hollow bird's nest structure. After 5% Ag doping, there was no effect on the crystal of MnO₂ nanorods and sea urchin microspheres, both of which were α-MnO₂, but a diffraction peak of Mn₂O₃ appeared in 5% Ag-MnO₂ nanorods. Compared to MnO₂ nanorods, MnO₂ sea urchin microspheres showed an increasing trend of specific surface area, pore size and pore volume. The doping of Ag further increased the specific surface area, pore size and pore volume of MnO₂ sea urchin microspheres. For the toluene removal, MnO₂ sea urchin microspheres showed a better toluene removal performance than MnO₂ nanorods, and 5% Ag-MnO₂ sea urchin microspheres showed the best toluene removal performance among all the catalysts.