Effect of 5% Ag on the morphology and toluene oxidation of MnO2 nanorod and sea urchin microspheres
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摘要:
采用水热法制备了MnO2纳米棒和海胆微球，并原位掺杂5%Ag制备了Mn-Ag复合氧化物，利用SEM、XRD、BET、Raman等表征技术对其结构进行表征，并考察不同催化剂对甲苯的去除性能。结果表明：(NH4)2S2O8的掺入量会对MnO2的形貌产生影响，当其掺入量为2.28 g时，形成MnO2纳米棒，当其掺入量为6.84 g时，形成MnO2海胆微球；MnO2纳米棒掺杂5%的Ag后，形貌未发生变化，但当MnO2海胆微球掺杂5%Ag时，表面的纳米线较MnO2海胆微球有所增长，且出现了缠绕现象，形成了空心鸟巢状结构；5%Ag掺杂后，对MnO2纳米棒和MnO2海胆微球的晶型未产生影响，均为α-MnO2，但5%Ag-MnO2纳米棒出现了Mn2O3的衍射峰；MnO2海胆微球较MnO2纳米棒的比表面积、孔径和孔容均增大，且Ag的掺杂进一步提高了MnO2海胆微球的比表面积、孔径和孔容；MnO2海胆微球比MnO2纳米棒具有更好的甲苯去除性能，且5%Ag掺杂后，MnO2海胆微球对甲苯的去除性能达到最好。
Abstract: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.
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Key words:
- MnO2 nanorod /
- MnO2 sea urchin microspheres /
- Ag doping /
- morphological effect /
- toluene removal
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图 1 不同形貌的Ag-Mn复合氧化物的SEM
Figure 1. SEM of Ag-Mn composite oxides with different morphologies
图 4 不同Ag-Mn复合氧化物对甲苯的氧化活性
Figure 4. Oxidative activity of different Ag-Mn composite oxides on toluene
图 5 不同Ag-Mn复合氧化物的N2吸附-脱附曲线和孔径分布
Figure 5. N2 adsorption-desorption curve and pore size distributions of different Ag-Mn composite oxides
表 1 不同Ag-Mn复合氧化物的T50和T90
Table 1. T50 and T90 of different Ag-Mn compiste oxides
℃ 样品 T50 T90 MnO2纳米棒 258.4 292.8 5%Ag-MnO2纳米棒 261.6 290.4 MnO2海胆微球 240.4 282.5 5%Ag-MnO2微球 214.5 237.7 
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表 2 不同Ag-Mn复合氧化物的比表面积和孔径
Table 2. Specific surface area and Pore Size of various Ag-Mn composite oxides
样品 比表面积/（m2/g） 孔径/nm 孔容/（cm3/g） MnO2纳米棒 10.89 18.63 0.051 5%Ag-MnO2纳米棒 8.08 21.62 0.044 MnO2海胆微球 51.40 22.86 0.294 5%Ag-MnO2微球 65.13 24.73 0.403
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