Manganese Oxides with Rod-, Wire-, Tube-, and Flower-Like Morphologies: Highly Effective Catalysts for the Removal of Toluene

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• 作者：Fang Wang ; Hongxing Dai ; Jiguang Deng ; Guangmei Bai ; Kemeng Ji ; Yuxi Liu
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2012
• 出版时间：April 3, 2012
• 年：2012
• 卷：46
• 期：7
• 页码：4034-4041
• 全文大小：595K
• 年卷期：v.46,no.7(April 3, 2012)
• ISSN：1520-5851

文摘

Nanosized rod-like, wire-like, and tubular 伪-MnO₂ and flower-like spherical Mn₂O₃ have been prepared via the hydrothermal method and the CCl₄ solution method, respectively. The physicochemical properties of the materials were characterized using numerous analytical techniques. The catalytic activities of the catalysts were evaluated for toluene oxidation. It is shown that 伪-MnO₂ nanorods, nanowires, and nanotubes with a surface area of 45鈥?3 m²/g were tetragonal in crystal structure, whereas flower-like spherical Mn₂O₃ with a surface area of 162 m²/g was of cubic crystal structure. There were the presence of surface Mn ions in multiple oxidation states (e.g., Mn³⁺, Mn⁴⁺, or even Mn²⁺) and the formation of surface oxygen vacancies. The oxygen adspecies concentration and low-temperature reducibility decreased in the order of rod-like 伪-MnO₂ > tube-like 伪-MnO₂ > flower-like Mn₂O₃ > wire-like 伪-MnO₂, in good agreement with the sequence of the catalytic performance of these samples. The best-performing rod-like 伪-MnO₂ catalyst could effectively catalyze the total oxidation of toluene at lower temperatures (T_50% = 210 掳C and T_90% = 225 掳C at space velocity = 20鈥?00 mL/(g h)). It is concluded that the excellent catalytic performance of 伪-MnO₂ nanorods might be associated with the high oxygen adspecies concentration and good low-temperature reducibility. We are sure that such one-dimensional well-defined morphological manganese oxides are promising materials for the catalytic elimination of air pollutants.