Particle Size Control of Cryptomelane Nanomaterials by Use of H2O2 in Acidic Conditions

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• 作者：Josanlet C. Villegas ; Luis J. Garces ; Sinue Gomez ; Jason P. Durand ; and Steven L. Suib
• 刊名：Chemistry of Materials
• 出版年：2005
• 出版时间：April 5, 2005
• 年：2005
• 卷：17
• 期：7
• 页码：1910 - 1918
• 全文大小：419K
• 年卷期：v.17,no.7(April 5, 2005)
• ISSN：1520-5002

文摘

A new soft-step chemistry method has been developed to prepare pure cryptomelane-type manganeseoxide materials (OMS-2) with the smallest particle sizes ever reported. The synthetic procedure is basedon the reduction of KMnO₄ by H₂O₂ under acidic conditions followed by reflux. An acetate-containingbuffer solution and HNO₃ are used to control the pH of the reaction mixture. The formation process,particle size, crystallite size, crystal structure, and properties of these nanomaterials have been investigatedby X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy(HRTEM), potentiometric titration, thermogravimetric analysis, and N₂ sorption analyses. Both theconcentration of H₂O₂ and the nature of the acid used affect the crystalline phase formation, microstructure,thermal stability, and the composition of the final product. HRTEM images reveal that the OMS-2nanofibers are not oriented preferentially and present significant twinning, along with discontinuity inthe growth of the tunnel. Catalytic studies of these OMS-2 nanomaterials for oxidation of benzyl alcoholand fluorene have been performed. These nanomaterials show a low performance for the oxidation ofbenzyl alcohol and a unique catalytic activity for the oxidation of fluorene compared to OMS-2 materialsprepared by conventional methods.