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Crystalline Mesoporous K2–xMn8O16 and ε‑MnO2 by Mild Transformations of Amorphous Mesoporous Manganese Oxides and Their Enhanced Redox Properties

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journal contribution
posted on 23.07.2014 by Altug S. Poyraz, Wenqiao Song, David Kriz, Chung-Hao Kuo, Mohammad S. Seraji, Steven L. Suib
Synthesis of crystalline mesoporous K2–xMn8O16 (Meso-OMS-2), and ε-MnO2 (Meso-ε-MnO2) is reported. The synthesis is based on the transformation of amorphous mesoporous manganese oxide (Meso-Mn-A) under mild conditions: aqueous acidic solutions (0.5 M H+ and 0.5 M K+), at low temperatures (70 °C), and short times (2 h). Meso-OMS-2 and Meso-ε-MnO2 maintain regular mesoporosity (4.8–5.6 nm) and high surface areas (as high as 277 m2/g). The synthesized mesoporous manganese oxides demonstrated enhanced redox (H2-TPR) and catalytic performances (CO oxidation) compared to nonporous analogues. The order of reducibility and enhanced catalytic performance of the samples is Commercial-Mn2O3 < nonporous-OMS-2 < Meso-Mn2O3 < Meso-OMS-2 < Meso-ε-MnO2 < Meso-Mn-A.