Magnesium manganese oxide nanoribbons: synthesis, characterization, and catalyti

2019-12-16 10:07:15

mg manganese oxide nanoribbons todorokite

责任者: Jia Liu;Jun Cai;Young-Chan Son;Qiuming Gao;Suib, S.L.;Aindow, M. 单位: Inst. of Mater. Sci., Connecticut Univ., Storrs, CT, USA 来源出处: Journal of Physical Chemistry B(J. Phys. Chem. B (USA)),26 Sept. 2002,106(38):9761-8 摘要: A todorokite-type magnesium manganese oxide molecular sieve material with a morphology of nanoribbons has been synthesized using a combination of techniques consisting of a sol-gel process to synthesize a nanosized tetraethylammonium manganese oxide layered material, an ion-exchange method to prepare a thin-film Mg-buserite (Mg-OL-1) precursor, and a hydrothermal reaction to transform the Mg-buserite to nanoribbonlike Mg-todorokite (Mg-OMS-1) material. The transformation of the Mg-buserite thin films to Mg-todorokite nanoribbons has been studied using XRD and TEM. XRD data indicate that the structural transformation of Mg-OL-1 to Mg-OMS-1 is completed after hydrothermal heating at 150°C for about 40 h and at 200°C for less than 8 h. TEM data show that the nanoribbons form at an early stage of the hydrothermal treatment, followed by the appearance of lattice fringes. TEM data also indicate that the well-formed nanoribbonlike crystals have a uniform tunnel dimension along the a axis and a long-range-ordered 3×3 tunnel structure along the b axis. FESEM data show that the lengths of the nanoribbons range from a few micrometers to tens of micrometers and that the widths range from 20 to 100 nm. Elemental and average oxidation state analyses indicate a formula for the nanoribbon of Mg2.11Mn5.46O12·xH2O. According to TGA and TPD-MS data, these nanoribbons are thermally stable up to 500°C. The BET surface area is 81 m2/g, which is higher than that of bulk todorokite synthesized using conventional methods. The catalytic performance of nanoribbonlike Mg-todorokite materials on converting benzyl alcohol to benzaldehyde was improved greatly as compared to that of bulk Mg-todorokite materials 关键词: catalysis;catalysts;chemical reactions;ion exchange;magnesium compounds;manganese compounds;nanostructured materials;scanning electron microscopy;sol-gel processing;transmission electron microscopy;X-ray diffraction;Mg-Mn oxide nanoribbons;synthesis;characterization;catalytic application;todorokite-type magnesium manganese oxide molecular sieve material;morphology;Mg2.11Mn5.46O12·xH2O;sol-gel process;nanosized tetraethylammonium manganese oxide layered material;ion-exchange method;Mg-buserite precursor thin film;X-ray diffraction;microscopy;structural transformation;lattice fringes;uniform tunnel dimension;nanoribbonlike crystals;long-range-ordered 3 × 3 tunnel structure;b axis;a axis;nanoribbon lengths;nanoribbon widths;150 C;200 C;40 h;8 h;500 C;Mg-Mn-O;Mg2.11Mn5.46O12-H2O