Subramanian V, Zhu Hongwei, Vajtai Robert, Ajayan P M, Wei Bingqing
Department of Electrical and Computer Engineering and Center for Computation and Technology, Louisiana State University, Baton Rouge, LA 70803, USA.
J Phys Chem B. 2005 Nov 3;109(43):20207-14. doi: 10.1021/jp0543330.
The effect of varying the hydrothermal time to synthesize manganese oxide (MnO(2)) nanostructures was investigated along with their influence on structural, morphological, compositional, and electrochemical properties in supercapacitor electrode materials. XRD and TEM studies showed that the MnO(2) prepared in shorter hydrothermal dwell time was a mixture of amorphous and nanocrystalline particles, and there was an evolution of crystallinity of the nanostructures as the dwell time increased from 1 to 18 h. Interestingly, SEM, TEM, and HRTEM revealed a variety of structures ranging from nanostructured surface with a distinct platelike morphology to nanorods depending upon the hydrothermal reaction time employed during the preparation of the manganese oxide: increasing the amount of individual nanorods in the materials prepared with longer hydrothermal reaction time. The surface area of the synthesized nanomaterials varied from 100 to 150 m(2)/g. Electrochemical properties were evaluated using cyclic voltammetry (CV) and galvanostatic charge-discharge studies, and the capacitance values were in the range 72-168 F/g depending upon synthesis conditions. The formation mechanism of the nanorods and their impact on the specific capacitance were discussed in detail.
研究了改变水热时间对合成氧化锰（MnO₂）纳米结构的影响，以及它们对超级电容器电极材料的结构、形态、组成和电化学性能的影响。X射线衍射（XRD）和透射电子显微镜（TEM）研究表明，在较短水热停留时间制备的MnO₂是无定形和纳米晶体颗粒的混合物，并且随着停留时间从1小时增加到18小时，纳米结构的结晶度有所演变。有趣的是，扫描电子显微镜（SEM）、透射电子显微镜（TEM）和高分辨率透射电子显微镜（HRTEM）显示，根据氧化锰制备过程中采用的水热反应时间，会出现从具有明显板状形态的纳米结构表面到纳米棒等各种结构：在较长水热反应时间制备的材料中，单个纳米棒的数量增加。合成纳米材料的表面积在100至150 m²/g之间变化。使用循环伏安法（CV）和恒电流充放电研究评估了电化学性能，根据合成条件，电容值在72 - 168 F/g范围内。详细讨论了纳米棒的形成机制及其对比电容的影响。
