Effect of Microwave on the Nanowire Morphology, Optical, Magnetic, and Pseudocapacitance Behavior of Co3O4
Effect of Microwave on the Nanowire Morphology, Optical, Magnetic, and Pseudocapacitance Behavior of Co3O4
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DOI：
10.1021/jp209165v
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发表时间：
2011-12-29
影响因子：
3.7
通讯作者：
Rao, G. Ranga
中科院分区：
文献类型：
--
作者：
Meher, Sumanta Kumar;Rao, G. Ranga
在合成方法对材料结构和功能特性具有极大控制作用的背景下，在均相沉淀条件下，采用常规回流法和微波辅助法合成了四氧化三钴（Co₃O₄）纳米线形貌。常规回流法合成的Co₃O₄样品由随机分布的细纳米线组成，而微波回流法生成了更高维度且排列有序的Co₃O₄纳米线。对Co₃O₄样品的表面积和孔隙结构分析表明，由于结晶产物不同，它们在中孔和大孔以及比表面积方面存在显著差异。紫外 - 可见 - 漫反射光谱（UV - Vis - DRS）研究表明，光学跃迁和带隙取决于微晶尺寸。磁性研究表明，两个样品都存在有限尺寸效应和低温铁磁性；低维度纳米线比高维度Co₃O₄纳米线具有更强的铁磁性。由于微晶尺寸更小且表面位点更易接近，常规回流法合成的Co₃O₄样品在赝电容研究中显示出更好的电荷存储、高库仑效率和增强的倍率响应。然而，微波辅助法合成的Co₃O₄样品由于其更刚性的定向纳米线结构，表现出更好的高倍率循环稳定性。此外，拉贡图（Ragone plot）显示低维度Co₃O₄纳米线具有相当高的能量和功率密度。总体而言，这项研究表明，在非水热均相沉淀条件下，对于电化学超级电容器应用，常规回流合成的低维度Co₃O₄纳米线比微波合成的高维度Co₃O₄纳米线具有更优异的表面性能。
In the context of immense control of synthesis methods on the structural and functional characteristics of the materials, nanowire morphologies of Co3O4 are synthesized in conventional reflux and microwave-assisted methods, under homogeneous precipitation conditions. The Co3O4 sample synthesized by the conventional reflux method consists of randomly distributed thin nanowires while the microwave reflux method generates higher-dimensional and arranged Co3O4 nanowires. The surface area and pore structural analysis of the Co3O4 samples show significant difference in their meso- and macroporosity as well as specific surface area, due to differently crystallized products. The UV-Vis-DRS study shows crystallite size dependent optical transitions and band gaps. The magnetic study illustrates finite size effect and low temperature ferromagnetism in both samples; the lower-dimensional nanowires being more ferromagnetic than the higher-dimensional Co3O4 nanowires. Due to smaller crystallite size and more accessible surface sites, the Co3O4 sample synthesized by the conventional reflux method shows better charge storage, high Coulombic efficiency, and enhanced rate response during the pseudocapacitance studies. However the Co3O4 sample synthesized using the microwave-assisted method shows better high rate cyclic stability due to its more rigid orientated nanowire structure. Further, the Ragone plot exhibits considerably higher energy and power densities of lower-dimensional Co3O4 nanowires. Broadly, this study reveals that, under nonhydrothermal homogeneous precipitation conditions, the conventional reflux synthesized lower-dimensional Co3O4 nanowires bear superior surface properties than the microwave synthesized higher-dimensional Co3O4 nanowires, for electrochemical supercapacitor applications.