Microstructure and electrochemical properties of the Co–BN composites
Microstructure and electrochemical properties of the Co–BN composites
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DOI：
10.1016/j.electacta.2007.10.006
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发表时间：
2008
影响因子：
6.6
通讯作者：
Z. Lu;S. Yao;G. R. Li;T. Y. Yan;X. P. Gao
中科院分区：
文献类型：
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作者：
Z. Lu;S. Yao;G. R. Li;T. Y. Yan;X. P. Gao
通过球磨不同Co/BN质量比的金属Co和氮化硼（BN）粉末制备了Co-BN复合材料。利用X射线衍射（XRD）、透射电子显微镜（TEM）和X射线光电子能谱（XPS）对Co-BN复合材料的微观结构、形貌和化学状态进行了表征。球磨后，在非晶BN基体上分布着尺寸为10- 30 nm的Co纳米颗粒。电化学测试结果表明，Co/BN质量比为5/1的Co-BN复合材料在6 M KOH溶液中具有良好的循环性能和较高的可逆电化学容量。此外，Co-BN复合物可以直接放电而无需第一充电过程。在预充电样品的第一个循环中观察到的较高的初始放电容量可以通过Co-BN复合材料表面上的氧化物质的初始还原和随后的氧化来解释。Co（OH）2在碱性溶液中的部分溶解将进一步增加材料的活性表面积，因为第一次循环后的过电位显著降低。基于结构分析和电化学测试，在Co-BN复合材料中，高度分散的活性Co纳米颗粒的可逆法拉第反应占主导地位。
The Co–BN composites are synthesized by ball-milling metallic Co and boron nitride (BN) powder with a different Co/BN weight ratio. The microstructure, morphology and chemical state of the obtained Co–BN composites are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). After ball milling, Co nanoparticles of 10–30nm in size are distributed on the amorphous BN matrix. The electrochemical measurements, including galvanostatic method and cyclic voltammetry (CV), show that the Co–BN composite with the Co/BN weight ratio of 5/1 has a good cycle performance and a high reversible electrochemical capacity in 6M KOH solution. Moreover, the Co–BN composite can be discharged directly without the first charging process. The higher initial discharge capacity, observed in the first cycle of the pre-charged sample, can be explained by an initial reduction of the oxidized species on the surface of the Co–BN composite and subsequent oxidation. The partial dissolution of Co(OH)2in alkaline solution would further increase the active surface area of the material for the considerable decrease in overpotential after the first cycle. Based on a structure analysis and electrochemical measurement, the reversible faradic reaction of the highly dispersed active Co nanoparticles in the Co–BN composite is dominant.