Supercapacitive studies on amorphous MnO2 in mild solutions
Supercapacitive studies on amorphous MnO2 in mild solutions
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DOI：
10.1016/j.jpowsour.2008.04.005
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发表时间：
2008-10
影响因子：
9.2
通讯作者：
Chengjun Xu;Baohua Li;Hongda Du;F. Kang;Yuqun Zeng
中科院分区：
文献类型：
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作者：
Chengjun Xu;Baohua Li;Hongda Du;F. Kang;Yuqun Zeng
采用自反应微乳液法合成二氧化锰。X-射线衍射结果表明，其无定形性质，没有明显的峰，峰变宽。在0.5molL−_1Na_2SO_4水溶液中测量了典型的循环伏安曲线，在2 mvs−_1的扫描速度下，电极的电位范围控制在−_(0.5)~0.5，−_(0.65)~0.65，Hg/Hg_2SO_4的−_(0.75)~0.75V之间。在−_(0.5)~0.5V之间观察到矩形对称的图像，表明在该电位和扫描速度下具有很高的电化学可逆性。本文还讨论了阳离子种类和浓度(活性)对MnO2电化学性能的影响。在Li2SO4、Na2SO4和K2SO4水溶液中进行了−0.5~0.5V的循环伏安实验，结果表明，在0.0 5~1molL−1范围内，MnO2的比容与阳离子浓度和种类有很强的依赖关系，比电容值随阳离子浓度的增加而增大。MnO_2的电容与阳离子活性的对数关系表明，MnO_2的电荷存储通过阳离子插入参与了快速氧化还原反应。
Manganese dioxide has been synthesized by a self-reacting microemulsion method. The result of X-ray diffraction shows that lack of clear peaks and broadening of peaks indicate its amorphous nature. Typical cyclic voltammograms were measured in 0.5molL−1Na2SO4aqueous solution and the potential ranges were controlled from −0.5 to 0.5, from −0.65 to 0.65, and from −0.75 to 0.75V versus Hg/Hg2SO4at a sweep rate of 2mVs−1. Rectangular and symmetric image was observed between −0.5 and 0.5V indicating high electrochemical reversibility in this potential and sweep rate. The influence of cation species and concentration (activity) on electrochemical performances of MnO2is also discussed in this work. Cyclic voltammetric experiments have been performed between −0.5 and 0.5V versus Hg/Hg2SO4in Li2SO4, Na2SO4and K2SO4aqueous solutions with different salt concentrations ranging from 0.05 to 1molL−1. The specific capacitance of MnO2was found to depend strongly on the cation concentration and species, and specific capacitance value will increase with the increase of cation concentration for all electrolytes. The logarithmic dependence of capacitance of MnO2on cation activity indicates that the charge storage for MnO2is involved in a fast redox reaction through cation insertion.