College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, PR China.
Department of Chemistry, University of Connecticut, Storrs, 55 North Eagleville Road, Storrs, CT 06269, USA.
J Colloid Interface Sci. 2016 Nov 15;482:183-192. doi: 10.1016/j.jcis.2016.07.077. Epub 2016 Jul 29.
Manganese oxides are environmentally benign supercapacitor electrode materials and, in particular, birnessite-type structure shows very promising electrochemical performance. In this work, nanostructured birnessite was facilely prepared by adding dropwise NH2OH·HCl to KMnO4 solution under ambient temperature and pressure. In order to fully exploit the potential of birnessite-type manganese oxide electrode materials, the effects of specific surface area, pore size, content of K(+), and manganese average oxidation state (Mn AOS) on their electrochemical performance were studied. The results showed that with the increase of NH2OH·HCl, the Mn AOS decreased and the corresponding pore sizes and specific surface area of birnessite increased. The synthesized nanostructured birnessite showed the highest specific capacitance of 245Fg(-1) at a current density of 0.1Ag(-1) within a potential range of 0-0.9V, and excellent cycle stability with a capacitance retention rate of 92% after 3000 cycles at a current density of 1.0Ag(-1). The present work implies that specific capacitance is mainly affected by specific surface area and pore volume, and provides a new method for the facile preparation of birnessite-type manganese oxide with excellent capacitive performance.
二氧化锰是环境友好型超级电容器电极材料，特别是纤锌矿型结构表现出非常有前景的电化学性能。在这项工作中，通过在环境温度和压力下将 NH2OH·HCl 逐滴加入 KMnO4 溶液中，简便地制备了纳米结构的纤锌矿。为了充分利用纤锌矿型氧化锰电极材料的潜力，研究了比表面积、孔径、K(+)含量和锰平均氧化态（Mn AOS）对其电化学性能的影响。结果表明，随着 NH2OH·HCl 的增加，Mn AOS 降低，相应的纤锌矿的孔径和比表面积增大。合成的纳米结构纤锌矿在 0-0.9V 的电位范围内，电流密度为 0.1Ag(-1)时具有最高的比电容 245Fg(-1)，在 1.0Ag(-1)的电流密度下循环 3000 次后，电容保持率为 92%，具有优异的循环稳定性。本工作表明比电容主要受比表面积和孔体积的影响，为制备具有优异电容性能的纤锌矿型氧化锰提供了一种新的简便方法。
