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Morphology and Electrical Capacitance Characteristics of Nanostructured Mn x O y /MWCNT Composites
Inorganic Materials ( IF 0.8 ) Pub Date : 2021-05-17 , DOI: 10.1134/s0020168521050113
Yu. A. Zakharov , G. Yu. Simenyuk , E. V. Kachina , Yu. N. Dudnikova , V. G. Dodonov , Z. R. Ismagilov

Abstract

Reducing potassium permanganate by a carbon matrix (multiwalled carbon nanotubes (MWCNTs)) in aqueous solutions, we have obtained MnxOy/MWCNT nanostructured composites (NSCs). The morphology and texture of the MWCNTs and NSCs have been studied by X-ray diffraction, small angle X-ray scattering (SAXS), sorption porosimetry (SP), scanning electron microscopy, and transmission electron microscopy (TEM) with the aim of assessing the effect of the MnxOy filler on their properties and the electrical capacitance characteristics of composite electrodes in model supercapacitor (SC) cells. Comparison of the TEM, SAXS, and SP results indicates that the MWCNTs have narrow distributions of the channel diameter (2–5 nm), outer diameter (18–23 nm), and wall thickness (2–12 nm). In addition, nanotube entanglements (“fibers”) form meso- and macropores (20–80 nm), probably slit-shaped. The filler particles in the NSCs have the form of nanometer-thick quasi-films of Mn2O3 and MnO2 nanocrystallites and aggregates on the surface of the inner channels, accessible to the electrolyte, and on the outer surface of the MWCNTs and partially block the MWCNT channels. The aggregate size and the blocking of channels and mesopores increase with increasing NSC preparation temperature and MnxOy filler content. The electrical capacitance of the NSCs in a potential window of ±1 V exceeds the capacitance of the MWCNTs owing to the contribution of the pseudocapacitance during redox processes involving MnxOy on the surface of the NSCs. At an optimal filler content (about 5 wt % in terms of Mn), the capacitance of NSC electrodes exceeds that of MWCNT electrodes by a factor of 1.5 (at v = 10 mV/s) and 2.5 (at v = 80 mV/s).



中文翻译:

纳米结构Mn x O y / MWCNT复合材料的形貌和电容特性

摘要

通过水溶液中的碳基质(多壁碳纳米管(MWCNT))还原高锰酸钾,我们获得了Mn x O y / MWCNT纳米结构复合材料(NSC)。通过X射线衍射,小角X射线散射(SAXS),吸附孔隙率法(SP),扫描电子显微镜和透射电子显微镜(TEM)研究了MWCNT和NSC的形态和织构,旨在评估Mn x O y的影响在模型超级电容器(SC)电池中填充它们的特性和复合电极的电容特性。TEM,SAXS和SP结果的比较表明,MWCNT的通道直径(2–5 nm),外径(18–23 nm)和壁厚(2–12 nm)分布较窄。另外,纳米管缠结(“纤维”)形成中孔和大孔(20-80 nm),可能是狭缝形的。NSC中的填料颗粒具有Mn 2 O 3和MnO 2的纳米厚度准薄膜的形式纳米晶和聚集体在内部通道的表面上,可被电解质接近,并且在MWCNT的外表面上,并部分阻塞MWCNT通道。随着NSC制备温度和Mn x O y填料含量的增加,聚集体的尺寸以及对通道和中孔的阻塞增加。在±1 V的电势窗口中,NSC的电容超过了MWCNT的电容,这是由于在NSC的表面上涉及Mn x O y的氧化还原过程中,伪电容的作用所致。在最佳填料含量(以Mn计约为5 wt%)下,NSC电极的电容比MWCNT电极的电容高1.5倍(在v= 10 mV / s)和2.5(在v = 80 mV / s时)。

更新日期:2021-05-18
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