Molecular engineering of aromatic amine spacers for high-performance graphene-based supercapacitors
Molecular engineering of aromatic amine spacers for high-performance graphene-based supercapacitors
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DOI：
10.1016/j.nanoen.2016.01.028
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发表时间：
2016-03-01
期刊：
影响因子：
17.6
通讯作者：
Wong, Ching-Ping
中科院分区：
文献类型：
--
作者：
Li, Liyi;Song, Bo;Wong, Ching-Ping
本文采用一步水热法合成了氧化石墨烯（GO）和胺分子作为间隔基的化合物。反应产物（称为rGO-Spacers样品）被制成超级电容器的电极。通过设计间隔物的分子结构，rGO-间隔物的比电容（C-s）在循环伏安法（CV）测量中在2 mV/s下可以达到612 F/g，在0.5A/g下可以达到597 F/g，在10A/g下可以达到512 F/g。经过10000次充放电循环后，仍有97%的高C_s值保持。相比之下，没有间隔物的对照样品在相同条件下在CV测量中测量的C-s为194 F/g。通过X射线衍射证实了由添加胺间隔物引起的石墨烯片之间的层间距离增加至1.9 nm。通过扫描电子显微镜、透射电子显微镜和原子力显微镜对rGO-间隔物样品的形态进行表征，其中观察到褶皱的薄片。通过能量色散谱图，发现间隔分子均匀地分散在片材上。通过热重分析、X射线光电子能谱（XPS）、紫外-可见光谱、傅里叶变换红外光谱和拉曼光谱证实了GO与间隔基之间的化学反应和共价键合。基于表征结果，提出了胺间隔基与GO之间的酰胺形成反应和环氧开环反应。XPS的重量测量和原子比信息进一步揭示了间隔基对GO的不同反应性，这可以解释具有不同分子结构的间隔基的样品的不同C-s。根据这些比较研究的结果，发现分子结构的工程化在确定C-s值方面起着关键作用。这些发现还为通过优化间隔子的分子结构以及可以促进间隔子和GO之间的反应的其他实验参数来实现甚至更高的C-s提供了指导。(C)2016爱思唯尔有限公司版权所有。
In this work, chemical compounds of graphene oxide (GO) and amine molecules as spacers were synthesized by one-step hydrothermal reactions. The products of the reactions, referred to as rGO-Spacers samples, were fabricated into electrodes for supercapacitors. By engineering the molecular structures of the spacers, the specific capacitance (C-s) of the rGO-Spacers can reach up to 612 F/g at 2 mV/s in cyclic voltammetry (CV) measurement, 597 F/g at 0.5 A/g and 512 F/g at 10 A/g in galvanostatic charge-discharge measurement using two-electrode setup with 1 M sulfuric acid aqueous solution at the electrolyte. 97% of the high C-s was retained after 10 000 charge-discharge cycles. In comparison, the control sample without spacers presents a C-s of 194 F/g measured in CV measurement under the same conditions. The increased interlayer distance up to 1.9 nm between graphene sheets caused by addition of the amine spacers was confirmed by X-ray diffraction. The morphology of rGO-Spacers samples was characterized by scanning electron microscope, transmission electron microscope and atomic force microscope, where crumpled thin sheets were observed. The spacer molecules were found to disperse uniformly on the sheets by energy dispersive spectroscope mapping. Chemical reactions and covalent bonding between GO and the spacers are evidenced by thermogravimetric analysis, Xray photoelectron spectroscopy (XPS), UV-visible spectroscopy, Fourier-transform infrared spectroscope and Raman spectroscopy.. Based on the characterization results, the amide formation reactions and epoxide ring opening reactions between amine spacers and GO are proposed. The weight measurement and the atomic ratio information from XPS further reveal different reactivity of the spacers to GO, which could account for the different C-s of the samples with spacers of different molecular structures. From the results of these comparative studies, the engineering of the molecular structures was found to play a pivotal role in determining the value of C-s. The findings also provide guidance to achieve even higher C-s by optimization of the molecular structures of the spacers, as well as other experimental parameters which can facilitate the reaction between the spacers and GO. (C) 2016 Elsevier Ltd. All rights reserved.