Configuration and capacitance properties of polypyrrole/aligned carbon nanotubes synthesized by electropolymerization

Science Bulletin, Dec 2011

Aligned carbon nanotubes (ACNTs) were modified with polypyrrole (PPy) via electropolymerization. Because of the large specific surface area and excellent electrical conductivity of ACNTs, continuous electropolymerization was able to be carried out, forming a thick PPy coating on the ACNTs. The resulting nanocomposite possessed a core-shell structure with ACNTs as the core, PPy as the shell, and nanoparticles of PPy on the top, and displayed high performance supercapacitance properties.

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Configuration and capacitance properties of polypyrrole/aligned carbon nanotubes synthesized by electropolymerization

XU Ying 0 ZHUANG ShuQi 0 ZHANG XiaoYan 0 HE PinGang 0 FANG YuZhi 0 0 Department of Chemistry, East China Normal University , Shanghai 200062, China Aligned carbon nanotubes (ACNTs) were modified with polypyrrole (PPy) via electropolymerization. Because of the large specific surface area and excellent electrical conductivity of ACNTs, continuous electropolymerization was able to be carried out, forming a thick PPy coating on the ACNTs. The resulting nanocomposite possessed a core-shell structure with ACNTs as the core, PPy as the shell, and nanoparticles of PPy on the top, and displayed high performance supercapacitance properties. - Carbon nanotubes (CNTs) were discovered in 1991, and possess many outstanding physical and chemical properties. Since then, this interesting nanomaterial has been developed substantially for science and technology applications. Generally, CNTs are prepared as a randomly oriented structure with each nanotube wrapped with others. Recently, scientists have designed and prepared them with specific structures, such as aligned CNTs (ACNTs) [1], which have been employed as a novel electrode nanomaterial to fabricate bio/chemical sensors [24], and electron field emitters [5]. ACNTs are also promising supercapacitor materials because their 3D structure offers a large specific surface area, superior electronic transfer ability through individual nanotubes, and chemical inertness [69]. However, because ACNTs are generally directly prepared on substrates without special protection, the nanotubes are easily cracked. In additional, they are intrinsically hydrophobic with a low affinity for aqueous solution. The friability and hydrophobic nature of ACNTs limits their use as supercapacitors. To improve the physicochemical and mechanical properties of ACNTs, and further increase their capacitance, herein, we have modified the nanotubes by electropolymerization with the conducting polymer polypyrrole (PPy). Conducting polymers such as polyaniline [10], polymethyl methacrylate [11], polythiophene [12] and PPy [1315] have been combined with traditional CNTs, and such nanocomposite materials display favorable electronic and mechanical properties including enhanced capacitance [16,17]. PPy possesses advantages such as easy synthesis, high electrical conductivity, thermal and chemical stability, environmental friendliness, low preparation cost and electropolymerization potential, in addition to the potential to store energy [18]. However, PPy deposited on common substrates forms an uncontrolled dense film with high resistance to ionic and electronic transfer. The highest reported electronic conductivity of a PPy film is several hundred S/cm [19], which limits its use as an electrode material, supercapacitor, and functional component in microelectromechanical systems. One method to resolve this problem is to use a special matrix with a high surface area and nanoporosity for polymerization of PPy, resulting in a large amount of porous PPy loaded on the matrix surface. CNTs are a good example of such a matrix, and possess the added advantage of increasing the electronic conductivity of PPy. To date, both entangled single- and multi-walled CNTs (i.e., SWCNTs and MWCNTs) have been employed as matrices The Author(s) 2011. This article is published with open access at Springerlink.com for electropolymerization of PPy, improving the specific surface area, electric conductivity and mechanical properties of PPy [2024]. However, there are few reports on the combination of conducting polymers with ACNTs. Dai and coworkers [25] first reported the electropolymerization of conducting polymers including polyaniline and PPy onto ACNTs for potential application in optoelectronic nanodevices and sensors. The conducting polymers uniformly modified the aligned nanotubes during the electropolymerization process. Windle and coworkers [26] found that electropolymerizing PPy onto ACNTs increased the specific capacitance (SC) by about 4 times compared with a pure PPy film. Wallace et al. [27] fabricated a glucose sensor using a PPy-coated ACNT electrode. Herein, PPy-ACNT nanocomposites are formed using an electrochemical method. The properties of the nanocomposites are fully investigated, especially the capacitive behavior. Because the ACNTs possess much lower resistance to electron transfer than those with structural defects, individual carbon nanotubes have a high conductivity up to 5000 S/cm, while entangled ones have a conductivity in the order of 200300 S/cm [2830]. In addition, the 3D ACNTs possess a much larger surface area than traditional CNTs. Therefore, it was expected that ACNTs would act as a suitable matrix for polymerization of PPy, and the resulting PPy-ACNT nanocomposites would overcome the individual shortcomings of ACNTs and PPy, facilitating their application as supercapacitor materials. ACNTs were prepared on quartz glass substrate by chemical vapor deposition using iron(II) phthalocyanine as the raw (...truncated)


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Ying Xu, ShuQi Zhuang, XiaoYan Zhang, PinGang He, YuZhi Fang. Configuration and capacitance properties of polypyrrole/aligned carbon nanotubes synthesized by electropolymerization, Science Bulletin, 2011, pp. 3823-3828, Volume 56, Issue 35, DOI: 10.1007/s11434-011-4745-z