Elsevier

Synthetic Metals

Volume 218, August 2016, Pages 56-63
Synthetic Metals

Large-scale free-template electrosynthesis of poly(2-chloromethyl-2,3-dihydrothieno[3,4-b][1,4]dioxine) nanowires and their application for supercapacitors

https://doi.org/10.1016/j.synthmet.2016.04.031Get rights and content

Highlights

  • Large-scale PEDOT-MeCl nanowires were easily electrodeposited without any templates.

  • The diameter of PEDOT-MeCl nanowires were only about 20 nm.

  • The capacitance performance of PEDOT-MeCl nanowires was firstly reported.

Abstract

Large-scale chloromethyl functionalized poly(3,4-ethylenedioxythiophene) nanowires (PEDOT-MeCl), poly(2-chloromethyl-2,3-dihydrothieno[3,4-b][1,4]dioxine), were easily electrodeposited in acetonitrile solution containing 0.1 M lithium perchlorate without any templates. The PEDOT-MeCl nanowires were characterized by FT-IR, TG, SEM, TEM and electrochemical technologies. The nanowires structural PEDOT-MeCl with diameter of about 20 nm displayed good thermal stability and high specific capacitance of 174 F g−1 at 25 mV s−1. Furthermore, the energy density of the symmetric supercapacitor built by PEDOT-MeCl nanowires reached 6.95 Wh kg−1 at a power density of 1625 W kg−1, and the specific capacitance retention was 81% after 1000 cycles. The above information implied the bright prospect of the PEDOT-MeCl nanowires as electrode material for supercapacitors.

Introduction

Supercapacitors have become one of the most promising energy storage devices because of their larger energy density than traditional capacitors and higher power density than secondary batteries [1], [2]. Moreover, they possess fast charge-discharge rates and long cycle life [3], [4]. According to the electrode materials, supercapacitors are generally classified into two categories: electrical double layer capacitors (EDLC) and pseudocapacitors. In comparison with the former, the latter shows higher energy density [5], [6]. Both transition metal oxides and conducting polymers (CPs) have been widely studied as electrode materials for pseudocapacitors. As an excellent candidate, CPs show lots of merits such as good redox reversibility, high conductivity, excellent mechanical flexibility, low cost and low toxicity [7], [8], [9].

As one of most important members of CPs, poly(3,4-ethylenedioxythiophene) (PEDOT) has been introduced into the field of supercapacitors because of its wide potential window, high electrical conductivity, fast charge/discharge ability and good environmental stability [10], [11], [12]. Additionally, due to the distinctive feature of positive (p-) and negative (n-) doping privilege, PEDOT has been regarded as the most famous electrode material in supercapacitor field [13], [14]. However, the practical specific capacitance of PEDOT is lower than its theoretical predictions, namely, the experimental value is only 70–130 F g−1 while the theoretical value is up to 210 F g−1 [15], [16], [17]. Many methods have been proposed to improve the capacitance property of PEDOT mainly based on three aspects: (1) forming composites with metal oxides [18], [19], [20] and/or carbon materials [21], [22], [23]; (2) building nanostructural morphology [24]; (3) synthesizing PEDOT derivatives by introducing various functional groups. The first method is most popular, however, the metal oxides or carbon materials are usually expensive. The second method is a good way to improve the capacitance performance of PEDOT, however, either special equipment or complex process is required in the case, which has limited its development. Relatively speaking, synthesizing new PEDOT derivative by simple molecular engineering is a fundamental way to solve the problem about the low specific capacitance of PEDOT.

On the other hand, one-dimensional nanostructures CPs including nanoparticles, nanowires and nanotubes have already been applied into supercapacitors. Currently, only a few reports on PEDOT nanowires or nanotubes are presented. These methods for preparing PEDOT with unique morphologies need to use the anodized alumina membranes as a hard template [25] or the surfactants as soft templates [26]. A convenient template-free synthetic route for preparation of large-scale PEDOT nanowires remains a challenge. As one of most important derivatives of 3,4-ethylenedioxythiophene (EDOT), 2-chloromethyl-2,3-dihydrothieno[3,4-b][1,4]dioxine (EDOT-MeCl) in dichloromethane solution can be electrochemically prepared into PEDOT-MeCl nanoparticles in our previous works [27]. According to literature, Cl substituent group or Cl ions are predicted to induce morphological modifications of organic and inorganic crystals [28], [29]. As such, we attempted to prepare PEDOT-MeCl nanowires in the present work. By simply replacing the dichloromethane with acetonitrile solvent, large-scale PEDOT-MeCl nanowires could be obtained from acetonitrile solution containing 0.1 M LiClO4 and 0.05 M EDOT-MeCl by a facile, one-step and template-free electrodeposition method. The morphology, structural information and the thermal stability of PEDOT-MeCl were investigated. Furthermore, the capacitive behaviors of PEDOT-MeCl nanowires and the symmetric supercapacitors were also examined by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge techniques.

Section snippets

Materials

EDOT-MeCl was prepared based on our previous reports [27]. Acetonitrile (ACN, AR) was obtained from Shanghai Lingfeng Chemical Reagent Co., Ltd. and used after reflux distillation. H2SO4 (98%) was used without further process. Lithium perchlorate (LiClO4, AR) was purchased from Xiya Reagent Research Center. All water used in this work was doubly distilled water.

Apparatus

The electrochemical tests were performed on a CHI 660B potentiostat/galvanostat (Shanghai Chenhua Instrumental Co., Ltd., China). Glass

Cyclic voltammograms of EDOT-MeCl

The electrochemical polymerization process of monomer and redox process of its polymer are usually determined by its consecutive cyclic voltammograms (CVs). The successive CVs of 0.05 M EDOT-MeCl in ACN solution containing 0.1 M LiClO4 at 50 mV s−1 are displayed in. Fig. 1. The oxidation of the monomer and its polymer took place in the process of the positive scan, while the reduction of the polymer appeared during the negative scan. The initial oxidation potential of EDOT-MeCl was found at 1.19 V

Conclusions

In this paper, PEDOT-MeCl nanowires were electrochemically prepared via the potentiostatic polymerization of its monomer in acetonitrile solution containing suitable lithium perchlorate. Thermogravimetric analysis result showed the good thermal stability of PEDOT-MeCl. Scanning electron microscopy and transmission electron microscopy confirmed the nanowires structure of PEDOT-MeCl with diameter of about 20 nm. Electrochemical tests indicated that PEDOT-MeCl was an excellent supercapacitor

Acknowledgements

This work was supported by the National Natural Science Foundation of China (grant number: 51572117, 51463008), Ganpo Outstanding Talents 555 projects (2013), the Natural Science Foundation of Jiangxi Province (grant number: 20142BAB206028 and 20142BAB216029), the Doctoral Starting up Foundation of Jiangxi Science and Technology Normal University, and the foundation of entrepreneurship and scientific research for undergraduates of Jiangxi Science and Technology Normal University (201511318008)

References (49)

  • K. Lota et al.

    Capacitance properties of poly(3,4-ethylenedioxythiophene)/carbon nanotubes composites

    J. Phys. Chem. Solids

    (2004)
  • Y. Xie et al.

    Porous poly(3,4-ethylenedioxythiophene) nanoarray used for flexible supercapacitor

    Micropor. Mesopor. Mat.

    (2015)
  • X. Ma et al.

    Effect of substituent position on electrodeposition morphology, and capacitance performance of polyindole bearing a carboxylic group

    Electrochim. Acta

    (2015)
  • X. Ma et al.

    Electrochemical preparation of poly(2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl) methanol)/carbon fiber core/shell structure composite and its high capacitance performance

    J.Electroanal. Chem.

    (2015)
  • W. Zhou et al.

    Electrochemical fabrication of a porous network MnO2/poly (5-cyanoindole) composite and its capacitance performance

    Electrochim. Acta

    (2014)
  • J. Roncali et al.

    Poly mono-, bi-and trithiophene: effect of oligomer chain length on the polymer properties

    Synth. Met.

    (1986)
  • Y. Wen et al.

    Electrochemical polymerization of 3,4-ethylenedioxythiophene in aqueous micellar solution containing biocompatible amino acid-based surfactant

    J. Electroanal. Chem.

    (2009)
  • S. Zhang et al.

    Electrochemical polymerization of 3,4-ethylenedioxythiophene in aqueous solution containing N-dodecyl-β-d-maltoside

    Eur. Polym. J

    (2006)
  • C. Du et al.

    Supercapacitors using carbon nanotubes films by electrophoretic deposition

    J. Power Sources

    (2006)
  • Z. Yu et al.

    Highly ordered MnO2 nanopillars for enhanced supercapacitor performance

    Adv. Mater.

    (2013)
  • Z. Yu et al.

    Flexible, sandwich-like Ag-nanowire/PEDOT: PSS-nanopillar/MnO2 high performance supercapacitors

    J. Mater. Chem. A

    (2014)
  • W. Wei et al.

    Partial ion-exchange of nickel-sulfide-derived electrodes for high performance supercapacitors

    Chem. Mater.

    (2014)
  • Y. Li et al.

    Ni-Co sulfide nanowires on nickel foam with ultrahigh capacitance for asymmetric supercapacitors

    J. Mater. Chem. A

    (2014)
  • Z. Zhang et al.

    One-step hydrothermal synthesis of 3D petal-like Co9S8/RGO/Ni3S2 composite on nickel foam for high-performance supercapacitors

    ACS Appl. Mater. Inter.

    (2015)
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