Xiumei Ma

High-performance capacitive behavior of layered reduced graphene oxide and polyindole nanocomposite materials

In this work, a high-capacitance hybrid nanocomposite based on reduced graphene oxide (RGO) and polyindole (PIn) was fabricated via an in situ chemical oxidative polymerization approach. The structure and morphology of PIn/RGO were investigated by FT-IR, Raman spectroscopy, SEM and TEM. The electrochemical properties of this electrode in aqueous H2SO4 electrolyte were also investigated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy (EIS). Compared to RGO and PIn electrodes, the PIn/RGO hybrid nanocomposite shows a large improved specific capacitance of 322.8 F g−1 at 1.0 A g−1, good stability with a cycling efficiency of 94.5% after 1000 cycles, and high energy density of 36 W h kg−1 at a high power density of 5000 W kg−1. The enhanced performance is proposed to arise from the synergetic effect between PIn and RGO. In addition, the symmetric PIn/RGO//PIn/RGO supercapacitor showed specific capacitance of 99.8 F g−1 and only 3.7% decay after 1000 cycles. These results imply that PIn/RGO should be a promising electrode material for supercapacitor applications.

Electrosynthesis and electrochemical capacitive behavior of a new nitrogen PEDOT analogue-based polymer electrode

In this work, poly(N-methyl-3,4-dihydrothieno[3,4-b][1,4]oxazine) (PMDTO), a new nitrogen poly(3,4-ethylendioxythiophene) (PEDOT) analogue, was synthesized by an electrochemical deposition method, and the capacitive properties of PMDTO were investigated and compared with those of PEDOT. The structure and morphology of PMDTO were characterized by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and thermal analysis. The pseudocapacitive properties of the as-prepared PMDTO electrodes have been examined by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) measurements and electrochemical impedance spectroscopy (EIS) in 0.1 mol L−1 CH3CN–Bu4NBF4 electrolyte solution. The as-prepared PMDTO electrode showed a high specific capacitance of 154.3 F g−1 at a discharge current density of 3 A g−1 and exhibited cycling stability with the maximal capacitance retention of nearly 71% after 500 cycles at a high current density of 10 A g−1. Additionally, the asymmetrical supercapacitor based on PMDTO and PEDOT electrodes exhibited a maximum specific capacitance of 63.5 F g−1 and an energy density of 12.7 W h kg−1 at a power density of 0.59 kW kg−1. These results implied that the PMDTO electrode can be used as a potential electrode material for supercapacitors.

One-step template-free electrodeposition of novel poly(indole-7-carboxylic acid) nanowires and their high capacitance properties

Poly(indole-7-carboxylic acid) (PICA) nanowires with conductivity of 5 × 10−2 S cm−1 were prepared by a facile, one-step and template-free electrodeposition method. The hydrogen bond interactions between the N–H group and the carboxyl group facilitated the formation of PICA nanowires. The diameter of the PICA nanowires was about 40 nm confirmed by scanning electron microscopy. Fourier transformation infrared spectroscopy and 1H NMR spectroscopy confirmed that the polymerization occurred at the C2 and C3 position on the indole ring. The electrochemical capacitance properties of the PICA nanowires were investigated with cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscope techniques. A remarkable specific capacitance of 373.2 F g−1 was obtained at a current density of 2.5 A g−1 in 1.0 M H2SO4 solution. PICA nanowires presented an excellent cycle life with 91% specific capacitance retention after 1000 charge–discharge processes. The energy density of the symmetric full cell based on two PICA electrodes was 7.03 W h kg−1 at a power density of 4500 W kg−1. These results implied that the PICA nanowires will be a promising electrode material for supercapacitors.