MnO₂@Pedot Nanowires And Nanotubes: Their Preparation And Electrochemical Properties

A new hybrid core-shell structured MnO₂@PEDOT composite had been successfully fabricated with MnO₂ nanowires as the inner core and poly?3,4-ethylenedioxythiophene? ?PEDOT? as the coating layer. The preparing processes included:Firstly, a-MnO₂ nanowires with length of 2-3 ?m and diameter of 50-80 nm was prepared by hydrothermal process. Secondly MnO₂ nanowires was treated with surface modification using KH570 to introduce C=C. Thirdly, the poly?sodium styrene sulfonate? ?PSSNa? chains were grafted onto MnO₂ nanowires coupled with silane by using 1,1-diphenylethylene ?DPE? capped PSSNa macroinitiator. The FTIR, stability of aqueous dispersion and TG analysis indicated the grafted products ?MnO₂-g-PSSNa? had been successfully synthesized. Lastly, with MnO₂-g-PSSNa as template, MnO₂/PEDOT composite ?MnO₂@PEDOT? was prepared via in-situ chemical oxidative polymerization.The SEM and TEM images showed that the PEDOT layer was evenly coated onto the surface of MnO₂ nanowires. The mass ratio of MnO₂-g-PSSNa:EDOT determined the morphology of MnO₂@PEDOT.When the mass ratio was 2:1, the product was coxial nanowire. When the mass ratio was 1:1, the hollow structure nanotubes could be produced and PEDOT aggregate accumulated with mEDOT increased. Cyclic voltammetry, charge-discharge test and EIS analysis showed that the composite possesses better capacitor properties than pure MnO₂. The specific capacitance first increased but then decreased with the increase of mEDOT.The highest specific capacitance of MnO₂@PEDOT ?62.9 F/g, mass ratio MnO₂-g-PSSNa:EDOT=1:1? was higher than pure MnO₂ ?18.5 F/g? and retained about 61.2% after 500 cycles of galvanostatic charging-discharging processes, indicating good cycle stability. The Nyquist plot indicated that MnO₂@PEDOT possessed lower charge transfer resistance ?Rct? than pure MnO₂, which proved the improvement of composite conductivity with combination of PEDOT. Furthermore, the composite possessed better capacitor performance under low potential ?<0.6 V?.