Over the past decades,with the excessive consumption of fossil energy and the increasingly severe environment pollution problem,exploring green,high-efficiency and sustainable energy sources,as well as advanced energy conversion and storage technologies is an urgent task needed to be solved.Supercapacitor(or electrochemical capacitor),which is a sort of typical energy storage devices with excellent power density and remarkable cycle stability,has attracted a great deal of interest in many advanced power systems.The conducting polymer has been widely investigated for a potential pseudocapacitor electrode material.However,an inevitable problem for conducting polymer is that they undergoes continuous swelling/shrinkage because of insertion/de-insertion of ions at the backbone of conducting polymer,leading to a significant structural breakdown and rapid capacitance decay during repeated charge/discharge cycles.A credible approach to circumvent these problems is integrating highly pseudocapacitive conducting polymer with the carbon materials.Treated with pyrolysis and KOH activation,the willow catkin is successfully converted into cross-linked carbon nanosheets(CCNs),and then the PPy/CCNs and PANI/CCNs composites are obtained through in situ chemical polymerization method.We study physical properties of composites,such as morphology,molecular structure and material composition by using a series of characterization including scanning electron microscope,X-ray diffraction and Fourier transform infrared spectroscopy.And the supercapacitor performance of composites is analyzed via cyclic voltammetry,chronopotentiometry and electrochemical impedance spectroscopy.The electrochemical tests indicate that the specific capacitance of PPy/CCNs is 313.75 F g-1with a current density of 0.1 A g-1.The capacitance retention of PPy/CCNs is 75.34%with current density enlarging from 0.1 A g-1 to 5 A g-1.The capacitance only decrease 14.32%after2000 cycles in 1 mol L-1 KCl solution.The specific capacitance of PANI/CCNs is 442.46 F g-1 at a current density of 0.1 A g-1.We construct a symmetric supercapacitor by employing two same PANI/CCNs composite as the positive electrode and negative electrode in 1 mol L-1 H2SO4 solution.The supercapacitor possesses an energy density,28.91 Wh kg-1 at power density around 85.12 W kg-1 and shows excellent stability up to 10000 cycles.On this basis,we prepare the MnO2/PANI/CCNs via a facile redox reaction.Electrochemical measurements such as cyclic voltammetry,galvanostatic charge-discharge,electrochemical impedance spectroscopy are carried out in 1 mol L-1 Na2SO4 aqueous electrolytic solution.The results show the excellent maximum specific capacitive behavior of434.79 F g-1 at a current density of 0.1 A g-1.This composite exhibits a good cyclic stability with a small loss of 11.64%of maximum capacitance and a coulombic efficiency around100%over a consecutive 2000 cycles.The investigation indicates that the prepared electrode material could be a potential and promising candidate for electrochemical supercapacitors. |