Electrochemical Co-deposition Of Polyaniline And Tungsten Oxide For Supercapacitor

Polyaniline(PANI)is a highly promising electrode material for supercapacitor.However,usually PANI experiences large volumetric swelling and shrinking during charge-discharge process.This leads to fast capacitance decay,which limits its application.Incorporation of inorganic oxides in the polymer is an effective way to address this issue.Tungsten oxide(WO3)can exist in a variety of valence and so has rich electrochemical activities.Incoporation of WO3 in PANI is helpful to suppress its capacitance decay and widen the potential window for charge storage as well,leading to energy density increase.Herein,concurrent electropolymerization of aniline and electrochemical deposition of WO3 were conducted by cyclic voltammetry(CV)on a current collector of partial exfoliated graphite foil(Ex-GF)to afford PANI-WO3/Ex-GF electrode.Influences of the ratio of aniline to WO3 precursor,as well as the H2O2 concentration in the electrochemical deposition solution,on pseudocapacitive properties of the obtained composite were investigated.Their morphologies were characterized by scanning electron microscope(SEM),while the structure and composition were characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR)and X-ray photoelectron spectroscopy(XPS).Their electrochemical performances were investigated by CV,galvanostatic charge-discharge and electrochemical impedance spectroscopy(EIS).It was found that the composite of PW-2:1-4/Ex-GF,made from the solution with an aniline to WO3 precursor ratio of 2:1 and containing 0.04 M H2O2,displayed a high composite based specific capacitance of 408 F/g at a discharging current density of 1 A/g in a w:ide charge storage potential window of-0.6～0.7 V vs.SCE.Its energy density was as high as 95.8 Wh/kg at 650 W/kg,which is superior to other PANI-based pseudocapacitive materials.PW-2:1-4/Ex-GF also showed much improved cyclic stability(91.6%capacitance retention)compared to similarly prepared PANI/Ex-GF(69.1%capacitance retention)at a discharging current density of 10 A/g after 5000 galvanostatic charge-discharge cycles.A symmetric supercapacitor PW-2:1-4/Ex-GF//PW-2:1-4/Ex-GF(SSC)with an operating voltage of 1.3 V was assembled by using PW-2:1-4/Ex-GF as both of the positive and negative electrodes.The SSC showed a specific capacitance of 102 F/g at a current density of 1 A/g.The SSC can retain 87.5%of its capacitance after 10000 galvanostatic charge-discharge cycles,exhibiting its excellent cycling stability.