Electrochemical Integration Of Molybdenum Oxide With Polypyrrole And Their Composites For Capacitive Applications

Polypyrrole(PPy)is a typical conducting polymer and a highly promising electrode material for supercapacitor.However,PPy is easy to aggregate and so difficult to get good contact with electrolyte for energy storage.It also suffers from large volumetric shrinking and swelling during charge-discharge process,leading to fast capacitance decay which limits its application in supercapacitor.Combination with metal oxides is an effective way to address this issue.MoOx has variety of valence states and excellent electrochemical activity in a wide potential range.Energy storage properties of PPy can be improved through suppressing the aggregation of PPy by combination with MoOx.Herein,concurrent electrochemical deposition of MoOx and electrochemical polymerization of pyrrole was conducted by cyclic voltammetry(CV)on partially exfoliated graphene(EGF)substrate to afford MoOx/PPy composite electrodes.The MoOx/PPy film displayed a cauliflower structure with many interspaces among the particles,which can facilitate the contact of electrolyte with electrode material and so result in improved energy storage behaviors.Influences of the higher and lower potential limits of the CV scans,scan times and the concentration of ammonium molybdate((NH4)6Mo7O24)on the prepared MoOx/PPy composite electrodes were investigated.Morphologies and compositions of MoOx/PPy composite electrode were studied by Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD),scanning electron microscopy(SEM)and energy dispersive X-ray spectroscopy(EDX).Electrochemical properties of MoOx/PPy composite electrode were studied by CV and galvanostatic charge-discharge(CP)experiments.It was found that the composite of MPy/50/0.02/-0.7/0.8,made through 50 times CV scans from-0.7 to 0.8 V vs.SCE in the solution containing 0.020 M ammonium molybdate,displayed a high specific capacitance of 3517.9 mF/cm2 at 2 mA/cm2.When the discharge current density increased 50 times to 100 mA/cm2.it still displayed a quite high capacitance of 1938.5 mF/cm2.MPy/50/0.02/-0.7/0.8 can retain 70.8%of its capacitance after 3500 galvanostatic charge-discharge cycles at 60 mA/cm2,showing its good cyclic stability...