CTAB-assisted microemulsion synthesis of unique 3D network nanostructured polypyrrole presenting significantly diverse capacitance performances in different electrolytes

Abstract

In this work, the unique 3D network nanostructured polypyrrole (PPy) has been successfully synthesized in cetyltrimethylammonium bromide/butyl alcohol/hexane/water microemulsion system. The composition, crystalline characteristic and morphology of as-prepared PPy materials are characterized by Fourier transform infrared spectrometer, X-ray diffractometer and field emission scanning electron microscope. It is shown that as-prepared PPy materials possess unique 3D network nanostructure stacked by PPy nanospheres with an average diameter of 100 nm. Furthermore, the electrochemical performances of PPy based electrodes are investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectrum in 1.0 M H2SO4, 1.0 M Na2SO4 and 1.0 M KCl electrolytes, respectively. At a current density of 1.0 A g−1, as-prepared PPy based electrode exhibits the highest specific capacitance (329.0 F g−1) in 1.0 M H2SO4 electrolyte, much higher than that in 1.0 M Na2SO4 (156.6 F g−1) or 1.0 M KCl (153.2 F g−1) electrolyte. However, the specific capacitance of PPy based electrode in 1.0 M H2SO4 electrolyte retains only 40.6% of the initial specific capacitance after 5000 continuous charge/discharge cycles and, interestingly, 83.9% and 81.3% in 1.0 M Na2SO4 and 1.0 M KCl electrolytes, respectively. It is reasonable that the process of deoxidation and reoxidation of PPy nanomaterials is accompanied by the intercalation and deintercalation of massive H3O+ in 1.0 M H2SO4 electrolyte, which might result in the collapsed structure of as-prepared PPy nanomaterials and the relative instability during the cycling process.