3D sponge nitrogen doped graphene (NG) was prepared economically from waste polyethylene-terephthalate (PET) bottles mixed with urea at different temperatures using green approach via a novel one-step method. The effect of temperature and the amount of urea on the formation of NG was investigated. Cyclic voltammetry and impedance spectroscopy measurements, revealed that nitrogen fixation, which affects the structure and morphology of prepared materials improve the charge propagation and ion diffusion. The prepared materials show outstanding performance as a supercapacitor electrode material, with the specific capacitance going up to 405 F g−1 at 1 A g−1. An energy density of 68.1 W h kg−1 and a high maximum power density of 558.5 W kg−1 in 6 M KOH electrolytes were recorded for the optimum sample. The NG samples showed an appropriate cyclic stability with capacitance retention of 87.7% after 5000 cycles at 4 A g−1 with high charge/discharge duration. Thus, the prepared NG herein is considered to be promising, cheap material used in energy storage applications and the method used is cost-effective and environmentally friendly method for mass production of NG in addition to opening up opportunities to process waste materials for a wide range of applications.
An electrochemical deposition technique was used to fabricate polypyrrole (Ppy)/NiO nanocomposite electrodes for supercapacitors. The nanocomposite electrodes were characterized and investigated by Fourier transform infrared spectroscopy (FTIR), X-ray Diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS). The performance of supercapacitor electrodes of Ppy/NiO nanocomposite was enhanced compared with pristine Ppy electrode. It was found that the Ppy/NiO electrode electrodeposited at 4 A/cm−2 demonstrated the highest specific capacitance of 679 Fg−1 at 1 Ag−1 with an energy density of 94.4 Wh kg−1 and power density of 500.74 W kg−1. Capacitance retention of 83.9% of its initial capacitance after 1000 cycles at 1 Ag−1 was obtained. The high electrochemical performance of Ppy/NiO was due to the synergistic effect of NiO and Ppy, where a rich pores network-like structure made the electrolyte ions more easily accessible for Faradic reactions. This work provided a simple approach for preparing organic–inorganic composite materials as high-performance electrode materials for electrochemical supercapacitors.
Novel electrospun membranes quasi-solid electrolytes based on blends of polymethylacrylate (PMA) -polyvinylidene fluoride (PVDF), and PMA-PVDF/PEG (polyethylene glycol) are prepared by electrospinning technique and applied as quasi-solid state electrolytes in dye sensitized solar cells (DSSCs). The membranes are characterized by Fourier transform infrared (FT-IR) spectrophotometer, differential scanning calorimeter (DSC), Scanning electron microscopy (SEM), and Electrochemical impedance spectroscopy. The crystallinity obtained from the DSC data increased with the increase of PVDF wt% in PMA-PVDF blend and then decreased for the PMA-PVDF/PEG membranes. The fully interconnected porous structure of the host polymer membranes of PMA-PVDF (4:6 wt%) exhibited a high electrolyte uptake reached to ~ 265% and an ionic conductivity of 2.1×10 −3 S cm −1 , which is increased to 406.3%, and 3.2 × 10 -3 S cm −1 , respectively for PMA-PVDF/PEG (4:6:4 wt%) membrane. DSSC is assembled by PMA-PVDF(4:6 wt%) and attained an overall energy conversion efficiency of 6.6% at light intensity of 100 mW cm -2 . The presence of 4 w% PEG in the electrolyte membrane increased the energy conversion efficiency to 7 % giving a promise candidate for scaling up this type of DSSCs.
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